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Date: Thu, 23 Jun 2011 10:34:55 +0900
From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
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To: rientjes@google.com
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        kamezawa.hiroyu@jp.fujitsu.com, mgorman@suse.de,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch 2/2] mm, hotplug: protect zonelist building with zonelists_mutex
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(2011/06/23 10:13), David Rientjes wrote:
> 959ecc48fc75 ("mm/memory_hotplug.c: fix building of node hotplug 
> zonelist") does not protect the build_all_zonelists() call with 
> zonelists_mutex as needed.  This can lead to races in constructing 
> zonelist ordering if a concurrent build is underway.  Protecting this with 
> lock_memory_hotplug() is insufficient since zonelists can be rebuild 
> though sysfs as well.
> 
> Signed-off-by: David Rientjes <rientjes@google.com>

Indeed.

 Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>

> ---
>  mm/memory_hotplug.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -498,7 +498,9 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
>  	 * The node we allocated has no zone fallback lists. For avoiding
>  	 * to access not-initialized zonelist, build here.
>  	 */
> +	mutex_lock(&zonelists_mutex);
>  	build_all_zonelists(NULL);
> +	mutex_unlock(&zonelists_mutex);
>  
>  	return pgdat;
>  }
> 
> --
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