linux-kernel - Re: [RFC][PATCH -mm] PM: Prevent frozen user mode helpers from failing the freezing of tasks

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Date:	Wed, 20 Jun 2007 11:14:35 +0200
From:	Uli Luckas <u.luckas@...d.de>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	LKML <linux-kernel@...r.kernel.org>, Pavel Machek <pavel@....cz>,
	pm list <linux-pm@...ts.linux-foundation.org>
Subject: Re: [RFC][PATCH -mm] PM: Prevent frozen user mode helpers from failing the freezing of tasks

On Monday, 18. June 2007, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rjw@...k.pl>
>
> At present, if a user mode helper is running while
> usermodehelper_pm_callback() is executed, the helper may be frozen and the
> completion in
> call_usermodehelper_exec() won't be completed until user space processes
> are thawed.  As a result, the freezing of kernel threads may fail, which is
> not desirable.
>
> Prevent this from happening by introducing a counter of running user mode
> helpers and allowing usermodehelper_pm_callback() to succeed for
> action = PM_HIBERNATION_PREPARE or action = PM_SUSPEND_PREPARE only if
> there are no helpers running.  [Namely, usermodehelper_pm_callback() waits
> for at most RUNNING_HELPERS_TIMEOUT for the number of running helpers to
> become zero and fails if that doesn't happen.]
>
> Special thanks to Uli Luckas <u.luckas@...d.de> for reviewing the previous
> versions of this patch and for very useful comments.
>

Acked-by: Uli Luckas <u.luckas@...d.de>

Regards,
Uli

-- 

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Uli Luckas
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