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From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: mhocko@kernel.org, rientjes@google.com
Cc: akpm@linux-foundation.org, aarcange@redhat.com,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: Multiple oom_reaper BUGs: unmap_page_range racing with exit_mmap
Date: Fri, 8 Dec 2017 00:44:11 +0900	[thread overview]
Message-ID: <201712080044.BID56711.FFVOLMStJOQHOF@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <20171207113548.GG20234@dhcp22.suse.cz>

Michal Hocko wrote:
> David, could you test with this patch please?

Even if this patch solved David's case, you need to update

	 * tsk_is_oom_victim() cannot be set from under us
	 * either because current->mm is already set to NULL
	 * under task_lock before calling mmput and oom_mm is
	 * set not NULL by the OOM killer only if current->mm
	 * is found not NULL while holding the task_lock.

part as well, for it is the explanation of why
tsk_is_oom_victim() test was expected to work.

Also, do we need to do

  set_bit(MMF_OOM_SKIP, &mm->flags);

if mm_is_oom_victim(mm) == false?

exit_mmap() is called means that nobody can reach this mm
except ->signal->oom_mm, and mm_is_oom_victim(mm) == false
means that this mm cannot be reached by ->signal->oom_mm .

Then, I think we do not need to set MMF_OOM_SKIP on this mm
at exit_mmap() if mm_is_oom_victim(mm) == false.

  reply	other threads:[~2017-12-07 15:44 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-12-06  2:43 Multiple oom_reaper BUGs: unmap_page_range racing with exit_mmap David Rientjes
2017-12-06  2:58 ` David Rientjes
     [not found]   ` <201712060328.vB63SrDK069830@www262.sakura.ne.jp>
2017-12-06  7:48     ` David Rientjes
2017-12-06  9:00       ` Michal Hocko
     [not found]         ` <201712070720.vB77KlBQ009754@www262.sakura.ne.jp>
2017-12-07  8:28           ` Michal Hocko
2017-12-07  8:44             ` Michal Hocko
2017-12-07 11:00             ` Tetsuo Handa
2017-12-07 21:22             ` David Rientjes
2017-12-08  7:50               ` Michal Hocko
2017-12-06 11:37       ` Tetsuo Handa
2017-12-06  8:50     ` Michal Hocko
2017-12-06  8:31 ` Michal Hocko
2017-12-07 11:35 ` Michal Hocko
2017-12-07 15:44   ` Tetsuo Handa [this message]
2017-12-07 16:30     ` Michal Hocko
2017-12-07 21:55       ` David Rientjes
2017-12-08  9:26         ` David Rientjes
2017-12-08 11:27           ` Michal Hocko
2017-12-08 10:11       ` Tetsuo Handa

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