From: Vincent Donnefort <vincent.donnefort@arm.com>
To: peterz@infradead.org, mingo@redhat.com, vincent.guittot@linaro.org
Cc: linux-kernel@vger.kernel.org, mgorman@techsingularity.net,
dietmar.eggemann@arm.com, valentin.schneider@arm.com,
Vincent Donnefort <vincent.donnefort@arm.com>
Subject: [PATCH] sched/fair: Fix detection of per-CPU kthreads waking a task
Date: Wed, 24 Nov 2021 15:42:39 +0000 [thread overview]
Message-ID: <20211124154239.3191366-1-vincent.donnefort@arm.com> (raw)
select_idle_sibling() will return prev_cpu for the case where the task is
woken up by a per-CPU kthread. However, the idle task has been recently
modified and is now identified by is_per_cpu_kthread(), breaking the
behaviour described above. Using !is_idle_task() ensures we do not
spuriously trigger that select_idle_sibling() exit path.
Fixes: 00b89fe0197f ("sched: Make the idle task quack like a per-CPU kthread")
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 945d987246c5..8bf95b0e368d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6399,6 +6399,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
* pattern is IO completions.
*/
if (is_per_cpu_kthread(current) &&
+ !is_idle_task(current) &&
prev == smp_processor_id() &&
this_rq()->nr_running <= 1) {
return prev;
--
2.25.1
next reply other threads:[~2021-11-24 15:43 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-24 15:42 Vincent Donnefort [this message]
2021-11-24 16:28 ` [PATCH] sched/fair: Fix detection of per-CPU kthreads waking a task Valentin Schneider
2021-11-25 9:05 ` Vincent Guittot
2021-11-25 11:16 ` Valentin Schneider
2021-11-25 13:17 ` Dietmar Eggemann
2021-11-25 13:23 ` Vincent Guittot
2021-11-25 15:30 ` Valentin Schneider
2021-11-26 8:23 ` Vincent Guittot
2021-11-26 13:32 ` Valentin Schneider
2021-11-26 14:40 ` Vincent Guittot
2021-11-26 16:49 ` Valentin Schneider
2021-11-26 17:18 ` Vincent Donnefort
2021-11-29 15:49 ` Vincent Guittot
2021-11-29 16:54 ` Vincent Donnefort
2021-11-30 13:35 ` Dietmar Eggemann
2021-11-30 15:42 ` Vincent Guittot
2021-12-01 14:40 ` Vincent Donnefort
2021-12-01 16:19 ` Vincent Guittot
2021-11-29 8:36 ` [sched/fair] 8d0920b981: stress-ng.sem.ops_per_sec 11.9% improvement kernel test robot
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