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

[H. Peter Anvin]

On 07/14/2010 01:45 PM, Zachary Amsden wrote:
> That's the kind of bug I think Linus is talking about.  We've been
> expecting volatile to work that way for over a decade, by my
> recollection, and if it doesn't, there is going to be a lot of broken code.
> 
> Shouldn't we at least get a compiler switch to force the volatile
> behavior?  I'd suggest it default to conservative.

At this point, it looks like there is no reason to be alarmed.  The
documentation actually contains a statement about volatiles not being
mutually reordered across sequence points, and since asm is a statement
(rather than an expression) it is always surrounded by sequence points.
 I have filed a gcc ticket to ask for clarification.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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