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

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Message-ID: <20131120172413.GN28946@htj.dyndns.org>
Date:	Wed, 20 Nov 2013 12:24:13 -0500
From:	Tejun Heo <tj@...nel.org>
To:	Hong Zhiguo <honkiko@...il.com>
Cc:	vgoyal@...hat.com, cgroups@...r.kernel.org, axboe@...nel.dk,
	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 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.

Thanks!

-- 
tejun
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