linux-kernel - Re: [PATCH] mm: fix hang on anon

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Message-ID: <AANLkTikML=HghpOVK0WZ0t6CRaNOKvu=57ebojZ+YCNS@mail.gmail.com>
Date:	Fri, 27 Aug 2010 14:33:35 -0700
From:	Hugh Dickins <hughd@...gle.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Andrea Arcangeli <aarcange@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] mm: fix hang on anon_vma->root->lock

Sorry, I seem to have hit some key which sent the mail off too soon, a
tab perhaps: finishing up...

On Fri, Aug 27, 2010 at 2:28 PM, Hugh Dickins <hughd@...gle.com> wrote:
> On Fri, Aug 27, 2010 at 1:56 PM, Christoph Lameter <cl@...ux.com> wrote:
>>
>>> of that second check, then we know that we got the right anon_vma,
>>
>> I do not see a second check (*after* taking the lock) in the patch

        if (page_mapped(page))
                return anon_vma;

>> and the way the lock is taken can be a problem in itself.

No, that's what we rely upon SLAB_DESTROY_BY_RCU for.

Hugh
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