From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759510AbYE0VNT (ORCPT ); Tue, 27 May 2008 17:13:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757924AbYE0VNL (ORCPT ); Tue, 27 May 2008 17:13:11 -0400 Received: from gate.crashing.org ([63.228.1.57]:35136 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757301AbYE0VNJ (ORCPT ); Tue, 27 May 2008 17:13:09 -0400 Subject: Re: MMIO and gcc re-ordering issue From: Benjamin Herrenschmidt Reply-To: benh@kernel.crashing.org To: Linus Torvalds Cc: David Miller , linux-arch@vger.kernel.org, scottwood@freescale.com, linuxppc-dev@ozlabs.org, alan@lxorguk.ukuu.org.uk, linux-kernel@vger.kernel.org, tpiepho@freescale.com In-Reply-To: References: <1211852026.3286.36.camel@pasglop> <20080526.184047.88207142.davem@davemloft.net> <1211854540.3286.42.camel@pasglop> <20080526.192812.184590464.davem@davemloft.net> <1211859542.3286.46.camel@pasglop> Content-Type: text/plain Date: Wed, 28 May 2008 07:12:46 +1000 Message-Id: <1211922766.3286.84.camel@pasglop> Mime-Version: 1.0 X-Mailer: Evolution 2.12.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2008-05-27 at 09:47 -0700, Linus Torvalds wrote: > > __read[bwlq]()/__write[bwlq]() are not serialized with a :"memory" > barrier, although since they still use "asm volatile" I suspect that > i > practice they are probably serial too. Did not look very closely at > any > generated code (only did a trivial test to see that the code looks > *roughly* correct). Nah, asm volatile doesn't help, it does need the "memory" clobber too. Cheers, Ben.