linux-kernel - [RFC PATCH 6/7] sched/fair: fix tasks

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Message-ID: <CANCG0GehTMm3sbtXMy9MMFtG=kPYpHiFwy63OO4+dmXh68bWfA@mail.gmail.com>
Date: Thu, 13 Mar 2025 00:22:03 -0700
From: Aaron Lu <ziqianlu@...edance.com>
To: Valentin Schneider <vschneid@...hat.com>, Ben Segall <bsegall@...gle.com>, 
	K Prateek Nayak <kprateek.nayak@....com>, Peter Zijlstra <peterz@...radead.org>, 
	Josh Don <joshdon@...gle.com>, Ingo Molnar <mingo@...hat.com>, 
	Vincent Guittot <vincent.guittot@...aro.org>
Cc: linux-kernel@...r.kernel.org, Juri Lelli <juri.lelli@...hat.com>, 
	Dietmar Eggemann <dietmar.eggemann@....com>, Steven Rostedt <rostedt@...dmis.org>, 
	Mel Gorman <mgorman@...e.de>, Chengming Zhou <chengming.zhou@...ux.dev>, 
	Chuyi Zhou <zhouchuyi@...edance.com>
Subject: [RFC PATCH 6/7] sched/fair: fix tasks_rcu with task based throttle

Taskes throttled on exit to user path are scheduled by cond_resched() in
task_work_run() but that is a preempt schedule and doesn't mark a task
rcu quiescent state.

Fix this by directly calling schedule() in throttle_cfs_rq_work().

Signed-off-by: Aaron Lu <ziqianlu@...edance.com>
---
 kernel/sched/fair.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index f26d53ac143fe..be96f7d32998c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5847,6 +5847,7 @@ static void throttle_cfs_rq_work(struct
callback_head *work)
 	struct cfs_rq *cfs_rq;
 	struct rq *rq;
 	struct rq_flags rf;
+	bool sched = false;

 	WARN_ON_ONCE(p != current);
 	p->sched_throttle_work.next = &p->sched_throttle_work;
@@ -5879,9 +5880,13 @@ static void throttle_cfs_rq_work(struct
callback_head *work)
 	dequeue_task_fair(rq, p, DEQUEUE_SLEEP | DEQUEUE_SPECIAL);
 	list_add(&p->throttle_node, &cfs_rq->throttled_limbo_list);
 	resched_curr(rq);
+	sched = true;

 out_unlock:
 	task_rq_unlock(rq, p, &rf);
+
+	if (sched)
+		schedule();
 }

 void init_cfs_throttle_work(struct task_struct *p)
-- 
2.39.5