From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964909AbWD0DbO (ORCPT ); Wed, 26 Apr 2006 23:31:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964910AbWD0DbO (ORCPT ); Wed, 26 Apr 2006 23:31:14 -0400 Received: from smtp104.mail.mud.yahoo.com ([209.191.85.214]:44379 "HELO smtp104.mail.mud.yahoo.com") by vger.kernel.org with SMTP id S964909AbWD0DbN (ORCPT ); Wed, 26 Apr 2006 23:31:13 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:Message-ID:Date:From:User-Agent:X-Accept-Language:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; b=ZAH+urJ4N11q6a5Rfv500F9lMC4YqApKoeaBgHdZaTMDV3TN5R5YUxGebAW5x3wQOOac5hn3a4b0H36K1utyPCajAH4HNyrbeGTR3iLgKHFz0f+SsNMwzxKEHaD1Jv8wKXnlpyj9z6a/OQK1IFHwCm3v0PwYjP+U+wsEyXbpJ94= ; Message-ID: <44503AD5.9020605@yahoo.com.au> Date: Thu, 27 Apr 2006 13:30:29 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.8) Gecko/20050927 Debian/1.7.8-1sarge3 X-Accept-Language: en MIME-Version: 1.0 To: Zachary Amsden CC: Andrew Morton , Linux-Kernel , Hugh Dickins , Jan Beulich , Keir Fraser , Pratap Subrahmanyam Subject: Re: [PATCH 2/2] I386 convert pae wmb to non smp References: <200604262203.k3QM3qOC009581@zach-dev.vmware.com> <445009A2.3030305@yahoo.com.au> <445019E7.80900@vmware.com> In-Reply-To: <445019E7.80900@vmware.com> 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 Zachary Amsden wrote: > Nick Piggin wrote: > >> wmb() means that it also orders IO memory. It is no difference for >> i386, but smp_wmb() actually has the right semantics of the abstract >> Linux memory model. > > > The name is pretty confused. smp_wmb seems to imply an SMP-only > barrier, whereas we want here a write barrier on regular memory. That is just a compiler barrier (barrier()). A CPU should always be consistent with itself so memory ordering doesn't really apply there (hence smp_ prefix, which also are compiler barriers, of course). > Both smp_wmb and wmb() are identical in that they both reduce to > barrier today, but I confess not to know which one semantically is > correct. Well you're only looking at i386. True it is i386 specific code, but sticking to the Linux memory model is more clear and consistent I think. > Your call on this patch - it is unecessary, I thought it was more > semantically correct, but you probably know that better than me. So, > drop part 2 of this patch? Yes, and make part 1 use smp_wmb. -- Send instant messages to your online friends http://au.messenger.yahoo.com