linux-kernel - [PATCH] mm/oom_kill.c: don't kill TASK

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Message-Id: <1442512783-14719-1-git-send-email-kwalker@redhat.com>
Date:	Thu, 17 Sep 2015 13:59:43 -0400
From:	Kyle Walker <kwalker@...hat.com>
To:	akpm@...ux-foundation.org
Cc:	mhocko@...e.cz, rientjes@...gle.com, hannes@...xchg.org,
	vdavydov@...allels.com, oleg@...hat.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Kyle Walker <kwalker@...hat.com>
Subject: [PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks

Currently, the oom killer will attempt to kill a process that is in
TASK_UNINTERRUPTIBLE state. For tasks in this state for an exceptional
period of time, such as processes writing to a frozen filesystem during
a lengthy backup operation, this can result in a deadlock condition as
related processes memory access will stall within the page fault
handler.

Within oom_unkillable_task(), check for processes in
TASK_UNINTERRUPTIBLE (TASK_KILLABLE omitted). The oom killer will
move on to another task.

Signed-off-by: Kyle Walker <kwalker@...hat.com>
---
 mm/oom_kill.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 1ecc0bc..66f03f8 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -131,6 +131,10 @@ static bool oom_unkillable_task(struct task_struct *p,
 	if (memcg && !task_in_mem_cgroup(p, memcg))
 		return true;
 
+	/* Uninterruptible tasks should not be killed unless in TASK_WAKEKILL */
+	if (p->state == TASK_UNINTERRUPTIBLE)
+		return true;
+
 	/* p may not have freeable memory in nodemask */
 	if (!has_intersects_mems_allowed(p, nodemask))
 		return true;
-- 
2.4.3

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