linux-kernel - Re: [PATCH -mm 2/7] Freezer: Close theoretical race between refrigerator and thaw

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Message-ID: <20070301163907.GA4710@ucw.cz>
Date:	Thu, 1 Mar 2007 16:39:08 +0000
From:	Pavel Machek <pavel@....cz>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Andrew Morton <akpm@...l.org>, LKML <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...sign.ru>,
	Aneesh Kumar <aneesh.kumar@...il.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Gautham R Shenoy <ego@...ibm.com>
Subject: Re: [PATCH -mm 2/7] Freezer: Close theoretical race between refrigerator and thaw_tasks

On Thu 2007-03-01 16:08:12, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rjw@...k.pl>
> 
> If the freezing of tasks fails and a task is preempted in refrigerator() before
> calling frozen_process(), then thaw_tasks() may run before this task is frozen.
> In that case the task will freeze and no one will thaw it.
> 
> To fix this race we can call freezing(current) in refrigerator() along with
> frozen_process(current) under the task_lock() which also should be taken in
> the error path of try_to_freeze_tasks() as well as in thaw_process().  Moreover,
> if thaw_process() additionally clears TIF_FREEZE for tasks that are not frozen,
> we can be sure that all tasks are thawed and there are no pending "freeze"
> requests after thaw_tasks() has run.
> 
> Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>

ack.
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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