The following commit has been merged into the sched/core branch of tip: Commit-ID: 126c2092e5c8b28623cb890cd2930aa292410676 Gitweb: https://git.kernel.org/tip/126c2092e5c8b28623cb890cd2930aa292410676 Author: Peter Zijlstra <pet...@infradead.org> AuthorDate: Tue, 26 May 2020 18:11:03 +02:00 Committer: Ingo Molnar <mi...@kernel.org> CommitterDate: Thu, 28 May 2020 10:54:16 +02:00
sched: Add rq::ttwu_pending In preparation of removing rq->wake_list, replace the !list_empty(rq->wake_list) with rq->ttwu_pending. This is not fully equivalent as this new variable is racy. Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Signed-off-by: Ingo Molnar <mi...@kernel.org> Link: https://lore.kernel.org/r/20200526161908.070399...@infradead.org --- kernel/sched/core.c | 13 +++++++++++-- kernel/sched/debug.c | 1 - kernel/sched/fair.c | 2 +- kernel/sched/sched.h | 4 +++- 4 files changed, 15 insertions(+), 5 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index fa0d499..b71ed5e 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2275,13 +2275,21 @@ static int ttwu_remote(struct task_struct *p, int wake_flags) void sched_ttwu_pending(void) { struct rq *rq = this_rq(); - struct llist_node *llist = llist_del_all(&rq->wake_list); + struct llist_node *llist; struct task_struct *p, *t; struct rq_flags rf; + llist = llist_del_all(&rq->wake_list); if (!llist) return; + /* + * rq::ttwu_pending racy indication of out-standing wakeups. + * Races such that false-negatives are possible, since they + * are shorter lived that false-positives would be. + */ + WRITE_ONCE(rq->ttwu_pending, 0); + rq_lock_irqsave(rq, &rf); update_rq_clock(rq); @@ -2318,6 +2326,7 @@ static void __ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED); + WRITE_ONCE(rq->ttwu_pending, 1); if (llist_add(&p->wake_entry, &rq->wake_list)) { if (!set_nr_if_polling(rq->idle)) smp_call_function_single_async(cpu, &rq->wake_csd); @@ -4705,7 +4714,7 @@ int idle_cpu(int cpu) return 0; #ifdef CONFIG_SMP - if (!llist_empty(&rq->wake_list)) + if (rq->ttwu_pending) return 0; #endif diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 1c24a6b..36c5426 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -638,7 +638,6 @@ do { \ P(nr_running); P(nr_switches); - P(nr_load_updates); P(nr_uninterruptible); PN(next_balance); SEQ_printf(m, " .%-30s: %ld\n", "curr->pid", (long)(task_pid_nr(rq->curr))); diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 2890bd5..0ed04d2 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8590,7 +8590,7 @@ static int idle_cpu_without(int cpu, struct task_struct *p) */ #ifdef CONFIG_SMP - if (!llist_empty(&rq->wake_list)) + if (rq->ttwu_pending) return 0; #endif diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 75b0629..c86fc94 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -895,7 +895,9 @@ struct rq { atomic_t nohz_flags; #endif /* CONFIG_NO_HZ_COMMON */ - unsigned long nr_load_updates; +#ifdef CONFIG_SMP + unsigned int ttwu_pending; +#endif u64 nr_switches; #ifdef CONFIG_UCLAMP_TASK
