From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linux-foundation.org (smtp1.linux-foundation.org [140.211.169.13]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "smtp.linux-foundation.org", Issuer "CA Cert Signing Authority" (verified OK)) by ozlabs.org (Postfix) with ESMTPS id 4A602DE125 for ; Wed, 28 May 2008 03:32:03 +1000 (EST) Date: Tue, 27 May 2008 10:31:14 -0700 (PDT) From: Linus Torvalds To: Benjamin Herrenschmidt Subject: Re: MMIO and gcc re-ordering issue In-Reply-To: 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> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, tpiepho@freescale.com, linuxppc-dev@ozlabs.org, scottwood@freescale.com, David Miller , alan@lxorguk.ukuu.org.uk List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, 27 May 2008, Linus Torvalds wrote: > > Here's a UNTESTED patch for x86 that may or may not compile and work, and > which serializes (on a compiler level) the IO accesses against regular > memory accesses. Ok, so it at least boots on x86-32. Thus probably on x86-64 too (since the code is now shared). I didn't look at whether it generates much bigger code due to the potential extra serialization, but some of the code generation I looked at looked fine. IOW, it doesn't at least create any _obviously_ worse code, and it should be arguably safer than assuming the compiler does volatile accesses the way we want it to. Linus