diff options
Diffstat (limited to 'kernel/smp.c')
| -rw-r--r-- | kernel/smp.c | 1185 |
1 files changed, 832 insertions, 353 deletions
diff --git a/kernel/smp.c b/kernel/smp.c index 4dba0f7b72ad..f349960f79ca 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -1,96 +1,313 @@ +// SPDX-License-Identifier: GPL-2.0-only /* * Generic helpers for smp ipi calls * * (C) Jens Axboe <jens.axboe@oracle.com> 2008 */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/irq_work.h> #include <linux/rcupdate.h> #include <linux/rculist.h> #include <linux/kernel.h> #include <linux/export.h> #include <linux/percpu.h> #include <linux/init.h> +#include <linux/interrupt.h> #include <linux/gfp.h> #include <linux/smp.h> #include <linux/cpu.h> +#include <linux/sched.h> +#include <linux/sched/idle.h> +#include <linux/hypervisor.h> +#include <linux/sched/clock.h> +#include <linux/nmi.h> +#include <linux/sched/debug.h> +#include <linux/jump_label.h> +#include <linux/string_choices.h> + +#include <trace/events/ipi.h> +#define CREATE_TRACE_POINTS +#include <trace/events/csd.h> +#undef CREATE_TRACE_POINTS #include "smpboot.h" +#include "sched/smp.h" -#ifdef CONFIG_USE_GENERIC_SMP_HELPERS -enum { - CSD_FLAG_LOCK = 0x01, -}; +#define CSD_TYPE(_csd) ((_csd)->node.u_flags & CSD_FLAG_TYPE_MASK) struct call_function_data { - struct call_single_data __percpu *csd; + call_single_data_t __percpu *csd; cpumask_var_t cpumask; cpumask_var_t cpumask_ipi; }; -static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data); +static DEFINE_PER_CPU_ALIGNED(struct call_function_data, cfd_data); -struct call_single_queue { - struct list_head list; - raw_spinlock_t lock; -}; +static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue); -static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_queue, call_single_queue); +static DEFINE_PER_CPU(atomic_t, trigger_backtrace) = ATOMIC_INIT(1); -static int -hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu) +static void __flush_smp_call_function_queue(bool warn_cpu_offline); + +int smpcfd_prepare_cpu(unsigned int cpu) { - long cpu = (long)hcpu; struct call_function_data *cfd = &per_cpu(cfd_data, cpu); - switch (action) { - case CPU_UP_PREPARE: - case CPU_UP_PREPARE_FROZEN: - if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL, - cpu_to_node(cpu))) - return notifier_from_errno(-ENOMEM); - if (!zalloc_cpumask_var_node(&cfd->cpumask_ipi, GFP_KERNEL, - cpu_to_node(cpu))) - return notifier_from_errno(-ENOMEM); - cfd->csd = alloc_percpu(struct call_single_data); - if (!cfd->csd) { - free_cpumask_var(cfd->cpumask); - return notifier_from_errno(-ENOMEM); - } - break; - -#ifdef CONFIG_HOTPLUG_CPU - case CPU_UP_CANCELED: - case CPU_UP_CANCELED_FROZEN: - - case CPU_DEAD: - case CPU_DEAD_FROZEN: + if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL, + cpu_to_node(cpu))) + return -ENOMEM; + if (!zalloc_cpumask_var_node(&cfd->cpumask_ipi, GFP_KERNEL, + cpu_to_node(cpu))) { + free_cpumask_var(cfd->cpumask); + return -ENOMEM; + } + cfd->csd = alloc_percpu(call_single_data_t); + if (!cfd->csd) { free_cpumask_var(cfd->cpumask); free_cpumask_var(cfd->cpumask_ipi); - free_percpu(cfd->csd); - break; -#endif - }; + return -ENOMEM; + } - return NOTIFY_OK; + return 0; } -static struct notifier_block __cpuinitdata hotplug_cfd_notifier = { - .notifier_call = hotplug_cfd, -}; +int smpcfd_dead_cpu(unsigned int cpu) +{ + struct call_function_data *cfd = &per_cpu(cfd_data, cpu); + + free_cpumask_var(cfd->cpumask); + free_cpumask_var(cfd->cpumask_ipi); + free_percpu(cfd->csd); + return 0; +} + +int smpcfd_dying_cpu(unsigned int cpu) +{ + /* + * The IPIs for the smp-call-function callbacks queued by other CPUs + * might arrive late, either due to hardware latencies or because this + * CPU disabled interrupts (inside stop-machine) before the IPIs were + * sent. So flush out any pending callbacks explicitly (without waiting + * for the IPIs to arrive), to ensure that the outgoing CPU doesn't go + * offline with work still pending. + * + * This runs with interrupts disabled inside the stopper task invoked by + * stop_machine(), ensuring mutually exclusive CPU offlining and IPI flush. + */ + __flush_smp_call_function_queue(false); + irq_work_run(); + return 0; +} void __init call_function_init(void) { - void *cpu = (void *)(long)smp_processor_id(); int i; - for_each_possible_cpu(i) { - struct call_single_queue *q = &per_cpu(call_single_queue, i); + for_each_possible_cpu(i) + init_llist_head(&per_cpu(call_single_queue, i)); + + smpcfd_prepare_cpu(smp_processor_id()); +} - raw_spin_lock_init(&q->lock); - INIT_LIST_HEAD(&q->list); +static __always_inline void +send_call_function_single_ipi(int cpu) +{ + if (call_function_single_prep_ipi(cpu)) { + trace_ipi_send_cpu(cpu, _RET_IP_, + generic_smp_call_function_single_interrupt); + arch_send_call_function_single_ipi(cpu); } +} - hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu); - register_cpu_notifier(&hotplug_cfd_notifier); +static __always_inline void +send_call_function_ipi_mask(struct cpumask *mask) +{ + trace_ipi_send_cpumask(mask, _RET_IP_, + generic_smp_call_function_single_interrupt); + arch_send_call_function_ipi_mask(mask); +} + +static __always_inline void +csd_do_func(smp_call_func_t func, void *info, call_single_data_t *csd) +{ + trace_csd_function_entry(func, csd); + func(info); + trace_csd_function_exit(func, csd); +} + +#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG + +static DEFINE_STATIC_KEY_MAYBE(CONFIG_CSD_LOCK_WAIT_DEBUG_DEFAULT, csdlock_debug_enabled); + +/* + * Parse the csdlock_debug= kernel boot parameter. + * + * If you need to restore the old "ext" value that once provided + * additional debugging information, reapply the following commits: + * + * de7b09ef658d ("locking/csd_lock: Prepare more CSD lock debugging") + * a5aabace5fb8 ("locking/csd_lock: Add more data to CSD lock debugging") + */ +static int __init csdlock_debug(char *str) +{ + int ret; + unsigned int val = 0; + + ret = get_option(&str, &val); + if (ret) { + if (val) + static_branch_enable(&csdlock_debug_enabled); + else + static_branch_disable(&csdlock_debug_enabled); + } + + return 1; +} +__setup("csdlock_debug=", csdlock_debug); + +static DEFINE_PER_CPU(call_single_data_t *, cur_csd); +static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func); +static DEFINE_PER_CPU(void *, cur_csd_info); + +static ulong csd_lock_timeout = 5000; /* CSD lock timeout in milliseconds. */ +module_param(csd_lock_timeout, ulong, 0644); +static int panic_on_ipistall; /* CSD panic timeout in milliseconds, 300000 for five minutes. */ +module_param(panic_on_ipistall, int, 0644); + +static atomic_t csd_bug_count = ATOMIC_INIT(0); + +/* Record current CSD work for current CPU, NULL to erase. */ +static void __csd_lock_record(call_single_data_t *csd) +{ + if (!csd) { + smp_mb(); /* NULL cur_csd after unlock. */ + __this_cpu_write(cur_csd, NULL); + return; + } + __this_cpu_write(cur_csd_func, csd->func); + __this_cpu_write(cur_csd_info, csd->info); + smp_wmb(); /* func and info before csd. */ + __this_cpu_write(cur_csd, csd); + smp_mb(); /* Update cur_csd before function call. */ + /* Or before unlock, as the case may be. */ +} + +static __always_inline void csd_lock_record(call_single_data_t *csd) +{ + if (static_branch_unlikely(&csdlock_debug_enabled)) + __csd_lock_record(csd); +} + +static int csd_lock_wait_getcpu(call_single_data_t *csd) +{ + unsigned int csd_type; + + csd_type = CSD_TYPE(csd); + if (csd_type == CSD_TYPE_ASYNC || csd_type == CSD_TYPE_SYNC) + return csd->node.dst; /* Other CSD_TYPE_ values might not have ->dst. */ + return -1; +} + +static atomic_t n_csd_lock_stuck; + +/** + * csd_lock_is_stuck - Has a CSD-lock acquisition been stuck too long? + * + * Returns @true if a CSD-lock acquisition is stuck and has been stuck + * long enough for a "non-responsive CSD lock" message to be printed. + */ +bool csd_lock_is_stuck(void) +{ + return !!atomic_read(&n_csd_lock_stuck); +} + +/* + * Complain if too much time spent waiting. Note that only + * the CSD_TYPE_SYNC/ASYNC types provide the destination CPU, + * so waiting on other types gets much less information. + */ +static bool csd_lock_wait_toolong(call_single_data_t *csd, u64 ts0, u64 *ts1, int *bug_id, unsigned long *nmessages) +{ + int cpu = -1; + int cpux; + bool firsttime; + u64 ts2, ts_delta; + call_single_data_t *cpu_cur_csd; + unsigned int flags = READ_ONCE(csd->node.u_flags); + unsigned long long csd_lock_timeout_ns = csd_lock_timeout * NSEC_PER_MSEC; + + if (!(flags & CSD_FLAG_LOCK)) { + if (!unlikely(*bug_id)) + return true; + cpu = csd_lock_wait_getcpu(csd); + pr_alert("csd: CSD lock (#%d) got unstuck on CPU#%02d, CPU#%02d released the lock.\n", + *bug_id, raw_smp_processor_id(), cpu); + atomic_dec(&n_csd_lock_stuck); + return true; + } + + ts2 = ktime_get_mono_fast_ns(); + /* How long since we last checked for a stuck CSD lock.*/ + ts_delta = ts2 - *ts1; + if (likely(ts_delta <= csd_lock_timeout_ns * (*nmessages + 1) * + (!*nmessages ? 1 : (ilog2(num_online_cpus()) / 2 + 1)) || + csd_lock_timeout_ns == 0)) + return false; + + if (ts0 > ts2) { + /* Our own sched_clock went backward; don't blame another CPU. */ + ts_delta = ts0 - ts2; + pr_alert("sched_clock on CPU %d went backward by %llu ns\n", raw_smp_processor_id(), ts_delta); + *ts1 = ts2; + return false; + } + + firsttime = !*bug_id; + if (firsttime) + *bug_id = atomic_inc_return(&csd_bug_count); + cpu = csd_lock_wait_getcpu(csd); + if (WARN_ONCE(cpu < 0 || cpu >= nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu)) + cpux = 0; + else + cpux = cpu; + cpu_cur_csd = smp_load_acquire(&per_cpu(cur_csd, cpux)); /* Before func and info. */ + /* How long since this CSD lock was stuck. */ + ts_delta = ts2 - ts0; + pr_alert("csd: %s non-responsive CSD lock (#%d) on CPU#%d, waiting %lld ns for CPU#%02d %pS(%ps).\n", + firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), (s64)ts_delta, + cpu, csd->func, csd->info); + (*nmessages)++; + if (firsttime) + atomic_inc(&n_csd_lock_stuck); + /* + * If the CSD lock is still stuck after 5 minutes, it is unlikely + * to become unstuck. Use a signed comparison to avoid triggering + * on underflows when the TSC is out of sync between sockets. + */ + BUG_ON(panic_on_ipistall > 0 && (s64)ts_delta > ((s64)panic_on_ipistall * NSEC_PER_MSEC)); + if (cpu_cur_csd && csd != cpu_cur_csd) { + pr_alert("\tcsd: CSD lock (#%d) handling prior %pS(%ps) request.\n", + *bug_id, READ_ONCE(per_cpu(cur_csd_func, cpux)), + READ_ONCE(per_cpu(cur_csd_info, cpux))); + } else { + pr_alert("\tcsd: CSD lock (#%d) %s.