From patchwork Wed Jan 27 08:35:46 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Zijlstra X-Patchwork-Id: 8131181 Return-Path: X-Original-To: patchwork-xen-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 0F45E9F818 for ; Wed, 27 Jan 2016 08:39:31 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 369FC20295 for ; Wed, 27 Jan 2016 08:39:30 +0000 (UTC) Received: from lists.xen.org (lists.xenproject.org [50.57.142.19]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id DD2892025B for ; Wed, 27 Jan 2016 08:39:24 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=lists.xen.org) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1aOLaH-000275-Pf; Wed, 27 Jan 2016 08:36:13 +0000 Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1aOLaH-000270-8Z for xen-devel@lists.xenproject.org; Wed, 27 Jan 2016 08:36:13 +0000 Received: from [85.158.139.211] by server-9.bemta-5.messagelabs.com id 66/39-29478-C7188A65; Wed, 27 Jan 2016 08:36:12 +0000 X-Env-Sender: peterz@infradead.org X-Msg-Ref: server-4.tower-206.messagelabs.com!1453883770!18395170!1 X-Originating-IP: [198.137.202.9] X-SpamReason: No, hits=0.0 required=7.0 tests= X-StarScan-Received: X-StarScan-Version: 7.35.1; banners=-,-,- X-VirusChecked: Checked Received: (qmail 27494 invoked from network); 27 Jan 2016 08:36:12 -0000 Received: from bombadil.infradead.org (HELO bombadil.infradead.org) (198.137.202.9) by server-4.tower-206.messagelabs.com with AES128-GCM-SHA256 encrypted SMTP; 27 Jan 2016 08:36:11 -0000 Received: from j217066.upc-j.chello.nl ([24.132.217.66] helo=twins) by bombadil.infradead.org with esmtpsa (Exim 4.80.1 #2 (Red Hat Linux)) id 1aOLZt-0000wt-7n; Wed, 27 Jan 2016 08:35:49 +0000 Received: by twins (Postfix, from userid 1000) id D908A1257A0D8; Wed, 27 Jan 2016 09:35:46 +0100 (CET) Date: Wed, 27 Jan 2016 09:35:46 +0100 From: Peter Zijlstra To: "Paul E. McKenney" Message-ID: <20160127083546.GJ6357@twins.programming.kicks-ass.net> References: <5696BA6E.4070508@imgtec.com> <20160114120445.GB15828@arm.com> <56980145.5030901@imgtec.com> <20160114204827.GE3818@linux.vnet.ibm.com> <56981212.7050301@imgtec.com> <20160114222046.GH3818@linux.vnet.ibm.com> <20160126102402.GE6357@twins.programming.kicks-ass.net> <20160126103200.GI6375@twins.programming.kicks-ass.net> <20160126110053.GA21553@arm.com> <20160126201143.GV4503@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20160126201143.GV4503@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2012-12-30) Cc: linux-mips@linux-mips.org, linux-ia64@vger.kernel.org, "Michael S. Tsirkin" , Will Deacon , virtualization@lists.linux-foundation.org, "H. Peter Anvin" , sparclinux@vger.kernel.org, Ingo Molnar , linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, Russell King - ARM Linux , user-mode-linux-devel@lists.sourceforge.net, linux-sh@vger.kernel.org, Michael Ellerman , x86@kernel.org, xen-devel@lists.xenproject.org, Ingo Molnar , linux-xtensa@linux-xtensa.org, james.hogan@imgtec.com, Arnd Bergmann , Stefano Stabellini , adi-buildroot-devel@lists.sourceforge.net, Leonid Yegoshin , ddaney.cavm@gmail.com, Thomas Gleixner , linux-metag@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Andrew Cooper , linux-kernel@vger.kernel.org, Ralf Baechle , Joe Perches , linuxppc-dev@lists.ozlabs.org, David Miller Subject: [Xen-devel] [PATCH] documentation: Add disclaimer X-BeenThere: xen-devel@lists.xen.org X-Mailman-Version: 2.1.13 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Tue, Jan 26, 2016 at 12:11:43PM -0800, Paul E. McKenney wrote: > So Peter, would you like to update your patch to include yourself > and Will as authors? Sure, here goes. Acked-by: Will Deacon --- Subject: documentation: Add disclaimer It appears people are reading this document as a requirements list for building hardware. This is not the intent of this document. Nor is it particularly suited for this purpose. The primary purpose of this document is our collective attempt to define a set of primitives that (hopefully) allow us to write correct code on the myriad of SMP platforms Linux supports. Its a definite work in progress as our understanding of these platforms, and memory ordering in general, progresses. Nor does being mentioned in this document mean we think its a particularly good idea; the data dependency barrier required by Alpha being a prime example. Yes we have it, no you're insane to require it when building new hardware. Signed-off-by: Peter Zijlstra (Intel) --- Documentation/memory-barriers.txt | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt index a61be39c7b51..98626125f484 100644 --- a/Documentation/memory-barriers.txt +++ b/Documentation/memory-barriers.txt @@ -4,8 +4,24 @@ By: David Howells Paul E. McKenney + Will Deacon + Peter Zijlstra -Contents: +========== +DISCLAIMER +========== + +This document is not a specification; it is intentionally (for the sake of +brevity) and unintentionally (due to being human) incomplete. This document is +meant as a guide to using the various memory barriers provided by Linux, but +in case of any doubt (and there are many) please ask. + +I repeat, this document is not a specification of what Linux expects from +hardware. + +======== +CONTENTS +======== (*) Abstract memory access model.