linux-kernel - Re: [RFC PATCH 1/2] Fix PF_NOFREEZE and freezeable race

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Date:	Thu, 19 Apr 2007 23:39:29 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	ego@...ibm.com
Cc:	Oleg Nesterov <oleg@...sign.ru>, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, mingo@...e.hu, vatsa@...ibm.com,
	paulmck@...ibm.com, pavel@....cz
Subject: Re: [RFC PATCH 1/2] Fix PF_NOFREEZE and freezeable race

Hi,

On Thursday, 19 April 2007 14:02, Gautham R Shenoy wrote:
> This patch fixes the race pointed out by Oleg Nesterov.
> 
> * Freezer marks a thread as freezeable. 
> * The thread now marks itself PF_NOFREEZE causing it to
>   freeze on calling try_to_freeze(). Thus the task is frozen, even though
>   it doesn't want to.
> * Subsequent thaw_processes() will also fail to thaw the task since it is 
>   marked PF_NOFREEZE.
> 
> Avoid this problem by checking the current task's PF_NOFREEZE status in the 
> refrigerator before marking current as frozen.
> 
> Signed-off-by: Gautham R Shenoy <ego@...ibm.com>

Looks good, although I'm not sure if we don't need to call recalc_sigpending()
for tasks that turn out to be PF_NOFREEZE.

Greetings,
Rafael
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