diff options
Diffstat (limited to 'kernel/sched/core.c')
| -rw-r--r-- | kernel/sched/core.c | 9865 |
1 files changed, 6817 insertions, 3048 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index a674c7db2f29..41ba0be16911 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1,30 +1,157 @@ +// SPDX-License-Identifier: GPL-2.0-only /* * kernel/sched/core.c * - * Core kernel scheduler code and related syscalls + * Core kernel CPU scheduler code * * Copyright (C) 1991-2002 Linus Torvalds + * Copyright (C) 1998-2024 Ingo Molnar, Red Hat */ -#include "sched.h" - +#define INSTANTIATE_EXPORTED_MIGRATE_DISABLE +#include <linux/sched.h> +#include <linux/highmem.h> +#include <linux/hrtimer_api.h> +#include <linux/ktime_api.h> +#include <linux/sched/signal.h> +#include <linux/syscalls_api.h> +#include <linux/debug_locks.h> +#include <linux/prefetch.h> +#include <linux/capability.h> +#include <linux/pgtable_api.h> +#include <linux/wait_bit.h> +#include <linux/jiffies.h> +#include <linux/spinlock_api.h> +#include <linux/cpumask_api.h> +#include <linux/lockdep_api.h> +#include <linux/hardirq.h> +#include <linux/softirq.h> +#include <linux/refcount_api.h> +#include <linux/topology.h> +#include <linux/sched/clock.h> +#include <linux/sched/cond_resched.h> +#include <linux/sched/cputime.h> +#include <linux/sched/debug.h> +#include <linux/sched/hotplug.h> +#include <linux/sched/init.h> +#include <linux/sched/isolation.h> +#include <linux/sched/loadavg.h> +#include <linux/sched/mm.h> +#include <linux/sched/nohz.h> +#include <linux/sched/rseq_api.h> +#include <linux/sched/rt.h> + +#include <linux/blkdev.h> +#include <linux/context_tracking.h> +#include <linux/cpuset.h> +#include <linux/delayacct.h> +#include <linux/init_task.h> +#include <linux/interrupt.h> +#include <linux/ioprio.h> +#include <linux/kallsyms.h> +#include <linux/kcov.h> +#include <linux/kprobes.h> +#include <linux/llist_api.h> +#include <linux/mmu_context.h> +#include <linux/mmzone.h> +#include <linux/mutex_api.h> +#include <linux/nmi.h> #include <linux/nospec.h> +#include <linux/perf_event_api.h> +#include <linux/profile.h> +#include <linux/psi.h> +#include <linux/rcuwait_api.h> +#include <linux/rseq.h> +#include <linux/sched/wake_q.h> +#include <linux/scs.h> +#include <linux/slab.h> +#include <linux/syscalls.h> +#include <linux/vtime.h> +#include <linux/wait_api.h> +#include <linux/workqueue_api.h> +#include <linux/livepatch_sched.h> + +#ifdef CONFIG_PREEMPT_DYNAMIC +# ifdef CONFIG_GENERIC_IRQ_ENTRY +# include <linux/irq-entry-common.h> +# endif +#endif -#include <linux/kcov.h> +#include <uapi/linux/sched/types.h> +#include <asm/irq_regs.h> #include <asm/switch_to.h> #include <asm/tlb.h> +#define CREATE_TRACE_POINTS +#include <linux/sched/rseq_api.h> +#include <trace/events/sched.h> +#include <trace/events/ipi.h> +#undef CREATE_TRACE_POINTS + +#include "sched.h" +#include "stats.h" + +#include "autogroup.h" +#include "pelt.h" +#include "smp.h" + #include "../workqueue_internal.h" +#include "../../io_uring/io-wq.h" #include "../smpboot.h" +#include "../locking/mutex.h" -#include "pelt.h" +EXPORT_TRACEPOINT_SYMBOL_GPL(ipi_send_cpu); +EXPORT_TRACEPOINT_SYMBOL_GPL(ipi_send_cpumask); -#define CREATE_TRACE_POINTS -#include <trace/events/sched.h> +/* + * Export tracepoints that act as a bare tracehook (ie: have no trace event + * associated with them) to allow external modules to probe them. + */ +EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_cfs_tp); +EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_rt_tp); +EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_dl_tp); +EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_irq_tp); +EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_se_tp); +EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_hw_tp); +EXPORT_TRACEPOINT_SYMBOL_GPL(sched_cpu_capacity_tp); +EXPORT_TRACEPOINT_SYMBOL_GPL(sched_overutilized_tp); +EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_cfs_tp); +EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_se_tp); +EXPORT_TRACEPOINT_SYMBOL_GPL(sched_update_nr_running_tp); +EXPORT_TRACEPOINT_SYMBOL_GPL(sched_compute_energy_tp); DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues); +DEFINE_PER_CPU(struct rnd_state, sched_rnd_state); + +#ifdef CONFIG_SCHED_PROXY_EXEC +DEFINE_STATIC_KEY_TRUE(__sched_proxy_exec); +static int __init setup_proxy_exec(char *str) +{ + bool proxy_enable = true; + + if (*str && kstrtobool(str + 1, &proxy_enable)) { + pr_warn("Unable to parse sched_proxy_exec=\n"); + return 0; + } + + if (proxy_enable) { + pr_info("sched_proxy_exec enabled via boot arg\n"); + static_branch_enable(&__sched_proxy_exec); + } else { + pr_info("sched_proxy_exec disabled via boot arg\n"); + static_branch_disable(&__sched_proxy_exec); + } + return 1; +} +#else +static int __init setup_proxy_exec(char *str) +{ + pr_warn("CONFIG_SCHED_PROXY_EXEC=n, so it cannot be enabled or disabled at boot time\n"); + return 0; +} +#endif +__setup("sched_proxy_exec", setup_proxy_exec); -#if defined(CONFIG_SCHED_DEBUG) && defined(CONFIG_JUMP_LABEL) /* * Debugging: various feature bits * @@ -34,31 +161,544 @@ DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues); */ #define SCHED_FEAT(name, enabled) \ (1UL << __SCHED_FEAT_##name) * enabled | -const_debug unsigned int sysctl_sched_features = +__read_mostly unsigned int sysctl_sched_features = #include "features.h" 0; #undef SCHED_FEAT -#endif + +/* + * Print a warning if need_resched is set for the given duration (if + * LATENCY_WARN is enabled). + * + * If sysctl_resched_latency_warn_once is set, only one warning will be shown + * per boot. + */ +__read_mostly int sysctl_resched_latency_warn_ms = 100; +__read_mostly int sysctl_resched_latency_warn_once = 1; /* * Number of tasks to iterate in a single balance run. * Limited because this is done with IRQs disabled. */ -const_debug unsigned int sysctl_sched_nr_migrate = 32; +__read_mostly unsigned int sysctl_sched_nr_migrate = SCHED_NR_MIGRATE_BREAK; + +__read_mostly int scheduler_running; + +#ifdef CONFIG_SCHED_CORE + +DEFINE_STATIC_KEY_FALSE(__sched_core_enabled); + +/* kernel prio, less is more */ +static inline int __task_prio(const struct task_struct *p) +{ + if (p->sched_class == &stop_sched_class) /* trumps deadline */ + return -2; + + if (p->dl_server) + return -1; /* deadline */ + + if (rt_or_dl_prio(p->prio)) + return p->prio; /* [-1, 99] */ + + if (p->sched_class == &idle_sched_class) + return MAX_RT_PRIO + NICE_WIDTH; /* 140 */ + + if (task_on_scx(p)) + return MAX_RT_PRIO + MAX_NICE + 1; /* 120, squash ext */ + + return MAX_RT_PRIO + MAX_NICE; /* 119, squash fair */ +} /* - * period over which we measure -rt task CPU usage in us. - * default: 1s + * l(a,b) + * le(a,b) := !l(b,a) + * g(a,b) := l(b,a) + * ge(a,b) := !l(a,b) */ -unsigned int sysctl_sched_rt_period = 1000000; -__read_mostly int scheduler_running; +/* real prio, less is less */ +static inline bool prio_less(const struct task_struct *a, + const struct task_struct *b, bool in_fi) +{ + + int pa = __task_prio(a), pb = __task_prio(b); + + if (-pa < -pb) + return true; + + if (-pb < -pa) + return false; + + if (pa == -1) { /* dl_prio() doesn't work because of stop_class above */ + const struct sched_dl_entity *a_dl, *b_dl; + + a_dl = &a->dl; + /* + * Since,'a' and 'b' can be CFS tasks served by DL server, + * __task_prio() can return -1 (for DL) even for those. In that + * case, get to the dl_server's DL entity. + */ + if (a->dl_server) + a_dl = a->dl_server; + + b_dl = &b->dl; + if (b->dl_server) + b_dl = b->dl_server; + + return !dl_time_before(a_dl->deadline, b_dl->deadline); + } + + if (pa == MAX_RT_PRIO + MAX_NICE) /* fair */ + return cfs_prio_less(a, b, in_fi); + +#ifdef CONFIG_SCHED_CLASS_EXT + if (pa == MAX_RT_PRIO + MAX_NICE + 1) /* ext */ + return scx_prio_less(a, b, in_fi); +#endif + + return false; +} + +static inline bool __sched_core_less(const struct task_struct *a, + const struct task_struct *b) +{ + if (a->core_cookie < b->core_cookie) + return true; + + if (a->core_cookie > b->core_cookie) + return false; + + /* flip prio, so high prio is leftmost */ + if (prio_less(b, a, !!task_rq(a)->core->core_forceidle_count)) + return true; + + return false; +} + +#define __node_2_sc(node) rb_entry((node), struct task_struct, core_node) + +static inline bool rb_sched_core_less(struct rb_node *a, const struct rb_node *b) +{ + return __sched_core_less(__node_2_sc(a), __node_2_sc(b)); +} + +static inline int rb_sched_core_cmp(const void *key, const struct rb_node *node) +{ + const struct task_struct *p = __node_2_sc(node); + unsigned long cookie = (unsigned long)key; + + if (cookie < p->core_cookie) + return -1; + + if (cookie > p->core_cookie) + return 1; + + return 0; +} + +void sched_core_enqueue(struct rq *rq, struct task_struct *p) +{ + if (p->se.sched_delayed) + return; + + rq->core->core_task_seq++; + + if (!p->core_cookie) + return; + + rb_add(&p->core_node, &rq->core_tree, rb_sched_core_less); +} + +void sched_core_dequeue(struct rq *rq, struct task_struct *p, int flags) +{ + if (p->se.sched_delayed) + return; + + rq->core->core_task_seq++; + + if (sched_core_enqueued(p)) { + rb_erase(&p->core_node, &rq->core_tree); + RB_CLEAR_NODE(&p->core_node); + } + + /* + * Migrating the last task off the cpu, with the cpu in forced idle + * state. Reschedule to create an accounting edge for forced idle, + * and re-examine whether the core is still in forced idle state. + */ + if (!(flags & DEQUEUE_SAVE) && rq->nr_running == 1 && + rq->core->core_forceidle_count && rq->curr == rq->idle) + resched_curr(rq); +} + +static int sched_task_is_throttled(struct task_struct *p, int cpu) +{ + if (p->sched_class->task_is_throttled) + return p->sched_class->task_is_throttled(p, cpu); + + return 0; +} + +static struct task_struct *sched_core_next(struct task_struct *p, unsigned long cookie) +{ + struct rb_node *node = &p->core_node; + int cpu = task_cpu(p); + + do { + node = rb_next(node); + if (!node) + return NULL; + + p = __node_2_sc(node); + if (p->core_cookie != cookie) + return NULL; + + } while (sched_task_is_throttled(p, cpu)); + + return p; +} + +/* + * Find left-most (aka, highest priority) and unthrottled task matching @cookie. + * If no suitable task is found, NULL will be returned. + */ +static struct task_struct *sched_core_find(struct rq *rq, unsigned long cookie) +{ + struct task_struct *p; + struct rb_node *node; + + node = rb_find_first((void *)cookie, &rq->core_tree, rb_sched_core_cmp); + if (!node) + return NULL; + + p = __node_2_sc(node); + if (!sched_task_is_throttled(p, rq->cpu)) + return p; + + return sched_core_next(p, cookie); +} /* - * part of the period that we allow rt tasks to run in us. - * default: 0.95s + * Magic required such that: + * + * raw_spin_rq_lock(rq); + * ... + * raw_spin_rq_unlock(rq); + * + * ends up locking and unlocking the _same_ lock, and all CPUs + * always agree on what rq has what lock. + * + * XXX entirely possible to selectively enable cores, don't bother for now. */ -int sysctl_sched_rt_runtime = 950000; + +static DEFINE_MUTEX(sched_core_mutex); +static atomic_t sched_core_count; +static struct cpumask sched_core_mask; + +static void sched_core_lock(int cpu, unsigned long *flags) +{ + const struct cpumask *smt_mask = cpu_smt_mask(cpu); + int t, i = 0; + + local_irq_save(*flags); + for_each_cpu(t, smt_mask) + raw_spin_lock_nested(&cpu_rq(t)->__lock, i++); +} + +static void sched_core_unlock(int cpu, unsigned long *flags) +{ + const struct cpumask *smt_mask = cpu_smt_mask(cpu); + int t; + + for_each_cpu(t, smt_mask) + raw_spin_unlock(&cpu_rq(t)->__lock); + local_irq_restore(*flags); +} + +static void __sched_core_flip(bool enabled) +{ + unsigned long flags; + int cpu, t; + + cpus_read_lock(); + + /* + * Toggle the online cores, one by one. + */ + cpumask_copy(&sched_core_mask, cpu_online_mask); + for_each_cpu(cpu, &sched_core_mask) { + const struct cpumask *smt_mask = cpu_smt_mask(cpu); + + sched_core_lock(cpu, &flags); + + for_each_cpu(t, smt_mask) + cpu_rq(t)->core_enabled = enabled; + + cpu_rq(cpu)->core->core_forceidle_start = 0; + + sched_core_unlock(cpu, &flags); + + cpumask_andnot(&sched_core_mask, &sched_core_mask, smt_mask); + } + + /* + * Toggle the offline CPUs. + */ + for_each_cpu_andnot(cpu, cpu_possible_mask, cpu_online_mask) + cpu_rq(cpu)->core_enabled = enabled; + + cpus_read_unlock(); +} + +static void sched_core_assert_empty(void) +{ + int cpu; + + for_each_possible_cpu(cpu) + WARN_ON_ONCE(!RB_EMPTY_ROOT(&cpu_rq(cpu)->core_tree)); +} + +static void __sched_core_enable(void) +{ + static_branch_enable(&__sched_core_enabled); + /* + * Ensure all previous instances of raw_spin_rq_*lock() have finished + * and future ones will observe !sched_core_disabled(). + */ + synchronize_rcu(); + __sched_core_flip(true); + sched_core_assert_empty(); +} + +static void __sched_core_disable(void) +{ + sched_core_assert_empty(); + __sched_core_flip(false); + static_branch_disable(&__sched_core_enabled); +} + +void sched_core_get(void) +{ + if (atomic_inc_not_zero(&sched_core_count)) + return; + + mutex_lock(&sched_core_mutex); + if (!atomic_read(&sched_core_count)) + __sched_core_enable(); + + smp_mb__before_atomic(); + atomic_inc(&sched_core_count); + mutex_unlock(&sched_core_mutex); +} + +static void __sched_core_put(struct work_struct *work) +{ + if (atomic_dec_and_mutex_lock(&sched_core_count, &sched_core_mutex)) { + __sched_core_disable(); + mutex_unlock(&sched_core_mutex); + } +} + +void sched_core_put(void) +{ + static DECLARE_WORK(_work, __sched_core_put); + + /* + * "There can be only one" + * + * Either this is the last one, or we don't actually need to do any + * 'work'. If it is the last *again*, we rely on + * WORK_STRUCT_PENDING_BIT. + */ + if (!atomic_add_unless(&sched_core_count, -1, 1)) + schedule_work(&_work); +} + +#else /* !CONFIG_SCHED_CORE: */ + +static inline void sched_core_enqueue(struct rq *rq, struct task_struct *p) { } +static inline void +sched_core_dequeue(struct rq *rq, struct task_struct *p, int flags) { } + +#endif /* !CONFIG_SCHED_CORE */ + +/* need a wrapper since we may need to trace from modules */ +EXPORT_TRACEPOINT_SYMBOL(sched_set_state_tp); + +/* Call via the helper macro trace_set_current_state. */ +void __trace_set_current_state(int state_value) +{ + trace_sched_set_state_tp(current, state_value); +} +EXPORT_SYMBOL(__trace_set_current_state); + +/* + * Serialization rules: + * + * Lock order: + * + * p->pi_lock + * rq->lock + * hrtimer_cpu_base->lock (hrtimer_start() for bandwidth controls) + * + * rq1->lock + * rq2->lock where: rq1 < rq2 + * + * Regular state: + * + * Normal scheduling state is serialized by rq->lock. __schedule() takes the + * local CPU's rq->lock, it optionally removes the task from the runqueue and + * always looks at the local rq data structures to find the most eligible task + * to run next. + * + * Task enqueue is also under rq->lock, possibly taken from another CPU. + * Wakeups from another LLC domain might use an IPI to transfer the enqueue to + * the local CPU to avoid bouncing the runqueue state around [ see + * ttwu_queue_wakelist() ] + * + * Task wakeup, specifically wakeups that involve migration, are horribly + * complicated to avoid having to take two rq->locks. + * + * Special state: + * + * System-calls and anything external will use task_rq_lock() which acquires + * both p->pi_lock and rq->lock. As a consequence the state they change is + * stable while holding either lock: + * + * - sched_setaffinity()/ + * set_cpus_allowed_ptr(): p->cpus_ptr, p->nr_cpus_allowed + * - set_user_nice(): p->se.load, p->*prio + * - __sched_setscheduler(): p->sched_class, p->policy, p->*prio, + * p->se.load, p->rt_priority, + * p->dl.dl_{runtime, deadline, period, flags, bw, density} + * - sched_setnuma(): p->numa_preferred_nid + * - sched_move_task(): p->sched_task_group + * - uclamp_update_active() p->uclamp* + * + * p->state <- TASK_*: + * + * is changed locklessly using set_current_state(), __set_current_state() or + * set_special_state(), see their respective comments, or by + * try_to_wake_up(). This latter uses p->pi_lock to serialize against + * concurrent self. + * + * p->on_rq <- { 0, 1 = TASK_ON_RQ_QUEUED, 2 = TASK_ON_RQ_MIGRATING }: + * + * is set by activate_task() and cleared by deactivate_task()/block_task(), + * under rq->lock. Non-zero indicates the task is runnable, the special + * ON_RQ_MIGRATING state is used for migration without holding both + * rq->locks. It indicates task_cpu() is not stable, see task_rq_lock(). + * + * Additionally it is possible to be ->on_rq but still be considered not + * runnable when p->se.sched_delayed is true. These tasks are on the runqueue + * but will be dequeued as soon as they get picked again. See the + * task_is_runnable() helper. + * + * p->on_cpu <- { 0, 1 }: + * + * is set by prepare_task() and cleared by finish_task() such that it will be + * set before p is scheduled-in and cleared after p is scheduled-out, both + * under rq->lock. Non-zero indicates the task is running on its CPU. + * + * [ The astute reader will observe that it is possible for two tasks on one + * CPU to have ->on_cpu = 1 at the same time. ] + * + * task_cpu(p): is changed by set_task_cpu(), the rules are: + * + * - Don't call set_task_cpu() on a blocked task: + * + * We don't care what CPU we're not running on, this simplifies hotplug, + * the CPU assignment of blocked tasks isn't required to be valid. + * + * - for try_to_wake_up(), called under p->pi_lock: + * + * This allows try_to_wake_up() to only take one rq->lock, see its comment. + * + * - for migration called under rq->lock: + * [ see task_on_rq_migrating() in task_rq_lock() ] + * + * o move_queued_task() + * o detach_task() + * + * - for migration called under double_rq_lock(): + * + * o __migrate_swap_task() + * o push_rt_task() / pull_rt_task() + * o push_dl_task() / pull_dl_task() + * o dl_task_offline_migration() + * + */ + +void raw_spin_rq_lock_nested(struct rq *rq, int subclass) +{ + raw_spinlock_t *lock; + + /* Matches synchronize_rcu() in __sched_core_enable() */ + preempt_disable(); + if (sched_core_disabled()) { + raw_spin_lock_nested(&rq->__lock, subclass); + /* preempt_count *MUST* be > 1 */ + preempt_enable_no_resched(); + return; + } + + for (;;) { + lock = __rq_lockp(rq); + raw_spin_lock_nested(lock, subclass); + if (likely(lock == __rq_lockp(rq))) { + /* preempt_count *MUST* be > 1 */ + preempt_enable_no_resched(); + return; + } + raw_spin_unlock(lock); + } +} + +bool raw_spin_rq_trylock(struct rq *rq) +{ + raw_spinlock_t *lock; + bool ret; + + /* Matches synchronize_rcu() in __sched_core_enable() */ + preempt_disable(); + if (sched_core_disabled()) { + ret = raw_spin_trylock(&rq->__lock); + preempt_enable(); + return ret; + } + + for (;;) { + lock = __rq_lockp(rq); + ret = raw_spin_trylock(lock); + if (!ret || (likely(lock == __rq_lockp(rq)))) { + preempt_enable(); + return ret; + } + raw_spin_unlock(lock); + } +} + +void raw_spin_rq_unlock(struct rq *rq) +{ + raw_spin_unlock(rq_lockp(rq)); +} + +/* + * double_rq_lock - safely lock two runqueues + */ +void double_rq_lock(struct rq *rq1, struct rq *rq2) +{ + lockdep_assert_irqs_disabled(); + + if (rq_order_less(rq2, rq1)) + swap(rq1, rq2); + + raw_spin_rq_lock(rq1); + if (__rq_lockp(rq1) != __rq_lockp(rq2)) + raw_spin_rq_lock_nested(rq2, SINGLE_DEPTH_NESTING); + + double_rq_clock_clear_update(rq1, rq2); +} /* * __task_rq_lock - lock the rq @p resides on. @@ -72,12 +712,12 @@ struct rq *__task_rq_lock(struct task_struct *p, struct rq_flags *rf) for (;;) { rq = task_rq(p); - raw_spin_lock(&rq->lock); + raw_spin_rq_lock(rq); if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) { rq_pin_lock(rq, rf); return rq; } - raw_spin_unlock(&rq->lock); + raw_spin_rq_unlock(rq); while (unlikely(task_on_rq_migrating(p))) cpu_relax(); @@ -96,7 +736,7 @@ struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf) for (;;) { raw_spin_lock_irqsave(&p->pi_lock, rf->flags); rq = task_rq(p); - raw_spin_lock(&rq->lock); + raw_spin_rq_lock(rq); /* * move_queued_task() task_rq_lock() * @@ -107,17 +747,18 @@ struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf) * [L] ->on_rq * RELEASE (rq->lock) * - * If we observe the old CPU in task_rq_lock, the acquire of + * If we observe the old CPU in task_rq_lock(), the acquire of * the old rq->lock will fully serialize against the stores. * - * If we observe the new CPU in task_rq_lock, the acquire will - * pair with the WMB to ensure we must then also see migrating. + * If we observe the new CPU in task_rq_lock(), the address + * dependency headed by '[L] rq = task_rq()' and the acquire + * will pair with the WMB to ensure we then also see migrating. */ if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) { rq_pin_lock(rq, rf); return rq; } - raw_spin_unlock(&rq->lock); + raw_spin_rq_unlock(rq); raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags); while (unlikely(task_on_rq_migrating(p))) @@ -138,38 +779,43 @@ static void update_rq_clock_task(struct rq *rq, s64 delta) s64 __maybe_unused steal = 0, irq_delta = 0; #ifdef CONFIG_IRQ_TIME_ACCOUNTING - irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time; + if (irqtime_enabled()) { + irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time; - /* - * Since irq_time is only updated on {soft,}irq_exit, we might run into - * this case when a previous update_rq_clock() happened inside a - * {soft,}irq region. - * - * When this happens, we stop ->clock_task and only update the - * prev_irq_time stamp to account for the part that fit, so that a next - * update will consume the rest. This ensures ->clock_task is - * monotonic. - * - * It does however cause some slight miss-attribution of {soft,}irq - * time, a more accurate solution would be to update the irq_time using - * the current rq->clock timestamp, except that would require using - * atomic ops. - */ - if (irq_delta > delta) - irq_delta = delta; + /* + * Since irq_time is only updated on {soft,}irq_exit, we might run into + * this case when a previous update_rq_clock() happened inside a + * {soft,}IRQ region. + * + * When this happens, we stop ->clock_task and only update the + * prev_irq_time stamp to account for the part that fit, so that a next + * update will consume the rest. This ensures ->clock_task is + * monotonic. + * + * It does however cause some slight miss-attribution of {soft,}IRQ + * time, a more accurate solution would be to update the irq_time using + * the current rq->clock timestamp, except that would require using + * atomic ops. + */ + if (irq_delta > delta) + irq_delta = delta; - rq->prev_irq_time += irq_delta; - delta -= irq_delta; + rq->prev_irq_time += irq_delta; + delta -= irq_delta; + delayacct_irq(rq->curr, irq_delta); + } #endif #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING if (static_key_false((¶virt_steal_rq_enabled))) { - steal = paravirt_steal_clock(cpu_of(rq)); + u64 prev_steal; + + steal = prev_steal = paravirt_steal_clock(cpu_of(rq)); steal -= rq->prev_steal_time_rq; if (unlikely(steal > delta)) steal = delta; - rq->prev_steal_time_rq += steal; + rq->prev_steal_time_rq = prev_steal; delta -= steal; } #endif @@ -180,31 +826,34 @@ static void update_rq_clock_task(struct rq *rq, s64 delta) if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY)) update_irq_load_avg(rq, irq_delta + steal); #endif + update_rq_clock_pelt(rq, delta); } void update_rq_clock(struct rq *rq) { s64 delta; + u64 clock; - lockdep_assert_held(&rq->lock); + lockdep_assert_rq_held(rq); if (rq->clock_update_flags & RQCF_ACT_SKIP) return; -#ifdef CONFIG_SCHED_DEBUG if (sched_feat(WARN_DOUBLE_CLOCK)) - SCHED_WARN_ON(rq->clock_update_flags & RQCF_UPDATED); + WARN_ON_ONCE(rq->clock_update_flags & RQCF_UPDATED); rq->clock_update_flags |= RQCF_UPDATED; -#endif - delta = sched_clock_cpu(cpu_of(rq)) - rq->clock; + clock = sched_clock_cpu(cpu_of(rq)); + scx_rq_clock_update(rq, clock); + + delta = clock - rq->clock; if (delta < 0) return; rq->clock += delta; + update_rq_clock_task(rq, delta); } - #ifdef CONFIG_SCHED_HRTICK /* * Use HR-timers to deliver accurate preemption points. @@ -229,19 +878,18 @@ static enum hrtimer_restart hrtick(struct hrtimer *timer) rq_lock(rq, &rf); update_rq_clock(rq); - rq->curr->sched_class->task_tick(rq, rq->curr, 1); + rq->donor->sched_class->task_tick(rq, rq->donor, 1); rq_unlock(rq, &rf); return HRTIMER_NORESTART; } -#ifdef CONFIG_SMP - static void __hrtick_restart(struct rq *rq) { struct hrtimer *timer = &rq->hrtick_timer; + ktime_t time = rq->hrtick_time; - hrtimer_start_expires(timer, HRTIMER_MODE_ABS_PINNED); + hrtimer_start(timer, time, HRTIMER_MODE_ABS_PINNED_HARD); } /* @@ -254,19 +902,17 @@ static void __hrtick_start(void *arg) rq_lock(rq, &rf); __hrtick_restart(rq); - rq->hrtick_csd_pending = 0; rq_unlock(rq, &rf); } /* * Called to set the hrtick timer state. * - * called with rq->lock held and irqs disabled + * called with rq->lock held and IRQs disabled */ void hrtick_start(struct rq *rq, u64 delay) { struct hrtimer *timer = &rq->hrtick_timer; - ktime_t time; s64 delta; /* @@ -274,50 +920,20 @@ void hrtick_start(struct rq *rq, u64 delay) * doesn't make sense and can cause timer DoS. */ delta = max_t(s64, delay, 10000LL); - time = ktime_add_ns(timer->base->get_time(), delta); + rq->hrtick_time = ktime_add_ns(hrtimer_cb_get_time(timer), delta); - hrtimer_set_expires(timer, time); - - if (rq == this_rq()) { + if (rq == this_rq()) __hrtick_restart(rq); - } else if (!rq->hrtick_csd_pending) { + else smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd); - rq->hrtick_csd_pending = 1; - } -} - -#else -/* - * Called to set the hrtick timer state. - * - * called with rq->lock held and irqs disabled - */ -void hrtick_start(struct rq *rq, u64 delay) -{ - /* - * Don't schedule slices shorter than 10000ns, that just - * doesn't make sense. Rely on vruntime for fairness. - */ - delay = max_t(u64, delay, 10000LL); - hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay), - HRTIMER_MODE_REL_PINNED); } -#endif /* CONFIG_SMP */ static void hrtick_rq_init(struct rq *rq) { -#ifdef CONFIG_SMP - rq->hrtick_csd_pending = 0; - - rq->hrtick_csd.flags = 0; - rq->hrtick_csd.func = __hrtick_start; - rq->hrtick_csd.info = rq; -#endif - - hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); - rq->hrtick_timer.function = hrtick; + INIT_CSD(&rq->hrtick_csd, __hrtick_start, rq); + hrtimer_setup(&rq->hrtick_timer, hrtick, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD); } -#else /* CONFIG_SCHED_HRTICK */ +#else /* !CONFIG_SCHED_HRTICK: */ static inline void hrtick_clear(struct rq *rq) { } @@ -325,36 +941,31 @@ static inline void hrtick_clear(struct rq *rq) static inline void hrtick_rq_init(struct rq *rq) { } -#endif /* CONFIG_SCHED_HRTICK */ +#endif /* !CONFIG_SCHED_HRTICK */ /* - * cmpxchg based fetch_or, macro so it works for different integer types + * try_cmpxchg based fetch_or() macro so it works for different integer types: */ #define fetch_or(ptr, mask) \ ({ \ typeof(ptr) _ptr = (ptr); \ typeof(mask) _mask = (mask); \ - typeof(*_ptr) _old, _val = *_ptr; \ + typeof(*_ptr) _val = *_ptr; \ \ - for (;;) { \ - _old = cmpxchg(_ptr, _val, _val | _mask); \ - if (_old == _val) \ - break; \ - _val = _old; \ - } \ - _old; \ + do { \ + } while (!try_cmpxchg(_ptr, &_val, _val | _mask)); \ + _val; \ }) -#if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG) +#ifdef TIF_POLLING_NRFLAG /* * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG, * this avoids any races wrt polling state changes and thereby avoids * spurious IPIs. */ -static bool set_nr_and_not_polling(struct task_struct *p) +static inline bool set_nr_and_not_polling(struct thread_info *ti, int tif) { - struct thread_info *ti = task_thread_info(p); - return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG); + return !(fetch_or(&ti->flags, 1 << tif) & _TIF_POLLING_NRFLAG); } /* @@ -366,58 +977,94 @@ static bool set_nr_and_not_polling(struct task_struct *p) static bool set_nr_if_polling(struct task_struct *p) { struct thread_info *ti = task_thread_info(p); - typeof(ti->flags) old, val = READ_ONCE(ti->flags); + typeof(ti->flags) val = READ_ONCE(ti->flags); - for (;;) { + do { if (!(val & _TIF_POLLING_NRFLAG)) return false; if (val & _TIF_NEED_RESCHED) return true; - old = cmpxchg(&ti->flags, val, val | _TIF_NEED_RESCHED); - if (old == val) - break; - val = old; - } + } while (!try_cmpxchg(&ti->flags, &val, val | _TIF_NEED_RESCHED)); + return true; } #else -static bool set_nr_and_not_polling(struct task_struct *p) +static inline bool set_nr_and_not_polling(struct thread_info *ti, int tif) { - set_tsk_need_resched(p); + set_ti_thread_flag(ti, tif); return true; } -#ifdef CONFIG_SMP -static bool set_nr_if_polling(struct task_struct *p) +static inline bool set_nr_if_polling(struct task_struct *p) { return false; } #endif -#endif -void wake_q_add(struct wake_q_head *head, struct task_struct *task) +static bool __wake_q_add(struct wake_q_head *head, struct task_struct *task) { struct wake_q_node *node = &task->wake_q; /* * Atomically grab the task, if ->wake_q is !nil already it means - * its already queued (either by us or someone else) and will get the + * it's already queued (either by us or someone else) and will get the * wakeup due to that. * - * This cmpxchg() executes a full barrier, which pairs with the full - * barrier executed by the wakeup in wake_up_q(). + * In order to ensure that a pending wakeup will observe our pending + * state, even in the failed case, an explicit smp_mb() must be used. */ - if (cmpxchg(&node->next, NULL, WAKE_Q_TAIL)) - return; - - get_task_struct(task); + smp_mb__before_atomic(); + if (unlikely(cmpxchg_relaxed(&node->next, NULL, WAKE_Q_TAIL))) + return false; /* * The head is context local, there can be no concurrency. */ *head->lastp = node; head->lastp = &node->next; + return true; +} + +/** + * wake_q_add() - queue a wakeup for 'later' waking. + * @head: the wake_q_head to add @task to + * @task: the task to queue for 'later' wakeup + * + * Queue a task for later wakeup, most likely by the wake_up_q() call in the + * same context, _HOWEVER_ this is not guaranteed, the wakeup can come + * instantly. + * + * This function must be used as-if it were wake_up_process(); IOW the task + * must be ready to be woken at this location. + */ +void wake_q_add(struct wake_q_head *head, struct task_struct *task) +{ + if (__wake_q_add(head, task)) + get_task_struct(task); +} + +/** + * wake_q_add_safe() - safely queue a wakeup for 'later' waking. + * @head: the wake_q_head to add @task to + * @task: the task to queue for 'later' wakeup + * + * Queue a task for later wakeup, most likely by the wake_up_q() call in the + * same context, _HOWEVER_ this is not guaranteed, the wakeup can come + * instantly. + * + * This function must be used as-if it were wake_up_process(); IOW the task + * must be ready to be woken at this location. + * + * This function is essentially a task-safe equivalent to wake_q_add(). Callers + * that already hold reference to @task can call the 'safe' version and trust + * wake_q to do the right thing depending whether or not the @task is already + * queued for wakeup. + */ +void wake_q_add_safe(struct wake_q_head *head, struct task_struct *task) +{ + if (!__wake_q_add(head, task)) + put_task_struct(task); } void wake_up_q(struct wake_q_head *head) @@ -428,10 +1075,10 @@ void wake_up_q(struct wake_q_head *head) struct task_struct *task; task = container_of(node, struct task_struct, wake_q); - BUG_ON(!task); - /* Task can safely be re-inserted now: */ node = node->next; - task->wake_q.next = NULL; + /* pairs with cmpxchg_relaxed() in __wake_q_add() */ + WRITE_ONCE(task->wake_q.next, NULL); + /* Task can safely be re-inserted now. */ /* * wake_up_process() executes a full barrier, which pairs with @@ -449,28 +1096,76 @@ void wake_up_q(struct wake_q_head *head) * might also involve a cross-CPU call to trigger the scheduler on * the target CPU. */ -void resched_curr(struct rq *rq) +static void __resched_curr(struct rq *rq, int tif) { struct task_struct *curr = rq->curr; + struct thread_info *cti = task_thread_info(curr); int cpu; - lockdep_assert_held(&rq->lock); + lockdep_assert_rq_held(rq); + + /* + * Always immediately preempt the idle task; no point in delaying doing + * actual work. + */ + if (is_idle_task(curr) && tif == TIF_NEED_RESCHED_LAZY) + tif = TIF_NEED_RESCHED; - if (test_tsk_need_resched(curr)) + if (cti->flags & ((1 << tif) | _TIF_NEED_RESCHED)) return; cpu = cpu_of(rq); + trace_sched_set_need_resched_tp(curr, cpu, tif); if (cpu == smp_processor_id()) { - set_tsk_need_resched(curr); - set_preempt_need_resched(); + set_ti_thread_flag(cti, tif); + if (tif == TIF_NEED_RESCHED) + set_preempt_need_resched(); return; } - if (set_nr_and_not_polling(curr)) - smp_send_reschedule(cpu); - else + if (set_nr_and_not_polling(cti, tif)) { + if (tif == TIF_NEED_RESCHED) + smp_send_reschedule(cpu); + } else { trace_sched_wake_idle_without_ipi(cpu); + } +} + +void __trace_set_need_resched(struct task_struct *curr, int tif) +{ + trace_sched_set_need_resched_tp(curr, smp_processor_id(), tif); +} + +void resched_curr(struct rq *rq) +{ + __resched_curr(rq, TIF_NEED_RESCHED); +} + +#ifdef CONFIG_PREEMPT_DYNAMIC +static DEFINE_STATIC_KEY_FALSE(sk_dynamic_preempt_lazy); +static __always_inline bool dynamic_preempt_lazy(void) +{ + return static_branch_unlikely(&sk_dynamic_preempt_lazy); +} +#else +static __always_inline bool dynamic_preempt_lazy(void) +{ + return IS_ENABLED(CONFIG_PREEMPT_LAZY); +} +#endif + +static __always_inline int get_lazy_tif_bit(void) +{ + if (dynamic_preempt_lazy()) + return TIF_NEED_RESCHED_LAZY; + + return TIF_NEED_RESCHED; +} + +void resched_curr_lazy(struct rq *rq) +{ + __resched_curr(rq, get_lazy_tif_bit()); } void resched_cpu(int cpu) @@ -478,13 +1173,12 @@ void resched_cpu(int cpu) struct rq *rq = cpu_rq(cpu); unsigned long flags; - raw_spin_lock_irqsave(&rq->lock, flags); + raw_spin_rq_lock_irqsave(rq, flags); if (cpu_online(cpu) || cpu == smp_processor_id()) resched_curr(rq); - raw_spin_unlock_irqrestore(&rq->lock, flags); + raw_spin_rq_unlock_irqrestore(rq, flags); } -#ifdef CONFIG_SMP #ifdef CONFIG_NO_HZ_COMMON /* * In the semi idle case, use the nearest busy CPU for migrating timers @@ -492,34 +1186,38 @@ void resched_cpu(int cpu) * * We don't do similar optimization for completely idle system, as * selecting an idle CPU will add more delays to the timers than intended - * (as that CPU's timer base may not be uptodate wrt jiffies etc). + * (as that CPU's timer base may not be up to date wrt jiffies etc). */ int get_nohz_timer_target(void) { - int i, cpu = smp_processor_id(); + int i, cpu = smp_processor_id(), default_cpu = -1; struct sched_domain *sd; + const struct cpumask *hk_mask; + + if (housekeeping_cpu(cpu, HK_TYPE_KERNEL_NOISE)) { + if (!idle_cpu(cpu)) + return cpu; + default_cpu = cpu; + } - if (!idle_cpu(cpu) && housekeeping_cpu(cpu, HK_FLAG_TIMER)) - return cpu; + hk_mask = housekeeping_cpumask(HK_TYPE_KERNEL_NOISE); + + guard(rcu)(); - rcu_read_lock(); for_each_domain(cpu, sd) { - for_each_cpu(i, sched_domain_span(sd)) { + for_each_cpu_and(i, sched_domain_span(sd), hk_mask) { if (cpu == i) continue; - if (!idle_cpu(i) && housekeeping_cpu(i, HK_FLAG_TIMER)) { - cpu = i; - goto unlock; - } + if (!idle_cpu(i)) + return i; } } - if (!housekeeping_cpu(cpu, HK_FLAG_TIMER)) - cpu = housekeeping_any_cpu(HK_FLAG_TIMER); -unlock: - rcu_read_unlock(); - return cpu; + if (default_cpu == -1) + default_cpu = housekeeping_any_cpu(HK_TYPE_KERNEL_NOISE); + + return default_cpu; } /* @@ -539,7 +1237,29 @@ static void wake_up_idle_cpu(int cpu) if (cpu == smp_processor_id()) return; - if (set_nr_and_not_polling(rq->idle)) + /* + * Set TIF_NEED_RESCHED and send an IPI if in the non-polling + * part of the idle loop. This forces an exit from the idle loop + * and a round trip to schedule(). Now this could be optimized + * because a simple new idle loop iteration is enough to + * re-evaluate the next tick. Provided some re-ordering of tick + * nohz functions that would need to follow TIF_NR_POLLING + * clearing: + * + * - On most architectures, a simple fetch_or on ti::flags with a + * "0" value would be enough to know if an IPI needs to be sent. + * + * - x86 needs to perform a last need_resched() check between + * monitor and mwait which doesn't take timers into account. + * There a dedicated TIF_TIMER flag would be required to + * fetch_or here and be checked along with TIF_NEED_RESCHED + * before mwait(). + * + * However, remote timer enqueue is not such a frequent event + * and testing of the above solutions didn't appear to report + * much benefits. + */ + if (set_nr_and_not_polling(task_thread_info(rq->idle), TIF_NEED_RESCHED)) smp_send_reschedule(cpu); else trace_sched_wake_idle_without_ipi(cpu); @@ -576,34 +1296,42 @@ void wake_up_nohz_cpu(int cpu) wake_up_idle_cpu(cpu); } -static inline bool got_nohz_idle_kick(void) +static void nohz_csd_func(void *info) { - int cpu = smp_processor_id(); - - if (!(atomic_read(nohz_flags(cpu)) & NOHZ_KICK_MASK)) - return false; - - if (idle_cpu(cpu) && !need_resched()) - return true; + struct rq *rq = info; + int cpu = cpu_of(rq); + unsigned int flags; /* - * We can't run Idle Load Balance on this CPU for this time so we - * cancel it and clear NOHZ_BALANCE_KICK + * Release the rq::nohz_csd. */ - atomic_andnot(NOHZ_KICK_MASK, nohz_flags(cpu)); - return false; -} - -#else /* CONFIG_NO_HZ_COMMON */ + flags = atomic_fetch_andnot(NOHZ_KICK_MASK | NOHZ_NEWILB_KICK, nohz_flags(cpu)); + WARN_ON(!(flags & NOHZ_KICK_MASK)); -static inline bool got_nohz_idle_kick(void) -{ - return false; + rq->idle_balance = idle_cpu(cpu); + if (rq->idle_balance) { + rq->nohz_idle_balance = flags; + __raise_softirq_irqoff(SCHED_SOFTIRQ); + } } #endif /* CONFIG_NO_HZ_COMMON */ #ifdef CONFIG_NO_HZ_FULL +static inline bool __need_bw_check(struct rq *rq, struct task_struct *p) +{ + if (rq->nr_running != 1) + return false; + + if (p->sched_class != &fair_sched_class) + return false; + + if (!task_on_rq_queued(p)) + return false; + + return true; +} + bool sched_can_stop_tick(struct rq *rq) { int fifo_nr_running; @@ -613,7 +1341,7 @@ bool sched_can_stop_tick(struct rq *rq) return false; /* - * If there are more than one RR tasks, we need the tick to effect the + * If there are more than one RR tasks, we need the tick to affect the * actual RR behaviour. */ if (rq->rt.rr_nr_running) { @@ -632,20 +1360,33 @@ bool sched_can_stop_tick(struct rq *rq) return true; /* - * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left; - * if there's more than one we need the tick for involuntary - * preemption. + * If there are no DL,RR/FIFO tasks, there must only be CFS or SCX tasks + * left. For CFS, if there's more than one we need the tick for + * involuntary preemption. For SCX, ask. */ - if (rq->nr_running > 1) + if (scx_enabled() && !scx_can_stop_tick(rq)) + return false; + + if (rq->cfs.h_nr_queued > 1) return false; + /* + * If there is one task and it has CFS runtime bandwidth constraints + * and it's on the cpu now we don't want to stop the tick. + * This check prevents clearing the bit if a newly enqueued task here is + * dequeued by migrating while the constrained task continues to run. + * E.g. going from 2->1 without going through pick_next_task(). + */ + if (__need_bw_check(rq, rq->curr)) { + if (cfs_task_bw_constrained(rq->curr)) + return false; + } + return true; } #endif /* CONFIG_NO_HZ_FULL */ -#endif /* CONFIG_SMP */ -#if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \ - (defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH))) +#if defined(CONFIG_RT_GROUP_SCHED) || defined(CONFIG_FAIR_GROUP_SCHED) /* * Iterate task_group tree rooted at *from, calling @down when first entering a * node and @up when leaving it for the final time. @@ -689,122 +1430,733 @@ int tg_nop(struct task_group *tg, void *data) } #endif -static void set_load_weight(struct task_struct *p, bool update_load) +void set_load_weight(struct task_struct *p, bool update_load) { int prio = p->static_prio - MAX_RT_PRIO; - struct load_weight *load = &p->se.load; + struct load_weight lw; - /* - * SCHED_IDLE tasks get minimal weight: - */ if (task_has_idle_policy(p)) { - load->weight = scale_load(WEIGHT_IDLEPRIO); - load->inv_weight = WMULT_IDLEPRIO; - p->se.runnable_weight = load->weight; - return; + lw.weight = scale_load(WEIGHT_IDLEPRIO); + lw.inv_weight = WMULT_IDLEPRIO; + } else { + lw.weight = scale_load(sched_prio_to_weight[prio]); + lw.inv_weight = sched_prio_to_wmult[prio]; } /* * SCHED_OTHER tasks have to update their load when changing their * weight */ - if (update_load && p->sched_class == &fair_sched_class) { - reweight_task(p, prio); - } else { - load->weight = scale_load(sched_prio_to_weight[prio]); - load->inv_weight = sched_prio_to_wmult[prio]; - p->se.runnable_weight = load->weight; + if (update_load && p->sched_class->reweight_task) + p->sched_class->reweight_task(task_rq(p), p, &lw); + else + p->se.load = lw; +} + +#ifdef CONFIG_UCLAMP_TASK +/* + * Serializes updates of utilization clamp values + * + * The (slow-path) user-space triggers utilization clamp value updates which + * can require updates on (fast-path) scheduler's data structures used to + * support enqueue/dequeue operations. + * While the per-CPU rq lock protects fast-path update operations, user-space + * requests are serialized using a mutex to reduce the risk of conflicting + * updates or API abuses. + */ +static __maybe_unused DEFINE_MUTEX(uclamp_mutex); + +/* Max allowed minimum utilization */ +static unsigned int __maybe_unused sysctl_sched_uclamp_util_min = SCHED_CAPACITY_SCALE; + +/* Max allowed maximum utilization */ +static unsigned int __maybe_unused sysctl_sched_uclamp_util_max = SCHED_CAPACITY_SCALE; + +/* + * By default RT tasks run at the maximum performance point/capacity of the + * system. Uclamp enforces this by always setting UCLAMP_MIN of RT tasks to + * SCHED_CAPACITY_SCALE. + * + * This knob allows admins to change the default behavior when uclamp is being + * used. In battery powered devices, particularly, running at the maximum + * capacity and frequency will increase energy consumption and shorten the + * battery life. + * + * This knob only affects RT tasks that their uclamp_se->user_defined == false. + * + * This knob will not override the system default sched_util_clamp_min defined + * above. + */ +unsigned int sysctl_sched_uclamp_util_min_rt_default = SCHED_CAPACITY_SCALE; + +/* All clamps are required to be less or equal than these values */ +static struct uclamp_se uclamp_default[UCLAMP_CNT]; + +/* + * This static key is used to reduce the uclamp overhead in the fast path. It + * primarily disables the call to uclamp_rq_{inc, dec}() in + * enqueue/dequeue_task(). + * + * This allows users to continue to enable uclamp in their kernel config with + * minimum uclamp overhead in the fast path. + * + * As soon as userspace modifies any of the uclamp knobs, the static key is + * enabled, since we have an actual users that make use of uclamp + * functionality. + * + * The knobs that would enable this static key are: + * + * * A task modifying its uclamp value with sched_setattr(). + * * An admin modifying the sysctl_sched_uclamp_{min, max} via procfs. + * * An admin modifying the cgroup cpu.uclamp.