From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754092Ab2DEJcz (ORCPT ); Thu, 5 Apr 2012 05:32:55 -0400 Received: from shutemov.name ([176.9.204.213]:47349 "EHLO shutemov.name" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753139Ab2DEJcy (ORCPT ); Thu, 5 Apr 2012 05:32:54 -0400 X-Greylist: delayed 518 seconds by postgrey-1.27 at vger.kernel.org; Thu, 05 Apr 2012 05:32:53 EDT Date: Thu, 5 Apr 2012 13:17:08 +0300 From: "Kirill A. Shutemov" To: Andrew Morton Cc: linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, containers@lists.linux-foundation.org, KAMEZAWA Hiroyuki , Balbir Singh , Michal Hocko , Johannes Weiner Subject: Re: [PATCH 5/6] memcg: fix broken boolen expression Message-ID: <20120405101708.GA13824@shutemov.name> References: <1324695619-5537-1-git-send-email-kirill@shutemov.name> <1324695619-5537-5-git-send-email-kirill@shutemov.name> <20120404143403.fd05a284.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120404143403.fd05a284.akpm@linux-foundation.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.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" wrote: > > > From: "Kirill A. Shutemov" > > > > action != CPU_DEAD || action != CPU_DEAD_FROZEN is always true. > > > > Signed-off-by: Kirill A. Shutemov > > --- > > 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