linux-kernel - Re: [PATCH -mm] workqueue: debug possible endless loop in cancel_rearming_delayed

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Date:	Thu, 19 Apr 2007 13:07:11 -0400
From:	Chuck Ebbert <cebbert@...hat.com>
To:	Jarek Poplawski <jarkao2@...pl>
CC:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH -mm] workqueue: debug possible endless loop in cancel_rearming_delayed_work

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...

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