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 X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 55F98C433DF for ; Tue, 26 May 2020 09:46:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 372F9207CB for ; Tue, 26 May 2020 09:46:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731823AbgEZJqC (ORCPT ); Tue, 26 May 2020 05:46:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59050 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728686AbgEZJqC (ORCPT ); Tue, 26 May 2020 05:46:02 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 08288C03E97E for ; Tue, 26 May 2020 02:46:02 -0700 (PDT) Received: from [5.158.153.53] (helo=debian-buster-darwi.lab.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.80) (envelope-from ) id 1jdW9I-0000j2-Ha; Tue, 26 May 2020 11:45:28 +0200 Date: Tue, 26 May 2020 11:45:26 +0200 From: "Ahmed S. Darwish" To: Peter Zijlstra Cc: "Sebastian A. Siewior" , Ingo Molnar , Will Deacon , Thomas Gleixner , "Paul E. McKenney" , Steven Rostedt , LKML Subject: Re: [PATCH v1 07/25] lockdep: Add preemption disabled assertion API Message-ID: <20200526094526.GA428152@debian-buster-darwi.lab.linutronix.de> References: <20200519214547.352050-1-a.darwish@linutronix.de> <20200519214547.352050-8-a.darwish@linutronix.de> <20200522175503.GQ325280@hirez.programming.kicks-ass.net> <20200523145942.vjk3z6pbj6yicqa4@linutronix.de> <20200523224132.GD2483@worktop.programming.kicks-ass.net> <20200525102241.GF325303@hirez.programming.kicks-ass.net> <20200526005231.GA377571@debian-buster-darwi.lab.linutronix.de> <20200526081350.GI317569@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200526081350.GI317569@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 26, 2020 at 10:13:50AM +0200, Peter Zijlstra wrote: > On Tue, May 26, 2020 at 02:52:31AM +0200, Ahmed S. Darwish wrote: > > Peter Zijlstra wrote: > > > > +#define lockdep_assert_irqs_enabled() \ > > > +do { \ > > > + WARN_ON_ONCE(debug_locks && !this_cpu_read(hardirqs_enabled)); \ > > > +} while (0) > > > > > > > Given that lockdep_off() is defined at lockdep.c as: > > > > void lockdep_off(void) > > { > > current->lockdep_recursion += LOCKDEP_OFF; > > } > > > > This would imply that all of the macros: > > > > - lockdep_assert_irqs_enabled() > > - lockdep_assert_irqs_disabled() > > - lockdep_assert_in_irq() > > - lockdep_assert_preemption_disabled() > > - lockdep_assert_preemption_enabled() > > > > will do the lockdep checks *even if* lockdep_off() was called. > > > > This doesn't sound right. Even if all of the above macros call sites > > didn't care about lockdep_off()/on(), it is semantically incoherent. > > lockdep_off() is an abomination and really should not exist. > > That dm-cache-target.c thing, for example, is atrocious shite that will > explode on -rt. Whoever wrote that needs a 'medal'. > > People using it deserve all the pain they get. > > Also; IRQ state _should_ be tracked irrespective of tracking lock > dependencies -- I see that that currently isn't entirely the case, lemme > go fix that. > Exactly, currently all the lockdep IRQ checks gets nullified if lockdep_off() is called. That was the source of my confusion. If you'll have any extra patches on this, I can also queue them in the next iteration of this series, before this patch. Thanks a lot, -- Ahmed S. Darwish Linutronix GmbH