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=-5.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 E335AC433DF for ; Fri, 29 May 2020 22:25:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B95AE2065F for ; Fri, 29 May 2020 22:25:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="As730tVr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728379AbgE2WZU (ORCPT ); Fri, 29 May 2020 18:25:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58376 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726857AbgE2WZT (ORCPT ); Fri, 29 May 2020 18:25:19 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 969B9C03E969 for ; Fri, 29 May 2020 15:25:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=EAQtx8ywsa1fD3NzR5GGh84KBN25dRPzifCzFwNJPHg=; b=As730tVrSxRaA4+GmFkdcV2jjs NYY/O9CQTWtgXX9qmY1htY15TQzkzZTQ0GBVCvJdhczJzB0ddXR1WgkMDtRZOWooLXksiOaQTQnz1 EHcYOcupzgUdd4NXhXwJ7k8jDF53Egc0V6M3MAmVzFa9DBXccMEtw5v0HgDlpd+FXjrzm0SWb7xSJ 71ZqIzkQN0vc8I5mtmokVhHLwq4L9DyZozQF6bkaAgeFU+oT1VaQIt1H+xAZ/JvtcbzVCp7bg9yVe a6aaKdQQeXZ5Pppn2jqEESr0wnLzbFTTVgEs+XoWwLzOEnh67x7S5i1udGgZCZ6N2E2QhxN0RPMuD Oi/8EnBA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jenR6-0008Dt-7v; Fri, 29 May 2020 22:25:08 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id B46089834CF; Sat, 30 May 2020 00:25:05 +0200 (CEST) Date: Sat, 30 May 2020 00:25:05 +0200 From: Peter Zijlstra To: Steven Rostedt Cc: tglx@linutronix.de, luto@amacapital.net, linux-kernel@vger.kernel.org, x86@kernel.org, Lai Jiangshan , sean.j.christopherson@intel.com, andrew.cooper3@citrix.com, daniel.thompson@linaro.org, a.darwish@linutronix.de, bigeasy@linutronix.de Subject: Re: [PATCH 13/14] lockdep: Prepare for NMI IRQ state tracking Message-ID: <20200529222505.GW2483@worktop.programming.kicks-ass.net> References: <20200529212728.795169701@infradead.org> <20200529213321.471984676@infradead.org> <20200529181401.1f01bdc5@oasis.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200529181401.1f01bdc5@oasis.local.home> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 29, 2020 at 06:14:01PM -0400, Steven Rostedt wrote: > On Fri, 29 May 2020 23:27:41 +0200 > Peter Zijlstra wrote: > > > There is no reason not to always, accurately, track IRQ state. > > > > This change also makes IRQ state tracking ignore lockdep_off(). > > > > Signed-off-by: Peter Zijlstra (Intel) > > --- > > kernel/locking/lockdep.c | 33 ++++++++++++++++++++++++++++++--- > > 1 file changed, 30 insertions(+), 3 deletions(-) > > > > --- a/kernel/locking/lockdep.c > > +++ b/kernel/locking/lockdep.c > > @@ -3646,7 +3646,13 @@ static void __trace_hardirqs_on_caller(v > > */ > > void lockdep_hardirqs_on_prepare(unsigned long ip) > > { > > - if (unlikely(!debug_locks || current->lockdep_recursion)) > > Why remove the check for debug_locks? Isn't that there to disable > everything at once to prevent more warnings to be printed? Yeah, maybe. I was thinking we could keep IRQ state running. But you're right, if we mess up the IRQ state itself this might generate a wee mess. > Also, isn't there other ways that we could have recursion besides NMIs? > Say we do a printk inside here, or call something that may also enable > interrupts? I thought the recursion check was also to prevent lockdep > infrastructure calling something that lockdep monitors being a problem? > > Or am I missing something? > > + /* > > + * NMIs do not (and cannot) track lock dependencies, nothing to do. > > + */ > > + if (in_nmi()) > > + return; > > + > > + if (DEBUG_LOCKS_WARN_ON(current->lockdep_recursion & LOCKDEP_RECURSION_MASK)) > > return; ^^ there's your regular recursion check.