Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752070AbWCHHlg (ORCPT ); Wed, 8 Mar 2006 02:41:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752089AbWCHHlg (ORCPT ); Wed, 8 Mar 2006 02:41:36 -0500 Received: from smtp102.mail.mud.yahoo.com ([209.191.85.212]:21437 "HELO smtp102.mail.mud.yahoo.com") by vger.kernel.org with SMTP id S1751120AbWCHHlf (ORCPT ); Wed, 8 Mar 2006 02:41:35 -0500 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=AEDZwj3eFq3FyqGnIwweTByXTcWp6LpQyRmVLbdR+8oIFEVI0bcLfY2mZeXTGqAa90nPPcOiHrVBWr3hLoF5U+zeC7B7xYUSqMUbh/i3C88vllzcdyKDJgzCNr/FFMHVNdf4BYlwsU8UdfCJBTTVeef0ghH/kpT4eYWEgxZEMKg= ; Message-ID: <440E8AAA.9030609@yahoo.com.au> Date: Wed, 08 Mar 2006 18:41:30 +1100 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20051007 Debian/1.7.12-1 X-Accept-Language: en MIME-Version: 1.0 To: Paul Mackerras CC: David Howells , torvalds@osdl.org, akpm@osdl.org, mingo@redhat.com, linux-arch@vger.kernel.org, linuxppc64-dev@ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] Document Linux's memory barriers References: <31492.1141753245@warthog.cambridge.redhat.com> <17422.19209.60360.178668@cargo.ozlabs.ibm.com> In-Reply-To: <17422.19209.60360.178668@cargo.ozlabs.ibm.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 797 Lines: 26 Paul Mackerras wrote: > David Howells writes: >>+ The way to deal with this is to insert an I/O memory barrier between the >>+ two accesses: >>+ >>+ *ADR = ctl_reg_3; >>+ mb(); >>+ reg = *DATA; > > > Ummm, this implies mb() is "an I/O memory barrier". I can see people > getting confused if they read this and then see mb() being used when > no I/O is being done. > Isn't it? Why wouldn't you just use smp_mb() if no IO is being done? -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com - 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/