linux-kernel - Re: [PATCH 2/2] cgroups: convert ss->attach to use whole threadgroup flex

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Message-ID: <20111014135323.GA3653@ghc17.ghc.andrew.cmu.edu>
Date:	Fri, 14 Oct 2011 09:53:23 -0400
From:	Ben Blum <bblum@...rew.cmu.edu>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Ben Blum <bblum@...rew.cmu.edu>, Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org,
	NeilBrown <neilb@...e.de>, paulmck@...ux.vnet.ibm.com,
	Paul Menage <paul@...lmenage.org>,
	Li Zefan <lizf@...fujitsu.com>,
	containers@...ts.linux-foundation.org,
	Balbir Singh <bsingharora@...il.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH 2/2] cgroups: convert ss->attach to use whole
 threadgroup flex_array (cpuset, memcontrol)

On Fri, Oct 14, 2011 at 02:21:30PM +0200, Frederic Weisbecker wrote:
> On Thu, Oct 13, 2011 at 08:36:01PM -0400, Ben Blum wrote:
> > Convert ss->attach to take a flex_array of tasks instead of just the leader.
> > 
> > From: Ben Blum <bblum@...rew.cmu.edu>
> > 
> > This lets subsystems with whole-threadgroup attach calls (i.e., cpuset and
> > memcontrol) to accurately find the group's mm even when a non-leader does exec
> > and leaves the leader with a NULL mm pointer.
> > 
> > Also converts cpuset and memcontrol to take the flex_array and iterate down it
> > until an mm is found, instead of just attempting to use the leader's mm.
> > 
> > Signed-off-by: Ben Blum <bblum@...rew.cmu.edu>
> 
> I think there are patches from Tejun that handle that did that already?
> 
> https://lkml.org/lkml/2011/8/23/418
> 

Yeah, I'm not hoping to preempt them or anything; I'm just presenting
this alternate approach, since (1) this way addresses the ss->attach()
problem directly without needing to add locking anywhere else, while the
focus of the discussion around Tejun's patches seems to have moved to
more global concerns, and (2) these patches and his patches ought to be
compatible with each other.

Ben
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