From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from hu-out-0506.google.com ([72.14.214.238]:58715 "EHLO hu-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763654AbXHXMvl (ORCPT ); Fri, 24 Aug 2007 08:51:41 -0400 Received: by hu-out-0506.google.com with SMTP id 19so497651hue for ; Fri, 24 Aug 2007 05:51:39 -0700 (PDT) From: Denys Vlasenko Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures Date: Fri, 24 Aug 2007 13:50:44 +0100 References: <20070809131423.GA9927@shell.boston.redhat.com> <18115.35524.56393.347841@cargo.ozlabs.ibm.com> In-Reply-To: <18115.35524.56393.347841@cargo.ozlabs.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200708241350.45061.vda.linux@googlemail.com> Sender: linux-arch-owner@vger.kernel.org To: Paul Mackerras Cc: Satyam Sharma , Stefan Richter , Christoph Lameter , Chris Snook , Linux Kernel Mailing List , linux-arch@vger.kernel.org, Linus Torvalds , netdev@vger.kernel.org, Andrew Morton , 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, segher@kernel.crashing.org, Herbert Xu , "Paul E. McKenney" List-ID: On Thursday 16 August 2007 00:22, Paul Mackerras wrote: > Satyam Sharma writes: > In the kernel we use atomic variables in precisely those situations > where a variable is potentially accessed concurrently by multiple > CPUs, and where each CPU needs to see updates done by other CPUs in a > timely fashion. That is what they are for. Therefore the compiler > must not cache values of atomic variables in registers; each > atomic_read must result in a load and each atomic_set must result in a > store. Anything else will just lead to subtle bugs. Amen. -- vda