{min, max} + */ +DEFINE_STATIC_KEY_FALSE(sched_uclamp_used); + +static inline unsigned int +uclamp_idle_value(struct rq *rq, enum uclamp_id clamp_id, + unsigned int clamp_value) +{ + /* + * Avoid blocked utilization pushing up the frequency when we go + * idle (which drops the max-clamp) by retaining the last known + * max-clamp. + */ + if (clamp_id == UCLAMP_MAX) { + rq->uclamp_flags |= UCLAMP_FLAG_IDLE; + return clamp_value; } + + return uclamp_none(UCLAMP_MIN); } -static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags) +static inline void uclamp_idle_reset(struct rq *rq, enum uclamp_id clamp_id, + unsigned int clamp_value) { - if (!(flags & ENQUEUE_NOCLOCK)) - update_rq_clock(rq); + /* Reset max-clamp retention only on idle exit */ + if (!(rq->uclamp_flags & UCLAMP_FLAG_IDLE)) + return; - if (!(flags & ENQUEUE_RESTORE)) { - sched_info_queued(rq, p); - psi_enqueue(p, flags & ENQUEUE_WAKEUP); + uclamp_rq_set(rq, clamp_id, clamp_value); +} + +static inline +unsigned int uclamp_rq_max_value(struct rq *rq, enum uclamp_id clamp_id, + unsigned int clamp_value) +{ + struct uclamp_bucket *bucket = rq->uclamp[clamp_id].bucket; + int bucket_id = UCLAMP_BUCKETS - 1; + + /* + * Since both min and max clamps are max aggregated, find the + * top most bucket with tasks in. + */ + for ( ; bucket_id >= 0; bucket_id--) { + if (!bucket[bucket_id].tasks) + continue; + return bucket[bucket_id].value; } - p->sched_class->enqueue_task(rq, p, flags); + /* No tasks -- default clamp values */ + return uclamp_idle_value(rq, clamp_id, clamp_value); } -static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags) +static void __uclamp_update_util_min_rt_default(struct task_struct *p) { - if (!(flags & DEQUEUE_NOCLOCK)) - update_rq_clock(rq); + unsigned int default_util_min; + struct uclamp_se *uc_se; - if (!(flags & DEQUEUE_SAVE)) { - sched_info_dequeued(rq, p); - psi_dequeue(p, flags & DEQUEUE_SLEEP); - } + lockdep_assert_held(&p->pi_lock); + + uc_se = &p->uclamp_req[UCLAMP_MIN]; + + /* Only sync if user didn't override the default */ + if (uc_se->user_defined) + return; - p->sched_class->dequeue_task(rq, p, flags); + default_util_min = sysctl_sched_uclamp_util_min_rt_default; + uclamp_se_set(uc_se, default_util_min, false); } -void activate_task(struct rq *rq, struct task_struct *p, int flags) +static void uclamp_update_util_min_rt_default(struct task_struct *p) { - if (task_contributes_to_load(p)) - rq->nr_uninterruptible--; + if (!rt_task(p)) + return; - enqueue_task(rq, p, flags); + /* Protect updates to p->uclamp_* */ + guard(task_rq_lock)(p); + __uclamp_update_util_min_rt_default(p); } -void deactivate_task(struct rq *rq, struct task_struct *p, int flags) +static inline struct uclamp_se +uclamp_tg_restrict(struct task_struct *p, enum uclamp_id clamp_id) { - if (task_contributes_to_load(p)) - rq->nr_uninterruptible++; + /* Copy by value as we could modify it */ + struct uclamp_se uc_req = p->uclamp_req[clamp_id]; +#ifdef CONFIG_UCLAMP_TASK_GROUP + unsigned int tg_min, tg_max, value; - dequeue_task(rq, p, flags); + /* + * Tasks in autogroups or root task group will be + * restricted by system defaults. + */ + if (task_group_is_autogroup(task_group(p))) + return uc_req; + if (task_group(p) == &root_task_group) + return uc_req; + + tg_min = task_group(p)->uclamp[UCLAMP_MIN].value; + tg_max = task_group(p)->uclamp[UCLAMP_MAX].value; + value = uc_req.value; + value = clamp(value, tg_min, tg_max); + uclamp_se_set(&uc_req, value, false); +#endif + + return uc_req; +} + +/* + * The effective clamp bucket index of a task depends on, by increasing + * priority: + * - the task specific clamp value, when explicitly requested from userspace + * - the task group effective clamp value, for tasks not either in the root + * group or in an autogroup + * - the system default clamp value, defined by the sysadmin + */ +static inline struct uclamp_se +uclamp_eff_get(struct task_struct *p, enum uclamp_id clamp_id) +{ + struct uclamp_se uc_req = uclamp_tg_restrict(p, clamp_id); + struct uclamp_se uc_max = uclamp_default[clamp_id]; + + /* System default restrictions always apply */ + if (unlikely(uc_req.value > uc_max.value)) + return uc_max; + + return uc_req; +} + +unsigned long uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id) +{ + struct uclamp_se uc_eff; + + /* Task currently refcounted: use back-annotated (effective) value */ + if (p->uclamp[clamp_id].active) + return (unsigned long)p->uclamp[clamp_id].value; + + uc_eff = uclamp_eff_get(p, clamp_id); + + return (unsigned long)uc_eff.value; } /* - * __normal_prio - return the priority that is based on the static prio + * When a task is enqueued on a rq, the clamp bucket currently defined by the + * task's uclamp::bucket_id is refcounted on that rq. This also immediately + * updates the rq's clamp value if required. + * + * Tasks can have a task-specific value requested from user-space, track + * within each bucket the maximum value for tasks refcounted in it. + * This "local max aggregation" allows to track the exact "requested" value + * for each bucket when all its RUNNABLE tasks require the same clamp. */ -static inline int __normal_prio(struct task_struct *p) +static inline void uclamp_rq_inc_id(struct rq *rq, struct task_struct *p, + enum uclamp_id clamp_id) { - return p->static_prio; + struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id]; + struct uclamp_se *uc_se = &p->uclamp[clamp_id]; + struct uclamp_bucket *bucket; + + lockdep_assert_rq_held(rq); + + /* Update task effective clamp */ + p->uclamp[clamp_id] = uclamp_eff_get(p, clamp_id); + + bucket = &uc_rq->bucket[uc_se->bucket_id]; + bucket->tasks++; + uc_se->active = true; + + uclamp_idle_reset(rq, clamp_id, uc_se->value); + + /* + * Local max aggregation: rq buckets always track the max + * "requested" clamp value of its RUNNABLE tasks. + */ + if (bucket->tasks == 1 || uc_se->value > bucket->value) + bucket->value = uc_se->value; + + if (uc_se->value > uclamp_rq_get(rq, clamp_id)) + uclamp_rq_set(rq, clamp_id, uc_se->value); } /* - * Calculate the expected normal priority: i.e. priority - * without taking RT-inheritance into account. Might be - * boosted by interactivity modifiers. Changes upon fork, - * setprio syscalls, and whenever the interactivity - * estimator recalculates. + * When a task is dequeued from a rq, the clamp bucket refcounted by the task + * is released. If this is the last task reference counting the rq's max + * active clamp value, then the rq's clamp value is updated. + * + * Both refcounted tasks and rq's cached clamp values are expected to be + * always valid. If it's detected they are not, as defensive programming, + * enforce the expected state and warn. */ -static inline int normal_prio(struct task_struct *p) +static inline void uclamp_rq_dec_id(struct rq *rq, struct task_struct *p, + enum uclamp_id clamp_id) { - int prio; + struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id]; + struct uclamp_se *uc_se = &p->uclamp[clamp_id]; + struct uclamp_bucket *bucket; + unsigned int bkt_clamp; + unsigned int rq_clamp; - if (task_has_dl_policy(p)) - prio = MAX_DL_PRIO-1; - else if (task_has_rt_policy(p)) - prio = MAX_RT_PRIO-1 - p->rt_priority; - else - prio = __normal_prio(p); - return prio; + lockdep_assert_rq_held(rq); + + /* + * If sched_uclamp_used was enabled after task @p was enqueued, + * we could end up with unbalanced call to uclamp_rq_dec_id(). + * + * In this case the uc_se->active flag should be false since no uclamp + * accounting was performed at enqueue time and we can just return + * here. + * + * Need to be careful of the following enqueue/dequeue ordering + * problem too + * + * enqueue(taskA) + * // sched_uclamp_used gets enabled + * enqueue(taskB) + * dequeue(taskA) + * // Must not decrement bucket->tasks here + * dequeue(taskB) + * + * where we could end up with stale data in uc_se and + * bucket[uc_se->bucket_id]. + * + * The following check here eliminates the possibility of such race. + */ + if (unlikely(!uc_se->active)) + return; + + bucket = &uc_rq->bucket[uc_se->bucket_id]; + + WARN_ON_ONCE(!bucket->tasks); + if (likely(bucket->tasks)) + bucket->tasks--; + + uc_se->active = false; + + /* + * Keep "local max aggregation" simple and accept to (possibly) + * overboost some RUNNABLE tasks in the same bucket. + * The rq clamp bucket value is reset to its base value whenever + * there are no more RUNNABLE tasks refcounting it. + */ + if (likely(bucket->tasks)) + return; + + rq_clamp = uclamp_rq_get(rq, clamp_id); + /* + * Defensive programming: this should never happen. If it happens, + * e.g. due to future modification, warn and fix up the expected value. + */ + WARN_ON_ONCE(bucket->value > rq_clamp); + if (bucket->value >= rq_clamp) { + bkt_clamp = uclamp_rq_max_value(rq, clamp_id, uc_se->value); + uclamp_rq_set(rq, clamp_id, bkt_clamp); + } +} + +static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p, int flags) +{ + enum uclamp_id clamp_id; + + /* + * Avoid any overhead until uclamp is actually used by the userspace. + * + * The condition is constructed such that a NOP is generated when + * sched_uclamp_used is disabled. + */ + if (!uclamp_is_used()) + return; + + if (unlikely(!p->sched_class->uclamp_enabled)) + return; + + /* Only inc the delayed task which being woken up. */ + if (p->se.sched_delayed && !(flags & ENQUEUE_DELAYED)) + return; + + for_each_clamp_id(clamp_id) + uclamp_rq_inc_id(rq, p, clamp_id); + + /* Reset clamp idle holding when there is one RUNNABLE task */ + if (rq->uclamp_flags & UCLAMP_FLAG_IDLE) + rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE; +} + +static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p) +{ + enum uclamp_id clamp_id; + + /* + * Avoid any overhead until uclamp is actually used by the userspace. + * + * The condition is constructed such that a NOP is generated when + * sched_uclamp_used is disabled. + */ + if (!uclamp_is_used()) + return; + + if (unlikely(!p->sched_class->uclamp_enabled)) + return; + + if (p->se.sched_delayed) + return; + + for_each_clamp_id(clamp_id) + uclamp_rq_dec_id(rq, p, clamp_id); +} + +static inline void uclamp_rq_reinc_id(struct rq *rq, struct task_struct *p, + enum uclamp_id clamp_id) +{ + if (!p->uclamp[clamp_id].active) + return; + + uclamp_rq_dec_id(rq, p, clamp_id); + uclamp_rq_inc_id(rq, p, clamp_id); + + /* + * Make sure to clear the idle flag if we've transiently reached 0 + * active tasks on rq. + */ + if (clamp_id == UCLAMP_MAX && (rq->uclamp_flags & UCLAMP_FLAG_IDLE)) + rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE; +} + +static inline void +uclamp_update_active(struct task_struct *p) +{ + enum uclamp_id clamp_id; + struct rq_flags rf; + struct rq *rq; + + /* + * Lock the task and the rq where the task is (or was) queued. + * + * We might lock the (previous) rq of a !RUNNABLE task, but that's the + * price to pay to safely serialize util_{min,max} updates with + * enqueues, dequeues and migration operations. + * This is the same locking schema used by __set_cpus_allowed_ptr(). + */ + rq = task_rq_lock(p, &rf); + + /* + * Setting the clamp bucket is serialized by task_rq_lock(). + * If the task is not yet RUNNABLE and its task_struct is not + * affecting a valid clamp bucket, the next time it's enqueued, + * it will already see the updated clamp bucket value. + */ + for_each_clamp_id(clamp_id) + uclamp_rq_reinc_id(rq, p, clamp_id); + + task_rq_unlock(rq, p, &rf); +} + +#ifdef CONFIG_UCLAMP_TASK_GROUP +static inline void +uclamp_update_active_tasks(struct cgroup_subsys_state *css) +{ + struct css_task_iter it; + struct task_struct *p; + + css_task_iter_start(css, 0, &it); + while ((p = css_task_iter_next(&it))) + uclamp_update_active(p); + css_task_iter_end(&it); +} + +static void cpu_util_update_eff(struct cgroup_subsys_state *css); +#endif + +#ifdef CONFIG_SYSCTL +#ifdef CONFIG_UCLAMP_TASK_GROUP +static void uclamp_update_root_tg(void) +{ + struct task_group *tg = &root_task_group; + + uclamp_se_set(&tg->uclamp_req[UCLAMP_MIN], + sysctl_sched_uclamp_util_min, false); + uclamp_se_set(&tg->uclamp_req[UCLAMP_MAX], + sysctl_sched_uclamp_util_max, false); + + guard(rcu)(); + cpu_util_update_eff(&root_task_group.css); +} +#else +static void uclamp_update_root_tg(void) { } +#endif + +static void uclamp_sync_util_min_rt_default(void) +{ + struct task_struct *g, *p; + + /* + * copy_process() sysctl_uclamp + * uclamp_min_rt = X; + * write_lock(&tasklist_lock) read_lock(&tasklist_lock) + * // link thread smp_mb__after_spinlock() + * write_unlock(&tasklist_lock) read_unlock(&tasklist_lock); + * sched_post_fork() for_each_process_thread() + * __uclamp_sync_rt() __uclamp_sync_rt() + * + * Ensures that either sched_post_fork() will observe the new + * uclamp_min_rt or for_each_process_thread() will observe the new + * task. + */ + read_lock(&tasklist_lock); + smp_mb__after_spinlock(); + read_unlock(&tasklist_lock); + + guard(rcu)(); + for_each_process_thread(g, p) + uclamp_update_util_min_rt_default(p); +} + +static int sysctl_sched_uclamp_handler(const struct ctl_table *table, int write, + void *buffer, size_t *lenp, loff_t *ppos) +{ + bool update_root_tg = false; + int old_min, old_max, old_min_rt; + int result; + + guard(mutex)(&uclamp_mutex); + + old_min = sysctl_sched_uclamp_util_min; + old_max = sysctl_sched_uclamp_util_max; + old_min_rt = sysctl_sched_uclamp_util_min_rt_default; + + result = proc_dointvec(table, write, buffer, lenp, ppos); + if (result) + goto undo; + if (!write) + return 0; + + if (sysctl_sched_uclamp_util_min > sysctl_sched_uclamp_util_max || + sysctl_sched_uclamp_util_max > SCHED_CAPACITY_SCALE || + sysctl_sched_uclamp_util_min_rt_default > SCHED_CAPACITY_SCALE) { + + result = -EINVAL; + goto undo; + } + + if (old_min != sysctl_sched_uclamp_util_min) { + uclamp_se_set(&uclamp_default[UCLAMP_MIN], + sysctl_sched_uclamp_util_min, false); + update_root_tg = true; + } + if (old_max != sysctl_sched_uclamp_util_max) { + uclamp_se_set(&uclamp_default[UCLAMP_MAX], + sysctl_sched_uclamp_util_max, false); + update_root_tg = true; + } + + if (update_root_tg) { + sched_uclamp_enable(); + uclamp_update_root_tg(); + } + + if (old_min_rt != sysctl_sched_uclamp_util_min_rt_default) { + sched_uclamp_enable(); + uclamp_sync_util_min_rt_default(); + } + + /* + * We update all RUNNABLE tasks only when task groups are in use. + * Otherwise, keep it simple and do just a lazy update at each next + * task enqueue time. + */ + return 0; + +undo: + sysctl_sched_uclamp_util_min = old_min; + sysctl_sched_uclamp_util_max = old_max; + sysctl_sched_uclamp_util_min_rt_default = old_min_rt; + return result; +} +#endif /* CONFIG_SYSCTL */ + +static void uclamp_fork(struct task_struct *p) +{ + enum uclamp_id clamp_id; + + /* + * We don't need to hold task_rq_lock() when updating p->uclamp_* here + * as the task is still at its early fork stages. + */ + for_each_clamp_id(clamp_id) + p->uclamp[clamp_id].active = false; + + if (likely(!p->sched_reset_on_fork)) + return; + + for_each_clamp_id(clamp_id) { + uclamp_se_set(&p->uclamp_req[clamp_id], + uclamp_none(clamp_id), false); + } +} + +static void uclamp_post_fork(struct task_struct *p) +{ + uclamp_update_util_min_rt_default(p); +} + +static void __init init_uclamp_rq(struct rq *rq) +{ + enum uclamp_id clamp_id; + struct uclamp_rq *uc_rq = rq->uclamp; + + for_each_clamp_id(clamp_id) { + uc_rq[clamp_id] = (struct uclamp_rq) { + .value = uclamp_none(clamp_id) + }; + } + + rq->uclamp_flags = UCLAMP_FLAG_IDLE; +} + +static void __init init_uclamp(void) +{ + struct uclamp_se uc_max = {}; + enum uclamp_id clamp_id; + int cpu; + + for_each_possible_cpu(cpu) + init_uclamp_rq(cpu_rq(cpu)); + + for_each_clamp_id(clamp_id) { + uclamp_se_set(&init_task.uclamp_req[clamp_id], + uclamp_none(clamp_id), false); + } + + /* System defaults allow max clamp values for both indexes */ + uclamp_se_set(&uc_max, uclamp_none(UCLAMP_MAX), false); + for_each_clamp_id(clamp_id) { + uclamp_default[clamp_id] = uc_max; +#ifdef CONFIG_UCLAMP_TASK_GROUP + root_task_group.uclamp_req[clamp_id] = uc_max; + root_task_group.uclamp[clamp_id] = uc_max; +#endif + } +} + +#else /* !CONFIG_UCLAMP_TASK: */ +static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p, int flags) { } +static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p) { } +static inline void uclamp_fork(struct task_struct *p) { } +static inline void uclamp_post_fork(struct task_struct *p) { } +static inline void init_uclamp(void) { } +#endif /* !CONFIG_UCLAMP_TASK */ + +bool sched_task_on_rq(struct task_struct *p) +{ + return task_on_rq_queued(p); +} + +unsigned long get_wchan(struct task_struct *p) +{ + unsigned long ip = 0; + unsigned int state; + + if (!p || p == current) + return 0; + + /* Only get wchan if task is blocked and we can keep it that way. */ + raw_spin_lock_irq(&p->pi_lock); + state = READ_ONCE(p->__state); + smp_rmb(); /* see try_to_wake_up() */ + if (state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq) + ip = __get_wchan(p); + raw_spin_unlock_irq(&p->pi_lock); + + return ip; +} + +void enqueue_task(struct rq *rq, struct task_struct *p, int flags) +{ + if (!(flags & ENQUEUE_NOCLOCK)) + update_rq_clock(rq); + + /* + * Can be before ->enqueue_task() because uclamp considers the + * ENQUEUE_DELAYED task before its ->sched_delayed gets cleared + * in ->enqueue_task(). + */ + uclamp_rq_inc(rq, p, flags); + + rq->queue_mask |= p->sched_class->queue_mask; + p->sched_class->enqueue_task(rq, p, flags); + + psi_enqueue(p, flags); + + if (!(flags & ENQUEUE_RESTORE)) + sched_info_enqueue(rq, p); + + if (sched_core_enabled(rq)) + sched_core_enqueue(rq, p); } /* - * Calculate the current priority, i.e. the priority - * taken into account by the scheduler. This value might - * be boosted by RT tasks, or might be boosted by - * interactivity modifiers. Will be RT if the task got - * RT-boosted. If not then it returns p->normal_prio. + * Must only return false when DEQUEUE_SLEEP. */ -static int effective_prio(struct task_struct *p) +inline bool dequeue_task(struct rq *rq, struct task_struct *p, int flags) +{ + if (sched_core_enabled(rq)) + sched_core_dequeue(rq, p, flags); + + if (!(flags & DEQUEUE_NOCLOCK)) + update_rq_clock(rq); + + if (!(flags & DEQUEUE_SAVE)) + sched_info_dequeue(rq, p); + + psi_dequeue(p, flags); + + /* + * Must be before ->dequeue_task() because ->dequeue_task() can 'fail' + * and mark the task ->sched_delayed. + */ + uclamp_rq_dec(rq, p); + rq->queue_mask |= p->sched_class->queue_mask; + return p->sched_class->dequeue_task(rq, p, flags); +} + +void activate_task(struct rq *rq, struct task_struct *p, int flags) { - p->normal_prio = normal_prio(p); + if (task_on_rq_migrating(p)) + flags |= ENQUEUE_MIGRATED; + + enqueue_task(rq, p, flags); + + WRITE_ONCE(p->on_rq, TASK_ON_RQ_QUEUED); + ASSERT_EXCLUSIVE_WRITER(p->on_rq); +} + +void deactivate_task(struct rq *rq, struct task_struct *p, int flags) +{ + WARN_ON_ONCE(flags & DEQUEUE_SLEEP); + + WRITE_ONCE(p->on_rq, TASK_ON_RQ_MIGRATING); + ASSERT_EXCLUSIVE_WRITER(p->on_rq); + /* - * If we are RT tasks or we were boosted to RT priority, - * keep the priority unchanged. Otherwise, update priority - * to the normal priority: + * Code explicitly relies on TASK_ON_RQ_MIGRATING begin set *before* + * dequeue_task() and cleared *after* enqueue_task(). */ - if (!rt_prio(p->prio)) - return p->normal_prio; - return p->prio; + + dequeue_task(rq, p, flags); +} + +static void block_task(struct rq *rq, struct task_struct *p, int flags) +{ + if (dequeue_task(rq, p, DEQUEUE_SLEEP | flags)) + __block_task(rq, p); } /** @@ -818,77 +2170,244 @@ inline int task_curr(const struct task_struct *p) return cpu_curr(task_cpu(p)) == p; } +void wakeup_preempt(struct rq *rq, struct task_struct *p, int flags) +{ + struct task_struct *donor = rq->donor; + + if (p->sched_class == donor->sched_class) + donor->sched_class->wakeup_preempt(rq, p, flags); + else if (sched_class_above(p->sched_class, donor->sched_class)) + resched_curr(rq); + + /* + * A queue event has occurred, and we're going to schedule. In + * this case, we can save a useless back to back clock update. + */ + if (task_on_rq_queued(donor) && test_tsk_need_resched(rq->curr)) + rq_clock_skip_update(rq); +} + +static __always_inline +int __task_state_match(struct task_struct *p, unsigned int state) +{ + if (READ_ONCE(p->__state) & state) + return 1; + + if (READ_ONCE(p->saved_state) & state) + return -1; + + return 0; +} + +static __always_inline +int task_state_match(struct task_struct *p, unsigned int state) +{ + /* + * Serialize against current_save_and_set_rtlock_wait_state(), + * current_restore_rtlock_saved_state(), and __refrigerator(). + */ + guard(raw_spinlock_irq)(&p->pi_lock); + return __task_state_match(p, state); +} + /* - * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock, - * use the balance_callback list if you want balancing. + * wait_task_inactive - wait for a thread to unschedule. * - * this means any call to check_class_changed() must be followed by a call to - * balance_callback(). + * Wait for the thread to block in any of the states set in @match_state. + * If it changes, i.e. @p might have woken up, then return zero. When we + * succeed in waiting for @p to be off its CPU, we return a positive number + * (its total switch count). If a second call a short while later returns the + * same number, the caller can be sure that @p has remained unscheduled the + * whole time. + * + * The caller must ensure that the task *will* unschedule sometime soon, + * else this function might spin for a *long* time. This function can't + * be called with interrupts off, or it may introduce deadlock with + * smp_call_function() if an IPI is sent by the same process we are + * waiting to become inactive. */ -static inline void check_class_changed(struct rq *rq, struct task_struct *p, - const struct sched_class *prev_class, - int oldprio) +unsigned long wait_task_inactive(struct task_struct *p, unsigned int match_state) { - if (prev_class != p->sched_class) { - if (prev_class->switched_from) - prev_class->switched_from(rq, p); + int running, queued, match; + struct rq_flags rf; + unsigned long ncsw; + struct rq *rq; - p->sched_class->switched_to(rq, p); - } else if (oldprio != p->prio || dl_task(p)) - p->sched_class->prio_changed(rq, p, oldprio); -} + for (;;) { + /* + * We do the initial early heuristics without holding + * any task-queue locks at all. We'll only try to get + * the runqueue lock when things look like they will + * work out! + */ + rq = task_rq(p); -void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags) -{ - const struct sched_class *class; + /* + * If the task is actively running on another CPU + * still, just relax and busy-wait without holding + * any locks. + * + * NOTE! Since we don't hold any locks, it's not + * even sure that "rq" stays as the right runqueue! + * But we don't care, since "task_on_cpu()" will + * return false if the runqueue has changed and p + * is actually now running somewhere else! + */ + while (task_on_cpu(rq, p)) { + if (!task_state_match(p, match_state)) + return 0; + cpu_relax(); + } - if (p->sched_class == rq->curr->sched_class) { - rq->curr->sched_class->check_preempt_curr(rq, p, flags); - } else { - for_each_class(class) { - if (class == rq->curr->sched_class) - break; - if (class == p->sched_class) { - resched_curr(rq); - break; - } + /* + * Ok, time to look more closely! We need the rq + * lock now, to be *sure*. If we're wrong, we'll + * just go back and repeat. + */ + rq = task_rq_lock(p, &rf); + /* + * If task is sched_delayed, force dequeue it, to avoid always + * hitting the tick timeout in the queued case + */ + if (p->se.sched_delayed) + dequeue_task(rq, p, DEQUEUE_SLEEP | DEQUEUE_DELAYED); + trace_sched_wait_task(p); + running = task_on_cpu(rq, p); + queued = task_on_rq_queued(p); + ncsw = 0; + if ((match = __task_state_match(p, match_state))) { + /* + * When matching on p->saved_state, consider this task + * still queued so it will wait. + */ + if (match < 0) + queued = 1; + ncsw = p->nvcsw | LONG_MIN; /* sets MSB */ + } + task_rq_unlock(rq, p, &rf); + + /* + * If it changed from the expected state, bail out now. + */ + if (unlikely(!ncsw)) + break; + + /* + * Was it really running after all now that we + * checked with the proper locks actually held? + * + * Oops. Go back and try again.. + */ + if (unlikely(running)) { + cpu_relax(); + continue; + } + + /* + * It's not enough that it's not actively running, + * it must be off the runqueue _entirely_, and not + * preempted! + * + * So if it was still runnable (but just not actively + * running right now), it's preempted, and we should + * yield - it could be a while. + */ + if (unlikely(queued)) { + ktime_t to = NSEC_PER_SEC / HZ; + + set_current_state(TASK_UNINTERRUPTIBLE); + schedule_hrtimeout(&to, HRTIMER_MODE_REL_HARD); + continue; } + + /* + * Ahh, all good. It wasn't running, and it wasn't + * runnable, which means that it will never become + * running in the future either. We're all done! + */ + break; } - /* - * A queue event has occurred, and we're going to schedule. In - * this case, we can save a useless back to back clock update. - */ - if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr)) - rq_clock_skip_update(rq); + return ncsw; } -#ifdef CONFIG_SMP +static void +do_set_cpus_allowed(struct task_struct *p, struct affinity_context *ctx); -static inline bool is_per_cpu_kthread(struct task_struct *p) +static void migrate_disable_switch(struct rq *rq, struct task_struct *p) { - if (!(p->flags & PF_KTHREAD)) - return false; + struct affinity_context ac = { + .new_mask = cpumask_of(rq->cpu), + .flags = SCA_MIGRATE_DISABLE, + }; - if (p->nr_cpus_allowed != 1) - return false; + if (likely(!p->migration_disabled)) + return; - return true; + if (p->cpus_ptr != &p->cpus_mask) + return; + + scoped_guard (task_rq_lock, p) + do_set_cpus_allowed(p, &ac); +} + +void ___migrate_enable(void) +{ + struct task_struct *p = current; + struct affinity_context ac = { + .new_mask = &p->cpus_mask, + .flags = SCA_MIGRATE_ENABLE, + }; + + __set_cpus_allowed_ptr(p, &ac); +} +EXPORT_SYMBOL_GPL(___migrate_enable); + +void migrate_disable(void) +{ + __migrate_disable(); +} +EXPORT_SYMBOL_GPL(migrate_disable); + +void migrate_enable(void) +{ + __migrate_enable(); +} +EXPORT_SYMBOL_GPL(migrate_enable); + +static inline bool rq_has_pinned_tasks(struct rq *rq) +{ + return rq->nr_pinned; } /* - * Per-CPU kthreads are allowed to run on !actie && online CPUs, see + * Per-CPU kthreads are allowed to run on !active && online CPUs, see * __set_cpus_allowed_ptr() and select_fallback_rq(). */ static inline bool is_cpu_allowed(struct task_struct *p, int cpu) { - if (!cpumask_test_cpu(cpu, &p->cpus_allowed)) + /* When not in the task's cpumask, no point in looking further. */ + if (!task_allowed_on_cpu(p, cpu)) return false; - if (is_per_cpu_kthread(p)) + /* migrate_disabled() must be allowed to finish. */ + if (is_migration_disabled(p)) + return cpu_online(cpu); + + /* Non kernel threads are not allowed during either online or offline. */ + if (!(p->flags & PF_KTHREAD)) + return cpu_active(cpu); + + /* KTHREAD_IS_PER_CPU is always allowed. */ + if (kthread_is_per_cpu(p)) return cpu_online(cpu); - return cpu_active(cpu); + /* Regular kernel threads don't get to stay during offline. */ + if (cpu_dying(cpu)) + return false; + + /* But are allowed during online. */ + return cpu_online(cpu); } /* @@ -913,27 +2432,38 @@ static inline bool is_cpu_allowed(struct task_struct *p, int cpu) static struct rq *move_queued_task(struct rq *rq, struct rq_flags *rf, struct task_struct *p, int new_cpu) { - lockdep_assert_held(&rq->lock); + lockdep_assert_rq_held(rq); - p->on_rq = TASK_ON_RQ_MIGRATING; - dequeue_task(rq, p, DEQUEUE_NOCLOCK); + deactivate_task(rq, p, DEQUEUE_NOCLOCK); set_task_cpu(p, new_cpu); rq_unlock(rq, rf); rq = cpu_rq(new_cpu); rq_lock(rq, rf); - BUG_ON(task_cpu(p) != new_cpu); - enqueue_task(rq, p, 0); - p->on_rq = TASK_ON_RQ_QUEUED; - check_preempt_curr(rq, p, 0); + WARN_ON_ONCE(task_cpu(p) != new_cpu); + activate_task(rq, p, 0); + wakeup_preempt(rq, p, 0); return rq; } struct migration_arg { - struct task_struct *task; - int dest_cpu; + struct task_struct *task; + int dest_cpu; + struct set_affinity_pending *pending; +}; + +/* + * @refs: number of wait_for_completion() + * @stop_pending: is @stop_work in use + */ +struct set_affinity_pending { + refcount_t refs; + unsigned int stop_pending; + struct completion done; + struct cpu_stop_work stop_work; + struct migration_arg arg; }; /* @@ -952,199 +2482,756 @@ static struct rq *__migrate_task(struct rq *rq, struct rq_flags *rf, if (!is_cpu_allowed(p, dest_cpu)) return rq; - update_rq_clock(rq); rq = move_queued_task(rq, rf, p, dest_cpu); return rq; } /* - * migration_cpu_stop - this will be executed by a highprio stopper thread + * migration_cpu_stop - this will be executed by a high-prio stopper thread * and performs thread migration by bumping thread off CPU then * 'pushing' onto another runqueue. */ static int migration_cpu_stop(void *data) { struct migration_arg *arg = data; + struct set_affinity_pending *pending = arg->pending; struct task_struct *p = arg->task; struct rq *rq = this_rq(); + bool complete = false; struct rq_flags rf; /* * The original target CPU might have gone down and we might * be on another CPU but it doesn't matter. */ - local_irq_disable(); + local_irq_save(rf.flags); /* * We need to explicitly wake pending tasks before running - * __migrate_task() such that we will not miss enforcing cpus_allowed + * __migrate_task() such that we will not miss enforcing cpus_ptr * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test. */ - sched_ttwu_pending(); + flush_smp_call_function_queue(); raw_spin_lock(&p->pi_lock); rq_lock(rq, &rf); + + /* + * If we were passed a pending, then ->stop_pending was set, thus + * p->migration_pending must have remained stable. + */ + WARN_ON_ONCE(pending && pending != p->migration_pending); + /* * If task_rq(p) != rq, it cannot be migrated here, because we're * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because * we're holding p->pi_lock. */ if (task_rq(p) == rq) { - if (task_on_rq_queued(p)) + if (is_migration_disabled(p)) + goto out; + + if (pending) { + p->migration_pending = NULL; + complete = true; + + if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask)) + goto out; + } + + if (task_on_rq_queued(p)) { + update_rq_clock(rq); rq = __migrate_task(rq, &rf, p, arg->dest_cpu); - else + } else { p->wake_cpu = arg->dest_cpu; + } + + /* + * XXX __migrate_task() can fail, at which point we might end + * up running on a dodgy CPU, AFAICT this can only happen + * during CPU hotplug, at which point we'll get pushed out + * anyway, so it's probably not a big deal. + */ + + } else if (pending) { + /* + * This happens when we get migrated between migrate_enable()'s + * preempt_enable() and scheduling the stopper task. At that + * point we're a regular task again and not current anymore. + * + * A !PREEMPT kernel has a giant hole here, which makes it far + * more likely. + */ + + /* + * The task moved before the stopper got to run. We're holding + * ->pi_lock, so the allowed mask is stable - if it got + * somewhere allowed, we're done. + */ + if (cpumask_test_cpu(task_cpu(p), p->cpus_ptr)) { + p->migration_pending = NULL; + complete = true; + goto out; + } + + /* + * When migrate_enable() hits a rq mis-match we can't reliably + * determine is_migration_disabled() and so have to chase after + * it. + */ + WARN_ON_ONCE(!pending->stop_pending); + preempt_disable(); + rq_unlock(rq, &rf); + raw_spin_unlock_irqrestore(&p->pi_lock, rf.flags); + stop_one_cpu_nowait(task_cpu(p), migration_cpu_stop, + &pending->arg, &pending->stop_work); + preempt_enable(); + return 0; } +out: + if (pending) + pending->stop_pending = false; rq_unlock(rq, &rf); - raw_spin_unlock(&p->pi_lock); + raw_spin_unlock_irqrestore(&p->pi_lock, rf.flags); + + if (complete) + complete_all(&pending->done); - local_irq_enable(); return 0; } +int push_cpu_stop(void *arg) +{ + struct rq *lowest_rq = NULL, *rq = this_rq(); + struct task_struct *p = arg; + + raw_spin_lock_irq(&p->pi_lock); + raw_spin_rq_lock(rq); + + if (task_rq(p) != rq) + goto out_unlock; + + if (is_migration_disabled(p)) { + p->migration_flags |= MDF_PUSH; + goto out_unlock; + } + + p->migration_flags &= ~MDF_PUSH; + + if (p->sched_class->find_lock_rq) + lowest_rq = p->sched_class->find_lock_rq(p, rq); + + if (!lowest_rq) + goto out_unlock; + + // XXX validate p is still the highest prio task + if (task_rq(p) == rq) { + move_queued_task_locked(rq, lowest_rq, p); + resched_curr(lowest_rq); + } + + double_unlock_balance(rq, lowest_rq); + +out_unlock: + rq->push_busy = false; + raw_spin_rq_unlock(rq); + raw_spin_unlock_irq(&p->pi_lock); + + put_task_struct(p); + return 0; +} + +static inline void mm_update_cpus_allowed(struct mm_struct *mm, const cpumask_t *affmask); + /* * sched_class::set_cpus_allowed must do the below, but is not required to * actually call this function. */ -void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask) +void set_cpus_allowed_common(struct task_struct *p, struct affinity_context *ctx) +{ + if (ctx->flags & (SCA_MIGRATE_ENABLE | SCA_MIGRATE_DISABLE)) { + p->cpus_ptr = ctx->new_mask; + return; + } + + cpumask_copy(&p->cpus_mask, ctx->new_mask); + p->nr_cpus_allowed = cpumask_weight(ctx->new_mask); + mm_update_cpus_allowed(p->mm, ctx->new_mask); + + /* + * Swap in a new user_cpus_ptr if SCA_USER flag set + */ + if (ctx->flags & SCA_USER) + swap(p->user_cpus_ptr, ctx->user_mask); +} + +static void +do_set_cpus_allowed(struct task_struct *p, struct affinity_context *ctx) { - cpumask_copy(&p->cpus_allowed, new_mask); - p->nr_cpus_allowed = cpumask_weight(new_mask); + scoped_guard (sched_change, p, DEQUEUE_SAVE) + p->sched_class->set_cpus_allowed(p, ctx); } -void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask) +/* + * Used for kthread_bind() and select_fallback_rq(), in both cases the user + * affinity (if any) should be destroyed too. + */ +void set_cpus_allowed_force(struct task_struct *p, const struct cpumask *new_mask) { - struct rq *rq = task_rq(p); - bool queued, running; + struct affinity_context ac = { + .new_mask = new_mask, + .user_mask = NULL, + .flags = SCA_USER, /* clear the user requested mask */ + }; + union cpumask_rcuhead { + cpumask_t cpumask; + struct rcu_head rcu; + }; - lockdep_assert_held(&p->pi_lock); + scoped_guard (__task_rq_lock, p) + do_set_cpus_allowed(p, &ac); + + /* + * Because this is called with p->pi_lock held, it is not possible + * to use kfree() here (when PREEMPT_RT=y), therefore punt to using + * kfree_rcu(). + */ + kfree_rcu((union cpumask_rcuhead *)ac.user_mask, rcu); +} + +int dup_user_cpus_ptr(struct task_struct *dst, struct task_struct *src, + int node) +{ + cpumask_t *user_mask; + unsigned long flags; + + /* + * Always clear dst->user_cpus_ptr first as their user_cpus_ptr's + * may differ by now due to racing. + */ + dst->user_cpus_ptr = NULL; + + /* + * This check is racy and losing the race is a valid situation. + * It is not worth the extra overhead of taking the pi_lock on + * every fork/clone. + */ + if (data_race(!src->user_cpus_ptr)) + return 0; + + user_mask = alloc_user_cpus_ptr(node); + if (!user_mask) + return -ENOMEM; + + /* + * Use pi_lock to protect content of user_cpus_ptr + * + * Though unlikely, user_cpus_ptr can be reset to NULL by a concurrent + * set_cpus_allowed_force(). + */ + raw_spin_lock_irqsave(&src->pi_lock, flags); + if (src->user_cpus_ptr) { + swap(dst->user_cpus_ptr, user_mask); + cpumask_copy(dst->user_cpus_ptr, src->user_cpus_ptr); + } + raw_spin_unlock_irqrestore(&src->pi_lock, flags); + + if (unlikely(user_mask)) + kfree(user_mask); + + return 0; +} + +static inline struct cpumask *clear_user_cpus_ptr(struct task_struct *p) +{ + struct cpumask *user_mask = NULL; + + swap(p->user_cpus_ptr, user_mask); + + return user_mask; +} + +void release_user_cpus_ptr(struct task_struct *p) +{ + kfree(clear_user_cpus_ptr(p)); +} - queued = task_on_rq_queued(p); - running = task_current(rq, p); +/* + * This function is wildly self concurrent; here be dragons. + * + * + * When given a valid mask, __set_cpus_allowed_ptr() must block until the + * designated task is enqueued on an allowed CPU. If that task is currently + * running, we have to kick it out using the CPU stopper. + * + * Migrate-Disable comes along and tramples all over our nice sandcastle. + * Consider: + * + * Initial conditions: P0->cpus_mask = [0, 1] + * + * P0@CPU0 P1 + * + * migrate_disable(); + * <preempted> + * set_cpus_allowed_ptr(P0, [1]); + * + * P1 *cannot* return from this set_cpus_allowed_ptr() call until P0 executes + * its outermost migrate_enable() (i.e. it exits its Migrate-Disable region). + * This means we need the following scheme: + * + * P0@CPU0 P1 + * + * migrate_disable(); + * <preempted> + * set_cpus_allowed_ptr(P0, [1]); + * <blocks> + * <resumes> + * migrate_enable(); + * __set_cpus_allowed_ptr(); + * <wakes local stopper> + * `--> <woken on migration completion> + * + * Now the fun stuff: there may be several P1-like tasks, i.e. multiple + * concurrent set_cpus_allowed_ptr(P0, [*]) calls. CPU affinity changes of any + * task p are serialized by p->pi_lock, which we can leverage: the one that + * should come into effect at the end of the Migrate-Disable region is the last + * one. This means we only need to track a single cpumask (i.e. p->cpus_mask), + * but we still need to properly signal those waiting tasks at the appropriate + * moment. + * + * This is implemented using struct set_affinity_pending. The first + * __set_cpus_allowed_ptr() caller within a given Migrate-Disable region will + * setup an instance of that struct and install it on the targeted task_struct. + * Any and all further callers will reuse that instance. Those then wait for + * a completion signaled at the tail of the CPU stopper callback (1), triggered + * on the end of the Migrate-Disable region (i.e. outermost migrate_enable()). + * + * + * (1) In the cases covered above. There is one more where the completion is + * signaled within affine_move_task() itself: when a subsequent affinity request + * occurs after the stopper bailed out due to the targeted task still being + * Migrate-Disable. Consider: + * + * Initial conditions: P0->cpus_mask = [0, 1] + * + * CPU0 P1 P2 + * <P0> + * migrate_disable(); + * <preempted> + * set_cpus_allowed_ptr(P0, [1]); + * <blocks> + * <migration/0> + * migration_cpu_stop() + * is_migration_disabled() + * <bails> + * set_cpus_allowed_ptr(P0, [0, 1]); + * <signal completion> + * <awakes> + * + * Note that the above is safe vs a concurrent migrate_enable(), as any + * pending affinity completion is preceded by an uninstallation of + * p->migration_pending done with p->pi_lock held. + */ +static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flags *rf, + int dest_cpu, unsigned int flags) + __releases(rq->lock) + __releases(p->pi_lock) +{ + struct set_affinity_pending my_pending = { }, *pending = NULL; + bool stop_pending, complete = false; + + /* + * Can the task run on the task's current CPU? If so, we're done + * + * We are also done if the task is the current donor, boosting a lock- + * holding proxy, (and potentially has been migrated outside its + * current or previous affinity mask) + */ + if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask) || + (task_current_donor(rq, p) && !task_current(rq, p))) { + struct task_struct *push_task = NULL; + + if ((flags & SCA_MIGRATE_ENABLE) && + (p->migration_flags & MDF_PUSH) && !rq->push_busy) { + rq->push_busy = true; + push_task = get_task_struct(p); + } - if (queued) { /* - * Because __kthread_bind() calls this on blocked tasks without - * holding rq->lock. + * If there are pending waiters, but no pending stop_work, + * then complete now. */ - lockdep_assert_held(&rq->lock); - dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK); + pending = p->migration_pending; + if (pending && !pending->stop_pending) { + p->migration_pending = NULL; + complete = true; + } + + preempt_disable(); + task_rq_unlock(rq, p, rf); + if (push_task) { + stop_one_cpu_nowait(rq->cpu, push_cpu_stop, + p, &rq->push_work); + } + preempt_enable(); + + if (complete) + complete_all(&pending->done); + + return 0; } - if (running) - put_prev_task(rq, p); - p->sched_class->set_cpus_allowed(p, new_mask); + if (!(flags & SCA_MIGRATE_ENABLE)) { + /* serialized by p->pi_lock */ + if (!p->migration_pending) { + /* Install the request */ + refcount_set(&my_pending.refs, 1); + init_completion(&my_pending.done); + my_pending.arg = (struct migration_arg) { + .task = p, + .dest_cpu = dest_cpu, + .pending = &my_pending, + }; + + p->migration_pending = &my_pending; + } else { + pending = p->migration_pending; + refcount_inc(&pending->refs); + /* + * Affinity has changed, but we've already installed a + * pending. migration_cpu_stop() *must* see this, else + * we risk a completion of the pending despite having a + * task on a disallowed CPU. + * + * Serialized by p->pi_lock, so this is safe. + */ + pending->arg.dest_cpu = dest_cpu; + } + } + pending = p->migration_pending; + /* + * - !MIGRATE_ENABLE: + * we'll have installed a pending if there wasn't one already. + * + * - MIGRATE_ENABLE: + * we're here because the current CPU isn't matching anymore, + * the only way that can happen is because of a concurrent + * set_cpus_allowed_ptr() call, which should then still be + * pending completion. + * + * Either way, we really should have a @pending here. + */ + if (WARN_ON_ONCE(!pending)) { + task_rq_unlock(rq, p, rf); + return -EINVAL; + } + + if (task_on_cpu(rq, p) || READ_ONCE(p->__state) == TASK_WAKING) { + /* + * MIGRATE_ENABLE gets here because 'p == current', but for + * anything else we cannot do is_migration_disabled(), punt + * and have the stopper function handle it all race-free. + */ + stop_pending = pending->stop_pending; + if (!stop_pending) + pending->stop_pending = true; + + if (flags & SCA_MIGRATE_ENABLE) + p->migration_flags &= ~MDF_PUSH; + + preempt_disable(); + task_rq_unlock(rq, p, rf); + if (!stop_pending) { + stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop, + &pending->arg, &pending->stop_work); + } + preempt_enable(); + + if (flags & SCA_MIGRATE_ENABLE) + return 0; + } else { + + if (!is_migration_disabled(p)) { + if (task_on_rq_queued(p)) + rq = move_queued_task(rq, rf, p, dest_cpu); + + if (!pending->stop_pending) { + p->migration_pending = NULL; + complete = true; + } + } + task_rq_unlock(rq, p, rf); + + if (complete) + complete_all(&pending->done); + } + + wait_for_completion(&pending->done); + + if (refcount_dec_and_test(&pending->refs)) + wake_up_var(&pending->refs); /* No UaF, just an address */ + + /* + * Block the original owner of &pending until all subsequent callers + * have seen the completion and decremented the refcount + */ + wait_var_event(&my_pending.refs, !refcount_read(&my_pending.refs)); + + /* ARGH */ + WARN_ON_ONCE(my_pending.stop_pending); - if (queued) - enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK); - if (running) - set_curr_task(rq, p); + return 0; } /* - * Change a given task's CPU affinity. Migrate the thread to a - * proper CPU and schedule it away if the CPU it's executing on - * is removed from the allowed bitmask. - * - * NOTE: the caller must have a valid reference to the task, the - * task must not exit() & deallocate itself prematurely. The - * call is not atomic; no spinlocks may be held. + * Called with both p->pi_lock and rq->lock held; drops both before returning. */ -static int __set_cpus_allowed_ptr(struct task_struct *p, - const struct cpumask *new_mask, bool check) +static int __set_cpus_allowed_ptr_locked(struct task_struct *p, + struct affinity_context *ctx, + struct rq *rq, + struct rq_flags *rf) + __releases(rq->lock) + __releases(p->pi_lock) { + const struct cpumask *cpu_allowed_mask = task_cpu_possible_mask(p); const struct cpumask *cpu_valid_mask = cpu_active_mask; + bool kthread = p->flags & PF_KTHREAD; unsigned int dest_cpu; - struct rq_flags rf; - struct rq *rq; int ret = 0; - rq = task_rq_lock(p, &rf); - update_rq_clock(rq); - - if (p->flags & PF_KTHREAD) { + if (kthread || is_migration_disabled(p)) { /* - * Kernel threads are allowed on online && !active CPUs + * Kernel threads are allowed on online && !active CPUs, + * however, during cpu-hot-unplug, even these might get pushed + * away if not KTHREAD_IS_PER_CPU. + * + * Specifically, migration_disabled() tasks must not fail the + * cpumask_any_and_distribute() pick below, esp. so on + * SCA_MIGRATE_ENABLE, otherwise we'll not call + * set_cpus_allowed_common() and actually reset p->cpus_ptr. */ cpu_valid_mask = cpu_online_mask; } + if (!kthread && !cpumask_subset(ctx->new_mask, cpu_allowed_mask)) { + ret = -EINVAL; + goto out; + } + /* * Must re-check here, to close a race against __kthread_bind(), * sched_setaffinity() is not guaranteed to observe the flag. */ - if (check && (p->flags & PF_NO_SETAFFINITY)) { + if ((ctx->flags & SCA_CHECK) && (p->flags & PF_NO_SETAFFINITY)) { ret = -EINVAL; goto out; } - if (cpumask_equal(&p->cpus_allowed, new_mask)) - goto out; + if (!