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From: Chuck Ebbert <cebbert@redhat.com>
To: Jarek Poplawski <jarkao2@o2.pl>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>
Subject: Re: [PATCH -mm] workqueue: debug possible endless loop in cancel_rearming_delayed_work
Date: Thu, 19 Apr 2007 13:07:11 -0400	[thread overview]
Message-ID: <4627A1BF.8080406@redhat.com> (raw)
In-Reply-To: <20070419065404.GB1782@ff.dom.local>

Jarek Poplawski wrote:
> Hi,
> 
> IMHO cancel_rearming_delayed_work is dangerous place:
> 
> - it assumes a work function always rearms (with no exception),
> which probably isn't explained enough now (but anyway should
> be checked in such loops);
> 
> - probably possible (theoretical) scenario: a few work
> functions rearm themselves with very short, equal times;
> before flush_workqueue ends, their timers are already
> fired, so cancel_delayed_work has nothing to do.
> 
> Maybe this patch could check, if I'm not dreaming...
> 
> PS: of course the counter value below is a question of taste

Okay, an easy test for it: insmod netconsole ; rmmod netconsole

In 2.6.20.x it loops forever and cancel_rearming_delayed_work()
is part of the trace...


  parent reply	other threads:[~2007-04-19 17:13 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-04-19  6:54 [PATCH -mm] workqueue: debug possible endless loop in cancel_rearming_delayed_work Jarek Poplawski
2007-04-19  7:32 ` Ingo Molnar
2007-04-19  8:28   ` Jarek Poplawski
2007-04-19 14:48   ` David Chinner
2007-04-19 14:46 ` David Chinner
2007-04-20  8:13   ` Jarek Poplawski
2007-04-20  8:53     ` David Chinner
2007-04-20 10:21       ` Jarek Poplawski
2007-04-20 11:01         ` David Chinner
2007-04-20 12:12           ` [PATCH] workqueue: cancel_rearming_delayed_work/workqueue usage warning Jarek Poplawski
2007-04-20 17:23             ` Oleg Nesterov
2007-04-23  9:41               ` Jarek Poplawski
2007-04-19 17:07 ` Chuck Ebbert [this message]
2007-04-20  7:14   ` [PATCH -mm] workqueue: debug possible endless loop in cancel_rearming_delayed_work Jarek Poplawski
  -- strict thread matches above, loose matches on Subject: below --
2007-04-20 11:09 Jarek Poplawski

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