linux-kernel - Re: Multiple oom_reaper BUGs: unmap_page_range racing with exit

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Message-ID: <20171206090019.GE16386@dhcp22.suse.cz>
Date:   Wed, 6 Dec 2017 10:00:19 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: Multiple oom_reaper BUGs: unmap_page_range racing with exit_mmap

On Tue 05-12-17 23:48:21, David Rientjes wrote:
[...]
> I think this argues to do MMF_REAPING-style behavior at the beginning of 
> exit_mmap() and avoid reaping all together once we have reached that 
> point.  There are no more users of the mm and we are in the process of 
> tearing it down, I'm not sure that the oom reaper should be in the 
> business with trying to interfere with that.  Or are there actual bug 
> reports where an oom victim gets wedged while in exit_mmap() prior to 
> releasing its memory?

Something like that seem to work indeed. But we should better understand
what is going on here before adding new oom reaper specific kludges. So
let's focus on getting more information from your crashes first.
-- 
Michal Hocko
SUSE Labs