linux-kernel - [PATCH v2] mm,oom: exclude oom_task_origin processes if they are OOM-unkillable.

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Message-Id: <1455719460-7690-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp>
Date:	Wed, 17 Feb 2016 23:31:00 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	mhocko@...nel.org, akpm@...ux-foundation.org
Cc:	rientjes@...gle.com, mgorman@...e.de, oleg@...hat.com,
	torvalds@...ux-foundation.org, hughd@...gle.com, andrea@...nel.org,
	riel@...hat.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Subject: [PATCH v2] mm,oom: exclude oom_task_origin processes if they are OOM-unkillable.

oom_scan_process_thread() returns OOM_SCAN_SELECT when there is a
thread which returns oom_task_origin() == true. But it is possible
that such thread is marked as OOM-unkillable. In that case, the OOM
killer must not select such process.

Since it is meaningless to return OOM_SCAN_OK for OOM-unkillable
process because subsequent oom_badness() call will return 0, this
patch changes oom_scan_process_thread to return OOM_SCAN_CONTINUE
if that process is marked as OOM-unkillable (regardless of
oom_task_origin()).

Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Suggested-by: Michal Hocko <mhocko@...nel.org>
---
 mm/oom_kill.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 7653055..cf87153 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -282,7 +282,7 @@ enum oom_scan_t oom_scan_process_thread(struct oom_control *oc,
 		if (!is_sysrq_oom(oc))
 			return OOM_SCAN_ABORT;
 	}
-	if (!task->mm)
+	if (!task->mm || task->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
 		return OOM_SCAN_CONTINUE;

 	/*
-- 
1.8.3.1