linux-kernel - Re: [patch 134/149] x86, paravirt: Add a global synchronization point for pvclock

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Date:	Tue, 13 Jul 2010 10:50:46 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Peter Palfrader <peter@...frader.org>, Avi Kivity <avi@...hat.com>,
	Greg KH <gregkh@...e.de>, linux-kernel@...r.kernel.org,
	stable@...nel.org, stable-review@...nel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Glauber Costa <glommer@...hat.com>,
	Zachary Amsden <zamsden@...hat.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Marcelo Tosatti <mtosatti@...hat.com>
Subject: Re: [patch 134/149] x86, paravirt: Add a global synchronization point 
	for pvclock

On Tue, Jul 13, 2010 at 10:25 AM, Peter Palfrader <peter@...frader.org> wrote:
>
> Linus's patch touches __xchg() whereas we're using __cmpxchg() in this
> particular case I think.
>
> At least, applying it to my 2.6.32.16 tree didn't help, last_value was
> still read-only.  Or I backported it wrong.

No, you didn't back-port it wrong. I just didn't fix the right part. I
thought the PV code used xchg, not cmpxchg, so I only patched that.
But cmpxchg has the exact same issue.

Does this fix it?

Again: UNTESTED.

                   Linus

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