From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932564AbdJJP5A (ORCPT ); Tue, 10 Oct 2017 11:57:00 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:51798 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932401AbdJJP45 (ORCPT ); Tue, 10 Oct 2017 11:56:57 -0400 Date: Tue, 10 Oct 2017 08:56:50 -0700 From: "Paul E. McKenney" To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, torvalds@linux-foundation.org, mark.rutland@arm.com, dhowells@redhat.com, linux-arch@vger.kernel.org, will.deacon@arm.com, Pablo Neira Ayuso , Jozsef Kadlecsik , Florian Westphal , "David S. Miller" , netfilter-devel@vger.kernel.org, coreteam@netfilter.org, netdev@vger.kernel.org Subject: Re: [PATCH RFC tip/core/rcu 14/15] netfilter: Remove now-redundant smp_read_barrier_depends() Reply-To: paulmck@linux.vnet.ibm.com References: <20171010001951.GA6476@linux.vnet.ibm.com> <1507594969-8347-14-git-send-email-paulmck@linux.vnet.ibm.com> <20171010084334.nbyhryiwyrl6km4u@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171010084334.nbyhryiwyrl6km4u@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 17101015-0044-0000-0000-0000039D7B07 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007873; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000235; SDB=6.00929168; UDB=6.00467653; IPR=6.00709439; BA=6.00005632; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00017476; XFM=3.00000015; UTC=2017-10-10 15:56:55 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17101015-0045-0000-0000-000007CC7BDB Message-Id: <20171010155650.GF3521@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-10-10_05:,, 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-1710100225 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 10, 2017 at 10:43:34AM +0200, Peter Zijlstra wrote: > On Mon, Oct 09, 2017 at 05:22:48PM -0700, Paul E. McKenney wrote: > > READ_ONCE() now implies smp_read_barrier_depends(), which means that > > the instances in arpt_do_table(), ipt_do_table(), and ip6t_do_table() > > are now redundant. This commit removes them and adjusts the comments. > > Similar to the previous patch, the lack of READ_ONCE() in the original > code is a pre-existing bug. It would allow the compiler to tear the load > and observe a composite of two difference pointer values, or reload the > private pointer and result in table_base and jumpstacl being part of > different objects. > > It would be good to point out this actually fixes a bug in the code. Assuming that these changes actually fixed something, agreed. ;-) Thanx, Paul