From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758789AbYE0Pgn (ORCPT ); Tue, 27 May 2008 11:36:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758578AbYE0PgW (ORCPT ); Tue, 27 May 2008 11:36:22 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:52316 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758681AbYE0PgU (ORCPT ); Tue, 27 May 2008 11:36:20 -0400 Date: Tue, 27 May 2008 08:35:29 -0700 (PDT) From: Linus Torvalds To: Benjamin Herrenschmidt 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 Subject: Re: MMIO and gcc re-ordering issue In-Reply-To: <1211859542.3286.46.camel@pasglop> Message-ID: 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> User-Agent: Alpine 1.10 (LFD 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 27 May 2008, Benjamin Herrenschmidt wrote: > > Yes. As it is today, tg3 for example is potentially broken on all archs > with newer gcc unless we either add "memory" clobber to readl/writel or > stick some wmb's in there (just a random driver I picked). > > So Linus, what is your take on that matter ? Let's just serialize the damn things, and add a memory clobber to them. Expecting people to fix up all drivers is simply not going to happen. And serializing things shouldn't be *that* expensive. People who cannot take the expense can continue to use the magic __raw_writel() etc stuff. Linus