linux-kernel - Re: [RESEND, PATCH 4/6] memcg: fix broken boolean expression

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Message-ID: <20120116115416.GA25687@shutemov.name>
Date:	Mon, 16 Jan 2012 13:54:16 +0200
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	linux-mm@...ck.org, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Balbir Singh <bsingharora@...il.com>,
	Michal Hocko <mhocko@...e.cz>, stable@...nel.org
Subject: Re: [RESEND, PATCH 4/6] memcg: fix broken boolean expression

On Mon, Jan 09, 2012 at 03:04:04PM +0100, Johannes Weiner wrote:
> On Fri, Jan 06, 2012 at 10:57:50PM +0200, Kirill A. Shutemov wrote:
> > From: "Kirill A. Shutemov" <kirill@...temov.name>
> > 
> > action != CPU_DEAD || action != CPU_DEAD_FROZEN is always true.
> > 
> > Signed-off-by: Kirill A. Shutemov <kirill@...temov.name>
> > Cc: <stable@...nel.org>
> 
> I think you don't need to actually CC stable via email.  If you
> include that tag, they will pick it up once the patch hits mainline.

I don't think it's a problem for stable@.

> 
> The changelog is too terse, doubly so for a patch that should go into
> stable.  How is the code supposed to work?  What are the consequences
> of the bug?

Is it enough?

---

>From fe1c2f2dc1abf63cce12017e2d9031cf67f0a161 Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill@...temov.name>
Date: Sat, 24 Dec 2011 04:12:53 +0200
Subject: [PATCH 4/6] memcg: fix broken boolean expression

action != CPU_DEAD || action != CPU_DEAD_FROZEN is always true.

We should return at the point if CPU doesn't go away. Otherwise drain
all counters and stocks from the CPU.

Signed-off-by: Kirill A. Shutemov <kirill@...temov.name>
Cc: <stable@...nel.org>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Acked-by: Michal Hocko <mhocko@...e.cz>
---
 mm/memcontrol.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 4ed6737..513ae04 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2095,9 +2095,11 @@ 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;
 
+	/* CPU goes away */
+
 	for_each_mem_cgroup(iter)
 		mem_cgroup_drain_pcp_counter(iter, cpu);
 
-- 
1.7.8.3

-- 
 Kirill A. Shutemov
--
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