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

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Date:	Mon, 25 Jun 2007 19:27:36 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Nigel Cunningham <nigel@...el.suspend2.net>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Pavel Machek <pavel@....cz>, Uli Luckas <u.luckas@...d.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -mm] PM: Prevent frozen user mode helpers from failing the freezing of tasks

On 06/25, Rafael J. Wysocki wrote:
>
> On Monday, 25 June 2007 12:43, Oleg Nesterov wrote:
> 
> > Second, call_usermodehelper's path should first increment the counter, and only
> > then check usermodehelper_disabled,
> 
> It does this already.

Ah, sorry, I looked at this patch without seeing the underlying code.

BTW, isn't it better to rename new_helper/helper_finished to
helper_lock/helper_unlock ?

> If I understand that correctly, it should suffice to place smp_mb() after
> usermodehelper_disabled = 1; in usermodehelper_pm_callback() and another
> smp_mb() after atomic_inc(&running_helpers); in new_helper().
> 
> Is that correct?

Afaics, yes.

Oleg.

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