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Date: Thu, 15 Jul 2010 21:48:36 -0700 From: "H. Peter Anvin" <hpa@...or.com> To: Zachary Amsden <zamsden@...hat.com> CC: Jeremy Fitzhardinge <jeremy@...p.org>, Avi Kivity <avi@...hat.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Peter Palfrader <peter@...frader.org>, 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>, Marcelo Tosatti <mtosatti@...hat.com> Subject: Re: [patch 134/149] x86, paravirt: Add a global synchronization point for pvclock 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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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