linux-kernel - Re: [BUGFIX][PATCH] memcg rcu lock fix v3

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Message-ID: <20100423070011.GS3994@balbir.in.ibm.com>
Date:	Fri, 23 Apr 2010 12:30:11 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Li Zefan <lizf@...fujitsu.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [BUGFIX][PATCH] memcg rcu lock fix v3

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2010-04-23 13:03:49]:

> On Fri, 23 Apr 2010 12:58:14 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
> 
> > On Fri, 23 Apr 2010 11:55:16 +0800
> > Li Zefan <lizf@...fujitsu.com> wrote:
> > 
> > > Li Zefan wrote:
> > > > KAMEZAWA Hiroyuki wrote:
> > > >> On Fri, 23 Apr 2010 11:00:41 +0800
> > > >> Li Zefan <lizf@...fujitsu.com> wrote:
> > > >>
> > > >>> with CONFIG_PROVE_RCU=y, I saw this warning, it's because
> > > >>> css_id() is not under rcu_read_lock().
> > > >>>
> > > >> Ok. Thank you for reporting.
> > > >> This is ok ? 
> > > > 
> > > > Yes, and I did some more simple tests on memcg, no more warning
> > > > showed up.
> > > > 
> > > 
> > > oops, after trigging oom, I saw 2 more warnings:
> > > 
> > 
> > Thank you for good testing.
> v3 here...sorry too rapid posting...
> 

Looking at the patch we seem to be protecting the use of only css_*().
I wonder if we should push down the rcu_read_*lock() semnatics to the
css routines or is it just too instrusive to do it that way?

-- 
	Three Cheers,
	Balbir
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