Groups > linux.kernel > #1261943

Re: timer code oops when calling mod_delayed_work

From	Tejun Heo <tj@kernel.org>
Newsgroups	linux.kernel
Subject	Re: timer code oops when calling mod_delayed_work
Date	2015-11-04 00:00 +0100
Message-ID	<qqSIz-vE-19@gated-at.bofh.it> (permalink)
References	(5 earlier) <qpMlP-890-7@gated-at.bofh.it> <qqth7-VK-7@gated-at.bofh.it> <qqtqP-10k-35@gated-at.bofh.it> <qqyJQ-4pO-21@gated-at.bofh.it> <qqO2e-5XS-1@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Hello, Jeff.

On Tue, Nov 03, 2015 at 12:55:04PM -0500, Jeff Layton wrote:
> > Ok, I built a kernel with that patch reverted and that seems to fix the
> > problem.
> > 
> > Looking at the patch, I guess the main difference is that we're no
> > longer using add_timer for unbound workqueue tasks. That said, we
> > should have possession of the PENDING bit before calling add_timer_on.
> > 
> > So...I'm a little stumped. Any thoughts as to where the race could be?
> 
> Ok, I've been able to reproduce this with a small module that I wrote
> as a reproducer:

I think I know what's going on.  Looks like a bug in timer code when
timers are queued on a different cpu than before.  Will experiment
with it a bit and report back.

Thanks.

-- 
tejun
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Thread

Re: timer code oops when calling mod_delayed_work Tejun Heo <tj@kernel.org> - 2015-10-31 22:40 +0100
  Re: timer code oops when calling mod_delayed_work Jeff Layton <jlayton@poochiereds.net> - 2015-10-31 23:00 +0100
    Re: timer code oops when calling mod_delayed_work Chris Worley <chris.worley@primarydata.com> - 2015-11-02 20:50 +0100
      Re: timer code oops when calling mod_delayed_work Jeff Layton <jlayton@poochiereds.net> - 2015-11-02 21:00 +0100
        Re: timer code oops when calling mod_delayed_work Jeff Layton <jlayton@poochiereds.net> - 2015-11-03 02:40 +0100
          Re: timer code oops when calling mod_delayed_work Jeff Layton <jlayton@poochiereds.net> - 2015-11-03 19:00 +0100
            Re: timer code oops when calling mod_delayed_work Tejun Heo <tj@kernel.org> - 2015-11-04 00:00 +0100
              Re: timer code oops when calling mod_delayed_work Tejun Heo <tj@kernel.org> - 2015-11-04 01:10 +0100
                Re: timer code oops when calling mod_delayed_work Jeff Layton <jlayton@poochiereds.net> - 2015-11-04 12:50 +0100
                [PATCH] timer: add_timer_on() should perform proper migration Tejun Heo <tj@kernel.org> - 2015-11-04 18:20 +0100
                [tip:timers/urgent] timers:   Use proper base migration in add_timer_on() tip-bot for Tejun Heo <tipbot@zytor.com> - 2015-11-04 20:30 +0100
                Re: [PATCH] timer: add_timer_on() should perform proper migration Thomas Gleixner <tglx@linutronix.de> - 2015-11-04 20:40 +0100
                Re: [PATCH] timer: add_timer_on() should perform proper migration Tejun Heo <tj@kernel.org> - 2015-11-04 20:50 +0100

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