Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932863AbXHXMw1 (ORCPT ); Fri, 24 Aug 2007 08:52:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1764894AbXHXMvo (ORCPT ); Fri, 24 Aug 2007 08:51:44 -0400 Received: from hu-out-0506.google.com ([72.14.214.237]:58537 "EHLO hu-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763606AbXHXMvl (ORCPT ); Fri, 24 Aug 2007 08:51:41 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=beta; h=received:from:to:subject:date:user-agent:cc:references:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:message-id; b=JOnonU7WDM90YP/k0Gljcdu0T9WWdXacJfoeEStyQ7Yqm0UfIyfQOcoj0m02gTKEnPTviuVD8s847GABJrtjDSDl4mRPn2rZfBgzEOPj3yt19Xz5GxWevg2o5IRJ1v/0igZJ7vivXyHV+3vYHnGgECJpSd2vMqqsqRqj+6z6PKk= From: Denys Vlasenko To: Paul Mackerras Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures Date: Fri, 24 Aug 2007 13:50:44 +0100 User-Agent: KMail/1.9.1 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" 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-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 809 Lines: 18 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 - 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/