From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e36.co.us.ibm.com (e36.co.us.ibm.com [32.97.110.154]) (using TLSv1 with cipher CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 9009C1A004E for ; Fri, 15 Jan 2016 07:36:52 +1100 (AEDT) Received: from localhost by e36.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 14 Jan 2016 13:36:50 -0700 Received: from b03cxnp07028.gho.boulder.ibm.com (b03cxnp07028.gho.boulder.ibm.com [9.17.130.15]) by d03dlp02.boulder.ibm.com (Postfix) with ESMTP id 1DDBE3E4003F for ; Thu, 14 Jan 2016 13:36:49 -0700 (MST) Received: from d03av05.boulder.ibm.com (d03av05.boulder.ibm.com [9.17.195.85]) by b03cxnp07028.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u0EKanI727656298 for ; Thu, 14 Jan 2016 13:36:49 -0700 Received: from d03av05.boulder.ibm.com (localhost [127.0.0.1]) by d03av05.boulder.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u0EKaeYx010651 for ; Thu, 14 Jan 2016 13:36:48 -0700 Date: Thu, 14 Jan 2016 12:36:37 -0800 From: "Paul E. McKenney" To: Peter Zijlstra Cc: Leonid Yegoshin , Will Deacon , "Michael S. Tsirkin" , linux-kernel@vger.kernel.org, Arnd Bergmann , linux-arch@vger.kernel.org, Andrew Cooper , Russell King - ARM Linux , virtualization@lists.linux-foundation.org, Stefano Stabellini , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Joe Perches , David Miller , linux-ia64@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-metag@vger.kernel.org, linux-mips@linux-mips.org, x86@kernel.org, user-mode-linux-devel@lists.sourceforge.net, adi-buildroot-devel@lists.sourceforge.net, linux-sh@vger.kernel.org, linux-xtensa@linux-xtensa.org, xen-devel@lists.xenproject.org, Ralf Baechle , Ingo Molnar , ddaney.cavm@gmail.com, james.hogan@imgtec.com, Michael Ellerman Subject: Re: [v3,11/41] mips: reuse asm-generic/barrier.h Message-ID: <20160114203637.GD3818@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20160112114111.GB15737@arm.com> <569565DA.2010903@imgtec.com> <20160113104516.GE25458@arm.com> <56969F4B.7070001@imgtec.com> <20160113204844.GV6357@twins.programming.kicks-ass.net> <5696BA6E.4070508@imgtec.com> <20160114120445.GB15828@arm.com> <20160114161604.GT3818@linux.vnet.ibm.com> <5697FA0A.6040601@imgtec.com> <20160114201513.GI6357@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20160114201513.GI6357@twins.programming.kicks-ass.net> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, Jan 14, 2016 at 09:15:13PM +0100, Peter Zijlstra wrote: > On Thu, Jan 14, 2016 at 11:42:02AM -0800, Leonid Yegoshin wrote: > > An the only point - please use an appropriate SYNC_* barriers instead of > > heavy bold hammer. That stuff was design explicitly to support the > > requirements of Documentation/memory-barriers.txt > > That's madness. That document changes from version to version as to what > we _think_ the actual hardware does. It is _NOT_ a specification. There is work in progress on a specification, but please don't hold your breath. And I am not as optimistic as I might be about any formal specification keeping up with the Linux kernel or with the hardware that it supports. But it seems worth a good try. > You cannot design hardware from that. Its incomplete and fails to > specify a bunch of things. It not a mathematically sound definition of a > memory model. > > Please stop referring to that document for what a particular barrier > _should_ do. Explain what MIPS does, so we can attempt to integrate > this knowledge with our knowledge of PPC/ARM/Alpha/x86/etc. and improve > upon our understanding of hardware and improve the Linux memory model. Please! Thanx, Paul