From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753245AbdHKOja (ORCPT ); Fri, 11 Aug 2017 10:39:30 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:36228 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753201AbdHKOj3 (ORCPT ); Fri, 11 Aug 2017 10:39:29 -0400 Date: Fri, 11 Aug 2017 07:39:17 -0700 From: "Paul E. McKenney" To: Peter Zijlstra Cc: Stephen Rothwell , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Linux-Next Mailing List , Linux Kernel Mailing List Subject: Re: linux-next: build failure after merge of the rcu tree Reply-To: paulmck@linux.vnet.ibm.com References: <20170811144352.585085e2@canb.auug.org.au> <20170811045453.GB3730@linux.vnet.ibm.com> <20170811091434.h6mkuuw3zcgkzg26@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170811091434.h6mkuuw3zcgkzg26@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 17081114-0044-0000-0000-0000037BD957 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007525; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000220; SDB=6.00900793; UDB=6.00451010; IPR=6.00680995; BA=6.00005522; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00016647; XFM=3.00000015; UTC=2017-08-11 14:39:19 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17081114-0045-0000-0000-000007A9EED8 Message-Id: <20170811143917.GD3730@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-08-11_07:,, 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=8.0.1-1706020000 definitions=main-1708110236 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 11, 2017 at 11:14:34AM +0200, Peter Zijlstra wrote: > On Thu, Aug 10, 2017 at 09:54:53PM -0700, Paul E. McKenney wrote: > > On Fri, Aug 11, 2017 at 02:43:52PM +1000, Stephen Rothwell wrote: > > > > Looks like I need to rebase my patch on top of a9668cd6ee28, and > > than put an smp_mb__after_spinlock() between the lock and the unlock. > > > > Peter, any objections to that approach? Other suggestions? > > Hurm.. I'll have to try and understand that comment there again it > seems. My reasoning is as follows: 1. The critical section is empty, so any prior references would be ordered only against later critical sections. 2. A full barrier within the critical section will order those prior references against later critical sections just as easily as would one prior to the critical section. Does that make sense, I should I have stayed away from the keyboard at this early hour? ;-) Thanx, Paul