From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org,
containers@lists.linux-foundation.org,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Balbir Singh <bsingharora@gmail.com>,
Michal Hocko <mhocko@suse.cz>,
Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH 5/6] memcg: fix broken boolen expression
Date: Thu, 5 Apr 2012 13:17:08 +0300 [thread overview]
Message-ID: <20120405101708.GA13824@shutemov.name> (raw)
In-Reply-To: <20120404143403.fd05a284.akpm@linux-foundation.org>
On Wed, Apr 04, 2012 at 02:34:03PM -0700, Andrew Morton wrote:
> On Sat, 24 Dec 2011 05:00:18 +0200
> "Kirill A. Shutemov" <kirill@shutemov.name> wrote:
>
> > From: "Kirill A. Shutemov" <kirill@shutemov.name>
> >
> > action != CPU_DEAD || action != CPU_DEAD_FROZEN is always true.
> >
> > Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
> > ---
> > mm/memcontrol.c | 2 +-
> > 1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index b27ce0f..3833a7b 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -2100,7 +2100,7 @@ static int __cpuinit memcg_cpu_hotplug_callback(struct notifier_block *nb,
> > return NOTIFY_OK;
> > }
> >
> > - if ((action != CPU_DEAD) || action != CPU_DEAD_FROZEN)
> > + if (action != CPU_DEAD && action != CPU_DEAD_FROZEN)
> > return NOTIFY_OK;
> >
> > for_each_mem_cgroup(iter)
>
> This spent too long in the backlog, sorry.
>
> I don't want to merge this patch into either mainline or -stable until
> I find out what it does!
>
> afacit the patch will newly cause the kernel to drain various resource
> counters away from the target CPU when the CPU_DEAD or CPU_DEAD_FROZEN
> events occur for thet CPU, yes?
Yes.
> So the user-visible effects of the bug whcih was just fixed is that
> these counters will be somewhat inaccurate after a CPU is taken down,
> yes?
Correct.
> Why wasn't this bug noticed before?
I guess CPU hotplug is not a usual test case for memcg changes. And the
result of the bug is inaccurate statistics, but not something dramatic
(oops, panic, etc.).
> Has anyone tested the patch and
> confirmed that the numbers are now correct?
I haven't. I found the bug with sparse.
> Given that this bug has been present for 1.5 years and nobody noticed,
> I don't think a backport into -stable is warranted?
>
--
Kirill A. Shutemov
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next prev parent reply other threads:[~2012-04-05 9:24 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-24 3:00 [PATCH 1/6] memcg: fix unused variable warning Kirill A. Shutemov
2011-12-24 3:00 ` [PATCH 2/6] memcg: mark more functions/variables as static Kirill A. Shutemov
2011-12-26 6:28 ` KAMEZAWA Hiroyuki
2011-12-27 14:05 ` Michal Hocko
2011-12-24 3:00 ` [PATCH 3/6] memcg: remove unused variable Kirill A. Shutemov
2011-12-26 6:29 ` KAMEZAWA Hiroyuki
2011-12-27 14:08 ` Michal Hocko
2011-12-24 3:00 ` [PATCH 4/6] memcg: mark stat field of mem_cgroup struct as __percpu Kirill A. Shutemov
2011-12-26 6:30 ` KAMEZAWA Hiroyuki
2011-12-27 14:11 ` Michal Hocko
2011-12-24 3:00 ` [PATCH 5/6] memcg: fix broken boolen expression Kirill A. Shutemov
2011-12-26 6:31 ` KAMEZAWA Hiroyuki
2011-12-26 6:57 ` Kirill A. Shutemov
2012-01-03 20:54 ` Greg KH
2011-12-27 14:17 ` Michal Hocko
2012-04-04 21:34 ` Andrew Morton
2012-04-05 10:17 ` Kirill A. Shutemov [this message]
2011-12-24 3:00 ` [PATCH 6/6] memcg: drop redundant brackets Kirill A. Shutemov
2011-12-26 6:40 ` KAMEZAWA Hiroyuki
2011-12-27 14:28 ` Michal Hocko
2011-12-26 6:25 ` [PATCH 1/6] memcg: fix unused variable warning KAMEZAWA Hiroyuki
2011-12-26 6:36 ` Kirill A. Shutemov
2011-12-26 6:42 ` KAMEZAWA Hiroyuki
2011-12-26 6:47 ` Kirill A. Shutemov
2011-12-26 6:50 ` KAMEZAWA Hiroyuki
2011-12-27 13:57 ` [PATCH] Makefiles: Disable unused-variable warning (was: Re: [PATCH 1/6] memcg: fix unused variable warning) Michal Hocko
2011-12-27 18:26 ` Kirill A. Shutemov
2011-12-29 10:42 ` Michal Hocko
2011-12-29 11:08 ` Kirill A. Shutemov
2011-12-29 11:16 ` Michal Hocko
2012-01-08 15:01 ` [PATCH] Makefiles: Disable unused-variable warning Michal Marek
2012-01-10 8:52 ` Michal Hocko
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