linux-kernel - Re: [PATCH 2/2] mm: memcontrol

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Message-ID: <t2ucc557aab1005062215p41f6086p21a19710d528d034@mail.gmail.com>
Date:	Fri, 7 May 2010 08:15:22 +0300
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Phil Carmody <ext-phil.2.carmody@...ia.com>,
	balbir@...ux.vnet.ibm.com, nishimura@....nes.nec.co.jp,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Paul Menage <menage@...gle.com>,
	"lizf@...fujitsu.com" <lizf@...fujitsu.com>
Subject: Re: [PATCH 2/2] mm: memcontrol - uninitialised return value

On Fri, May 7, 2010 at 4:07 AM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@...fujitsu.com> wrote:
> On Thu, 6 May 2010 14:24:17 -0700
> Andrew Morton <akpm@...ux-foundation.org> wrote:
>
>> On Wed,  5 May 2010 14:21:49 +0300
>> Phil Carmody <ext-phil.2.carmody@...ia.com> wrote:
>>
>> > From: Phil Carmody <ext-phil.2.carmody@...ia.com>
>> >
>> > Only an out of memory error will cause ret to be set.
>> >
>> > Acked-by: Kirill A. Shutemov <kirill@...temov.name>
>> > Signed-off-by: Phil Carmody <ext-phil.2.carmody@...ia.com>
>> > ---
>> >  mm/memcontrol.c |    2 +-
>> >  1 files changed, 1 insertions(+), 1 deletions(-)
>> >
>> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> > index 90e32b2..09af773 100644
>> > --- a/mm/memcontrol.c
>> > +++ b/mm/memcontrol.c
>> > @@ -3464,7 +3464,7 @@ static int mem_cgroup_unregister_event(struct cgroup *cgrp, struct cftype *cft,
>> >     int type = MEMFILE_TYPE(cft->private);
>> >     u64 usage;
>> >     int size = 0;
>> > -   int i, j, ret;
>> > +   int i, j, ret = 0;
>> >
>> >     mutex_lock(&memcg->thresholds_lock);
>> >     if (type == _MEM)
>>
>> afacit the return value of cftype.unregister_event() is always ignored
>> anyway.  Perhaps it should be changed to void-returning, or fixed.
>>
>>
> Ah, it's now "TODO". But hmm...."unregister_event()" is called by workqueue.
> (for avoiding race?)

Because it can be called from atomic context.

> I think unregister_event should be "void" and mem_cgroup_unregister_event()
> should be implemented as "never fail" function.
>
> I'll try by myself....but if someone knows this event notifier implementation well,
> please.

Ok, better if I'll do it.
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