From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alan Cox Subject: Re: MMIO and gcc re-ordering issue Date: Tue, 27 May 2008 09:24:30 +0100 Message-ID: <20080527092430.6380d962@core> References: <1211852026.3286.36.camel@pasglop> <20080526.184047.88207142.davem@davemloft.net> <1211854540.3286.42.camel@pasglop> <20080526.192812.184590464.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: Received: from earthlight.etchedpixels.co.uk ([81.2.110.250]:45050 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1757449AbYE0IlY (ORCPT ); Tue, 27 May 2008 04:41:24 -0400 In-Reply-To: <20080526.192812.184590464.davem@davemloft.net> Sender: linux-arch-owner@vger.kernel.org List-ID: To: David Miller Cc: benh@kernel.crashing.org, linux-arch@vger.kernel.org, scottwood@freescale.com, linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, tpiepho@freescale.com > It's just another complicated thing for driver authors to get wrong. > The other side of the coin is of course the cost. > > The only thing I am absolutely sure of is that we should make a > decision fast, document it, and just stick to it. It's unfortunate that the __read/___write versions have other different semantics. The default should definitely be ordered but having un-ordered ones as an option would be good for zapping the hot paths that matter. Most I/O paths aren't even worth the thinking time for non-ordered I/O. Alan