linux-kernel - Re: race with page_referenced_one->ptep_test_and_clear

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Message-ID: <C32C1AD6.167B3%keir@xensource.com>
Date:	Fri, 05 Oct 2007 16:46:14 +0100
From:	Keir Fraser <keir@...source.com>
To:	Hugh Dickins <hugh@...itas.com>
CC:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Zachary Amsden <zach@...are.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Jan Beulich <jbeulich@...ell.com>, Andi Kleen <ak@...e.de>,
	Ken Chen <kenchen@...gle.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: race with page_referenced_one->ptep_test_and_clear_young and
 pagetable setup/pulldown

On 5/10/07 16:33, "Hugh Dickins" <hugh@...itas.com> wrote:

> If a 2.6.23 fix is needed, I suggest simply excluding split ptlocks
> in the Xen case, as shown by the mm/Kconfig - line in Jan's patch.

I didn't think that nobbling config options for particular pv_ops
implementations was acceptable? I'm rather out of the loop though, and could
be wrong.

The PREEMPT_BITS limitation is a good argument for at least taking the pte
locks in small batches though (small batches is preferable to one-by-one
since we will want to batch the make-readonly-and-pin hypercall requests to
amortise the cost of the hypervisor trap).

 -- Keir

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