Re: [PATCH] mm,oom: Exclude TIF_MEMDIE processes from candidates.

From	Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Newsgroups	linux.kernel
Subject	Re: [PATCH] mm,oom: Exclude TIF_MEMDIE processes from candidates.
Date	2016-01-07 14:40 +0100
Message-ID	<qOiXf-hG-5@gated-at.bofh.it> (permalink)
References	<qL2YH-1hA-9@gated-at.bofh.it> <qOeTE-65o-23@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Michal Hocko wrote:
> I do not think the placement in find_lock_task_mm is desirable nor
> correct. This function is used in multiple contexts outside of the oom
> proper. It only returns a locked task_struct for a thread that belongs
> to the process.

OK. Andrew, please drop from -mm tree for now.

> What you are seeing is clearly undesirable of course but I believe we
> should handle it at oom_kill_process layer. Blindly selecting a child
> process even when it doesn't sit on some memory or when it has already
> been killed is wrong. The heuristic is clearly too naive and so we
> should touch it rather than compensating it somewhere else. What about
> the following simple approach? It does two things and I will split it
> up if this looks like a desirable approach. Please note I haven't tested
> it because it is more of an idea than a finished thing. What do you think?

I think we need to filter at select_bad_process() and oom_kill_process().

When P has no children, P is chosen and TIF_MEMDIE is set on P. But P can
be chosen forever due to P->signal->oom_score_adj == OOM_SCORE_ADJ_MAX
even if the OOM reaper reclaimed P's mm. We need to ensure that
oom_kill_process() is not called with P if P already has TIF_MEMDIE.

(By the way, we are already assuming the OOM reaper kernel thread is
available. Changing to BUG_ON(IS_ERR(oom_reaper_th)) should be OK. ;-) )
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Thread

Re: [PATCH] mm,oom: Exclude TIF_MEMDIE processes from candidates. Michal Hocko <mhocko@kernel.org> - 2016-01-07 10:20 +0100
  Re: [PATCH] mm,oom: Exclude TIF_MEMDIE processes from candidates. Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-01-07 14:40 +0100
    Re: [PATCH] mm,oom: Exclude TIF_MEMDIE processes from candidates. Michal Hocko <mhocko@kernel.org> - 2016-01-07 16:00 +0100
      Re: [PATCH] mm,oom: Exclude TIF_MEMDIE processes from candidates. Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-01-07 16:40 +0100
        Re: [PATCH] mm,oom: Exclude TIF_MEMDIE processes from candidates. Michal Hocko <mhocko@kernel.org> - 2016-01-11 16:20 +0100
          Re: [PATCH] mm,oom: Exclude TIF_MEMDIE processes from candidates. Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-01-12 12:40 +0100
            Re: [PATCH] mm,oom: Exclude TIF_MEMDIE processes from candidates. Michal Hocko <mhocko@kernel.org> - 2016-01-12 21:00 +0100
              Re: [PATCH] mm,oom: Exclude TIF_MEMDIE processes from candidates. Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-01-13 11:20 +0100
                Re: [PATCH] mm,oom: Exclude TIF_MEMDIE processes from candidates. Michal Hocko <mhocko@kernel.org> - 2016-01-13 16:30 +0100
      Re: [PATCH] mm,oom: Exclude TIF_MEMDIE processes from candidates. Michal Hocko <mhocko@kernel.org> - 2016-01-07 16:50 +0100
        Re: [PATCH v2] mm,oom: Exclude TIF_MEMDIE processes from candidates. Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-01-08 11:20 +0100
          Re: [PATCH v2] mm,oom: Exclude TIF_MEMDIE processes from  candidates. David Rientjes <rientjes@google.com> - 2016-01-13 01:40 +0100
            Re: [PATCH v2] mm,oom: Exclude TIF_MEMDIE processes from candidates. Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-01-13 12:00 +0100
              Re: [PATCH v2] mm,oom: Exclude TIF_MEMDIE processes from  candidates. David Rientjes <rientjes@google.com> - 2016-01-14 02:00 +0100
                Re: [PATCH v2] mm,oom: Exclude TIF_MEMDIE processes from candidates. Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-01-14 11:30 +0100
                Re: [PATCH v2] mm,oom: Exclude TIF_MEMDIE processes from  candidates. David Rientjes <rientjes@google.com> - 2016-01-14 23:00 +0100
                Re: [PATCH v2] mm,oom: Exclude TIF_MEMDIE processes from candidates. Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2016-01-14 23:30 +0100

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