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Date: Tue, 24 Apr 2018 15:25:51 -0700 (PDT)
From: David Rientjes <rientjes@google.com>
Subject: Re: [patch v2] mm, oom: fix concurrent munlock and oom reaper
 unmap
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To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: mhocko@kernel.org, akpm@linux-foundation.org, aarcange@redhat.com, guro@fb.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org

On Wed, 25 Apr 2018, Tetsuo Handa wrote:

> > One of the reasons that I extracted __oom_reap_task_mm() out of the new 
> > oom_reap_task_mm() is to avoid the checks that would be unnecessary when 
> > called from exit_mmap().  In this case, we can ignore the 
> > mm_has_blockable_invalidate_notifiers() check because exit_mmap() has 
> > already done mmu_notifier_release().  So I don't think there's a concern 
> > about __oom_reap_task_mm() blocking while holding oom_lock.  Unless you 
> > are referring to something else?
> 
> Oh, mmu_notifier_release() made mm_has_blockable_invalidate_notifiers() == false. OK.
> 
> But I want comments why it is safe; I will probably miss that dependency
> when we move that code next time.
> 

Ok, makes sense.  I'll send a v3 to update the comment.