(ctx->flags & SCA_MIGRATE_ENABLE)) { + if (cpumask_equal(&p->cpus_mask, ctx->new_mask)) { + if (ctx->flags & SCA_USER) + swap(p->user_cpus_ptr, ctx->user_mask); + goto out; + } + + if (WARN_ON_ONCE(p == current && + is_migration_disabled(p) && + !cpumask_test_cpu(task_cpu(p), ctx->new_mask))) { + ret = -EBUSY; + goto out; + } + } - if (!cpumask_intersects(new_mask, cpu_valid_mask)) { + /* + * Picking a ~random cpu helps in cases where we are changing affinity + * for groups of tasks (ie. cpuset), so that load balancing is not + * immediately required to distribute the tasks within their new mask. + */ + dest_cpu = cpumask_any_and_distribute(cpu_valid_mask, ctx->new_mask); + if (dest_cpu >= nr_cpu_ids) { ret = -EINVAL; goto out; } - do_set_cpus_allowed(p, new_mask); + do_set_cpus_allowed(p, ctx); - if (p->flags & PF_KTHREAD) { - /* - * For kernel threads that do indeed end up on online && - * !active we want to ensure they are strict per-CPU threads. - */ - WARN_ON(cpumask_intersects(new_mask, cpu_online_mask) && - !cpumask_intersects(new_mask, cpu_active_mask) && - p->nr_cpus_allowed != 1); - } + return affine_move_task(rq, p, rf, dest_cpu, ctx->flags); - /* Can the task run on the task's current CPU? If so, we're done */ - if (cpumask_test_cpu(task_cpu(p), new_mask)) - goto out; - - dest_cpu = cpumask_any_and(cpu_valid_mask, new_mask); - if (task_running(rq, p) || p->state == TASK_WAKING) { - struct migration_arg arg = { p, dest_cpu }; - /* Need help from migration thread: drop lock and wait. */ - task_rq_unlock(rq, p, &rf); - stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg); - tlb_migrate_finish(p->mm); - return 0; - } else if (task_on_rq_queued(p)) { - /* - * OK, since we're going to drop the lock immediately - * afterwards anyway. - */ - rq = move_queued_task(rq, &rf, p, dest_cpu); - } out: - task_rq_unlock(rq, p, &rf); + task_rq_unlock(rq, p, rf); return ret; } +/* + * Change a given task's CPU affinity. Migrate the thread to a + * proper CPU and schedule it away if the CPU it's executing on + * is removed from the allowed bitmask. + * + * NOTE: the caller must have a valid reference to the task, the + * task must not exit() & deallocate itself prematurely. The + * call is not atomic; no spinlocks may be held. + */ +int __set_cpus_allowed_ptr(struct task_struct *p, struct affinity_context *ctx) +{ + struct rq_flags rf; + struct rq *rq; + + rq = task_rq_lock(p, &rf); + /* + * Masking should be skipped if SCA_USER or any of the SCA_MIGRATE_* + * flags are set. + */ + if (p->user_cpus_ptr && + !(ctx->flags & (SCA_USER | SCA_MIGRATE_ENABLE | SCA_MIGRATE_DISABLE)) && + cpumask_and(rq->scratch_mask, ctx->new_mask, p->user_cpus_ptr)) + ctx->new_mask = rq->scratch_mask; + + return __set_cpus_allowed_ptr_locked(p, ctx, rq, &rf); +} + int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask) { - return __set_cpus_allowed_ptr(p, new_mask, false); + struct affinity_context ac = { + .new_mask = new_mask, + .flags = 0, + }; + + return __set_cpus_allowed_ptr(p, &ac); } EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr); +/* + * Change a given task's CPU affinity to the intersection of its current + * affinity mask and @subset_mask, writing the resulting mask to @new_mask. + * If user_cpus_ptr is defined, use it as the basis for restricting CPU + * affinity or use cpu_online_mask instead. + * + * If the resulting mask is empty, leave the affinity unchanged and return + * -EINVAL. + */ +static int restrict_cpus_allowed_ptr(struct task_struct *p, + struct cpumask *new_mask, + const struct cpumask *subset_mask) +{ + struct affinity_context ac = { + .new_mask = new_mask, + .flags = 0, + }; + struct rq_flags rf; + struct rq *rq; + int err; + + rq = task_rq_lock(p, &rf); + + /* + * Forcefully restricting the affinity of a deadline task is + * likely to cause problems, so fail and noisily override the + * mask entirely. + */ + if (task_has_dl_policy(p) && dl_bandwidth_enabled()) { + err = -EPERM; + goto err_unlock; + } + + if (!cpumask_and(new_mask, task_user_cpus(p), subset_mask)) { + err = -EINVAL; + goto err_unlock; + } + + return __set_cpus_allowed_ptr_locked(p, &ac, rq, &rf); + +err_unlock: + task_rq_unlock(rq, p, &rf); + return err; +} + +/* + * Restrict the CPU affinity of task @p so that it is a subset of + * task_cpu_possible_mask() and point @p->user_cpus_ptr to a copy of the + * old affinity mask. If the resulting mask is empty, we warn and walk + * up the cpuset hierarchy until we find a suitable mask. + */ +void force_compatible_cpus_allowed_ptr(struct task_struct *p) +{ + cpumask_var_t new_mask; + const struct cpumask *override_mask = task_cpu_possible_mask(p); + + alloc_cpumask_var(&new_mask, GFP_KERNEL); + + /* + * __migrate_task() can fail silently in the face of concurrent + * offlining of the chosen destination CPU, so take the hotplug + * lock to ensure that the migration succeeds. + */ + cpus_read_lock(); + if (!cpumask_available(new_mask)) + goto out_set_mask; + + if (!restrict_cpus_allowed_ptr(p, new_mask, override_mask)) + goto out_free_mask; + + /* + * We failed to find a valid subset of the affinity mask for the + * task, so override it based on its cpuset hierarchy. + */ + cpuset_cpus_allowed(p, new_mask); + override_mask = new_mask; + +out_set_mask: + if (printk_ratelimit()) { + printk_deferred("Overriding affinity for process %d (%s) to CPUs %*pbl\n", + task_pid_nr(p), p->comm, + cpumask_pr_args(override_mask)); + } + + WARN_ON(set_cpus_allowed_ptr(p, override_mask)); +out_free_mask: + cpus_read_unlock(); + free_cpumask_var(new_mask); +} + +/* + * Restore the affinity of a task @p which was previously restricted by a + * call to force_compatible_cpus_allowed_ptr(). + * + * It is the caller's responsibility to serialise this with any calls to + * force_compatible_cpus_allowed_ptr(@p). + */ +void relax_compatible_cpus_allowed_ptr(struct task_struct *p) +{ + struct affinity_context ac = { + .new_mask = task_user_cpus(p), + .flags = 0, + }; + int ret; + + /* + * Try to restore the old affinity mask with __sched_setaffinity(). + * Cpuset masking will be done there too. + */ + ret = __sched_setaffinity(p, &ac); + WARN_ON_ONCE(ret); +} + +#ifdef CONFIG_SMP + void set_task_cpu(struct task_struct *p, unsigned int new_cpu) { -#ifdef CONFIG_SCHED_DEBUG + unsigned int state = READ_ONCE(p->__state); + /* * We should never call set_task_cpu() on a blocked task, * ttwu() will sort out the placement. */ - WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING && - !p->on_rq); + WARN_ON_ONCE(state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq); /* * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING, * because schedstat_wait_{start,end} rebase migrating task's wait_start * time relying on p->on_rq. */ - WARN_ON_ONCE(p->state == TASK_RUNNING && + WARN_ON_ONCE(state == TASK_RUNNING && p->sched_class == &fair_sched_class && (p->on_rq && !task_on_rq_migrating(p))); @@ -1160,13 +3247,14 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu) * task_rq_lock(). */ WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) || - lockdep_is_held(&task_rq(p)->lock))); + lockdep_is_held(__rq_lockp(task_rq(p))))); #endif /* * Clearly, migrating tasks to offline CPUs is a fairly daft thing. */ WARN_ON_ONCE(!cpu_online(new_cpu)); -#endif + + WARN_ON_ONCE(is_migration_disabled(p)); trace_sched_migrate_task(p, new_cpu); @@ -1174,12 +3262,12 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu) if (p->sched_class->migrate_task_rq) p->sched_class->migrate_task_rq(p, new_cpu); p->se.nr_migrations++; - rseq_migrate(p); perf_event_task_migrate(p); } __set_task_cpu(p, new_cpu); } +#endif /* CONFIG_SMP */ #ifdef CONFIG_NUMA_BALANCING static void __migrate_swap_task(struct task_struct *p, int cpu) @@ -1194,12 +3282,8 @@ static void __migrate_swap_task(struct task_struct *p, int cpu) rq_pin_lock(src_rq, &srf); rq_pin_lock(dst_rq, &drf); - p->on_rq = TASK_ON_RQ_MIGRATING; - deactivate_task(src_rq, p, 0); - set_task_cpu(p, cpu); - activate_task(dst_rq, p, 0); - p->on_rq = TASK_ON_RQ_QUEUED; - check_preempt_curr(dst_rq, p, 0); + move_queued_task_locked(src_rq, dst_rq, p); + wakeup_preempt(dst_rq, p, 0); rq_unpin_lock(dst_rq, &drf); rq_unpin_lock(src_rq, &srf); @@ -1223,7 +3307,6 @@ static int migrate_swap_stop(void *data) { struct migration_swap_arg *arg = data; struct rq *src_rq, *dst_rq; - int ret = -EAGAIN; if (!cpu_active(arg->src_cpu) || !cpu_active(arg->dst_cpu)) return -EAGAIN; @@ -1231,33 +3314,25 @@ static int migrate_swap_stop(void *data) src_rq = cpu_rq(arg->src_cpu); dst_rq = cpu_rq(arg->dst_cpu); - double_raw_lock(&arg->src_task->pi_lock, - &arg->dst_task->pi_lock); - double_rq_lock(src_rq, dst_rq); + guard(double_raw_spinlock)(&arg->src_task->pi_lock, &arg->dst_task->pi_lock); + guard(double_rq_lock)(src_rq, dst_rq); if (task_cpu(arg->dst_task) != arg->dst_cpu) - goto unlock; + return -EAGAIN; if (task_cpu(arg->src_task) != arg->src_cpu) - goto unlock; + return -EAGAIN; - if (!cpumask_test_cpu(arg->dst_cpu, &arg->src_task->cpus_allowed)) - goto unlock; + if (!cpumask_test_cpu(arg->dst_cpu, arg->src_task->cpus_ptr)) + return -EAGAIN; - if (!cpumask_test_cpu(arg->src_cpu, &arg->dst_task->cpus_allowed)) - goto unlock; + if (!cpumask_test_cpu(arg->src_cpu, arg->dst_task->cpus_ptr)) + return -EAGAIN; __migrate_swap_task(arg->src_task, arg->dst_cpu); __migrate_swap_task(arg->dst_task, arg->src_cpu); - ret = 0; - -unlock: - double_rq_unlock(src_rq, dst_rq); - raw_spin_unlock(&arg->dst_task->pi_lock); - raw_spin_unlock(&arg->src_task->pi_lock); - - return ret; + return 0; } /* @@ -1286,10 +3361,10 @@ int migrate_swap(struct task_struct *cur, struct task_struct *p, if (!cpu_active(arg.src_cpu) || !cpu_active(arg.dst_cpu)) goto out; - if (!cpumask_test_cpu(arg.dst_cpu, &arg.src_task->cpus_allowed)) + if (!cpumask_test_cpu(arg.dst_cpu, arg.src_task->cpus_ptr)) goto out; - if (!cpumask_test_cpu(arg.src_cpu, &arg.dst_task->cpus_allowed)) + if (!cpumask_test_cpu(arg.src_cpu, arg.dst_task->cpus_ptr)) goto out; trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu); @@ -1300,114 +3375,6 @@ out: } #endif /* CONFIG_NUMA_BALANCING */ -/* - * wait_task_inactive - wait for a thread to unschedule. - * - * If @match_state is nonzero, it's the @p->state value just checked and - * not expected to change. If it changes, i.e. @p might have woken up, - * then return zero. When we succeed in waiting for @p to be off its CPU, - * we return a positive number (its total switch count). If a second call - * a short while later returns the same number, the caller can be sure that - * @p has remained unscheduled the whole time. - * - * The caller must ensure that the task *will* unschedule sometime soon, - * else this function might spin for a *long* time. This function can't - * be called with interrupts off, or it may introduce deadlock with - * smp_call_function() if an IPI is sent by the same process we are - * waiting to become inactive. - */ -unsigned long wait_task_inactive(struct task_struct *p, long match_state) -{ - int running, queued; - struct rq_flags rf; - unsigned long ncsw; - struct rq *rq; - - for (;;) { - /* - * We do the initial early heuristics without holding - * any task-queue locks at all. We'll only try to get - * the runqueue lock when things look like they will - * work out! - */ - rq = task_rq(p); - - /* - * If the task is actively running on another CPU - * still, just relax and busy-wait without holding - * any locks. - * - * NOTE! Since we don't hold any locks, it's not - * even sure that "rq" stays as the right runqueue! - * But we don't care, since "task_running()" will - * return false if the runqueue has changed and p - * is actually now running somewhere else! - */ - while (task_running(rq, p)) { - if (match_state && unlikely(p->state != match_state)) - return 0; - cpu_relax(); - } - - /* - * Ok, time to look more closely! We need the rq - * lock now, to be *sure*. If we're wrong, we'll - * just go back and repeat. - */ - rq = task_rq_lock(p, &rf); - trace_sched_wait_task(p); - running = task_running(rq, p); - queued = task_on_rq_queued(p); - ncsw = 0; - if (!match_state || p->state == match_state) - ncsw = p->nvcsw | LONG_MIN; /* sets MSB */ - task_rq_unlock(rq, p, &rf); - - /* - * If it changed from the expected state, bail out now. - */ - if (unlikely(!ncsw)) - break; - - /* - * Was it really running after all now that we - * checked with the proper locks actually held? - * - * Oops. Go back and try again.. - */ - if (unlikely(running)) { - cpu_relax(); - continue; - } - - /* - * It's not enough that it's not actively running, - * it must be off the runqueue _entirely_, and not - * preempted! - * - * So if it was still runnable (but just not actively - * running right now), it's preempted, and we should - * yield - it could be a while. - */ - if (unlikely(queued)) { - ktime_t to = NSEC_PER_SEC / HZ; - - set_current_state(TASK_UNINTERRUPTIBLE); - schedule_hrtimeout(&to, HRTIMER_MODE_REL); - continue; - } - - /* - * Ahh, all good. It wasn't running, and it wasn't - * runnable, which means that it will never become - * running in the future either. We're all done! - */ - break; - } - - return ncsw; -} - /*** * kick_process - kick a running thread to enter/exit the kernel * @p: the to-be-kicked thread @@ -1423,18 +3390,16 @@ unsigned long wait_task_inactive(struct task_struct *p, long match_state) */ void kick_process(struct task_struct *p) { - int cpu; + guard(preempt)(); + int cpu = task_cpu(p); - preempt_disable(); - cpu = task_cpu(p); if ((cpu != smp_processor_id()) && task_curr(p)) smp_send_reschedule(cpu); - preempt_enable(); } EXPORT_SYMBOL_GPL(kick_process); /* - * ->cpus_allowed is protected by both rq->lock and p->pi_lock + * ->cpus_ptr is protected by both rq->lock and p->pi_lock * * A few notes on cpu_active vs cpu_online: * @@ -1472,16 +3437,14 @@ static int select_fallback_rq(int cpu, struct task_struct *p) /* Look for allowed, online CPU in same node. */ for_each_cpu(dest_cpu, nodemask) { - if (!cpu_active(dest_cpu)) - continue; - if (cpumask_test_cpu(dest_cpu, &p->cpus_allowed)) + if (is_cpu_allowed(p, dest_cpu)) return dest_cpu; } } for (;;) { /* Any allowed, online CPU? */ - for_each_cpu(dest_cpu, &p->cpus_allowed) { + for_each_cpu(dest_cpu, p->cpus_ptr) { if (!is_cpu_allowed(p, dest_cpu)) continue; @@ -1491,17 +3454,15 @@ static int select_fallback_rq(int cpu, struct task_struct *p) /* No more Mr. Nice Guy. */ switch (state) { case cpuset: - if (IS_ENABLED(CONFIG_CPUSETS)) { - cpuset_cpus_allowed_fallback(p); + if (cpuset_cpus_allowed_fallback(p)) { state = possible; break; } - /* Fall-through */ + fallthrough; case possible: - do_set_cpus_allowed(p, cpu_possible_mask); + set_cpus_allowed_force(p, task_cpu_fallback_mask(p)); state = fail; break; - case fail: BUG(); break; @@ -1525,21 +3486,23 @@ out: } /* - * The caller (fork, wakeup) owns p->pi_lock, ->cpus_allowed is stable. + * The caller (fork, wakeup) owns p->pi_lock, ->cpus_ptr is stable. */ static inline -int select_task_rq(struct task_struct *p, int cpu, int sd_flags, int wake_flags) +int select_task_rq(struct task_struct *p, int cpu, int *wake_flags) { lockdep_assert_held(&p->pi_lock); - if (p->nr_cpus_allowed > 1) - cpu = p->sched_class->select_task_rq(p, cpu, sd_flags, wake_flags); - else - cpu = cpumask_any(&p->cpus_allowed); + if (p->nr_cpus_allowed > 1 && !is_migration_disabled(p)) { + cpu = p->sched_class->select_task_rq(p, cpu, *wake_flags); + *wake_flags |= WF_RQ_SELECTED; + } else { + cpu = cpumask_any(p->cpus_ptr); + } /* * In order not to call set_task_cpu() on a blocking task we need - * to rely on ttwu() to place the task on a valid ->cpus_allowed + * to rely on ttwu() to place the task on a valid ->cpus_ptr * CPU. * * Since this is common to all placement strategies, this lives here. @@ -1553,14 +3516,9 @@ int select_task_rq(struct task_struct *p, int cpu, int sd_flags, int wake_flags) return cpu; } -static void update_avg(u64 *avg, u64 sample) -{ - s64 diff = sample - *avg; - *avg += diff >> 3; -} - void sched_set_stop_task(int cpu, struct task_struct *stop) { + static struct lock_class_key stop_pi_lock; struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 }; struct task_struct *old_stop = cpu_rq(cpu)->stop; @@ -1576,6 +3534,20 @@ void sched_set_stop_task(int cpu, struct task_struct *stop) sched_setscheduler_nocheck(stop, SCHED_FIFO, ¶m); stop->sched_class = &stop_sched_class; + + /* + * The PI code calls rt_mutex_setprio() with ->pi_lock held to + * adjust the effective priority of a task. As a result, + * rt_mutex_setprio() can trigger (RT) balancing operations, + * which can then trigger wakeups of the stop thread to push + * around the current task. + * + * The stop task itself will never be part of the PI-chain, it + * never blocks, therefore that ->pi_lock recursion is safe. + * Tell lockdep about this by placing the stop->pi_lock in its + * own class. + */ + lockdep_set_class(&stop->pi_lock, &stop_pi_lock); } cpu_rq(cpu)->stop = stop; @@ -1589,16 +3561,6 @@ void sched_set_stop_task(int cpu, struct task_struct *stop) } } -#else - -static inline int __set_cpus_allowed_ptr(struct task_struct *p, - const struct cpumask *new_mask, bool check) -{ - return set_cpus_allowed_ptr(p, new_mask); -} - -#endif /* CONFIG_SMP */ - static void ttwu_stat(struct task_struct *p, int cpu, int wake_flags) { @@ -1609,59 +3571,71 @@ ttwu_stat(struct task_struct *p, int cpu, int wake_flags) rq = this_rq(); -#ifdef CONFIG_SMP if (cpu == rq->cpu) { __schedstat_inc(rq->ttwu_local); - __schedstat_inc(p->se.statistics.nr_wakeups_local); + __schedstat_inc(p->stats.nr_wakeups_local); } else { struct sched_domain *sd; - __schedstat_inc(p->se.statistics.nr_wakeups_remote); - rcu_read_lock(); + __schedstat_inc(p->stats.nr_wakeups_remote); + + guard(rcu)(); for_each_domain(rq->cpu, sd) { if (cpumask_test_cpu(cpu, sched_domain_span(sd))) { __schedstat_inc(sd->ttwu_wake_remote); break; } } - rcu_read_unlock(); } if (wake_flags & WF_MIGRATED) - __schedstat_inc(p->se.statistics.nr_wakeups_migrate); -#endif /* CONFIG_SMP */ + __schedstat_inc(p->stats.nr_wakeups_migrate); __schedstat_inc(rq->ttwu_count); - __schedstat_inc(p->se.statistics.nr_wakeups); + __schedstat_inc(p->stats.nr_wakeups); if (wake_flags & WF_SYNC) - __schedstat_inc(p->se.statistics.nr_wakeups_sync); -} - -static inline void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags) -{ - activate_task(rq, p, en_flags); - p->on_rq = TASK_ON_RQ_QUEUED; - - /* If a worker is waking up, notify the workqueue: */ - if (p->flags & PF_WQ_WORKER) - wq_worker_waking_up(p, cpu_of(rq)); + __schedstat_inc(p->stats.nr_wakeups_sync); } /* - * Mark the task runnable and perform wakeup-preemption. + * Mark the task runnable. */ -static void ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags, - struct rq_flags *rf) +static inline void ttwu_do_wakeup(struct task_struct *p) { - check_preempt_curr(rq, p, wake_flags); - p->state = TASK_RUNNING; + WRITE_ONCE(p->__state, TASK_RUNNING); trace_sched_wakeup(p); +} + +static void +ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags, + struct rq_flags *rf) +{ + int en_flags = ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK; + + lockdep_assert_rq_held(rq); + + if (p->sched_contributes_to_load) + rq->nr_uninterruptible--; + + if (wake_flags & WF_RQ_SELECTED) + en_flags |= ENQUEUE_RQ_SELECTED; + if (wake_flags & WF_MIGRATED) + en_flags |= ENQUEUE_MIGRATED; + else + if (p->in_iowait) { + delayacct_blkio_end(p); + atomic_dec(&task_rq(p)->nr_iowait); + } + + activate_task(rq, p, en_flags); + wakeup_preempt(rq, p, wake_flags); + + ttwu_do_wakeup(p); -#ifdef CONFIG_SMP if (p->sched_class->task_woken) { /* - * Our task @p is fully woken up and running; so its safe to + * Our task @p is fully woken up and running; so it's safe to * drop the rq->lock, hereafter rq is only used for statistics. */ rq_unpin_lock(rq, rf); @@ -1680,36 +3654,34 @@ static void ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags, rq->idle_stamp = 0; } -#endif -} - -static void -ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags, - struct rq_flags *rf) -{ - int en_flags = ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK; - - lockdep_assert_held(&rq->lock); - -#ifdef CONFIG_SMP - if (p->sched_contributes_to_load) - rq->nr_uninterruptible--; - - if (wake_flags & WF_MIGRATED) - en_flags |= ENQUEUE_MIGRATED; -#endif - - ttwu_activate(rq, p, en_flags); - ttwu_do_wakeup(rq, p, wake_flags, rf); } /* - * Called in case the task @p isn't fully descheduled from its runqueue, - * in this case we must do a remote wakeup. Its a 'light' wakeup though, - * since all we need to do is flip p->state to TASK_RUNNING, since - * the task is still ->on_rq. + * Consider @p being inside a wait loop: + * + * for (;;) { + * set_current_state(TASK_UNINTERRUPTIBLE); + * + * if (CONDITION) + * break; + * + * schedule(); + * } + * __set_current_state(TASK_RUNNING); + * + * between set_current_state() and schedule(). In this case @p is still + * runnable, so all that needs doing is change p->state back to TASK_RUNNING in + * an atomic manner. + * + * By taking task_rq(p)->lock we serialize against schedule(), if @p->on_rq + * then schedule() must still happen and p->state can be changed to + * TASK_RUNNING. Otherwise we lost the race, schedule() has happened, and we + * need to do a full wakeup with enqueue. + * + * Returns: %true when the wakeup is done, + * %false otherwise. */ -static int ttwu_remote(struct task_struct *p, int wake_flags) +static int ttwu_runnable(struct task_struct *p, int wake_flags) { struct rq_flags rf; struct rq *rq; @@ -1717,21 +3689,28 @@ static int ttwu_remote(struct task_struct *p, int wake_flags) rq = __task_rq_lock(p, &rf); if (task_on_rq_queued(p)) { - /* check_preempt_curr() may use rq clock */ update_rq_clock(rq); - ttwu_do_wakeup(rq, p, wake_flags, &rf); + if (p->se.sched_delayed) + enqueue_task(rq, p, ENQUEUE_NOCLOCK | ENQUEUE_DELAYED); + if (!task_on_cpu(rq, p)) { + /* + * When on_rq && !on_cpu the task is preempted, see if + * it should preempt the task that is current now. + */ + wakeup_preempt(rq, p, wake_flags); + } + ttwu_do_wakeup(p); ret = 1; } - __task_rq_unlock(rq, &rf); + __task_rq_unlock(rq, p, &rf); return ret; } -#ifdef CONFIG_SMP -void sched_ttwu_pending(void) +void sched_ttwu_pending(void *arg) { + struct llist_node *llist = arg; struct rq *rq = this_rq(); - struct llist_node *llist = llist_del_all(&rq->wake_list); struct task_struct *p, *t; struct rq_flags rf; @@ -1741,106 +3720,174 @@ void sched_ttwu_pending(void) rq_lock_irqsave(rq, &rf); update_rq_clock(rq); - llist_for_each_entry_safe(p, t, llist, wake_entry) - ttwu_do_activate(rq, p, p->sched_remote_wakeup ? WF_MIGRATED : 0, &rf); - - rq_unlock_irqrestore(rq, &rf); -} + llist_for_each_entry_safe(p, t, llist, wake_entry.llist) { + if (WARN_ON_ONCE(p->on_cpu)) + smp_cond_load_acquire(&p->on_cpu, !VAL); -void scheduler_ipi(void) -{ - /* - * Fold TIF_NEED_RESCHED into the preempt_count; anybody setting - * TIF_NEED_RESCHED remotely (for the first time) will also send - * this IPI. - */ - preempt_fold_need_resched(); + if (WARN_ON_ONCE(task_cpu(p) != cpu_of(rq))) + set_task_cpu(p, cpu_of(rq)); - if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick()) - return; + ttwu_do_activate(rq, p, p->sched_remote_wakeup ? WF_MIGRATED : 0, &rf); + } /* - * Not all reschedule IPI handlers call irq_enter/irq_exit, since - * traditionally all their work was done from the interrupt return - * path. Now that we actually do some work, we need to make sure - * we do call them. - * - * Some archs already do call them, luckily irq_enter/exit nest - * properly. + * Must be after enqueueing at least once task such that + * idle_cpu() does not observe a false-negative -- if it does, + * it is possible for select_idle_siblings() to stack a number + * of tasks on this CPU during that window. * - * Arguably we should visit all archs and update all handlers, - * however a fair share of IPIs are still resched only so this would - * somewhat pessimize the simple resched case. + * It is OK to clear ttwu_pending when another task pending. + * We will receive IPI after local IRQ enabled and then enqueue it. + * Since now nr_running > 0, idle_cpu() will always get correct result. */ - irq_enter(); - sched_ttwu_pending(); + WRITE_ONCE(rq->ttwu_pending, 0); + rq_unlock_irqrestore(rq, &rf); +} - /* - * Check if someone kicked us for doing the nohz idle load balance. - */ - if (unlikely(got_nohz_idle_kick())) { - this_rq()->idle_balance = 1; - raise_softirq_irqoff(SCHED_SOFTIRQ); +/* + * Prepare the scene for sending an IPI for a remote smp_call + * + * Returns true if the caller can proceed with sending the IPI. + * Returns false otherwise. + */ +bool call_function_single_prep_ipi(int cpu) +{ + if (set_nr_if_polling(cpu_rq(cpu)->idle)) { + trace_sched_wake_idle_without_ipi(cpu); + return false; } - irq_exit(); + + return true; } -static void ttwu_queue_remote(struct task_struct *p, int cpu, int wake_flags) +/* + * Queue a task on the target CPUs wake_list and wake the CPU via IPI if + * necessary. The wakee CPU on receipt of the IPI will queue the task + * via sched_ttwu_wakeup() for activation so the wakee incurs the cost + * of the wakeup instead of the waker. + */ +static void __ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags) { struct rq *rq = cpu_rq(cpu); p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED); - if (llist_add(&p->wake_entry, &cpu_rq(cpu)->wake_list)) { - if (!set_nr_if_polling(rq->idle)) - smp_send_reschedule(cpu); - else - trace_sched_wake_idle_without_ipi(cpu); - } + WRITE_ONCE(rq->ttwu_pending, 1); +#ifdef CONFIG_SMP + __smp_call_single_queue(cpu, &p->wake_entry.llist); +#endif } void wake_up_if_idle(int cpu) { struct rq *rq = cpu_rq(cpu); - struct rq_flags rf; - - rcu_read_lock(); - if (!is_idle_task(rcu_dereference(rq->curr))) - goto out; - - if (set_nr_if_polling(rq->idle)) { - trace_sched_wake_idle_without_ipi(cpu); - } else { - rq_lock_irqsave(rq, &rf); + guard(rcu)(); + if (is_idle_task(rcu_dereference(rq->curr))) { + guard(rq_lock_irqsave)(rq); if (is_idle_task(rq->curr)) - smp_send_reschedule(cpu); - /* Else CPU is not idle, do nothing here: */ - rq_unlock_irqrestore(rq, &rf); + resched_curr(rq); } +} -out: - rcu_read_unlock(); +bool cpus_equal_capacity(int this_cpu, int that_cpu) +{ + if (!sched_asym_cpucap_active()) + return true; + + if (this_cpu == that_cpu) + return true; + + return arch_scale_cpu_capacity(this_cpu) == arch_scale_cpu_capacity(that_cpu); } bool cpus_share_cache(int this_cpu, int that_cpu) { + if (this_cpu == that_cpu) + return true; + return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu); } -#endif /* CONFIG_SMP */ + +/* + * Whether CPUs are share cache resources, which means LLC on non-cluster + * machines and LLC tag or L2 on machines with clusters. + */ +bool cpus_share_resources(int this_cpu, int that_cpu) +{ + if (this_cpu == that_cpu) + return true; + + return per_cpu(sd_share_id, this_cpu) == per_cpu(sd_share_id, that_cpu); +} + +static inline bool ttwu_queue_cond(struct task_struct *p, int cpu) +{ + /* See SCX_OPS_ALLOW_QUEUED_WAKEUP. */ + if (!scx_allow_ttwu_queue(p)) + return false; + +#ifdef CONFIG_SMP + if (p->sched_class == &stop_sched_class) + return false; +#endif + + /* + * Do not complicate things with the async wake_list while the CPU is + * in hotplug state. + */ + if (!cpu_active(cpu)) + return false; + + /* Ensure the task will still be allowed to run on the CPU. */ + if (!cpumask_test_cpu(cpu, p->cpus_ptr)) + return false; + + /* + * If the CPU does not share cache, then queue the task on the + * remote rqs wakelist to avoid accessing remote data. + */ + if (!cpus_share_cache(smp_processor_id(), cpu)) + return true; + + if (cpu == smp_processor_id()) + return false; + + /* + * If the wakee cpu is idle, or the task is descheduling and the + * only running task on the CPU, then use the wakelist to offload + * the task activation to the idle (or soon-to-be-idle) CPU as + * the current CPU is likely busy. nr_running is checked to + * avoid unnecessary task stacking. + * + * Note that we can only get here with (wakee) p->on_rq=0, + * p->on_cpu can be whatever, we've done the dequeue, so + * the wakee has been accounted out of ->nr_running. + */ + if (!cpu_rq(cpu)->nr_running) + return true; + + return false; +} + +static bool ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags) +{ + if (sched_feat(TTWU_QUEUE) && ttwu_queue_cond(p, cpu)) { + sched_clock_cpu(cpu); /* Sync clocks across CPUs */ + __ttwu_queue_wakelist(p, cpu, wake_flags); + return true; + } + + return false; +} static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags) { struct rq *rq = cpu_rq(cpu); struct rq_flags rf; -#if defined(CONFIG_SMP) - if (sched_feat(TTWU_QUEUE) && !cpus_share_cache(smp_processor_id(), cpu)) { - sched_clock_cpu(cpu); /* Sync clocks across CPUs */ - ttwu_queue_remote(p, cpu, wake_flags); + if (ttwu_queue_wakelist(p, cpu, wake_flags)) return; - } -#endif rq_lock(rq, &rf); update_rq_clock(rq); @@ -1849,6 +3896,56 @@ static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags) } /* + * Invoked from try_to_wake_up() to check whether the task can be woken up. + * + * The caller holds p::pi_lock if p != current or has preemption + * disabled when p == current. + * + * The rules of saved_state: + * + * The related locking code always holds p::pi_lock when updating + * p::saved_state, which means the code is fully serialized in both cases. + * + * For PREEMPT_RT, the lock wait and lock wakeups happen via TASK_RTLOCK_WAIT. + * No other bits set. This allows to distinguish all wakeup scenarios. + * + * For FREEZER, the wakeup happens via TASK_FROZEN. No other bits set. This + * allows us to prevent early wakeup of tasks before they can be run on + * asymmetric ISA architectures (eg ARMv9). + */ +static __always_inline +bool ttwu_state_match(struct task_struct *p, unsigned int state, int *success) +{ + int match; + + if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)) { + WARN_ON_ONCE((state & TASK_RTLOCK_WAIT) && + state != TASK_RTLOCK_WAIT); + } + + *success = !!(match = __task_state_match(p, state)); + + /* + * Saved state preserves the task state across blocking on + * an RT lock or TASK_FREEZABLE tasks. If the state matches, + * set p::saved_state to TASK_RUNNING, but do not wake the task + * because it waits for a lock wakeup or __thaw_task(). Also + * indicate success because from the regular waker's point of + * view this has succeeded. + * + * After acquiring the lock the task will restore p::__state + * from p::saved_state which ensures that the regular + * wakeup is not lost. The restore will also set + * p::saved_state to TASK_RUNNING so any further tests will + * not result in false positives vs. @success + */ + if (match < 0) + p->saved_state = TASK_RUNNING; + + return match > 0; +} + +/* * Notes on Program-Order guarantees on SMP systems. * * MIGRATION @@ -1896,8 +3993,8 @@ static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags) * migration. However the means are completely different as there is no lock * chain to provide order. Instead we do: * - * 1) smp_store_release(X->on_cpu, 0) - * 2) smp_cond_load_acquire(!X->on_cpu) + * 1) smp_store_release(X->on_cpu, 0) -- finish_task() + * 2) smp_cond_load_acquire(!X->on_cpu) -- try_to_wake_up() * * Example: * @@ -1937,180 +4034,303 @@ static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags) * @state: the mask of task states that can be woken * @wake_flags: wake modifier flags (WF_*) * - * If (@state & @p->state) @p->state = TASK_RUNNING. + * Conceptually does: + * + * If (@state & @p->state) @p->state = TASK_RUNNING. * * If the task was not queued/runnable, also place it back on a runqueue. * - * Atomic against schedule() which would dequeue a task, also see - * set_current_state(). + * This function is atomic against schedule() which would dequeue the task. + * + * It issues a full memory barrier before accessing @p->state, see the comment + * with set_current_state(). + * + * Uses p->pi_lock to serialize against concurrent wake-ups. + * + * Relies on p->pi_lock stabilizing: + * - p->sched_class + * - p->cpus_ptr + * - p->sched_task_group + * in order to do migration, see its use of select_task_rq()/set_task_cpu(). + * + * Tries really hard to only take one task_rq(p)->lock for performance. + * Takes rq->lock in: + * - ttwu_runnable() -- old rq, unavoidable, see comment there; + * - ttwu_queue() -- new rq, for enqueue of the task; + * - psi_ttwu_dequeue() -- much sadness :-( accounting will kill us. * - * This function executes a full memory barrier before accessing the task - * state; see set_current_state(). + * As a consequence we race really badly with just about everything. See the + * many memory barriers and their comments for details. * * Return: %true if @p->state changes (an actual wakeup was done), * %false otherwise. */ -static int -try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) +int try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) { - unsigned long flags; + guard(preempt)(); int cpu, success = 0; + wake_flags |= WF_TTWU; + + if (p == current) { + /* + * We're waking current, this means 'p->on_rq' and 'task_cpu(p) + * == smp_processor_id()'. Together this means we can special + * case the whole 'p->on_rq && ttwu_runnable()' case below + * without taking any locks. + * + * Specifically, given current runs ttwu() we must be before + * schedule()'s block_task(), as such this must not observe + * sched_delayed. + * + * In particular: + * - we rely on Program-Order guarantees for all the ordering, + * - we're serialized against set_special_state() by virtue of + * it disabling IRQs (this allows not taking ->pi_lock). + */ + WARN_ON_ONCE(p->se.sched_delayed); + if (!ttwu_state_match(p, state, &success)) + goto out; + + trace_sched_waking(p); + ttwu_do_wakeup(p); + goto out; + } + /* * If we are going to wake up a thread waiting for CONDITION we * need to ensure that CONDITION=1 done by the caller can not be - * reordered with p->state check below. This pairs with mb() in - * set_current_state() the waiting thread does. + * reordered with p->state check below. This pairs with smp_store_mb() + * in set_current_state() that the waiting thread does. */ - raw_spin_lock_irqsave(&p->pi_lock, flags); - smp_mb__after_spinlock(); - if (!(p->state & state)) - goto out; + scoped_guard (raw_spinlock_irqsave, &p->pi_lock) { + smp_mb__after_spinlock(); + if (!ttwu_state_match(p, state, &success)) + break; + + trace_sched_waking(p); + + /* + * Ensure we load p->on_rq _after_ p->state, otherwise it would + * be possible to, falsely, observe p->on_rq == 0 and get stuck + * in smp_cond_load_acquire() below. + * + * sched_ttwu_pending() try_to_wake_up() + * STORE p->on_rq = 1 LOAD p->state + * UNLOCK rq->lock + * + * __schedule() (switch to task 'p') + * LOCK rq->lock smp_rmb(); + * smp_mb__after_spinlock(); + * UNLOCK rq->lock + * + * [task p] + * STORE p->state = UNINTERRUPTIBLE LOAD p->on_rq + * + * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in + * __schedule(). See the comment for smp_mb__after_spinlock(). + * + * A similar smp_rmb() lives in __task_needs_rq_lock(). + */ + smp_rmb(); + if (READ_ONCE(p->on_rq) && ttwu_runnable(p, wake_flags)) + break; + + /* + * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be + * possible to, falsely, observe p->on_cpu == 0. + * + * One must be running (->on_cpu == 1) in order to remove oneself + * from the runqueue. + * + * __schedule() (switch to task 'p') try_to_wake_up() + * STORE p->on_cpu = 1 LOAD p->on_rq + * UNLOCK rq->lock + * + * __schedule() (put 'p' to sleep) + * LOCK rq->lock smp_rmb(); + * smp_mb__after_spinlock(); + * STORE p->on_rq = 0 LOAD p->on_cpu + * + * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in + * __schedule(). See the comment for smp_mb__after_spinlock(). + * + * Form a control-dep-acquire with p->on_rq == 0 above, to ensure + * schedule()'s block_task() has 'happened' and p will no longer + * care about it's own p->state. See the comment in __schedule(). + */ + smp_acquire__after_ctrl_dep(); + + /* + * We're doing the wakeup (@success == 1), they did a dequeue (p->on_rq + * == 0), which means we need to do an enqueue, change p->state to + * TASK_WAKING such that we can unlock p->pi_lock before doing the + * enqueue, such as ttwu_queue_wakelist(). + */ + WRITE_ONCE(p->__state, TASK_WAKING); + + /* + * If the owning (remote) CPU is still in the middle of schedule() with + * this task as prev, considering queueing p on the remote CPUs wake_list + * which potentially sends an IPI instead of spinning on p->on_cpu to + * let the waker make forward progress. This is safe because IRQs are + * disabled and the IPI will deliver after on_cpu is cleared. + * + * Ensure we load task_cpu(p) after p->on_cpu: + * + * set_task_cpu(p, cpu); + * STORE p->cpu = @cpu + * __schedule() (switch to task 'p') + * LOCK rq->lock + * smp_mb__after_spin_lock() smp_cond_load_acquire(&p->on_cpu) + * STORE p->on_cpu = 1 LOAD p->cpu + * + * to ensure we observe the correct CPU on which the task is currently + * scheduling. + */ + if (smp_load_acquire(&p->on_cpu) && + ttwu_queue_wakelist(p, task_cpu(p), wake_flags)) + break; + + /* + * If the owning (remote) CPU is still in the middle of schedule() with + * this task as prev, wait until it's done referencing the task. + * + * Pairs with the smp_store_release() in finish_task(). + * + * This ensures that tasks getting woken will be fully ordered against + * their previous state and preserve Program Order. + */ + smp_cond_load_acquire(&p->on_cpu, !VAL); + + cpu = select_task_rq(p, p->wake_cpu, &wake_flags); + if (task_cpu(p) != cpu) { + if (p->in_iowait) { + delayacct_blkio_end(p); + atomic_dec(&task_rq(p)->nr_iowait); + } + + wake_flags |= WF_MIGRATED; + psi_ttwu_dequeue(p); + set_task_cpu(p, cpu); + } - trace_sched_waking(p); + ttwu_queue(p, cpu, wake_flags); + } +out: + if (success) + ttwu_stat(p, task_cpu(p), wake_flags); + + return success; +} - /* We're going to change ->state: */ - success = 1; - cpu = task_cpu(p); +static bool __task_needs_rq_lock(struct task_struct *p) +{ + unsigned int state = READ_ONCE(p->__state); /* - * Ensure we load p->on_rq _after_ p->state, otherwise it would - * be possible to, falsely, observe p->on_rq == 0 and get stuck - * in smp_cond_load_acquire() below. - * - * sched_ttwu_pending() try_to_wake_up() - * STORE p->on_rq = 1 LOAD p->state - * UNLOCK rq->lock - * - * __schedule() (switch to task 'p') - * LOCK rq->lock smp_rmb(); - * smp_mb__after_spinlock(); - * UNLOCK rq->lock - * - * [task p] - * STORE p->state = UNINTERRUPTIBLE LOAD p->on_rq - * - * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in - * __schedule(). See the comment for smp_mb__after_spinlock(). + * Since pi->lock blocks try_to_wake_up(), we don't need rq->lock when + * the task is blocked. Make sure to check @state since ttwu() can drop + * locks at the end, see ttwu_queue_wakelist(). */ - smp_rmb(); - if (p->on_rq && ttwu_remote(p, wake_flags)) - goto stat; + if (state == TASK_RUNNING || state == TASK_WAKING) + return true; -#ifdef CONFIG_SMP /* - * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be - * possible to, falsely, observe p->on_cpu == 0. - * - * One must be running (->on_cpu == 1) in order to remove oneself - * from the runqueue. - * - * __schedule() (switch to task 'p') try_to_wake_up() - * STORE p->on_cpu = 1 LOAD p->on_rq - * UNLOCK rq->lock + * Ensure we load p->on_rq after p->__state, otherwise it would be + * possible to, falsely, observe p->on_rq == 0. * - * __schedule() (put 'p' to sleep) - * LOCK rq->lock smp_rmb(); - * smp_mb__after_spinlock(); - * STORE p->on_rq = 0 LOAD p->on_cpu - * - * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in - * __schedule(). See the comment for smp_mb__after_spinlock(). + * See try_to_wake_up() for a longer comment. */ smp_rmb(); + if (p->on_rq) + return true; /* - * If the owning (remote) CPU is still in the middle of schedule() with - * this task as prev, wait until its done referencing the task. - * - * Pairs with the smp_store_release() in finish_task(). - * - * This ensures that tasks getting woken will be fully ordered against - * their previous state and preserve Program Order. + * Ensure the task has finished __schedule() and will not be referenced + * anymore. Again, see try_to_wake_up() for a longer comment. */ + smp_rmb(); smp_cond_load_acquire(&p->on_cpu, !VAL); - p->sched_contributes_to_load = !!task_contributes_to_load(p); - p->state = TASK_WAKING; - - if (p->in_iowait) { - delayacct_blkio_end(p); - atomic_dec(&task_rq(p)->nr_iowait); - } + return false; +} - cpu = select_task_rq(p, p->wake_cpu, SD_BALANCE_WAKE, wake_flags); - if (task_cpu(p) != cpu) { - wake_flags |= WF_MIGRATED; - psi_ttwu_dequeue(p); - set_task_cpu(p, cpu); - } +/** + * task_call_func - Invoke a function on task in fixed state + * @p: Process for which the function is to be invoked, can be @current. + * @func: Function to invoke. + * @arg: Argument to function. + * + * Fix the task in it's current state by avoiding wakeups and or rq operations + * and call @func(@arg) on it. This function can use task_is_runnable() and + * task_curr() to work out what the state is, if required. Given that @func + * can be invoked with a runqueue lock held, it had better be quite + * lightweight. + * + * Returns: + * Whatever @func returns + */ +int task_call_func(struct task_struct *p, task_call_f func, void *arg) +{ + struct rq *rq = NULL; + struct rq_flags rf; + int ret; -#else /* CONFIG_SMP */ + raw_spin_lock_irqsave(&p->pi_lock, rf.flags); - if (p->in_iowait) { - delayacct_blkio_end(p); - atomic_dec(&task_rq(p)->nr_iowait); - } + if (__task_needs_rq_lock(p)) + rq = __task_rq_lock(p, &rf); -#endif /* CONFIG_SMP */ + /* + * At this point the task is pinned; either: + * - blocked and we're holding off wakeups (pi->lock) + * - woken, and we're holding off enqueue (rq->lock) + * - queued, and we're holding off schedule (rq->lock) + * - running, and we're holding off de-schedule (rq->lock) + * + * The called function (@func) can use: task_curr(), p->on_rq and + * p->__state to differentiate between these states. + */ + ret = func(p, arg); - ttwu_queue(p, cpu, wake_flags); -stat: - ttwu_stat(p, cpu, wake_flags); -out: - raw_spin_unlock_irqrestore(&p->pi_lock, flags); + if (rq) + __task_rq_unlock(rq, p, &rf); - return success; + raw_spin_unlock_irqrestore(&p->pi_lock, rf.flags); + return ret; } /** - * try_to_wake_up_local - try to wake up a local task with rq lock held - * @p: the thread to be awakened - * @rf: request-queue flags for pinning + * cpu_curr_snapshot - Return a snapshot of the currently running task + * @cpu: The CPU on which to snapshot the task. + * + * Returns the task_struct pointer of the task "currently" running on + * the specified CPU. + * + * If the specified CPU was offline, the return value is whatever it + * is, perhaps a pointer to the task_struct structure of that CPU's idle + * task, but there is no guarantee. Callers wishing a useful return + * value must take some action to ensure that the specified CPU remains + * online throughout. * - * Put @p on the run-queue if it's not already there. The caller must - * ensure that this_rq() is locked, @p is bound to this_rq() and not - * the current task. + * This function executes full memory barriers before and after fetching + * the pointer, which permits the caller to confine this function's fetch + * with respect to the caller's accesses to other shared variables. */ -static void try_to_wake_up_local(struct task_struct *p, struct rq_flags *rf) +struct task_struct *cpu_curr_snapshot(int cpu) { - struct rq *rq = task_rq(p); - - if (WARN_ON_ONCE(rq != this_rq()) || - WARN_ON_ONCE(p == current)) - return; - - lockdep_assert_held(&rq->lock); - - if (!raw_spin_trylock(&p->pi_lock)) { - /* - * This is OK, because current is on_cpu, which avoids it being - * picked for load-balance and preemption/IRQs are still - * disabled avoiding further scheduler activity on it and we've - * not yet picked a replacement task. - */ - rq_unlock(rq, rf); - raw_spin_lock(&p->pi_lock); - rq_relock(rq, rf); - } - - if (!