\n", + *bug_id, !cpu_cur_csd ? "unresponsive" : "handling this request"); + } + if (cpu >= 0) { + if (atomic_cmpxchg_acquire(&per_cpu(trigger_backtrace, cpu), 1, 0)) + dump_cpu_task(cpu); + if (!cpu_cur_csd) { + pr_alert("csd: Re-sending CSD lock (#%d) IPI from CPU#%02d to CPU#%02d\n", *bug_id, raw_smp_processor_id(), cpu); + arch_send_call_function_single_ipi(cpu); + } + } + if (firsttime) + dump_stack(); + *ts1 = ts2; + + return false; } /* @@ -100,58 +317,91 @@ void __init call_function_init(void) * previous function call. For multi-cpu calls its even more interesting * as we'll have to ensure no other cpu is observing our csd. */ -static void csd_lock_wait(struct call_single_data *csd) +static void __csd_lock_wait(call_single_data_t *csd) { - while (csd->flags & CSD_FLAG_LOCK) + unsigned long nmessages = 0; + int bug_id = 0; + u64 ts0, ts1; + + ts1 = ts0 = ktime_get_mono_fast_ns(); + for (;;) { + if (csd_lock_wait_toolong(csd, ts0, &ts1, &bug_id, &nmessages)) + break; cpu_relax(); + } + smp_acquire__after_ctrl_dep(); +} + +static __always_inline void csd_lock_wait(call_single_data_t *csd) +{ + if (static_branch_unlikely(&csdlock_debug_enabled)) { + __csd_lock_wait(csd); + return; + } + + smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK)); +} +#else +static void csd_lock_record(call_single_data_t *csd) +{ +} + +static __always_inline void csd_lock_wait(call_single_data_t *csd) +{ + smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK)); } +#endif -static void csd_lock(struct call_single_data *csd) +static __always_inline void csd_lock(call_single_data_t *csd) { csd_lock_wait(csd); - csd->flags |= CSD_FLAG_LOCK; + csd->node.u_flags |= CSD_FLAG_LOCK; /* * prevent CPU from reordering the above assignment * to ->flags with any subsequent assignments to other - * fields of the specified call_single_data structure: + * fields of the specified call_single_data_t structure: */ - smp_mb(); + smp_wmb(); } -static void csd_unlock(struct call_single_data *csd) +static __always_inline void csd_unlock(call_single_data_t *csd) { - WARN_ON(!(csd->flags & CSD_FLAG_LOCK)); + WARN_ON(!(csd->node.u_flags & CSD_FLAG_LOCK)); /* * ensure we're all done before releasing data: */ - smp_mb(); - - csd->flags &= ~CSD_FLAG_LOCK; + smp_store_release(&csd->node.u_flags, 0); } -/* - * Insert a previously allocated call_single_data element - * for execution on the given CPU. data must already have - * ->func, ->info, and ->flags set. - */ -static -void generic_exec_single(int cpu, struct call_single_data *csd, int wait) +static DEFINE_PER_CPU_SHARED_ALIGNED(call_single_data_t, csd_data); + +void __smp_call_single_queue(int cpu, struct llist_node *node) { - struct call_single_queue *dst = &per_cpu(call_single_queue, cpu); - unsigned long flags; - int ipi; + /* + * We have to check the type of the CSD before queueing it, because + * once queued it can have its flags cleared by + * flush_smp_call_function_queue() + * even if we haven't sent the smp_call IPI yet (e.g. the stopper + * executes migration_cpu_stop() on the remote CPU). + */ + if (trace_csd_queue_cpu_enabled()) { + call_single_data_t *csd; + smp_call_func_t func; + + csd = container_of(node, call_single_data_t, node.llist); + func = CSD_TYPE(csd) == CSD_TYPE_TTWU ? + sched_ttwu_pending : csd->func; - raw_spin_lock_irqsave(&dst->lock, flags); - ipi = list_empty(&dst->list); - list_add_tail(&csd->list, &dst->list); - raw_spin_unlock_irqrestore(&dst->lock, flags); + trace_csd_queue_cpu(cpu, _RET_IP_, func, csd); + } /* - * The list addition should be visible before sending the IPI - * handler locks the list to pull the entry off it because of - * normal cache coherency rules implied by spinlocks. + * The list addition should be visible to the target CPU when it pops + * the head of the list to pull the entry off it in the IPI handler + * because of normal cache coherency rules implied by the underlying + * llist ops. * * If IPIs can go out of order to the cache coherency protocol * in an architecture, sufficient synchronisation should be added @@ -159,56 +409,221 @@ void generic_exec_single(int cpu, struct call_single_data *csd, int wait) * locking and barrier primitives. Generic code isn't really * equipped to do the right thing... */ - if (ipi) - arch_send_call_function_single_ipi(cpu); - - if (wait) - csd_lock_wait(csd); + if (llist_add(node, &per_cpu(call_single_queue, cpu))) + send_call_function_single_ipi(cpu); } /* - * Invoked by arch to handle an IPI for call function single. Must be - * called from the arch with interrupts disabled. + * Insert a previously allocated call_single_data_t element + * for execution on the given CPU. data must already have + * ->func, ->info, and ->flags set. */ -void generic_smp_call_function_single_interrupt(void) +static int generic_exec_single(int cpu, call_single_data_t *csd) { - struct call_single_queue *q = &__get_cpu_var(call_single_queue); - LIST_HEAD(list); - /* - * Shouldn't receive this interrupt on a cpu that is not yet online. + * Preemption already disabled here so stopper cannot run on this CPU, + * ensuring mutually exclusive CPU offlining and last IPI flush. */ - WARN_ON_ONCE(!cpu_online(smp_processor_id())); + if (cpu == smp_processor_id()) { + smp_call_func_t func = csd->func; + void *info = csd->info; + unsigned long flags; - raw_spin_lock(&q->lock); - list_replace_init(&q->list, &list); - raw_spin_unlock(&q->lock); + /* + * We can unlock early even for the synchronous on-stack case, + * since we're doing this from the same CPU.. + */ + csd_lock_record(csd); + csd_unlock(csd); + local_irq_save(flags); + csd_do_func(func, info, NULL); + csd_lock_record(NULL); + local_irq_restore(flags); + return 