From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [RFC PATCH v2] memory-barriers: remove smp_mb__after_unlock_lock() Date: Wed, 12 Aug 2015 08:43:46 -0700 Message-ID: <20150812154346.GR3895@linux.vnet.ibm.com> References: <20150714125146.GJ16213@arm.com> <20150714140014.GD3717@linux.vnet.ibm.com> <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> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from e35.co.us.ibm.com ([32.97.110.153]:33488 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753493AbbHLPnw (ORCPT ); Wed, 12 Aug 2015 11:43:52 -0400 Received: from /spool/local by e35.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 12 Aug 2015 09:43:51 -0600 Content-Disposition: inline In-Reply-To: <20150812134415.GC23540@arm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Will Deacon Cc: Peter Zijlstra , "linux-arch@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Benjamin Herrenschmidt On Wed, Aug 12, 2015 at 02:44:15PM +0100, Will Deacon wrote: > Hello Paul, > > On Fri, Jul 24, 2015 at 04:30:46PM +0100, Paul E. McKenney wrote: > > On Fri, Jul 24, 2015 at 12:31:01PM +0100, Will Deacon wrote: > > > On Wed, Jul 15, 2015 at 02:12:21PM +0100, Paul E. McKenney wrote: > > > > > > commit 695c05d4b9666c50b40a1c022678b5f6e2e3e771 > > > > > > 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" > > > > > > Are you planning to queue this somewhere? I think it makes sense regardless > > > of whether we change PowerPc or not and ideally it would be merged around > > > the same time as my relaxed atomics series. > > > > I have is in -rcu. By default, I will push it to the 4.4 merge window. > > Please let me know if you need it sooner. > > 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? Thanx, Paul