linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
* [PATCH] sched/fair: Fix detection of per-CPU kthreads waking a task
@ 2021-11-24 15:42 Vincent Donnefort
  2021-11-24 16:28 ` Valentin Schneider
                   ` (2 more replies)
  0 siblings, 3 replies; 19+ messages in thread
From: Vincent Donnefort @ 2021-11-24 15:42 UTC (permalink / raw)
  To: peterz, mingo, vincent.guittot
  Cc: linux-kernel, mgorman, dietmar.eggemann, valentin.schneider,
	Vincent Donnefort

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


^ permalink raw reply related	[flat|nested] 19+ messages in thread

end of thread, other threads:[~2021-12-01 16:20 UTC | newest]

Thread overview: 19+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-11-24 15:42 [PATCH] sched/fair: Fix detection of per-CPU kthreads waking a task Vincent Donnefort
2021-11-24 16:28 ` 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

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).