(p->state & TASK_NORMAL)) - goto out; - - trace_sched_waking(p); + struct rq *rq = cpu_rq(cpu); + struct task_struct *t; + struct rq_flags rf; - if (!task_on_rq_queued(p)) { - if (p->in_iowait) { - delayacct_blkio_end(p); - atomic_dec(&rq->nr_iowait); - } - ttwu_activate(rq, p, ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK); - } + rq_lock_irqsave(rq, &rf); + smp_mb__after_spinlock(); /* Pairing determined by caller's synchronization design. */ + t = rcu_dereference(cpu_curr(cpu)); + rq_unlock_irqrestore(rq, &rf); + smp_mb(); /* Pairing determined by caller's synchronization design. */ - ttwu_do_wakeup(rq, p, 0, rf); - ttwu_stat(p, smp_processor_id(), 0); -out: - raw_spin_unlock(&p->pi_lock); + return t; } /** @@ -2139,9 +4359,10 @@ int wake_up_state(struct task_struct *p, unsigned int state) * Perform scheduler related setup for a newly forked process p. * p is forked by current. * - * __sched_fork() is basic setup used by init_idle() too: + * __sched_fork() is basic setup which is also used by sched_init() to + * initialize the boot CPU's idle task. */ -static void __sched_fork(unsigned long clone_flags, struct task_struct *p) +static void __sched_fork(u64 clone_flags, struct task_struct *p) { p->on_rq = 0; @@ -2151,21 +4372,25 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p) p->se.prev_sum_exec_runtime = 0; p->se.nr_migrations = 0; p->se.vruntime = 0; + p->se.vlag = 0; INIT_LIST_HEAD(&p->se.group_node); + /* A delayed task cannot be in clone(). */ + WARN_ON_ONCE(p->se.sched_delayed); + #ifdef CONFIG_FAIR_GROUP_SCHED p->se.cfs_rq = NULL; +#ifdef CONFIG_CFS_BANDWIDTH + init_cfs_throttle_work(p); +#endif #endif #ifdef CONFIG_SCHEDSTATS /* Even if schedstat is disabled, there should not be garbage */ - memset(&p->se.statistics, 0, sizeof(p->se.statistics)); + memset(&p->stats, 0, sizeof(p->stats)); #endif - RB_CLEAR_NODE(&p->dl.rb_node); - init_dl_task_timer(&p->dl); - init_dl_inactive_task_timer(&p->dl); - __dl_clear_params(p); + init_dl_entity(&p->dl); INIT_LIST_HEAD(&p->rt.run_list); p->rt.timeout = 0; @@ -2173,18 +4398,29 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p) p->rt.on_rq = 0; p->rt.on_list = 0; +#ifdef CONFIG_SCHED_CLASS_EXT + init_scx_entity(&p->scx); +#endif + #ifdef CONFIG_PREEMPT_NOTIFIERS INIT_HLIST_HEAD(&p->preempt_notifiers); #endif +#ifdef CONFIG_COMPACTION + p->capture_control = NULL; +#endif init_numa_balancing(clone_flags, p); + p->wake_entry.u_flags = CSD_TYPE_TTWU; + p->migration_pending = NULL; } DEFINE_STATIC_KEY_FALSE(sched_numa_balancing); #ifdef CONFIG_NUMA_BALANCING -void set_numabalancing_state(bool enabled) +int sysctl_numa_balancing_mode; + +static void __set_numabalancing_state(bool enabled) { if (enabled) static_branch_enable(&sched_numa_balancing); @@ -2192,13 +4428,33 @@ void set_numabalancing_state(bool enabled) static_branch_disable(&sched_numa_balancing); } +void set_numabalancing_state(bool enabled) +{ + if (enabled) + sysctl_numa_balancing_mode = NUMA_BALANCING_NORMAL; + else + sysctl_numa_balancing_mode = NUMA_BALANCING_DISABLED; + __set_numabalancing_state(enabled); +} + #ifdef CONFIG_PROC_SYSCTL -int sysctl_numa_balancing(struct ctl_table *table, int write, - void __user *buffer, size_t *lenp, loff_t *ppos) +static void reset_memory_tiering(void) +{ + struct pglist_data *pgdat; + + for_each_online_pgdat(pgdat) { + pgdat->nbp_threshold = 0; + pgdat->nbp_th_nr_cand = node_page_state(pgdat, PGPROMOTE_CANDIDATE); + pgdat->nbp_th_start = jiffies_to_msecs(jiffies); + } +} + +static int sysctl_numa_balancing(const struct ctl_table *table, int write, + void *buffer, size_t *lenp, loff_t *ppos) { struct ctl_table t; int err; - int state = static_branch_likely(&sched_numa_balancing); + int state = sysctl_numa_balancing_mode; if (write && !capable(CAP_SYS_ADMIN)) return -EPERM; @@ -2208,17 +4464,21 @@ int sysctl_numa_balancing(struct ctl_table *table, int write, err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); if (err < 0) return err; - if (write) - set_numabalancing_state(state); + if (write) { + if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) && + (state & NUMA_BALANCING_MEMORY_TIERING)) + reset_memory_tiering(); + sysctl_numa_balancing_mode = state; + __set_numabalancing_state(state); + } return err; } -#endif -#endif +#endif /* CONFIG_PROC_SYSCTL */ +#endif /* CONFIG_NUMA_BALANCING */ #ifdef CONFIG_SCHEDSTATS DEFINE_STATIC_KEY_FALSE(sched_schedstats); -static bool __initdata __sched_schedstats = false; static void set_schedstats(bool enabled) { @@ -2242,16 +4502,11 @@ static int __init setup_schedstats(char *str) if (!str) goto out; - /* - * This code is called before jump labels have been set up, so we can't - * change the static branch directly just yet. Instead set a temporary - * variable so init_schedstats() can do it later. - */ if (!strcmp(str, "enable")) { - __sched_schedstats = true; + set_schedstats(true); ret = 1; } else if (!strcmp(str, "disable")) { - __sched_schedstats = false; + set_schedstats(false); ret = 1; } out: @@ -2262,14 +4517,9 @@ out: } __setup("schedstats=", setup_schedstats); -static void __init init_schedstats(void) -{ - set_schedstats(__sched_schedstats); -} - #ifdef CONFIG_PROC_SYSCTL -int sysctl_schedstats(struct ctl_table *table, int write, - void __user *buffer, size_t *lenp, loff_t *ppos) +static int sysctl_schedstats(const struct ctl_table *table, int write, void *buffer, + size_t *lenp, loff_t *ppos) { struct ctl_table t; int err; @@ -2288,30 +4538,84 @@ int sysctl_schedstats(struct ctl_table *table, int write, return err; } #endif /* CONFIG_PROC_SYSCTL */ -#else /* !CONFIG_SCHEDSTATS */ -static inline void init_schedstats(void) {} #endif /* CONFIG_SCHEDSTATS */ +#ifdef CONFIG_SYSCTL +static const struct ctl_table sched_core_sysctls[] = { +#ifdef CONFIG_SCHEDSTATS + { + .procname = "sched_schedstats", + .data = NULL, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = sysctl_schedstats, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }, +#endif /* CONFIG_SCHEDSTATS */ +#ifdef CONFIG_UCLAMP_TASK + { + .procname = "sched_util_clamp_min", + .data = &sysctl_sched_uclamp_util_min, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = sysctl_sched_uclamp_handler, + }, + { + .procname = "sched_util_clamp_max", + .data = &sysctl_sched_uclamp_util_max, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = sysctl_sched_uclamp_handler, + }, + { + .procname = "sched_util_clamp_min_rt_default", + .data = &sysctl_sched_uclamp_util_min_rt_default, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = sysctl_sched_uclamp_handler, + }, +#endif /* CONFIG_UCLAMP_TASK */ +#ifdef CONFIG_NUMA_BALANCING + { + .procname = "numa_balancing", + .data = NULL, /* filled in by handler */ + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = sysctl_numa_balancing, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_FOUR, + }, +#endif /* CONFIG_NUMA_BALANCING */ +}; +static int __init sched_core_sysctl_init(void) +{ + register_sysctl_init("kernel", sched_core_sysctls); + return 0; +} +late_initcall(sched_core_sysctl_init); +#endif /* CONFIG_SYSCTL */ + /* * fork()/clone()-time setup: */ -int sched_fork(unsigned long clone_flags, struct task_struct *p) +int sched_fork(u64 clone_flags, struct task_struct *p) { - unsigned long flags; - __sched_fork(clone_flags, p); /* * We mark the process as NEW here. This guarantees that * nobody will actually run it, and a signal or other external * event cannot wake it up and insert it on the runqueue either. */ - p->state = TASK_NEW; + p->__state = TASK_NEW; /* * Make sure we do not leak PI boosting priority to the child. */ p->prio = current->normal_prio; + uclamp_fork(p); + /* * Revert to default priority/policy on fork if requested. */ @@ -2323,8 +4627,10 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p) } else if (PRIO_TO_NICE(p->static_prio) < 0) p->static_prio = NICE_TO_PRIO(0); - p->prio = p->normal_prio = __normal_prio(p); + p->prio = p->normal_prio = p->static_prio; set_load_weight(p, false); + p->se.custom_slice = 0; + p->se.slice = sysctl_sched_base_slice; /* * We don't need the reset flag anymore after the fork. It has @@ -2335,21 +4641,52 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p) if (dl_prio(p->prio)) return -EAGAIN; - else if (rt_prio(p->prio)) + + scx_pre_fork(p); + + if (rt_prio(p->prio)) { p->sched_class = &rt_sched_class; - else +#ifdef CONFIG_SCHED_CLASS_EXT + } else if (task_should_scx(p->policy)) { + p->sched_class = &ext_sched_class; +#endif + } else { p->sched_class = &fair_sched_class; + } init_entity_runnable_average(&p->se); + +#ifdef CONFIG_SCHED_INFO + if (likely(sched_info_on())) + memset(&p->sched_info, 0, sizeof(p->sched_info)); +#endif + p->on_cpu = 0; + init_task_preempt_count(p); + plist_node_init(&p->pushable_tasks, MAX_PRIO); + RB_CLEAR_NODE(&p->pushable_dl_tasks); + + return 0; +} + +int sched_cgroup_fork(struct task_struct *p, struct kernel_clone_args *kargs) +{ + unsigned long flags; + /* - * The child is not yet in the pid-hash so no cgroup attach races, - * and the cgroup is pinned to this child due to cgroup_fork() - * is ran before sched_fork(). - * - * Silence PROVE_RCU. + * Because we're not yet on the pid-hash, p->pi_lock isn't strictly + * required yet, but lockdep gets upset if rules are violated. */ raw_spin_lock_irqsave(&p->pi_lock, flags); +#ifdef CONFIG_CGROUP_SCHED + if (1) { + struct task_group *tg; + tg = container_of(kargs->cset->subsys[cpu_cgrp_id], + struct task_group, css); + tg = autogroup_task_group(p, tg); + p->sched_task_group = tg; + } +#endif /* * We're setting the CPU for the first time, we don't migrate, * so use __set_task_cpu(). @@ -2359,19 +4696,18 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p) p->sched_class->task_fork(p); raw_spin_unlock_irqrestore(&p->pi_lock, flags); -#ifdef CONFIG_SCHED_INFO - if (likely(sched_info_on())) - memset(&p->sched_info, 0, sizeof(p->sched_info)); -#endif -#if defined(CONFIG_SMP) - p->on_cpu = 0; -#endif - init_task_preempt_count(p); -#ifdef CONFIG_SMP - plist_node_init(&p->pushable_tasks, MAX_PRIO); - RB_CLEAR_NODE(&p->pushable_dl_tasks); -#endif - return 0; + return scx_fork(p); +} + +void sched_cancel_fork(struct task_struct *p) +{ + scx_cancel_fork(p); +} + +void sched_post_fork(struct task_struct *p) +{ + uclamp_post_fork(p); + scx_post_fork(p); } unsigned long to_ratio(u64 period, u64 runtime) @@ -2401,40 +4737,36 @@ void wake_up_new_task(struct task_struct *p) { struct rq_flags rf; struct rq *rq; + int wake_flags = WF_FORK; raw_spin_lock_irqsave(&p->pi_lock, rf.flags); - p->state = TASK_RUNNING; -#ifdef CONFIG_SMP + WRITE_ONCE(p->__state, TASK_RUNNING); /* * Fork balancing, do it here and not earlier because: - * - cpus_allowed can change in the fork path + * - cpus_ptr can change in the fork path * - any previously selected CPU might disappear through hotplug * * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq, * as we're not fully set-up yet. */ p->recent_used_cpu = task_cpu(p); - __set_task_cpu(p, select_task_rq(p, task_cpu(p), SD_BALANCE_FORK, 0)); -#endif + __set_task_cpu(p, select_task_rq(p, task_cpu(p), &wake_flags)); rq = __task_rq_lock(p, &rf); update_rq_clock(rq); - post_init_entity_util_avg(&p->se); + post_init_entity_util_avg(p); - activate_task(rq, p, ENQUEUE_NOCLOCK); - p->on_rq = TASK_ON_RQ_QUEUED; + activate_task(rq, p, ENQUEUE_NOCLOCK | ENQUEUE_INITIAL); trace_sched_wakeup_new(p); - check_preempt_curr(rq, p, WF_FORK); -#ifdef CONFIG_SMP + wakeup_preempt(rq, p, wake_flags); if (p->sched_class->task_woken) { /* - * Nothing relies on rq->lock after this, so its fine to + * Nothing relies on rq->lock after this, so it's fine to * drop it. */ rq_unpin_lock(rq, &rf); p->sched_class->task_woken(rq, p); rq_repin_lock(rq, &rf); } -#endif task_rq_unlock(rq, p, &rf); } @@ -2511,7 +4843,7 @@ fire_sched_out_preempt_notifiers(struct task_struct *curr, __fire_sched_out_preempt_notifiers(curr, next); } -#else /* !CONFIG_PREEMPT_NOTIFIERS */ +#else /* !CONFIG_PREEMPT_NOTIFIERS: */ static inline void fire_sched_in_preempt_notifiers(struct task_struct *curr) { @@ -2523,25 +4855,26 @@ fire_sched_out_preempt_notifiers(struct task_struct *curr, { } -#endif /* CONFIG_PREEMPT_NOTIFIERS */ +#endif /* !CONFIG_PREEMPT_NOTIFIERS */ static inline void prepare_task(struct task_struct *next) { -#ifdef CONFIG_SMP /* * Claim the task as running, we do this before switching to it * such that any running task will have this set. + * + * See the smp_load_acquire(&p->on_cpu) case in ttwu() and + * its ordering comment. */ - next->on_cpu = 1; -#endif + WRITE_ONCE(next->on_cpu, 1); } static inline void finish_task(struct task_struct *prev) { -#ifdef CONFIG_SMP /* - * After ->on_cpu is cleared, the task can be moved to a different CPU. - * We must ensure this doesn't happen until the switch is completely + * This must be the very last reference to @prev from this CPU. After + * p->on_cpu is cleared, the task can be moved to a different CPU. We + * must ensure this doesn't happen until the switch is completely * finished. * * In particular, the load of prev->state in finish_task_switch() must @@ -2550,7 +4883,87 @@ static inline void finish_task(struct task_struct *prev) * Pairs with the smp_cond_load_acquire() in try_to_wake_up(). */ smp_store_release(&prev->on_cpu, 0); -#endif +} + +static void do_balance_callbacks(struct rq *rq, struct balance_callback *head) +{ + void (*func)(struct rq *rq); + struct balance_callback *next; + + lockdep_assert_rq_held(rq); + + while (head) { + func = (void (*)(struct rq *))head->func; + next = head->next; + head->next = NULL; + head = next; + + func(rq); + } +} + +static void balance_push(struct rq *rq); + +/* + * balance_push_callback is a right abuse of the callback interface and plays + * by significantly different rules. + * + * Where the normal balance_callback's purpose is to be ran in the same context + * that queued it (only later, when it's safe to drop rq->lock again), + * balance_push_callback is specifically targeted at __schedule(). + * + * This abuse is tolerated because it places all the unlikely/odd cases behind + * a single test, namely: rq->balance_callback == NULL. + */ +struct balance_callback balance_push_callback = { + .next = NULL, + .func = balance_push, +}; + +static inline struct balance_callback * +__splice_balance_callbacks(struct rq *rq, bool split) +{ + struct balance_callback *head = rq->balance_callback; + + if (likely(!head)) + return NULL; + + lockdep_assert_rq_held(rq); + /* + * Must not take balance_push_callback off the list when + * splice_balance_callbacks() and balance_callbacks() are not + * in the same rq->lock section. + * + * In that case it would be possible for __schedule() to interleave + * and observe the list empty. + */ + if (split && head == &balance_push_callback) + head = NULL; + else + rq->balance_callback = NULL; + + return head; +} + +struct balance_callback *splice_balance_callbacks(struct rq *rq) +{ + return __splice_balance_callbacks(rq, true); +} + +static void __balance_callbacks(struct rq *rq) +{ + do_balance_callbacks(rq, __splice_balance_callbacks(rq, false)); +} + +void balance_callbacks(struct rq *rq, struct balance_callback *head) +{ + unsigned long flags; + + if (unlikely(head)) { + raw_spin_rq_lock_irqsave(rq, flags); + do_balance_callbacks(rq, head); + raw_spin_rq_unlock_irqrestore(rq, flags); + } } static inline void @@ -2563,10 +4976,10 @@ prepare_lock_switch(struct rq *rq, struct task_struct *next, struct rq_flags *rf * do an early lockdep release here: */ rq_unpin_lock(rq, rf); - spin_release(&rq->lock.dep_map, 1, _THIS_IP_); + spin_release(&__rq_lockp(rq)->dep_map, _THIS_IP_); #ifdef CONFIG_DEBUG_SPINLOCK /* this is a valid case when another task releases the spinlock */ - rq->lock.owner = next; + rq_lockp(rq)->owner = next; #endif } @@ -2577,8 +4990,9 @@ static inline void finish_lock_switch(struct rq *rq) * fix up the runqueue lock - which gets 'carried over' from * prev into current: */ - spin_acquire(&rq->lock.dep_map, 0, 0, _THIS_IP_); - raw_spin_unlock_irq(&rq->lock); + spin_acquire(&__rq_lockp(rq)->dep_map, 0, 0, _THIS_IP_); + __balance_callbacks(rq); + raw_spin_rq_unlock_irq(rq); } /* @@ -2593,6 +5007,22 @@ static inline void finish_lock_switch(struct rq *rq) # define finish_arch_post_lock_switch() do { } while (0) #endif +static inline void kmap_local_sched_out(void) +{ +#ifdef CONFIG_KMAP_LOCAL + if (unlikely(current->kmap_ctrl.idx)) + __kmap_local_sched_out(); +#endif +} + +static inline void kmap_local_sched_in(void) +{ +#ifdef CONFIG_KMAP_LOCAL + if (unlikely(current->kmap_ctrl.idx)) + __kmap_local_sched_in(); +#endif +} + /** * prepare_task_switch - prepare to switch tasks * @rq: the runqueue preparing to switch @@ -2613,8 +5043,8 @@ prepare_task_switch(struct rq *rq, struct task_struct *prev, kcov_prepare_switch(prev); sched_info_switch(rq, prev, next); perf_event_task_sched_out(prev, next); - rseq_preempt(prev); fire_sched_out_preempt_notifiers(prev, next); + kmap_local_sched_out(); prepare_task(next); prepare_arch_switch(next); } @@ -2635,7 +5065,7 @@ prepare_task_switch(struct rq *rq, struct task_struct *prev, * * The context switch have flipped the stack from under us and restored the * local variables which were saved when this task called schedule() in the - * past. prev == current is still correct but we need to recalculate this_rq + * past. 'prev == current' is still correct but we need to recalculate this_rq * because prev may have moved to another CPU. */ static struct rq *finish_task_switch(struct task_struct *prev) @@ -2643,7 +5073,7 @@ static struct rq *finish_task_switch(struct task_struct *prev) { struct rq *rq = this_rq(); struct mm_struct *mm = rq->prev_mm; - long prev_state; + unsigned int prev_state; /* * The previous task will have left us with a preempt_count of 2 @@ -2674,13 +5104,22 @@ static struct rq *finish_task_switch(struct task_struct *prev) * running on another CPU and we could rave with its RUNNING -> DEAD * transition, resulting in a double drop. */ - prev_state = prev->state; + prev_state = READ_ONCE(prev->__state); vtime_task_switch(prev); perf_event_task_sched_in(prev, current); finish_task(prev); + tick_nohz_task_switch(); finish_lock_switch(rq); finish_arch_post_lock_switch(); kcov_finish_switch(current); + /* + * kmap_local_sched_out() is invoked with rq::lock held and + * interrupts disabled. There is no requirement for that, but the + * sched out code does not have an interrupt enabled section. + * Restoring the maps on sched in does not require interrupts being + * disabled either. + */ + kmap_local_sched_in(); fire_sched_in_preempt_notifiers(current); /* @@ -2692,70 +5131,35 @@ static struct rq *finish_task_switch(struct task_struct *prev) * rq->curr, before returning to userspace, so provide them here: * * - a full memory barrier for {PRIVATE,GLOBAL}_EXPEDITED, implicitly - * provided by mmdrop(), + * provided by mmdrop_lazy_tlb(), * - a sync_core for SYNC_CORE. */ if (mm) { membarrier_mm_sync_core_before_usermode(mm); - mmdrop(mm); + mmdrop_lazy_tlb_sched(mm); } + if (unlikely(prev_state == TASK_DEAD)) { if (prev->sched_class->task_dead) prev->sched_class->task_dead(prev); /* - * Remove function-return probe instances associated with this - * task and put them back on the free list. + * sched_ext_dead() must come before cgroup_task_dead() to + * prevent cgroups from being removed while its member tasks are + * visible to SCX schedulers. */ - kprobe_flush_task(prev); + sched_ext_dead(prev); + cgroup_task_dead(prev); /* Task is done with its stack. */ put_task_stack(prev); - put_task_struct(prev); + put_task_struct_rcu_user(prev); } - tick_nohz_task_switch(); return rq; } -#ifdef CONFIG_SMP - -/* rq->lock is NOT held, but preemption is disabled */ -static void __balance_callback(struct rq *rq) -{ - struct callback_head *head, *next; - void (*func)(struct rq *rq); - unsigned long flags; - - raw_spin_lock_irqsave(&rq->lock, flags); - head = rq->balance_callback; - rq->balance_callback = NULL; - while (head) { - func = (void (*)(struct rq *))head->func; - next = head->next; - head->next = NULL; - head = next; - - func(rq); - } - raw_spin_unlock_irqrestore(&rq->lock, flags); -} - -static inline void balance_callback(struct rq *rq) -{ - if (unlikely(rq->balance_callback)) - __balance_callback(rq); -} - -#else - -static inline void balance_callback(struct rq *rq) -{ -} - -#endif - /** * schedule_tail - first thing a freshly forked thread must call. * @prev: the thread we just switched away from. @@ -2763,8 +5167,6 @@ static inline void balance_callback(struct rq *rq) asmlinkage __visible void schedule_tail(struct task_struct *prev) __releases(rq->lock) { - struct rq *rq; - /* * New tasks start with FORK_PREEMPT_COUNT, see there and * finish_task_switch() for details. @@ -2774,8 +5176,13 @@ asmlinkage __visible void schedule_tail(struct task_struct *prev) * PREEMPT_COUNT kernels). */ - rq = finish_task_switch(prev); - balance_callback(rq); + finish_task_switch(prev); + /* + * This is a special case: the newly created task has just + * switched the context for the first time. It is returning from + * schedule for the first time in this path. + */ + trace_sched_exit_tp(true); preempt_enable(); if (current->set_child_tid) @@ -2791,12 +5198,8 @@ static __always_inline struct rq * context_switch(struct rq *rq, struct task_struct *prev, struct task_struct *next, struct rq_flags *rf) { - struct mm_struct *mm, *oldmm; - prepare_task_switch(rq, prev, next); - mm = next->mm; - oldmm = prev->active_mm; /* * For paravirt, this is coupled with an exit in switch_to to * combine the page table reload and the switch backend into @@ -2805,25 +5208,47 @@ context_switch(struct rq *rq, struct task_struct *prev, arch_start_context_switch(prev); /* - * If mm is non-NULL, we pass through switch_mm(). If mm is - * NULL, we will pass through mmdrop() in finish_task_switch(). - * Both of these contain the full memory barrier required by - * membarrier after storing to rq->curr, before returning to - * user-space. + * kernel -> kernel lazy + transfer active + * user -> kernel lazy + mmgrab_lazy_tlb() active + * + * kernel -> user switch + mmdrop_lazy_tlb() active + * user -> user switch */ - if (!mm) { - next->active_mm = oldmm; - mmgrab(oldmm); - enter_lazy_tlb(oldmm, next); - } else - switch_mm_irqs_off(oldmm, mm, next); + if (!next->mm) { // to kernel + enter_lazy_tlb(prev->active_mm, next); - if (!prev->mm) { - prev->active_mm = NULL; - rq->prev_mm = oldmm; + next->active_mm = prev->active_mm; + if (prev->mm) // from user + mmgrab_lazy_tlb(prev->active_mm); + else + prev->active_mm = NULL; + } else { // to user + membarrier_switch_mm(rq, prev->active_mm, next->mm); + /* + * sys_membarrier() requires an smp_mb() between setting + * rq->curr / membarrier_switch_mm() and returning to userspace. + * + * The below provides this either through switch_mm(), or in + * case 'prev->active_mm == next->mm' through + * finish_task_switch()'s mmdrop(). + */ + switch_mm_irqs_off(prev->active_mm, next->mm, next); + lru_gen_use_mm(next->mm); + + if (!prev->mm) { // from kernel + /* will mmdrop_lazy_tlb() in finish_task_switch(). */ + rq->prev_mm = prev->active_mm; + prev->active_mm = NULL; + } } - rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP); + mm_cid_switch_to(prev, next); + + /* + * Tell rseq that the task was scheduled in. Must be after + * switch_mm_cid() to get the TIF flag set. + */ + rseq_sched_switch_event(next); prepare_lock_switch(rq, next, rf); @@ -2840,9 +5265,9 @@ context_switch(struct rq *rq, struct task_struct *prev, * externally visible scheduler statistics: current number of runnable * threads, total number of context switches performed since bootup. */ -unsigned long nr_running(void) +unsigned int nr_running(void) { - unsigned long i, sum = 0; + unsigned int i, sum = 0; for_each_online_cpu(i) sum += cpu_rq(i)->nr_running; @@ -2869,6 +5294,11 @@ bool single_task_running(void) } EXPORT_SYMBOL(single_task_running); +unsigned long long nr_context_switches_cpu(int cpu) +{ + return cpu_rq(cpu)->nr_switches; +} + unsigned long long nr_context_switches(void) { int i; @@ -2887,13 +5317,13 @@ unsigned long long nr_context_switches(void) * it does become runnable. */ -unsigned long nr_iowait_cpu(int cpu) +unsigned int nr_iowait_cpu(int cpu) { return atomic_read(&cpu_rq(cpu)->nr_iowait); } /* - * IO-wait accounting, and how its mostly bollocks (on SMP). + * IO-wait accounting, and how it's mostly bollocks (on SMP). * * The idea behind IO-wait account is to account the idle time that we could * have spend running if it were not for IO. That is, if we were to improve the @@ -2922,9 +5352,9 @@ unsigned long nr_iowait_cpu(int cpu) * Task CPU affinities can make all that even more 'interesting'. */ -unsigned long nr_iowait(void) +unsigned int nr_iowait(void) { - unsigned long i, sum = 0; + unsigned int i, sum = 0; for_each_possible_cpu(i) sum += nr_iowait_cpu(i); @@ -2932,8 +5362,6 @@ unsigned long nr_iowait(void) return sum; } -#ifdef CONFIG_SMP - /* * sched_exec - execve() is a valuable balancing opportunity, because at * this point the task has the smallest effective memory and cache footprint. @@ -2941,27 +5369,22 @@ unsigned long nr_iowait(void) void sched_exec(void) { struct task_struct *p = current; - unsigned long flags; + struct migration_arg arg; int dest_cpu; - raw_spin_lock_irqsave(&p->pi_lock, flags); - dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), SD_BALANCE_EXEC, 0); - if (dest_cpu == smp_processor_id()) - goto unlock; + scoped_guard (raw_spinlock_irqsave, &p->pi_lock) { + dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), WF_EXEC); + if (dest_cpu == smp_processor_id()) + return; - if (likely(cpu_active(dest_cpu))) { - struct migration_arg arg = { p, dest_cpu }; + if (unlikely(!cpu_active(dest_cpu))) + return; - raw_spin_unlock_irqrestore(&p->pi_lock, flags); - stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg); - return; + arg = (struct migration_arg){ p, dest_cpu }; } -unlock: - raw_spin_unlock_irqrestore(&p->pi_lock, flags); + stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg); } -#endif - DEFINE_PER_CPU(struct kernel_stat, kstat); DEFINE_PER_CPU(struct kernel_cpustat, kernel_cpustat); @@ -2977,9 +5400,9 @@ EXPORT_PER_CPU_SYMBOL(kernel_cpustat); static inline void prefetch_curr_exec_start(struct task_struct *p) { #ifdef CONFIG_FAIR_GROUP_SCHED - struct sched_entity *curr = (&p->se)->cfs_rq->curr; + struct sched_entity *curr = p->se.cfs_rq->curr; #else - struct sched_entity *curr = (&task_rq(p)->cfs)->curr; + struct sched_entity *curr = task_rq(p)->cfs.curr; #endif prefetch(curr); prefetch(&curr->exec_start); @@ -2996,11 +5419,11 @@ unsigned long long task_sched_runtime(struct task_struct *p) struct rq *rq; u64 ns; -#if defined(CONFIG_64BIT) && defined(CONFIG_SMP) +#ifdef CONFIG_64BIT /* * 64-bit doesn't need locks to atomically read a 64-bit value. * So we have a optimization chance when the task's delta_exec is 0. - * Reading ->on_cpu is racy, but this is ok. + * Reading ->on_cpu is racy, but this is OK. * * If we race with it leaving CPU, we'll take a lock. So we're correct. * If we race with it entering CPU, unaccounted time is 0. This is @@ -3018,7 +5441,7 @@ unsigned long long task_sched_runtime(struct task_struct *p) * project cycles that may never be accounted to this * thread, breaking clock_gettime(). */ - if (task_current(rq, p) && task_on_rq_queued(p)) { + if (task_current_donor(rq, p) && task_on_rq_queued(p)) { prefetch_curr_exec_start(p); update_rq_clock(rq); p->sched_class->update_curr(rq); @@ -3029,43 +5452,139 @@ unsigned long long task_sched_runtime(struct task_struct *p) return ns; } +static u64 cpu_resched_latency(struct rq *rq) +{ + int latency_warn_ms = READ_ONCE(sysctl_resched_latency_warn_ms); + u64 resched_latency, now = rq_clock(rq); + static bool warned_once; + + if (sysctl_resched_latency_warn_once && warned_once) + return 0; + + if (!need_resched() || !latency_warn_ms) + return 0; + + if (system_state == SYSTEM_BOOTING) + return 0; + + if (!rq->last_seen_need_resched_ns) { + rq->last_seen_need_resched_ns = now; + rq->ticks_without_resched = 0; + return 0; + } + + rq->ticks_without_resched++; + resched_latency = now - rq->last_seen_need_resched_ns; + if (resched_latency <= latency_warn_ms * NSEC_PER_MSEC) + return 0; + + warned_once = true; + + return resched_latency; +} + +static int __init setup_resched_latency_warn_ms(char *str) +{ + long val; + + if ((kstrtol(str, 0, &val))) { + pr_warn("Unable to set resched_latency_warn_ms\n"); + return 1; + } + + sysctl_resched_latency_warn_ms = val; + return 1; +} +__setup("resched_latency_warn_ms=", setup_resched_latency_warn_ms); + /* * This function gets called by the timer code, with HZ frequency. * We call it with interrupts disabled. */ -void scheduler_tick(void) +void sched_tick(void) { int cpu = smp_processor_id(); struct rq *rq = cpu_rq(cpu); - struct task_struct *curr = rq->curr; + /* accounting goes to the donor task */ + struct task_struct *donor; struct rq_flags rf; + unsigned long hw_pressure; + u64 resched_latency; + + if (housekeeping_cpu(cpu, HK_TYPE_KERNEL_NOISE)) + arch_scale_freq_tick(); sched_clock_tick(); rq_lock(rq, &rf); + donor = rq->donor; + + psi_account_irqtime(rq, donor, NULL); update_rq_clock(rq); - curr->sched_class->task_tick(rq, curr, 0); - cpu_load_update_active(rq); + hw_pressure = arch_scale_hw_pressure(cpu_of(rq)); + update_hw_load_avg(rq_clock_task(rq), rq, hw_pressure); + + if (dynamic_preempt_lazy() && tif_test_bit(TIF_NEED_RESCHED_LAZY)) + resched_curr(rq); + + donor->sched_class->task_tick(rq, donor, 0); + if (sched_feat(LATENCY_WARN)) + resched_latency = cpu_resched_latency(rq); calc_global_load_tick(rq); - psi_task_tick(rq); + sched_core_tick(rq); + scx_tick(rq); rq_unlock(rq, &rf); + if (sched_feat(LATENCY_WARN) && resched_latency) + resched_latency_warn(cpu, resched_latency); + perf_event_task_tick(); -#ifdef CONFIG_SMP - rq->idle_balance = idle_cpu(cpu); - trigger_load_balance(rq); -#endif + if (donor->flags & PF_WQ_WORKER) + wq_worker_tick(donor); + + if (!scx_switched_all()) { + rq->idle_balance = idle_cpu(cpu); + sched_balance_trigger(rq); + } } #ifdef CONFIG_NO_HZ_FULL struct tick_work { int cpu; + atomic_t state; struct delayed_work work; }; +/* Values for ->state, see diagram below. */ +#define TICK_SCHED_REMOTE_OFFLINE 0 +#define TICK_SCHED_REMOTE_OFFLINING 1 +#define TICK_SCHED_REMOTE_RUNNING 2 + +/* + * State diagram for ->state: + * + * + * TICK_SCHED_REMOTE_OFFLINE + * | ^ + * | | + * | | sched_tick_remote() + * | | + * | | + * +--TICK_SCHED_REMOTE_OFFLINING + * | ^ + * | | + * sched_tick_start() | | sched_tick_stop() + * | | + * V | + * TICK_SCHED_REMOTE_RUNNING + * + * + * Other transitions get WARN_ON_ONCE(), except that sched_tick_remote() + * and sched_tick_start() are happy to leave the state in RUNNING. + */ static struct tick_work __percpu *tick_work_cpu; @@ -3075,9 +5594,7 @@ static void sched_tick_remote(struct work_struct *work) struct tick_work *twork = container_of(dwork, struct tick_work, work); int cpu = twork->cpu; struct rq *rq = cpu_rq(cpu); - struct task_struct *curr; - struct rq_flags rf; - u64 delta; + int os; /* * Handle the tick only if it appears the remote CPU is running in full @@ -3086,63 +5603,81 @@ static void sched_tick_remote(struct work_struct *work) * statistics and checks timeslices in a time-independent way, regardless * of when exactly it is running. */ - if (idle_cpu(cpu) || !tick_nohz_tick_stopped_cpu(cpu)) - goto out_requeue; + if (tick_nohz_tick_stopped_cpu(cpu)) { + guard(rq_lock_irq)(rq); + struct task_struct *curr = rq->curr; - rq_lock_irq(rq, &rf); - curr = rq->curr; - if (is_idle_task(curr)) - goto out_unlock; - - update_rq_clock(rq); - delta = rq_clock_task(rq) - curr->se.exec_start; - - /* - * Make sure the next tick runs within a reasonable - * amount of time. - */ - WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3); - curr->sched_class->task_tick(rq, curr, 0); + if (cpu_online(cpu)) { + /* + * Since this is a remote tick for full dynticks mode, + * we are always sure that there is no proxy (only a + * single task is running). + */ + WARN_ON_ONCE(rq->curr != rq->donor); + update_rq_clock(rq); + + if (!is_idle_task(curr)) { + /* + * Make sure the next tick runs within a + * reasonable amount of time. + */ + u64 delta = rq_clock_task(rq) - curr->se.exec_start; + WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 30); + } + curr->sched_class->task_tick(rq, curr, 0); -out_unlock: - rq_unlock_irq(rq, &rf); + calc_load_nohz_remote(rq); + } + } -out_requeue: /* * Run the remote tick once per second (1Hz). This arbitrary * frequency is large enough to avoid overload but short enough - * to keep scheduler internal stats reasonably up to date. + * to keep scheduler internal stats reasonably up to date. But + * first update state to reflect hotplug activity if required. */ - queue_delayed_work(system_unbound_wq, dwork, HZ); + os = atomic_fetch_add_unless(&twork->state, -1, TICK_SCHED_REMOTE_RUNNING); + WARN_ON_ONCE(os == TICK_SCHED_REMOTE_OFFLINE); + if (os == TICK_SCHED_REMOTE_RUNNING) + queue_delayed_work(system_unbound_wq, dwork, HZ); } static void sched_tick_start(int cpu) { + int os; struct tick_work *twork; - if (housekeeping_cpu(cpu, HK_FLAG_TICK)) + if (housekeeping_cpu(cpu, HK_TYPE_KERNEL_NOISE)) return; WARN_ON_ONCE(!tick_work_cpu); twork = per_cpu_ptr(tick_work_cpu, cpu); - twork->cpu = cpu; - INIT_DELAYED_WORK(&twork->work, sched_tick_remote); - queue_delayed_work(system_unbound_wq, &twork->work, HZ); + os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_RUNNING); + WARN_ON_ONCE(os == TICK_SCHED_REMOTE_RUNNING); + if (os == TICK_SCHED_REMOTE_OFFLINE) { + twork->cpu = cpu; + INIT_DELAYED_WORK(&twork->work, sched_tick_remote); + queue_delayed_work(system_unbound_wq, &twork->work, HZ); + } } #ifdef CONFIG_HOTPLUG_CPU static void sched_tick_stop(int cpu) { struct tick_work *twork; + int os; - if (housekeeping_cpu(cpu, HK_FLAG_TICK)) + if (housekeeping_cpu(cpu, HK_TYPE_KERNEL_NOISE)) return; WARN_ON_ONCE(!tick_work_cpu); twork = per_cpu_ptr(tick_work_cpu, cpu); - cancel_delayed_work_sync(&twork->work); + /* There cannot be competing actions, but don't rely on stop-machine. */ + os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_OFFLINING); + WARN_ON_ONCE(os != TICK_SCHED_REMOTE_RUNNING); + /* Don't cancel, as this would mess up the state machine. */ } #endif /* CONFIG_HOTPLUG_CPU */ @@ -3150,16 +5685,15 @@ int __init sched_tick_offload_init(void) { tick_work_cpu = alloc_percpu(struct tick_work); BUG_ON(!tick_work_cpu); - return 0; } -#else /* !CONFIG_NO_HZ_FULL */ +#else /* !CONFIG_NO_HZ_FULL: */ static inline void sched_tick_start(int cpu) { } static inline void sched_tick_stop(int cpu) { } -#endif +#endif /* !CONFIG_NO_HZ_FULL */ -#if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \ +#if defined(CONFIG_PREEMPTION) && (defined(CONFIG_DEBUG_PREEMPT) || \ defined(CONFIG_TRACE_PREEMPT_TOGGLE)) /* * If the value passed in is equal to the current preempt count @@ -3262,14 +5796,11 @@ static noinline void __schedule_bug(struct task_struct *prev) print_modules(); if (irqs_disabled()) print_irqtrace_events(prev); - if (IS_ENABLED(CONFIG_DEBUG_PREEMPT) - && in_atomic_preempt_off()) { + if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)) { pr_err("Preemption disabled at:"); - print_ip_sym(preempt_disable_ip); - pr_cont("\n"); + print_ip_sym(KERN_ERR, preempt_disable_ip); } - if (panic_on_warn) - panic("scheduling while atomic\n"); + check_panic_on_warn("scheduling while atomic"); dump_stack(); add_taint(TAINT_WARN, LOCKDEP_STILL_OK); @@ -3278,11 +5809,23 @@ static noinline void __schedule_bug(struct task_struct *prev) /* * Various schedule()-time debugging checks and statistics: */ -static inline void schedule_debug(struct task_struct *prev) +static inline void schedule_debug(struct task_struct *prev, bool preempt) { #ifdef CONFIG_SCHED_STACK_END_CHECK if (task_stack_end_corrupted(prev)) panic("corrupted stack end detected inside scheduler\n"); + + if (task_scs_end_corrupted(prev)) + panic("corrupted shadow stack detected inside scheduler\n"); +#endif + +#ifdef CONFIG_DEBUG_ATOMIC_SLEEP + if (!preempt && READ_ONCE(prev->__state) && prev->non_block_count) { + printk(KERN_ERR "BUG: scheduling in a non-blocking section: %s/%d/%i\n", + prev->comm, prev->pid, prev->non_block_count); + dump_stack(); + add_taint(TAINT_WARN, LOCKDEP_STILL_OK); + } #endif if (unlikely(in_atomic_preempt_off())) { @@ -3290,54 +5833,847 @@ static inline void schedule_debug(struct task_struct *prev) preempt_count_set(PREEMPT_DISABLED); } rcu_sleep_check(); + WARN_ON_ONCE(ct_state() == CT_STATE_USER); profile_hit(SCHED_PROFILING, __builtin_return_address(0)); schedstat_inc(this_rq()->sched_count); } +static void prev_balance(struct rq *rq, struct task_struct *prev, + struct rq_flags *rf) +{ + const struct sched_class *start_class = prev->sched_class; + const struct sched_class *class; + + /* + * We must do the balancing pass before put_prev_task(), such + * that when we release the rq->lock the task is in the same + * state as before we took rq->lock. + * + * We can terminate the balance pass as soon as we know there is + * a runnable task of @class priority or higher. + */ + for_active_class_range(class, start_class, &idle_sched_class) { + if (class->balance && class->balance(rq, prev, rf)) + break; + } +} + /* * Pick up the highest-prio task: */ static inline struct task_struct * -pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) +__pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) { const struct sched_class *class; struct task_struct *p; + rq->dl_server = NULL; + + if (scx_enabled()) + goto restart; + /* * Optimization: we know that if all tasks are in the fair class we can * call that function directly, but only if the @prev task wasn't of a - * higher scheduling class, because otherwise those loose the + * higher scheduling class, because otherwise those lose the * opportunity to pull in more work from other CPUs. */ - if (likely((prev->sched_class == &idle_sched_class || - prev->sched_class == &fair_sched_class) && - rq->nr_running == rq->cfs.h_nr_running)) { + if (likely(!sched_class_above(prev->sched_class, &fair_sched_class) && + rq->nr_running == rq->cfs.h_nr_queued)) { - p = fair_sched_class.pick_next_task(rq, prev, rf); + p = pick_next_task_fair(rq, prev, rf); if (unlikely(p == RETRY_TASK)) - goto again; + goto restart; - /* Assumes fair_sched_class->next == idle_sched_class */ - if (unlikely(!p)) - p = idle_sched_class.pick_next_task(rq, prev, rf); + /* Assume the next prioritized class is idle_sched_class */ + if (!p) { + p = pick_task_idle(rq, rf); + put_prev_set_next_task(rq, prev, p); + } return p; } -again: - for_each_class(class) { - p = class->pick_next_task(rq, prev, rf); - if (p) { +restart: + prev_balance(rq, prev, rf); + + for_each_active_class(class) { + if (class->pick_next_task) { + p = class->pick_next_task(rq, prev, rf); + if (unlikely(p == RETRY_TASK)) + goto restart; + if (p) + return p; + } else { + p = class->pick_task(rq, rf); if (unlikely(p == RETRY_TASK)) - goto again; + goto restart; + if (p) { + put_prev_set_next_task(rq, prev, p); + return p; + } + } + } + + BUG(); /* The idle class should always have a runnable task. */ +} + +#ifdef CONFIG_SCHED_CORE +static inline bool is_task_rq_idle(struct task_struct *t) +{ + return (task_rq(t)->idle == t); +} + +static inline bool cookie_equals(struct task_struct *a, unsigned long cookie) +{ + return is_task_rq_idle(a) || (a->core_cookie == cookie); +} + +static inline bool cookie_match(struct task_struct *a, struct task_struct *b) +{ + if (is_task_rq_idle(a) || is_task_rq_idle(b)) + return true; + + return a->core_cookie == b->core_cookie; +} + +/* + * Careful; this can return RETRY_TASK, it does not include the retry-loop + * itself due to the whole SMT pick retry thing below. + */ +static inline struct task_struct *pick_task(struct rq *rq, struct rq_flags *rf) +{ + const struct sched_class *class; + struct task_struct *p; + + rq->dl_server = NULL; + + for_each_active_class(class) { + p = class->pick_task(rq, rf); + if (p) return p; + } + + BUG(); /* The idle class should always have a runnable task. */ +} + +extern void task_vruntime_update(struct rq *rq, struct task_struct *p, bool in_fi); + +static void queue_core_balance(struct rq *rq); + +static struct task_struct * +pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) +{ + struct task_struct *next, *p, *max; + const struct cpumask *smt_mask; + bool fi_before = false; + bool core_clock_updated = (rq == rq->core); + unsigned long cookie; + int i, cpu, occ = 0; + struct rq *rq_i; + bool need_sync; + + if (!sched_core_enabled(rq)) + return __pick_next_task(rq, prev, rf); + + cpu = cpu_of(rq); + + /* Stopper task is switching into idle, no need core-wide selection. */ + if (cpu_is_offline(cpu)) { + /* + * Reset core_pick so that we don't enter the fastpath when + * coming online. core_pick would already be migrated to + * another cpu during offline. + */ + rq->core_pick = NULL; + rq->core_dl_server = NULL; + return __pick_next_task(rq, prev, rf); + } + + /* + * If there were no {en,de}queues since we picked (IOW, the task + * pointers are all still valid), and we haven't scheduled the last + * pick yet, do so now. + * + * rq->core_pick can be NULL if no selection was made for a CPU because + * it was either offline or went offline during a sibling's core-wide + * selection. In this case, do a core-wide selection. + */ + if (rq->core->core_pick_seq == rq->core->core_task_seq && + rq->core->core_pick_seq != rq->core_sched_seq && + rq->core_pick) { + WRITE_ONCE(rq->core_sched_seq, rq->core->core_pick_seq); + + next = rq->core_pick; + rq->dl_server = rq->core_dl_server; + rq->core_pick = NULL; + rq->core_dl_server = NULL; + goto out_set_next; + } + + prev_balance(rq, prev, rf); + + smt_mask = cpu_smt_mask(cpu); + need_sync = !!rq->core->core_cookie; + + /* reset state */ + rq->core->core_cookie = 0UL; + if (rq->core->core_forceidle_count) { + if (!core_clock_updated) { + update_rq_clock(rq->core); + core_clock_updated = true; } + sched_core_account_forceidle(rq); + /* reset after accounting force idle */ + rq->core->core_forceidle_start = 0; + rq->core->core_forceidle_count = 0; + rq->core->core_forceidle_occupation = 0; + need_sync = true; + fi_before = true; } - /* The idle class should always have a runnable task: */ - BUG(); + /* + * core->core_task_seq, core->core_pick_seq, rq->core_sched_seq + * + * @task_seq guards the task state ({en,de}queues) + * @pick_seq is the @task_seq we did a selection on + * @sched_seq is the @pick_seq we scheduled + * + * However, preemptions can cause multiple picks on the same task set. + * 'Fix' this by also increasing @task_seq for every pick. + */ + rq->core->core_task_seq++; + + /* + * Optimize for common case where this CPU has no cookies + * and there are no cookied tasks running on siblings. + */ + if (!need_sync) { +restart_single: + next = pick_task(rq, rf); + if (unlikely(next == RETRY_TASK)) + goto restart_single; + if (!next->core_cookie) { + rq->core_pick = NULL; + rq->core_dl_server = NULL; + /* + * For robustness, update the min_vruntime_fi for + * unconstrained picks as well. + */ + WARN_ON_ONCE(fi_before); + task_vruntime_update(rq, next, false); + goto out_set_next; + } + } + + /* + * For each thread: do the regular task pick and find the max prio task + * amongst them. + * + * Tie-break prio towards the current CPU + */ +restart_multi: + max = NULL; + for_each_cpu_wrap(i, smt_mask, cpu) { + rq_i = cpu_rq(i); + + /* + * Current cpu always has its clock updated on entrance to + * pick_next_task(). If the current cpu is not the core, + * the core may also have been updated above. + */ + if (i != cpu && (rq_i != rq->core || !core_clock_updated)) + update_rq_clock(rq_i); + + p = pick_task(rq_i, rf); + if (unlikely(p == RETRY_TASK)) + goto restart_multi; + + rq_i->core_pick = p; + rq_i->core_dl_server = rq_i->dl_server; + + if (!max || prio_less(max, p, fi_before)) + max = p; + } + + cookie = rq->core->core_cookie = max->core_cookie; + + /* + * For each thread: try and find a runnable task that matches @max or + * force idle. + */ + for_each_cpu(i, smt_mask) { + rq_i = cpu_rq(i); + p = rq_i->core_pick; + + if (!cookie_equals(p, cookie)) { + p = NULL; + if (cookie) + p = sched_core_find(rq_i, cookie); + if (!p) + p = idle_sched_class.pick_task(rq_i, rf); + } + + rq_i->core_pick = p; + rq_i->core_dl_server = NULL; + + if (p == rq_i->idle) { + if (rq_i->nr_running) { + rq->core->core_forceidle_count++; + if (!fi_before) + rq->core->core_forceidle_seq++; + } + } else { + occ++; + } + } + + if (schedstat_enabled() && rq->core->core_forceidle_count) { + rq->core->core_forceidle_start = rq_clock(rq->core); + rq->core->core_forceidle_occupation = occ; + } + + rq->core->core_pick_seq = rq->core->core_task_seq; + next = rq->core_pick; + rq->core_sched_seq = rq->core->core_pick_seq; + + /* Something should have been selected for current CPU */ + WARN_ON_ONCE(!next); + + /* + * Reschedule siblings + * + * NOTE: L1TF -- at this point we're no longer running the old task and + * sending an IPI (below) ensures the sibling will no longer be running + * their task. This ensures there is no inter-sibling overlap between + * non-matching user state. + */ + for_each_cpu(i, smt_mask) { + rq_i = cpu_rq(i); + + /* + * An online sibling might have gone offline before a task + * could be picked for it, or it might be offline but later + * happen to come online, but its too late and nothing was + * picked for it. That's Ok - it will pick tasks for itself, + * so ignore it. + */ + if (!rq_i->core_pick) + continue; + + /* + * Update for new !FI->FI transitions, or if continuing to be in !FI: + * fi_before fi update? + * 0 0 1 + * 0 1 1 + * 1 0 1 + * 1 1 0 + */ + if (!(fi_before && rq->core->core_forceidle_count)) + task_vruntime_update(rq_i, rq_i->core_pick, !!rq->core->core_forceidle_count); + + rq_i->core_pick->core_occupation = occ; + + if (i == cpu) { + rq_i->core_pick = NULL; + rq_i->core_dl_server = NULL; + continue; + } + + /* Did we break L1TF mitigation requirements? */ + WARN_ON_ONCE(!cookie_match(next, rq_i->core_pick)); + + if (rq_i->curr == rq_i->core_pick) { + rq_i->core_pick = NULL; + rq_i->core_dl_server = NULL; + continue; + } + + resched_curr(rq_i); + } + +out_set_next: + put_prev_set_next_task(rq, prev, next); + if (rq->core->core_forceidle_count && next == rq->idle) + queue_core_balance(rq); + + return next; +} + +static bool try_steal_cookie(int this, int that) +{ + struct rq *dst = cpu_rq(this), *src = cpu_rq(that); + struct task_struct *p; + unsigned long cookie; + bool success = false; + + guard(irq)(); + guard(double_rq_lock)(dst, src); + + cookie = dst->core->core_cookie; + if (!cookie) + return false; + + if (dst->curr != dst->idle) + return false; + + p = sched_core_find(src, cookie); + if (!p) + return false; + + do { + if (p == src->core_pick || p == src->curr) + goto next; + + if (!is_cpu_allowed(p, this)) + goto next; + + if (p->core_occupation > dst->idle->core_occupation) + goto next; + /* + * sched_core_find() and sched_core_next() will ensure + * that task @p is not throttled now, we also need to + * check whether the runqueue of the destination CPU is + * being throttled. + */ + if (sched_task_is_throttled(p, this)) + goto next; + + move_queued_task_locked(src, dst, p); + resched_curr(dst); + + success = true; + break; + +next: + p = sched_core_next(p, cookie); + } while (p); + + return success; +} + +static bool steal_cookie_task(int cpu, struct sched_domain *sd) +{ + int i; + + for_each_cpu_wrap(i, sched_domain_span(sd), cpu + 1) { + if (i == cpu) + continue; + + if (need_resched()) + break; + + if (try_steal_cookie(cpu, i)) + return true; + } + + return false; +} + +static void sched_core_balance(struct rq *rq) +{ + struct sched_domain *sd; + int cpu = cpu_of(rq); + + guard(preempt)(); + guard(rcu)(); + + raw_spin_rq_unlock_irq(rq); + for_each_domain(cpu, sd) { + if (need_resched()) + break; + + if (steal_cookie_task(cpu, sd)) + break; + } + raw_spin_rq_lock_irq(rq); +} + +static DEFINE_PER_CPU(struct balance_callback, core_balance_head); + +static void queue_core_balance(struct rq *rq) +{ + if (!sched_core_enabled(rq)) + return; + + if (!rq->core->core_cookie) + return; + + if (!rq->nr_running) /* not forced idle */ + return; + + queue_balance_callback(rq, &per_cpu(core_balance_head, rq->cpu), sched_core_balance); +} + +DEFINE_LOCK_GUARD_1(core_lock, int, + sched_core_lock(*_T->lock, &_T->flags), + sched_core_unlock(*_T->lock, &_T->flags), + unsigned long flags) + +static void sched_core_cpu_starting(unsigned int cpu) +{ + const struct cpumask *smt_mask = cpu_smt_mask(cpu); + struct rq *rq = cpu_rq(cpu), *core_rq = NULL; + int t; + + guard(core_lock)(&cpu); + + WARN_ON_ONCE(rq->core != rq); + + /* if we're the first, we'll be our own leader */ + if (cpumask_weight(smt_mask) == 1) + return; + + /* find the leader */ + for_each_cpu(t, smt_mask) { + if (t == cpu) + continue; + rq = cpu_rq(t); + if (rq->core == rq) { + core_rq = rq; + break; + } + } + + if (WARN_ON_ONCE(!core_rq)) /* whoopsie */ + return; + + /* install and validate core_rq */ + for_each_cpu(t, smt_mask) { + rq = cpu_rq(t); + + if (t == cpu) + rq->core = core_rq; + + WARN_ON_ONCE(rq->core != core_rq); + } +} + +static void sched_core_cpu_deactivate(unsigned int cpu) +{ + const struct cpumask *smt_mask = cpu_smt_mask(cpu); + struct rq *rq = cpu_rq(cpu), *core_rq = NULL; + int t; + + guard(core_lock)(&cpu); + + /* if we're the last man standing, nothing to do */ + if (cpumask_weight(smt_mask) == 1) { + WARN_ON_ONCE(rq->core != rq); + return; + } + + /* if we're not the leader, nothing to do */ + if (rq->core != rq) + return; + + /* find a new leader */ + for_each_cpu(t, smt_mask) { + if (t == cpu) + continue; + core_rq = cpu_rq(t); + break; + } + + if (WARN_ON_ONCE(!core_rq)) /* impossible */ + return; + + /* copy the shared state to the new leader */ + core_rq->core_task_seq = rq->core_task_seq; + core_rq->core_pick_seq = rq->core_pick_seq; + core_rq->core_cookie = rq->core_cookie; + core_rq->core_forceidle_count = rq->core_forceidle_count; + core_rq->core_forceidle_seq = rq->core_forceidle_seq; + core_rq->core_forceidle_occupation = rq->core_forceidle_occupation; + + /* + * Accounting edge for forced idle is handled in pick_next_task(). + * Don't need another one here, since the hotplug thread shouldn't + * have a cookie. + */ + core_rq->core_forceidle_start = 0; + + /* install new leader */ + for_each_cpu(t, smt_mask) { + rq = cpu_rq(t); + rq->core = core_rq; + } +} + +static inline void sched_core_cpu_dying(unsigned int cpu) +{ + struct rq *rq = cpu_rq(cpu); + + if (rq->core != rq) + rq->core = rq; +} + +#else /* !CONFIG_SCHED_CORE: */ + +static inline void sched_core_cpu_starting(unsigned int cpu) {} +static inline void sched_core_cpu_deactivate(unsigned int cpu) {} +static inline void sched_core_cpu_dying(unsigned int cpu) {} + +static struct task_struct * +pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) +{ + return __pick_next_task(rq, prev, rf); +} + +#endif /* !CONFIG_SCHED_CORE */ + +/* + * Constants for the sched_mode argument of __schedule(). + * + * The mode argument allows RT enabled kernels to differentiate a + * preemption from blocking on an 'sleeping' spin/rwlock. + */ +#define SM_IDLE (-1) +#define SM_NONE 0 +#define SM_PREEMPT 1 +#define SM_RTLOCK_WAIT 2 + +/* + * Helper function for __schedule() + * + * Tries to deactivate the task, unless the should_block arg + * is false or if a signal is pending. In the case a signal + * is pending, marks the task's __state as RUNNING (and clear + * blocked_on). + */ +static bool try_to_block_task(struct rq *rq, struct task_struct *p, + unsigned long *task_state_p, bool should_block) +{ + unsigned long task_state = *task_state_p; + int flags = DEQUEUE_NOCLOCK; + + if (signal_pending_state(task_state, p)) { + WRITE_ONCE(p->__state, TASK_RUNNING); + *task_state_p = TASK_RUNNING; + return false; + } + + /* + * We check should_block after signal_pending because we + * will want to wake the task in that case. But if + * should_block is false, its likely due to the task being + * blocked on a mutex, and we want to keep it on the runqueue + * to be selectable for proxy-execution. + */ + if (!should_block) + return false; + + p->sched_contributes_to_load = + (task_state & TASK_UNINTERRUPTIBLE) && + !(task_state & TASK_NOLOAD) && + !(task_state & TASK_FROZEN); + + if (unlikely(is_special_task_state(task_state))) + flags |= DEQUEUE_SPECIAL; + + /* + * __schedule() ttwu() + * prev_state = prev->state; if (p->on_rq && ...) + * if (prev_state) goto out; + * p->on_rq = 0; smp_acquire__after_ctrl_dep(); + * p->state = TASK_WAKING + * + * Where __schedule() and ttwu() have matching control dependencies. + * + * After this, schedule() must not care about p->state any more. + */ + block_task(rq, p, flags); + return true; +} + +#ifdef CONFIG_SCHED_PROXY_EXEC +static inline struct task_struct *proxy_resched_idle(struct rq *rq) +{ + put_prev_set_next_task(rq, rq->donor, rq->idle); + rq_set_donor(rq, rq->idle); + set_tsk_need_resched(rq->idle); + return rq->idle; +} + +static bool __proxy_deactivate(struct rq *rq, struct task_struct *donor) +{ + unsigned long state = READ_ONCE(donor->__state); + + /* Don't deactivate if the state has been changed to TASK_RUNNING */ + if (state == TASK_RUNNING) + return false; + /* + * Because we got donor from pick_next_task(), it is *crucial* + * that we call proxy_resched_idle() before we deactivate it. + * As once we deactivate donor, donor->on_rq is set to zero, + * which allows ttwu() to immediately try to wake the task on + * another rq. So we cannot use *any* references to donor + * after that point. So things like cfs_rq->curr or rq->donor + * need to be changed from next *before* we deactivate. + */ + proxy_resched_idle(rq); + return try_to_block_task(rq, donor, &state, true); +} + +static struct task_struct *proxy_deactivate(struct rq *rq, struct task_struct *donor) +{ + if (!__proxy_deactivate(rq, donor)) { + /* + * XXX: For now, if deactivation failed, set donor + * as unblocked, as we aren't doing proxy-migrations + * yet (more logic will be needed then). + */ + donor->blocked_on = NULL; + } + return NULL; +} + +/* + * Find runnable lock owner to proxy for mutex blocked donor + * + * Follow the blocked-on relation: + * task->blocked_on -> mutex->owner -> task... + * + * Lock order: + * + * p->pi_lock + * rq->lock + * mutex->wait_lock + * + * Returns the task that is going to be used as execution context (the one + * that is actually going to be run on cpu_of(rq)). + */ +static struct task_struct * +find_proxy_task(struct rq *rq, struct task_struct *donor, struct rq_flags *rf) +{ + struct task_struct *owner = NULL; + int this_cpu = cpu_of(rq); + struct task_struct *p; + struct mutex *mutex; + + /* Follow blocked_on chain. */ + for (p = donor; task_is_blocked(p); p = owner) { + mutex = p->blocked_on; + /* Something changed in the chain, so pick again */ + if (!mutex) + return NULL; + /* + * By taking mutex->wait_lock we hold off concurrent mutex_unlock() + * and ensure @owner sticks around. + */ + guard(raw_spinlock)(&mutex->wait_lock); + + /* Check again that p is blocked with wait_lock held */ + if (mutex != __get_task_blocked_on(p)) { + /* + * Something changed in the blocked_on chain and + * we don't know if only at this level. So, let's + * just bail out completely and let __schedule() + * figure things out (pick_again loop). + */ + return NULL; + } + + owner = __mutex_owner(mutex); + if (!owner) { + __clear_task_blocked_on(p, mutex); + return p; + } + + if (!READ_ONCE(owner->on_rq) || owner->se.sched_delayed) { + /* XXX Don't handle blocked owners/delayed dequeue yet */ + return proxy_deactivate(rq, donor); + } + + if (task_cpu(owner) != this_cpu) { + /* XXX Don't handle migrations yet */ + return proxy_deactivate(rq, donor); + } + + if (task_on_rq_migrating(owner)) { + /* + * One of the chain of mutex owners is currently migrating to this + * CPU, but has not yet been enqueued because we are holding the + * rq lock. As a simple solution, just schedule rq->idle to give + * the migration a chance to complete. Much like the migrate_task + * case we should end up back in find_proxy_task(), this time + * hopefully with all relevant tasks already enqueued. + */ + return proxy_resched_idle(rq); + } + + /* + * Its possible to race where after we check owner->on_rq + * but before we check (owner_cpu != this_cpu) that the + * task on another cpu was migrated back to this cpu. In + * that case it could slip by our checks. So double check + * we are still on this cpu and not migrating. If we get + * inconsistent results, try again. + */ + if (!task_on_rq_queued(owner) || task_cpu(owner) != this_cpu) + return NULL; + + if (owner == p) { + /* + * It's possible we interleave with mutex_unlock like: + * + * lock(&rq->lock); + * find_proxy_task() + * mutex_unlock() + * lock(&wait_lock); + * donor(owner) = current->blocked_donor; + * unlock(&wait_lock); + * + * wake_up_q(); + * ... + * ttwu_runnable() + * __task_rq_lock() + * lock(&wait_lock); + * owner == p + * + * Which leaves us to finish the ttwu_runnable() and make it go. + * + * So schedule rq->idle so that ttwu_runnable() can get the rq + * lock and mark owner as running. + */ + return proxy_resched_idle(rq); + } + /* + * OK, now we're absolutely sure @owner is on this + * rq, therefore holding @rq->lock is sufficient to + * guarantee its existence, as per ttwu_remote(). + */ + } + + WARN_ON_ONCE(owner && !owner->on_rq); + return owner; +} +#else /* SCHED_PROXY_EXEC */ +static struct task_struct * +find_proxy_task(struct rq *rq, struct task_struct *donor, struct rq_flags *rf) +{ + WARN_ONCE(1, "This should never be called in the !SCHED_PROXY_EXEC case\n"); + return donor; +} +#endif /* SCHED_PROXY_EXEC */ + +static inline void proxy_tag_curr(struct rq *rq, struct task_struct *owner) +{ + if (!sched_proxy_exec()) + return; + /* + * pick_next_task() calls set_next_task() on the chosen task + * at some point, which ensures it is not push/pullable. + * However, the chosen/donor task *and* the mutex owner form an + * atomic pair wrt push/pull. + * + * Make sure owner we run is not pushable. Unfortunately we can + * only deal with that by means of a dequeue/enqueue cycle. :-/ + */ + dequeue_task(rq, owner, DEQUEUE_NOCLOCK | DEQUEUE_SAVE); + enqueue_task(rq, owner, ENQUEUE_NOCLOCK | ENQUEUE_RESTORE); } /* @@ -3351,7 +6687,7 @@ again: * paths. For example, see arch/x86/entry_64.S. * * To drive preemption between tasks, the scheduler sets the flag in timer - * interrupt handler scheduler_tick(). + * interrupt handler sched_tick(). * * 3. Wakeups don't really cause entry into schedule(). They add a * task to the run-queue and that's it. @@ -3360,7 +6696,7 @@ again: * task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets * called on the nearest possible occasion: * - * - If the kernel is preemptible (CONFIG_PREEMPT=y): + * - If the kernel is preemptible (CONFIG_PREEMPTION=y): * * - in syscall or exception context, at the next outmost * preempt_enable(). (this might be as soon as the wake_up()'s @@ -3369,7 +6705,7 @@ again: * - in IRQ context, return from interrupt-handler to * preemptible context * - * - If the kernel is not preemptible (CONFIG_PREEMPT is not set) + * - If the kernel is not preemptible (CONFIG_PREEMPTION is not set) * then at the next: * * - cond_resched() call @@ -3379,33 +6715,55 @@ again: * * WARNING: must be called with preemption disabled! */ -static void __sched notrace __schedule(bool preempt) +static void __sched notrace __schedule(int sched_mode) { struct task_struct *prev, *next; + /* + * On PREEMPT_RT kernel, SM_RTLOCK_WAIT is noted + * as a preemption by schedule_debug() and RCU. + */ + bool preempt = sched_mode > SM_NONE; + bool is_switch = false; unsigned long *switch_count; + unsigned long prev_state; struct rq_flags rf; struct rq *rq; int cpu; + /* Trace preemptions consistently with task switches */ + trace_sched_entry_tp(sched_mode == SM_PREEMPT); + cpu = smp_processor_id(); rq = cpu_rq(cpu); prev = rq->curr; - schedule_debug(prev); + schedule_debug(prev, preempt); - if (sched_feat(HRTICK)) + if (sched_feat(HRTICK) || sched_feat(HRTICK_DL)) hrtick_clear(rq); + klp_sched_try_switch(prev); + local_irq_disable(); rcu_note_context_switch(preempt); + migrate_disable_switch(rq, prev); /* * Make sure that signal_pending_state()->signal_pending() below * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE) - * done by the caller to avoid the race with signal_wake_up(). + * done by the caller to avoid the race with signal_wake_up(): * - * The membarrier system call requires a full memory barrier - * after coming from user-space, before storing to rq->curr. + * __set_current_state(@state) signal_wake_up() + * schedule() set_tsk_thread_flag(p, TIF_SIGPENDING) + * wake_up_state(p, state) + * LOCK rq->lock LOCK p->pi_state + * smp_mb__after_spinlock() smp_mb__after_spinlock() + * if (signal_pending_state()) if (p->state & @state) + * + * Also, the membarrier system call requires a full memory barrier + * after coming from user-space, before storing to rq->curr; this + * barrier matches a full barrier in the proximity of the membarrier + * system call exit. */ rq_lock(rq, &rf); smp_mb__after_spinlock(); @@ -3413,43 +6771,64 @@ static void __sched notrace __schedule(bool preempt) /* Promote REQ to ACT */ rq->clock_update_flags <<= 1; update_rq_clock(rq); + rq->clock_update_flags = RQCF_UPDATED; switch_count = &prev->nivcsw; - if (!preempt && prev->state) { - if (signal_pending_state(prev->state, prev)) { - prev->state = TASK_RUNNING; - } else { - deactivate_task(rq, prev, DEQUEUE_SLEEP | DEQUEUE_NOCLOCK); - prev->on_rq = 0; - if (prev->in_iowait) { - atomic_inc(&rq->nr_iowait); - delayacct_blkio_start(); - } + /* Task state changes only considers SM_PREEMPT as preemption */ + preempt = sched_mode == SM_PREEMPT; - /* - * If a worker went to sleep, notify and ask workqueue - * whether it wants to wake up a task to maintain - * concurrency. - */ - if (prev->flags & PF_WQ_WORKER) { - struct task_struct *to_wakeup; - - to_wakeup = wq_worker_sleeping(prev); - if (to_wakeup) - try_to_wake_up_local(to_wakeup, &rf); - } + /* + * We must load prev->state once (task_struct::state is volatile), such + * that we form a control dependency vs deactivate_task() below. + */ + prev_state = READ_ONCE(prev->__state); + if (sched_mode == SM_IDLE) { + /* SCX must consult the BPF scheduler to tell if rq is empty */ + if (!rq->nr_running && !scx_enabled()) { + next = prev; + goto picked; } + } else if (!preempt && prev_state) { + /* + * We pass task_is_blocked() as the should_block arg + * in order to keep mutex-blocked tasks on the runqueue + * for slection with proxy-exec (without proxy-exec + * task_is_blocked() will always be false). + */ + try_to_block_task(rq, prev, &prev_state, + !task_is_blocked(prev)); switch_count = &prev->nvcsw; } - next = pick_next_task(rq, prev, &rf); +pick_again: + next = pick_next_task(rq, rq->donor, &rf); + rq_set_donor(rq, next); + if (unlikely(task_is_blocked(next))) { + next = find_proxy_task(rq, next, &rf); + if (!next) + goto pick_again; + if (next == rq->idle) + goto keep_resched; + } +picked: clear_tsk_need_resched(prev); clear_preempt_need_resched(); +keep_resched: + rq->last_seen_need_resched_ns = 0; - if (likely(prev != next)) { + is_switch = prev != next; + if (likely(is_switch)) { rq->nr_switches++; - rq->curr = next; + /* + * RCU users of rcu_dereference(rq->curr) may not see + * changes to task_struct made by pick_next_task(). + */ + RCU_INIT_POINTER(rq->curr, next); + + if (!task_current_donor(rq, next)) + proxy_tag_curr(rq, next); + /* * The membarrier system call requires each architecture * to have a full memory barrier after updating @@ -3457,25 +6836,41 @@ static void __sched notrace __schedule(bool preempt) * * Here are the schemes providing that barrier on the * various architectures: - * - mm ? switch_mm() : mmdrop() for x86, s390, sparc, PowerPC. - * switch_mm() rely on membarrier_arch_switch_mm() on PowerPC. + * - mm ? switch_mm() : mmdrop() for x86, s390, sparc, PowerPC, + * RISC-V. switch_mm() relies on membarrier_arch_switch_mm() + * on PowerPC and on RISC-V. * - finish_lock_switch() for weakly-ordered * architectures where spin_unlock is a full barrier, * - switch_to() for arm64 (weakly-ordered, spin_unlock * is a RELEASE barrier), + * + * The barrier matches a full barrier in the proximity of + * the membarrier system call entry. + * + * On RISC-V, this barrier pairing is also needed for the + * SYNC_CORE command when switching between processes, cf. + * the inline comments in membarrier_arch_switch_mm(). */ ++*switch_count; - trace_sched_switch(preempt, prev, next); + psi_account_irqtime(rq, prev, next); + psi_sched_switch(prev, next, !task_on_rq_queued(prev) || + prev->se.sched_delayed); + + trace_sched_switch(preempt, prev, next, prev_state); /* Also unlocks the rq: */ rq = context_switch(rq, prev, next, &rf); } else { - rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP); - rq_unlock_irq(rq, &rf); - } + /* In case next was already curr but just got blocked_donor */ + if (!task_current_donor(rq, next)) + proxy_tag_curr(rq, next); - balance_callback(rq); + rq_unpin_lock(rq, &rf); + __balance_callbacks(rq); + raw_spin_rq_unlock_irq(rq); + } + trace_sched_exit_tp(is_switch); } void __noreturn do_task_dead(void) @@ -3486,7 +6881,7 @@ void __noreturn do_task_dead(void) /* Tell freezer to ignore us: */ current->flags |= PF_NOFREEZE; - __schedule(false); + __schedule(SM_NONE); BUG(); /* Avoid "noreturn function does return" - but don't continue if BUG() is a NOP: */ @@ -3496,27 +6891,75 @@ void __noreturn do_task_dead(void) static inline void sched_submit_work(struct task_struct *tsk) { - if (!tsk->state || tsk_is_pi_blocked(tsk)) - return; + static DEFINE_WAIT_OVERRIDE_MAP(sched_map, LD_WAIT_CONFIG); + unsigned int task_flags; + + /* + * Establish LD_WAIT_CONFIG context to ensure none of the code called + * will use a blocking primitive -- which would lead to recursion. + */ + lock_map_acquire_try(&sched_map); + + task_flags = tsk->flags; + /* + * If a worker goes to sleep, notify and ask workqueue whether it + * wants to wake up a task to maintain concurrency. + */ + if (task_flags & PF_WQ_WORKER) + wq_worker_sleeping(tsk); + else if (task_flags & PF_IO_WORKER) + io_wq_worker_sleeping(tsk); + + /* + * spinlock and rwlock must not flush block requests. This will + * deadlock if the callback attempts to acquire a lock which is + * already acquired. + */ + WARN_ON_ONCE(current->__state & TASK_RTLOCK_WAIT); + /* * If we are going to sleep and we have plugged IO queued, * make sure to submit it to avoid deadlocks. */ - if (blk_needs_flush_plug(tsk)) - blk_schedule_flush_plug(tsk); + blk_flush_plug(tsk->plug, true); + + lock_map_release(&sched_map); } -asmlinkage __visible void __sched schedule(void) +static void sched_update_worker(struct task_struct *tsk) { - struct task_struct *tsk = current; + if (tsk->flags & (PF_WQ_WORKER | PF_IO_WORKER | PF_BLOCK_TS)) { + if (tsk->flags & PF_BLOCK_TS) + blk_plug_invalidate_ts(tsk); + if (tsk->flags & PF_WQ_WORKER) + wq_worker_running(tsk); + else if (tsk->flags & PF_IO_WORKER) + io_wq_worker_running(tsk); + } +} - sched_submit_work(tsk); +static __always_inline void __schedule_loop(int sched_mode) +{ do { preempt_disable(); - __schedule(false); + __schedule(sched_mode); sched_preempt_enable_no_resched(); } while (need_resched()); } + +asmlinkage __visible void __sched schedule(void) +{ + struct task_struct *tsk = current; + +#ifdef CONFIG_RT_MUTEXES + lockdep_assert(!tsk->sched_rt_mutex); +#endif + + if (!task_is_running(tsk)) + sched_submit_work(tsk); + __schedule_loop(SM_NONE); + sched_update_worker(tsk); +} EXPORT_SYMBOL(schedule); /* @@ -3533,18 +6976,18 @@ void __sched schedule_idle(void) { /* * As this skips calling sched_submit_work(), which the idle task does - * regardless because that function is a nop when the task is in a + * regardless because that function is a NOP when the task is in a * TASK_RUNNING state, make sure this isn't used someplace that the * current task can be in any other state. Note, idle is always in the * TASK_RUNNING state. */ - WARN_ON_ONCE(current->state); + WARN_ON_ONCE(current->__state); do { - __schedule(false); + __schedule(SM_IDLE); } while (need_resched()); } -#ifdef CONFIG_CONTEXT_TRACKING +#if defined(CONFIG_CONTEXT_TRACKING_USER) && !defined(CONFIG_HAVE_CONTEXT_TRACKING_USER_OFFSTACK) asmlinkage __visible void __sched schedule_user(void) { /* @@ -3554,7 +6997,7 @@ asmlinkage __visible void __sched schedule_user(void) * we find a better solution. * * NB: There are buggy callers of this function. Ideally we - * should warn if prev_state != CONTEXT_USER, but that will trigger + * should warn if prev_state != CT_STATE_USER, but that will trigger * too frequently to make sense yet. */ enum ctx_state prev_state = exception_enter(); @@ -3575,6 +7018,14 @@ void __sched schedule_preempt_disabled(void) preempt_disable(); } +#ifdef CONFIG_PREEMPT_RT +void __sched notrace schedule_rtlock(void) +{ + __schedule_loop(SM_RTLOCK_WAIT); +} +NOKPROBE_SYMBOL(schedule_rtlock); +#endif + static void __sched notrace preempt_schedule_common(void) { do { @@ -3593,7 +7044,7 @@ static void __sched notrace preempt_schedule_common(void) */ preempt_disable_notrace(); preempt_latency_start(1); - __schedule(true); + __schedule(SM_PREEMPT); preempt_latency_stop(1); preempt_enable_no_resched_notrace(); @@ -3604,11 +7055,10 @@ static void __sched notrace preempt_schedule_common(void) } while (need_resched()); } -#ifdef CONFIG_PREEMPT +#ifdef CONFIG_PREEMPTION /* - * this is the entry point to schedule() from in-kernel preemption - * off of preempt_enable. Kernel preemptions off return from interrupt - * occur there and call schedule directly. + * This is the entry point to schedule() from in-kernel preemption + * off of preempt_enable. */ asmlinkage __visible void __sched notrace preempt_schedule(void) { @@ -3618,12 +7068,32 @@ asmlinkage __visible void __sched notrace preempt_schedule(void) */ if (likely(!preemptible())) return; - preempt_schedule_common(); } NOKPROBE_SYMBOL(preempt_schedule); EXPORT_SYMBOL(preempt_schedule); +#ifdef CONFIG_PREEMPT_DYNAMIC +# ifdef CONFIG_HAVE_PREEMPT_DYNAMIC_CALL +# ifndef preempt_schedule_dynamic_enabled +# define preempt_schedule_dynamic_enabled preempt_schedule +# define preempt_schedule_dynamic_disabled NULL +# endif +DEFINE_STATIC_CALL(preempt_schedule, preempt_schedule_dynamic_enabled); +EXPORT_STATIC_CALL_TRAMP(preempt_schedule); +# elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY) +static DEFINE_STATIC_KEY_TRUE(sk_dynamic_preempt_schedule); +void __sched notrace dynamic_preempt_schedule(void) +{ + if (!static_branch_unlikely(&sk_dynamic_preempt_schedule)) + return; + preempt_schedule(); +} +NOKPROBE_SYMBOL(dynamic_preempt_schedule); +EXPORT_SYMBOL(dynamic_preempt_schedule); +# endif +#endif /* CONFIG_PREEMPT_DYNAMIC */ + /** * preempt_schedule_notrace - preempt_schedule called by tracing * @@ -3667,7 +7137,7 @@ asmlinkage __visible void __sched notrace preempt_schedule_notrace(void) * an infinite recursion. */ prev_ctx = exception_enter(); - __schedule(true); + __schedule(SM_PREEMPT); exception_exit(prev_ctx); preempt_latency_stop(1); @@ -3676,13 +7146,34 @@ asmlinkage __visible void __sched notrace preempt_schedule_notrace(void) } EXPORT_SYMBOL_GPL(preempt_schedule_notrace); -#endif /* CONFIG_PREEMPT */ +#ifdef CONFIG_PREEMPT_DYNAMIC +# if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL) +# ifndef preempt_schedule_notrace_dynamic_enabled +# define preempt_schedule_notrace_dynamic_enabled preempt_schedule_notrace +# define preempt_schedule_notrace_dynamic_disabled NULL +# endif +DEFINE_STATIC_CALL(preempt_schedule_notrace, preempt_schedule_notrace_dynamic_enabled); +EXPORT_STATIC_CALL_TRAMP(preempt_schedule_notrace); +# elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY) +static DEFINE_STATIC_KEY_TRUE(sk_dynamic_preempt_schedule_notrace); +void __sched notrace dynamic_preempt_schedule_notrace(void) +{ + if (!static_branch_unlikely(&sk_dynamic_preempt_schedule_notrace)) + return; + preempt_schedule_notrace(); +} +NOKPROBE_SYMBOL(dynamic_preempt_schedule_notrace); +EXPORT_SYMBOL(dynamic_preempt_schedule_notrace); +# endif +#endif + +#endif /* CONFIG_PREEMPTION */ /* - * this is the entry point to schedule() from kernel preemption - * off of irq context. - * Note, that this is called and return with irqs disabled. This will - * protect us against recursive calling from irq. + * This is the entry point to schedule() from kernel preemption + * off of IRQ context. + * Note, that this is called and return with IRQs disabled. This will + * protect us against recursive calling from IRQ contexts. */ asmlinkage __visible void __sched preempt_schedule_irq(void) { @@ -3696,7 +7187,7 @@ asmlinkage __visible void __sched preempt_schedule_irq(void) do { preempt_disable(); local_irq_enable(); - __schedule(true); + __schedule(SM_PREEMPT); local_irq_disable(); sched_preempt_enable_no_resched(); } while (need_resched()); @@ -3707,25 +7198,53 @@ asmlinkage __visible void __sched preempt_schedule_irq(void) int default_wake_function(wait_queue_entry_t *curr, unsigned mode, int wake_flags, void *key) { + WARN_ON_ONCE(wake_flags & ~(WF_SYNC|WF_CURRENT_CPU)); return try_to_wake_up(curr->private, mode, wake_flags); } EXPORT_SYMBOL(default_wake_function); +const struct sched_class *__setscheduler_class(int policy, int prio) +{ + if (dl_prio(prio)) + return &dl_sched_class; + + if (rt_prio(prio)) + return &rt_sched_class; + +#ifdef CONFIG_SCHED_CLASS_EXT + if (task_should_scx(policy)) + return &ext_sched_class; +#endif + + return &fair_sched_class; +} + #ifdef CONFIG_RT_MUTEXES -static inline int __rt_effective_prio(struct task_struct *pi_task, int prio) -{ - if (pi_task) - prio = min(prio, pi_task->prio); +/* + * Would be more useful with typeof()/auto_type but they don't mix with + * bit-fields. Since it's a local thing, use int. Keep the generic sounding + * name such that if someone were to implement this function we get to compare + * notes. + */ +#define fetch_and_set(x, v) ({ int _x = (x); (x) = (v); _x; }) - return prio; +void rt_mutex_pre_schedule(void) +{ + lockdep_assert(!fetch_and_set(current->sched_rt_mutex, 1)); + sched_submit_work(current); } -static inline int rt_effective_prio(struct task_struct *p, int prio) +void rt_mutex_schedule(void) { - struct task_struct *pi_task = rt_mutex_get_top_task(p); + lockdep_assert(current->sched_rt_mutex); + __schedule_loop(SM_NONE); +} - return __rt_effective_prio(pi_task, prio); +void rt_mutex_post_schedule(void) +{ + sched_update_worker(current); + lockdep_assert(fetch_and_set(current->sched_rt_mutex, 0)); } /* @@ -3741,9 +7260,9 @@ static inline int rt_effective_prio(struct task_struct *p, int prio) */ void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task) { - int prio, oldprio, queued, running, queue_flag = + int prio, oldprio, queue_flag = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK; - const struct sched_class *prev_class; + const struct sched_class *prev_class, *next_class; struct rq_flags rf; struct rq *rq; @@ -3766,7 +7285,7 @@ void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task) * right. rt_mutex_slowunlock()+rt_mutex_postunlock() work together to * ensure a task is de-boosted (pi_task is set to NULL) before the * task is allowed to run again (and can exit). This ensures the pointer - * points to a blocked task -- which guaratees the task is present. + * points to a blocked task -- which guarantees the task is present. */ p->pi_top_task = pi_task; @@ -3777,7 +7296,7 @@ void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task) goto out_unlock; /* - * Idle task boosting is a nono in general. There is one + * Idle task boosting is a no-no in general. There is one * exception, when PREEMPT_RT and NOHZ is active: * * The idle task calls get_next_timer_interrupt() and holds @@ -3801,1309 +7320,442 @@ void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task) queue_flag &= ~DEQUEUE_MOVE; prev_class = p->sched_class; - queued = task_on_rq_queued(p); - running = task_current(rq, p); - if (queued) - dequeue_task(rq, p, queue_flag); - if (running) - put_prev_task(rq, p); - - /* - * Boosting condition are: - * 1. -rt task is running and holds mutex A - * --> -dl task blocks on mutex A - * - * 2. -dl task is running and holds mutex A - * --> -dl task blocks on mutex A and could preempt the - * running task - */ - if (dl_prio(prio)) { - if (!dl_prio(p->normal_prio) || - (pi_task && dl_entity_preempt(&pi_task->dl, &p->dl))) { - p->dl.dl_boosted = 1; - queue_flag |= ENQUEUE_REPLENISH; - } else - p->dl.dl_boosted = 0; - p->sched_class = &dl_sched_class; - } else if (rt_prio(prio)) { - if (dl_prio(oldprio)) - p->dl.dl_boosted = 0; - if (oldprio < prio) - queue_flag |= ENQUEUE_HEAD; - p->sched_class = &rt_sched_class; - } else { - if (dl_prio(oldprio)) - p->dl.dl_boosted = 0; - if (rt_prio(oldprio)) - p->rt.timeout = 0; - p->sched_class = &fair_sched_class; - } - - p->prio = prio; - - if (queued) - enqueue_task(rq, p, queue_flag); - if (running) - set_curr_task(rq, p); - - check_class_changed(rq, p, prev_class, oldprio); -out_unlock: - /* Avoid rq from going away on us: */ - preempt_disable(); - __task_rq_unlock(rq, &rf); - - balance_callback(rq); - preempt_enable(); -} -#else -static inline int rt_effective_prio(struct task_struct *p, int prio) -{ - return prio; -} -#endif + next_class = __setscheduler_class(p->policy, prio); -void set_user_nice(struct task_struct *p, long nice) -{ - bool queued, running; - int old_prio, delta; - struct rq_flags rf; - struct rq *rq; - - if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE) - return; - /* - * We have to be careful, if called from sys_setpriority(), - * the task might be in the middle of scheduling on another CPU. - */ - rq = task_rq_lock(p, &rf); - update_rq_clock(rq); - - /* - * The RT priorities are set via sched_setscheduler(), but we still - * allow the 'normal' nice value to be set - but as expected - * it wont have any effect on scheduling until the task is - * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR: - */ - if (task_has_dl_policy(p) || task_has_rt_policy(p)) { - p->static_prio = NICE_TO_PRIO(nice); - goto out_unlock; - } - queued = task_on_rq_queued(p); - running = task_current(rq, p); - if (queued) - dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK); - if (running) - put_prev_task(rq, p); + if (prev_class != next_class) + queue_flag |= DEQUEUE_CLASS; - p->static_prio = NICE_TO_PRIO(nice); - set_load_weight(p, true); - old_prio = p->prio; - p->prio = effective_prio(p); - delta = p->prio - old_prio; - - if (queued) { - enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK); + scoped_guard (sched_change, p, queue_flag) { /* - * If the task increased its priority or is running and - * lowered its priority, then reschedule its CPU: + * Boosting condition are: + * 1. -rt task is running and holds mutex A + * --> -dl task blocks on mutex A + * + * 2. -dl task is running and holds mutex A + * --> -dl task blocks on mutex A and could preempt the + * running task */ - if (delta < 0 || (delta > 0 && task_running(rq, p))) - resched_curr(rq); + if (dl_prio(prio)) { + if (!dl_prio(p->normal_prio) || + (pi_task && dl_prio(pi_task->prio) && + dl_entity_preempt(&pi_task->dl, &p->dl))) { + p->dl.pi_se = pi_task->dl.pi_se; + scope->flags |= ENQUEUE_REPLENISH; + } else { + p->dl.pi_se = &p->dl; + } + } else if (rt_prio(prio)) { + if (dl_prio(oldprio)) + p->dl.pi_se = &p->dl; + if (oldprio < prio) + scope->flags |= ENQUEUE_HEAD; + } else { + if (dl_prio(oldprio)) + p->dl.pi_se = &p->dl; + if (rt_prio(oldprio)) + p->rt.timeout = 0; + } + + p->sched_class = next_class; + p->prio = prio; } - if (running) - set_curr_task(rq, p); out_unlock: - task_rq_unlock(rq, p, &rf); -} -EXPORT_SYMBOL(set_user_nice); + /* Caller holds task_struct::pi_lock, IRQs are still disabled */ -/* - * can_nice - check if a task can reduce its nice value - * @p: task - * @nice: nice value - */ -int can_nice(const struct task_struct *p, const int nice) -{ - /* Convert nice value [19,-20] to rlimit style value [1,40]: */ - int nice_rlim = nice_to_rlimit(nice); - - return (nice_rlim <= task_rlimit(p, RLIMIT_NICE) || - capable(CAP_SYS_NICE)); + rq_unpin_lock(rq, &rf); + __balance_callbacks(rq); + rq_repin_lock(rq, &rf); + __task_rq_unlock(rq, p, &rf); } +#endif /* CONFIG_RT_MUTEXES */ -#ifdef __ARCH_WANT_SYS_NICE - -/* - * sys_nice - change the priority of the current process. - * @increment: priority increment - * - * sys_setpriority is a more generic, but much slower function that - * does similar things. - */ -SYSCALL_DEFINE1(nice, int, increment) +#if !