linux-kernel - [BUGFIX][PATCH] memcg fix wake up in oom wait queue

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Message-Id: <20100604115820.d7ec1008.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Fri, 4 Jun 2010 11:58:20 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>
Subject: [BUGFIX][PATCH] memcg fix wake up in oom wait queue

Tested on mmotm-2010-06-03 and works well.
==
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

OOM-waitqueue should be waken up when oom_disable is canceled.
This is a fix for
 memcg-oom-kill-disable-and-oom-status.patch

How to test:
 Create a cgroup A...
 1. set memory.limit and memory.memsw.limit to be small value
 2. echo 1 > /cgroup/A/memory.oom_control, this disables oom-kill.
 3. run a program which must cause OOM.

A program executed in 3 will sleep by oom_waiqueue in memcg.
Then, how to wake it up is problem.

 1. echo 0 > /cgroup/A/memory.oom_control (enable OOM-killer)
 2. echo big mem > /cgroup/A/memory.memsw.limit_in_bytes(allow more swap)
etc..

Without the patch, a task in slept can not be waken up.

Changelog: 2010/06/04
Rebased onto mmotm-2010-06-03-16-36

Acked-by: Acked-by: Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
---
 mm/memcontrol.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Index: mmotm-2.6.34-Jun6/mm/memcontrol.c
===================================================================
--- mmotm-2.6.34-Jun6.orig/mm/memcontrol.c
+++ mmotm-2.6.34-Jun6/mm/memcontrol.c
@@ -1370,7 +1370,7 @@ static void memcg_wakeup_oom(struct mem_
 
 static void memcg_oom_recover(struct mem_cgroup *mem)
 {
-	if (mem->oom_kill_disable && atomic_read(&mem->oom_lock))
+	if (atomic_read(&mem->oom_lock))
 		memcg_wakeup_oom(mem);
 }
 
@@ -3781,6 +3781,8 @@ static int mem_cgroup_oom_control_write(
 		return -EINVAL;
 	}
 	mem->oom_kill_disable = val;
+	if (!val)
+		memcg_oom_recover(mem);
 	cgroup_unlock();
 	return 0;
 }

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