0; + } - while (!list_empty(&list)) { - struct call_single_data *csd; - unsigned int csd_flags; + if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu)) { + csd_unlock(csd); + return -ENXIO; + } - csd = list_entry(list.next, struct call_single_data, list); - list_del(&csd->list); + __smp_call_single_queue(cpu, &csd->node.llist); - /* - * 'csd' can be invalid after this call if flags == 0 - * (when called through generic_exec_single()), - * so save them away before making the call: - */ - csd_flags = csd->flags; + return 0; +} - csd->func(csd->info); +/** + * generic_smp_call_function_single_interrupt - Execute SMP IPI callbacks + * + * Invoked by arch to handle an IPI for call function single. + * Must be called with interrupts disabled. + */ +void generic_smp_call_function_single_interrupt(void) +{ + __flush_smp_call_function_queue(true); +} + +/** + * __flush_smp_call_function_queue - Flush pending smp-call-function callbacks + * + * @warn_cpu_offline: If set to 'true', warn if callbacks were queued on an + * offline CPU. Skip this check if set to 'false'. + * + * Flush any pending smp-call-function callbacks queued on this CPU. This is + * invoked by the generic IPI handler, as well as by a CPU about to go offline, + * to ensure that all pending IPI callbacks are run before it goes completely + * offline. + * + * Loop through the call_single_queue and run all the queued callbacks. + * Must be called with interrupts disabled. + */ +static void __flush_smp_call_function_queue(bool warn_cpu_offline) +{ + call_single_data_t *csd, *csd_next; + struct llist_node *entry, *prev; + struct llist_head *head; + static bool warned; + atomic_t *tbt; + + lockdep_assert_irqs_disabled(); + + /* Allow waiters to send backtrace NMI from here onwards */ + tbt = this_cpu_ptr(&trigger_backtrace); + atomic_set_release(tbt, 1); + + head = this_cpu_ptr(&call_single_queue); + entry = llist_del_all(head); + entry = llist_reverse_order(entry); + + /* There shouldn't be any pending callbacks on an offline CPU. */ + if (unlikely(warn_cpu_offline && !cpu_online(smp_processor_id()) && + !warned && entry != NULL)) { + warned = true; + WARN(1, "IPI on offline CPU %d\n", smp_processor_id()); /* - * Unlocked CSDs are valid through generic_exec_single(): + * We don't have to use the _safe() variant here + * because we are not invoking the IPI handlers yet. */ - if (csd_flags & CSD_FLAG_LOCK) + llist_for_each_entry(csd, entry, node.llist) { + switch (CSD_TYPE(csd)) { + case CSD_TYPE_ASYNC: + case CSD_TYPE_SYNC: + case CSD_TYPE_IRQ_WORK: + pr_warn("IPI callback %pS sent to offline CPU\n", + csd->func); + break; + + case CSD_TYPE_TTWU: + pr_warn("IPI task-wakeup sent to offline CPU\n"); + break; + + default: + pr_warn("IPI callback, unknown type %d, sent to offline CPU\n", + CSD_TYPE(csd)); + break; + } + } + } + + /* + * First; run all SYNC callbacks, people are waiting for us. + */ + prev = NULL; + llist_for_each_entry_safe(csd, csd_next, entry, node.llist) { + /* Do we wait until *after* callback? */ + if (CSD_TYPE(csd) == CSD_TYPE_SYNC) { + smp_call_func_t func = csd->func; + void *info = csd->info; + + if (prev) { + prev->next = &csd_next->node.llist; + } else { + entry = &csd_next->node.llist; + } + + csd_lock_record(csd); + csd_do_func(func, info, csd); csd_unlock(csd); + csd_lock_record(NULL); + } else { + prev = &csd->node.llist; + } + } + + if (!entry) + return; + + /* + * Second; run all !SYNC callbacks. + */ + prev = NULL; + llist_for_each_entry_safe(csd, csd_next, entry, node.llist) { + int type = CSD_TYPE(csd); + + if (type != CSD_TYPE_TTWU) { + if (prev) { + prev->next = &csd_next->node.llist; + } else { + entry = &csd_next->node.llist; + } + + if (type == CSD_TYPE_ASYNC) { + smp_call_func_t func = csd->func; + void *info = csd->info; + + csd_lock_record(csd); + csd_unlock(csd); + csd_do_func(func, info, csd); + csd_lock_record(NULL); + } else if (type == CSD_TYPE_IRQ_WORK) { + irq_work_single(csd); + } + + } else { + prev = &csd->node.llist; + } + } + + /* + * Third; only CSD_TYPE_TTWU is left, issue those. + */ + if (entry) { + csd = llist_entry(entry, typeof(*csd), node.llist); + csd_do_func(sched_ttwu_pending, entry, csd); } } -static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data); + +/** + * flush_smp_call_function_queue - Flush pending smp-call-function callbacks + * from task context (idle, migration thread) + * + * When TIF_POLLING_NRFLAG is supported and a CPU is in idle and has it + * set, then remote CPUs can avoid sending IPIs and wake the idle CPU by + * setting TIF_NEED_RESCHED. The idle task on the woken up CPU has to + * handle queued SMP function calls before scheduling. + * + * The migration thread has to ensure that an eventually pending wakeup has + * been handled before it migrates a task. + */ +void flush_smp_call_function_queue(void) +{ + unsigned int was_pending; + unsigned long flags; + + if (llist_empty(this_cpu_ptr(&call_single_queue))) + return; + + local_irq_save(flags); + /* Get the already pending soft interrupts for RT enabled kernels */ + was_pending = local_softirq_pending(); + __flush_smp_call_function_queue(true); + if (local_softirq_pending()) + do_softirq_post_smp_call_flush(was_pending); + + local_irq_restore(flags); +} /* * smp_call_function_single - Run a function on a specific CPU @@ -221,16 +636,18 @@ static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data); int smp_call_function_single(int cpu, smp_call_func_t func, void *info, int wait) { - struct call_single_data d = { - .flags = 0, + call_single_data_t *csd; + call_single_data_t csd_stack = { + .node = { .u_flags = CSD_FLAG_LOCK | CSD_TYPE_SYNC, }, }; - unsigned long flags; int this_cpu; - int err = 0; + int err; /* - * prevent preemption and reschedule on another processor, - * as well as CPU removal + * Prevent preemption and reschedule on another CPU, as well as CPU + * removal. This prevents stopper from running on this CPU, thus + * providing mutual exclusion of the below cpu_online() check and + * IPI sending ensuring IPI are not missed by CPU going offline. */ this_cpu = get_cpu(); @@ -243,26 +660,31 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info, WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() && !oops_in_progress); - if (cpu == this_cpu) { - local_irq_save(flags); - func(info); - local_irq_restore(flags); - } else { - if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) { - struct call_single_data *csd = &d; + /* + * When @wait we can deadlock when we interrupt between llist_add() and + * arch_send_call_function_ipi*(); when !@wait we can deadlock due to + * csd_lock() on because the interrupt context uses the same csd + * storage. + */ + WARN_ON_ONCE(!in_task()); - if (!wait) - csd = &__get_cpu_var(csd_data); + csd = &csd_stack; + if (!wait) { + csd = this_cpu_ptr(&csd_data); + csd_lock(csd); + } - csd_lock(csd); + csd->func = func; + csd->info = info; +#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG + csd->node.src = smp_processor_id(); + csd->node.dst = cpu; +#endif - csd->func = func; - csd->info = info; - generic_exec_single(cpu, csd, wait); - } else { - err = -ENXIO; /* CPU not online */ - } - } + err = generic_exec_single(cpu, csd); + + if (wait) + csd_lock_wait(csd); put_cpu(); @@ -270,6 +692,52 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info, } EXPORT_SYMBOL(smp_call_function_single); +/** + * smp_call_function_single_async() - Run an asynchronous function on a + * specific CPU. + * @cpu: The CPU to run on. + * @csd: Pre-allocated and setup data structure + * + * Like smp_call_function_single(), but the call is asynchonous and + * can thus be done from contexts with disabled interrupts. + * + * The caller passes his own pre-allocated data structure + * (ie: embedded in an object) and is responsible for synchronizing it + * such that the IPIs performed on the @csd are strictly serialized. + * + * If the function is called with one csd which has not yet been + * processed by previous call to smp_call_function_single_async(), the + * function will return immediately with -EBUSY showing that the csd + * object is still in progress. + * + * NOTE: Be careful, there is unfortunately no current debugging facility to + * validate the correctness of this serialization. + * + * Return: %0 on success or negative errno value on error + */ +int smp_call_function_single_async(int cpu, call_single_data_t *csd) +{ + int err = 0; + + preempt_disable(); + + if (csd->node.u_flags & CSD_FLAG_LOCK) { + err = -EBUSY; + goto out; + } + + csd->node.u_flags = CSD_FLAG_LOCK; + smp_wmb(); + + err = generic_exec_single(cpu, csd); + +out: + preempt_enable(); + + return err; +} +EXPORT_SYMBOL_GPL(smp_call_function_single_async); + /* * smp_call_function_any - Run a function on any of the given cpus * @mask: The mask of cpus it can run on. @@ -278,99 +746,49 @@ EXPORT_SYMBOL(smp_call_function_single); * @wait: If true, wait until function has completed. * * Returns 0 on success, else a negative status code (if no cpus were online). - * Note that @wait will be implicitly turned on in case of allocation failures, - * since we fall back to on-stack allocation. * * Selection preference: * 1) current cpu if in @mask - * 2) any cpu of current node if in @mask - * 3) any other online cpu in @mask + * 2) nearest cpu in @mask, based on NUMA topology */ int smp_call_function_any(const struct cpumask *mask, smp_call_func_t func, void *info, int wait) { unsigned int cpu; - const struct cpumask *nodemask; int ret; /* Try for same CPU (cheapest) */ cpu = get_cpu(); - if (cpumask_test_cpu(cpu, mask)) - goto call; - - /* Try for same node. */ - nodemask = cpumask_of_node(cpu_to_node(cpu)); - for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids; - cpu = cpumask_next_and(cpu, nodemask, mask)) { - if (cpu_online(cpu)) - goto call; - } + if (!cpumask_test_cpu(cpu, mask)) + cpu = sched_numa_find_nth_cpu(mask, 0, cpu_to_node(cpu)); - /* Any online will do: smp_call_function_single handles nr_cpu_ids. */ - cpu = cpumask_any_and(mask, cpu_online_mask); -call: ret = smp_call_function_single(cpu, func, info, wait); put_cpu(); return ret; } EXPORT_SYMBOL_GPL(smp_call_function_any); -/** - * __smp_call_function_single(): Run a function on a specific CPU - * @cpu: The CPU to run on. - * @data: Pre-allocated and setup data structure - * @wait: If true, wait until function has completed on specified CPU. +/* + * Flags to be used as scf_flags argument of smp_call_function_many_cond(). * - * Like smp_call_function_single(), but allow caller to pass in a - * pre-allocated data structure. Useful for embedding @data inside - * other structures, for instance. + * %SCF_WAIT: Wait until function execution is completed + * %SCF_RUN_LOCAL: Run also locally if local cpu is set in cpumask */ -void __smp_call_function_single(int cpu, struct call_single_data *csd, - int wait) -{ - unsigned int this_cpu; - unsigned long flags; +#define SCF_WAIT (1U << 0) +#define SCF_RUN_LOCAL (1U << 1) - this_cpu = get_cpu(); - /* - * Can deadlock when called with interrupts disabled. - * We allow cpu's that are not yet online though, as no one else can - * send smp call function interrupt to this cpu and as such deadlocks - * can't happen. - */ - WARN_ON_ONCE(cpu_online(smp_processor_id()) && wait && irqs_disabled() - && !oops_in_progress); - - if (cpu == this_cpu) { - local_irq_save(flags); - csd->func(csd->info); - local_irq_restore(flags); - } else { - csd_lock(csd); - generic_exec_single(cpu, csd, wait); - } - put_cpu(); -} - -/** - * smp_call_function_many(): Run a function on a set of other CPUs. - * @mask: The set of cpus to run on (only runs on online subset). - * @func: The function to run. This must be fast and non-blocking. - * @info: An arbitrary pointer to pass to the function. - * @wait: If true, wait (atomically) until function has completed - * on other CPUs. - * - * If @wait is true, then returns once @func has returned. - * - * You must not call this function with disabled interrupts or from a - * hardware interrupt handler or from a bottom half handler. Preemption - * must be disabled when calling this function. - */ -void smp_call_function_many(const struct cpumask *mask, - smp_call_func_t func, void *info, bool wait) +static void smp_call_function_many_cond(const struct cpumask *mask, + smp_call_func_t func, void *info, + unsigned int scf_flags, + smp_cond_func_t cond_func) { + int cpu, last_cpu, this_cpu = smp_processor_id(); struct call_function_data *cfd; - int cpu, next_cpu, this_cpu = smp_processor_id(); + bool wait = scf_flags & SCF_WAIT; + int nr_cpus = 0; + bool run_remote = false; + + lockdep_assert_preemption_disabled(); /* * Can deadlock when called with interrupts disabled. @@ -378,72 +796,109 @@ void smp_call_function_many(const struct cpumask *mask, * send smp call function interrupt to this cpu and as such deadlocks * can't happen. */ - WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() - && !oops_in_progress && !early_boot_irqs_disabled); + if (cpu_online(this_cpu) && !oops_in_progress && + !early_boot_irqs_disabled) + lockdep_assert_irqs_enabled(); - /* Try to fastpath. So, what's a CPU they want? Ignoring this one. */ - cpu = cpumask_first_and(mask, cpu_online_mask); - if (cpu == this_cpu) - cpu = cpumask_next_and(cpu, mask, cpu_online_mask); - - /* No online cpus? We're done. */ - if (cpu >= nr_cpu_ids) - return; + /* + * When @wait we can deadlock when we interrupt between llist_add() and + * arch_send_call_function_ipi*(); when !@wait we can deadlock due to + * csd_lock() on because the interrupt context uses the same csd + * storage. + */ + WARN_ON_ONCE(!in_task()); - /* Do we have another CPU which isn't us? */ - next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask); - if (next_cpu == this_cpu) - next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask); + /* Check if we need remote execution, i.e., any CPU excluding this one. */ + if (cpumask_any_and_but(mask, cpu_online_mask, this_cpu) < nr_cpu_ids) { + cfd = this_cpu_ptr(&cfd_data); + cpumask_and(cfd->cpumask, mask, cpu_online_mask); + __cpumask_clear_cpu(this_cpu, cfd->cpumask); - /* Fastpath: do that cpu by itself. */ - if (next_cpu >= nr_cpu_ids) { - smp_call_function_single(cpu, func, info, wait); - return; - } + cpumask_clear(cfd->cpumask_ipi); + for_each_cpu(cpu, cfd->cpumask) { + call_single_data_t *csd = per_cpu_ptr(cfd->csd, cpu); - cfd = &__get_cpu_var(cfd_data); + if (cond_func && !cond_func(cpu, info)) { + __cpumask_clear_cpu(cpu, cfd->cpumask); + continue; + } - cpumask_and(cfd->cpumask, mask, cpu_online_mask); - cpumask_clear_cpu(this_cpu, cfd->cpumask); + /* Work is enqueued on a remote CPU. */ + run_remote = true; - /* Some callers race with other cpus changing the passed mask */ - if (unlikely(!cpumask_weight(cfd->cpumask))) - return; + csd_lock(csd); + if (wait) + csd->node.u_flags |= CSD_TYPE_SYNC; + csd->func = func; + csd->info = info; +#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG + csd->node.src = smp_processor_id(); + csd->node.dst = cpu; +#endif + trace_csd_queue_cpu(cpu, _RET_IP_, func, csd); + + /* + * Kick the remote CPU if this is the first work + * item enqueued. + */ + if (llist_add(&csd->node.llist, &per_cpu(call_single_queue, cpu))) { + __cpumask_set_cpu(cpu, cfd->cpumask_ipi); + nr_cpus++; + last_cpu = cpu; + } + } - /* - * After we put an entry into the list, cfd->cpumask may be cleared - * again when another CPU sends another IPI for a SMP function call, so - * cfd->cpumask will be zero. - */ - cpumask_copy(cfd->cpumask_ipi, cfd->cpumask); + /* + * Choose the most efficient way to send an IPI. Note that the + * number of CPUs might be zero due to concurrent changes to the + * provided mask. + */ + if (nr_cpus == 1) + send_call_function_single_ipi(last_cpu); + else if (likely(nr_cpus > 1)) + send_call_function_ipi_mask(cfd->cpumask_ipi); + } - for_each_cpu(cpu, cfd->cpumask) { - struct call_single_data *csd = per_cpu_ptr(cfd->csd, cpu); - struct call_single_queue *dst = - &per_cpu(call_single_queue, cpu); + /* Check if we need local execution. */ + if ((scf_flags & SCF_RUN_LOCAL) && cpumask_test_cpu(this_cpu, mask) && + (!cond_func || cond_func(this_cpu, info))) { unsigned long flags; - csd_lock(csd); - csd->func = func; - csd->info = info; - - raw_spin_lock_irqsave(&dst->lock, flags); - list_add_tail(&csd->list, &dst->list); - raw_spin_unlock_irqrestore(&dst->lock, flags); + local_irq_save(flags); + csd_do_func(func, info, NULL); + local_irq_restore(flags); } - /* Send a message to all CPUs in the map */ - arch_send_call_function_ipi_mask(cfd->cpumask_ipi); - - if (wait) { + if (run_remote && wait) { for_each_cpu(cpu, cfd->cpumask) { - struct call_single_data *csd; + call_single_data_t *csd; csd = per_cpu_ptr(cfd->csd, cpu); csd_lock_wait(csd); } } } + +/** + * smp_call_function_many(): Run a function on a set of CPUs. + * @mask: The set of cpus to run on (only runs on online subset). + * @func: The function to run. This must be fast and non-blocking. + * @info: An arbitrary pointer to pass to the function. + * @wait: If true, wait (atomically) until function has completed + * on other CPUs. + * + * You must not call this function with disabled interrupts or from a + * hardware interrupt handler or from a bottom half handler. Preemption + * must be disabled when calling this function. + * + * @func is not called on the local CPU even if @mask contains it. Consider + * using on_each_cpu_cond_mask() instead if this is not desirable. + */ +void smp_call_function_many(const struct cpumask *mask, + smp_call_func_t func, void *info, bool wait) +{ + smp_call_function_many_cond(mask, func, info, wait * SCF_WAIT, NULL); +} EXPORT_SYMBOL(smp_call_function_many); /** @@ -461,16 +916,13 @@ EXPORT_SYMBOL(smp_call_function_many); * You must not call this function with disabled interrupts or from a * hardware interrupt handler or from a bottom half handler. */ -int smp_call_function(smp_call_func_t func, void *info, int wait) +void smp_call_function(smp_call_func_t func, void *info, int wait) { preempt_disable(); smp_call_function_many(cpu_online_mask, func, info, wait); preempt_enable(); - - return 0; } EXPORT_SYMBOL(smp_call_function); -#endif /* USE_GENERIC_SMP_HELPERS */ /* Setup configured maximum number of CPUs to activate */ unsigned int setup_max_cpus = NR_CPUS; @@ -488,7 +940,7 @@ EXPORT_SYMBOL(setup_max_cpus); * SMP mode to <NUM>. */ -void __weak arch_disable_smp_support(void) { } +void __weak __init arch_disable_smp_support(void) { } static int __init nosmp(char *str) { @@ -505,9 +957,8 @@ static int __init nrcpus(char *str) { int nr_cpus; - get_option(&str, &nr_cpus); - if (nr_cpus > 0 && nr_cpus < nr_cpu_ids) - nr_cpu_ids = nr_cpus; + if (get_option(&str, &nr_cpus) && nr_cpus > 0 && nr_cpus < nr_cpu_ids) + set_nr_cpu_ids(nr_cpus); return 0; } @@ -525,84 +976,38 @@ static int __init maxcpus(char *str) early_param("maxcpus", maxcpus); +#if (NR_CPUS > 1) && !defined(CONFIG_FORCE_NR_CPUS) /* Setup number of possible processor ids */ -int nr_cpu_ids __read_mostly = NR_CPUS; +unsigned int nr_cpu_ids __read_mostly = NR_CPUS; EXPORT_SYMBOL(nr_cpu_ids); +#endif /* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */ void __init setup_nr_cpu_ids(void) { - nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1; + set_nr_cpu_ids(find_last_bit(cpumask_bits(cpu_possible_mask), NR_CPUS) + 1); } /* Called by boot processor to activate the rest. */ void __init smp_init(void) { - unsigned int cpu; + int num_nodes, num_cpus; idle_threads_init(); + cpuhp_threads_init(); - /* FIXME: This should be done in userspace --RR */ - for_each_present_cpu(cpu) { - if (num_online_cpus() >= setup_max_cpus) - break; - if (!cpu_online(cpu)) - cpu_up(cpu); - } - - /* Any cleanup work */ - printk(KERN_INFO "Brought up %ld CPUs\n", (long)num_online_cpus()); - smp_cpus_done(setup_max_cpus); -} - -/* - * Call a function on all processors. May be used during early boot while - * early_boot_irqs_disabled is set. Use local_irq_save/restore() instead - * of local_irq_disable/enable(). - */ -int on_each_cpu(void (*func) (void *info), void *info, int wait) -{ - unsigned long flags; - int ret = 0; + pr_info("Bringing up secondary CPUs ...\n"); - preempt_disable(); - ret = smp_call_function(func, info, wait); - local_irq_save(flags); - func(info); - local_irq_restore(flags); - preempt_enable(); - return ret; -} -EXPORT_SYMBOL(on_each_cpu); + bringup_nonboot_cpus(setup_max_cpus); -/** - * on_each_cpu_mask(): Run a function on processors specified by - * cpumask, which may include the local processor. - * @mask: The set of cpus to run on (only runs on online subset). - * @func: The function to run. This must be fast and non-blocking. - * @info: An arbitrary pointer to pass to the function. - * @wait: If true, wait (atomically) until function has completed - * on other CPUs. - * - * If @wait is true, then returns once @func has returned. - * - * You must not call this function with disabled interrupts or - * from a hardware interrupt handler or from a bottom half handler. - */ -void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func, - void *info, bool wait) -{ - int cpu = get_cpu(); + num_nodes = num_online_nodes(); + num_cpus = num_online_cpus(); + pr_info("Brought up %d node%s, %d CPU%s\n", + num_nodes, str_plural(num_nodes), num_cpus, str_plural(num_cpus)); - smp_call_function_many(mask, func, info, wait); - if (cpumask_test_cpu(cpu, mask)) { - local_irq_disable(); - func(info); - local_irq_enable(); - } - put_cpu(); + /* Any