From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx207.postini.com [74.125.245.207]) by kanga.kvack.org (Postfix) with SMTP id 17C5C6B012A for ; Thu, 4 Oct 2012 14:09:29 -0400 (EDT) From: Johannes Weiner Subject: [patch 1/2] mm: memcontrol: handle potential crash when rmap races with task exit Date: Thu, 4 Oct 2012 14:09:16 -0400 Message-Id: <1349374157-20604-2-git-send-email-hannes@cmpxchg.org> In-Reply-To: <1349374157-20604-1-git-send-email-hannes@cmpxchg.org> References: <1349374157-20604-1-git-send-email-hannes@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Michal Hocko , Konstantin Khlebnikov , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org page_referenced() counts only references of mm's that are associated with the memcg hierarchy that is being reclaimed. However, if it races with the owner of the mm exiting, mm->owner may be NULL. Don't crash, just ignore the reference. Signed-off-by: Johannes Weiner Cc: stable@kernel.org [3.5] --- include/linux/memcontrol.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 8d9489f..8686294 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -91,7 +91,7 @@ int mm_match_cgroup(const struct mm_struct *mm, const struct mem_cgroup *cgroup) rcu_read_lock(); memcg = mem_cgroup_from_task(rcu_dereference((mm)->owner)); - match = __mem_cgroup_same_or_subtree(cgroup, memcg); + match = memcg && __mem_cgroup_same_or_subtree(cgroup, memcg); rcu_read_unlock(); return match; } -- 1.7.11.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org