linux-kernel - Re: [-mm] Add an owner to the mm

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Message-ID: <47F51DE7.7010204@linux.vnet.ibm.com>
Date:	Thu, 03 Apr 2008 23:41:51 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	Paul Menage <menage@...gle.com>
CC:	Pavel Emelianov <xemul@...nvz.org>,
	Hugh Dickins <hugh@...itas.com>,
	Sudhir Kumar <skumar@...ux.vnet.ibm.com>,
	YAMAMOTO Takashi <yamamoto@...inux.co.jp>, lizf@...fujitsu.com,
	linux-kernel@...r.kernel.org, taka@...inux.co.jp,
	linux-mm@...ck.org, David Rientjes <rientjes@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [-mm] Add an owner to the mm_struct (v7)

Paul Menage wrote:
> On Thu, Apr 3, 2008 at 10:44 AM, Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
>>  +
>>  +       /*
>>  +        * If there are other users of the mm and the owner (us) is exiting
>>  +        * we need to find a new owner to take on the responsibility.
>>  +        * When we use thread groups (CLONE_THREAD), the thread group
>>  +        * leader is kept around in zombie state, even after it exits.
>>  +        * delay_group_leader() ensures that if the group leader is around
>>  +        * we need not select a new owner.
>>  +        */
> 
> Hmm, is this new check for delay_group_leader() safe? Won't we have
> called exit_cgroup() by this point, and hence be reassigned to the
> root cgroup? And so mm->owner->cgroups won't point to the right place?
> 

cgroup_exit() comes in much later after exit_mm(). Moreover delay_group_leader()
is a function that checks to see if

We are the group leader and the thread group is not empty.

-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL
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