linux-kernel - Re: [PATCH 02/10] freezer: skip waking up tasks with PF_FREEZER

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Message-ID: <20130430171059.GA28944@redhat.com>
Date:	Tue, 30 Apr 2013 19:10:59 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Colin Cross <ccross@...roid.com>
Cc:	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...k.pl>, arve@...roid.com,
	Tejun Heo <tj@...nel.org>, Li Zefan <lizefan@...wei.com>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	containers@...hat.com
Subject: Re: [PATCH 02/10] freezer: skip waking up tasks with
	PF_FREEZER_SKIP set

On 04/29, Colin Cross wrote:
>
> @@ -46,10 +46,10 @@ static int try_to_freeze_tasks(bool user_only)
>  		todo = 0;
>  		read_lock(&tasklist_lock);
>  		do_each_thread(g, p) {
> -			if (p == current || !freeze_task(p))
> +			if (p == current || freezer_should_skip(p))
>  				continue;
>
> -			if (!freezer_should_skip(p))
> +			if (freeze_task(p))
>  				todo++;

What if we race with freezer_count() ?

try_to_freeze_tasks() can wrongly succeed leaving the running task
unfrozen, no?

Oleg.

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