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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,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 354A1C0044D for ; Mon, 16 Mar 2020 15:01:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0C1FA2073C for ; Mon, 16 Mar 2020 15:01:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="PkRwHenX" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731821AbgCPPBR (ORCPT ); Mon, 16 Mar 2020 11:01:17 -0400 Received: from mail-qt1-f195.google.com ([209.85.160.195]:45517 "EHLO mail-qt1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731775AbgCPPBN (ORCPT ); Mon, 16 Mar 2020 11:01:13 -0400 Received: by mail-qt1-f195.google.com with SMTP id z8so11024185qto.12 for ; Mon, 16 Mar 2020 08:01:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=toDgRxGkv3Au9QraZzaLZxhTcUG6A8OuNPWq31a+tWs=; b=PkRwHenXC1sh5P6YofjVaT7LKOVV8z7J1aDn/2jT4HDuyut32E5bKrUkalswF9IRuP /lDL2EZQf6DQkgFTHHe7Dl/RD25L+sXC24B9tSug/pKtzfmNJKOnkEDBrXpfVkXM0xaC WI03IfjTn8z5GM0o++tlHYVIrFjP7nGJdThsQ= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=toDgRxGkv3Au9QraZzaLZxhTcUG6A8OuNPWq31a+tWs=; b=ZtF4YrEZGoLe+0Se1hI+xYvGdBwTJu6KyTQH7GwPYr/HJZpziq6AlwS5GSr+UZerFN 2HKZocPexM/k9cckihmoUDwICJvwD0S1d/aZDoWNZsE9Up9/EnGVXpjuHJ7RZYY0g6hn d1swh1HIoRa9lA5E0iGQcx9wayz5scCP2RvRMWG+C7cH+fuZtTrpaRxazpmREknAkGKD 9HlFKZ3sqdhQjCPe9pheQevQF9qyUN1bC31U/Nw9zJ7oS84UviZv8Co/E2uUtUt6txM2 ZgIgpaesxUaqKmmMCdUyTY8kAgVTWiBgoyMEnmV9CjfsQtAARvWLnqCJoHVxSImcOZZn F39w== X-Gm-Message-State: ANhLgQ3TulVwwMP5ncwbcHsw/Q81dPw/ikHQgIz8To5bhcNXdnzcn8E8 iOatNFHxRwIP0oeLt2CdmNRymA== X-Google-Smtp-Source: ADFU+vvJFwFt9cBgLtR8fCszl78b95Z+5RabLU2VNLX1UaPszxBnI0lJnRSvBlXkhyGKePUrD4aU/g== X-Received: by 2002:ac8:2f23:: with SMTP id j32mr514513qta.120.1584370871758; Mon, 16 Mar 2020 08:01:11 -0700 (PDT) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id d72sm15615874qkc.88.2020.03.16.08.01.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 16 Mar 2020 08:01:11 -0700 (PDT) Date: Mon, 16 Mar 2020 11:01:10 -0400 From: Joel Fernandes To: Peter Zijlstra 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: <20200316150110.GB134626@google.com> References: <20200312151258.128036-1-boqun.feng@gmail.com> <20200313093325.GW12561@hirez.programming.kicks-ass.net> <20200315010422.GA134626@google.com> <20200316135507.GF12561@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200316135507.GF12561@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.12.2 (2019-09-21) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 16, 2020 at 02:55:07PM +0100, Peter Zijlstra wrote: > 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. Makes sense, thank you Peter. - Joel