linux-kernel - Re: [PATCH 4/4] cgroup: remove extra calls to find_existing_css

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Message-ID: <20111222154037.GC17084@google.com>
Date:	Thu, 22 Dec 2011 07:40:37 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Li Zefan <lizf@...fujitsu.com>,
	Mandeep Singh Baines <msb@...omium.org>,
	linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org, cgroups@...r.kernel.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Paul Menage <paul@...lmenage.org>
Subject: Re: [PATCH 4/4] cgroup: remove extra calls to find_existing_css_set

On Thu, Dec 22, 2011 at 10:44:39AM +0100, Frederic Weisbecker wrote:
> > >  		if (ent.cgrp == cgrp)
> > >  			continue;
> > > +		ent.cg = find_css_set(tsk->cgroups, cgrp);
> > 
> > unfortunately This won't work, because we are holding tasklist_lock.
> 
> I believe we can remove tasklist_lock now (in a seperate patch).
> 
> It was there in order to protect while_each_thread() against exec but
> now we have threadgroup_lock().
> 
> I think we only need to use rcu_read_lock() to protect against concurrent
> removal in exit.

Yeah, that should work and I really like this patch.

 kernel/cgroup.c |  152 ++++++++++++-------------------------------------------
 1 files changed, 32 insertions(+), 120 deletions(-)

Let's get it working. :)

Thanks.

-- 
tejun
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