linux-kernel - Re: [PATCH] Revert "mm/page_alloc: protect pcp->batch accesses with ACCESS

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Message-ID: <20160330103839.GA4773@techsingularity.net>
Date:	Wed, 30 Mar 2016 11:38:39 +0100
From:	Mel Gorman <mgorman@...hsingularity.net>
To:	He Kuang <hekuang@...wei.com>
Cc:	akpm@...ux-foundation.org, mhocko@...e.com, vbabka@...e.cz,
	rientjes@...gle.com, cody@...ux.vnet.ibm.com, gilad@...yossef.com,
	kosaki.motohiro@...il.com, mgorman@...e.de, penberg@...nel.org,
	lizefan@...wei.com, wangnan0@...wei.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Revert "mm/page_alloc: protect pcp->batch accesses with
 ACCESS_ONCE"

On Wed, Mar 30, 2016 at 10:22:07AM +0000, He Kuang wrote:
> This reverts commit 998d39cb236fe464af86a3492a24d2f67ee1efc2.
> 
> When local irq is disabled, a percpu variable does not change, so we can
> remove the access macros and let the compiler optimize the code safely.
> 

batch can be changed from other contexts. Why is this safe?

-- 
Mel Gorman
SUSE Labs