From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752190AbdGFQUd (ORCPT ); Thu, 6 Jul 2017 12:20:33 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:48208 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751813AbdGFQUa (ORCPT ); Thu, 6 Jul 2017 12:20:30 -0400 Date: Thu, 6 Jul 2017 09:20:24 -0700 From: "Paul E. McKenney" To: Peter Zijlstra Cc: David Laight , "linux-kernel@vger.kernel.org" , "netfilter-devel@vger.kernel.org" , "netdev@vger.kernel.org" , "oleg@redhat.com" , "akpm@linux-foundation.org" , "mingo@redhat.com" , "dave@stgolabs.net" , "manfred@colorfullife.com" , "tj@kernel.org" , "arnd@arndb.de" , "linux-arch@vger.kernel.org" , "will.deacon@arm.com" , "stern@rowland.harvard.edu" , "parri.andrea@gmail.com" , "torvalds@linux-foundation.org" Subject: Re: [PATCH v2 0/9] Remove spin_unlock_wait() Reply-To: paulmck@linux.vnet.ibm.com References: <20170629235918.GA6445@linux.vnet.ibm.com> <20170705232955.GA15992@linux.vnet.ibm.com> <063D6719AE5E284EB5DD2968C1650D6DD0033F01@AcuExch.aculab.com> <20170706160555.xc63yydk77gmttae@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170706160555.xc63yydk77gmttae@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 17070616-0036-0000-0000-00000241A708 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007331; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000214; SDB=6.00883737; UDB=6.00440899; IPR=6.00663924; BA=6.00005455; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00016115; XFM=3.00000015; UTC=2017-07-06 16:20:29 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17070616-0037-0000-0000-000040FEFC5F Message-Id: <20170706162024.GD2393@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-07-06_10:,, 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=8.0.1-1703280000 definitions=main-1707060280 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 06, 2017 at 06:05:55PM +0200, Peter Zijlstra wrote: > On Thu, Jul 06, 2017 at 02:12:24PM +0000, David Laight wrote: > > From: Paul E. McKenney [ . . . ] > Now on the one hand I feel like Oleg that it would be a shame to loose > the optimization, OTOH this thing is really really tricky to use, > and has lead to a number of bugs already. I do agree, it is a bit sad to see these optimizations go. So, should this make mainline, I will be tagging the commits that spin_unlock_wait() so that they can be easily reverted should someone come up with good semantics and a compelling use case with compelling performance benefits. Thanx, Paul