diff options
| -rw-r--r-- | include/linux/cpuset.h | 3 | ||||
| -rw-r--r-- | kernel/cgroup/cpuset.c | 141 | ||||
| -rw-r--r-- | kernel/cpu.c | 48 | ||||
| -rw-r--r-- | kernel/power/process.c | 2 |
4 files changed, 56 insertions, 138 deletions
diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h index 0ce6ff0d9c9a..de4cf0ee96f7 100644 --- a/include/linux/cpuset.h +++ b/include/linux/cpuset.h @@ -70,7 +70,6 @@ extern int cpuset_init(void); extern void cpuset_init_smp(void); extern void cpuset_force_rebuild(void); extern void cpuset_update_active_cpus(void); -extern void cpuset_wait_for_hotplug(void); extern void inc_dl_tasks_cs(struct task_struct *task); extern void dec_dl_tasks_cs(struct task_struct *task); extern void cpuset_lock(void); @@ -185,8 +184,6 @@ static inline void cpuset_update_active_cpus(void) partition_sched_domains(1, NULL, NULL); } -static inline void cpuset_wait_for_hotplug(void) { } - static inline void inc_dl_tasks_cs(struct task_struct *task) { } static inline void dec_dl_tasks_cs(struct task_struct *task) { } static inline void cpuset_lock(void) { } diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 4237c8748715..d8d3439eda4e 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -202,6 +202,14 @@ struct cpuset { }; /* + * Legacy hierarchy call to cgroup_transfer_tasks() is handled asynchrously + */ +struct cpuset_remove_tasks_struct { + struct work_struct work; + struct cpuset *cs; +}; + +/* * Exclusive CPUs distributed out to sub-partitions of top_cpuset */ static cpumask_var_t subpartitions_cpus; @@ -449,12 +457,6 @@ static DEFINE_SPINLOCK(callback_lock); static struct workqueue_struct *cpuset_migrate_mm_wq; -/* - * CPU / memory hotplug is handled asynchronously. - */ -static void cpuset_hotplug_workfn(struct work_struct *work); -static DECLARE_WORK(cpuset_hotplug_work, cpuset_hotplug_workfn); - static DECLARE_WAIT_QUEUE_HEAD(cpuset_attach_wq); static inline void check_insane_mems_config(nodemask_t *nodes) @@ -540,22 +542,10 @@ static void guarantee_online_cpus(struct task_struct *tsk, rcu_read_lock(); cs = task_cs(tsk); - while (!cpumask_intersects(cs->effective_cpus, pmask)) { + while (!cpumask_intersects(cs->effective_cpus, pmask)) cs = parent_cs(cs); - if (unlikely(!cs)) { - /* - * The top cpuset doesn't have any online cpu as a - * consequence of a race between cpuset_hotplug_work - * and cpu hotplug notifier. But we know the top - * cpuset's effective_cpus is on its way to be - * identical to cpu_online_mask. - */ - goto out_unlock; - } - } - cpumask_and(pmask, pmask, cs->effective_cpus); -out_unlock: + cpumask_and(pmask, pmask, cs->effective_cpus); rcu_read_unlock(); } @@ -1217,7 +1207,7 @@ static void rebuild_sched_domains_locked(void) /* * If we have raced with CPU hotplug, return early to avoid * passing doms with offlined cpu to partition_sched_domains(). - * Anyways, cpuset_hotplug_workfn() will rebuild sched domains. + * Anyways, cpuset_handle_hotplug() will rebuild sched domains. * * With no CPUs in any subpartitions, top_cpuset's effective CPUs * should be the same as the active CPUs, so checking only top_cpuset @@ -1260,12 +1250,17 @@ static void rebuild_sched_domains_locked(void) } #endif /* CONFIG_SMP */ -void rebuild_sched_domains(void) +static void rebuild_sched_domains_cpuslocked(void) { - cpus_read_lock(); mutex_lock(&cpuset_mutex); rebuild_sched_domains_locked(); mutex_unlock(&cpuset_mutex); +} + +void rebuild_sched_domains(void) +{ + cpus_read_lock(); + rebuild_sched_domains_cpuslocked(); cpus_read_unlock(); } @@ -2079,14 +2074,11 @@ write_error: /* * For partcmd_update without newmask, it is being called from - * cpuset_hotplug_workfn() where cpus_read_lock() wasn't taken. - * Update the load balance flag and scheduling domain if - * cpus_read_trylock() is successful. + * cpuset_handle_hotplug(). Update the load balance flag and + * scheduling domain accordingly. */ - if ((cmd == partcmd_update) && !newmask && cpus_read_trylock()) { + if ((cmd == partcmd_update) && !newmask) update_partition_sd_lb(cs, old_prs); - cpus_read_unlock(); - } notify_partition_change(cs, old_prs); return 0; @@ -3599,8 +3591,8 @@ static ssize_t cpuset_write_resmask(struct kernfs_open_file *of, * proceeding, so that we don't end up keep removing tasks added * after execution capability is restored. * - * cpuset_hotplug_work calls