Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751828AbdIAJsA (ORCPT ); Fri, 1 Sep 2017 05:48:00 -0400 Received: from merlin.infradead.org ([205.233.59.134]:52708 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751676AbdIAJr7 (ORCPT ); Fri, 1 Sep 2017 05:47:59 -0400 Date: Fri, 1 Sep 2017 11:47:47 +0200 From: Peter Zijlstra 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 Message-ID: <20170901094747.iv6s532ccuuzpry2@hirez.programming.kicks-ass.net> References: <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> <20170831080442.5vdgoaijzmrc776x@hirez.programming.kicks-ass.net> <20170831081501.GJ3240@X58A-UD3R> <20170831083453.5tfjofzk7idthsof@hirez.programming.kicks-ass.net> <20170901020512.GK3240@X58A-UD3R> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170901020512.GK3240@X58A-UD3R> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1062 Lines: 30 On Fri, Sep 01, 2017 at 11:05:12AM +0900, Byungchul Park wrote: > On Thu, Aug 31, 2017 at 10:34:53AM +0200, Peter Zijlstra wrote: > > On Thu, Aug 31, 2017 at 05:15:01PM +0900, Byungchul Park wrote: > > > It's not important. Ok, check the following, instead: > > > > > > context X context Y > > > --------- --------- > > > wait_for_completion(C) > > > acquire(A) > > > release(A) > > > process_one_work() > > > acquire(B) > > > release(B) > > > work->fn() > > > complete(C) > > > > > > We don't need to lose C->A and C->B dependencies unnecessarily. > > > > I really can't be arsed about them. Its really only the first few works > > that will retain that dependency anyway, even if you were to retain > > them. > > Wrong. > > Every 'work' doing complete() for different classes of completion > variable suffers from losing valuable dependencies, every time, not > first few ones. The moment you overrun the history array its gone. So yes, only the first few works will ever see them