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC) +int __sched __cond_resched(void) { - long nice, retval; - + if (should_resched(0) && !irqs_disabled()) { + preempt_schedule_common(); + return 1; + } /* - * Setpriority might change our priority at the same moment. - * We don't have to worry. Conceptually one call occurs first - * and we have a single winner. + * In PREEMPT_RCU kernels, ->rcu_read_lock_nesting tells the tick + * whether the current CPU is in an RCU read-side critical section, + * so the tick can report quiescent states even for CPUs looping + * in kernel context. In contrast, in non-preemptible kernels, + * RCU readers leave no in-memory hints, which means that CPU-bound + * processes executing in kernel context might never report an + * RCU quiescent state. Therefore, the following code causes + * cond_resched() to report a quiescent state, but only when RCU + * is in urgent need of one. + * A third case, preemptible, but non-PREEMPT_RCU provides for + * urgently needed quiescent states via rcu_flavor_sched_clock_irq(). */ - increment = clamp(increment, -NICE_WIDTH, NICE_WIDTH); - nice = task_nice(current) + increment; - - nice = clamp_val(nice, MIN_NICE, MAX_NICE); - if (increment < 0 && !can_nice(current, nice)) - return -EPERM; - - retval = security_task_setnice(current, nice); - if (retval) - return retval; - - set_user_nice(current, nice); +#ifndef CONFIG_PREEMPT_RCU + rcu_all_qs(); +#endif return 0; } - +EXPORT_SYMBOL(__cond_resched); #endif -/** - * task_prio - return the priority value of a given task. - * @p: the task in question. - * - * Return: The priority value as seen by users in /proc. - * RT tasks are offset by -200. Normal tasks are centered - * around 0, value goes from -16 to +15. - */ -int task_prio(const struct task_struct *p) -{ - return p->prio - MAX_RT_PRIO; -} - -/** - * idle_cpu - is a given CPU idle currently? - * @cpu: the processor in question. - * - * Return: 1 if the CPU is currently idle. 0 otherwise. - */ -int idle_cpu(int cpu) -{ - struct rq *rq = cpu_rq(cpu); - - if (rq->curr != rq->idle) - return 0; - - if (rq->nr_running) - return 0; - -#ifdef CONFIG_SMP - if (!llist_empty(&rq->wake_list)) +#ifdef CONFIG_PREEMPT_DYNAMIC +# ifdef CONFIG_HAVE_PREEMPT_DYNAMIC_CALL +# define cond_resched_dynamic_enabled __cond_resched +# define cond_resched_dynamic_disabled ((void *)&__static_call_return0) +DEFINE_STATIC_CALL_RET0(cond_resched, __cond_resched); +EXPORT_STATIC_CALL_TRAMP(cond_resched); + +# define might_resched_dynamic_enabled __cond_resched +# define might_resched_dynamic_disabled ((void *)&__static_call_return0) +DEFINE_STATIC_CALL_RET0(might_resched, __cond_resched); +EXPORT_STATIC_CALL_TRAMP(might_resched); +# elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY) +static DEFINE_STATIC_KEY_FALSE(sk_dynamic_cond_resched); +int __sched dynamic_cond_resched(void) +{ + if (!static_branch_unlikely(&sk_dynamic_cond_resched)) return 0; -#endif - - return 1; + return __cond_resched(); } +EXPORT_SYMBOL(dynamic_cond_resched); -/** - * available_idle_cpu - is a given CPU idle for enqueuing work. - * @cpu: the CPU in question. - * - * Return: 1 if the CPU is currently idle. 0 otherwise. - */ -int available_idle_cpu(int cpu) +static DEFINE_STATIC_KEY_FALSE(sk_dynamic_might_resched); +int __sched dynamic_might_resched(void) { - if (!idle_cpu(cpu)) + if (!static_branch_unlikely(&sk_dynamic_might_resched)) return 0; - - if (vcpu_is_preempted(cpu)) - return 0; - - return 1; -} - -/** - * idle_task - return the idle task for a given CPU. - * @cpu: the processor in question. - * - * Return: The idle task for the CPU @cpu. - */ -struct task_struct *idle_task(int cpu) -{ - return cpu_rq(cpu)->idle; -} - -/** - * find_process_by_pid - find a process with a matching PID value. - * @pid: the pid in question. - * - * The task of @pid, if found. %NULL otherwise. - */ -static struct task_struct *find_process_by_pid(pid_t pid) -{ - return pid ? find_task_by_vpid(pid) : current; + return __cond_resched(); } +EXPORT_SYMBOL(dynamic_might_resched); +# endif +#endif /* CONFIG_PREEMPT_DYNAMIC */ /* - * sched_setparam() passes in -1 for its policy, to let the functions - * it calls know not to change it. - */ -#define SETPARAM_POLICY -1 - -static void __setscheduler_params(struct task_struct *p, - const struct sched_attr *attr) -{ - int policy = attr->sched_policy; - - if (policy == SETPARAM_POLICY) - policy = p->policy; - - p->policy = policy; - - if (dl_policy(policy)) - __setparam_dl(p, attr); - else if (fair_policy(policy)) - p->static_prio = NICE_TO_PRIO(attr->sched_nice); - - /* - * __sched_setscheduler() ensures attr->sched_priority == 0 when - * !rt_policy. Always setting this ensures that things like - * getparam()/getattr() don't report silly values for !rt tasks. - */ - p->rt_priority = attr->sched_priority; - p->normal_prio = normal_prio(p); - set_load_weight(p, true); -} - -/* Actually do priority change: must hold pi & rq lock. */ -static void __setscheduler(struct rq *rq, struct task_struct *p, - const struct sched_attr *attr, bool keep_boost) -{ - __setscheduler_params(p, attr); - - /* - * Keep a potential priority boosting if called from - * sched_setscheduler(). - */ - p->prio = normal_prio(p); - if (keep_boost) - p->prio = rt_effective_prio(p, p->prio); - - if (dl_prio(p->prio)) - p->sched_class = &dl_sched_class; - else if (rt_prio(p->prio)) - p->sched_class = &rt_sched_class; - else - p->sched_class = &fair_sched_class; -} - -/* - * Check the target process has a UID that matches the current process's: + * __cond_resched_lock() - if a reschedule is pending, drop the given lock, + * call schedule, and on return reacquire the lock. + * + * This works OK both with and without CONFIG_PREEMPTION. We do strange low-level + * operations here to prevent schedule() from being called twice (once via + * spin_unlock(), once by hand). */ -static bool check_same_owner(struct task_struct *p) -{ - const struct cred *cred = current_cred(), *pcred; - bool match; - - rcu_read_lock(); - pcred = __task_cred(p); - match = (uid_eq(cred->euid, pcred->euid) || - uid_eq(cred->euid, pcred->uid)); - rcu_read_unlock(); - return match; -} - -static int __sched_setscheduler(struct task_struct *p, - const struct sched_attr *attr, - bool user, bool pi) +int __cond_resched_lock(spinlock_t *lock) { - int newprio = dl_policy(attr->sched_policy) ? MAX_DL_PRIO - 1 : - MAX_RT_PRIO - 1 - attr->sched_priority; - int retval, oldprio, oldpolicy = -1, queued, running; - int new_effective_prio, policy = attr->sched_policy; - const struct sched_class *prev_class; - struct rq_flags rf; - int reset_on_fork; - int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK; - struct rq *rq; - - /* The pi code expects interrupts enabled */ - BUG_ON(pi && in_interrupt()); -recheck: - /* Double check policy once rq lock held: */ - if (policy < 0) { - reset_on_fork = p->sched_reset_on_fork; - policy = oldpolicy = p->policy; - } else { - reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK); - - if (!valid_policy(policy)) - return -EINVAL; - } - - if (attr->sched_flags & ~(SCHED_FLAG_ALL | SCHED_FLAG_SUGOV)) - return -EINVAL; - - /* - * Valid priorities for SCHED_FIFO and SCHED_RR are - * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL, - * SCHED_BATCH and SCHED_IDLE is 0. - */ - if ((p->mm && attr->sched_priority > MAX_USER_RT_PRIO-1) || - (!p->mm && attr->sched_priority > MAX_RT_PRIO-1)) - return -EINVAL; - if ((dl_policy(policy) && !__checkparam_dl(attr)) || - (rt_policy(policy) != (attr->sched_priority != 0))) - return -EINVAL; - - /* - * Allow unprivileged RT tasks to decrease priority: - */ - if (user && !capable(CAP_SYS_NICE)) { - if (fair_policy(policy)) { - if (attr->sched_nice < task_nice(p) && - !can_nice(p, attr->sched_nice)) - return -EPERM; - } - - if (rt_policy(policy)) { - unsigned long rlim_rtprio = - task_rlimit(p, RLIMIT_RTPRIO); - - /* Can't set/change the rt policy: */ - if (policy != p->policy && !rlim_rtprio) - return -EPERM; - - /* Can't increase priority: */ - if (attr->sched_priority > p->rt_priority && - attr->sched_priority > rlim_rtprio) - return -EPERM; - } - - /* - * Can't set/change SCHED_DEADLINE policy at all for now - * (safest behavior); in the future we would like to allow - * unprivileged DL tasks to increase their relative deadline - * or reduce their runtime (both ways reducing utilization) - */ - if (dl_policy(policy)) - return -EPERM; - - /* - * Treat SCHED_IDLE as nice 20. Only allow a switch to - * SCHED_NORMAL if the RLIMIT_NICE would normally permit it. - */ - if (task_has_idle_policy(p) && !idle_policy(policy)) { - if (!can_nice(p, task_nice(p))) - return -EPERM; - } - - /* Can't change other user's priorities: */ - if (!check_same_owner(p)) - return -EPERM; - - /* Normal users shall not reset the sched_reset_on_fork flag: */ - if (p->sched_reset_on_fork && !reset_on_fork) - return -EPERM; - } - - if (user) { - if (attr->sched_flags & SCHED_FLAG_SUGOV) - return -EINVAL; - - retval = security_task_setscheduler(p); - if (retval) - return retval; - } - - /* - * Make sure no PI-waiters arrive (or leave) while we are - * changing the priority of the task: - * - * To be able to change p->policy safely, the appropriate - * runqueue lock must be held. - */ - rq = task_rq_lock(p, &rf); - update_rq_clock(rq); - - /* - * Changing the policy of the stop threads its a very bad idea: - */ - if (p == rq->stop) { - task_rq_unlock(rq, p, &rf); - return -EINVAL; - } - - /* - * If not changing anything there's no need to proceed further, - * but store a possible modification of reset_on_fork. - */ - if (unlikely(policy == p->policy)) { - if (fair_policy(policy) && attr->sched_nice != task_nice(p)) - goto change; - if (rt_policy(policy) && attr->sched_priority != p->rt_priority) - goto change; - if (dl_policy(policy) && dl_param_changed(p, attr)) - goto change; - - p->sched_reset_on_fork = reset_on_fork; - task_rq_unlock(rq, p, &rf); - return 0; - } -change: - - if (user) { -#ifdef CONFIG_RT_GROUP_SCHED - /* - * Do not allow realtime tasks into groups that have no runtime - * assigned. - */ - if (rt_bandwidth_enabled() && rt_policy(policy) && - task_group(p)->rt_bandwidth.rt_runtime == 0 && - !task_group_is_autogroup(task_group(p))) { - task_rq_unlock(rq, p, &rf); - return -EPERM; - } -#endif -#ifdef CONFIG_SMP - if (dl_bandwidth_enabled() && dl_policy(policy) && - !(attr->sched_flags & SCHED_FLAG_SUGOV)) { - cpumask_t *span = rq->rd->span; - - /* - * Don't allow tasks with an affinity mask smaller than - * the entire root_domain to become SCHED_DEADLINE. We - * will also fail if there's no bandwidth available. - */ - if (!cpumask_subset(span, &p->cpus_allowed) || - rq->rd->dl_bw.bw == 0) { - task_rq_unlock(rq, p, &rf); - return -EPERM; - } - } -#endif - } - - /* Re-check policy now with rq lock held: */ - if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) { - policy = oldpolicy = -1; - task_rq_unlock(rq, p, &rf); - goto recheck; - } - - /* - * If setscheduling to SCHED_DEADLINE (or changing the parameters - * of a SCHED_DEADLINE task) we need to check if enough bandwidth - * is available. - */ - if ((dl_policy(policy) || dl_task(p)) && sched_dl_overflow(p, policy, attr)) { - task_rq_unlock(rq, p, &rf); - return -EBUSY; - } - - p->sched_reset_on_fork = reset_on_fork; - oldprio = p->prio; - - if (pi) { - /* - * Take priority boosted tasks into account. If the new - * effective priority is unchanged, we just store the new - * normal parameters and do not touch the scheduler class and - * the runqueue. This will be done when the task deboost - * itself. - */ - new_effective_prio = rt_effective_prio(p, newprio); - if (new_effective_prio == oldprio) - queue_flags &= ~DEQUEUE_MOVE; - } - - queued = task_on_rq_queued(p); - running = task_current(rq, p); - if (queued) - dequeue_task(rq, p, queue_flags); - if (running) - put_prev_task(rq, p); - - prev_class = p->sched_class; - __setscheduler(rq, p, attr, pi); + int resched = should_resched(PREEMPT_LOCK_OFFSET); + int ret = 0; - if (queued) { - /* - * We enqueue to tail when the priority of a task is - * increased (user space view). - */ - if (oldprio < p->prio) - queue_flags |= ENQUEUE_HEAD; + lockdep_assert_held(lock); - enqueue_task(rq, p, queue_flags); + if (spin_needbreak(lock) || resched) { + spin_unlock(lock); + if (!_cond_resched()) + cpu_relax(); + ret = 1; + spin_lock(lock); } - if (running) - set_curr_task(rq, p); - - check_class_changed(rq, p, prev_class, oldprio); - - /* Avoid rq from going away on us: */ - preempt_disable(); - task_rq_unlock(rq, p, &rf); - - if (pi) - rt_mutex_adjust_pi(p); - - /* Run balance callbacks after we've adjusted the PI chain: */ - balance_callback(rq); - preempt_enable(); - - return 0; + return ret; } +EXPORT_SYMBOL(__cond_resched_lock); -static int _sched_setscheduler(struct task_struct *p, int policy, - const struct sched_param *param, bool check) +int __cond_resched_rwlock_read(rwlock_t *lock) { - struct sched_attr attr = { - .sched_policy = policy, - .sched_priority = param->sched_priority, - .sched_nice = PRIO_TO_NICE(p->static_prio), - }; + int resched = should_resched(PREEMPT_LOCK_OFFSET); + int ret = 0; - /* Fixup the legacy SCHED_RESET_ON_FORK hack. */ - if ((policy != SETPARAM_POLICY) && (policy & SCHED_RESET_ON_FORK)) { - attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK; - policy &= ~SCHED_RESET_ON_FORK; - attr.sched_policy = policy; - } + lockdep_assert_held_read(lock); - return __sched_setscheduler(p, &attr, check, true); -} -/** - * sched_setscheduler - change the scheduling policy and/or RT priority of a thread. - * @p: the task in question. - * @policy: new policy. - * @param: structure containing the new RT priority. - * - * Return: 0 on success. An error code otherwise. - * - * NOTE that the task may be already dead. - */ -int sched_setscheduler(struct task_struct *p, int policy, - const struct sched_param *param) -{ - return _sched_setscheduler(p, policy, param, true); + if (rwlock_needbreak(lock) || resched) { + read_unlock(lock); + if (!_cond_resched()) + cpu_relax(); + ret = 1; + read_lock(lock); + } + return ret; } -EXPORT_SYMBOL_GPL(sched_setscheduler); +EXPORT_SYMBOL(__cond_resched_rwlock_read); -int sched_setattr(struct task_struct *p, const struct sched_attr *attr) +int __cond_resched_rwlock_write(rwlock_t *lock) { - return __sched_setscheduler(p, attr, true, true); -} -EXPORT_SYMBOL_GPL(sched_setattr); + int resched = should_resched(PREEMPT_LOCK_OFFSET); + int ret = 0; -int sched_setattr_nocheck(struct task_struct *p, const struct sched_attr *attr) -{ - return __sched_setscheduler(p, attr, false, true); -} + lockdep_assert_held_write(lock); -/** - * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace. - * @p: the task in question. - * @policy: new policy. - * @param: structure containing the new RT priority. - * - * Just like sched_setscheduler, only don't bother checking if the - * current context has permission. For example, this is needed in - * stop_machine(): we create temporary high priority worker threads, - * but our caller might not have that capability. - * - * Return: 0 on success. An error code otherwise. - */ -int sched_setscheduler_nocheck(struct task_struct *p, int policy, - const struct sched_param *param) -{ - return _sched_setscheduler(p, policy, param, false); + if (rwlock_needbreak(lock) || resched) { + write_unlock(lock); + if (!_cond_resched()) + cpu_relax(); + ret = 1; + write_lock(lock); + } + return ret; } -EXPORT_SYMBOL_GPL(sched_setscheduler_nocheck); +EXPORT_SYMBOL(__cond_resched_rwlock_write); -static int -do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param) -{ - struct sched_param lparam; - struct task_struct *p; - int retval; +#ifdef CONFIG_PREEMPT_DYNAMIC - if (!param || pid < 0) - return -EINVAL; - if (copy_from_user(&lparam, param, sizeof(struct sched_param))) - return -EFAULT; - - rcu_read_lock(); - retval = -ESRCH; - p = find_process_by_pid(pid); - if (p != NULL) - retval = sched_setscheduler(p, policy, &lparam); - rcu_read_unlock(); - - return retval; -} +# ifdef CONFIG_GENERIC_IRQ_ENTRY +# include <linux/irq-entry-common.h> +# endif /* - * Mimics kernel/events/core.c perf_copy_attr(). - */ -static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *attr) -{ - u32 size; - int ret; - - if (!access_ok(uattr, SCHED_ATTR_SIZE_VER0)) - return -EFAULT; - - /* Zero the full structure, so that a short copy will be nice: */ - memset(attr, 0, sizeof(*attr)); - - ret = get_user(size, &uattr->size); - if (ret) - return ret; - - /* Bail out on silly large: */ - if (size > PAGE_SIZE) - goto err_size; - - /* ABI compatibility quirk: */ - if (!size) - size = SCHED_ATTR_SIZE_VER0; - - if (size < SCHED_ATTR_SIZE_VER0) - goto err_size; - - /* - * If we're handed a bigger struct than we know of, - * ensure all the unknown bits are 0 - i.e. new - * user-space does not rely on any kernel feature - * extensions we dont know about yet. - */ - if (size > sizeof(*attr)) { - unsigned char __user *addr; - unsigned char __user *end; - unsigned char val; - - addr = (void __user *)uattr + sizeof(*attr); - end = (void __user *)uattr + size; - - for (; addr < end; addr++) { - ret = get_user(val, addr); - if (ret) - return ret; - if (val) - goto err_size; - } - size = sizeof(*attr); - } - - ret = copy_from_user(attr, uattr, size); - if (ret) - return -EFAULT; - - /* - * XXX: Do we want to be lenient like existing syscalls; or do we want - * to be strict and return an error on out-of-bounds values? - */ - attr->sched_nice = clamp(attr->sched_nice, MIN_NICE, MAX_NICE); - - return 0; - -err_size: - put_user(sizeof(*attr), &uattr->size); - return -E2BIG; -} - -/** - * sys_sched_setscheduler - set/change the scheduler policy and RT priority - * @pid: the pid in question. - * @policy: new policy. - * @param: structure containing the new RT priority. - * - * Return: 0 on success. An error code otherwise. + * SC:cond_resched + * SC:might_resched + * SC:preempt_schedule + * SC:preempt_schedule_notrace + * SC:irqentry_exit_cond_resched + * + * + * NONE: + * cond_resched <- __cond_resched + * might_resched <- RET0 + * preempt_schedule <- NOP + * preempt_schedule_notrace <- NOP + * irqentry_exit_cond_resched <- NOP + * dynamic_preempt_lazy <- false + * + * VOLUNTARY: + * cond_resched <- __cond_resched + * might_resched <- __cond_resched + * preempt_schedule <- NOP + * preempt_schedule_notrace <- NOP + * irqentry_exit_cond_resched <- NOP + * dynamic_preempt_lazy <- false + * + * FULL: + * cond_resched <- RET0 + * might_resched <- RET0 + * preempt_schedule <- preempt_schedule + * preempt_schedule_notrace <- preempt_schedule_notrace + * irqentry_exit_cond_resched <- irqentry_exit_cond_resched + * dynamic_preempt_lazy <- false + * + * LAZY: + * cond_resched <- RET0 + * might_resched <- RET0 + * preempt_schedule <- preempt_schedule + * preempt_schedule_notrace <- preempt_schedule_notrace + * irqentry_exit_cond_resched <- irqentry_exit_cond_resched + * dynamic_preempt_lazy <- true */ -SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy, struct sched_param __user *, param) -{ - if (policy < 0) - return -EINVAL; - return do_sched_setscheduler(pid, policy, param); -} +enum { + preempt_dynamic_undefined = -1, + preempt_dynamic_none, + preempt_dynamic_voluntary, + preempt_dynamic_full, + preempt_dynamic_lazy, +}; -/** - * sys_sched_setparam - set/change the RT priority of a thread - * @pid: the pid in question. - * @param: structure containing the new RT priority. - * - * Return: 0 on success. An error code otherwise. - */ -SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param) -{ - return do_sched_setscheduler(pid, SETPARAM_POLICY, param); -} +int preempt_dynamic_mode = preempt_dynamic_undefined; -/** - * sys_sched_setattr - same as above, but with extended sched_attr - * @pid: the pid in question. - * @uattr: structure containing the extended parameters. - * @flags: for future extension. - */ -SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr, - unsigned int, flags) +int sched_dynamic_mode(const char *str) { - struct sched_attr attr; - struct task_struct *p; - int retval; - - if (!uattr || pid < 0 || flags) - return -EINVAL; - - retval = sched_copy_attr(uattr, &attr); - if (retval) - return retval; - - if ((int)attr.sched_policy < 0) - return -EINVAL; - - rcu_read_lock(); - retval = -ESRCH; - p = find_process_by_pid(pid); - if (p != NULL) - retval = sched_setattr(p, &attr); - rcu_read_unlock(); +# ifndef CONFIG_PREEMPT_RT + if (!strcmp(str, "none")) + return preempt_dynamic_none; - return retval; -} + if (!strcmp(str, "voluntary")) + return preempt_dynamic_voluntary; +# endif -/** - * sys_sched_getscheduler - get the policy (scheduling class) of a thread - * @pid: the pid in question. - * - * Return: On success, the policy of the thread. Otherwise, a negative error - * code. - */ -SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid) -{ - struct task_struct *p; - int retval; + if (!strcmp(str, "full")) + return preempt_dynamic_full; - if (pid < 0) - return -EINVAL; +# ifdef CONFIG_ARCH_HAS_PREEMPT_LAZY + if (!strcmp(str, "lazy")) + return preempt_dynamic_lazy; +# endif - retval = -ESRCH; - rcu_read_lock(); - p = find_process_by_pid(pid); - if (p) { - retval = security_task_getscheduler(p); - if (!retval) - retval = p->policy - | (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0); - } - rcu_read_unlock(); - return retval; + return -EINVAL; } -/** - * sys_sched_getparam - get the RT priority of a thread - * @pid: the pid in question. - * @param: structure containing the RT priority. - * - * Return: On success, 0 and the RT priority is in @param. Otherwise, an error - * code. - */ -SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param) -{ - struct sched_param lp = { .sched_priority = 0 }; - struct task_struct *p; - int retval; - - if (!param || pid < 0) - return -EINVAL; - - rcu_read_lock(); - p = find_process_by_pid(pid); - retval = -ESRCH; - if (!p) - goto out_unlock; +# define preempt_dynamic_key_enable(f) static_key_enable(&sk_dynamic_##f.key) +# define preempt_dynamic_key_disable(f) static_key_disable(&sk_dynamic_##f.key) - retval = security_task_getscheduler(p); - if (retval) - goto out_unlock; +# if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL) +# define preempt_dynamic_enable(f) static_call_update(f, f##_dynamic_enabled) +# define preempt_dynamic_disable(f) static_call_update(f, f##_dynamic_disabled) +# elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY) +# define preempt_dynamic_enable(f) preempt_dynamic_key_enable(f) +# define preempt_dynamic_disable(f) preempt_dynamic_key_disable(f) +# else +# error "Unsupported PREEMPT_DYNAMIC mechanism" +# endif - if (task_has_rt_policy(p)) - lp.sched_priority = p->rt_priority; - rcu_read_unlock(); - - /* - * This one might sleep, we cannot do it with a spinlock held ... - */ - retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0; - - return retval; - -out_unlock: - rcu_read_unlock(); - return retval; -} +static DEFINE_MUTEX(sched_dynamic_mutex); -static int sched_read_attr(struct sched_attr __user *uattr, - struct sched_attr *attr, - unsigned int usize) +static void __sched_dynamic_update(int mode) { - int ret; - - if (!access_ok(uattr, usize)) - return -EFAULT; - /* - * If we're handed a smaller struct than we know of, - * ensure all the unknown bits are 0 - i.e. old - * user-space does not get uncomplete information. + * Avoid {NONE,VOLUNTARY} -> FULL transitions from ever ending up in + * the ZERO state, which is invalid. */ - if (usize < sizeof(*attr)) { - unsigned char *addr; - unsigned char *end; + preempt_dynamic_enable(cond_resched); + preempt_dynamic_enable(might_resched); + preempt_dynamic_enable(preempt_schedule); + preempt_dynamic_enable(preempt_schedule_notrace); + preempt_dynamic_enable(irqentry_exit_cond_resched); + preempt_dynamic_key_disable(preempt_lazy); + + switch (mode) { + case preempt_dynamic_none: + preempt_dynamic_enable(cond_resched); + preempt_dynamic_disable(might_resched); + preempt_dynamic_disable(preempt_schedule); + preempt_dynamic_disable(preempt_schedule_notrace); + preempt_dynamic_disable(irqentry_exit_cond_resched); + preempt_dynamic_key_disable(preempt_lazy); + if (mode != preempt_dynamic_mode) + pr_info("Dynamic Preempt: none\n"); + break; - addr = (void *)attr + usize; - end = (void *)attr + sizeof(*attr); + case preempt_dynamic_voluntary: + preempt_dynamic_enable(cond_resched); + preempt_dynamic_enable(might_resched); + preempt_dynamic_disable(preempt_schedule); + preempt_dynamic_disable(preempt_schedule_notrace); + preempt_dynamic_disable(irqentry_exit_cond_resched); + preempt_dynamic_key_disable(preempt_lazy); + if (mode != preempt_dynamic_mode) + pr_info("Dynamic Preempt: voluntary\n"); + break; - for (; addr < end; addr++) { - if (*addr) - return -EFBIG; - } + case preempt_dynamic_full: + preempt_dynamic_disable(cond_resched); + preempt_dynamic_disable(might_resched); + preempt_dynamic_enable(preempt_schedule); + preempt_dynamic_enable(preempt_schedule_notrace); + preempt_dynamic_enable(irqentry_exit_cond_resched); + preempt_dynamic_key_disable(preempt_lazy); + if (mode != preempt_dynamic_mode) + pr_info("Dynamic Preempt: full\n"); + break; - attr->size = usize; + case preempt_dynamic_lazy: + preempt_dynamic_disable(cond_resched); + preempt_dynamic_disable(might_resched); + preempt_dynamic_enable(preempt_schedule); + preempt_dynamic_enable(preempt_schedule_notrace); + preempt_dynamic_enable(irqentry_exit_cond_resched); + preempt_dynamic_key_enable(preempt_lazy); + if (mode != preempt_dynamic_mode) + pr_info("Dynamic Preempt: lazy\n"); + break; } - ret = copy_to_user(uattr, attr, attr->size); - if (ret) - return -EFAULT; - - return 0; + preempt_dynamic_mode = mode; } -/** - * sys_sched_getattr - similar to sched_getparam, but with sched_attr - * @pid: the pid in question. - * @uattr: structure containing the extended parameters. - * @size: sizeof(attr) for fwd/bwd comp. - * @flags: for future extension. - */ -SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr, - unsigned int, size, unsigned int, flags) +void sched_dynamic_update(int mode) { - struct sched_attr attr = { - .size = sizeof(struct sched_attr), - }; - struct task_struct *p; - int retval; - - if (!uattr || pid < 0 || size > PAGE_SIZE || - size < SCHED_ATTR_SIZE_VER0 || flags) - return -EINVAL; - - rcu_read_lock(); - p = find_process_by_pid(pid); - retval = -ESRCH; - if (!p) - goto out_unlock; - - retval = security_task_getscheduler(p); - if (retval) - goto out_unlock; - - attr.sched_policy = p->policy; - if (p->sched_reset_on_fork) - attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK; - if (task_has_dl_policy(p)) - __getparam_dl(p, &attr); - else if (task_has_rt_policy(p)) - attr.sched_priority = p->rt_priority; - else - attr.sched_nice = task_nice(p); - - rcu_read_unlock(); - - retval = sched_read_attr(uattr, &attr, size); - return retval; - -out_unlock: - rcu_read_unlock(); - return retval; + mutex_lock(&sched_dynamic_mutex); + __sched_dynamic_update(mode); + mutex_unlock(&sched_dynamic_mutex); } -long sched_setaffinity(pid_t pid, const struct cpumask *in_mask) +static int __init setup_preempt_mode(char *str) { - cpumask_var_t cpus_allowed, new_mask; - struct task_struct *p; - int retval; - - rcu_read_lock(); - - p = find_process_by_pid(pid); - if (!p) { - rcu_read_unlock(); - return -ESRCH; - } - - /* Prevent p going away */ - get_task_struct(p); - rcu_read_unlock(); - - if (p->flags & PF_NO_SETAFFINITY) { - retval = -EINVAL; - goto out_put_task; - } - if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) { - retval = -ENOMEM; - goto out_put_task; - } - if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) { - retval = -ENOMEM; - goto out_free_cpus_allowed; - } - retval = -EPERM; - if (!check_same_owner(p)) { - rcu_read_lock(); - if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) { - rcu_read_unlock(); - goto out_free_new_mask; - } - rcu_read_unlock(); - } - - retval = security_task_setscheduler(p); - if (retval) - goto out_free_new_mask; - - - cpuset_cpus_allowed(p, cpus_allowed); - cpumask_and(new_mask, in_mask, cpus_allowed); - - /* - * Since bandwidth control happens on root_domain basis, - * if admission test is enabled, we only admit -deadline - * tasks allowed to run on all the CPUs in the task's - * root_domain. - */ -#ifdef CONFIG_SMP - if (task_has_dl_policy(p) && dl_bandwidth_enabled()) { - rcu_read_lock(); - if (!cpumask_subset(task_rq(p)->rd->span, new_mask)) { - retval = -EBUSY; - rcu_read_unlock(); - goto out_free_new_mask; - } - rcu_read_unlock(); - } -#endif -again: - retval = __set_cpus_allowed_ptr(p, new_mask, true); - - if (!retval) { - cpuset_cpus_allowed(p, cpus_allowed); - if (!cpumask_subset(new_mask, cpus_allowed)) { - /* - * We must have raced with a concurrent cpuset - * update. Just reset the cpus_allowed to the - * cpuset's cpus_allowed - */ - cpumask_copy(new_mask, cpus_allowed); - goto again; - } + int mode = sched_dynamic_mode(str); + if (mode < 0) { + pr_warn("Dynamic Preempt: unsupported mode: %s\n", str); + return 0; } -out_free_new_mask: - free_cpumask_var(new_mask); -out_free_cpus_allowed: - free_cpumask_var(cpus_allowed); -out_put_task: - put_task_struct(p); - return retval; -} - -static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len, - struct cpumask *new_mask) -{ - if (len < cpumask_size()) - cpumask_clear(new_mask); - else if (len > cpumask_size()) - len = cpumask_size(); - - return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0; -} - -/** - * sys_sched_setaffinity - set the CPU affinity of a process - * @pid: pid of the process - * @len: length in bytes of the bitmask pointed to by user_mask_ptr - * @user_mask_ptr: user-space pointer to the new CPU mask - * - * Return: 0 on success. An error code otherwise. - */ -SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len, - unsigned long __user *, user_mask_ptr) -{ - cpumask_var_t new_mask; - int retval; - - if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) - return -ENOMEM; - - retval = get_user_cpu_mask(user_mask_ptr, len, new_mask); - if (retval == 0) - retval = sched_setaffinity(pid, new_mask); - free_cpumask_var(new_mask); - return retval; -} - -long sched_getaffinity(pid_t pid, struct cpumask *mask) -{ - struct task_struct *p; - unsigned long flags; - int retval; - - rcu_read_lock(); - - retval = -ESRCH; - p = find_process_by_pid(pid); - if (!p) - goto out_unlock; - retval = security_task_getscheduler(p); - if (retval) - goto out_unlock; - - raw_spin_lock_irqsave(&p->pi_lock, flags); - cpumask_and(mask, &p->cpus_allowed, cpu_active_mask); - raw_spin_unlock_irqrestore(&p->pi_lock, flags); - -out_unlock: - rcu_read_unlock(); - - return retval; + sched_dynamic_update(mode); + return 1; } +__setup("preempt=", setup_preempt_mode); -/** - * sys_sched_getaffinity - get the CPU affinity of a process - * @pid: pid of the process - * @len: length in bytes of the bitmask pointed to by user_mask_ptr - * @user_mask_ptr: user-space pointer to hold the current CPU mask - * - * Return: size of CPU mask copied to user_mask_ptr on success. An - * error code otherwise. - */ -SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len, - unsigned long __user *, user_mask_ptr) +static void __init preempt_dynamic_init(void) { - int ret; - cpumask_var_t mask; - - if ((len * BITS_PER_BYTE) < nr_cpu_ids) - return -EINVAL; - if (len & (sizeof(unsigned long)-1)) - return -EINVAL; - - if (!alloc_cpumask_var(&mask, GFP_KERNEL)) - return -ENOMEM; - - ret = sched_getaffinity(pid, mask); - if (ret == 0) { - unsigned int retlen = min(len, cpumask_size()); - - if (copy_to_user(user_mask_ptr, mask, retlen)) - ret = -EFAULT; - else - ret = retlen; + if (preempt_dynamic_mode == preempt_dynamic_undefined) { + if (IS_ENABLED(CONFIG_PREEMPT_NONE)) { + sched_dynamic_update(preempt_dynamic_none); + } else if (IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY)) { + sched_dynamic_update(preempt_dynamic_voluntary); + } else if (IS_ENABLED(CONFIG_PREEMPT_LAZY)) { + sched_dynamic_update(preempt_dynamic_lazy); + } else { + /* Default static call setting, nothing to do */ + WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPT)); + preempt_dynamic_mode = preempt_dynamic_full; + pr_info("Dynamic Preempt: full\n"); + } } - free_cpumask_var(mask); - - return ret; } -/** - * sys_sched_yield - yield the current processor to other threads. - * - * This function yields the current CPU to other tasks. If there are no - * other threads running on this CPU then this function will return. - * - * Return: 0. - */ -static void do_sched_yield(void) -{ - struct rq_flags rf; - struct rq *rq; - - rq = this_rq_lock_irq(&rf); +# define PREEMPT_MODEL_ACCESSOR(mode) \ + bool preempt_model_##mode(void) \ + { \ + WARN_ON_ONCE(preempt_dynamic_mode == preempt_dynamic_undefined); \ + return preempt_dynamic_mode == preempt_dynamic_##mode; \ + } \ + EXPORT_SYMBOL_GPL(preempt_model_##mode) - schedstat_inc(rq->yld_count); - current->sched_class->yield_task(rq); +PREEMPT_MODEL_ACCESSOR(none); +PREEMPT_MODEL_ACCESSOR(voluntary); +PREEMPT_MODEL_ACCESSOR(full); +PREEMPT_MODEL_ACCESSOR(lazy); - /* - * Since we are going to call schedule() anyway, there's - * no need to preempt or enable interrupts: - */ - preempt_disable(); - rq_unlock(rq, &rf); - sched_preempt_enable_no_resched(); - - schedule(); -} - -SYSCALL_DEFINE0(sched_yield) -{ - do_sched_yield(); - return 0; -} +#else /* !CONFIG_PREEMPT_DYNAMIC: */ -#ifndef CONFIG_PREEMPT -int __sched _cond_resched(void) -{ - if (should_resched(0)) { - preempt_schedule_common(); - return 1; - } - rcu_all_qs(); - return 0; -} -EXPORT_SYMBOL(_cond_resched); -#endif +#define preempt_dynamic_mode -1 -/* - * __cond_resched_lock() - if a reschedule is pending, drop the given lock, - * call schedule, and on return reacquire the lock. - * - * This works OK both with and without CONFIG_PREEMPT. We do strange low-level - * operations here to prevent schedule() from being called twice (once via - * spin_unlock(), once by hand). - */ -int __cond_resched_lock(spinlock_t *lock) -{ - int resched = should_resched(PREEMPT_LOCK_OFFSET); - int ret = 0; +static inline void preempt_dynamic_init(void) { } - lockdep_assert_held(lock); +#endif /* CONFIG_PREEMPT_DYNAMIC */ - if (spin_needbreak(lock) || resched) { - spin_unlock(lock); - if (resched) - preempt_schedule_common(); - else - cpu_relax(); - ret = 1; - spin_lock(lock); - } - return ret; -} -EXPORT_SYMBOL(__cond_resched_lock); - -/** - * yield - yield the current processor to other threads. - * - * Do not ever use this function, there's a 99% chance you're doing it wrong. - * - * The scheduler is at all times free to pick the calling task as the most - * eligible task to run, if removing the yield() call from your code breaks - * it, its already broken. - * - * Typical broken usage is: - * - * while (!event) - * yield(); - * - * where one assumes that yield() will let 'the other' process run that will - * make event true. If the current task is a SCHED_FIFO task that will never - * happen. Never use yield() as a progress guarantee!! - * - * If you want to use yield() to wait for something, use wait_event(). - * If you want to use yield() to be 'nice' for others, use cond_resched(). - * If you still want to use yield(), do not! - */ -void __sched yield(void) -{ - set_current_state(TASK_RUNNING); - do_sched_yield(); -} -EXPORT_SYMBOL(yield); +const char *preempt_modes[] = { + "none", "voluntary", "full", "lazy", NULL, +}; -/** - * yield_to - yield the current processor to another thread in - * your thread group, or accelerate that thread toward the - * processor it's on. - * @p: target task - * @preempt: whether task preemption is allowed or not - * - * It's the caller's job to ensure that the target task struct - * can't go away on us before we can do any checks. - * - * Return: - * true (>0) if we indeed boosted the target task. - * false (0) if we failed to boost the target. - * -ESRCH if there's no task to yield to. - */ -int __sched yield_to(struct task_struct *p, bool preempt) +const char *preempt_model_str(void) { - struct task_struct *curr = current; - struct rq *rq, *p_rq; - unsigned long flags; - int yielded = 0; + bool brace = IS_ENABLED(CONFIG_PREEMPT_RT) && + (IS_ENABLED(CONFIG_PREEMPT_DYNAMIC) || + IS_ENABLED(CONFIG_PREEMPT_LAZY)); + static char buf[128]; - local_irq_save(flags); - rq = this_rq(); - -again: - p_rq = task_rq(p); - /* - * If we're the only runnable task on the rq and target rq also - * has only one task, there's absolutely no point in yielding. - */ - if (rq->nr_running == 1 && p_rq->nr_running == 1) { - yielded = -ESRCH; - goto out_irq; - } + if (IS_ENABLED(CONFIG_PREEMPT_BUILD)) { + struct seq_buf s; - double_rq_lock(rq, p_rq); - if (task_rq(p) != p_rq) { - double_rq_unlock(rq, p_rq); - goto again; - } + seq_buf_init(&s, buf, sizeof(buf)); + seq_buf_puts(&s, "PREEMPT"); - if (!curr->sched_class->yield_to_task) - goto out_unlock; + if (IS_ENABLED(CONFIG_PREEMPT_RT)) + seq_buf_printf(&s, "%sRT%s", + brace ? "_{" : "_", + brace ? "," : ""); - if (curr->sched_class != p->sched_class) - goto out_unlock; + if (IS_ENABLED(CONFIG_PREEMPT_DYNAMIC)) { + seq_buf_printf(&s, "(%s)%s", + preempt_dynamic_mode >= 0 ? + preempt_modes[preempt_dynamic_mode] : "undef", + brace ? "}" : ""); + return seq_buf_str(&s); + } - if (task_running(p_rq, p) || p->state) - goto out_unlock; + if (IS_ENABLED(CONFIG_PREEMPT_LAZY)) { + seq_buf_printf(&s, "LAZY%s", + brace ? "}" : ""); + return seq_buf_str(&s); + } - yielded = curr->sched_class->yield_to_task(rq, p, preempt); - if (yielded) { - schedstat_inc(rq->yld_count); - /* - * Make p's CPU reschedule; pick_next_entity takes care of - * fairness. - */ - if (preempt && rq != p_rq) - resched_curr(p_rq); + return seq_buf_str(&s); } -out_unlock: - double_rq_unlock(rq, p_rq); -out_irq: - local_irq_restore(flags); - - if (yielded > 0) - schedule(); + if (IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY_BUILD)) + return "VOLUNTARY"; - return yielded; + return "NONE"; } -EXPORT_SYMBOL_GPL(yield_to); int io_schedule_prepare(void) { int old_iowait = current->in_iowait; current->in_iowait = 1; - blk_schedule_flush_plug(current); - + blk_flush_plug(current->plug, true); return old_iowait; } @@ -5129,7 +7781,7 @@ long __sched io_schedule_timeout(long timeout) } EXPORT_SYMBOL(io_schedule_timeout); -void io_schedule(void) +void __sched io_schedule(void) { int token; @@ -5139,158 +7791,32 @@ void io_schedule(void) } EXPORT_SYMBOL(io_schedule); -/** - * sys_sched_get_priority_max - return maximum RT priority. - * @policy: scheduling class. - * - * Return: On success, this syscall returns the maximum - * rt_priority that can be used by a given scheduling class. - * On failure, a negative error code is returned. - */ -SYSCALL_DEFINE1(sched_get_priority_max, int, policy) -{ - int ret = -EINVAL; - - switch (policy) { - case SCHED_FIFO: - case SCHED_RR: - ret = MAX_USER_RT_PRIO-1; - break; - case SCHED_DEADLINE: - case SCHED_NORMAL: - case SCHED_BATCH: - case SCHED_IDLE: - ret = 0; - break; - } - return ret; -} - -/** - * sys_sched_get_priority_min - return minimum RT priority. - * @policy: scheduling class. - * - * Return: On success, this syscall returns the minimum - * rt_priority that can be used by a given scheduling class. - * On failure, a negative error code is returned. - */ -SYSCALL_DEFINE1(sched_get_priority_min, int, policy) -{ - int ret = -EINVAL; - - switch (policy) { - case SCHED_FIFO: - case SCHED_RR: - ret = 1; - break; - case SCHED_DEADLINE: - case SCHED_NORMAL: - case SCHED_BATCH: - case SCHED_IDLE: - ret = 0; - } - return ret; -} - -static int sched_rr_get_interval(pid_t pid, struct timespec64 *t) -{ - struct task_struct *p; - unsigned int time_slice; - struct rq_flags rf; - struct rq *rq; - int retval; - - if (pid < 0) - return -EINVAL; - - retval = -ESRCH; - rcu_read_lock(); - p = find_process_by_pid(pid); - if (!p) - goto out_unlock; - - retval = security_task_getscheduler(p); - if (retval) - goto out_unlock; - - rq = task_rq_lock(p, &rf); - time_slice = 0; - if (p->sched_class->get_rr_interval) - time_slice = p->sched_class->get_rr_interval(rq, p); - task_rq_unlock(rq, p, &rf); - - rcu_read_unlock(); - jiffies_to_timespec64(time_slice, t); - return 0; - -out_unlock: - rcu_read_unlock(); - return retval; -} - -/** - * sys_sched_rr_get_interval - return the default timeslice of a process. - * @pid: pid of the process. - * @interval: userspace pointer to the timeslice value. - * - * this syscall writes the default timeslice value of a given process - * into the user-space timespec buffer. A value of '0' means infinity. - * - * Return: On success, 0 and the timeslice is in @interval. Otherwise, - * an error code. - */ -SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid, - struct __kernel_timespec __user *, interval) -{ - struct timespec64 t; - int retval = sched_rr_get_interval(pid, &t); - - if (retval == 0) - retval = put_timespec64(&t, interval); - - return retval; -} - -#ifdef CONFIG_COMPAT_32BIT_TIME -COMPAT_SYSCALL_DEFINE2(sched_rr_get_interval, - compat_pid_t, pid, - struct old_timespec32 __user *, interval) -{ - struct timespec64 t; - int retval = sched_rr_get_interval(pid, &t); - - if (retval == 0) - retval = put_old_timespec32(&t, interval); - return retval; -} -#endif - void sched_show_task(struct task_struct *p) { - unsigned long free = 0; + unsigned long free; int ppid; if (!try_get_task_stack(p)) return; - printk(KERN_INFO "%-15.15s %c", p->comm, task_state_to_char(p)); + pr_info("task:%-15.15s state:%c", p->comm, task_state_to_char(p)); - if (p->state == TASK_RUNNING) - printk(KERN_CONT " running task "); -#ifdef CONFIG_DEBUG_STACK_USAGE + if (task_is_running(p)) + pr_cont(" running task "); free = stack_not_used(p); -#endif ppid = 0; rcu_read_lock(); if (pid_alive(p)) ppid = task_pid_nr(rcu_dereference(p->real_parent)); rcu_read_unlock(); - printk(KERN_CONT "%5lu %5d %6d 0x%08lx\n", free, - task_pid_nr(p), ppid, - (unsigned long)task_thread_info(p)->flags); + pr_cont(" stack:%-5lu pid:%-5d tgid:%-5d ppid:%-6d task_flags:0x%04x flags:0x%08lx\n", + free, task_pid_nr(p), task_tgid_nr(p), + ppid, p->flags, read_task_thread_flags(p)); print_worker_info(KERN_INFO, p); - show_stack(p, NULL); + print_stop_info(KERN_INFO, p); + print_scx_info(KERN_INFO, p); + show_stack(p, NULL, KERN_INFO); put_task_stack(p); } EXPORT_SYMBOL_GPL(sched_show_task); @@ -5298,36 +7824,31 @@ EXPORT_SYMBOL_GPL(sched_show_task); static inline bool state_filter_match(unsigned long state_filter, struct task_struct *p) { + unsigned int state = READ_ONCE(p->__state); + /* no filter, everything matches */ if (!state_filter) return true; /* filter, but doesn't match */ - if (!(p->state & state_filter)) + if (!