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) <[email protected]> Acked-by: Vasily Gorbik <[email protected]> Tested-by: Vasily Gorbik <[email protected]> # on s390 Link: https://lkml.kernel.org/r/[email protected]
amazonlinux · Oct 7, 2021 · 8850cb6 · 8850cb6
1 parent 00619f7
commit 8850cb6
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Showing 2 changed files with 8 additions and 12 deletions.
diff --git 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
@@ -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);