linux-kernel - [tip: sched/core] sched/fair: Fix sched_can_stop

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Message-ID: <173374201363.412.6879199999203287235.tip-bot2@tip-bot2>
Date: Mon, 09 Dec 2024 11:00:13 -0000
From: "tip-bot2 for Vincent Guittot" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Vincent Guittot <vincent.guittot@...aro.org>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject:
 [tip: sched/core] sched/fair: Fix sched_can_stop_tick() for fair tasks

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     c1f43c342e1f2e32f0620bf2e972e2a9ea0a1e60
Gitweb:        https://git.kernel.org/tip/c1f43c342e1f2e32f0620bf2e972e2a9ea0a1e60
Author:        Vincent Guittot <vincent.guittot@...aro.org>
AuthorDate:    Mon, 02 Dec 2024 18:45:56 +01:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Mon, 09 Dec 2024 11:48:09 +01:00

sched/fair: Fix sched_can_stop_tick() for fair tasks

We can't stop the tick of a rq if there are at least 2 tasks enqueued in
the whole hierarchy and not only at the root cfs rq.

rq->cfs.nr_running tracks the number of sched_entity at one level
whereas rq->cfs.h_nr_running tracks all queued tasks in the
hierarchy.

Fixes: 11cc374f4643b ("sched_ext: Simplify scx_can_stop_tick() invocation in sched_can_stop_tick()")
Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@....com>
Link: https://lore.kernel.org/r/20241202174606.4074512-2-vincent.guittot@linaro.org
---
 kernel/sched/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c6d8232..3e5a6bf 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1341,7 +1341,7 @@ bool sched_can_stop_tick(struct rq *rq)
 	if (scx_enabled() && !scx_can_stop_tick(rq))
 		return false;
 
-	if (rq->cfs.nr_running > 1)
+	if (rq->cfs.h_nr_running > 1)
 		return false;
 
 	/*