linux-kernel - Re: [PATCH v4 11/19] sched/core: Make migrate disable and CPU hotplug cooperative

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Message-ID: <dda3b8f67a23dd60d36e5325dbb0c406be18e1db.camel@redhat.com>
Date:   Wed, 18 Nov 2020 09:44:34 -0500
From:   Qian Cai <cai@...hat.com>
To:     Valentin Schneider <valentin.schneider@....com>
Cc:     Peter Zijlstra <peterz@...radead.org>, tglx@...utronix.de,
        mingo@...nel.org, linux-kernel@...r.kernel.org,
        bigeasy@...utronix.de, qais.yousef@....com, swood@...hat.com,
        juri.lelli@...hat.com, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, bristot@...hat.com, vincent.donnefort@....com,
        tj@...nel.org, ouwen210@...mail.com
Subject: Re: [PATCH v4 11/19] sched/core: Make migrate disable and CPU
 hotplug cooperative

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.