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From: Joseph Qi <joseph.qi@linux.alibaba.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	linux-kernel@vger.kernel.org,
	Johannes Weiner <hannes@cmpxchg.org>,
	Suren Baghdasaryan <surenb@google.com>,
	Jason Xing <kerneljasonxing@linux.alibaba.com>,
	Caspar Zhang <caspar@linux.alibaba.com>
Subject: Re: [PATCH v3] psi: get poll_work to run when calling poll syscall next time
Date: Fri, 23 Aug 2019 08:53:09 +0800	[thread overview]
Message-ID: <8a093924-98ea-de13-554d-5f5b6ee63536@linux.alibaba.com> (raw)
In-Reply-To: <20190822152107.adc0d4cd374fcc3eb8e148a9@linux-foundation.org>



On 19/8/23 06:21, Andrew Morton wrote:
> On Wed, 21 Aug 2019 11:26:25 +0800 Joseph Qi <joseph.qi@linux.alibaba.com> wrote:
> 
>> Only when calling the poll syscall the first time can user
>> receive POLLPRI correctly. After that, user always fails to
>> acquire the event signal.
>>
>> Reproduce case:
>> 1. Get the monitor code in Documentation/accounting/psi.txt
>> 2. Run it, and wait for the event triggered.
>> 3. Kill and restart the process.
>>
>> The question is why we can end up with poll_scheduled = 1 but the work
>> not running (which would reset it to 0). And the answer is because the
>> scheduling side sees group->poll_kworker under RCU protection and then
>> schedules it, but here we cancel the work and destroy the worker. The
>> cancel needs to pair with resetting the poll_scheduled flag.
> 
> Should this be backported into -stable kernels?
> 
Sorry for missing that, should I resend it with cc stable tag?

Thanks,
Joseph

  parent reply	other threads:[~2019-08-23  0:53 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-21  3:26 Joseph Qi
2019-08-22 22:21 ` Andrew Morton
2019-08-22 23:11   ` Suren Baghdasaryan
2019-08-22 23:17     ` Andrew Morton
2019-08-22 23:21       ` Suren Baghdasaryan
2019-08-23  0:53   ` Joseph Qi [this message]
2019-08-24 20:51     ` Andrew Morton

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