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From:   Chengming Zhou <zhouchengming@bytedance.com>
To:     linux-kernel@vger.kernel.org, pmladek@suse.com,
        sergey.senozhatsky@gmail.com, rostedt@goodmis.org,
        mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
        vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
        bsegall@google.com, mgorman@suse.de
Cc:     zhouchengming@bytedance.com, songmuchun@bytedance.com
Subject: [PATCH 2/2] sched: mark PRINTK_DEFERRED_CONTEXT_MASK in __schedule()
Date:   Mon, 28 Sep 2020 00:11:30 +0800
Message-Id: <20200927161130.33172-2-zhouchengming@bytedance.com>
In-Reply-To: <20200927161130.33172-1-zhouchengming@bytedance.com>
References: <20200927161130.33172-1-zhouchengming@bytedance.com>
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The WARN_ON/WARN_ON_ONCE with rq lock held in __schedule() should be
deferred by marking the PRINTK_DEFERRED_CONTEXT_MASK, or will cause
deadlock on rq lock in the printk path.

Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 kernel/sched/core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 2d95dc3f4644..81d8bf614225 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4444,6 +4444,7 @@ static void __sched notrace __schedule(bool preempt)
 	 */
 	rq_lock(rq, &rf);
 	smp_mb__after_spinlock();
+	printk_deferred_enter();
 
 	/* Promote REQ to ACT */
 	rq->clock_update_flags <<= 1;
@@ -4530,6 +4531,7 @@ static void __sched notrace __schedule(bool preempt)
 		rq_unlock_irq(rq, &rf);
 	}
 
+	printk_deferred_exit();
 	balance_callback(rq);
 }
 
-- 
2.11.0