linux-kernel - Re: [RFC][PATCH 5/4] memcg: don't call res_counter

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Message-Id: <20090115142725.c3ee5dc4.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 15 Jan 2009 14:27:25 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	balbir@...ux.vnet.ibm.com
Cc:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Li Zefan <lizf@...fujitsu.com>, Paul Menage <menage@...gle.com>
Subject: Re: [RFC][PATCH 5/4] memcg: don't call res_counter_uncharge when
 obsolete

On Thu, 15 Jan 2009 10:47:17 +0530
Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:

> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2009-01-15 13:52:23]:

> > I think rmdir() should succeed everywhen "there are no tasks and children".
> > And that can be done.
> >
> 
> All I am saying is that let rmdir() fail if there are tasks or
> children, which I suspect cgroup takes care of. The second thing to do would
> be to add a mem_cgroup_get_hierarchical() and _put_hierarchical() API's so
> that we can get references all the way up to the parents. My concern
> is that not calling res_counter_uncharge() can lead to dangling
> references and bad behaviour.
>  
> > With Paul's suggestion, I'll add wait_queue for rmdir of cgroup.
> > 
> 
> That might be a good idea and also a good idea to maintain the
> hierarchy (since we will walk up when we do uncharge) until we know
> that css reference count is down to 0.
> 
It seems Nishimura started his work in that direction. (see other mail.)
Let's wait a bit.

-Kame

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