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

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Date:	Wed, 14 Jul 2010 12:40:07 -0700
From:	"H.J. Lu" <hjl.tools@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	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>
Subject: Re: [patch 134/149] x86, paravirt: Add a global synchronization point 
	for pvclock

On Wed, Jul 14, 2010 at 12:36 PM, H. Peter Anvin <hpa@...or.com> wrote:
> On 07/14/2010 12:32 PM, H.J. Lu wrote:
>> On Wed, Jul 14, 2010 at 12:00 PM, H. Peter Anvin <hpa@...or.com> wrote:
>>> On 07/14/2010 11:18 AM, H.J. Lu wrote:
>>>>
>>>> There are some discussions on:
>>>>
>>>> http://gcc.gnu.org/ml/gcc-patches/2010-06/msg02001.html
>>>> http://gcc.gnu.org/ml/gcc-patches/2010-07/msg00001.html
>>>>
>>>> Are they related?
>>>>
>>>
>>> Not directly as far as I can tell.
>>>
>>> The issue is if gcc can ever reorder, duplicate or elide a volatile
>>> operation (either asm volatile or a volatile-annotated memory
>>> reference.)  In my (and Linus') opinion, this would be an incredibly
>>> serious bug.
>>
>> Is there a gcc bug for this?
>>
>
> Are you asking for a bug report against the documentation?  We're not
> sure what the semantics intended by the gcc team to be, which I guess is
> a documentation bug.
>

Documentation bug is also a bug :-).


-- 
H.J.
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