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From: Tejun Heo <tj@kernel.org>
To: Jeff Layton <jlayton@poochiereds.net>
Cc: Chris Worley <chris.worley@primarydata.com>,
	linux-kernel@vger.kernel.org, bfields@fieldses.org,
	Michael Skralivetsky <michael.skralivetsky@primarydata.com>,
	Trond Myklebust <trond.myklebust@primarydata.com>,
	Shaohua Li <shli@fb.com>
Subject: Re: timer code oops when calling mod_delayed_work
Date: Tue, 3 Nov 2015 17:54:05 -0500	[thread overview]
Message-ID: <20151103225405.GG5749@mtj.duckdns.org> (raw)
In-Reply-To: <20151103125504.6649138f@tlielax.poochiereds.net>

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

  reply	other threads:[~2015-11-03 22:54 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-10-29 14:31 timer code oops when calling mod_delayed_work Jeff Layton
2015-10-29 17:58 ` Jeff Layton
2015-10-31  2:00   ` Tejun Heo
2015-10-31 11:34     ` Jeff Layton
2015-10-31 21:31       ` Tejun Heo
2015-10-31 21:54         ` Jeff Layton
2015-11-02 19:48           ` Chris Worley
2015-11-02 19:56             ` Jeff Layton
2015-11-03  1:33               ` Jeff Layton
2015-11-03 17:55                 ` Jeff Layton
2015-11-03 22:54                   ` Tejun Heo [this message]
2015-11-04  0:06                     ` Tejun Heo
2015-11-04 11:48                       ` Jeff Layton
2015-11-04 17:15                         ` [PATCH] timer: add_timer_on() should perform proper migration Tejun Heo
2015-11-04 19:27                           ` [tip:timers/urgent] timers: Use proper base migration in add_timer_on() tip-bot for Tejun Heo
2015-11-04 19:35                           ` [PATCH] timer: add_timer_on() should perform proper migration Thomas Gleixner
2015-11-04 19:43                             ` Tejun Heo

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