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Date: Tue, 17 Jul 2007 13:01:18 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Hugh Dickins <hugh@veritas.com>
Cc: Joe Jin <joe.jin@oracle.com>, bill.irwin@oracle.com,
       linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Add nid sanity on alloc_pages_node
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On Tue, 17 Jul 2007 20:49:25 +0100 (BST) Hugh Dickins <hugh@veritas.com> wrote:

> --- 2.6.22-git9/mm/hugetlb.c	2007-07-17 20:29:33.000000000 +0100
> +++ linux/mm/hugetlb.c	2007-07-17 20:32:51.000000000 +0100
> @@ -107,15 +107,12 @@ static int alloc_fresh_huge_page(void)
>  {
>  	static int prev_nid;
>  	struct page *page;
> -	static DEFINE_SPINLOCK(nid_lock);
>  	int nid;
>  
> -	spin_lock(&nid_lock);
>  	nid = next_node(prev_nid, node_online_map);
>  	if (nid == MAX_NUMNODES)
>  		nid = first_node(node_online_map);
>  	prev_nid = nid;
> -	spin_unlock(&nid_lock);

Given that we've now gone and added deliberate-but-we-hope-benign 
races into this code, an elaborate comment which explains and justifies
it all is pretty much obligatory, IMO.