linux-kernel - Re: mm: Do not iterate over NR_CPUS in __zone_pcp

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Date:	Mon, 8 Mar 2010 15:29:16 +0200
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
	Christoph Lameter <cl@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>, Tejun Heo <tj@...nel.org>
Subject: Re: mm: Do not iterate over NR_CPUS in __zone_pcp_update()

On Mon, Mar 8, 2010 at 11:21 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
> __zone_pcp_update() iterates over NR_CPUS instead of limiting the
> access to the possible cpus. This might result in access to
> uninitialized areas as the per cpu allocator only populates the per
> cpu memory for possible cpus.
>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

Looks OK to me.

Acked-by: Pekka Enberg <penberg@...helsinki.fi>

> ---
>  mm/page_alloc.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> Index: linux-2.6/mm/page_alloc.c
> ===================================================================
> --- linux-2.6.orig/mm/page_alloc.c
> +++ linux-2.6/mm/page_alloc.c
> @@ -3224,7 +3224,7 @@ static int __zone_pcp_update(void *data)
>        int cpu;
>        unsigned long batch = zone_batchsize(zone), flags;
>
> -       for (cpu = 0; cpu < NR_CPUS; cpu++) {
> +       for_each_possible_cpu(cpu) {
>                struct per_cpu_pageset *pset;
>                struct per_cpu_pages *pcp;
>
>
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