From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759247AbYHOOby (ORCPT ); Fri, 15 Aug 2008 10:31:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756335AbYHOObq (ORCPT ); Fri, 15 Aug 2008 10:31:46 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:42394 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753296AbYHOObp (ORCPT ); Fri, 15 Aug 2008 10:31:45 -0400 Date: Fri, 15 Aug 2008 16:24:30 +0200 From: Ingo Molnar To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, oleg@tv-sign.ru, manfred@colorfullife.com, dipankar@in.ibm.com, rostedt@goodmis.org, dvhltc@us.ibm.com, niv@us.ibm.com Subject: Re: [PATCH tip/core/rcu] classic RCU locking and memory-barrier cleanups Message-ID: <20080815142430.GA20722@elte.hu> References: <20080805162144.GA8297@linux.vnet.ibm.com> <20080815140902.GE14103@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080815140902.GE14103@elte.hu> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Paul, one of your two recent RCU patches caused this lockdep splat in -tip testing: -------------------> Brought up 2 CPUs Total of 2 processors activated (6850.87 BogoMIPS). PM: Adding info for No Bus:platform khelper used greatest stack depth: 3124 bytes left ================================= [ INFO: inconsistent lock state ] 2.6.27-rc3-tip #1 --------------------------------- inconsistent {softirq-on-W} -> {in-softirq-W} usage. ksoftirqd/0/4 [HC0[0]:SC1[1]:HE1:SE0] takes: (&rcu_ctrlblk.lock){-+..}, at: [] __rcu_process_callbacks+0x1ac/0x1f0 {softirq-on-W} state was registered at: [] __lock_acquire+0x3f4/0x5b0 [] lock_acquire+0x89/0xc0 [] _spin_lock+0x3b/0x70 [] rcu_init_percpu_data+0x29/0x80 [] rcu_cpu_notify+0xaf/0xd0 [] notifier_call_chain+0x2d/0x60 [] __raw_notifier_call_chain+0x1e/0x30 [] _cpu_up+0x79/0x110 [] cpu_up+0x4d/0x70 [] kernel_init+0xb1/0x200 [] kernel_thread_helper+0x7/0x10 [] 0xffffffff irq event stamp: 14 hardirqs last enabled at (14): [] trace_hardirqs_on+0xb/0x10 hardirqs last disabled at (13): [] trace_hardirqs_off+0xb/0x10 softirqs last enabled at (0): [] copy_process+0x276/0x1190 softirqs last disabled at (11): [] call_on_stack+0x1a/0x30 other info that might help us debug this: no locks held by ksoftirqd/0/4. stack backtrace: Pid: 4, comm: ksoftirqd/0 Not tainted 2.6.27-rc3-tip #1 [] print_usage_bug+0x16c/0x1b0 [] mark_lock+0xa75/0xb10 [] ? sched_clock+0x15/0x30 [] __lock_acquire+0x3ad/0x5b0 [] lock_acquire+0x89/0xc0 [] ? __rcu_process_callbacks+0x1ac/0x1f0 [] _spin_lock+0x3b/0x70 [] ? __rcu_process_callbacks+0x1ac/0x1f0 [] __rcu_process_callbacks+0x1ac/0x1f0 [] rcu_process_callbacks+0x26/0x50 [] __do_softirq+0x95/0x120 [] ? __do_softirq+0x0/0x120 [] call_on_stack+0x1a/0x30 [] ? ksoftirqd+0x96/0x110 [] ? ksoftirqd+0x0/0x110 [] ? kthread+0x47/0x80 [] ? kthread+0x0/0x80 [] ? kernel_thread_helper+0x7/0x10 ======================= calling init_cpufreq_transition_notifier_list+0x0/0x20 initcall init_cpufreq_transition_notifier_list+0x0/0x20 returned 0 after 0 msecs calling net_ns_init+0x0/0x190 net_namespace: 676 bytes initcall net_ns_init+0x0/0x190 returned 0 after 0 msecs calling cpufreq_tsc+0x0/0x20 initcall cpufreq_tsc+0x0/0x20 returned 0 after 0 msecs calling reboot_init+0x0/0x20 initcall reboot_init+0x0/0x20 returned 0 after 0 msecs calling print_banner+0x0/0x10 Booting paravirtualized kernel on bare hardware <----------------------- my guess is on: commit 1f7b94cd3d564901f9e04a8bc5832ae7bfd690a0 Author: Paul E. McKenney Date: Tue Aug 5 09:21:44 2008 -0700 rcu: classic RCU locking and memory-barrier cleanups Ingo