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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 E4F12C18E5B for ; Mon, 16 Mar 2020 13:55:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BA3D02051A for ; Mon, 16 Mar 2020 13:55:13 +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="G42P68L1" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731411AbgCPNzN (ORCPT ); Mon, 16 Mar 2020 09:55:13 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:48928 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731110AbgCPNzN (ORCPT ); Mon, 16 Mar 2020 09:55:13 -0400 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=WEBG3nIg5bRO/ndpNpdjvppQegv8JGgyyt7RDg3n9BA=; b=G42P68L1AVx/huDT3DLmA5JN+R T9nK0j8g2tIhO+d+7Kq90Oabd+k2yKREMXg4WYN1OrgaB7okGszUsGuSn/OEjIFY2Qf6qAsnr4lHE gnut877TQ4yK4893v0WhkXkigpKr2NlBpIZygt/mmbGcKoMnsiXHnk+hFHrO6XG0WzmVhWcKkL/mD klD0+jzJF4ttIx932LKWpLPPRNswCysyDAD6vr/tZ3uDWqw1UaO58gK7k93FAU6IK7JfE93lpcPTt 2CcZGdh+piCS5+Uf/3xe5N/TNWjbtPH1EdD7jnlFmnht8D33wSrnAm6UKjgF1bsLmsfSJ5sgLVMaA vqrRm3GQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jDqCz-0007ub-Qa; Mon, 16 Mar 2020 13:55:09 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id F3B7530138D; Mon, 16 Mar 2020 14:55:07 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id DE7B820B16492; Mon, 16 Mar 2020 14:55:07 +0100 (CET) Date: Mon, 16 Mar 2020 14:55:07 +0100 From: Peter Zijlstra To: Joel Fernandes Cc: Boqun Feng , linux-kernel@vger.kernel.org, rcu@vger.kernel.org, "Paul E. McKenney" , Madhuparna Bhowmik , Qian Cai , Ingo Molnar , Will Deacon Subject: Re: [PATCH] locking/lockdep: Avoid recursion in lockdep_count_{for,back}ward_deps() Message-ID: <20200316135507.GF12561@hirez.programming.kicks-ass.net> References: <20200312151258.128036-1-boqun.feng@gmail.com> <20200313093325.GW12561@hirez.programming.kicks-ass.net> <20200315010422.GA134626@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200315010422.GA134626@google.com> Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Sat, Mar 14, 2020 at 09:04:22PM -0400, Joel Fernandes wrote: > On Fri, Mar 13, 2020 at 10:33:25AM +0100, Peter Zijlstra wrote: > Thanks Peter and Boqun, the below patch makes sense to me. Just had some nits > below, otherwise: > > @@ -1719,11 +1725,11 @@ unsigned long lockdep_count_forward_deps > > this.class = class; > > > > raw_local_irq_save(flags); > > - current->lockdep_recursion = 1; > > + current->lockdep_recursion++; > > arch_spin_lock(&lockdep_lock); > > ret = __lockdep_count_forward_deps(&this); > > arch_spin_unlock(&lockdep_lock); > > - current->lockdep_recursion = 0; > > + current->lockdep_recursion--; > > This doesn't look like it should recurse. Why not just use the > lockdep_recursion_finish() helper here? I chose to only add that to the sites that check recursion on entry.