linux-kernel - Re: [Patch] freezer: check OOM kill signal while being frozen

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Date:	Mon, 11 Aug 2014 17:34:39 -0700
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	David Rientjes <rientjes@...gle.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>, Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [Patch] freezer: check OOM kill signal while being frozen

On Mon, Aug 11, 2014 at 6:18 AM, Michal Hocko <mhocko@...e.cz> wrote:
>
> OK, so the system/memcg is still OOM and a new allocation/charge
> would trigger killer again, right? Then oom_scan_process_thread sees
> TIF_MEMDIE frozen task and thaw it so it can go away and die. So this
> shouldn't be a permanent state. Or am I missing something?
>

Good point!

Reading the code again, I think David's commit (f660daac) doesn't
work any more, __thaw_task() just checks if it's frozen and then wakes
it up, but the frozen task, after waking up, will check if it's freezing() and
continue to freeze itself if so. __thaw_task() can't make freezing() return
false since it doesn't change any of these conditions, especially
cgroup_freezing().

This reminds me I should revert that code in oom_killer, checking
TIF_MEMDIE in __refrigerator() is more correct and clear.

I will update my patch.

Thanks!
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