linux-kernel - [PATCH v2 4/4] sched/core: use put_task_struct_atomic

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Message-Id: <20230120150246.20797-5-wander@redhat.com>
Date:   Fri, 20 Jan 2023 12:02:42 -0300
From:   Wander Lairson Costa <wander@...hat.com>
To:     Ingo Molnar <mingo@...hat.com>,
        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>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Stafford Horne <shorne@...il.com>,
        "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
        Oleg Nesterov <oleg@...hat.com>,
        Wander Lairson Costa <wander@...hat.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Andrei Vagin <avagin@...il.com>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v2 4/4] sched/core: use put_task_struct_atomic_safe() to avoid potential splat

push_cpu_stop() is called form a context in which it must not sleep.
Since push_cpu_stop() calls put_task_struct(), it potentially can sleep
under PREEMPT_RT if the usage count reaches zero.

Use put_task_struct_atomic_safe(0 instead to avoid this potential splat.

Signed-off-by: Wander Lairson Costa <wander@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
---
 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 c437260e19b0..e5d0c66cb90c 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2565,7 +2565,7 @@ int push_cpu_stop(void *arg)
 	raw_spin_rq_unlock(rq);
 	raw_spin_unlock_irq(&p->pi_lock);
 
-	put_task_struct(p);
+	put_task_struct_atomic_safe(p);
 	return 0;
 }
 
-- 
2.39.0