From: Corey Minyard <minyard@acm.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
tglx@linutronix.de, Steven Rostedt <rostedt@goodmis.org>,
Corey Minyard <cminyard@mvista.com>
Subject: Re: [PATCH RT v2] Fix a lockup in wait_for_completion() and friends
Date: Fri, 10 May 2019 07:08:24 -0500 [thread overview]
Message-ID: <20190510120824.GL16145@minyard.net> (raw)
In-Reply-To: <20190510103318.6cieoifz27eph4n5@linutronix.de>
On Fri, May 10, 2019 at 12:33:18PM +0200, Sebastian Andrzej Siewior wrote:
> On 2019-05-09 14:33:20 [-0500], minyard@acm.org wrote:
> > From: Corey Minyard <cminyard@mvista.com>
> >
> > The function call do_wait_for_common() has a race condition that
> > can result in lockups waiting for completions. Adding the thread
> > to (and removing the thread from) the wait queue for the completion
> > is done outside the do loop in that function. However, if the thread
> > is woken up, the swake_up_locked() function will delete the entry
> > from the wait queue. If that happens and another thread sneaks
> > in and decrements the done count in the completion to zero, the
> > loop will go around again, but the thread will no longer be in the
> > wait queue, so there is no way to wake it up.
>
> applied, thank you.
>
> Sebastian
Thanks a bunch. Do I need to do anything for backports? I'm pretty
sure this goes back to 4.4.
-corey
next prev parent reply other threads:[~2019-05-10 12:08 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-09 19:33 [PATCH RT v2] Fix a lockup in wait_for_completion() and friends minyard
2019-05-09 19:51 ` Steven Rostedt
2019-05-10 10:33 ` Sebastian Andrzej Siewior
2019-05-10 12:08 ` Corey Minyard [this message]
2019-05-10 12:26 ` Sebastian Andrzej Siewior
2019-06-29 1:49 ` Steven Rostedt
2019-07-01 19:09 ` Corey Minyard
[not found] ` <20190701161840.1a53c9e4@gandalf.local.home>
2019-07-01 20:43 ` Corey Minyard
2019-07-01 21:06 ` Steven Rostedt
2019-07-01 21:13 ` Steven Rostedt
2019-07-01 21:28 ` Steven Rostedt
2019-07-01 21:34 ` Corey Minyard
2019-07-02 7:04 ` Kurt Kanzenbach
2019-07-02 8:35 ` Sebastian Andrzej Siewior
2019-07-02 11:40 ` Corey Minyard
2019-07-02 11:53 ` Sebastian Andrzej Siewior
-- strict thread matches above, loose matches on Subject: below --
2019-05-08 20:57 [PATCH " minyard
2019-05-09 16:19 ` [PATCH RT " Sebastian Andrzej Siewior
2019-05-09 17:46 ` Corey Minyard
2019-05-14 8:43 ` Peter Zijlstra
2019-05-14 9:12 ` Sebastian Andrzej Siewior
2019-05-14 11:35 ` Peter Zijlstra
2019-05-14 15:25 ` Sebastian Andrzej Siewior
2019-05-14 12:13 ` Corey Minyard
2019-05-14 15:36 ` Sebastian Andrzej Siewior
2019-05-15 16:22 ` Corey Minyard
2019-06-26 10:35 ` Peter Zijlstra
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