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

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Message-ID: <4C3DFED2.5000807@goop.org>
Date:	Wed, 14 Jul 2010 11:15:46 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	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, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Glauber Costa <glommer@...hat.com>,
	Zachary Amsden <zamsden@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	"H.J. Lu" <hjl.tools@...il.com>
Subject: Re: [patch 134/149] x86, paravirt: Add a global synchronization point
 	for pvclock

On 07/14/2010 11:08 AM, H. Peter Anvin wrote:
> Noone has talked about strict ordering between volatiles and
> (non-volatile) memory ops in general.  I have been talking about
> volatile to volatile ordering, and I thought I'd been very clear about that.
>   

OK.

> H.J., we're having a debate about the actual semantics of "volatile",
> especially "asm volatile" in gcc.  In particular, I believe that
> volatile operations should not be possible to reorder with regards to
> each other, and the kernel depends on that fact.
>   

I think we should consider that deprecated and rely on dependencies and
clobbers.

    J
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