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From:   Wander Lairson Costa <wander@redhat.com>
To:     Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
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        "Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>,
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        Wander Lairson Costa <wander@redhat.com>,
        Kefeng Wang <wangkefeng.wang@huawei.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
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        linux-kernel@vger.kernel.org (open list)
Subject: [PATCH v2 4/4] sched/core: use put_task_struct_atomic_safe() to avoid potential splat
Date:   Fri, 20 Jan 2023 12:02:42 -0300
Message-Id: <20230120150246.20797-5-wander@redhat.com>
In-Reply-To: <20230120150246.20797-1-wander@redhat.com>
References: <20230120150246.20797-1-wander@redhat.com>
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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@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.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