Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965210AbVKWWW7 (ORCPT ); Wed, 23 Nov 2005 17:22:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965212AbVKWWW7 (ORCPT ); Wed, 23 Nov 2005 17:22:59 -0500 Received: from terminus.zytor.com ([192.83.249.54]:54956 "EHLO terminus.zytor.com") by vger.kernel.org with ESMTP id S965211AbVKWWWw (ORCPT ); Wed, 23 Nov 2005 17:22:52 -0500 Message-ID: <4384EB98.5050408@zytor.com> Date: Wed, 23 Nov 2005 14:22:16 -0800 From: "H. Peter Anvin" User-Agent: Mozilla Thunderbird 1.0.7-1.1.fc4 (X11/20050929) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Alan Cox CC: Linus Torvalds , Andi Kleen , Gerd Knorr , Dave Jones , Zachary Amsden , Pavel Machek , Andrew Morton , Linux Kernel Mailing List , Zwane Mwaikambo , Pratap Subrahmanyam , Christopher Li , "Eric W. Biederman" , Ingo Molnar Subject: Re: [patch] SMP alternatives References: <4378A7F3.9070704@suse.de> <4379ECC1.20005@suse.de> <437A0649.7010702@suse.de> <437B5A83.8090808@suse.de> <438359D7.7090308@suse.de> <1132764133.7268.51.camel@localhost.localdomain> <20051123163906.GF20775@brahms.suse.de> <1132766489.7268.71.camel@localhost.localdomain> <4384AECC.1030403@zytor.com> <1132782245.13095.4.camel@localhost.localdomain> <1132786222.13095.28.camel@localhost.localdomain> In-Reply-To: <1132786222.13095.28.camel@localhost.localdomain> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1122 Lines: 33 Alan Cox wrote: > On Mer, 2005-11-23 at 13:36 -0800, Linus Torvalds wrote: > >>>have to add PAT support which we need to do anyway we would get a world >>>where on uniprocessor lock prefix only works on addresse targets we want >>>it to - ie pci_alloc_consistent() pages. >> >>No. That would be wrong. >> >>The thing is, "lock" is useless EVEN ON SMP in user space 99% of the time. > > > Now I see what you are aiming at, yes that makes vast amounts of sense > and since AMD have the "no lock effect" bit for general case maybe they > can > What it really comes down to (virtualization or not!) is whether or not the OS can guarantee that nothing else is messing with memory at the same time. This is potentially different from process to process (because of page table differences) and from kernel to user space (because of the User bit in the page tables.) -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/