Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752347Ab0GNAPm (ORCPT ); Tue, 13 Jul 2010 20:15:42 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:52776 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750801Ab0GNAPl (ORCPT ); Tue, 13 Jul 2010 20:15:41 -0400 MIME-Version: 1.0 In-Reply-To: <4C3CFB8B.1090804@goop.org> References: <20100707124731.GJ15122@anguilla.noreply.org> <4C359D5A.1050906@redhat.com> <20100713102350.GW15122@anguilla.noreply.org> <4C3C68C8.4060409@redhat.com> <20100713141902.GB15122@anguilla.noreply.org> <4C3C8CE5.1080705@redhat.com> <20100713162207.GC15122@anguilla.noreply.org> <4C3C9589.4090602@redhat.com> <4C3C96EC.8060901@redhat.com> <4C3C9839.4090404@redhat.com> <20100713172526.GE15122@anguilla.noreply.org> <4C3CAE8F.10900@goop.org> <4C3CE560.5050701@zytor.com> <4C3CFB8B.1090804@goop.org> Date: Tue, 13 Jul 2010 17:15:02 -0700 Message-ID: Subject: Re: [patch 134/149] x86, paravirt: Add a global synchronization point for pvclock From: Linus Torvalds To: Jeremy Fitzhardinge Cc: "H. Peter Anvin" , Peter Palfrader , Avi Kivity , Greg KH , linux-kernel@vger.kernel.org, stable@kernel.org, stable-review@kernel.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Glauber Costa , Zachary Amsden , Marcelo Tosatti Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1683 Lines: 35 On Tue, Jul 13, 2010 at 4:49 PM, Jeremy Fitzhardinge wrote: > > The documentation makes no reference to that property; in fact it > suggests it is outright not true: The gcc documentation wrt inline asm's is totally worthless. Don't even bother quoting it - because the gcc people themselves have never cared. If the docs ever end up not matching what they want to do, they will just change the documentation. In other words, at least historically the docs are not in any way meaningful. They are not a "these are the semantics we guarantee", they are just random noise. As I mentioned, the docs historically just said something like "will not be moved significantly", and apparently they've been changed to be something else. The only thing that has ever been meaningful is "this works". And, of course, that has changed over time too, including actual recommendations on how to make something work (as mentioned, iirc "+" was only valid on register constraints, and "+m" used to not be allowed _or_ recommended, these days it's the only way to do certain things). It's irritating, because in other circumstances, gcc people take the reverse approach, and consider paper documentation more important than actual implementation issues. So sometimes they say "hey, this is the spec", but when it comes to their own docs, the answer has historically been "we'll just change the spec". Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/