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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 80162C43145 for ; Sat, 23 Jun 2018 01:21:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 427FB24A7D for ; Sat, 23 Jun 2018 01:21:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 427FB24A7D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934616AbeFWBVL (ORCPT ); Fri, 22 Jun 2018 21:21:11 -0400 Received: from mail.kernel.org ([198.145.29.99]:43300 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933850AbeFWBVG (ORCPT ); Fri, 22 Jun 2018 21:21:06 -0400 Received: from gandalf.local.home (cpe-66-24-56-78.stny.res.rr.com [66.24.56.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 393B324A72; Sat, 23 Jun 2018 01:21:06 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.91) (envelope-from ) id 1fWXEf-0008Qh-7g; Fri, 22 Jun 2018 21:21:05 -0400 Message-Id: <20180623012105.136449195@goodmis.org> User-Agent: quilt/0.65 Date: Fri, 22 Jun 2018 21:20:37 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Linus Torvalds , Ingo Molnar , Andrew Morton , Peter Zijlstra , Ingo Molnar , Mathieu Desnoyers , Tom Zanussi , Namhyung Kim , Thomas Glexiner , Boqun Feng , Paul McKenney , Masami Hiramatsu , Todd Kjos , Erick Reyes , Julia Cartwright , Byungchul Park , stable@vger.kernel.org, "Joel Fernandes (Google)" Subject: [PATCH 2/5] softirq: Reorder trace_softirqs_on to prevent lockdep splat MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Disposition: inline; filename=0002-softirq-Reorder-trace_softirqs_on-to-prevent-lockdep.patch Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Joel Fernandes (Google)" I'm able to reproduce a lockdep splat with config options: CONFIG_PROVE_LOCKING=y, CONFIG_DEBUG_LOCK_ALLOC=y and CONFIG_PREEMPTIRQ_EVENTS=y $ echo 1 > /d/tracing/events/preemptirq/preempt_enable/enable [ 26.112609] DEBUG_LOCKS_WARN_ON(current->softirqs_enabled) [ 26.112636] WARNING: CPU: 0 PID: 118 at kernel/locking/lockdep.c:3854 [...] [ 26.144229] Call Trace: [ 26.144926] [ 26.145506] lock_acquire+0x55/0x1b0 [ 26.146499] ? __do_softirq+0x46f/0x4d9 [ 26.147571] ? __do_softirq+0x46f/0x4d9 [ 26.148646] trace_preempt_on+0x8f/0x240 [ 26.149744] ? trace_preempt_on+0x4d/0x240 [ 26.150862] ? __do_softirq+0x46f/0x4d9 [ 26.151930] preempt_count_sub+0x18a/0x1a0 [ 26.152985] __do_softirq+0x46f/0x4d9 [ 26.153937] irq_exit+0x68/0xe0 [ 26.154755] smp_apic_timer_interrupt+0x271/0x280 [ 26.156056] apic_timer_interrupt+0xf/0x20 [ 26.157105] The issue was this: preempt_count = 1 << SOFTIRQ_SHIFT __local_bh_enable(cnt = 1 << SOFTIRQ_SHIFT) { if (softirq_count() == (cnt && SOFTIRQ_MASK)) { trace_softirqs_on() { current->softirqs_enabled = 1; } } preempt_count_sub(cnt) { trace_preempt_on() { tracepoint() { rcu_read_lock_sched() { // jumps into lockdep Where preempt_count still has softirqs disabled, but current->softirqs_enabled is true, and we get a splat. Link: http://lkml.kernel.org/r/20180607201143.247775-1-joel@joelfernandes.org Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Linus Torvalds Cc: Mathieu Desnoyers Cc: Tom Zanussi Cc: Namhyung Kim Cc: Thomas Glexiner Cc: Boqun Feng Cc: Paul McKenney Cc: Masami Hiramatsu Cc: Todd Kjos Cc: Erick Reyes Cc: Julia Cartwright Cc: Byungchul Park Cc: stable@vger.kernel.org Reviewed-by: Steven Rostedt (VMware) Fixes: d59158162e032 ("tracing: Add support for preempt and irq enable/disable events") Signed-off-by: Joel Fernandes (Google) Signed-off-by: Steven Rostedt (VMware) --- kernel/softirq.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/softirq.c b/kernel/softirq.c index de2f57fddc04..900dcfee542c 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -139,9 +139,13 @@ static void __local_bh_enable(unsigned int cnt) { lockdep_assert_irqs_disabled(); + if (preempt_count() == cnt) + trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip()); + if (softirq_count() == (cnt & SOFTIRQ_MASK)) trace_softirqs_on(_RET_IP_); - preempt_count_sub(cnt); + + __preempt_count_sub(cnt); } /* -- 2.17.1