linux-kernel - Re: [patch v2 2/6] memcg: keep prev's css alive for the whole mem_cgroup

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Message-ID: <50B5CD94.5020105@jp.fujitsu.com>
Date:	Wed, 28 Nov 2012 17:38:44 +0900
From:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Michal Hocko <mhocko@...e.cz>
CC:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Johannes Weiner <hannes@...xchg.org>,
	Ying Han <yinghan@...gle.com>, Tejun Heo <htejun@...il.com>,
	Glauber Costa <glommer@...allels.com>,
	Li Zefan <lizefan@...wei.com>
Subject: Re: [patch v2 2/6] memcg: keep prev's css alive for the whole mem_cgroup_iter

(2012/11/27 3:47), Michal Hocko wrote:
> css reference counting keeps the cgroup alive even though it has been
> already removed. mem_cgroup_iter relies on this fact and takes a
> reference to the returned group. The reference is then released on the
> next iteration or mem_cgroup_iter_break.
> mem_cgroup_iter currently releases the reference right after it gets the
> last css_id.
> This is correct because neither prev's memcg nor cgroup are accessed
> after then. This will change in the next patch so we need to hold the
> group alive a bit longer so let's move the css_put at the end of the
> function.
> 
> Signed-off-by: Michal Hocko <mhocko@...e.cz>

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>


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