back into cgroup core via - * cgroup_transfer_tasks() and waiting for it from a cgroupfs + * cpuset_handle_hotplug may call back into cgroup core asynchronously + * via cgroup_transfer_tasks() and waiting for it from a cgroupfs * operation like this one can lead to a deadlock through kernfs * active_ref protection. Let's break the protection. Losing the * protection is okay as we check whether @cs is online after @@ -3609,7 +3601,6 @@ static ssize_t cpuset_write_resmask(struct kernfs_open_file *of, */ css_get(&cs->css); kernfs_break_active_protection(of->kn); - flush_work(&cpuset_hotplug_work); cpus_read_lock(); mutex_lock(&cpuset_mutex); @@ -4354,6 +4345,16 @@ static void remove_tasks_in_empty_cpuset(struct cpuset *cs) } } +static void cpuset_migrate_tasks_workfn(struct work_struct *work) +{ + struct cpuset_remove_tasks_struct *s; + + s = container_of(work, struct cpuset_remove_tasks_struct, work); + remove_tasks_in_empty_cpuset(s->cs); + css_put(&s->cs->css); + kfree(s); +} + static void hotplug_update_tasks_legacy(struct cpuset *cs, struct cpumask *new_cpus, nodemask_t *new_mems, @@ -4383,12 +4384,21 @@ hotplug_update_tasks_legacy(struct cpuset *cs, /* * Move tasks to the nearest ancestor with execution resources, * This is full cgroup operation which will also call back into - * cpuset. Should be done outside any lock. + * cpuset. Execute it asynchronously using workqueue. */ - if (is_empty) { - mutex_unlock(&cpuset_mutex); - remove_tasks_in_empty_cpuset(cs); - mutex_lock(&cpuset_mutex); + if (is_empty && cs->css.cgroup->nr_populated_csets && + css_tryget_online(&cs->css)) { + struct cpuset_remove_tasks_struct *s; + + s = kzalloc(sizeof(*s), GFP_KERNEL); + if (WARN_ON_ONCE(!s)) { + css_put(&cs->css); + return; + } + + s->cs = cs; + INIT_WORK(&s->work, cpuset_migrate_tasks_workfn); + schedule_work(&s->work); } } @@ -4421,30 +4431,6 @@ void cpuset_force_rebuild(void) force_rebuild = true; } -/* - * Attempt to acquire a cpus_read_lock while a hotplug operation may be in - * progress. - * Return: true if successful, false otherwise - * - * To avoid circular lock dependency between cpuset_mutex and cpus_read_lock, - * cpus_read_trylock() is used here to acquire the lock. - */ -static bool cpuset_hotplug_cpus_read_trylock(void) -{ - int retries = 0; - - while (!cpus_read_trylock()) { - /* - * CPU hotplug still in progress. Retry 5 times - * with a 10ms wait before bailing out. - */ - if (++retries > 5) - return false; - msleep(10); - } - return true; -} - /** * cpuset_hotplug_update_tasks - update tasks in a cpuset for hotunplug * @cs: cpuset in interest @@ -4493,13 +4479,11 @@ retry: compute_partition_effective_cpumask(cs, &new_cpus); if (remote && cpumask_empty(&new_cpus) && - partition_is_populated(cs, NULL) && - cpuset_hotplug_cpus_read_trylock()) { + partition_is_populated(cs, NULL)) { remote_partition_disable(cs, tmp); compute_effective_cpumask(&new_cpus, cs, parent); remote = false; cpuset_force_rebuild(); - cpus_read_unlock(); } /* @@ -4519,18 +4503,8 @@ retry: else if (is_partition_valid(parent) && is_partition_invalid(cs)) partcmd = partcmd_update; - /* - * cpus_read_lock needs to be held before calling - * update_parent_effective_cpumask(). To avoid circular lock - * dependency between cpuset_mutex and cpus_read_lock, - * cpus_read_trylock() is used here to acquire the lock. - */ if (partcmd >= 0) { - if (!cpuset_hotplug_cpus_read_trylock()) - goto update_tasks; - update_parent_effective_cpumask(cs, partcmd, NULL, tmp); - cpus_read_unlock(); if ((partcmd == partcmd_invalidate) || is_partition_valid(cs)) { compute_partition_effective_cpumask(cs, &new_cpus); cpuset_force_rebuild(); @@ -4558,8 +4532,7 @@ unlock: } /** - * cpuset_hotplug_workfn - handle CPU/memory hotunplug for a cpuset - * @work: unused + * cpuset_handle_hotplug - handle CPU/memory hot{,un}plug for a cpuset * * This function is called after either CPU or memory configuration has * changed and updates cpuset accordingly. The top_cpuset is always @@ -4573,8 +4546,10 @@ unlock: * * Note that CPU offlining during suspend is ignored. We don't modify * cpusets across suspend/resume cycles at all. + * + * CPU / memory hotplug is handled synchronously. */ -static void cpuset_hotplug_workfn(struct work_struct *work) +static void cpuset_handle_hotplug(void) { static cpumask_t new_cpus; static