Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752375AbdLSQyq (ORCPT ); Tue, 19 Dec 2017 11:54:46 -0500 Received: from aserp2120.oracle.com ([141.146.126.78]:48032 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751685AbdLSQym (ORCPT ); Tue, 19 Dec 2017 11:54:42 -0500 Subject: Re: [PATCH] lockdep: Show up to three levels for a deadlock scenario To: Steven Rostedt , Peter Zijlstra Cc: LKML , Ingo Molnar , Thomas Gleixner , Andrew Morton References: <20171214123852.515257aa@gandalf.local.home> <20171214175931.mlvr7lk7bcnsqu5i@hirez.programming.kicks-ass.net> <3317dd1a-1a39-3295-eb90-538be296dff8@oracle.com> <20171219164619.ehrsqvqajj4n6wr6@hirez.programming.kicks-ass.net> <20171219115238.03dc992c@gandalf.local.home> From: Dhaval Giani Message-ID: Date: Tue, 19 Dec 2017 11:54:10 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 MIME-Version: 1.0 In-Reply-To: <20171219115238.03dc992c@gandalf.local.home> Content-Type: text/plain; charset=utf-8 Content-Language: en-CA Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8750 signatures=668650 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=862 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1712190240 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 824 Lines: 26 On 2017-12-19 11:52 AM, Steven Rostedt wrote: > On Tue, 19 Dec 2017 17:46:19 +0100 > Peter Zijlstra wrote: > > >> It really isn't that hard, Its mostly a question of TL;DR. >> >> #0 is useless and should be thrown out >> #1 shows where we take #1 while holding #0 >> .. >> #n shows where we take #n while holding #n-1 >> >> And the bottom callstack shows where we take #0 while holding #n. Which >> gets you a nice circle in your graph, which spells deadlock. >> >> Plenty people have shown they get this stuff. > > > Then I suggest that you can either take my patch to improve the > visual or remove the visual completely, as nobody cares about it. > I prefer the former. As Steven has mentioned elsewhere, people find lockdep output hard to follow (enough that he has given talks :) ) Dhaval