Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965221AbXHJTzW (ORCPT ); Fri, 10 Aug 2007 15:55:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S940230AbXHJTyn (ORCPT ); Fri, 10 Aug 2007 15:54:43 -0400 Received: from mx1.redhat.com ([66.187.233.31]:46908 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S938642AbXHJTyk (ORCPT ); Fri, 10 Aug 2007 15:54:40 -0400 Message-ID: <46BCC26B.6080600@redhat.com> Date: Fri, 10 Aug 2007 15:54:19 -0400 From: Chris Snook User-Agent: Thunderbird 1.5.0.12 (Macintosh/20070509) MIME-Version: 1.0 To: David Howells CC: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, torvalds@linux-foundation.org, netdev@vger.kernel.org, akpm@linux-foundation.org, ak@suse.de, heiko.carstens@de.ibm.com, davem@davemloft.net, schwidefsky@de.ibm.com, wensong@linux-vs.org, horms@verge.net.au, wjiang@resilience.com, cfriesen@nortel.com, zlynx@acm.org, rpjday@mindspring.com, jesper.juhl@gmail.com Subject: Re: [PATCH 6/24] make atomic_read() behave consistently on frv References: <46BB46B2.60808@redhat.com> <20070809134150.GA14890@shell.boston.redhat.com> <2708.1186737826@redhat.com> In-Reply-To: <2708.1186737826@redhat.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 Content-Length: 830 Lines: 21 David Howells wrote: > Chris Snook wrote: > >> To head off the criticism, I admit this is an oversimplification, and true >> busy-waiters should be using cpu_relax(), which contains a barrier. > > Why would you want to use cpu_relax()? That's there to waste time efficiently, > isn't it? Shouldn't you be using smp_rmb() or something like that? > > David cpu_relax() contains a barrier, so it should do the right thing. For non-smp architectures, I'm concerned about interacting with interrupt handlers. Some drivers do use atomic_* operations. -- Chris - 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/