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

From Michal Hocko <mhocko@kernel.org>
Newsgroups linux.kernel
Subject Re: [PATCH] mm,oom: Exclude TIF_MEMDIE processes from candidates.
Date 2016-01-07 16:00 +0100
Message-ID <qOkcH-137-25@gated-at.bofh.it> (permalink)
References <qL2YH-1hA-9@gated-at.bofh.it> <qOeTE-65o-23@gated-at.bofh.it> <qOiXf-hG-5@gated-at.bofh.it>
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On Thu 07-01-16 22:31:32, Tetsuo Handa wrote:
[...]
> 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.

Hmm. Any task is allowed to set its oom_score_adj that way and I
guess we should really make sure that at least sysrq+f will make some
progress. This is what I would do. Again I think this is worth a
separate patch. Unless there are any objections I will roll out what I
have and post 3 separate patches.
---
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 45e51ad2f7cf..ee34a51bd65a 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -333,6 +333,14 @@ static struct task_struct *select_bad_process(struct oom_control *oc,
 		if (points == chosen_points && thread_group_leader(chosen))
 			continue;
 
+		/*
+		 * If the current major task is already ooom killed and this
+		 * is sysrq+f request then we rather choose somebody else
+		 * because the current oom victim might be stuck.
+		 */
+		if (is_sysrq_oom(sc) && test_tsk_thread_flag(p, TIF_MEMDIE))
+			continue;
+
 		chosen = p;
 		chosen_points = points;
 	}
-- 
Michal Hocko
SUSE Labs
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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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