linux-kernel - Re: [Patch v3 1/2] freezer: check OOM kill while being frozen

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Message-ID: <20140903154219.GA30011@mtj.dyndns.org>
Date:	Wed, 3 Sep 2014 11:42:19 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Cong Wang <xiyou.wangcong@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	David Rientjes <rientjes@...gle.com>,
	Michal Hocko <mhocko@...e.cz>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [Patch v3 1/2] freezer: check OOM kill while being frozen

Hello, Cong.

On Tue, Sep 02, 2014 at 03:52:40PM -0700, Cong Wang wrote:
> diff --git a/kernel/freezer.c b/kernel/freezer.c
> index 33cbcb0..b06a059 100644
> --- a/kernel/freezer.c
> +++ b/kernel/freezer.c
> @@ -56,7 +56,8 @@ static bool should_thaw_current(bool check_kthr_stop)
>  {
>         if (!freezing(current) ||
>             (check_kthr_stop && kthread_should_stop()) ||
> -           test_thread_flag(TIF_MEMDIE))
> +           /* It might not be safe to check TIF_MEMDIE for pm freeze */
> +           (cgroup_freezing(current) && test_thread_flag(TIF_MEMDIE)))
>                 return true;
>         else
>                 return false;
> 
> Are you happy now, Tejun? :)

Yes, this should be a lot safer.  The function still looks weird to me
tho.

	if (cond)
		return true;
	else
		return false;

is equivalent to

	return cond;

If you're worried that the conditional is too complex and harms
readability you can do

	/* explain cond0 */
	if (cond0)
		return true;

	/* explain cond1 */
	if (cond1)
		return true;

	return false;

Thanks.

-- 
tejun
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