linux-kernel - Re: [PATCH 10/10] mm, oom: hide mm which is shared with kthread or global init

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Date:	Thu, 16 Jun 2016 22:36:09 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	mhocko@...nel.org
Cc:	linux-mm@...ck.org, rientjes@...gle.com, oleg@...hat.com,
	vdavydov@...allels.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, penguin-kernel@...ove.SAKURA.ne.jp
Subject: Re: [PATCH 10/10] mm, oom: hide mm which is shared with kthread or global init

Tetsuo Handa wrote:
> But this is not safe for CONFIG_MMU=y kernels as well.
> can_oom_reap == false means that oom_reap_task() will not be called.
> It is possible that the TIF_MEMDIE thread falls into
> 
>    atomic_read(&task->signal->oom_victims) > 0 && find_lock_task_mm(task) == NULL
> 
> situation. We are still risking OOM livelock. We must somehow clear (or ignore)
> TIF_MEMDIE even if oom_reap_task() is not called.

Oops. mmput() from exit_mm() does not block in that case. So, we won't livelock here.

> 
> Can't we apply http://lkml.kernel.org/r/201606102323.BCC73478.FtOJHFQMSVFLOO@I-love.SAKURA.ne.jp now?
>