From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: [PATCH v2] barriers: introduce smp_mb__release_acquire and update documentation Date: Fri, 9 Oct 2015 13:41:28 +0100 Message-ID: <20151009124127.GO26278@arm.com> References: <1444215568-24732-1-git-send-email-will.deacon@arm.com> <20151007111915.GF17308@twins.programming.kicks-ass.net> <20151007132317.GK16065@arm.com> <20151007152501.GI3910@linux.vnet.ibm.com> <1444276236.9940.5.camel@ellerman.id.au> <20151008111638.GL3816@twins.programming.kicks-ass.net> <20151008214439.GE3910@linux.vnet.ibm.com> <20151009083138.GU3816@twins.programming.kicks-ass.net> <20151009094039.GD26278@arm.com> <20151009110246.GY3816@twins.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from foss.arm.com ([217.140.101.70]:38985 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754432AbbJIMlb (ORCPT ); Fri, 9 Oct 2015 08:41:31 -0400 Content-Disposition: inline In-Reply-To: <20151009110246.GY3816@twins.programming.kicks-ass.net> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Peter Zijlstra Cc: "Paul E. McKenney" , Michael Ellerman , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Boqun Feng , Anton Blanchard , Benjamin Herrenschmidt , Paul Mackerras , linuxppc-dev@lists.ozlabs.org On Fri, Oct 09, 2015 at 01:02:46PM +0200, Peter Zijlstra wrote: > On Fri, Oct 09, 2015 at 10:40:39AM +0100, Will Deacon wrote: > > Stepping back a second, I believe that there are three cases: > > > > > > RELEASE X -> ACQUIRE Y (same CPU) > > * Needs a barrier on TSO architectures for full ordering > +PPC > > > UNLOCK X -> LOCK Y (same CPU) > > * Needs a barrier on PPC for full ordering > > > > RELEASE X -> ACQUIRE X (different CPUs) > * Fully ordered everywhere... > * ... but needs a barrier on TSO + PPC to become a full barrier > > > UNLOCK X -> ACQUIRE X (different CPUs) > > s/ACQUIRE/LOCK/ ? Yes, sorry. Will