linux-kernel - Re: [RFC PATCH] take all anon_vma locks in anon_vma

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Message-ID: <20100428180336.GC510@random.random>
Date:	Wed, 28 Apr 2010 20:03:36 +0200
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	Mel Gorman <mel@....ul.ie>, Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Minchan Kim <minchan.kim@...il.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Christoph Lameter <cl@...ux.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC PATCH] take all anon_vma locks in anon_vma_lock

On Wed, Apr 28, 2010 at 01:47:19PM -0400, Rik van Riel wrote:
>  static inline void anon_vma_unlock(struct vm_area_struct *vma)

never mind as this is RFC, lock is clear enough

> @@ -1762,7 +1760,8 @@ static int expand_downwards(struct vm_area_struct *vma,
>  	if (error)
>  		return error;
>  
> -	anon_vma_lock(vma);
> +	spin_lock(&mm->page_table_lock);
> +	anon_vma_lock(vma, &mm->page_table_lock);

This will cause a lock inversion (page_table_lock can only be taken
after the anon_vma lock). I don't immediately see why the
page_table_lock here though?
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