From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752527AbdJKRGi (ORCPT ); Wed, 11 Oct 2017 13:06:38 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:53078 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751710AbdJKRGh (ORCPT ); Wed, 11 Oct 2017 13:06:37 -0400 Date: Wed, 11 Oct 2017 10:06:31 -0700 From: "Paul E. McKenney" To: Peter Zijlstra Cc: David Howells , Will Deacon , linux-kernel@vger.kernel.org, mingo@kernel.org, torvalds@linux-foundation.org, mark.rutland@arm.com, linux-arch@vger.kernel.org, Jonathan Corbet , Alexander Kuleshov , dvyukov@google.com Subject: Re: [PATCH RFC tip/core/rcu 12/15] lib/assoc_array: Remove smp_read_barrier_depends() Reply-To: paulmck@linux.vnet.ibm.com References: <1507594969-8347-12-git-send-email-paulmck@linux.vnet.ibm.com> <20171010001951.GA6476@linux.vnet.ibm.com> <8079.1507628146@warthog.procyon.org.uk> <26455.1507724399@warthog.procyon.org.uk> <6309.1507735045@warthog.procyon.org.uk> <20171011155948.GE3521@linux.vnet.ibm.com> <20171011161220.zqkdhynxerrcmvdd@hirez.programming.kicks-ass.net> <20171011162412.o6lmjiag7spwabge@hirez.programming.kicks-ass.net> <20171011164748.GK3521@linux.vnet.ibm.com> <20171011165405.xd4xfa2x3dcz4e57@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171011165405.xd4xfa2x3dcz4e57@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 17101117-0044-0000-0000-0000039E1A16 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007878; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000236; SDB=6.00929672; UDB=6.00467930; IPR=6.00709943; BA=6.00005634; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00017492; XFM=3.00000015; UTC=2017-10-11 17:06:34 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17101117-0045-0000-0000-000007CD1BC9 Message-Id: <20171011170631.GN3521@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-10-11_06:,, 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=8.0.1-1707230000 definitions=main-1710110237 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 11, 2017 at 06:54:05PM +0200, Peter Zijlstra wrote: > On Wed, Oct 11, 2017 at 09:47:48AM -0700, Paul E. McKenney wrote: > > Interesting. Do we currently have any dependencies headed by > > this_cpu_read()? > > Nope, but almost, look for: cpufreq_update_util_data. This, you mean? data = rcu_dereference_sched(*this_cpu_ptr(&cpufreq_update_util_data)); True, a non-RCU dependency use case would want to use ACCESS_ONCE() in the new regime. Thanx, Paul