From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758137Ab1GKXTg (ORCPT ); Mon, 11 Jul 2011 19:19:36 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40273 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752488Ab1GKXTe (ORCPT ); Mon, 11 Jul 2011 19:19:34 -0400 Date: Mon, 11 Jul 2011 19:19:32 -0400 From: Dave Jones To: Linux Kernel Subject: lockdep circular locking error (rcu_node_level_0 vs rq->lock) Message-ID: <20110711231932.GB20367@redhat.com> Mail-Followup-To: Dave Jones , Linux Kernel MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I was doing an install in a kvm guest, which wedged itself at the end. This was in the host dmesg. [ INFO: possible circular locking dependency detected ] 3.0.0-rc6+ #91 ------------------------------------------------------- libvirtd/5720 is trying to acquire lock: (rcu_node_level_0){..-.-.}, at: [] rcu_report_unblock_qs_rnp.part.5+0x3f/0x60 but task is already holding lock: (&rq->lock){-.-.-.}, at: [] sched_ttwu_pending+0x39/0x5b which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&rq->lock){-.-.-.}: [] lock_acquire+0xf3/0x13e [] _raw_spin_lock+0x40/0x73 [] __task_rq_lock+0x5e/0x8b [] wake_up_new_task+0x46/0x10d [] do_fork+0x231/0x331 [] kernel_thread+0x75/0x77 [] rest_init+0x26/0xdc [] start_kernel+0x401/0x40c [] x86_64_start_reservations+0xaf/0xb3 [] x86_64_start_kernel+0x102/0x111 -> #2 (&p->pi_lock){-.-.-.}: [] lock_acquire+0xf3/0x13e [] _raw_spin_lock_irqsave+0x4f/0x89 [] try_to_wake_up+0x2e/0x1db [] default_wake_function+0x12/0x14 [] autoremove_wake_function+0x18/0x3d [] __wake_up_common+0x4d/0x83 [] __wake_up+0x39/0x4d [] rcu_report_exp_rnp+0x52/0x8b [] __rcu_read_unlock+0x1d0/0x231 [] rcu_read_unlock+0x26/0x28 [] __d_lookup+0x103/0x115 [] walk_component+0x1b1/0x3af [] link_path_walk+0x1a1/0x43b [] path_lookupat+0x5a/0x2af [] do_path_lookup+0x28/0x97 [] user_path_at+0x59/0x96 [] sys_readlinkat+0x33/0x95 [] sys_readlink+0x1b/0x1d [] system_call_fastpath+0x16/0x1b -> #1 (sync_rcu_preempt_exp_wq.lock){......}: [] lock_acquire+0xf3/0x13e [] _raw_spin_lock_irqsave+0x4f/0x89 [] __wake_up+0x22/0x4d [] rcu_report_exp_rnp+0x52/0x8b [] __rcu_read_unlock+0x1d0/0x231 [] rcu_read_unlock+0x26/0x28 [] __d_lookup+0x103/0x115 [] walk_component+0x1b1/0x3af [] link_path_walk+0x1a1/0x43b [] path_lookupat+0x5a/0x2af [] do_path_lookup+0x28/0x97 [] user_path_at+0x59/0x96 [] sys_readlinkat+0x33/0x95 [] sys_readlink+0x1b/0x1d [] system_call_fastpath+0x16/0x1b -> #0 (rcu_node_level_0){..-.-.}: [] __lock_acquire+0xa2f/0xd0c [] lock_acquire+0xf3/0x13e [] _raw_spin_lock+0x40/0x73 [] rcu_report_unblock_qs_rnp.part.5+0x3f/0x60 [] __rcu_read_unlock+0x18e/0x231 [] rcu_read_unlock+0x26/0x28 [] cpuacct_charge+0x58/0x61 [] update_curr+0x107/0x134 [] check_preempt_wakeup+0xc9/0x1d0 [] check_preempt_curr+0x2f/0x6e [] ttwu_do_wakeup+0x7b/0x111 [] ttwu_do_activate.constprop.76+0x5c/0x61 [] sched_ttwu_pending+0x49/0x5b [] scheduler_ipi+0xe/0x10 [] smp_reschedule_interrupt+0x1b/0x1d [] reschedule_interrupt+0x13/0x20 [] rcu_read_unlock+0x26/0x28 [] sock_def_readable+0x88/0x8d [] unix_stream_sendmsg+0x264/0x2ff [] sock_aio_write+0x112/0x126 [] do_sync_write+0xbf/0xff [] vfs_write+0xb6/0xf6 [] sys_write+0x4d/0x74 [] system_call_fastpath+0x16/0x1b other info that might help us debug this: Chain exists of: rcu_node_level_0 --> &p->pi_lock --> &rq->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&rq->lock); lock(&p->pi_lock); lock(&rq->lock); lock(rcu_node_level_0); *** DEADLOCK *** 1 lock held by libvirtd/5720: #0: (&rq->lock){-.-.-.}, at: [] sched_ttwu_pending+0x39/0x5b stack backtrace: Pid: 5720, comm: libvirtd Not tainted 3.0.0-rc6+ #91 Call Trace: [] print_circular_bug+0x1f8/0x209 [] __lock_acquire+0xa2f/0xd0c [] ? sched_clock_local+0x12/0x75 [] ? rcu_report_unblock_qs_rnp.part.5+0x3f/0x60 [] lock_acquire+0xf3/0x13e [] ? rcu_report_unblock_qs_rnp.part.5+0x3f/0x60 [] ? lock_release_holdtime.part.10+0x59/0x62 [] _raw_spin_lock+0x40/0x73 [] ? rcu_report_unblock_qs_rnp.part.5+0x3f/0x60 [] ? _raw_spin_unlock+0x47/0x54 [] rcu_report_unblock_qs_rnp.part.5+0x3f/0x60 [] ? __rcu_read_unlock+0xb8/0x231 [] __rcu_read_unlock+0x18e/0x231 [] rcu_read_unlock+0x26/0x28 [] cpuacct_charge+0x58/0x61 [] update_curr+0x107/0x134 [] check_preempt_wakeup+0xc9/0x1d0 [] check_preempt_curr+0x2f/0x6e [] ttwu_do_wakeup+0x7b/0x111 [] ttwu_do_activate.constprop.76+0x5c/0x61 [] sched_ttwu_pending+0x49/0x5b [] scheduler_ipi+0xe/0x10 [] smp_reschedule_interrupt+0x1b/0x1d [] reschedule_interrupt+0x13/0x20 [] ? sched_clock_local+0x12/0x75 [] ? __rcu_read_unlock+0x49/0x231 [] ? lock_release+0x1b1/0x1de [] rcu_read_unlock+0x26/0x28 [] sock_def_readable+0x88/0x8d [] unix_stream_sendmsg+0x264/0x2ff [] sock_aio_write+0x112/0x126 [] ? inode_has_perm+0x6a/0x77 [] do_sync_write+0xbf/0xff [] ? security_file_permission+0x2e/0x33 [] ? rw_verify_area+0xb6/0xd3 [] vfs_write+0xb6/0xf6 [] ? fget_light+0x97/0xa2 [] sys_write+0x4d/0x74 [] ? remove_wait_queue+0x1a/0x3a [] system_call_fastpath+0x16/0x1b