Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751450AbdHaH0n (ORCPT ); Thu, 31 Aug 2017 03:26:43 -0400 Received: from LGEAMRELO13.lge.com ([156.147.23.53]:54380 "EHLO lgeamrelo13.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750908AbdHaH0l (ORCPT ); Thu, 31 Aug 2017 03:26:41 -0400 X-Original-SENDERIP: 156.147.1.127 X-Original-MAILFROM: byungchul.park@lge.com X-Original-SENDERIP: 10.177.222.33 X-Original-MAILFROM: byungchul.park@lge.com Date: Thu, 31 Aug 2017 16:26:38 +0900 From: Byungchul Park To: "'Peter Zijlstra'" Cc: mingo@kernel.org, tj@kernel.org, boqun.feng@gmail.com, david@fromorbit.com, johannes@sipsolutions.net, oleg@redhat.com, linux-kernel@vger.kernel.org, kernel-team@lge.com Subject: Re: [PATCH 4/4] lockdep: Fix workqueue crossrelease annotation Message-ID: <20170831072637.GI3240@X58A-UD3R> References: <20170824140240.t4imrpvussebfimm@hirez.programming.kicks-ass.net> <20170825011114.GA3858@X58A-UD3R> <20170829085939.ggmb6xiohw67micb@hirez.programming.kicks-ass.net> <20170830020953.GE3240@X58A-UD3R> <20170830074117.GG3240@X58A-UD3R> <20170830085333.GM32112@worktop.programming.kicks-ass.net> <004601d3216e$a3702030$ea506090$@lge.com> <20170830091223.xxnh3podtcumlabm@hirez.programming.kicks-ass.net> <004701d32171$ce57d4c0$6b077e40$@lge.com> <20170830112546.GH3240@X58A-UD3R> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170830112546.GH3240@X58A-UD3R> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1978 Lines: 49 On Wed, Aug 30, 2017 at 08:25:46PM +0900, Byungchul Park wrote: > On Wed, Aug 30, 2017 at 06:24:39PM +0900, Byungchul Park wrote: > > > -----Original Message----- > > > From: Peter Zijlstra [mailto:peterz@infradead.org] > > > Sent: Wednesday, August 30, 2017 6:12 PM > > > To: Byungchul Park > > > Cc: mingo@kernel.org; tj@kernel.org; boqun.feng@gmail.com; > > > david@fromorbit.com; johannes@sipsolutions.net; oleg@redhat.com; linux- > > > kernel@vger.kernel.org; kernel-team@lge.com > > > Subject: Re: [PATCH 4/4] lockdep: Fix workqueue crossrelease annotation > > > > > > On Wed, Aug 30, 2017 at 06:01:59PM +0900, Byungchul Park wrote: > > > > My point is that we inevitably lose valuable dependencies by yours. > > > That's > > > > why I've endlessly asked you 'do you have any reason you try those > > > patches?' > > > > a ton of times. And you have never answered it. > > > > > > The only dependencies that are lost are those between the first work and > > > the setup of the workqueue thread. > > > > > > And there obviously _should_ not be any dependencies between those. A > > > > 100% right. Since there obviously should not be any, it would be better > > to check them. So I've endlessly asked you 'do you have any reason removing > > the opportunity for that check?'. Overhead? Logical problem? Or want to > > believe workqueue setup code perfect forever? I mean, is it a problem if we > > check them? > > > > > work should not depend on the setup of the thread. > > > > 100% right. > > For example - I'm giving you the same example repeatedly: > > context X context Y > --------- --------- > wait_for_completion(C) > acquire(A) > process_one_work() > acquire(B) > work->fn() > complete(C) > > Please let lockdep check C->A and C->B. You always stop answering whenever I ask you for opinion with this example. I'm really curious. Could you let me know your opinion about this example?