diff options
author | Peter Zijlstra (Intel) <peterz@infradead.org> | 2020-03-27 11:44:56 +0100 |
---|---|---|
committer | Thomas Gleixner <tglx@linutronix.de> | 2020-05-12 17:10:48 +0200 |
commit | 90b5363acd4739769c3f38c1aff16171bd133e8c (patch) | |
tree | a735cefbe7aa985a4bb70caf58b2a961a140f45b /kernel/sched | |
parent | b1d1779e5ef7a60b192b61fd97201f322e1e9303 (diff) | |
download | linux-90b5363acd4739769c3f38c1aff16171bd133e8c.tar.bz2 |
sched: Clean up scheduler_ipi()
The scheduler IPI has grown weird and wonderful over the years, time
for spring cleaning.
Move all the non-trivial stuff out of it and into a regular smp function
call IPI. This then reduces the schedule_ipi() to most of it's former NOP
glory and ensures to keep the interrupt vector lean and mean.
Aside of that avoiding the full irq_enter() in the x86 IPI implementation
is incorrect as scheduler_ipi() can be instrumented. To work around that
scheduler_ipi() had an irq_enter/exit() hack when heavy work was
pending. This is gone now.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Link: https://lkml.kernel.org/r/20200505134058.361859938@linutronix.de
Diffstat (limited to 'kernel/sched')
-rw-r--r-- | kernel/sched/core.c | 64 | ||||
-rw-r--r-- | kernel/sched/fair.c | 5 | ||||
-rw-r--r-- | kernel/sched/sched.h | 6 |
3 files changed, 36 insertions, 39 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index b58efb1156eb..cd2070d6f1e4 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -219,6 +219,13 @@ void update_rq_clock(struct rq *rq) update_rq_clock_task(rq, delta); } +static inline void +rq_csd_init(struct rq *rq, call_single_data_t *csd, smp_call_func_t func) +{ + csd->flags = 0; + csd->func = func; + csd->info = rq; +} #ifdef CONFIG_SCHED_HRTICK /* @@ -314,16 +321,14 @@ void hrtick_start(struct rq *rq, u64 delay) hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay), HRTIMER_MODE_REL_PINNED_HARD); } + #endif /* CONFIG_SMP */ static void hrtick_rq_init(struct rq *rq) { #ifdef CONFIG_SMP - rq->hrtick_csd.flags = 0; - rq->hrtick_csd.func = __hrtick_start; - rq->hrtick_csd.info = rq; + rq_csd_init(rq, &rq->hrtick_csd, __hrtick_start); #endif - hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD); rq->hrtick_timer.function = hrtick; } @@ -650,6 +655,16 @@ static inline bool got_nohz_idle_kick(void) return false; } +static void nohz_csd_func(void *info) +{ + struct rq *rq = info; + + if (got_nohz_idle_kick()) { + rq->idle_balance = 1; + raise_softirq_irqoff(SCHED_SOFTIRQ); + } +} + #else /* CONFIG_NO_HZ_COMMON */ static inline bool got_nohz_idle_kick(void) @@ -2292,6 +2307,11 @@ void sched_ttwu_pending(void) rq_unlock_irqrestore(rq, &rf); } +static void wake_csd_func(void *info) +{ + sched_ttwu_pending(); +} + void scheduler_ipi(void) { /* @@ -2300,34 +2320,6 @@ void scheduler_ipi(void) * this IPI. */ preempt_fold_need_resched(); - - if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick()) - return; - - /* - * 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. - * - * 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. - */ - irq_enter(); - sched_ttwu_pending(); - - /* - * 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); - } - irq_exit(); } static void ttwu_queue_remote(struct task_struct *p, int cpu, int wake_flags) @@ -2336,9 +2328,9 @@ static void ttwu_queue_remote(struct task_struct *p, int cpu, int wake_flags) p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED); - if (llist_add(&p->wake_entry, &cpu_rq(cpu)->wake_list)) { + if (llist_add(&p->wake_entry, &rq->wake_list)) { if (!set_nr_if_polling(rq->idle)) - smp_send_reschedule(cpu); + smp_call_function_single_async(cpu, &rq->wake_csd); else trace_sched_wake_idle_without_ipi(cpu); } @@ -6693,12 +6685,16 @@ void __init sched_init(void) rq->avg_idle = 2*sysctl_sched_migration_cost; rq->max_idle_balance_cost = sysctl_sched_migration_cost; + rq_csd_init(rq, &rq->wake_csd, wake_csd_func); + INIT_LIST_HEAD(&rq->cfs_tasks); rq_attach_root(rq, &def_root_domain); #ifdef CONFIG_NO_HZ_COMMON rq->last_blocked_load_update_tick = jiffies; atomic_set(&rq->nohz_flags, 0); + + rq_csd_init(rq, &rq->nohz_csd, nohz_csd_func); #endif #endif /* CONFIG_SMP */ hrtick_rq_init(rq); diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 46b7bd41573f..6b7f1474e2d6 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -10000,12 +10000,11 @@ static void kick_ilb(unsigned int flags) return; /* - * Use smp_send_reschedule() instead of resched_cpu(). - * This way we generate a sched IPI on the target CPU which + * This way we generate an IPI on the target CPU which * is idle. And the softirq performing nohz idle load balance * will be run before returning from the IPI. */ - smp_send_reschedule(ilb_cpu); + smp_call_function_single_async(ilb_cpu, &cpu_rq(ilb_cpu)->nohz_csd); } /* diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 978c6fac8cb8..21416b30c520 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -889,9 +889,10 @@ struct rq { #ifdef CONFIG_SMP unsigned long last_blocked_load_update_tick; unsigned int has_blocked_load; + call_single_data_t nohz_csd; #endif /* CONFIG_SMP */ unsigned int nohz_tick_stopped; - atomic_t nohz_flags; + atomic_t nohz_flags; #endif /* CONFIG_NO_HZ_COMMON */ unsigned long nr_load_updates; @@ -978,7 +979,7 @@ struct rq { /* This is used to determine avg_idle's max value */ u64 max_idle_balance_cost; -#endif +#endif /* CONFIG_SMP */ #ifdef CONFIG_IRQ_TIME_ACCOUNTING u64 prev_irq_time; @@ -1020,6 +1021,7 @@ struct rq { #endif #ifdef CONFIG_SMP + call_single_data_t wake_csd; struct llist_head wake_list; #endif |