diff options
| -rw-r--r-- | kernel/sched/core.c | 54 | ||||
| -rw-r--r-- | kernel/sched/idle.c | 10 | ||||
| -rw-r--r-- | kernel/sched/sched.h | 6 |
3 files changed, 61 insertions, 9 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 6afbfeefddd6..60d4e05d64dd 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -519,7 +519,7 @@ static inline void init_hrtick(void) __old; \ }) -#ifdef TIF_POLLING_NRFLAG +#if defined(CONFIG_SMP) && defined(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 @@ -530,12 +530,44 @@ static bool set_nr_and_not_polling(struct task_struct *p) struct thread_info *ti = task_thread_info(p); return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG); } + +/* + * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set. + * + * If this returns true, then the idle task promises to call + * sched_ttwu_pending() and reschedule soon. + */ +static bool set_nr_if_polling(struct task_struct *p) +{ + struct thread_info *ti = task_thread_info(p); + typeof(ti->flags) old, val = ACCESS_ONCE(ti->flags); + + for (;;) { + 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; + } + return true; +} + #else static bool set_nr_and_not_polling(struct task_struct *p) { set_tsk_need_resched(p); return true; } + +#ifdef CONFIG_SMP +static bool set_nr_if_polling(struct task_struct *p) +{ + return false; +} +#endif #endif /* @@ -1490,13 +1522,17 @@ static int ttwu_remote(struct task_struct *p, int wake_flags) } #ifdef CONFIG_SMP -static void sched_ttwu_pending(void) +void sched_ttwu_pending(void) { struct rq *rq = this_rq(); struct llist_node *llist = llist_del_all(&rq->wake_list); struct task_struct *p; + unsigned long flags; - raw_spin_lock(&rq->lock); + if (!llist) + return; + + raw_spin_lock_irqsave(&rq->lock, flags); while (llist) { p = llist_entry(llist, struct task_struct, wake_entry); @@ -1504,7 +1540,7 @@ static void sched_ttwu_pending(void) ttwu_do_activate(rq, p, 0); } - raw_spin_unlock(&rq->lock); + raw_spin_unlock_irqrestore(&rq->lock, flags); } void scheduler_ipi(void) @@ -1550,8 +1586,14 @@ void scheduler_ipi(void) static void ttwu_queue_remote(struct task_struct *p, int cpu) { - if (llist_add(&p->wake_entry, &cpu_rq(cpu)->wake_list)) - smp_send_reschedule(cpu); + struct rq *rq = cpu_rq(cpu); + + 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); + } } bool cpus_share_cache(int this_cpu, int that_cpu) diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index fe4b24bf33ca..cf009fb0bc25 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -12,6 +12,8 @@ #include <trace/events/power.h> +#include "sched.h" + static int __read_mostly cpu_idle_force_poll; void cpu_idle_poll_ctrl(bool enable) @@ -237,12 +239,14 @@ static void cpu_idle_loop(void) __current_clr_polling(); /* - * We promise to reschedule if need_resched is set while - * polling is set. That means that clearing polling - * needs to be visible before rescheduling. + * We promise to call sched_ttwu_pending and reschedule + * if need_resched is set while polling is set. That + * means that clearing polling needs to be visible + * before doing these things. */ smp_mb__after_atomic(); + sched_ttwu_pending(); schedule_preempt_disabled(); } } diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 956b8ca24893..2f8636199b83 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -670,6 +670,8 @@ extern int migrate_swap(struct task_struct *, struct task_struct *); #ifdef CONFIG_SMP +extern void sched_ttwu_pending(void); + #define rcu_dereference_check_sched_domain(p) \ rcu_dereference_check((p), \ lockdep_is_held(&sched_domains_mutex)) @@ -787,6 +789,10 @@ static inline unsigned int group_first_cpu(struct sched_group *group) extern int group_balance_cpu(struct sched_group *sg); +#else + +static inline void sched_ttwu_pending(void) { } + #endif /* CONFIG_SMP */ #include "stats.h" |