[PATCH v2 04/11] sched: Simplify wake_up_*idle*()
From: Peter Zijlstra <peterz@infradead.org>
Date: 2021-09-29 16:08:46
Also in:
lkml
Simplify and make wake_up_if_idle() more robust, also don't iterate the whole machine with preempt_disable() in it's caller: wake_up_all_idle_cpus(). This prepares for another wake_up_if_idle() user that needs a full do_idle() cycle. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- kernel/sched/core.c | 14 +++++--------- kernel/smp.c | 6 +++--- 2 files changed, 8 insertions(+), 12 deletions(-)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c@@ -3691,15 +3691,11 @@ void wake_up_if_idle(int cpu) if (!is_idle_task(rcu_dereference(rq->curr))) goto out; - if (set_nr_if_polling(rq->idle)) { - trace_sched_wake_idle_without_ipi(cpu); - } else { - rq_lock_irqsave(rq, &rf); - if (is_idle_task(rq->curr)) - smp_send_reschedule(cpu); - /* Else CPU is not idle, do nothing here: */ - rq_unlock_irqrestore(rq, &rf); - } + rq_lock_irqsave(rq, &rf); + if (is_idle_task(rq->curr)) + resched_curr(rq); + /* Else CPU is not idle, do nothing here: */ + rq_unlock_irqrestore(rq, &rf); out: rcu_read_unlock(); --- a/kernel/smp.c +++ b/kernel/smp.c
@@ -1170,14 +1170,14 @@ void wake_up_all_idle_cpus(void) { int cpu; - preempt_disable(); + cpus_read_lock(); for_each_online_cpu(cpu) { - if (cpu == smp_processor_id()) + if (cpu == raw_smp_processor_id()) continue; wake_up_if_idle(cpu); } - preempt_enable(); + cpus_read_unlock(); } EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus);