"unregister_netdevice: waiting for lo to become free." message after shutting down an lxc container

Bug #1039196 reported by Jean-Baptiste Lallement on 2012-08-20
24
This bug affects 5 people
Affects Status Importance Assigned to Milestone
lxc (Ubuntu)
Undecided
Unassigned

Bug Description

On Quantal, after I shutdown an lxc-container the following message is displayed in syslog every 10s:
Aug 20 21:50:23 sark kernel: [50270.380638] unregister_netdevice: waiting for lo to become free. Usage count = 1
Aug 20 21:50:34 sark kernel: [50280.617544] unregister_netdevice: waiting for lo to become free. Usage count = 1
Aug 20 21:50:44 sark kernel: [50290.854556] unregister_netdevice: waiting for lo to become free. Usage count = 1
Aug 20 21:50:54 sark kernel: [50301.091389] unregister_netdevice: waiting for lo to become free. Usage count = 1

Usage count maybe 1 or more.

Then I cannot start the container again and it completely blocks the shutdown of the host system which is waiting for lo to become free.

Reboot is then forced with SysRq.

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: lxc 0.8.0~rc1-4ubuntu26
ProcVersionSignature: Ubuntu 3.5.0-10.10-generic 3.5.1
Uname: Linux 3.5.0-10-generic x86_64
ApportVersion: 2.4-0ubuntu8
Architecture: amd64
Date: Mon Aug 20 21:46:57 2012
ProcEnviron:
 TERM=xterm
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: lxc
UpgradeStatus: Upgraded to quantal on 2012-01-31 (201 days ago)

Jean-Baptiste Lallement (jibel) wrote :
Launchpad Janitor (janitor) wrote :

Status changed to 'Confirmed' because the bug affects multiple users.

Changed in lxc (Ubuntu):
status: New → Confirmed
Robert (web-ubuntu) wrote :

Same here on 12.10.

I can start a container. After shutting it down, it wont come up again. The console just hangs right after issuing the second starting command with no further output line.

syslog shows "waiting for lo to become free" messages.

I am able to shutdown the host.

Tim (iceczd) wrote :

Same as Robert, and this only happens occasionally, I am using Ubuntu 12.10 kernel 3.6.3

Here is a log excerpt:

--Mount file system
kjournald starting. Commit interval 5 seconds
EXT3-fs (dm-1): using internal journal
EXT3-fs (dm-1): mounted filesystem with ordered data mode
--lxc-start
device vethAUqDoX entered promiscuous mode
IPv6: ADDRCONF(NETDEV_UP): vethAUqDoX: link is not ready
unregister_netdevice: waiting for lo to become free. Usage count = 1
unregister_netdevice: waiting for lo to become free. Usage count = 1
unregister_netdevice: waiting for lo to become free. Usage count = 1
unregister_netdevice: waiting for lo to become free. Usage count = 1
unregister_netdevice: waiting for lo to become free. Usage count = 1
unregister_netdevice: waiting for lo to become free. Usage count = 1
unregister_netdevice: waiting for lo to become free. Usage count = 1
unregister_netdevice: waiting for lo to become free. Usage count = 1
unregister_netdevice: waiting for lo to become free. Usage count = 1
unregister_netdevice: waiting for lo to become free. Usage count = 1
unregister_netdevice: waiting for lo to become free. Usage count = 1
unregister_netdevice: waiting for lo to become free. Usage count = 1
unregister_netdevice: waiting for lo to become free. Usage count = 1
unregister_netdevice: waiting for lo to become free. Usage count = 1
unregister_netdevice: waiting for lo to become free. Usage count = 1
INFO: task lxc-start:3820 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
lxc-start D 0000000000000000 0 3820 1 0x00000000
 ffff88001c119ca0 0000000000000286 ffff88001c119c50 ffffffff8113528d
 ffff88001c119fd8 ffff88001c119fd8 ffff88001c119fd8 0000000000013dc0
 ffff88000b352da0 ffff880012d1db40 ffff88001c119ca0 ffffffff81cad260
Call Trace:
 [<ffffffff8113528d>] ? free_pages+0x3d/0x40
 [<ffffffff8169e459>] schedule+0x29/0x70
 [<ffffffff8169e71e>] schedule_preempt_disabled+0xe/0x10
 [<ffffffff8169d347>] __mutex_lock_slowpath+0xd7/0x150
 [<ffffffff8169cf5a>] mutex_lock+0x2a/0x50
 [<ffffffff8157de74>] copy_net_ns+0x84/0x110
 [<ffffffff8108192b>] create_new_namespaces+0xdb/0x190
 [<ffffffff81081b1c>] copy_namespaces+0x8c/0xd0
 [<ffffffff8105513b>] ? dup_mm+0x13b/0x240
 [<ffffffff81055960>] copy_process.part.24+0x6e0/0xec0
 [<ffffffff810561b7>] copy_process+0x77/0x80
 [<ffffffff810562ea>] do_fork+0xfa/0x290
 [<ffffffff8117821f>] ? kmem_cache_free+0x2f/0x110
 [<ffffffff81191035>] ? putname+0x35/0x50
 [<ffffffff8101d638>] sys_clone+0x28/0x30
 [<ffffffff816a7ef3>] stub_clone+0x13/0x20
 [<ffffffff816a7be9>] ? system_call_fastpath+0x16/0x1b

 --Repeated unregister_netdevice, then lxc-start blocked message

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