From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lxorguk.ukuu.org.uk (earthlight.etchedpixels.co.uk [81.2.110.250]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id E3EBADDF78 for ; Tue, 27 May 2008 18:41:18 +1000 (EST) Date: Tue, 27 May 2008 09:24:30 +0100 From: Alan Cox To: David Miller Subject: Re: MMIO and gcc re-ordering issue Message-ID: <20080527092430.6380d962@core> In-Reply-To: <20080526.192812.184590464.davem@davemloft.net> 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 Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, scottwood@freescale.com, torvalds@linux-foundation.org, tpiepho@freescale.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , > 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