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From: Valentin Schneider <valentin.schneider@arm.com>
To: Qian Cai <qcai@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	tglx@linutronix.de, mingo@kernel.org,
	linux-kernel@vger.kernel.org, bigeasy@linutronix.de,
	qais.yousef@arm.com, swood@redhat.com, juri.lelli@redhat.com,
	vincent.guittot@linaro.org, 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
Subject: Re: [PATCH v4 11/19] sched/core: Make migrate disable and CPU hotplug cooperative
Date: Sat, 05 Dec 2020 18:37:06 +0000	[thread overview]
Message-ID: <jhjwnxwt7zh.mognet@arm.com> (raw)
In-Reply-To: <c2c013282faf278ee6e0fc66deefbab165ff4e88.camel@redhat.com>


On 04/12/20 21:19, Qian Cai wrote:
> 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:
>
> Okay, your patch did not help, since it can still be reproduced using this,
>

It wasn't meant to fix this, only add some more debug prints :)

> https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/hotplug/cpu_hotplug/functional/cpuhotplug04.sh
>
> # while :; do cpuhotplug04.sh -l 1; done
>
> The ftrace dump has too much output on this 256-CPU system, so I have not had
> the patient to wait for it to finish after 15-min. But here is the log capturing
> so far (search for "kernel BUG" there).
>
> http://people.redhat.com/qcai/console.log
>

From there I see:

[20798.166987][  T650] CPU127 nr_running=2
[20798.171185][  T650]  p=migration/127
[20798.175161][  T650]  p=kworker/127:1

so this might be another workqueue hurdle. This should be prevented by:

  06249738a41a ("workqueue: Manually break affinity on hotplug")

In any case, I'll give this a try on a TX2 next week and see where it gets
me.

Note that much earlier in your log, you have a softlockup on CPU127:

[   74.278367][  C127] watchdog: BUG: soft lockup - CPU#127 stuck for 23s! [swapper/0:1]

  reply	other threads:[~2020-12-05 18:38 UTC|newest]

