From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 02ED9C433EF for ; Mon, 9 May 2022 20:47:22 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 30E306B0072; Mon, 9 May 2022 16:47:22 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2BBF76B0073; Mon, 9 May 2022 16:47:22 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 184C56B0074; Mon, 9 May 2022 16:47:22 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 0A8DA6B0072 for ; Mon, 9 May 2022 16:47:22 -0400 (EDT) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay12.hostedemail.com (Postfix) with ESMTP id D54CA121295 for ; Mon, 9 May 2022 20:47:21 +0000 (UTC) X-FDA: 79447389882.14.47FB6B0 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf06.hostedemail.com (Postfix) with ESMTP id 35C8C180062 for ; Mon, 9 May 2022 20:47:19 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 700A3616FF; Mon, 9 May 2022 20:47:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7A498C385BA; Mon, 9 May 2022 20:47:14 +0000 (UTC) Date: Mon, 9 May 2022 16:47:12 -0400 From: Steven Rostedt To: Byungchul Park Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>, torvalds@linux-foundation.org, damien.lemoal@opensource.wdc.com, linux-ide@vger.kernel.org, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, mingo@redhat.com, linux-kernel@vger.kernel.org, peterz@infradead.org, will@kernel.org, tglx@linutronix.de, joel@joelfernandes.org, sashal@kernel.org, daniel.vetter@ffwll.ch, chris@chris-wilson.co.uk, duyuyang@gmail.com, johannes.berg@intel.com, tj@kernel.org, tytso@mit.edu, willy@infradead.org, david@fromorbit.com, amir73il@gmail.com, gregkh@linuxfoundation.org, kernel-team@lge.com, linux-mm@kvack.org, akpm@linux-foundation.org, mhocko@kernel.org, minchan@kernel.org, hannes@cmpxchg.org, vdavydov.dev@gmail.com, sj@kernel.org, jglisse@redhat.com, dennis@kernel.org, cl@linux.com, penberg@kernel.org, rientjes@google.com, vbabka@suse.cz, ngupta@vflare.org, linux-block@vger.kernel.org, paolo.valente@linaro.org, josef@toxicpanda.com, linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk, jack@suse.cz, jack@suse.com, jlayton@kernel.org, dan.j.williams@intel.com, hch@infradead.org, djwong@kernel.org, dri-devel@lists.freedesktop.org, airlied@linux.ie, rodrigosiqueiramelo@gmail.com, melissa.srw@gmail.com, hamohammed.sa@gmail.com Subject: Re: [PATCH RFC v6 00/21] DEPT(Dependency Tracker) Message-ID: <20220509164712.746e236b@gandalf.local.home> In-Reply-To: <20220509001637.GA6047@X58A-UD3R> References: <1651795895-8641-1-git-send-email-byungchul.park@lge.com> <20220509001637.GA6047@X58A-UD3R> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: sykdoihr68m5g5wq3acacu4t158ikrz3 X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 35C8C180062 Authentication-Results: imf06.hostedemail.com; dkim=none; spf=pass (imf06.hostedemail.com: domain of "SRS0=bAvH=VR=goodmis.org=rostedt@kernel.org" designates 139.178.84.217 as permitted sender) smtp.mailfrom="SRS0=bAvH=VR=goodmis.org=rostedt@kernel.org"; dmarc=none X-Rspam-User: X-HE-Tag: 1652129239-471702 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, 9 May 2022 09:16:37 +0900 Byungchul Park wrote: > CASE 2. > > lock L with depth n > lock A > lock_nested L' with depth n + 1 > ... > unlock L' > unlock A > unlock L > > This case is allowed by Lockdep. > This case is *NOT* allowed by DEPT cuz it's a *DEADLOCK*. > > --- > > The following scenario would explain why CASE 2 is problematic. > > THREAD X THREAD Y > > lock L with depth n > lock L' with depth n > lock A > lock A > lock_nested L' with depth n + 1 I'm confused by what exactly you are saying is a deadlock above. Are you saying that lock A and L' are inversed? If so, lockdep had better detect that regardless of L. A nested lock associates the the nesting with the same type of lock. That is, in lockdep nested tells lockdep not to trigger on the L and L' but it will not ignore that A was taken. -- Steve > lock_nested L'' with depth n + 1 > ... ... > unlock L' unlock L'' > unlock A unlock A > unlock L unlock L'