linux-kernel - Re: [PATCH] blkcg: have bh disable for 32bit UP system reading 64bit stats

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Message-ID: <528CF1F3.7020106@kernel.dk>
Date:	Wed, 20 Nov 2013 10:31:31 -0700
From:	Jens Axboe <axboe@...nel.dk>
To:	Tejun Heo <tj@...nel.org>, Hong Zhiguo <honkiko@...il.com>
CC:	vgoyal@...hat.com, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org, Hong Zhiguo <zhiguohong@...cent.com>
Subject: Re: [PATCH] blkcg: have bh disable for 32bit UP system reading 64bit
 stats

On 11/20/2013 10:24 AM, Tejun Heo wrote:
> On Wed, Nov 06, 2013 at 07:14:44PM +0800, Hong Zhiguo wrote:
>> From: Hong Zhiguo <zhiguohong@...cent.com>
>>
>> Update of blkg_stat and blkg_rwstat may happen in bh context.
>> While u64_stats_fetch_retry is only preempt_disable on 32bit
>> UP system. This is not enough to avoid preemption by bh and
>> may read strange 64 bit value.
>>
>> Signed-off-by: Hong Zhiguo <zhiguohong@...cent.com>
> 
> Acked-by: Tejun Heo <tj@...nel.org>
> 
> Jens, can you please pick this one up?  This probably needs to be
> tagged for stable too.

Yeah will do, thanks.

-- 
Jens Axboe

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