From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sasha Levin Subject: net: Hung task when closing device Date: Wed, 14 Mar 2012 17:07:35 -0400 Message-ID: <1331759255.3723.8.camel@lappy> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Dave Jones To: davem , Eric Dumazet , netdev , linux-kernel Return-path: Received: from mail-bk0-f46.google.com ([209.85.214.46]:37630 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756031Ab2CNTHu (ORCPT ); Wed, 14 Mar 2012 15:07:50 -0400 Sender: netdev-owner@vger.kernel.org List-ID: Hi all, I've stumbled on the backtrace at the bottom when running the trinity fuzzer in a KVM guest on the latest linux-next build. It reminds me a lot of https://lkml.org/lkml/2012/1/14/45 where the problem was a held mutex when leaving to userspace to deal with call_usermodehelper_exec(). [ 241.448189] INFO: task kworker/u:2:3577 blocked for more than 120 seconds. [ 241.449837] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 241.452037] kworker/u:2 D 0000000000000000 4280 3577 2 0x00000000 [ 241.454055] ffff88002d599810 0000000000000082 5482a487f047e242 ffff88002d599fd8 [ 241.456210] 00000000001d4340 ffff88002d598000 00000000001d4340 00000000001d4340 [ 241.457907] 00000000001d4340 00000000001d4340 ffff88002d599fd8 00000000001d4340 [ 241.459056] Call Trace: [ 241.459424] [] schedule+0x24/0x70 [ 241.460130] [] schedule_timeout+0x245/0x2c0 [ 241.460994] [] ? mark_held_locks+0x6e/0x130 [ 241.461890] [] ? __lock_release+0x8f/0x1d0 [ 241.462779] [] ? _raw_spin_unlock_irq+0x2b/0x70 [ 241.463585] [] ? get_parent_ip+0x11/0x50 [ 241.464344] [] wait_for_common+0x120/0x170 [ 241.465108] [] ? try_to_wake_up+0x250/0x250 [ 241.465798] [] wait_for_completion+0x18/0x20 [ 241.466533] [] call_usermodehelper_exec+0x228/0x230 [ 241.467372] [] ? wait_for_common+0x44/0x170 [ 241.468111] [] kobject_uevent_env+0x61b/0x650 [ 241.468957] [] ? sched_clock+0x13/0x20 [ 241.469852] [] kobject_uevent+0xb/0x10 [ 241.470652] [] kobject_cleanup+0xca/0x1b0 [ 241.471426] [] kobject_release+0xd/0x10 [ 241.472140] [] kobject_put+0x2c/0x60 [ 241.472819] [] ? dev_mc_flush+0x38/0x50 [ 241.473524] [] net_rx_queue_update_kobjects+0xab/0xf0 [ 241.474426] [] netdev_unregister_kobject+0x37/0x70 [ 241.475311] [] rollback_registered_many+0x186/0x250 [ 241.476139] [] unregister_netdevice_many+0x14/0x60 [ 241.476935] [] default_device_exit_batch+0xb5/0xe0 [ 241.477773] [] ops_exit_list.clone.0+0x53/0x60 [ 241.478562] [] cleanup_net+0x100/0x1a0 [ 241.479244] [] process_one_work+0x1c7/0x460 [ 241.479938] [] ? process_one_work+0x166/0x460 [ 241.480740] [] ? net_drop_ns+0x40/0x40 [ 241.481488] [] worker_thread+0x162/0x340 [ 241.482216] [] ? manage_workers.clone.13+0x130/0x130 [ 241.483040] [] kthread+0xbe/0xd0 [ 241.483679] [] kernel_thread_helper+0x4/0x10 [ 241.484473] [] ? finish_task_switch+0x78/0x100 [ 241.485291] [] ? retint_restore_args+0x13/0x13 [ 241.486058] [] ? kthread_flush_work_fn+0x10/0x10 [ 241.486844] [] ? gs_change+0x13/0x13 [ 241.487535] 4 locks held by kworker/u:2/3577: [ 241.488131] #0: (netns){.+.+.+}, at: [] process_one_work+0x166/0x460 [ 241.489222] #1: (net_cleanup_work){+.+.+.}, at: [] process_one_work+0x166/0x460 [ 241.490419] #2: (net_mutex){+.+.+.}, at: [] cleanup_net+0x80/0x1a0 [ 241.491460] #3: (rtnl_mutex){+.+.+.}, at: [] rtnl_lock+0x12/0x20 [ 241.492556] Kernel panic - not syncing: hung_task: blocked tasks [ 241.493478] Rebooting in 1 seconds. -- Sasha.