linux-kernel - Re: [RFC][PATCH 1/4] memcg: fix for mem_cgroup_get_reclaim_stat_from

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Message-Id: <20090109100531.03cd998f.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Fri, 9 Jan 2009 10:05:31 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	balbir@...ux.vnet.ibm.com, menage@...gle.com
Subject: Re: [RFC][PATCH 1/4] memcg: fix for
 mem_cgroup_get_reclaim_stat_from_page

On Fri, 09 Jan 2009 08:57:59 +0800
Li Zefan <lizf@...fujitsu.com> wrote:

> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index e2996b8..62e69d8 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -559,6 +559,10 @@ mem_cgroup_get_reclaim_stat_from_page(struct page *page)
> >  		return NULL;
> >  
> >  	pc = lookup_page_cgroup(page);
> > +	smp_rmb();
> 
> It is better to add a comment to explain this smp_rmb. I think it's recommended
> that every memory barrier has a comment.
> 
Ah, yes. good point.

Maybe text like this
/*
 * Used bit is set without atomic ops but after smp_wmb().
 * For making pc->mem_cgroup visible, insert smp_rmb() here.
 */

?
-Kame

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