linux-kernel - Re: [RFC 1/4] OOM, PM: Do not miss OOM killed frozen tasks

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Date:	Fri, 14 Nov 2014 12:55:34 -0500
From:	Tejun Heo <tj@...nel.org>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
	linux-pm@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	"\\\"Rafael J. Wysocki\\\"" <rjw@...ysocki.net>,
	David Rientjes <rientjes@...gle.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Cong Wang <xiyou.wangcong@...il.com>
Subject: Re: [RFC 1/4] OOM, PM: Do not miss OOM killed frozen tasks

Hello, Michal.

On Wed, Nov 12, 2014 at 07:58:49PM +0100, Michal Hocko wrote:
> Also change the return value semantic as the current one is little bit
> awkward. There is just one caller (try_to_freeze_tasks) which checks
> the return value and it is only interested whether the request was
> successful or the task blocks the freezing progress. It is natural to
> reflect the success by true rather than false.

I don't know about this.  It's also customary to return %true when
further action needs to be taken.  I don't think either is
particularly wrong but the flip seems gratuitous.

>  bool freeze_task(struct task_struct *p)
>  {
> @@ -129,12 +130,20 @@ bool freeze_task(struct task_struct *p)
>  	 * normally.
>  	 */
>  	if (freezer_should_skip(p))
> +		return true;
> +
> +	/*
> +	 * Do not check freezing state or attempt to freeze a task
> +	 * which has been killed by OOM killer. We are just waiting
> +	 * for the task to wake up and die.

Maybe saying sth like "consider the task freezing as ...." is a
clearer way to put it?

> +	 */
> +	if (!test_tsk_thread_flag(p, TIF_MEMDIE))
>  		return false;

Thanks.

-- 
tejun
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