Thread overview: 81+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-23 10:11 [PATCH v4 00/19] sched: Migrate disable support Peter Zijlstra
2020-10-23 10:11 ` [PATCH v4 01/19] stop_machine: Add function and caller debug info Peter Zijlstra
2020-11-11  8:23   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2020-10-23 10:12 ` [PATCH v4 02/19] sched: Fix balance_callback() Peter Zijlstra
2020-11-11  8:23   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2020-11-11 20:30     ` Paul Bolle
2020-11-11 20:45       ` Peter Zijlstra
2020-10-23 10:12 ` [PATCH v4 03/19] sched/hotplug: Ensure only per-cpu kthreads run during hotplug Peter Zijlstra
2020-11-11  8:23   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2020-10-23 10:12 ` [PATCH v4 04/19] sched/core: Wait for tasks being pushed away on hotplug Peter Zijlstra
2020-11-11  8:23   ` [tip: sched/core] " tip-bot2 for Thomas Gleixner
2020-10-23 10:12 ` [PATCH v4 05/19] workqueue: Manually break affinity " Peter Zijlstra
2020-11-11  8:23   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2020-10-23 10:12 ` [PATCH v4 06/19] sched/hotplug: Consolidate task migration on CPU unplug Peter Zijlstra
2020-11-11  8:23   ` [tip: sched/core] " tip-bot2 for Thomas Gleixner
2020-10-23 10:12 ` [PATCH v4 07/19] sched: Fix hotplug vs CPU bandwidth control Peter Zijlstra
2020-11-11  8:23   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2020-10-23 10:12 ` [PATCH v4 08/19] sched: Massage set_cpus_allowed() Peter Zijlstra
2020-11-11  8:23   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2020-10-23 10:12 ` [PATCH v4 09/19] sched: Add migrate_disable() Peter Zijlstra
2020-11-11  8:23   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2020-10-23 10:12 ` [PATCH v4 10/19] sched: Fix migrate_disable() vs set_cpus_allowed_ptr() Peter Zijlstra
2020-11-11  8:23   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2020-11-12 16:38   ` [PATCH v4 10/19] " Qian Cai
2020-11-12 17:26     ` Valentin Schneider
2020-11-12 18:01       ` Qian Cai
2020-11-12 19:31         ` Valentin Schneider
2020-11-12 19:41           ` Qian Cai
2020-11-12 20:37           ` Qian Cai
2020-11-12 21:26             ` Valentin Schneider
2020-11-13 10:27           ` Peter Zijlstra
2020-11-12 18:35       ` Qian Cai
2020-11-20 12:34     ` [tip: sched/core] sched/core: Add missing completion for affine_move_task() waiters tip-bot2 for Valentin Schneider
2020-10-23 10:12 ` [PATCH v4 11/19] sched/core: Make migrate disable and CPU hotplug cooperative Peter Zijlstra
2020-10-29 16:27   ` Valentin Schneider
2020-10-29 17:34     ` Peter Zijlstra
2020-10-29 17:55       ` Valentin Schneider
2020-11-11  8:23   ` [tip: sched/core] " tip-bot2 for Thomas Gleixner
2020-11-13 15:06   ` [PATCH v4 11/19] " Qian Cai
2020-11-17 19:28     ` Valentin Schneider
2020-11-18 14:44       ` Qian Cai
2020-11-23 18:13         ` Sebastian Andrzej Siewior
2020-12-02 21:59           ` Qian Cai
2020-12-03 12:31           ` Qian Cai
2020-12-04  0:23       ` Qian Cai
2020-12-04 21:19       ` Qian Cai
2020-12-05 18:37         ` Valentin Schneider [this message]
2020-12-06  1:17           ` Qian Cai
2020-12-07 19:27         ` Valentin Schneider
2020-12-08 13:46           ` Qian Cai
2020-12-09 19:16             ` Valentin Schneider
2020-10-23 10:12 ` [PATCH v4 12/19] sched,rt: Use cpumask_any*_distribute() Peter Zijlstra
2020-11-11  8:23   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2020-10-23 10:12 ` [PATCH v4 13/19] sched,rt: Use the full cpumask for balancing Peter Zijlstra
2020-11-11  8:23   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2020-10-23 10:12 ` [PATCH v4 14/19] sched, lockdep: Annotate ->pi_lock recursion Peter Zijlstra
2020-10-29 16:27   ` Valentin Schneider
2020-10-29 17:38     ` Peter Zijlstra
2020-10-29 18:09       ` Valentin Schneider
2020-11-11  8:23   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2020-10-23 10:12 ` [PATCH v4 15/19] sched: Fix migrate_disable() vs rt/dl balancing Peter Zijlstra
2020-11-11  8:23   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2020-12-26 13:54   ` [PATCH v4 15/19] " Qais Yousef
2021-03-05 14:56     ` Peter Zijlstra
2021-03-05 15:41       ` Valentin Schneider
2021-03-05 17:11         ` Qais Yousef
2021-03-10 14:44         ` Qais Yousef
2021-03-05 16:48       ` Qais Yousef
2020-10-23 10:12 ` [PATCH v4 16/19] sched/proc: Print accurate cpumask vs migrate_disable() Peter Zijlstra
2020-11-11  8:23   ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2020-10-23 10:12 ` [PATCH v4 17/19] sched: Add migrate_disable() tracepoints Peter Zijlstra
2020-10-29 16:27   ` Valentin Schneider
2020-10-29 17:43     ` Peter Zijlstra
2020-10-29 17:56       ` Valentin Schneider
2020-10-29 17:59         ` Peter Zijlstra
2020-10-23 10:12 ` [PATCH v4 18/19] sched: Deny self-issued __set_cpus_allowed_ptr() when migrate_disable() Peter Zijlstra
2020-10-23 10:12 ` [PATCH v4 19/19] sched: Comment affine_move_task() Peter Zijlstra
2020-10-29 16:27   ` Valentin Schneider
2020-10-29 17:44     ` Peter Zijlstra
2020-10-29 19:03 ` [PATCH v4 00/19] sched: Migrate disable support Valentin Schneider
2020-11-09 16:39 ` Daniel Bristot de Oliveira

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