From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752733AbbHMKtd (ORCPT ); Thu, 13 Aug 2015 06:49:33 -0400 Received: from foss.arm.com ([217.140.101.70]:34175 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752405AbbHMKtb (ORCPT ); Thu, 13 Aug 2015 06:49:31 -0400 Date: Thu, 13 Aug 2015 11:49:28 +0100 From: Will Deacon To: "Paul E. McKenney" Cc: Peter Zijlstra , "linux-arch@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Benjamin Herrenschmidt Subject: Re: [RFC PATCH v2] memory-barriers: remove smp_mb__after_unlock_lock() Message-ID: <20150813104928.GC10280@arm.com> References: <20150714141202.GN16213@arm.com> <20150714193144.GP3717@linux.vnet.ibm.com> <20150715013820.GA21971@linux.vnet.ibm.com> <20150715105135.GE1005@arm.com> <20150715131221.GY3717@linux.vnet.ibm.com> <20150724113101.GE30410@arm.com> <20150724153046.GJ3717@linux.vnet.ibm.com> <20150812134415.GC23540@arm.com> <20150812154346.GR3895@linux.vnet.ibm.com> <20150812175938.GA27985@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150812175938.GA27985@linux.vnet.ibm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 12, 2015 at 06:59:38PM +0100, Paul E. McKenney wrote: > On Wed, Aug 12, 2015 at 08:43:46AM -0700, Paul E. McKenney wrote: > > On Wed, Aug 12, 2015 at 02:44:15PM +0100, Will Deacon wrote: > > > The generic relaxed atomics are now queued in -tip, so it would be really > > > good to see this Documentation update land in 4.3 if at all possible. I > > > appreciate it's late in the cycle, but it's always worth asking. > > > > Can't hurt to give it a try. I have set -rcu's rcu/next branch to this > > commit, and if it passes a few day's worth of testing, I will see what > > Ingo has to say about a pull request. > > > > This commit also privatizes smp_mb__after_unlock_lock() as well as > > updating documentation. Looks like we need to strengthen powerpc's > > locking primitives, then get rid of smp_mb__after_unlock_lock() entirely. > > Or did that already happen and I just missed it? > > And just for completeness, here is the current version of that commit. > > Thanx, Paul > > ------------------------------------------------------------------------ > > b/Documentation/memory-barriers.txt | 71 +--------------------------------- > b/arch/powerpc/include/asm/spinlock.h | 2 > b/include/linux/spinlock.h | 10 ---- > b/kernel/rcu/tree.h | 12 +++++ > 4 files changed, 16 insertions(+), 79 deletions(-) > > commit 12d560f4ea87030667438a169912380be00cea4b > Author: Paul E. McKenney > Date: Tue Jul 14 18:35:23 2015 -0700 > > rcu,locking: Privatize smp_mb__after_unlock_lock() > > RCU is the only thing that uses smp_mb__after_unlock_lock(), and is > likely the only thing that ever will use it, so this commit makes this > macro private to RCU. > > Signed-off-by: Paul E. McKenney > Cc: Will Deacon > Cc: Peter Zijlstra > Cc: Benjamin Herrenschmidt > Cc: "linux-arch@vger.kernel.org" Acked-by: Will Deacon I don't think the PowerPC spinlock change is queued anywhere (I sent it out as a diff for discussion, but that was it). This patch doesn't rely on that though, right? Will