Re: [PATCH] workqueue: fix rebind bound workers warning

From	Wanpeng Li <kernellwp@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] workqueue: fix rebind bound workers warning
Date	2016-05-11 01:30 +0200
Message-ID	<rxpgd-4fX-3@gated-at.bofh.it> (permalink)
References	<rvgAr-6ZQ-5@gated-at.bofh.it> <rwWQW-1tE-37@gated-at.bofh.it> <rx1nC-5F3-37@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Hi Tejun,
2016-05-10 5:50 GMT+08:00 Wanpeng Li <kernellwp@gmail.com>:
> Cc Thomas, the new state machine author,
> 2016-05-10 1:00 GMT+08:00 Tejun Heo <tj@kernel.org>:
>> Hello,
>>
>> On Thu, May 05, 2016 at 09:41:31AM +0800, Wanpeng Li wrote:
>>> The boot CPU handles housekeeping duty(unbound timers, workqueues,
>>> timekeeping, ...) on behalf of full dynticks CPUs. It must remain
>>> online when nohz full is enabled. There is a priority set to every
>>> notifier_blocks:
>>>
>>> workqueue_cpu_up > tick_nohz_cpu_down > workqueue_cpu_down
>>>
>>> So tick_nohz_cpu_down callback failed when down prepare cpu 0, and
>>> notifier_blocks behind tick_nohz_cpu_down will not be called any
>>> more, which leads to workers are actually not unbound. Then hotplug
>>> state machine will fallback to undo and online cpu 0 again. Workers
>>> will be rebound unconditionally even if they are not unbound and
>>> trigger the warning in this progress.
>>
>> I'm a bit confused.  Are you saying that the hotplug statemachine may
>> invoke CPU_DOWN_FAILED w/o preceding CPU_DOWN on the same callback?
>
> I think so. CPU_DOWN_FAILED is detected in the process of CPU_DOWN_PREPARE

So any plan to apply? :-)

Regards,
Wanpeng Li

Thread

[PATCH] workqueue: fix rebind bound workers warning Wanpeng Li <kernellwp@gmail.com> - 2016-05-05 03:50 +0200
  Re: [PATCH] workqueue: fix rebind bound workers warning Wanpeng Li <kernellwp@gmail.com> - 2016-05-09 09:30 +0200
  Re: [PATCH] workqueue: fix rebind bound workers warning Tejun Heo <tj@kernel.org> - 2016-05-09 19:10 +0200
    Re: [PATCH] workqueue: fix rebind bound workers warning Wanpeng Li <kernellwp@gmail.com> - 2016-05-10 00:00 +0200
      Re: [PATCH] workqueue: fix rebind bound workers warning Wanpeng Li <kernellwp@gmail.com> - 2016-05-10 00:20 +0200
      Re: [PATCH] workqueue: fix rebind bound workers warning Wanpeng Li <kernellwp@gmail.com> - 2016-05-11 01:30 +0200
        Re: [PATCH] workqueue: fix rebind bound workers warning Thomas Gleixner <tglx@linutronix.de> - 2016-05-11 09:40 +0200
          Re: [PATCH] workqueue: fix rebind bound workers warning Wanpeng Li <kernellwp@gmail.com> - 2016-05-11 10:10 +0200
            Re: [PATCH] workqueue: fix rebind bound workers warning Thomas Gleixner <tglx@linutronix.de> - 2016-05-11 12:10 +0200
              Re: [PATCH] workqueue: fix rebind bound workers warning Wanpeng Li <kernellwp@gmail.com> - 2016-05-11 12:30 +0200

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