Commit 8850cb66 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

sched: Simplify wake_up_*idle*() 



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: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarVasily Gorbik <gor@linux.ibm.com>
Tested-by: Vasily Gorbik <gor@linux.ibm.com> # on s390
Link: https://lkml.kernel.org/r/20210929152428.769328779@infradead.org
parent 00619f7c

kernel/sched/core.c

+5 −9
Original line number Diff line number Diff line
@@ -3695,15 +3695,11 @@ 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);

		resched_curr(rq);

	/* Else CPU is not idle, do nothing here: */

	rq_unlock_irqrestore(rq, &rf);

	}



out:

	rcu_read_unlock();

kernel/smp.c

+3 −3
Original line number Diff line number Diff line
@@ -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);