nodemask_t new_mems; @@ -4585,6 +4560,7 @@ static void cpuset_hotplug_workfn(struct work_struct *work) if (on_dfl && !alloc_cpumasks(NULL, &tmp)) ptmp = &tmp; + lockdep_assert_cpus_held(); mutex_lock(&cpuset_mutex); /* fetch the available cpus/mems and find out which changed how */ @@ -4666,7 +4642,7 @@ static void cpuset_hotplug_workfn(struct work_struct *work) /* rebuild sched domains if cpus_allowed has changed */ if (cpus_updated || force_rebuild) { force_rebuild = false; - rebuild_sched_domains(); + rebuild_sched_domains_cpuslocked(); } free_cpumasks(NULL, ptmp); @@ -4679,12 +4655,7 @@ void cpuset_update_active_cpus(void) * inside cgroup synchronization. Bounce actual hotplug processing * to a work item to avoid reverse locking order. */ - schedule_work(&cpuset_hotplug_work); -} - -void cpuset_wait_for_hotplug(void) -{ - flush_work(&cpuset_hotplug_work); + cpuset_handle_hotplug(); } /* @@ -4695,7 +4666,7 @@ void cpuset_wait_for_hotplug(void) static int cpuset_track_online_nodes(struct notifier_block *self, unsigned long action, void *arg) { - schedule_work(&cpuset_hotplug_work); + cpuset_handle_hotplug(); return NOTIFY_OK; } diff --git a/kernel/cpu.c b/kernel/cpu.c index 8f6affd051f7..49ce3f309688 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1208,52 +1208,6 @@ void __init cpuhp_threads_init(void) kthread_unpark(this_cpu_read(cpuhp_state.thread)); } -/* - * - * Serialize hotplug trainwrecks outside of the cpu_hotplug_lock - * protected region. - * - * The operation is still serialized against concurrent CPU hotplug via - * cpu_add_remove_lock, i.e. CPU map protection. But it is _not_ - * serialized against other hotplug related activity like adding or - * removing of state callbacks and state instances, which invoke either the - * startup or the teardown callback of the affected state. - * - * This is required for subsystems which are unfixable vs. CPU hotplug and - * evade lock inversion problems by scheduling work which has to be - * completed _before_ cpu_up()/_cpu_down() returns. - * - * Don't even think about adding anything to this for any new code or even - * drivers. It's only purpose is to keep existing lock order trainwrecks - * working. - * - * For cpu_down() there might be valid reasons to finish cleanups which are - * not required to be done under cpu_hotplug_lock, but that's a different - * story and would be not invoked via this. - */ -static void cpu_up_down_serialize_trainwrecks(bool tasks_frozen) -{ - /* - * cpusets delegate hotplug operations to a worker to "solve" the - * lock order problems. Wait for the worker, but only if tasks are - * _not_ frozen (suspend, hibernate) as that would wait forever. - * - * The wait is required because otherwise the hotplug operation - * returns with inconsistent state, which could even be observed in - * user space when a new CPU is brought up. The CPU plug uevent - * would be delivered and user space reacting on it would fail to - * move tasks to the newly plugged CPU up to the point where the - * work has finished because up to that point the newly plugged CPU - * is not assignable in cpusets/cgroups. On unplug that's not - * necessarily a visible issue, but it is still inconsistent state, - * which is the real problem which needs to be "fixed". This can't - * prevent the transient state between scheduling the work and - * returning from waiting for it. - */ - if (!tasks_frozen) - cpuset_wait_for_hotplug(); -} - #ifdef CONFIG_HOTPLUG_CPU #ifndef arch_clear_mm_cpumask_cpu #define arch_clear_mm_cpumask_cpu(cpu, mm) cpumask_clear_cpu(cpu, mm_cpumask(mm)) @@ -1494,7 +1448,6 @@ out: */ lockup_detector_cleanup(); arch_smt_update(); - cpu_up_down_serialize_trainwrecks(tasks_frozen); return ret; } @@ -1728,7 +1681,6 @@ static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target) out: cpus_write_unlock(); arch_smt_update(); - cpu_up_down_serialize_trainwrecks(tasks_frozen); return ret; } diff --git a/kernel/power/process.c b/kernel/power/process.c index cae81a87cc91..66ac067d9ae6 100644 --- a/kernel/power/process.c +++ b/kernel/power/process.c @@ -194,8 +194,6 @@ void thaw_processes(void) __usermodehelper_set_disable_depth(UMH_FREEZING); thaw_workqueues(); - cpuset_wait_for_hotplug(); - read_lock(&tasklist_lock); for_each_process_thread(g, p) { /* No other threads should have PF_SUSPEND_TASK set */ |