From: Peter Zijlstra <peterz@infradead.org>
Date: Tue, 21 Sep 2021 20:16:02 +0000 (+0200)
Subject: sched: Simplify wake_up_*idle*()
X-Git-Tag: v5.16-rc1~197^2~29
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8850cb663b5cda04d33f9cfbc38889d73d3c8e24;p=thirdparty%2Fkernel%2Flinux.git

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: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Vasily 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
---

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 74db3c3afa6d4..3b55ef99c03ff 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -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);
-		/* 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();
diff --git a/kernel/smp.c b/kernel/smp.c
index f43ede0ab183a..ad0b68a3a3d36 100644
--- 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);