Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756315Ab0GMWSh (ORCPT ); Tue, 13 Jul 2010 18:18:37 -0400 Received: from terminus.zytor.com ([198.137.202.10]:35349 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751988Ab0GMWSg (ORCPT ); Tue, 13 Jul 2010 18:18:36 -0400 Message-ID: <4C3CE560.5050701@zytor.com> Date: Tue, 13 Jul 2010 15:14:56 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.10) Gecko/20100621 Fedora/3.0.5-1.fc13 Thunderbird/3.0.5 MIME-Version: 1.0 To: Jeremy Fitzhardinge CC: Linus Torvalds , 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 Subject: Re: [patch 134/149] x86, paravirt: Add a global synchronization point for pvclock 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> In-Reply-To: <4C3CAE8F.10900@goop.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1128 Lines: 29 On 07/13/2010 11:21 AM, Jeremy Fitzhardinge wrote: > > "asm volatile"'s only real meaning is that it will not get elided if it > appears its output is unused (assuming it is reachable at all). I don't > think you can consider it having any meaningful effects on ordering. > Actually, I believe volatile operations (including asm volatile) are strictly ordered *with respect to other volatile operations*. As such I would think we'd want to keep the "memory" clobber here, to make it strictly ordered with regards to *all* memory operations. As for the concept in this patch, it's obviously the right thing, but as Linus said elsewhere it's incomplete. Conceptually: Acked-by: H. Peter Anvin Unfortunately I can't write the productization patch right now since I have a plane to catch in about an hour, but if noone beats me to it I'll to it Thursday. -hpa -- 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/