linux-kernel - [GIT PULL] scheduler fix

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Message-ID: <aQ9BsTHEl9jdRtUm@gmail.com>
Date: Sat, 8 Nov 2025 14:12:17 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: [GIT PULL] scheduler fix

Linus,

Please pull the latest sched/urgent Git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched-urgent-2025-11-08

   # HEAD: 956dfda6a70885f18c0f8236a461aa2bc4f556ad sched/fair: Prevent cfs_rq from being unthrottled with zero runtime_remaining

Fix a group-throttling bug in the fair scheduler.

 Thanks,

	Ingo

------------------>
Aaron Lu (1):
      sched/fair: Prevent cfs_rq from being unthrottled with zero runtime_remaining


 kernel/sched/core.c |  2 +-
 kernel/sched/fair.c | 15 ++++++---------
 2 files changed, 7 insertions(+), 10 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f1ebf67b48e2..f754a60de848 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9606,7 +9606,7 @@ static int tg_set_cfs_bandwidth(struct task_group *tg,
 
 		guard(rq_lock_irq)(rq);
 		cfs_rq->runtime_enabled = runtime_enabled;
-		cfs_rq->runtime_remaining = 0;
+		cfs_rq->runtime_remaining = 1;
 
 		if (cfs_rq->throttled)
 			unthrottle_cfs_rq(cfs_rq);
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 25970dbbb279..5b752324270b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6024,20 +6024,17 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
 	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
 
 	/*
-	 * It's possible we are called with !runtime_remaining due to things
-	 * like user changed quota setting(see tg_set_cfs_bandwidth()) or async
-	 * unthrottled us with a positive runtime_remaining but other still
-	 * running entities consumed those runtime before we reached here.
+	 * It's possible we are called with runtime_remaining < 0 due to things
+	 * like async unthrottled us with a positive runtime_remaining but other
+	 * still running entities consumed those runtime before we reached here.
 	 *
-	 * Anyway, we can't unthrottle this cfs_rq without any runtime remaining
-	 * because any enqueue in tg_unthrottle_up() will immediately trigger a
-	 * throttle, which is not supposed to happen on unthrottle path.
+	 * We can't unthrottle this cfs_rq without any runtime remaining because
+	 * any enqueue in tg_unthrottle_up() will immediately trigger a throttle,
+	 * which is not supposed to happen on unthrottle path.
 	 */
 	if (cfs_rq->runtime_enabled && cfs_rq->runtime_remaining <= 0)
 		return;
 
-	se = cfs_rq->tg->se[cpu_of(rq)];
-
 	cfs_rq->throttled = 0;
 
 	update_rq_clock(rq);