Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752764AbXHKEaL (ORCPT ); Sat, 11 Aug 2007 00:30:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750905AbXHKE35 (ORCPT ); Sat, 11 Aug 2007 00:29:57 -0400 Received: from e4.ny.us.ibm.com ([32.97.182.144]:54698 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750897AbXHKE3z (ORCPT ); Sat, 11 Aug 2007 00:29:55 -0400 Date: Fri, 10 Aug 2007 21:29:43 -0700 From: "Paul E. McKenney" To: Herbert Xu Cc: Chris Snook , dhowells@redhat.com, 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 Message-ID: <20070811042943.GA13410@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <46BCC26B.6080600@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1003 Lines: 22 On Sat, Aug 11, 2007 at 08:54:46AM +0800, Herbert Xu wrote: > Chris Snook wrote: > > > > 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. > > What problems with interrupt handlers? Access to int/long must > be atomic or we're in big trouble anyway. Reordering due to compiler optimizations. CPU reordering does not affect interactions with interrupt handlers on a given CPU, but reordering due to compiler code-movement optimization does. Since volatile can in some cases suppress code-movement optimizations, it can affect interactions with interrupt handlers. Thanx, Paul - 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/