(state & state_filter)) return false; /* * When looking for TASK_UNINTERRUPTIBLE skip TASK_IDLE (allows * TASK_KILLABLE). */ - if (state_filter == TASK_UNINTERRUPTIBLE && p->state == TASK_IDLE) + if (state_filter == TASK_UNINTERRUPTIBLE && (state & TASK_NOLOAD)) return false; return true; } -void show_state_filter(unsigned long state_filter) +void show_state_filter(unsigned int state_filter) { struct task_struct *g, *p; -#if BITS_PER_LONG == 32 - printk(KERN_INFO - " task PC stack pid father\n"); -#else - printk(KERN_INFO - " task PC stack pid father\n"); -#endif rcu_read_lock(); for_each_process_thread(g, p) { /* @@ -5343,10 +7864,9 @@ void show_state_filter(unsigned long state_filter) sched_show_task(p); } -#ifdef CONFIG_SCHED_DEBUG if (!state_filter) sysrq_sched_debug_show(); -#endif + rcu_read_unlock(); /* * Only show locks if all tasks are dumped: @@ -5363,30 +7883,32 @@ void show_state_filter(unsigned long state_filter) * NOTE: this function does not set the idle thread's NEED_RESCHED * flag, to make booting more robust. */ -void init_idle(struct task_struct *idle, int cpu) +void __init init_idle(struct task_struct *idle, int cpu) { + struct affinity_context ac = (struct affinity_context) { + .new_mask = cpumask_of(cpu), + .flags = 0, + }; struct rq *rq = cpu_rq(cpu); unsigned long flags; raw_spin_lock_irqsave(&idle->pi_lock, flags); - raw_spin_lock(&rq->lock); + raw_spin_rq_lock(rq); - __sched_fork(0, idle); - idle->state = TASK_RUNNING; + idle->__state = TASK_RUNNING; idle->se.exec_start = sched_clock(); - idle->flags |= PF_IDLE; - - kasan_unpoison_task_stack(idle); + /* + * PF_KTHREAD should already be set at this point; regardless, make it + * look like a proper per-CPU kthread. + */ + idle->flags |= PF_KTHREAD | PF_NO_SETAFFINITY; + kthread_set_per_cpu(idle, cpu); -#ifdef CONFIG_SMP /* - * Its possible that init_idle() gets called multiple times on a task, - * in that case do_set_cpus_allowed() will not do the right thing. - * - * And since this is boot we can forgo the serialization. + * No validation and serialization required at boot time and for + * setting up the idle tasks of not yet online CPUs. */ - set_cpus_allowed_common(idle, cpumask_of(cpu)); -#endif + set_cpus_allowed_common(idle, &ac); /* * We're having a chicken and egg problem, even though we are * holding rq->lock, the CPU isn't yet set to this CPU so the @@ -5401,12 +7923,12 @@ void init_idle(struct task_struct *idle, int cpu) __set_task_cpu(idle, cpu); rcu_read_unlock(); - rq->curr = rq->idle = idle; + rq->idle = idle; + rq_set_donor(rq, idle); + rcu_assign_pointer(rq->curr, idle); idle->on_rq = TASK_ON_RQ_QUEUED; -#ifdef CONFIG_SMP idle->on_cpu = 1; -#endif - raw_spin_unlock(&rq->lock); + raw_spin_rq_unlock(rq); raw_spin_unlock_irqrestore(&idle->pi_lock, flags); /* Set the preempt count _outside_ the spinlocks! */ @@ -5418,19 +7940,15 @@ void init_idle(struct task_struct *idle, int cpu) idle->sched_class = &idle_sched_class; ftrace_graph_init_idle_task(idle, cpu); vtime_init_idle(idle, cpu); -#ifdef CONFIG_SMP sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu); -#endif } -#ifdef CONFIG_SMP - int cpuset_cpumask_can_shrink(const struct cpumask *cur, const struct cpumask *trial) { int ret = 1; - if (!cpumask_weight(cur)) + if (cpumask_empty(cur)) return ret; ret = dl_cpuset_cpumask_can_shrink(cur, trial); @@ -5438,8 +7956,7 @@ int cpuset_cpumask_can_shrink(const struct cpumask *cur, return ret; } -int task_can_attach(struct task_struct *p, - const struct cpumask *cs_cpus_allowed) +int task_can_attach(struct task_struct *p) { int ret = 0; @@ -5450,18 +7967,11 @@ int task_can_attach(struct task_struct *p, * allowed nodes is unnecessary. Thus, cpusets are not * applicable for such threads. This prevents checking for * success of set_cpus_allowed_ptr() on all attached tasks - * before cpus_allowed may be changed. + * before cpus_mask may be changed. */ - if (p->flags & PF_NO_SETAFFINITY) { + if (p->flags & PF_NO_SETAFFINITY) ret = -EINVAL; - goto out; - } - - if (dl_task(p) && !cpumask_intersects(task_rq(p)->rd->span, - cs_cpus_allowed)) - ret = dl_task_can_attach(p, cs_cpus_allowed); -out: return ret; } @@ -5477,7 +7987,7 @@ int migrate_task_to(struct task_struct *p, int target_cpu) if (curr_cpu == target_cpu) return 0; - if (!cpumask_test_cpu(target_cpu, &p->cpus_allowed)) + if (!cpumask_test_cpu(target_cpu, p->cpus_ptr)) return -EINVAL; /* TODO: This is not properly updating schedstats */ @@ -5492,166 +8002,177 @@ int migrate_task_to(struct task_struct *p, int target_cpu) */ void sched_setnuma(struct task_struct *p, int nid) { - bool queued, running; - struct rq_flags rf; - struct rq *rq; - - rq = task_rq_lock(p, &rf); - queued = task_on_rq_queued(p); - running = task_current(rq, p); - - if (queued) - dequeue_task(rq, p, DEQUEUE_SAVE); - if (running) - put_prev_task(rq, p); - - p->numa_preferred_nid = nid; - - if (queued) - enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK); - if (running) - set_curr_task(rq, p); - task_rq_unlock(rq, p, &rf); + guard(task_rq_lock)(p); + scoped_guard (sched_change, p, DEQUEUE_SAVE) + p->numa_preferred_nid = nid; } #endif /* CONFIG_NUMA_BALANCING */ #ifdef CONFIG_HOTPLUG_CPU /* - * Ensure that the idle task is using init_mm right before its CPU goes - * offline. + * Invoked on the outgoing CPU in context of the CPU hotplug thread + * after ensuring that there are no user space tasks left on the CPU. + * + * If there is a lazy mm in use on the hotplug thread, drop it and + * switch to init_mm. + * + * The reference count on init_mm is dropped in finish_cpu(). */ -void idle_task_exit(void) +static void sched_force_init_mm(void) { struct mm_struct *mm = current->active_mm; - BUG_ON(cpu_online(smp_processor_id())); - if (mm != &init_mm) { - switch_mm(mm, &init_mm, current); + mmgrab_lazy_tlb(&init_mm); + local_irq_disable(); current->active_mm = &init_mm; + switch_mm_irqs_off(mm, &init_mm, current); + local_irq_enable(); finish_arch_post_lock_switch(); + mmdrop_lazy_tlb(mm); } - mmdrop(mm); -} -/* - * Since this CPU is going 'away' for a while, fold any nr_active delta - * we might have. Assumes we're called after migrate_tasks() so that the - * nr_active count is stable. We need to take the teardown thread which - * is calling this into account, so we hand in adjust = 1 to the load - * calculation. - * - * Also see the comment "Global load-average calculations". - */ -static void calc_load_migrate(struct rq *rq) -{ - long delta = calc_load_fold_active(rq, 1); - if (delta) - atomic_long_add(delta, &calc_load_tasks); + /* finish_cpu(), as ran on the BP, will clean up the active_mm state */ } -static void put_prev_task_fake(struct rq *rq, struct task_struct *prev) +static int __balance_push_cpu_stop(void *arg) { -} + struct task_struct *p = arg; + struct rq *rq = this_rq(); + struct rq_flags rf; + int cpu; -static const struct sched_class fake_sched_class = { - .put_prev_task = put_prev_task_fake, -}; + scoped_guard (raw_spinlock_irq, &p->pi_lock) { + cpu = select_fallback_rq(rq->cpu, p); -static struct task_struct fake_task = { - /* - * Avoid pull_{rt,dl}_task() - */ - .prio = MAX_PRIO + 1, - .sched_class = &fake_sched_class, -}; + rq_lock(rq, &rf); + update_rq_clock(rq); + if (task_rq(p) == rq && task_on_rq_queued(p)) + rq = __migrate_task(rq, &rf, p, cpu); + rq_unlock(rq, &rf); + } + + put_task_struct(p); + + return 0; +} + +static DEFINE_PER_CPU(struct cpu_stop_work, push_work); /* - * Migrate all tasks from the rq, sleeping tasks will be migrated by - * try_to_wake_up()->select_task_rq(). + * Ensure we only run per-cpu kthreads once the CPU goes !active. * - * Called with rq->lock held even though we'er in stop_machine() and - * there's no concurrency possible, we hold the required locks anyway - * because of lock validation efforts. + * This is enabled below SCHED_AP_ACTIVE; when !cpu_active(), but only + * effective when the hotplug motion is down. */ -static void migrate_tasks(struct rq *dead_rq, struct rq_flags *rf) +static void balance_push(struct rq *rq) { - struct rq *rq = dead_rq; - struct task_struct *next, *stop = rq->stop; - struct rq_flags orf = *rf; - int dest_cpu; + struct task_struct *push_task = rq->curr; + + lockdep_assert_rq_held(rq); /* - * Fudge the rq selection such that the below task selection loop - * doesn't get stuck on the currently eligible stop task. - * - * We're currently inside stop_machine() and the rq is either stuck - * in the stop_machine_cpu_stop() loop, or we're executing this code, - * either way we should never end up calling schedule() until we're - * done here. + * Ensure the thing is persistent until balance_push_set(.on = false); */ - rq->stop = NULL; + rq->balance_callback = &balance_push_callback; /* - * put_prev_task() and pick_next_task() sched - * class method both need to have an up-to-date - * value of rq->clock[_task] + * Only active while going offline and when invoked on the outgoing + * CPU. */ - update_rq_clock(rq); - - for (;;) { - /* - * There's this thread running, bail when that's the only - * remaining thread: - */ - if (rq->nr_running == 1) - break; + if (!cpu_dying(rq->cpu) || rq != this_rq()) + return; - /* - * pick_next_task() assumes pinned rq->lock: - */ - next = pick_next_task(rq, &fake_task, rf); - BUG_ON(!next); - put_prev_task(rq, next); + /* + * Both the cpu-hotplug and stop task are in this case and are + * required to complete the hotplug process. + */ + if (kthread_is_per_cpu(push_task) || + is_migration_disabled(push_task)) { /* - * Rules for changing task_struct::cpus_allowed are holding - * both pi_lock and rq->lock, such that holding either - * stabilizes the mask. + * If this is the idle task on the outgoing CPU try to wake + * up the hotplug control thread which might wait for the + * last task to vanish. The rcuwait_active() check is + * accurate here because the waiter is pinned on this CPU + * and can't obviously be running in parallel. * - * Drop rq->lock is not quite as disastrous as it usually is - * because !cpu_active at this point, which means load-balance - * will not interfere. Also, stop-machine. + * On RT kernels this also has to check whether there are + * pinned and scheduled out tasks on the runqueue. They + * need to leave the migrate disabled section first. */ - rq_unlock(rq, rf); - raw_spin_lock(&next->pi_lock); - rq_relock(rq, rf); - - /* - * Since we're inside stop-machine, _nothing_ should have - * changed the task, WARN if weird stuff happened, because in - * that case the above rq->lock drop is a fail too. - */ - if (WARN_ON(task_rq(next) != rq || !task_on_rq_queued(next))) { - raw_spin_unlock(&next->pi_lock); - continue; + if (!rq->nr_running && !rq_has_pinned_tasks(rq) && + rcuwait_active(&rq->hotplug_wait)) { + raw_spin_rq_unlock(rq); + rcuwait_wake_up(&rq->hotplug_wait); + raw_spin_rq_lock(rq); } + return; + } - /* Find suitable destination for @next, with force if needed. */ - dest_cpu = select_fallback_rq(dead_rq->cpu, next); - rq = __migrate_task(rq, rf, next, dest_cpu); - if (rq != dead_rq) { - rq_unlock(rq, rf); - rq = dead_rq; - *rf = orf; - rq_relock(rq, rf); - } - raw_spin_unlock(&next->pi_lock); + get_task_struct(push_task); + /* + * Temporarily drop rq->lock such that we can wake-up the stop task. + * Both preemption and IRQs are still disabled. + */ + preempt_disable(); + raw_spin_rq_unlock(rq); + stop_one_cpu_nowait(rq->cpu, __balance_push_cpu_stop, push_task, + this_cpu_ptr(&push_work)); + preempt_enable(); + /* + * At this point need_resched() is true and we'll take the loop in + * schedule(). The next pick is obviously going to be the stop task + * which kthread_is_per_cpu() and will push this task away. + */ + raw_spin_rq_lock(rq); +} + +static void balance_push_set(int cpu, bool on) +{ + struct rq *rq = cpu_rq(cpu); + struct rq_flags rf; + + rq_lock_irqsave(rq, &rf); + if (on) { + WARN_ON_ONCE(rq->balance_callback); + rq->balance_callback = &balance_push_callback; + } else if (rq->balance_callback == &balance_push_callback) { + rq->balance_callback = NULL; } + rq_unlock_irqrestore(rq, &rf); +} + +/* + * Invoked from a CPUs hotplug control thread after the CPU has been marked + * inactive. All tasks which are not per CPU kernel threads are either + * pushed off this CPU now via balance_push() or placed on a different CPU + * during wakeup. Wait until the CPU is quiescent. + */ +static void balance_hotplug_wait(void) +{ + struct rq *rq = this_rq(); - rq->stop = stop; + rcuwait_wait_event(&rq->hotplug_wait, + rq->nr_running == 1 && !rq_has_pinned_tasks(rq), + TASK_UNINTERRUPTIBLE); +} + +#else /* !CONFIG_HOTPLUG_CPU: */ + +static inline void balance_push(struct rq *rq) +{ +} + +static inline void balance_push_set(int cpu, bool on) +{ +} + +static inline void balance_hotplug_wait(void) +{ } -#endif /* CONFIG_HOTPLUG_CPU */ + +#endif /* !CONFIG_HOTPLUG_CPU */ void set_rq_online(struct rq *rq) { @@ -5673,6 +8194,7 @@ void set_rq_offline(struct rq *rq) if (rq->online) { const struct sched_class *class; + update_rq_clock(rq); for_each_class(class) { if (class->rq_offline) class->rq_offline(rq); @@ -5683,6 +8205,30 @@ void set_rq_offline(struct rq *rq) } } +static inline void sched_set_rq_online(struct rq *rq, int cpu) +{ + struct rq_flags rf; + + rq_lock_irqsave(rq, &rf); + if (rq->rd) { + BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span)); + set_rq_online(rq); + } + rq_unlock_irqrestore(rq, &rf); +} + +static inline void sched_set_rq_offline(struct rq *rq, int cpu) +{ + struct rq_flags rf; + + rq_lock_irqsave(rq, &rf); + if (rq->rd) { + BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span)); + set_rq_offline(rq); + } + rq_unlock_irqrestore(rq, &rf); +} + /* * used to mark begin/end of suspend/resume: */ @@ -5705,7 +8251,7 @@ static void cpuset_cpu_active(void) * operation in the resume sequence, just build a single sched * domain, ignoring cpusets. */ - partition_sched_domains(1, NULL, NULL); + cpuset_reset_sched_domains(); if (--num_cpus_frozen) return; /* @@ -5718,38 +8264,56 @@ static void cpuset_cpu_active(void) cpuset_update_active_cpus(); } -static int cpuset_cpu_inactive(unsigned int cpu) +static void cpuset_cpu_inactive(unsigned int cpu) { if (!cpuhp_tasks_frozen) { - if (dl_cpu_busy(cpu)) - return -EBUSY; cpuset_update_active_cpus(); } else { num_cpus_frozen++; - partition_sched_domains(1, NULL, NULL); + cpuset_reset_sched_domains(); } - return 0; +} + +static inline void sched_smt_present_inc(int cpu) +{ +#ifdef CONFIG_SCHED_SMT + if (cpumask_weight(cpu_smt_mask(cpu)) == 2) + static_branch_inc_cpuslocked(&sched_smt_present); +#endif +} + +static inline void sched_smt_present_dec(int cpu) +{ +#ifdef CONFIG_SCHED_SMT + if (cpumask_weight(cpu_smt_mask(cpu)) == 2) + static_branch_dec_cpuslocked(&sched_smt_present); +#endif } int sched_cpu_activate(unsigned int cpu) { struct rq *rq = cpu_rq(cpu); - struct rq_flags rf; -#ifdef CONFIG_SCHED_SMT + /* + * Clear the balance_push callback and prepare to schedule + * regular tasks. + */ + balance_push_set(cpu, false); + /* * When going up, increment the number of cores with SMT present. */ - if (cpumask_weight(cpu_smt_mask(cpu)) == 2) - static_branch_inc_cpuslocked(&sched_smt_present); -#endif + sched_smt_present_inc(cpu); set_cpu_active(cpu, true); if (sched_smp_initialized) { + sched_update_numa(cpu, true); sched_domains_numa_masks_set(cpu); cpuset_cpu_active(); } + scx_rq_activate(rq); + /* * Put the rq online, if not already. This happens: * @@ -5759,48 +8323,67 @@ int sched_cpu_activate(unsigned int cpu) * 2) At runtime, if cpuset_cpu_active() fails to rebuild the * domains. */ - rq_lock_irqsave(rq, &rf); - if (rq->rd) { - BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span)); - set_rq_online(rq); - } - rq_unlock_irqrestore(rq, &rf); - - update_max_interval(); + sched_set_rq_online(rq, cpu); return 0; } int sched_cpu_deactivate(unsigned int cpu) { + struct rq *rq = cpu_rq(cpu); int ret; + ret = dl_bw_deactivate(cpu); + + if (ret) + return ret; + + /* + * Remove CPU from nohz.idle_cpus_mask to prevent participating in + * load balancing when not active + */ + nohz_balance_exit_idle(rq); + set_cpu_active(cpu, false); + /* - * We've cleared cpu_active_mask, wait for all preempt-disabled and RCU - * users of this state to go away such that all new such users will - * observe it. + * From this point forward, this CPU will refuse to run any task that + * is not: migrate_disable() or KTHREAD_IS_PER_CPU, and will actively + * push those tasks away until this gets cleared, see + * sched_cpu_dying(). + */ + balance_push_set(cpu, true); + + /* + * We've cleared cpu_active_mask / set balance_push, wait for all + * preempt-disabled and RCU users of this state to go away such that + * all new such users will observe it. + * + * Specifically, we rely on ttwu to no longer target this CPU, see + * ttwu_queue_cond() and is_cpu_allowed(). * - * Do sync before park smpboot threads to take care the rcu boost case. + * Do sync before park smpboot threads to take care the RCU boost case. */ synchronize_rcu(); -#ifdef CONFIG_SCHED_SMT + sched_set_rq_offline(rq, cpu); + + scx_rq_deactivate(rq); + /* * When going down, decrement the number of cores with SMT present. */ - if (cpumask_weight(cpu_smt_mask(cpu)) == 2) - static_branch_dec_cpuslocked(&sched_smt_present); + sched_smt_present_dec(cpu); + +#ifdef CONFIG_SCHED_SMT + sched_core_cpu_deactivate(cpu); #endif if (!sched_smp_initialized) return 0; - ret = cpuset_cpu_inactive(cpu); - if (ret) { - set_cpu_active(cpu, true); - return ret; - } + sched_update_numa(cpu, false); + cpuset_cpu_inactive(cpu); sched_domains_numa_masks_clear(cpu); return 0; } @@ -5815,79 +8398,129 @@ static void sched_rq_cpu_starting(unsigned int cpu) int sched_cpu_starting(unsigned int cpu) { + sched_core_cpu_starting(cpu); sched_rq_cpu_starting(cpu); sched_tick_start(cpu); return 0; } #ifdef CONFIG_HOTPLUG_CPU + +/* + * Invoked immediately before the stopper thread is invoked to bring the + * CPU down completely. At this point all per CPU kthreads except the + * hotplug thread (current) and the stopper thread (inactive) have been + * either parked or have been unbound from the outgoing CPU. Ensure that + * any of those which might be on the way out are gone. + * + * If after this point a bound task is being woken on this CPU then the + * responsible hotplug callback has failed to do it's job. + * sched_cpu_dying() will catch it with the appropriate fireworks. + */ +int sched_cpu_wait_empty(unsigned int cpu) +{ + balance_hotplug_wait(); + sched_force_init_mm(); + return 0; +} + +/* + * Since this CPU is going 'away' for a while, fold any nr_active delta we + * might have. Called from the CPU stopper task after ensuring that the + * stopper is the last running task on the CPU, so nr_active count is + * stable. We need to take the tear-down thread which is calling this into + * account, so we hand in adjust = 1 to the load calculation. + * + * Also see the comment "Global load-average calculations". + */ +static void calc_load_migrate(struct rq *rq) +{ + long delta = calc_load_fold_active(rq, 1); + + if (delta) + atomic_long_add(delta, &calc_load_tasks); +} + +static void dump_rq_tasks(struct rq *rq, const char *loglvl) +{ + struct task_struct *g, *p; + int cpu = cpu_of(rq); + + lockdep_assert_rq_held(rq); + + printk("%sCPU%d enqueued tasks (%u total):\n", loglvl, cpu, rq->nr_running); + for_each_process_thread(g, p) { + if (task_cpu(p) != cpu) + continue; + + if (!task_on_rq_queued(p)) + continue; + + printk("%s\tpid: %d, name: %s\n", loglvl, p->pid, p->comm); + } +} + int sched_cpu_dying(unsigned int cpu) { struct rq *rq = cpu_rq(cpu); struct rq_flags rf; /* Handle pending wakeups and then migrate everything off */ - sched_ttwu_pending(); sched_tick_stop(cpu); rq_lock_irqsave(rq, &rf); - if (rq->rd) { - BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span)); - set_rq_offline(rq); + update_rq_clock(rq); + if (rq->nr_running != 1 || rq_has_pinned_tasks(rq)) { + WARN(true, "Dying CPU not properly vacated!"); + dump_rq_tasks(rq, KERN_WARNING); } - migrate_tasks(rq, &rf); - BUG_ON(rq->nr_running != 1); + dl_server_stop(&rq->fair_server); rq_unlock_irqrestore(rq, &rf); calc_load_migrate(rq); update_max_interval(); - nohz_balance_exit_idle(rq); hrtick_clear(rq); + sched_core_cpu_dying(cpu); return 0; } -#endif +#endif /* CONFIG_HOTPLUG_CPU */ void __init sched_init_smp(void) { - sched_init_numa(); + sched_init_numa(NUMA_NO_NODE); + + prandom_init_once(&sched_rnd_state); /* * There's no userspace yet to cause hotplug operations; hence all the * CPU masks are stable and all blatant races in the below code cannot - * happen. The hotplug lock is nevertheless taken to satisfy lockdep, - * but there won't be any contention on it. + * happen. */ - cpus_read_lock(); - mutex_lock(&sched_domains_mutex); + sched_domains_mutex_lock(); sched_init_domains(cpu_active_mask); - mutex_unlock(&sched_domains_mutex); - cpus_read_unlock(); + sched_domains_mutex_unlock(); /* Move init over to a non-isolated CPU */ - if (set_cpus_allowed_ptr(current, housekeeping_cpumask(HK_FLAG_DOMAIN)) < 0) + if (set_cpus_allowed_ptr(current, housekeeping_cpumask(HK_TYPE_DOMAIN)) < 0) BUG(); + current->flags &= ~PF_NO_SETAFFINITY; sched_init_granularity(); init_sched_rt_class(); init_sched_dl_class(); + sched_init_dl_servers(); + sched_smp_initialized = true; } static int __init migration_init(void) { - sched_rq_cpu_starting(smp_processor_id()); + sched_cpu_starting(smp_processor_id()); return 0; } early_initcall(migration_init); -#else -void __init sched_init_smp(void) -{ - sched_init_granularity(); -} -#endif /* CONFIG_SMP */ - int in_sched_functions(unsigned long addr) { return in_lock_functions(addr) || @@ -5904,27 +8537,34 @@ struct task_group root_task_group; LIST_HEAD(task_groups); /* Cacheline aligned slab cache for task_group */ -static struct kmem_cache *task_group_cache __read_mostly; +static struct kmem_cache *task_group_cache __ro_after_init; #endif -DECLARE_PER_CPU(cpumask_var_t, load_balance_mask); -DECLARE_PER_CPU(cpumask_var_t, select_idle_mask); - void __init sched_init(void) { - int i, j; - unsigned long alloc_size = 0, ptr; + unsigned long ptr = 0; + int i; + + /* Make sure the linker didn't screw up */ + BUG_ON(!sched_class_above(&stop_sched_class, &dl_sched_class)); + BUG_ON(!sched_class_above(&dl_sched_class, &rt_sched_class)); + BUG_ON(!sched_class_above(&rt_sched_class, &fair_sched_class)); + BUG_ON(!sched_class_above(&fair_sched_class, &idle_sched_class)); +#ifdef CONFIG_SCHED_CLASS_EXT + BUG_ON(!sched_class_above(&fair_sched_class, &ext_sched_class)); + BUG_ON(!sched_class_above(&ext_sched_class, &idle_sched_class)); +#endif wait_bit_init(); #ifdef CONFIG_FAIR_GROUP_SCHED - alloc_size += 2 * nr_cpu_ids * sizeof(void **); + ptr += 2 * nr_cpu_ids * sizeof(void **); #endif #ifdef CONFIG_RT_GROUP_SCHED - alloc_size += 2 * nr_cpu_ids * sizeof(void **); + ptr += 2 * nr_cpu_ids * sizeof(void **); #endif - if (alloc_size) { - ptr = (unsigned long)kzalloc(alloc_size, GFP_NOWAIT); + if (ptr) { + ptr = (unsigned long)kzalloc(ptr, GFP_NOWAIT); #ifdef CONFIG_FAIR_GROUP_SCHED root_task_group.se = (struct sched_entity **)ptr; @@ -5933,7 +8573,12 @@ void __init sched_init(void) root_task_group.cfs_rq = (struct cfs_rq **)ptr; ptr += nr_cpu_ids * sizeof(void **); + root_task_group.shares = ROOT_TASK_GROUP_LOAD; + init_cfs_bandwidth(&root_task_group.cfs_bandwidth, NULL); #endif /* CONFIG_FAIR_GROUP_SCHED */ +#ifdef CONFIG_EXT_GROUP_SCHED + scx_tg_init(&root_task_group); +#endif /* CONFIG_EXT_GROUP_SCHED */ #ifdef CONFIG_RT_GROUP_SCHED root_task_group.rt_se = (struct sched_rt_entity **)ptr; ptr += nr_cpu_ids * sizeof(void **); @@ -5943,21 +8588,8 @@ void __init sched_init(void) #endif /* CONFIG_RT_GROUP_SCHED */ } -#ifdef CONFIG_CPUMASK_OFFSTACK - for_each_possible_cpu(i) { - per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node( - cpumask_size(), GFP_KERNEL, cpu_to_node(i)); - per_cpu(select_idle_mask, i) = (cpumask_var_t)kzalloc_node( - cpumask_size(), GFP_KERNEL, cpu_to_node(i)); - } -#endif /* CONFIG_CPUMASK_OFFSTACK */ - init_rt_bandwidth(&def_rt_bandwidth, global_rt_period(), global_rt_runtime()); - init_dl_bandwidth(&def_dl_bandwidth, global_rt_period(), global_rt_runtime()); - -#ifdef CONFIG_SMP init_defrootdomain(); -#endif #ifdef CONFIG_RT_GROUP_SCHED init_rt_bandwidth(&root_task_group.rt_bandwidth, @@ -5977,7 +8609,7 @@ void __init sched_init(void) struct rq *rq; rq = cpu_rq(i); - raw_spin_lock_init(&rq->lock); + raw_spin_lock_init(&rq->__lock); rq->nr_running = 0; rq->calc_load_active = 0; rq->calc_load_update = jiffies + LOAD_FREQ; @@ -5985,13 +8617,12 @@ void __init sched_init(void) init_rt_rq(&rq->rt); init_dl_rq(&rq->dl); #ifdef CONFIG_FAIR_GROUP_SCHED - root_task_group.shares = ROOT_TASK_GROUP_LOAD; INIT_LIST_HEAD(&rq->leaf_cfs_rq_list); rq->tmp_alone_branch = &rq->leaf_cfs_rq_list; /* * How much CPU bandwidth does root_task_group get? * - * In case of task-groups formed thr' the cgroup filesystem, it + * In case of task-groups formed through the cgroup filesystem, it * gets 100% of the CPU resources in the system. This overall * system CPU resource is divided among the tasks of * root_task_group and its child task-groups in a fair manner, @@ -6007,23 +8638,22 @@ void __init sched_init(void) * We achieve this by letting root_task_group's tasks sit * directly in rq->cfs (i.e root_task_group->se[] = NULL). */ - init_cfs_bandwidth(&root_task_group.cfs_bandwidth); init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL); #endif /* CONFIG_FAIR_GROUP_SCHED */ - rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime; #ifdef CONFIG_RT_GROUP_SCHED + /* + * This is required for init cpu because rt.c:__enable_runtime() + * starts working after scheduler_running, which is not the case + * yet. + */ + rq->rt.rt_runtime = global_rt_runtime(); init_tg_rt_entry(&root_task_group, &rq->rt, NULL, i, NULL); #endif - - for (j = 0; j < CPU_LOAD_IDX_MAX; j++) - rq->cpu_load[j] = 0; - -#ifdef CONFIG_SMP rq->sd = NULL; rq->rd = NULL; - rq->cpu_capacity = rq->cpu_capacity_orig = SCHED_CAPACITY_SCALE; - rq->balance_callback = NULL; + rq->cpu_capacity = SCHED_CAPACITY_SCALE; + rq->balance_callback = &balance_push_callback; rq->active_balance = 0; rq->next_balance = jiffies; rq->push_cpu = 0; @@ -6037,72 +8667,118 @@ void __init sched_init(void) rq_attach_root(rq, &def_root_domain); #ifdef CONFIG_NO_HZ_COMMON - rq->last_load_update_tick = jiffies; rq->last_blocked_load_update_tick = jiffies; atomic_set(&rq->nohz_flags, 0); + + INIT_CSD(&rq->nohz_csd, nohz_csd_func, rq); +#endif +#ifdef CONFIG_HOTPLUG_CPU + rcuwait_init(&rq->hotplug_wait); #endif -#endif /* CONFIG_SMP */ hrtick_rq_init(rq); atomic_set(&rq->nr_iowait, 0); + fair_server_init(rq); + +#ifdef CONFIG_SCHED_CORE + rq->core = rq; + rq->core_pick = NULL; + rq->core_dl_server = NULL; + rq->core_enabled = 0; + rq->core_tree = RB_ROOT; + rq->core_forceidle_count = 0; + rq->core_forceidle_occupation = 0; + rq->core_forceidle_start = 0; + + rq->core_cookie = 0UL; +#endif + zalloc_cpumask_var_node(&rq->scratch_mask, GFP_KERNEL, cpu_to_node(i)); } set_load_weight(&init_task, false); + init_task.se.slice = sysctl_sched_base_slice, /* * The boot idle thread does lazy MMU switching as well: */ - mmgrab(&init_mm); + mmgrab_lazy_tlb(&init_mm); enter_lazy_tlb(&init_mm, current); /* + * The idle task doesn't need the kthread struct to function, but it + * is dressed up as a per-CPU kthread and thus needs to play the part + * if we want to avoid special-casing it in code that deals with per-CPU + * kthreads. + */ + WARN_ON(!set_kthread_struct(current)); + + /* * Make us the idle thread. Technically, schedule() should not be * called from this thread, however somewhere below it might be, * but because we are the idle thread, we just pick up running again * when this runqueue becomes "idle". */ + __sched_fork(0, current); init_idle(current, smp_processor_id()); calc_load_update = jiffies + LOAD_FREQ; -#ifdef CONFIG_SMP idle_thread_set_boot_cpu(); -#endif - init_sched_fair_class(); - init_schedstats(); + balance_push_set(smp_processor_id(), false); + init_sched_fair_class(); + init_sched_ext_class(); psi_init(); + init_uclamp(); + + preempt_dynamic_init(); + scheduler_running = 1; } #ifdef CONFIG_DEBUG_ATOMIC_SLEEP -static inline int preempt_count_equals(int preempt_offset) -{ - int nested = preempt_count() + rcu_preempt_depth(); - - return (nested == preempt_offset); -} -void __might_sleep(const char *file, int line, int preempt_offset) +void __might_sleep(const char *file, int line) { + unsigned int state = get_current_state(); /* * Blocking primitives will set (and therefore destroy) current->state, * since we will exit with TASK_RUNNING make sure we enter with it, * otherwise we will destroy state. */ - WARN_ONCE(current->state != TASK_RUNNING && current->task_state_change, + WARN_ONCE(state != TASK_RUNNING && current->task_state_change, "do not call blocking ops when !TASK_RUNNING; " - "state=%lx set at [<%p>] %pS\n", - current->state, + "state=%x set at [<%p>] %pS\n", state, (void *)current->task_state_change, (void *)current->task_state_change); - ___might_sleep(file, line, preempt_offset); + __might_resched(file, line, 0); } EXPORT_SYMBOL(__might_sleep); -void ___might_sleep(const char *file, int line, int preempt_offset) +static void print_preempt_disable_ip(int preempt_offset, unsigned long ip) +{ + if (!IS_ENABLED(CONFIG_DEBUG_PREEMPT)) + return; + + if (preempt_count() == preempt_offset) + return; + + pr_err("Preemption disabled at:"); + print_ip_sym(KERN_ERR, ip); +} + +static inline bool resched_offsets_ok(unsigned int offsets) +{ + unsigned int nested = preempt_count(); + + nested += rcu_preempt_depth() << MIGHT_RESCHED_RCU_SHIFT; + + return nested == offsets; +} + +void __might_resched(const char *file, int line, unsigned int offsets) { /* Ratelimiting timestamp: */ static unsigned long prev_jiffy; @@ -6112,8 +8788,8 @@ void ___might_sleep(const char *file, int line, int preempt_offset) /* WARN_ON_ONCE() by default, no rate limit required: */ rcu_sleep_check(); - if ((preempt_count_equals(preempt_offset) && !irqs_disabled() && - !is_idle_task(current)) || + if ((resched_offsets_ok(offsets) && !irqs_disabled() && + !is_idle_task(current) && !current->non_block_count) || system_state == SYSTEM_BOOTING || system_state > SYSTEM_RUNNING || oops_in_progress) return; @@ -6125,31 +8801,95 @@ void ___might_sleep(const char *file, int line, int preempt_offset) /* Save this before calling printk(), since that will clobber it: */ preempt_disable_ip = get_preempt_disable_ip(current); - printk(KERN_ERR - "BUG: sleeping function called from invalid context at %s:%d\n", - file, line); - printk(KERN_ERR - "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n", - in_atomic(), irqs_disabled(), - current->pid, current->comm); + pr_err("BUG: sleeping function called from invalid context at %s:%d\n", + file, line); + pr_err("in_atomic(): %d, irqs_disabled(): %d, non_block: %d, pid: %d, name: %s\n", + in_atomic(), irqs_disabled(), current->non_block_count, + current->pid, current->comm); + pr_err("preempt_count: %x, expected: %x\n", preempt_count(), + offsets & MIGHT_RESCHED_PREEMPT_MASK); + + if (IS_ENABLED(CONFIG_PREEMPT_RCU)) { + pr_err("RCU nest depth: %d, expected: %u\n", + rcu_preempt_depth(), offsets >> MIGHT_RESCHED_RCU_SHIFT); + } if (task_stack_end_corrupted(current)) - printk(KERN_EMERG "Thread overran stack, or stack corrupted\n"); + pr_emerg("Thread overran stack, or stack corrupted\n"); debug_show_held_locks(current); if (irqs_disabled()) print_irqtrace_events(current); - if (IS_ENABLED(CONFIG_DEBUG_PREEMPT) - && !preempt_count_equals(preempt_offset)) { - pr_err("Preemption disabled at:"); - print_ip_sym(preempt_disable_ip); - pr_cont("\n"); - } + + print_preempt_disable_ip(offsets & MIGHT_RESCHED_PREEMPT_MASK, + preempt_disable_ip); + dump_stack(); add_taint(TAINT_WARN, LOCKDEP_STILL_OK); } -EXPORT_SYMBOL(___might_sleep); -#endif +EXPORT_SYMBOL(__might_resched); + +void __cant_sleep(const char *file, int line, int preempt_offset) +{ + static unsigned long prev_jiffy; + + if (irqs_disabled()) + return; + + if (!IS_ENABLED(CONFIG_PREEMPT_COUNT)) + return; + + if (preempt_count() > preempt_offset) + return; + + if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy) + return; + prev_jiffy = jiffies; + + printk(KERN_ERR "BUG: assuming atomic context at %s:%d\n", file, line); + printk(KERN_ERR "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n", + in_atomic(), irqs_disabled(), + current->pid, current->comm); + + debug_show_held_locks(current); + dump_stack(); + add_taint(TAINT_WARN, LOCKDEP_STILL_OK); +} +EXPORT_SYMBOL_GPL(__cant_sleep); + +# ifdef CONFIG_SMP +void __cant_migrate(const char *file, int line) +{ + static unsigned long prev_jiffy; + + if (irqs_disabled()) + return; + + if (is_migration_disabled(current)) + return; + + if (!IS_ENABLED(CONFIG_PREEMPT_COUNT)) + return; + + if (preempt_count() > 0) + return; + + if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy) + return; + prev_jiffy = jiffies; + + pr_err("BUG: assuming non migratable context at %s:%d\n", file, line); + pr_err("in_atomic(): %d, irqs_disabled(): %d, migration_disabled() %u pid: %d, name: %s\n", + in_atomic(), irqs_disabled(), is_migration_disabled(current), + current->pid, current->comm); + + debug_show_held_locks(current); + dump_stack(); + add_taint(TAINT_WARN, LOCKDEP_STILL_OK); +} +EXPORT_SYMBOL_GPL(__cant_migrate); +# endif /* CONFIG_SMP */ +#endif /* CONFIG_DEBUG_ATOMIC_SLEEP */ #ifdef CONFIG_MAGIC_SYSRQ void normalize_rt_tasks(void) @@ -6168,11 +8908,11 @@ void normalize_rt_tasks(void) continue; p->se.exec_start = 0; - schedstat_set(p->se.statistics.wait_start, 0); - schedstat_set(p->se.statistics.sleep_start, 0); - schedstat_set(p->se.statistics.block_start, 0); + schedstat_set(p->stats.wait_start, 0); + schedstat_set(p->stats.sleep_start, 0); + schedstat_set(p->stats.block_start, 0); - if (!dl_task(p) && !rt_task(p)) { + if (!rt_or_dl_task(p)) { /* * Renice negative nice level userspace * tasks back to 0: @@ -6189,9 +8929,9 @@ void normalize_rt_tasks(void) #endif /* CONFIG_MAGIC_SYSRQ */ -#if defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) +#ifdef CONFIG_KGDB_KDB /* - * These functions are only useful for the IA64 MCA handling, or kdb. + * These functions are only useful for KDB. * * They can only be called when the whole system has been * stopped - every CPU needs to be quiescent, and no scheduling @@ -6213,35 +8953,26 @@ struct task_struct *curr_task(int cpu) return cpu_curr(cpu); } -#endif /* defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) */ - -#ifdef CONFIG_IA64 -/** - * set_curr_task - set the current task for a given CPU. - * @cpu: the processor in question. - * @p: the task pointer to set. - * - * Description: This function must only be used when non-maskable interrupts - * are serviced on a separate stack. It allows the architecture to switch the - * notion of the current task on a CPU in a non-blocking manner. This function - * must be called with all CPU's synchronized, and interrupts disabled, the - * and caller must save the original value of the current task (see - * curr_task() above) and restore that value before reenabling interrupts and - * re-starting the system. - * - * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED! - */ -void ia64_set_curr_task(int cpu, struct task_struct *p) -{ - cpu_curr(cpu) = p; -} - -#endif +#endif /* CONFIG_KGDB_KDB */ #ifdef CONFIG_CGROUP_SCHED /* task_group_lock serializes the addition/removal of task groups */ static DEFINE_SPINLOCK(task_group_lock); +static inline void alloc_uclamp_sched_group(struct task_group *tg, + struct task_group *parent) +{ +#ifdef CONFIG_UCLAMP_TASK_GROUP + enum uclamp_id clamp_id; + + for_each_clamp_id(clamp_id) { + uclamp_se_set(&tg->uclamp_req[clamp_id], + uclamp_none(clamp_id), false); + tg->uclamp[clamp_id] = parent->uclamp[clamp_id]; + } +#endif +} + static void sched_free_group(struct task_group *tg) { free_fair_sched_group(tg); @@ -6250,6 +8981,22 @@ static void sched_free_group(struct task_group *tg) kmem_cache_free(task_group_cache, tg); } +static void sched_free_group_rcu(struct rcu_head *rcu) +{ + sched_free_group(container_of(rcu, struct task_group, rcu)); +} + +static void sched_unregister_group(struct task_group *tg) +{ + unregister_fair_sched_group(tg); + unregister_rt_sched_group(tg); + /* + * We have to wait for yet another RCU grace period to expire, as + * print_cfs_stats() might run concurrently. + */ + call_rcu(&tg->rcu, sched_free_group_rcu); +} + /* allocate runqueue etc for a new task group */ struct task_group *sched_create_group(struct task_group *parent) { @@ -6265,6 +9012,9 @@ struct task_group *sched_create_group(struct task_group *parent) if (!alloc_rt_sched_group(tg, parent)) goto err; + scx_tg_init(tg); + alloc_uclamp_sched_group(tg, parent); + return tg; err: @@ -6277,7 +9027,7 @@ void sched_online_group(struct task_group *tg, struct task_group *parent) unsigned long flags; spin_lock_irqsave(&task_group_lock, flags); - list_add_rcu(&tg->list, &task_groups); + list_add_tail_rcu(&tg->list, &task_groups); /* Root should already exist: */ WARN_ON(!parent); @@ -6290,33 +9040,43 @@ void sched_online_group(struct task_group *tg, struct task_group *parent) online_fair_sched_group(tg); } -/* rcu callback to free various structures associated with a task group */ -static void sched_free_group_rcu(struct rcu_head *rhp) +/* RCU callback to free various structures associated with a task group */ +static void sched_unregister_group_rcu(struct rcu_head *rhp) { /* Now it should be safe to free those cfs_rqs: */ - sched_free_group(container_of(rhp, struct task_group, rcu)); + sched_unregister_group(container_of(rhp, struct task_group, rcu)); } void sched_destroy_group(struct task_group *tg) { /* Wait for possible concurrent references to cfs_rqs complete: */ - call_rcu(&tg->rcu, sched_free_group_rcu); + call_rcu(&tg->rcu, sched_unregister_group_rcu); } -void sched_offline_group(struct task_group *tg) +void sched_release_group(struct task_group *tg) { unsigned long flags; - /* End participation in shares distribution: */ - unregister_fair_sched_group(tg); - + /* + * Unlink first, to avoid walk_tg_tree_from() from finding us (via + * sched_cfs_period_timer()). + * + * For this to be effective, we have to wait for all pending users of + * this task group to leave their RCU critical section to ensure no new + * user will see our dying task group any more. Specifically ensure + * that tg_unthrottle_up() won't add decayed cfs_rq's to it. + * + * We therefore defer calling unregister_fair_sched_group() to + * sched_unregister_group() which is guarantied to get called only after the + * current RCU grace period has expired. + */ spin_lock_irqsave(&task_group_lock, flags); list_del_rcu(&tg->list); list_del_rcu(&tg->siblings); spin_unlock_irqrestore(&task_group_lock, flags); } -static void sched_change_group(struct task_struct *tsk, int type) +static void sched_change_group(struct task_struct *tsk) { struct task_group *tg; @@ -6332,7 +9092,7 @@ static void sched_change_group(struct task_struct *tsk, int type) #ifdef CONFIG_FAIR_GROUP_SCHED if (tsk->sched_class->task_change_group) - tsk->sched_class->task_change_group(tsk, type); + tsk->sched_class->task_change_group(tsk); else #endif set_task_rq(tsk, task_cpu(tsk)); @@ -6345,37 +9105,25 @@ static void sched_change_group(struct task_struct *tsk, int type) * now. This function just updates tsk->se.cfs_rq and tsk->se.parent to reflect * its new group. */ -void sched_move_task(struct task_struct *tsk) +void sched_move_task(struct task_struct *tsk, bool for_autogroup) { - int queued, running, queue_flags = - DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK; - struct rq_flags rf; + unsigned int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE; + bool resched = false; struct rq *rq; - rq = task_rq_lock(tsk, &rf); - update_rq_clock(rq); - - running = task_current(rq, tsk); - queued = task_on_rq_queued(tsk); - - if (queued) - dequeue_task(rq, tsk, queue_flags); - if (running) - put_prev_task(rq, tsk); - - sched_change_group(tsk, TASK_MOVE_GROUP); + CLASS(task_rq_lock, rq_guard)(tsk); + rq = rq_guard.rq; - if (queued) - enqueue_task(rq, tsk, queue_flags); - if (running) - set_curr_task(rq, tsk); - - task_rq_unlock(rq, tsk, &rf); -} + scoped_guard (sched_change, tsk, queue_flags) { + sched_change_group(tsk); + if (!for_autogroup) + scx_cgroup_move_task(tsk); + if (scope->running) + resched = true; + } -static inline struct task_group *css_tg(struct cgroup_subsys_state *css) -{ - return css ? container_of(css, struct task_group, css) : NULL; + if (resched) + resched_curr(rq); } static struct cgroup_subsys_state * @@ -6401,17 +9149,37 @@ static int cpu_cgroup_css_online(struct cgroup_subsys_state *css) { struct task_group *tg = css_tg(css); struct task_group *parent = css_tg(css->parent); + int ret; + + ret = scx_tg_online(tg); + if (ret) + return ret; if (parent) sched_online_group(tg, parent); + +#ifdef CONFIG_UCLAMP_TASK_GROUP + /* Propagate the effective uclamp value for the new group */ + guard(mutex)(&uclamp_mutex); + guard(rcu)(); + cpu_util_update_eff(css); +#endif + return 0; } +static void cpu_cgroup_css_offline(struct cgroup_subsys_state *css) +{ + struct task_group *tg = css_tg(css); + + scx_tg_offline(tg); +} + static void cpu_cgroup_css_released(struct cgroup_subsys_state *css) { struct task_group *tg = css_tg(css); - sched_offline_group(tg); + sched_release_group(tg); } static void cpu_cgroup_css_free(struct cgroup_subsys_state *css) @@ -6421,59 +9189,25 @@ static void cpu_cgroup_css_free(struct cgroup_subsys_state *css) /* * Relies on the RCU grace period between css_released() and this. */ - sched_free_group(tg); -} - -/* - * This is called before wake_up_new_task(), therefore we really only - * have to set its group bits, all the other stuff does not apply. - */ -static void cpu_cgroup_fork(struct task_struct *task) -{ - struct rq_flags rf; - struct rq *rq; - - rq = task_rq_lock(task, &rf); - - update_rq_clock(rq); - sched_change_group(task, TASK_SET_GROUP); - - task_rq_unlock(rq, task, &rf); + sched_unregister_group(tg); } static int cpu_cgroup_can_attach(struct cgroup_taskset *tset) { +#ifdef CONFIG_RT_GROUP_SCHED struct task_struct *task; struct cgroup_subsys_state *css; - int ret = 0; + + if (!rt_group_sched_enabled()) + goto scx_check; cgroup_taskset_for_each(task, css, tset) { -#ifdef CONFIG_RT_GROUP_SCHED if (!sched_rt_can_attach(css_tg(css), task)) return -EINVAL; -#else - /* We don't support RT-tasks being in separate groups */ - if (task->sched_class != &fair_sched_class) - return -EINVAL; -#endif - /* - * Serialize against wake_up_new_task() such that if its - * running, we're sure to observe its full state. - */ - raw_spin_lock_irq(&task->pi_lock); - /* - * Avoid calling sched_move_task() before wake_up_new_task() - * has happened. This would lead to problems with PELT, due to - * move wanting to detach+attach while we're not attached yet. - */ - if (task->state == TASK_NEW) - ret = -EINVAL; - raw_spin_unlock_irq(&task->pi_lock); - - if (ret) - break; } - return ret; +scx_check: +#endif /* CONFIG_RT_GROUP_SCHED */ + return scx_cgroup_can_attach(tset); } static void cpu_cgroup_attach(struct cgroup_taskset *tset) @@ -6482,65 +9216,250 @@ static void cpu_cgroup_attach(struct cgroup_taskset *tset) struct cgroup_subsys_state *css; cgroup_taskset_for_each(task, css, tset) - sched_move_task(task); + sched_move_task(task, false); +} + +static void cpu_cgroup_cancel_attach(struct cgroup_taskset *tset) +{ + scx_cgroup_cancel_attach(tset); +} + +#ifdef CONFIG_UCLAMP_TASK_GROUP +static void cpu_util_update_eff(struct cgroup_subsys_state *css) +{ + struct cgroup_subsys_state *top_css = css; + struct uclamp_se *uc_parent = NULL; + struct uclamp_se *uc_se = NULL; + unsigned int eff[UCLAMP_CNT]; + enum uclamp_id clamp_id; + unsigned int clamps; + + lockdep_assert_held(&uclamp_mutex); + WARN_ON_ONCE(!rcu_read_lock_held()); + + css_for_each_descendant_pre(css, top_css) { + uc_parent = css_tg(css)->parent + ? css_tg(css)->parent->uclamp : NULL; + + for_each_clamp_id(clamp_id) { + /* Assume effective clamps matches requested clamps */ + eff[clamp_id] = css_tg(css)->uclamp_req[clamp_id].value; + /* Cap effective clamps with parent's effective clamps */ + if (uc_parent && + eff[clamp_id] > uc_parent[clamp_id].value) { + eff[clamp_id] = uc_parent[clamp_id].value; + } + } + /* Ensure protection is always capped by limit */ + eff[UCLAMP_MIN] = min(eff[UCLAMP_MIN], eff[UCLAMP_MAX]); + + /* Propagate most restrictive effective clamps */ + clamps = 0x0; + uc_se = css_tg(css)->uclamp; + for_each_clamp_id(clamp_id) { + if (eff[clamp_id] == uc_se[clamp_id].value) + continue; + uc_se[clamp_id].value = eff[clamp_id]; + uc_se[clamp_id].bucket_id = uclamp_bucket_id(eff[clamp_id]); + clamps |= (0x1 << clamp_id); + } + if (!clamps) { + css = css_rightmost_descendant(css); + continue; + } + + /* Immediately update descendants RUNNABLE tasks */ + uclamp_update_active_tasks(css); + } } +/* + * Integer 10^N with a given N exponent by casting to integer the literal "1eN" + * C expression. Since there is no way to convert a macro argument (N) into a + * character constant, use two levels of macros. + */ +#define _POW10(exp) ((unsigned int)1e##exp) +#define POW10(exp) _POW10(exp) + +struct uclamp_request { +#define UCLAMP_PERCENT_SHIFT 2 +#define UCLAMP_PERCENT_SCALE (100 * POW10(UCLAMP_PERCENT_SHIFT)) + s64 percent; + u64 util; + int ret; +}; + +static inline struct uclamp_request +capacity_from_percent(char *buf) +{ + struct uclamp_request req = { + .percent = UCLAMP_PERCENT_SCALE, + .util = SCHED_CAPACITY_SCALE, + .ret = 0, + }; + + buf = strim(buf); + if (strcmp(buf, "max")) { + req.ret = cgroup_parse_float(buf, UCLAMP_PERCENT_SHIFT, + &req.percent); + if (req.ret) + return req; + if ((u64)req.percent > UCLAMP_PERCENT_SCALE) { + req.ret = -ERANGE; + return req; + } + + req.util = req.percent << SCHED_CAPACITY_SHIFT; + req.util = DIV_ROUND_CLOSEST_ULL(req.util, UCLAMP_PERCENT_SCALE); + } + + return req; +} + +static ssize_t cpu_uclamp_write(struct kernfs_open_file *of, char *buf, + size_t nbytes, loff_t off, + enum uclamp_id clamp_id) +{ + struct uclamp_request req; + struct task_group *tg; + + req = capacity_from_percent(buf); + if (req.ret) + return req.ret; + + sched_uclamp_enable(); + + guard(mutex)(&uclamp_mutex); + guard(rcu)(); + + tg = css_tg(of_css(of)); + if (tg->uclamp_req[clamp_id].value != req.util) + uclamp_se_set(&tg->uclamp_req[clamp_id], req.util, false); + + /* + * Because of not recoverable conversion rounding we keep track of the + * exact requested value + */ + tg->uclamp_pct[clamp_id] = req.percent; + + /* Update effective clamps to track the most restrictive value */ + cpu_util_update_eff(of_css(of)); + + return nbytes; +} + +static ssize_t cpu_uclamp_min_write(struct kernfs_open_file *of, + char *buf, size_t nbytes, + loff_t off) +{ + return cpu_uclamp_write(of, buf, nbytes, off, UCLAMP_MIN); +} + +static ssize_t cpu_uclamp_max_write(struct kernfs_open_file *of, + char *buf, size_t nbytes, + loff_t off) +{ + return cpu_uclamp_write(of, buf, nbytes, off, UCLAMP_MAX); +} + +static inline void cpu_uclamp_print(struct seq_file *sf, + enum uclamp_id clamp_id) +{ + struct task_group *tg; + u64 util_clamp; + u64 percent; + u32 rem; + + scoped_guard (rcu) { + tg = css_tg(seq_css(sf)); + util_clamp = tg->uclamp_req[clamp_id].value; + } + + if (util_clamp == SCHED_CAPACITY_SCALE) { + seq_puts(sf, "max\n"); + return; + } + + percent = tg->uclamp_pct[clamp_id]; + percent = div_u64_rem(percent, POW10(UCLAMP_PERCENT_SHIFT), &rem); + seq_printf(sf, "%llu.