From: Michal Hocko <mhocko@suse.cz>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Konstantin Khlebnikov <khlebnikov@openvz.org>,
linux-mm@kvack.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [patch 1/2] mm: memcontrol: handle potential crash when rmap races with task exit
Date: Thu, 4 Oct 2012 20:49:58 +0200 [thread overview]
Message-ID: <20121004184958.GG27536@dhcp22.suse.cz> (raw)
In-Reply-To: <1349374157-20604-2-git-send-email-hannes@cmpxchg.org>
On Thu 04-10-12 14:09:16, Johannes Weiner wrote:
> 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.
This seems to be fixed by Hugh's patch 3a981f48 "memcg: fix use_hierarchy
css_is_ancestor oops regression" which seems to be merged already.
>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
> 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
>
--
Michal Hocko
SUSE Labs
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next prev parent reply other threads:[~2012-10-04 18:50 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-04 18:09 [patch 0/2] memcg fixups that fell through cracks in 3.5 Johannes Weiner
2012-10-04 18:09 ` [patch 1/2] mm: memcontrol: handle potential crash when rmap races with task exit Johannes Weiner
2012-10-04 18:49 ` Michal Hocko [this message]
2012-10-04 20:19 ` Johannes Weiner
2012-10-05 7:05 ` Michal Hocko
2012-10-04 18:09 ` [patch 2/2] mm: memcg: clean up mm_match_cgroup() signature Johannes Weiner
2012-10-05 20:53 ` Andrew Morton
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