From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751402AbdAOTph (ORCPT ); Sun, 15 Jan 2017 14:45:37 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:33813 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751223AbdAOTpg (ORCPT ); Sun, 15 Jan 2017 14:45:36 -0500 Date: Sun, 15 Jan 2017 11:45:26 -0800 From: "Paul E. McKenney" To: Ingo Molnar 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 Reply-To: paulmck@linux.vnet.ibm.com References: <20170114091941.GA22961@linux.vnet.ibm.com> <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170115094058.GB28621@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 17011519-0024-0000-0000-000015B3D0BE X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00006439; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000199; SDB=6.00808020; UDB=6.00393473; IPR=6.00585377; BA=6.00005056; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00013928; XFM=3.00000011; UTC=2017-01-15 19:45:33 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17011519-0025-0000-0000-000047F71CEE Message-Id: <20170115194526.GH5238@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-01-15_14:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1612050000 definitions=main-1701150297 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? Thanx, Paul