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

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Date:	Tue, 13 Jul 2010 20:23:34 +0200
From:	Peter Palfrader <peter@...frader.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Avi Kivity <avi@...hat.com>, Greg KH <gregkh@...e.de>,
	linux-kernel@...r.kernel.org, stable@...nel.org,
	stable-review@...nel.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, 13 Jul 2010, Linus Torvalds wrote:

> On Tue, Jul 13, 2010 at 10:50 AM, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> >
> > 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?

It appears to, thanks a lot.

[git|v2.6.32.16] weasel@...lma:/scratch/kernel/2.6.32.16$ nm arch/x86/kernel/pvclock.o
0000000000000000 b last_value
..

And it did boot too.

> Btw, this second patch was a bit more aggressive than the first one,
> and actually removes the "memory" clobber entirely, and the fake cast
> of the target type.

Without the cast gcc spews a fair amount of warnings.  About four every
time it hits the include file.


Just for completeness' sake I attached the patch on top of 2.6.32.16
that I built with.
-- 
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