%0*u\n", percent, UCLAMP_PERCENT_SHIFT, rem); +} + +static int cpu_uclamp_min_show(struct seq_file *sf, void *v) +{ + cpu_uclamp_print(sf, UCLAMP_MIN); + return 0; +} + +static int cpu_uclamp_max_show(struct seq_file *sf, void *v) +{ + cpu_uclamp_print(sf, UCLAMP_MAX); + return 0; +} +#endif /* CONFIG_UCLAMP_TASK_GROUP */ + +#ifdef CONFIG_GROUP_SCHED_WEIGHT +static unsigned long tg_weight(struct task_group *tg) +{ #ifdef CONFIG_FAIR_GROUP_SCHED + return scale_load_down(tg->shares); +#else + return sched_weight_from_cgroup(tg->scx.weight); +#endif +} + static int cpu_shares_write_u64(struct cgroup_subsys_state *css, struct cftype *cftype, u64 shareval) { - return sched_group_set_shares(css_tg(css), scale_load(shareval)); + int ret; + + if (shareval > scale_load_down(ULONG_MAX)) + shareval = MAX_SHARES; + ret = sched_group_set_shares(css_tg(css), scale_load(shareval)); + if (!ret) + scx_group_set_weight(css_tg(css), + sched_weight_to_cgroup(shareval)); + return ret; } static u64 cpu_shares_read_u64(struct cgroup_subsys_state *css, struct cftype *cft) { - struct task_group *tg = css_tg(css); - - return (u64) scale_load_down(tg->shares); + return tg_weight(css_tg(css)); } +#endif /* CONFIG_GROUP_SCHED_WEIGHT */ #ifdef CONFIG_CFS_BANDWIDTH static DEFINE_MUTEX(cfs_constraints_mutex); -const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */ -const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */ - static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime); -static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota) +static int tg_set_cfs_bandwidth(struct task_group *tg, + u64 period_us, u64 quota_us, u64 burst_us) { int i, ret = 0, runtime_enabled, runtime_was_enabled; struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth; + u64 period, quota, burst; - if (tg == &root_task_group) - return -EINVAL; + period = (u64)period_us * NSEC_PER_USEC; - /* - * Ensure we have at some amount of bandwidth every period. This is - * to prevent reaching a state of large arrears when throttled via - * entity_tick() resulting in prolonged exit starvation. - */ - if (quota < min_cfs_quota_period || period < min_cfs_quota_period) - return -EINVAL; + if (quota_us == RUNTIME_INF) + quota = RUNTIME_INF; + else + quota = (u64)quota_us * NSEC_PER_USEC; - /* - * Likewise, bound things on the otherside by preventing insane quota - * periods. This also allows us to normalize in computing quota - * feasibility. - */ - if (period > max_cfs_quota_period) - return -EINVAL; + burst = (u64)burst_us * NSEC_PER_USEC; /* * Prevent race between setting of cfs_rq->runtime_enabled and * unthrottle_offline_cfs_rqs(). */ - get_online_cpus(); - mutex_lock(&cfs_constraints_mutex); + guard(cpus_read_lock)(); + guard(mutex)(&cfs_constraints_mutex); + ret = __cfs_schedulable(tg, period, quota); if (ret) - goto out_unlock; + return ret; runtime_enabled = quota != RUNTIME_INF; runtime_was_enabled = cfs_b->quota != RUNTIME_INF; @@ -6550,59 +9469,56 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota) */ if (runtime_enabled && !runtime_was_enabled) cfs_bandwidth_usage_inc(); - raw_spin_lock_irq(&cfs_b->lock); - cfs_b->period = ns_to_ktime(period); - cfs_b->quota = quota; - __refill_cfs_bandwidth_runtime(cfs_b); + scoped_guard (raw_spinlock_irq, &cfs_b->lock) { + cfs_b->period = ns_to_ktime(period); + cfs_b->quota = quota; + cfs_b->burst = burst; - /* Restart the period timer (if active) to handle new period expiry: */ - if (runtime_enabled) - start_cfs_bandwidth(cfs_b); + __refill_cfs_bandwidth_runtime(cfs_b); - raw_spin_unlock_irq(&cfs_b->lock); + /* + * Restart the period timer (if active) to handle new + * period expiry: + */ + if (runtime_enabled) + start_cfs_bandwidth(cfs_b); + } for_each_online_cpu(i) { struct cfs_rq *cfs_rq = tg->cfs_rq[i]; struct rq *rq = cfs_rq->rq; - struct rq_flags rf; - rq_lock_irq(rq, &rf); + guard(rq_lock_irq)(rq); cfs_rq->runtime_enabled = runtime_enabled; - cfs_rq->runtime_remaining = 0; + cfs_rq->runtime_remaining = 1; if (cfs_rq->throttled) unthrottle_cfs_rq(cfs_rq); - rq_unlock_irq(rq, &rf); } + if (runtime_was_enabled && !runtime_enabled) cfs_bandwidth_usage_dec(); -out_unlock: - mutex_unlock(&cfs_constraints_mutex); - put_online_cpus(); - return ret; + return 0; } -int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us) +static u64 tg_get_cfs_period(struct task_group *tg) { - u64 quota, period; + u64 cfs_period_us; - period = ktime_to_ns(tg->cfs_bandwidth.period); - if (cfs_quota_us < 0) - quota = RUNTIME_INF; - else - quota = (u64)cfs_quota_us * NSEC_PER_USEC; + cfs_period_us = ktime_to_ns(tg->cfs_bandwidth.period); + do_div(cfs_period_us, NSEC_PER_USEC); - return tg_set_cfs_bandwidth(tg, period, quota); + return cfs_period_us; } -long tg_get_cfs_quota(struct task_group *tg) +static u64 tg_get_cfs_quota(struct task_group *tg) { u64 quota_us; if (tg->cfs_bandwidth.quota == RUNTIME_INF) - return -1; + return RUNTIME_INF; quota_us = tg->cfs_bandwidth.quota; do_div(quota_us, NSEC_PER_USEC); @@ -6610,48 +9526,14 @@ long tg_get_cfs_quota(struct task_group *tg) return quota_us; } -int tg_set_cfs_period(struct task_group *tg, long cfs_period_us) -{ - u64 quota, period; - - period = (u64)cfs_period_us * NSEC_PER_USEC; - quota = tg->cfs_bandwidth.quota; - - return tg_set_cfs_bandwidth(tg, period, quota); -} - -long tg_get_cfs_period(struct task_group *tg) -{ - u64 cfs_period_us; - - cfs_period_us = ktime_to_ns(tg->cfs_bandwidth.period); - do_div(cfs_period_us, NSEC_PER_USEC); - - return cfs_period_us; -} - -static s64 cpu_cfs_quota_read_s64(struct cgroup_subsys_state *css, - struct cftype *cft) +static u64 tg_get_cfs_burst(struct task_group *tg) { - return tg_get_cfs_quota(css_tg(css)); -} + u64 burst_us; -static int cpu_cfs_quota_write_s64(struct cgroup_subsys_state *css, - struct cftype *cftype, s64 cfs_quota_us) -{ - return tg_set_cfs_quota(css_tg(css), cfs_quota_us); -} + burst_us = tg->cfs_bandwidth.burst; + do_div(burst_us, NSEC_PER_USEC); -static u64 cpu_cfs_period_read_u64(struct cgroup_subsys_state *css, - struct cftype *cft) -{ - return tg_get_cfs_period(css_tg(css)); -} - -static int cpu_cfs_period_write_u64(struct cgroup_subsys_state *css, - struct cftype *cftype, u64 cfs_period_us) -{ - return tg_set_cfs_period(css_tg(css), cfs_period_us); + return burst_us; } struct cfs_schedulable_data { @@ -6699,11 +9581,16 @@ static int tg_cfs_schedulable_down(struct task_group *tg, void *data) /* * Ensure max(child_quota) <= parent_quota. On cgroup2, - * always take the min. On cgroup1, only inherit when no - * limit is set: + * always take the non-RUNTIME_INF min. On cgroup1, only + * inherit when no limit is set. In both cases this is used + * by the scheduler to determine if a given CFS task has a + * bandwidth constraint at some higher level. */ if (cgroup_subsys_on_dfl(cpu_cgrp_subsys)) { - quota = min(quota, parent_quota); + if (quota == RUNTIME_INF) + quota = parent_quota; + else if (parent_quota != RUNTIME_INF) + quota = min(quota, parent_quota); } else { if (quota == RUNTIME_INF) quota = parent_quota; @@ -6718,7 +9605,6 @@ static int tg_cfs_schedulable_down(struct task_group *tg, void *data) static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota) { - int ret; struct cfs_schedulable_data data = { .tg = tg, .period = period, @@ -6730,11 +9616,8 @@ static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota) do_div(data.quota, NSEC_PER_USEC); } - rcu_read_lock(); - ret = walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data); - rcu_read_unlock(); - - return ret; + guard(rcu)(); + return walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data); } static int cpu_cfs_stat_show(struct seq_file *sf, void *v) @@ -6747,19 +9630,182 @@ static int cpu_cfs_stat_show(struct seq_file *sf, void *v) seq_printf(sf, "throttled_time %llu\n", cfs_b->throttled_time); if (schedstat_enabled() && tg != &root_task_group) { + struct sched_statistics *stats; u64 ws = 0; int i; - for_each_possible_cpu(i) - ws += schedstat_val(tg->se[i]->statistics.wait_sum); + for_each_possible_cpu(i) { + stats = __schedstats_from_se(tg->se[i]); + ws += schedstat_val(stats->wait_sum); + } seq_printf(sf, "wait_sum %llu\n", ws); } + seq_printf(sf, "nr_bursts %d\n", cfs_b->nr_burst); + seq_printf(sf, "burst_time %llu\n", cfs_b->burst_time); + + return 0; +} + +static u64 throttled_time_self(struct task_group *tg) +{ + int i; + u64 total = 0; + + for_each_possible_cpu(i) { + total += READ_ONCE(tg->cfs_rq[i]->throttled_clock_self_time); + } + + return total; +} + +static int cpu_cfs_local_stat_show(struct seq_file *sf, void *v) +{ + struct task_group *tg = css_tg(seq_css(sf)); + + seq_printf(sf, "throttled_time %llu\n", throttled_time_self(tg)); + return 0; } #endif /* CONFIG_CFS_BANDWIDTH */ -#endif /* CONFIG_FAIR_GROUP_SCHED */ + +#ifdef CONFIG_GROUP_SCHED_BANDWIDTH +const u64 max_bw_quota_period_us = 1 * USEC_PER_SEC; /* 1s */ +static const u64 min_bw_quota_period_us = 1 * USEC_PER_MSEC; /* 1ms */ +/* More than 203 days if BW_SHIFT equals 20. */ +static const u64 max_bw_runtime_us = MAX_BW; + +static void tg_bandwidth(struct task_group *tg, + u64 *period_us_p, u64 *quota_us_p, u64 *burst_us_p) +{ +#ifdef CONFIG_CFS_BANDWIDTH + if (period_us_p) + *period_us_p = tg_get_cfs_period(tg); + if (quota_us_p) + *quota_us_p = tg_get_cfs_quota(tg); + if (burst_us_p) + *burst_us_p = tg_get_cfs_burst(tg); +#else /* !CONFIG_CFS_BANDWIDTH */ + if (period_us_p) + *period_us_p = tg->scx.bw_period_us; + if (quota_us_p) + *quota_us_p = tg->scx.bw_quota_us; + if (burst_us_p) + *burst_us_p = tg->scx.bw_burst_us; +#endif /* CONFIG_CFS_BANDWIDTH */ +} + +static u64 cpu_period_read_u64(struct cgroup_subsys_state *css, + struct cftype *cft) +{ + u64 period_us; + + tg_bandwidth(css_tg(css), &period_us, NULL, NULL); + return period_us; +} + +static int tg_set_bandwidth(struct task_group *tg, + u64 period_us, u64 quota_us, u64 burst_us) +{ + const u64 max_usec = U64_MAX / NSEC_PER_USEC; + int ret = 0; + + if (tg == &root_task_group) + return -EINVAL; + + /* Values should survive translation to nsec */ + if (period_us > max_usec || + (quota_us != RUNTIME_INF && quota_us > max_usec) || + burst_us > max_usec) + return -EINVAL; + + /* + * Ensure we have some amount of bandwidth every period. This is to + * prevent reaching a state of large arrears when throttled via + * entity_tick() resulting in prolonged exit starvation. + */ + if (quota_us < min_bw_quota_period_us || + period_us < min_bw_quota_period_us) + return -EINVAL; + + /* + * Likewise, bound things on the other side by preventing insane quota + * periods. This also allows us to normalize in computing quota + * feasibility. + */ + if (period_us > max_bw_quota_period_us) + return -EINVAL; + + /* + * Bound quota to defend quota against overflow during bandwidth shift. + */ + if (quota_us != RUNTIME_INF && quota_us > max_bw_runtime_us) + return -EINVAL; + + if (quota_us != RUNTIME_INF && (burst_us > quota_us || + burst_us + quota_us > max_bw_runtime_us)) + return -EINVAL; + +#ifdef CONFIG_CFS_BANDWIDTH + ret = tg_set_cfs_bandwidth(tg, period_us, quota_us, burst_us); +#endif /* CONFIG_CFS_BANDWIDTH */ + if (!ret) + scx_group_set_bandwidth(tg, period_us, quota_us, burst_us); + return ret; +} + +static s64 cpu_quota_read_s64(struct cgroup_subsys_state *css, + struct cftype *cft) +{ + u64 quota_us; + + tg_bandwidth(css_tg(css), NULL, "a_us, NULL); + return quota_us; /* (s64)RUNTIME_INF becomes -1 */ +} + +static u64 cpu_burst_read_u64(struct cgroup_subsys_state *css, + struct cftype *cft) +{ + u64 burst_us; + + tg_bandwidth(css_tg(css), NULL, NULL, &burst_us); + return burst_us; +} + +static int cpu_period_write_u64(struct cgroup_subsys_state *css, + struct cftype *cftype, u64 period_us) +{ + struct task_group *tg = css_tg(css); + u64 quota_us, burst_us; + + tg_bandwidth(tg, NULL, "a_us, &burst_us); + return tg_set_bandwidth(tg, period_us, quota_us, burst_us); +} + +static int cpu_quota_write_s64(struct cgroup_subsys_state *css, + struct cftype *cftype, s64 quota_us) +{ + struct task_group *tg = css_tg(css); + u64 period_us, burst_us; + + if (quota_us < 0) + quota_us = RUNTIME_INF; + + tg_bandwidth(tg, &period_us, NULL, &burst_us); + return tg_set_bandwidth(tg, period_us, quota_us, burst_us); +} + +static int cpu_burst_write_u64(struct cgroup_subsys_state *css, + struct cftype *cftype, u64 burst_us) +{ + struct task_group *tg = css_tg(css); + u64 period_us, quota_us; + + tg_bandwidth(tg, &period_us, "a_us, NULL); + return tg_set_bandwidth(tg, period_us, quota_us, burst_us); +} +#endif /* CONFIG_GROUP_SCHED_BANDWIDTH */ #ifdef CONFIG_RT_GROUP_SCHED static int cpu_rt_runtime_write(struct cgroup_subsys_state *css, @@ -6787,31 +9833,84 @@ static u64 cpu_rt_period_read_uint(struct cgroup_subsys_state *css, } #endif /* CONFIG_RT_GROUP_SCHED */ +#ifdef CONFIG_GROUP_SCHED_WEIGHT +static s64 cpu_idle_read_s64(struct cgroup_subsys_state *css, + struct cftype *cft) +{ + return css_tg(css)->idle; +} + +static int cpu_idle_write_s64(struct cgroup_subsys_state *css, + struct cftype *cft, s64 idle) +{ + int ret; + + ret = sched_group_set_idle(css_tg(css), idle); + if (!ret) + scx_group_set_idle(css_tg(css), idle); + return ret; +} +#endif /* CONFIG_GROUP_SCHED_WEIGHT */ + static struct cftype cpu_legacy_files[] = { -#ifdef CONFIG_FAIR_GROUP_SCHED +#ifdef CONFIG_GROUP_SCHED_WEIGHT { .name = "shares", .read_u64 = cpu_shares_read_u64, .write_u64 = cpu_shares_write_u64, }, + { + .name = "idle", + .read_s64 = cpu_idle_read_s64, + .write_s64 = cpu_idle_write_s64, + }, #endif -#ifdef CONFIG_CFS_BANDWIDTH +#ifdef CONFIG_GROUP_SCHED_BANDWIDTH + { + .name = "cfs_period_us", + .read_u64 = cpu_period_read_u64, + .write_u64 = cpu_period_write_u64, + }, { .name = "cfs_quota_us", - .read_s64 = cpu_cfs_quota_read_s64, - .write_s64 = cpu_cfs_quota_write_s64, + .read_s64 = cpu_quota_read_s64, + .write_s64 = cpu_quota_write_s64, }, { - .name = "cfs_period_us", - .read_u64 = cpu_cfs_period_read_u64, - .write_u64 = cpu_cfs_period_write_u64, + .name = "cfs_burst_us", + .read_u64 = cpu_burst_read_u64, + .write_u64 = cpu_burst_write_u64, }, +#endif +#ifdef CONFIG_CFS_BANDWIDTH { .name = "stat", .seq_show = cpu_cfs_stat_show, }, + { + .name = "stat.local", + .seq_show = cpu_cfs_local_stat_show, + }, #endif +#ifdef CONFIG_UCLAMP_TASK_GROUP + { + .name = "uclamp.min", + .flags = CFTYPE_NOT_ON_ROOT, + .seq_show = cpu_uclamp_min_show, + .write = cpu_uclamp_min_write, + }, + { + .name = "uclamp.max", + .flags = CFTYPE_NOT_ON_ROOT, + .seq_show = cpu_uclamp_max_show, + .write = cpu_uclamp_max_write, + }, +#endif + { } /* Terminate */ +}; + #ifdef CONFIG_RT_GROUP_SCHED +static struct cftype rt_group_files[] = { { .name = "rt_runtime_us", .read_s64 = cpu_rt_runtime_read, @@ -6822,10 +9921,43 @@ static struct cftype cpu_legacy_files[] = { .read_u64 = cpu_rt_period_read_uint, .write_u64 = cpu_rt_period_write_uint, }, -#endif { } /* Terminate */ }; +# ifdef CONFIG_RT_GROUP_SCHED_DEFAULT_DISABLED +DEFINE_STATIC_KEY_FALSE(rt_group_sched); +# else +DEFINE_STATIC_KEY_TRUE(rt_group_sched); +# endif + +static int __init setup_rt_group_sched(char *str) +{ + long val; + + if (kstrtol(str, 0, &val) || val < 0 || val > 1) { + pr_warn("Unable to set rt_group_sched\n"); + return 1; + } + if (val) + static_branch_enable(&rt_group_sched); + else + static_branch_disable(&rt_group_sched); + + return 1; +} +__setup("rt_group_sched=", setup_rt_group_sched); + +static int __init cpu_rt_group_init(void) +{ + if (!rt_group_sched_enabled()) + return 0; + + WARN_ON(cgroup_add_legacy_cftypes(&cpu_cgrp_subsys, rt_group_files)); + return 0; +} +subsys_initcall(cpu_rt_group_init); +#endif /* CONFIG_RT_GROUP_SCHED */ + static int cpu_extra_stat_show(struct seq_file *sf, struct cgroup_subsys_state *css) { @@ -6833,53 +9965,72 @@ static int cpu_extra_stat_show(struct seq_file *sf, { struct task_group *tg = css_tg(css); struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth; - u64 throttled_usec; + u64 throttled_usec, burst_usec; throttled_usec = cfs_b->throttled_time; do_div(throttled_usec, NSEC_PER_USEC); + burst_usec = cfs_b->burst_time; + do_div(burst_usec, NSEC_PER_USEC); seq_printf(sf, "nr_periods %d\n" "nr_throttled %d\n" - "throttled_usec %llu\n", + "throttled_usec %llu\n" + "nr_bursts %d\n" + "burst_usec %llu\n", cfs_b->nr_periods, cfs_b->nr_throttled, - throttled_usec); + throttled_usec, cfs_b->nr_burst, burst_usec); + } +#endif /* CONFIG_CFS_BANDWIDTH */ + return 0; +} + +static int cpu_local_stat_show(struct seq_file *sf, + struct cgroup_subsys_state *css) +{ +#ifdef CONFIG_CFS_BANDWIDTH + { + struct task_group *tg = css_tg(css); + u64 throttled_self_usec; + + throttled_self_usec = throttled_time_self(tg); + do_div(throttled_self_usec, NSEC_PER_USEC); + + seq_printf(sf, "throttled_usec %llu\n", + throttled_self_usec); } #endif return 0; } -#ifdef CONFIG_FAIR_GROUP_SCHED +#ifdef CONFIG_GROUP_SCHED_WEIGHT + static u64 cpu_weight_read_u64(struct cgroup_subsys_state *css, struct cftype *cft) { - struct task_group *tg = css_tg(css); - u64 weight = scale_load_down(tg->shares); - - return DIV_ROUND_CLOSEST_ULL(weight * CGROUP_WEIGHT_DFL, 1024); + return sched_weight_to_cgroup(tg_weight(css_tg(css))); } static int cpu_weight_write_u64(struct cgroup_subsys_state *css, - struct cftype *cft, u64 weight) + struct cftype *cft, u64 cgrp_weight) { - /* - * cgroup weight knobs should use the common MIN, DFL and MAX - * values which are 1, 100 and 10000 respectively. While it loses - * a bit of range on both ends, it maps pretty well onto the shares - * value used by scheduler and the round-trip conversions preserve - * the original value over the entire range. - */ - if (weight < CGROUP_WEIGHT_MIN || weight > CGROUP_WEIGHT_MAX) + unsigned long weight; + int ret; + + if (cgrp_weight < CGROUP_WEIGHT_MIN || cgrp_weight > CGROUP_WEIGHT_MAX) return -ERANGE; - weight = DIV_ROUND_CLOSEST_ULL(weight * 1024, CGROUP_WEIGHT_DFL); + weight = sched_weight_from_cgroup(cgrp_weight); - return sched_group_set_shares(css_tg(css), scale_load(weight)); + ret = sched_group_set_shares(css_tg(css), scale_load(weight)); + if (!ret) + scx_group_set_weight(css_tg(css), cgrp_weight); + return ret; } static s64 cpu_weight_nice_read_s64(struct cgroup_subsys_state *css, struct cftype *cft) { - unsigned long weight = scale_load_down(css_tg(css)->shares); + unsigned long weight = tg_weight(css_tg(css)); int last_delta = INT_MAX; int prio, delta; @@ -6898,7 +10049,7 @@ static int cpu_weight_nice_write_s64(struct cgroup_subsys_state *css, struct cftype *cft, s64 nice) { unsigned long weight; - int idx; + int idx, ret; if (nice < MIN_NICE || nice > MAX_NICE) return -ERANGE; @@ -6907,9 +10058,13 @@ static int cpu_weight_nice_write_s64(struct cgroup_subsys_state *css, idx = array_index_nospec(idx, 40); weight = sched_prio_to_weight[idx]; - return sched_group_set_shares(css_tg(css), scale_load(weight)); + ret = sched_group_set_shares(css_tg(css), scale_load(weight)); + if (!ret) + scx_group_set_weight(css_tg(css), + sched_weight_to_cgroup(weight)); + return ret; } -#endif +#endif /* CONFIG_GROUP_SCHED_WEIGHT */ static void __maybe_unused cpu_period_quota_print(struct seq_file *sf, long period, long quota) @@ -6923,32 +10078,32 @@ static void __maybe_unused cpu_period_quota_print(struct seq_file *sf, } /* caller should put the current value in *@periodp before calling */ -static int __maybe_unused cpu_period_quota_parse(char *buf, - u64 *periodp, u64 *quotap) +static int __maybe_unused cpu_period_quota_parse(char *buf, u64 *period_us_p, + u64 *quota_us_p) { char tok[21]; /* U64_MAX */ - if (!sscanf(buf, "%s %llu", tok, periodp)) + if (sscanf(buf, "%20s %llu", tok, period_us_p) < 1) return -EINVAL; - *periodp *= NSEC_PER_USEC; - - if (sscanf(tok, "%llu", quotap)) - *quotap *= NSEC_PER_USEC; - else if (!strcmp(tok, "max")) - *quotap = RUNTIME_INF; - else - return -EINVAL; + if (sscanf(tok, "%llu", quota_us_p) < 1) { + if (!strcmp(tok, "max")) + *quota_us_p = RUNTIME_INF; + else + return -EINVAL; + } return 0; } -#ifdef CONFIG_CFS_BANDWIDTH +#ifdef CONFIG_GROUP_SCHED_BANDWIDTH static int cpu_max_show(struct seq_file *sf, void *v) { struct task_group *tg = css_tg(seq_css(sf)); + u64 period_us, quota_us; - cpu_period_quota_print(sf, tg_get_cfs_period(tg), tg_get_cfs_quota(tg)); + tg_bandwidth(tg, &period_us, "a_us, NULL); + cpu_period_quota_print(sf, period_us, quota_us); return 0; } @@ -6956,19 +10111,19 @@ static ssize_t cpu_max_write(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off) { struct task_group *tg = css_tg(of_css(of)); - u64 period = tg_get_cfs_period(tg); - u64 quota; + u64 period_us, quota_us, burst_us; int ret; - ret = cpu_period_quota_parse(buf, &period, "a); + tg_bandwidth(tg, &period_us, NULL, &burst_us); + ret = cpu_period_quota_parse(buf, &period_us, "a_us); if (!ret) - ret = tg_set_cfs_bandwidth(tg, period, quota); + ret = tg_set_bandwidth(tg, period_us, quota_us, burst_us); return ret ?: nbytes; } -#endif +#endif /* CONFIG_CFS_BANDWIDTH */ static struct cftype cpu_files[] = { -#ifdef CONFIG_FAIR_GROUP_SCHED +#ifdef CONFIG_GROUP_SCHED_WEIGHT { .name = "weight", .flags = CFTYPE_NOT_ON_ROOT, @@ -6981,37 +10136,78 @@ static struct cftype cpu_files[] = { .read_s64 = cpu_weight_nice_read_s64, .write_s64 = cpu_weight_nice_write_s64, }, + { + .name = "idle", + .flags = CFTYPE_NOT_ON_ROOT, + .read_s64 = cpu_idle_read_s64, + .write_s64 = cpu_idle_write_s64, + }, #endif -#ifdef CONFIG_CFS_BANDWIDTH +#ifdef CONFIG_GROUP_SCHED_BANDWIDTH { .name = "max", .flags = CFTYPE_NOT_ON_ROOT, .seq_show = cpu_max_show, .write = cpu_max_write, }, -#endif + { + .name = "max.burst", + .flags = CFTYPE_NOT_ON_ROOT, + .read_u64 = cpu_burst_read_u64, + .write_u64 = cpu_burst_write_u64, + }, +#endif /* CONFIG_CFS_BANDWIDTH */ +#ifdef CONFIG_UCLAMP_TASK_GROUP + { + .name = "uclamp.min", + .flags = CFTYPE_NOT_ON_ROOT, + .seq_show = cpu_uclamp_min_show, + .write = cpu_uclamp_min_write, + }, + { + .name = "uclamp.max", + .flags = CFTYPE_NOT_ON_ROOT, + .seq_show = cpu_uclamp_max_show, + .write = cpu_uclamp_max_write, + }, +#endif /* CONFIG_UCLAMP_TASK_GROUP */ { } /* terminate */ }; struct cgroup_subsys cpu_cgrp_subsys = { .css_alloc = cpu_cgroup_css_alloc, .css_online = cpu_cgroup_css_online, + .css_offline = cpu_cgroup_css_offline, .css_released = cpu_cgroup_css_released, .css_free = cpu_cgroup_css_free, .css_extra_stat_show = cpu_extra_stat_show, - .fork = cpu_cgroup_fork, + .css_local_stat_show = cpu_local_stat_show, .can_attach = cpu_cgroup_can_attach, .attach = cpu_cgroup_attach, + .cancel_attach = cpu_cgroup_cancel_attach, .legacy_cftypes = cpu_legacy_files, .dfl_cftypes = cpu_files, .early_init = true, .threaded = true, }; -#endif /* CONFIG_CGROUP_SCHED */ +#endif /* CONFIG_CGROUP_SCHED */ void dump_cpu_task(int cpu) { + if (in_hardirq() && cpu == smp_processor_id()) { + struct pt_regs *regs; + + regs = get_irq_regs(); + if (regs) { + show_regs(regs); + return; + } + } + + if (trigger_single_cpu_backtrace(cpu)) + return; + pr_info("Task dump for CPU %d:\n", cpu); sched_show_task(cpu_curr(cpu)); } @@ -7040,10 +10236,10 @@ const int sched_prio_to_weight[40] = { }; /* - * Inverse (2^32/x) values of the sched_prio_to_weight[] array, precalculated. + * Inverse (2^32/x) values of the sched_prio_to_weight[] array, pre-calculated. * * In cases where the weight does not change often, we can use the - * precalculated inverse to speed up arithmetics by turning divisions + * pre-calculated inverse to speed up arithmetics by turning divisions * into multiplications: */ const u32 sched_prio_to_wmult[40] = { @@ -7057,4 +10253,577 @@ const u32 sched_prio_to_wmult[40] = { /* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153, }; -#undef CREATE_TRACE_POINTS +void call_trace_sched_update_nr_running(struct rq *rq, int count) +{ + trace_sched_update_nr_running_tp(rq, count); +} + +#ifdef CONFIG_SCHED_MM_CID +/* + * Concurrency IDentifier management + * + * Serialization rules: + * + * mm::mm_cid::mutex: Serializes fork() and exit() and therefore + * protects mm::mm_cid::users. + * + * mm::mm_cid::lock: Serializes mm_update_max_cids() and + * mm_update_cpus_allowed(). Nests in mm_cid::mutex + * and runqueue lock. + * + * The mm_cidmask bitmap is not protected by any of the mm::mm_cid locks + * and can only be modified with atomic operations. + * + * The mm::mm_cid:pcpu per CPU storage is protected by the CPUs runqueue + * lock. + * + * CID ownership: + * + * A CID is either owned by a task (stored in task_struct::mm_cid.cid) or + * by a CPU (stored in mm::mm_cid.pcpu::cid). CIDs owned by CPUs have the + * MM_CID_ONCPU bit set. During transition from CPU to task ownership mode, + * MM_CID_TRANSIT is set on the per task CIDs. When this bit is set the + * task needs to drop the CID into the pool when scheduling out. Both bits + * (ONCPU and TRANSIT) are filtered out by task_cid() when the CID is + * actually handed over to user space in the RSEQ memory. + * + * Mode switching: + * + * Switching to per CPU mode happens when the user count becomes greater + * than the maximum number of CIDs, which is calculated by: + * + * opt_cids = min(mm_cid::nr_cpus_allowed, mm_cid::users); + * max_cids = min(1.25 * opt_cids, num_possible_cpus()); + * + * The +25% allowance is useful for tight CPU masks in scenarios where only + * a few threads are created and destroyed to avoid frequent mode + * switches. Though this allowance shrinks, the closer opt_cids becomes to + * num_possible_cpus(), which is the (unfortunate) hard ABI limit. + * + * At the point of switching to per CPU mode the new user is not yet + * visible in the system, so the task which initiated the fork() runs the + * fixup function: mm_cid_fixup_tasks_to_cpu() walks the thread list and + * either transfers each tasks owned CID to the CPU the task runs on or + * drops it into the CID pool if a task is not on a CPU at that point in + * time. Tasks which schedule in before the task walk reaches them do the + * handover in mm_cid_schedin(). When mm_cid_fixup_tasks_to_cpus() completes + * it's guaranteed that no task related to that MM owns a CID anymore. + * + * Switching back to task mode happens when the user count goes below the + * threshold which was recorded on the per CPU mode switch: + * + * pcpu_thrs = min(opt_cids - (opt_cids / 4), num_possible_cpus() / 2); + * + * This threshold is updated when a affinity change increases the number of + * allowed CPUs for the MM, which might cause a switch back to per task + * mode. + * + * If the switch back was initiated by a exiting task, then that task runs + * the fixup function. If it was initiated by a affinity change, then it's + * run either in the deferred update function in context of a workqueue or + * by a task which forks a new one or by a task which exits. Whatever + * happens first. mm_cid_fixup_cpus_to_task() walks through the possible + * CPUs and either transfers the CPU owned CIDs to a related task which + * runs on the CPU or drops it into the pool. Tasks which schedule in on a + * CPU which the walk did not cover yet do the handover themself. + * + * This transition from CPU to per task ownership happens in two phases: + * + * 1) mm:mm_cid.transit contains MM_CID_TRANSIT This is OR'ed on the task + * CID and denotes that the CID is only temporarily owned by the + * task. When it schedules out the task drops the CID back into the + * pool if this bit is set. + * + * 2) The initiating context walks the per CPU space and after completion + * clears mm:mm_cid.transit. So after that point the CIDs are strictly + * task owned again. + * + * This two phase transition is required to prevent CID space exhaustion + * during the transition as a direct transfer of ownership would fail if + * two tasks are scheduled in on the same CPU before the fixup freed per + * CPU CIDs. + * + * When mm_cid_fixup_cpus_to_tasks() completes it's guaranteed that no CID + * related to that MM is owned by a CPU anymore. + */ + +/* + * Update the CID range properties when the constraints change. Invoked via + * fork(), exit() and affinity changes + */ +static void __mm_update_max_cids(struct mm_mm_cid *mc) +{ + unsigned int opt_cids, max_cids; + + /* Calculate the new optimal constraint */ + opt_cids = min(mc->nr_cpus_allowed, mc->users); + + /* Adjust the maximum CIDs to +25% limited by the number of possible CPUs */ + max_cids = min(opt_cids + (opt_cids / 4), num_possible_cpus()); + WRITE_ONCE(mc->max_cids, max_cids); +} + +static inline unsigned int mm_cid_calc_pcpu_thrs(struct mm_mm_cid *mc) +{ + unsigned int opt_cids; + + opt_cids = min(mc->nr_cpus_allowed, mc->users); + /* Has to be at least 1 because 0 indicates PCPU mode off */ + return max(min(opt_cids - opt_cids / 4, num_possible_cpus() / 2), 1); +} + +static bool mm_update_max_cids(struct mm_struct *mm) +{ + struct mm_mm_cid *mc = &mm->mm_cid; + + lockdep_assert_held(&mm->mm_cid.lock); + + /* Clear deferred mode switch flag. A change is handled by the caller */ + mc->update_deferred = false; + __mm_update_max_cids(mc); + + /* Check whether owner mode must be changed */ + if (!mc->percpu) { + /* Enable per CPU mode when the number of users is above max_cids */ + if (mc->users > mc->max_cids) + mc->pcpu_thrs = mm_cid_calc_pcpu_thrs(mc); + } else { + /* Switch back to per task if user count under threshold */ + if (mc->users < mc->pcpu_thrs) + mc->pcpu_thrs = 0; + } + + /* Mode change required? */ + if (!!mc->percpu == !!mc->pcpu_thrs) + return false; + /* When switching back to per TASK mode, set the transition flag */ + if (!mc->pcpu_thrs) + WRITE_ONCE(mc->transit, MM_CID_TRANSIT); + WRITE_ONCE(mc->percpu, !!mc->pcpu_thrs); + return true; +} + +static inline void mm_update_cpus_allowed(struct mm_struct *mm, const struct cpumask *affmsk) +{ + struct cpumask *mm_allowed; + struct mm_mm_cid *mc; + unsigned int weight; + + if (!mm || !READ_ONCE(mm->mm_cid.users)) + return; + /* + * mm::mm_cid::mm_cpus_allowed is the superset of each threads + * allowed CPUs mask which means it can only grow. + */ + mc = &mm->mm_cid; + guard(raw_spinlock)(&mc->lock); + mm_allowed = mm_cpus_allowed(mm); + weight = cpumask_weighted_or(mm_allowed, mm_allowed, affmsk); + if (weight == mc->nr_cpus_allowed) + return; + + WRITE_ONCE(mc->nr_cpus_allowed, weight); + __mm_update_max_cids(mc); + if (!mc->percpu) + return; + + /* Adjust the threshold to the wider set */ + mc->pcpu_thrs = mm_cid_calc_pcpu_thrs(mc); + /* Switch back to per task mode? */ + if (mc->users >= mc->pcpu_thrs) + return; + + /* Don't queue twice */ + if (mc->update_deferred) + return; + + /* Queue the irq work, which schedules the real work */ + mc->update_deferred = true; + irq_work_queue(&mc->irq_work); +} + +static inline void mm_cid_transit_to_task(struct task_struct *t, struct mm_cid_pcpu *pcp) +{ + if (cid_on_cpu(t->mm_cid.cid)) { + unsigned int cid = cpu_cid_to_cid(t->mm_cid.cid); + + t->mm_cid.cid = cid_to_transit_cid(cid); + pcp->cid = t->mm_cid.cid; + } +} + +static void mm_cid_fixup_cpus_to_tasks(struct mm_struct *mm) +{ + unsigned int cpu; + + /* Walk the CPUs and fixup all stale CIDs */ + for_each_possible_cpu(cpu) { + struct mm_cid_pcpu *pcp = per_cpu_ptr(mm->mm_cid.pcpu, cpu); + struct rq *rq = cpu_rq(cpu); + + /* Remote access to mm::mm_cid::pcpu requires rq_lock */ + guard(rq_lock_irq)(rq); + /* Is the CID still owned by the CPU? */ + if (cid_on_cpu(pcp->cid)) { + /* + * If rq->curr has @mm, transfer it with the + * transition bit set. Otherwise drop it. + */ + if (rq->curr->mm == mm && rq->curr->mm_cid.active) + mm_cid_transit_to_task(rq->curr, pcp); + else + mm_drop_cid_on_cpu(mm, pcp); + + } else if (rq->curr->mm == mm && rq->curr->mm_cid.active) { + unsigned int cid = rq->curr->mm_cid.cid; + + /* Ensure it has the transition bit set */ + if (!cid_in_transit(cid)) { + cid = cid_to_transit_cid(cid); + rq->curr->mm_cid.cid = cid; + pcp->cid = cid; + } + } + } + /* Clear the transition bit */ + WRITE_ONCE(mm->mm_cid.transit, 0); +} + +static inline void mm_cid_transfer_to_cpu(struct task_struct *t, struct mm_cid_pcpu *pcp) +{ + if (cid_on_task(t->mm_cid.cid)) { + t->mm_cid.cid = cid_to_cpu_cid(t->mm_cid.cid); + pcp->cid = t->mm_cid.cid; + } +} + +static bool mm_cid_fixup_task_to_cpu(struct task_struct *t, struct mm_struct *mm) +{ + /* Remote access to mm::mm_cid::pcpu requires rq_lock */ + guard(task_rq_lock)(t); + /* If the task is not active it is not in the users count */ + if (!t->mm_cid.active) + return false; + if (cid_on_task(t->mm_cid.cid)) { + /* If running on the CPU, transfer the CID, otherwise drop it */ + if (task_rq(t)->curr == t) + mm_cid_transfer_to_cpu(t, per_cpu_ptr(mm->mm_cid.pcpu, task_cpu(t))); + else + mm_unset_cid_on_task(t); + } + return true; +} + +static void mm_cid_fixup_tasks_to_cpus(void) +{ + struct mm_struct *mm = current->mm; + struct task_struct *p, *t; + unsigned int users; + + /* + * This can obviously race with a concurrent affinity change, which + * increases the number of allowed CPUs for this mm, but that does + * not affect the mode and only changes the CID constraints. A + * possible switch back to per task mode happens either in the + * deferred handler function or in the next fork()/exit(). + * + * The caller has already transferred. The newly incoming task is + * already accounted for, but not yet visible. + */ + users = mm->mm_cid.users - 2; + if (!users) + return; + + guard(rcu)(); + for_other_threads(current, t) { + if (mm_cid_fixup_task_to_cpu(t, mm)) + users--; + } + + if (!users) + return; + + /* Happens only for VM_CLONE processes. */ + for_each_process_thread(p, t) { + if (t == current || t->mm != mm) + continue; + if (mm_cid_fixup_task_to_cpu(t, mm)) { + if (--users == 0) + return; + } + } +} + +static bool sched_mm_cid_add_user(struct task_struct *t, struct mm_struct *mm) +{ + t->mm_cid.active = 1; + mm->mm_cid.users++; + return mm_update_max_cids(mm); +} + +void sched_mm_cid_fork(struct task_struct *t) +{ + struct mm_struct *mm = t->mm; + bool percpu; + + WARN_ON_ONCE(!mm || t->mm_cid.cid != MM_CID_UNSET); + + guard(mutex)(&mm->mm_cid.mutex); + scoped_guard(raw_spinlock_irq, &mm->mm_cid.lock) { + struct mm_cid_pcpu *pcp = this_cpu_ptr(mm->mm_cid.pcpu); + + /* First user ? */ + if (!mm->mm_cid.users) { + sched_mm_cid_add_user(t, mm); + t->mm_cid.cid = mm_get_cid(mm); + /* Required for execve() */ + pcp->cid = t->mm_cid.cid; + return; + } + + if (!sched_mm_cid_add_user(t, mm)) { + if (!mm->mm_cid.percpu) + t->mm_cid.cid = mm_get_cid(mm); + return; + } + + /* Handle the mode change and transfer current's CID */ + percpu = !!mm->mm_cid.percpu; + if (!percpu) + mm_cid_transit_to_task(current, pcp); + else + mm_cid_transfer_to_cpu(current, pcp); + } + + if (percpu) { + mm_cid_fixup_tasks_to_cpus(); + } else { + mm_cid_fixup_cpus_to_tasks(mm); + t->mm_cid.cid = mm_get_cid(mm); + } +} + +static bool sched_mm_cid_remove_user(struct task_struct *t) +{ + t->mm_cid.active = 0; + scoped_guard(preempt) { + /* Clear the transition bit */ + t->mm_cid.cid = cid_from_transit_cid(t->mm_cid.cid); + mm_unset_cid_on_task(t); + } + t->mm->mm_cid.users--; + return mm_update_max_cids(t->mm); +} + +static bool __sched_mm_cid_exit(struct task_struct *t) +{ + struct mm_struct *mm = t->mm; + + if (!sched_mm_cid_remove_user(t)) + return false; + /* + * Contrary to fork() this only deals with a switch back to per + * task mode either because the above decreased users or an + * affinity change increased the number of allowed CPUs and the + * deferred fixup did not run yet. + */ + if (WARN_ON_ONCE(mm->mm_cid.percpu)) + return false; + /* + * A failed fork(2) cleanup never gets here, so @current must have + * the same MM as @t. That's true for exit() and the failed + * pthread_create() cleanup case. + */ + if (WARN_ON_ONCE(current->mm != mm)) + return false; + return true; +} + +/* + * When a task exits, the MM CID held by the task is not longer required as + * the task cannot return to user space. + */ +void sched_mm_cid_exit(struct task_struct *t) +{ + struct mm_struct *mm = t->mm; + + if (!mm || !t->mm_cid.active) + return; + /* + * Ensure that only one instance is doing MM CID operations within + * a MM. The common case is uncontended. The rare fixup case adds + * some overhead. + */ + scoped_guard(mutex, &mm->mm_cid.mutex) { + /* mm_cid::mutex is sufficient to protect mm_cid::users */ + if (likely(mm->mm_cid.users > 1)) { + scoped_guard(raw_spinlock_irq, &mm->mm_cid.lock) { + if (!__sched_mm_cid_exit(t)) + return; + /* Mode change required. Transfer currents CID */ + mm_cid_transit_to_task(current, this_cpu_ptr(mm->mm_cid.pcpu)); + } + mm_cid_fixup_cpus_to_tasks(mm); + return; + } + /* Last user */ + scoped_guard(raw_spinlock_irq, &mm->mm_cid.lock) { + /* Required across execve() */ + if (t == current) + mm_cid_transit_to_task(t, this_cpu_ptr(mm->mm_cid.pcpu)); + /* Ignore mode change. There is nothing to do. */ + sched_mm_cid_remove_user(t); + } + } + + /* + * As this is the last user (execve(), process exit or failed + * fork(2)) there is no concurrency anymore. + * + * Synchronize eventually pending work to ensure that there are no + * dangling references left. @t->mm_cid.users is zero so nothing + * can queue this work anymore. + */ + irq_work_sync(&mm->mm_cid.irq_work); + cancel_work_sync(&mm->mm_cid.work); +} + +/* Deactivate MM CID allocation across execve() */ +void sched_mm_cid_before_execve(struct task_struct *t) +{ + sched_mm_cid_exit(t); +} + +/* Reactivate MM CID after successful execve() */ +void sched_mm_cid_after_execve(struct task_struct *t) +{ + sched_mm_cid_fork(t); +} + +static void mm_cid_work_fn(struct work_struct *work) +{ + struct mm_struct *mm = container_of(work, struct mm_struct, mm_cid.work); + + guard(mutex)(&mm->mm_cid.mutex); + /* Did the last user task exit already? */ + if (!mm->mm_cid.users) + return; + + scoped_guard(raw_spinlock_irq, &mm->mm_cid.lock) { + /* Have fork() or exit() handled it already? */ + if (!mm->mm_cid.update_deferred) + return; + /* This clears mm_cid::update_deferred */ + if (!mm_update_max_cids(mm)) + return; + /* Affinity changes can only switch back to task mode */ + if (WARN_ON_ONCE(mm->mm_cid.percpu)) + return; + } + mm_cid_fixup_cpus_to_tasks(mm); +} + +static void mm_cid_irq_work(struct irq_work *work) +{ + struct mm_struct *mm = container_of(work, struct mm_struct, mm_cid.irq_work); + + /* + * Needs to be unconditional because mm_cid::lock cannot be held + * when scheduling work as mm_update_cpus_allowed() nests inside + * rq::lock and schedule_work() might end up in wakeup... + */ + schedule_work(&mm->mm_cid.work); +} + +void mm_init_cid(struct mm_struct *mm, struct task_struct *p) +{ + mm->mm_cid.max_cids = 0; + mm->mm_cid.percpu = 0; + mm->mm_cid.transit = 0; + mm->mm_cid.nr_cpus_allowed = p->nr_cpus_allowed; + mm->mm_cid.users = 0; + mm->mm_cid.pcpu_thrs = 0; + mm->mm_cid.update_deferred = 0; + raw_spin_lock_init(&mm->mm_cid.lock); + mutex_init(&mm->mm_cid.mutex); + mm->mm_cid.irq_work = IRQ_WORK_INIT_HARD(mm_cid_irq_work); + INIT_WORK(&mm->mm_cid.work, mm_cid_work_fn); + cpumask_copy(mm_cpus_allowed(mm), &p->cpus_mask); + bitmap_zero(mm_cidmask(mm), num_possible_cpus()); +} +#else /* CONFIG_SCHED_MM_CID */ +static inline void mm_update_cpus_allowed(struct mm_struct *mm, const struct cpumask *affmsk) { } +#endif /* !CONFIG_SCHED_MM_CID */ + +static DEFINE_PER_CPU(struct sched_change_ctx, sched_change_ctx); + +struct sched_change_ctx *sched_change_begin(struct task_struct *p, unsigned int flags) +{ + struct sched_change_ctx *ctx = this_cpu_ptr(&sched_change_ctx); + struct rq *rq = task_rq(p); + + /* + * Must exclusively use matched flags since this is both dequeue and + * enqueue. + */ + WARN_ON_ONCE(flags & 0xFFFF0000); + + lockdep_assert_rq_held(rq); + + if (!(flags & DEQUEUE_NOCLOCK)) { + update_rq_clock(rq); + flags |= DEQUEUE_NOCLOCK; + } + + if (flags & DEQUEUE_CLASS) { + if (p->sched_class->switching_from) + p->sched_class->switching_from(rq, p); + } + + *ctx = (struct sched_change_ctx){ + .p = p, + .flags = flags, + .queued = task_on_rq_queued(p), + .running = task_current_donor(rq, p), + }; + + if (!(flags & DEQUEUE_CLASS)) { + if (p->sched_class->get_prio) + ctx->prio = p->sched_class->get_prio(rq, p); + else + ctx->prio = p->prio; + } + + if (ctx->queued) + dequeue_task(rq, p, flags); + if (ctx->running) + put_prev_task(rq, p); + + if ((flags & DEQUEUE_CLASS) && p->sched_class->switched_from) + p->sched_class->switched_from(rq, p); + + return ctx; +} + +void sched_change_end(struct sched_change_ctx *ctx) +{ + struct task_struct *p = ctx->p; + struct rq *rq = task_rq(p); + + lockdep_assert_rq_held(rq); + + if ((ctx->flags & ENQUEUE_CLASS) && p->sched_class->switching_to) + p->sched_class->switching_to(rq, p); + + if (ctx->queued) + enqueue_task(rq, p, ctx->flags); + if (ctx->running) + set_next_task(rq, p); + + if (ctx->flags & ENQUEUE_CLASS) { + if (p->sched_class->switched_to) + p->sched_class->switched_to(rq, p); + } else { + p->sched_class->prio_changed(rq, p, ctx->prio); + } +} |