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From:   Schspa Shi <schspa@gmail.com>
To:     mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
        vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
        rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
        bristot@redhat.com, vschneid@redhat.com
Cc:     linux-kernel@vger.kernel.org, Schspa Shi <schspa@gmail.com>
Subject: [PATCH] sched: Dump stacktrace when some task failed to stop
Date:   Fri, 20 May 2022 00:11:25 +0800
Message-Id: <20220519161125.41144-1-schspa@gmail.com>
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Some processes may not be stopped, such as workqueue workers.

Add this dump_stack to easily figure out which process caused the problems.

Before this change:

<4>[  517.545889] ------------[ cut here ]------------
<4>[  517.545901] Dying CPU not properly vacated!
<4>[  517.546366] ---[ end trace 0000000000000002 ]---
<4>[  518.546831] CPU6 enqueued tasks (2 total):
<4>[  518.546855] 	pid: 49, name: migration/6
<4>[  518.547010] 	pid: 6231, name: kworker/6:0

Signed-off-by: Schspa Shi <schspa@gmail.com>
---
 kernel/sched/core.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 53596842f0d8..de6b5320e4d7 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9416,7 +9416,14 @@ static void dump_rq_tasks(struct rq *rq, const char *loglvl)
 			continue;
 
 		printk("%s\tpid: %d, name: %s\n", loglvl, p->pid, p->comm);
+		if (p != current)
+			sched_show_task(p);
 	}
+	/*
+	 * We need the stack of each cpu to analyze who is blocking the
+	 * current cpu scheduling
+	 */
+	trigger_all_cpu_backtrace();
 }
 
 int sched_cpu_dying(unsigned int cpu)
-- 
2.24.3 (Apple Git-128)