linux-kernel - Re: [patch] mm, memcg: store memcg name for oom kill log consistency

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Date:	Mon, 9 Sep 2013 02:00:26 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Michal Hocko <mhocko@...e.cz>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch] mm, memcg: store memcg name for oom kill log
 consistency

On Thu, 5 Sep 2013, Michal Hocko wrote:

> From 4cee36f56100f5689fe1ae22f468016ce5a0cbae Mon Sep 17 00:00:00 2001
> From: Michal Hocko <mhocko@...e.cz>
> Date: Thu, 5 Sep 2013 15:39:20 +0200
> Subject: [PATCH] memcg, oom: lock mem_cgroup_print_oom_info
> 
> mem_cgroup_print_oom_info uses a static buffer (memcg_name) to store the
> name of the cgroup. This is not safe as pointed out by David Rientjes
> because although memcg oom is locked for its hierarchy nothing prevents
> another parallel hierarchy to trigger oom as well and overwrite the
> already in-use buffer.
> 
> This patch introduces oom_info_lock hidden inside mem_cgroup_print_oom_info
> which is held throughout the function. It make access to memcg_name safe
> and as a bonus it also prevents parallel memcg ooms to interleave their
> statistics which would make the printed data hard to analyze otherwise.
> 
> Using the spinlock is OK here because this path is not hot and
> meaningful data is much more important.
> 
> Reported-by: David Rientjes <rientjes@...gle.com>

Remove this.

> Signed-off-by: Michal Hocko <mhocko@...e.cz>
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