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Subject: Re: [PATCH v4 11/19] sched/core: Make migrate disable and CPU
 hotplug cooperative
From:   Qian Cai <cai@redhat.com>
To:     Valentin Schneider <valentin.schneider@arm.com>
Cc:     Peter Zijlstra <peterz@infradead.org>, tglx@linutronix.de,
        mingo@kernel.org, linux-kernel@vger.kernel.org,
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        dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com,
        mgorman@suse.de, bristot@redhat.com, vincent.donnefort@arm.com,
        tj@kernel.org, ouwen210@hotmail.com
Date:   Wed, 18 Nov 2020 09:44:34 -0500
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On Tue, 2020-11-17 at 19:28 +0000, Valentin Schneider wrote:
> We did have some breakage in that area, but all the holes I was aware of
> have been plugged. What would help here is to see which tasks are still
> queued on that outgoing CPU, and their recent activity.
> 
> Something like
> - ftrace_dump_on_oops on your kernel cmdline
> - trace-cmd start -e 'sched:*'
>  <start the test here>
> 
> ought to do it. Then you can paste the (tail of the) ftrace dump.
> 
> I also had this laying around, which may or may not be of some help:

Once I have found a reliable reproducer, I'll report back.