From mboxrd@z Thu Jan  1 00:00:00 1970
From: Oleg Nesterov <oleg@tv-sign.ru>
Subject: Re: [RFC][PATCH -mm 2/2] Freezer: Use wait queue instead
	of busy looping
Date: Wed, 25 Jul 2007 17:29:17 +0400
Message-ID: <20070725132917.GA242@tv-sign.ru>
References: <200707251401.48340.rjw@sisk.pl> <200707251409.40592.rjw@sisk.pl>
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To: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: pm list <linux-pm@lists.linux-foundation.org>, Nigel Cunningham <nigel@nigel.suspend2.net>, Pavel Machek <pavel@ucw.cz>
List-Id: linux-pm@vger.kernel.org

On 07/25, Rafael J. Wysocki wrote:
>
>  void refrigerator(void)
>  {
> @@ -50,6 +73,9 @@ void refrigerator(void)
>  	   processes around? */
>  	long save;
>
> +	refrigerator_called = 1;
> +	wake_up(&refrigerator_waitq);
> +

This is a bit racy. Unless I missed something, the task should not set
refrigerator_called == 1 until it has PF_FROZEN.

Otherwise, try_to_freeze_tasks() can set refrigerator_called == 0 after
refrigerator() sets it == 1, the the main loop notices this unfrozen task,
and goes to sleep.

(I must admit, I agree with Pavel on that patch).

Oleg.