From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752193AbdARMPF (ORCPT ); Wed, 18 Jan 2017 07:15:05 -0500 Received: from LGEAMRELO11.lge.com ([156.147.23.51]:60783 "EHLO lgeamrelo11.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751734AbdARMPD (ORCPT ); Wed, 18 Jan 2017 07:15:03 -0500 X-Original-SENDERIP: 156.147.1.121 X-Original-MAILFROM: byungchul.park@lge.com X-Original-SENDERIP: 10.177.222.185 X-Original-MAILFROM: byungchul.park@lge.com From: "byungchul.park" To: "'Peter Zijlstra'" Cc: "'Boqun Feng'" , , , , , , , , , References: <1481260331-360-1-git-send-email-byungchul.park@lge.com> <1481260331-360-16-git-send-email-byungchul.park@lge.com> <20170118064230.GF15084@tardis.cn.ibm.com> <20170118105346.GL3326@X58A-UD3R> <20170118110317.GC6515@twins.programming.kicks-ass.net> <20170118115428.GM3326@X58A-UD3R> <20170118120757.GD6515@twins.programming.kicks-ass.net> In-Reply-To: <20170118120757.GD6515@twins.programming.kicks-ass.net> Subject: RE: [PATCH v4 15/15] lockdep: Crossrelease feature documentation Date: Wed, 18 Jan 2017 21:14:59 +0900 Message-ID: <008101d27184$7d3cbd00$77b63700$@lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Outlook 14.0 Thread-Index: AQIUng6axrHphDflJrI0ajjf/YIBSACqPJSyAk+M/2YCZwFCagGb8auaAgrCpFsCi6itmaBdMnlw Content-Language: ko Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > -----Original Message----- > From: Peter Zijlstra [mailto:peterz@infradead.org] > Sent: Wednesday, January 18, 2017 9:08 PM > To: Byungchul Park > Cc: Boqun Feng; mingo@kernel.org; tglx@linutronix.de; walken@google.com; > kirill@shutemov.name; linux-kernel@vger.kernel.org; linux-mm@kvack.org; > iamjoonsoo.kim@lge.com; akpm@linux-foundation.org; npiggin@gmail.com > Subject: Re: [PATCH v4 15/15] lockdep: Crossrelease feature documentation > > On Wed, Jan 18, 2017 at 08:54:28PM +0900, Byungchul Park wrote: > > On Wed, Jan 18, 2017 at 12:03:17PM +0100, Peter Zijlstra wrote: > > > On Wed, Jan 18, 2017 at 07:53:47PM +0900, Byungchul Park wrote: > > > > On Wed, Jan 18, 2017 at 02:42:30PM +0800, Boqun Feng wrote: > > > > > On Fri, Dec 09, 2016 at 02:12:11PM +0900, Byungchul Park wrote: > > > > > [...] > > > > > > +Example 1: > > > > > > + > > > > > > + CONTEXT X CONTEXT Y > > > > > > + --------- --------- > > > > > > + mutext_lock A > > > > > > + lock_page B > > > > > > + lock_page B > > > > > > + mutext_lock A /* DEADLOCK */ > > > > > > > > > > s/mutext_lock/mutex_lock > > > > > > > > Thank you. > > > > > > > > > > +Example 3: > > > > > > + > > > > > > + CONTEXT X CONTEXT Y > > > > > > + --------- --------- > > > > > > + mutex_lock A > > > > > > + mutex_lock A > > > > > > + mutex_unlock A > > > > > > + wait_for_complete B /* DEADLOCK */ > > > > > > > > > > I think this part better be: > > > > > > > > > > CONTEXT X CONTEXT Y > > > > > --------- --------- > > > > > mutex_lock A > > > > > mutex_lock A > > > > > wait_for_complete B /* DEADLOCK */ > > > > > mutex_unlock A > > > > > > > > > > , right? Because Y triggers DEADLOCK before X could run > mutex_unlock(). > > > > > > > > There's no different between two examples. > > > > > > There is.. > > > > > > > No matter which one is chosen, mutex_lock A in CONTEXT X cannot be > passed. > > > > > > But your version shows it does mutex_unlock() before CONTEXT Y does > > > wait_for_completion(). > > > > > > The thing about these diagrams is that both columns are assumed to > have > > > the same timeline. > > > > X cannot acquire mutex A because Y already acquired it. > > > > In order words, all statements below mutex_lock A in X cannot run. > > But your timeline shows it does, which is the error that Boqun pointed > out. I am sorry for not understanding what you are talking about. Do you mean that I should remove all statements below mutex_lock A in X? Or should I move mutex_unlock as Boqun said? What will change?