From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751294AbdAPG4z (ORCPT ); Mon, 16 Jan 2017 01:56:55 -0500 Received: from mail-wm0-f67.google.com ([74.125.82.67]:36384 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751112AbdAPG4x (ORCPT ); Mon, 16 Jan 2017 01:56:53 -0500 Date: Mon, 16 Jan 2017 07:56:47 +0100 From: Ingo Molnar To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com, will.deacon@arm.com, boqun.feng@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org, Peter Zijlstra Subject: Re: [PATCH tip/core/rcu 2/3] srcu: Force full grace-period ordering Message-ID: <20170116065647.GA29538@gmail.com> References: <1484385601-23379-2-git-send-email-paulmck@linux.vnet.ibm.com> <20170114093550.GB14970@gmail.com> <20170114195417.GW5238@linux.vnet.ibm.com> <20170114214159.GA7098@linux.vnet.ibm.com> <20170115071123.GB26581@gmail.com> <20170115074034.GE5238@linux.vnet.ibm.com> <20170115075711.GA19506@gmail.com> <20170115092454.GF5238@linux.vnet.ibm.com> <20170115094058.GB28621@gmail.com> <20170115194526.GH5238@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170115194526.GH5238@linux.vnet.ibm.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Paul E. McKenney wrote: > On Sun, Jan 15, 2017 at 10:40:58AM +0100, Ingo Molnar wrote: > > > > * Paul E. McKenney wrote: > > > > > > [sounds of rummaging around in the Git tree] > > > > > > > > I found this commit of yours from ancient history (more than a year ago!): > > > > > > > > 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" > > > > > > > > So I concur and I'm fine with your patch - or with the status quo code as well. > > > > > > I already have the patch queued, so how about I keep it if I get an ack > > > from the powerpc guys and drop it otherwise? > > > > Yeah, sounds good! Your patch made me look up 'RelAcq' so it has documentation > > value as well ;-) > > ;-) ;-) ;-) > > Looking forward, my guess would be that if some other code needs > smp_mb__after_unlock_lock() or if some other architecture needs > non-smb_mb() special handling, I should consider making it work the > same as smp_mb__after_atomic() and friends. Does that seem like a > reasonable thought? Yeah, absolutely - it's just that the pattern triggered the 'this looks a bit too specialized' response in me, but after seeing the details (again ...) I agree that this time is different! Thanks, Ingo