cleanup work */ + smp_cpus_done(setup_max_cpus); } -EXPORT_SYMBOL(on_each_cpu_mask); /* * on_each_cpu_cond(): Call a function on each processor for which @@ -610,20 +1015,15 @@ EXPORT_SYMBOL(on_each_cpu_mask); * for all the required CPUs to finish. This may include the local * processor. * @cond_func: A callback function that is passed a cpu id and - * the the info parameter. The function is called + * the info parameter. The function is called * with preemption disabled. The function should - * return a blooean value indicating whether to IPI + * return a boolean value indicating whether to IPI * the specified CPU. * @func: The function to run on all applicable CPUs. * This must be fast and non-blocking. * @info: An arbitrary pointer to pass to both functions. * @wait: If true, wait (atomically) until function has * completed on other CPUs. - * @gfp_flags: GFP flags to use when allocating the cpumask - * used internally by the function. - * - * The function might sleep if the GFP flags indicates a non - * atomic allocation is allowed. * * Preemption is disabled to protect against CPUs going offline but not online. * CPUs going online during the call will not be seen or sent an IPI. @@ -631,39 +1031,19 @@ EXPORT_SYMBOL(on_each_cpu_mask); * You must not call this function with disabled interrupts or * from a hardware interrupt handler or from a bottom half handler. */ -void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info), - smp_call_func_t func, void *info, bool wait, - gfp_t gfp_flags) +void on_each_cpu_cond_mask(smp_cond_func_t cond_func, smp_call_func_t func, + void *info, bool wait, const struct cpumask *mask) { - cpumask_var_t cpus; - int cpu, ret; + unsigned int scf_flags = SCF_RUN_LOCAL; - might_sleep_if(gfp_flags & __GFP_WAIT); + if (wait) + scf_flags |= SCF_WAIT; - if (likely(zalloc_cpumask_var(&cpus, (gfp_flags|__GFP_NOWARN)))) { - preempt_disable(); - for_each_online_cpu(cpu) - if (cond_func(cpu, info)) - cpumask_set_cpu(cpu, cpus); - on_each_cpu_mask(cpus, func, info, wait); - preempt_enable(); - free_cpumask_var(cpus); - } else { - /* - * No free cpumask, bother. No matter, we'll - * just have to IPI them one by one. - */ - preempt_disable(); - for_each_online_cpu(cpu) - if (cond_func(cpu, info)) { - ret = smp_call_function_single(cpu, func, - info, wait); - WARN_ON_ONCE(!ret); - } - preempt_enable(); - } + preempt_disable(); + smp_call_function_many_cond(mask, func, info, scf_flags, cond_func); + preempt_enable(); } -EXPORT_SYMBOL(on_each_cpu_cond); +EXPORT_SYMBOL(on_each_cpu_cond_mask); static void do_nothing(void *unused) { @@ -687,3 +1067,102 @@ void kick_all_cpus_sync(void) smp_call_function(do_nothing, NULL, 1); } EXPORT_SYMBOL_GPL(kick_all_cpus_sync); + +/** + * wake_up_all_idle_cpus - break all cpus out of idle + * wake_up_all_idle_cpus try to break all cpus which is in idle state even + * including idle polling cpus, for non-idle cpus, we will do nothing + * for them. + */ +void wake_up_all_idle_cpus(void) +{ + int cpu; + + for_each_possible_cpu(cpu) { + preempt_disable(); + if (cpu != smp_processor_id() && cpu_online(cpu)) + wake_up_if_idle(cpu); + preempt_enable(); + } +} +EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus); + +/** + * cpus_peek_for_pending_ipi - Check for pending IPI for CPUs + * @mask: The CPU mask for the CPUs to check. + * + * This function walks through the @mask to check if there are any pending IPIs + * scheduled, for any of the CPUs in the @mask. It does not guarantee + * correctness as it only provides a racy snapshot. + * + * Returns true if there is a pending IPI scheduled and false otherwise. + */ +bool cpus_peek_for_pending_ipi(const struct cpumask *mask) +{ + unsigned int cpu; + + for_each_cpu(cpu, mask) { + if (!llist_empty(per_cpu_ptr(&call_single_queue, cpu))) + return true; + } + + return false; +} + +/** + * struct smp_call_on_cpu_struct - Call a function on a specific CPU + * @work: &work_struct + * @done: &completion to signal + * @func: function to call + * @data: function's data argument + * @ret: return value from @func + * @cpu: target CPU (%-1 for any CPU) + * + * Used to call a function on a specific cpu and wait for it to return. + * Optionally make sure the call is done on a specified physical cpu via vcpu + * pinning in order to support virtualized environments. + */ +struct smp_call_on_cpu_struct { + struct work_struct work; + struct completion done; + int (*func)(void *); + void *data; + int ret; + int cpu; +}; + +static void smp_call_on_cpu_callback(struct work_struct *work) +{ + struct smp_call_on_cpu_struct *sscs; + + sscs = container_of(work, struct smp_call_on_cpu_struct, work); + if (sscs->cpu >= 0) + hypervisor_pin_vcpu(sscs->cpu); + sscs->ret = sscs->func(sscs->data); + if (sscs->cpu >= 0) + hypervisor_pin_vcpu(-1); + + complete(&sscs->done); +} + +int smp_call_on_cpu(unsigned int cpu, int (*func)(void *), void *par, bool phys) +{ + struct smp_call_on_cpu_struct sscs = { + .done = COMPLETION_INITIALIZER_ONSTACK(sscs.done), + .func = func, + .data = par, + .cpu = phys ? cpu : -1, + }; + + INIT_WORK_ONSTACK(&sscs.work, smp_call_on_cpu_callback); + + if (cpu >= nr_cpu_ids || !cpu_online(cpu)) + return -ENXIO; + + queue_work_on(cpu, system_wq, &sscs.work); + wait_for_completion(&sscs.done); + destroy_work_on_stack(&sscs.work); + + return sscs.ret; +} +EXPORT_SYMBOL_GPL(smp_call_on_cpu); |