From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753932AbYCNHwO (ORCPT ); Fri, 14 Mar 2008 03:52:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751926AbYCNHv6 (ORCPT ); Fri, 14 Mar 2008 03:51:58 -0400 Received: from terminus.zytor.com ([198.137.202.10]:37061 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751672AbYCNHv5 (ORCPT ); Fri, 14 Mar 2008 03:51:57 -0400 Message-ID: <47DA2E6F.5080907@zytor.com> Date: Fri, 14 Mar 2008 08:51:11 +0100 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.9 (X11/20071115) MIME-Version: 1.0 To: Jan Beulich CC: mingo@elte.hu, tglx@linutronix.de, linux-kernel@vger.kernel.org Subject: Re: [RFC] x86: bitops asm constraint fixes References: <47D8FD33.76E4.0078.0@novell.com> In-Reply-To: <47D8FD33.76E4.0078.0@novell.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jan Beulich wrote: > > I'd really like understand, though, what the policy of (not) having a > "memory" clobber in these operations is - currently, this appears to > be totally inconsistent. Also, many comments of the non-atomic > functions say those may also be re-ordered - this contradicts the use > of "asm volatile" in there, which again I'd like to understand. > In general, proper "m" constraints are better than "memory" clobbers, since they give gcc more information. Note that the "m" constraint doesn't actually have to be *manifest* in the assembly string. -hpa