linux-kernel - Re: Q: down_killable() is racy? or schedule() is not right?

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Message-ID: <20080609114316.GB5028@elte.hu>
Date:	Mon, 9 Jun 2008 13:43:16 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Dmitry Adamushko <dmitry.adamushko@...il.com>
Cc:	Oleg Nesterov <oleg@...sign.ru>, Matthew Wilcox <matthew@....cx>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org
Subject: Re: Q: down_killable() is racy? or schedule() is not right?


* Dmitry Adamushko <dmitry.adamushko@...il.com> wrote:

> > This looks racy. If SIGKILL comes in the WINDOW above, the event is 
> > lost. The task will wait for up() or timeout with the fatal signal 
> > pending, and it is not possible to wakeup it via kill() again.
> >
> > This is easy to fix, but I wonder if we should change schedule() 
> > instead.
> 
> [ for what it's worth ] I think, you are definitely right here.
> 
> The schedule() would be the right place to fix it. At the very least, 
> because otherwise callers are obliged to always check for 
> fatal_signal_pending(task) before scheduling with state == 
> TASK_KILLABLE. e.g. schedule_timeout_killable().
> 
> Not very nice, IMHO.

i guess we should fix this in schedule() - is there a patch i could try?

	Ingo
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