From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [v3,11/41] mips: reuse asm-generic/barrier.h Date: Fri, 15 Jan 2016 22:27:14 +0100 Message-ID: <20160115212714.GM3421@worktop> References: <20160113104516.GE25458@arm.com> <5696CF08.8080700@imgtec.com> <20160114121449.GC15828@arm.com> <5697F6D2.60409@imgtec.com> <20160114203430.GC3818@linux.vnet.ibm.com> <56980C91.1010403@imgtec.com> <20160114212913.GF3818@linux.vnet.ibm.com> <20160115085554.GF3421@worktop> <20160115091348.GA27936@worktop> <20160115174612.GV3818@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20160115174612.GV3818@linux.vnet.ibm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: "Paul E. McKenney" 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 List-Id: linux-arch.vger.kernel.org On Fri, Jan 15, 2016 at 09:46:12AM -0800, Paul E. McKenney wrote: > On Fri, Jan 15, 2016 at 10:13:48AM +0100, Peter Zijlstra wrote: > > And the stuff we're confused about is how best to express the difference > > and guarantees of these two forms of transitivity and how exactly they > > interact. > > Hoping my memory-barrier.txt patch helps here... Yes, that seems a good start. But yesterday you raised the 'fun' point of two globally ordered sequences connected by a single local link. And I think I'm still confused on LWSYNC (in the smp_wmb case) when one of the stores looses a conflict, and if that scenario matters. If it does, we should inspect the same case for other barriers. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bombadil.infradead.org ([198.137.202.9]:36670 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751788AbcAOV1z (ORCPT ); Fri, 15 Jan 2016 16:27:55 -0500 Date: Fri, 15 Jan 2016 22:27:14 +0100 From: Peter Zijlstra Subject: Re: [v3,11/41] mips: reuse asm-generic/barrier.h Message-ID: <20160115212714.GM3421@worktop> References: <20160113104516.GE25458@arm.com> <5696CF08.8080700@imgtec.com> <20160114121449.GC15828@arm.com> <5697F6D2.60409@imgtec.com> <20160114203430.GC3818@linux.vnet.ibm.com> <56980C91.1010403@imgtec.com> <20160114212913.GF3818@linux.vnet.ibm.com> <20160115085554.GF3421@worktop> <20160115091348.GA27936@worktop> <20160115174612.GV3818@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160115174612.GV3818@linux.vnet.ibm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: "Paul E. McKenney" 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 Message-ID: <20160115212714.LLCs1HfVC7indg3fWs4wfFnWfw66mnNsf6sXCTFpWtc@z> On Fri, Jan 15, 2016 at 09:46:12AM -0800, Paul E. McKenney wrote: > On Fri, Jan 15, 2016 at 10:13:48AM +0100, Peter Zijlstra wrote: > > And the stuff we're confused about is how best to express the difference > > and guarantees of these two forms of transitivity and how exactly they > > interact. > > Hoping my memory-barrier.txt patch helps here... Yes, that seems a good start. But yesterday you raised the 'fun' point of two globally ordered sequences connected by a single local link. And I think I'm still confused on LWSYNC (in the smp_wmb case) when one of the stores looses a conflict, and if that scenario matters. If it does, we should inspect the same case for other barriers.