diff options
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/core.c | 22 | ||||
| -rw-r--r-- | kernel/sched/sched.h | 12 |
2 files changed, 22 insertions, 12 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 3bdf01b494fe..7f3063c153d8 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -684,10 +684,16 @@ static void wake_up_idle_cpu(int cpu) static bool wake_up_full_nohz_cpu(int cpu) { + /* + * We just need the target to call irq_exit() and re-evaluate + * the next tick. The nohz full kick at least implies that. + * If needed we can still optimize that later with an + * empty IRQ. + */ if (tick_nohz_full_cpu(cpu)) { if (cpu != smp_processor_id() || tick_nohz_tick_stopped()) - smp_send_reschedule(cpu); + tick_nohz_full_kick_cpu(cpu); return true; } @@ -734,10 +740,11 @@ bool sched_can_stop_tick(void) rq = this_rq(); - /* Make sure rq->nr_running update is visible after the IPI */ - smp_rmb(); - - /* More than one running task need preemption */ + /* + * More than one running task need preemption. + * nr_running update is assumed to be visible + * after IPI is sent from wakers. + */ if (rq->nr_running > 1) return false; @@ -1568,9 +1575,7 @@ void scheduler_ipi(void) */ preempt_fold_need_resched(); - if (llist_empty(&this_rq()->wake_list) - && !tick_nohz_full_cpu(smp_processor_id()) - && !got_nohz_idle_kick()) + if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick()) return; /* @@ -1587,7 +1592,6 @@ void scheduler_ipi(void) * somewhat pessimize the simple resched case. */ irq_enter(); - tick_nohz_full_check(); sched_ttwu_pending(); /* diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 31cc02ebc54e..eb8567610295 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1221,9 +1221,15 @@ static inline void add_nr_running(struct rq *rq, unsigned count) #ifdef CONFIG_NO_HZ_FULL if (prev_nr < 2 && rq->nr_running >= 2) { if (tick_nohz_full_cpu(rq->cpu)) { - /* Order rq->nr_running write against the IPI */ - smp_wmb(); - smp_send_reschedule(rq->cpu); + /* + * Tick is needed if more than one task runs on a CPU. + * Send the target an IPI to kick it out of nohz mode. + * + * We assume that IPI implies full memory barrier and the + * new value of rq->nr_running is visible on reception + * from the target. + */ + tick_nohz_full_kick_cpu(rq->cpu); } } #endif |