Raring is EOL since January 27:

https://wiki.ubuntu.com/Releases

Excerpts from Alessandro Moscatelli's message of 2014-06-12 22:23:52 UTC:
> It looks I have this problem with Ubuntu Raring
> kernel version : 3.8.13
> 
> I attached a screenshot with dmesg after I tried to start again my
> containers.
> 
> Should I open a new bug ?
> 
> Thank you in advance
> 
> 
> ** Attachment added: "screenshot"
>    https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1021471/+attachment/4130637/+files/5.png
> 
> -- 
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1021471
> 
> Title:
>   clone() hang when creating new network namespace (dmesg show
>   unregister_netdevice: waiting for lo to become free. Usage count = 2)
> 
> Status in The Linux Kernel:
>   Confirmed
> Status in “linux” package in Ubuntu:
>   Fix Released
> Status in “linux” source package in Precise:
>   Fix Released
> Status in “linux” source package in Quantal:
>   Fix Released
> 
> Bug description:
>   SRU Justification:
> 
>   Impact:
>       When creating new network namespace dmesg can show the following
>       unregister_netdevice: waiting for lo to become free. Usage count = 1
> 
>   Fix:
>       Stefan Bader's SAUCE patch has fixed this for Quantal:
>       UBUNTU: SAUCE: net/ipv4: Always flush route cache on unregister batch call
> 
>   Testcase:
>       The sourcecode found here:
>       https://lists.debian.org/debian-kernel/2012/05/msg00494.html
>       can be compiled and run as follows:
> 
>       sudo ./reproducer
>       #ctrl+c
>       sudo ./reproducer
>       #wait for a while
>       dmesg | grep unregister
> 
>   
>   --
> 
>   I'm not sure how I triggered this. I've been moving around between
>   networks and suspending/resuming all day.
> 
>   Earlier in this boot I successfully used a container (start,
>   networking and stop). I came to start the same one later and noticed
>   that it didn't come up. Trying to attach to the console with lxc-
>   console informed me that it wasn't running. I then saw suspicious
>   content in dmesg:
> 
>   [25800.412234] INFO: task lxc-start:25817 blocked for more than 120 seconds.
>   [25800.412243] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>   [25800.412254] lxc-start       D ffff88013fd13980     0 25817      1 0x00000000
>   [25800.412266]  ffff880007b43cc0 0000000000000086 ffff88003ba4c500 ffff880007b43fd8
>   [25800.412275]  ffff880007b43fd8 ffff880007b43fd8 ffff880134c65c00 ffff88003ba4c500
>   [25800.412284]  000080d0ffffffff ffffffff81ca7c00 ffff88003ba4c500 ffffffff81ca7c04
>   [25800.412288] Call Trace:
>   [25800.412306]  [<ffffffff81673759>] schedule+0x29/0x70
>   [25800.412313]  [<ffffffff81673a1e>] schedule_preempt_disabled+0xe/0x10
>   [25800.412323]  [<ffffffff81672537>] __mutex_lock_slowpath+0xd7/0x150
>   [25800.412331]  [<ffffffff8167200a>] mutex_lock+0x2a/0x50
>   [25800.412340]  [<ffffffff8155ede1>] copy_net_ns+0x71/0x100
>   [25800.412350]  [<ffffffff8107adfb>] create_new_namespaces+0xdb/0x190
>   [25800.412357]  [<ffffffff8107afec>] copy_namespaces+0x8c/0xd0
>   [25800.412367]  [<ffffffff81050142>] copy_process.part.22+0x902/0x1520
>   [25800.412375]  [<ffffffff81050ee5>] do_fork+0x135/0x390
>   [25800.412385]  [<ffffffff8116db40>] ? kmem_cache_free+0x20/0x100
>   [25800.412395]  [<ffffffff8118c6b3>] ? putname+0x33/0x50
>   [25800.412402]  [<ffffffff811811cc>] ? do_sys_open+0x16c/0x200
>   [25800.412410]  [<ffffffff8101c238>] sys_clone+0x28/0x30
>   [25800.412418]  [<ffffffff8167cbf3>] stub_clone+0x13/0x20
>   [25800.412424]  [<ffffffff8167c8e9>] ? system_call_fastpath+0x16/0x1b
>   [25806.312385] unregister_netdevice: waiting for lo to become free. Usage count = 1
> 
>   ProblemType: Bug
>   DistroRelease: Ubuntu 12.10
>   Package: linux-image-generic 3.5.0.3.3
>   ProcVersionSignature: Ubuntu 3.5.0-2.2-generic 3.5.0-rc4
>   Uname: Linux 3.5.0-2-generic x86_64
>   NonfreeKernelModules: nvidia wl
>   AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.25.
>   ApportVersion: 2.2.5-0ubuntu2
>   Architecture: amd64
>   ArecordDevices:
>    **** List of CAPTURE Hardware Devices ****
>    card 0: NVidia [HDA NVidia], device 0: Cirrus Analog [Cirrus Analog]
>      Subdevices: 1/1
>      Subdevice #0: subdevice #0
>   AudioDevicesInUse:
>    USER PID ACCESS COMMAND
>    /dev/snd/controlC0:  laney      2787 F.... pulseaudio
>   CRDA: Error: command ['iw', 'reg', 'get'] failed with exit code 1: nl80211 not found.
>   Card0.Amixer.info:
>    Card hw:0 'NVidia'/'HDA NVidia at 0xd3480000 irq 22'
>      Mixer name    : 'Nvidia MCP89 HDMI'
>      Components    : 'HDA:10134206,106b0d00,00100301 HDA:10de000c,10de0101,00100200'
>      Controls      : 37
>      Simple ctrls  : 13
>   Date: Thu Jul  5 21:26:08 2012
>   HibernationDevice: RESUME=UUID=1c5b3f2c-2c89-4fa1-9ed8-0e238de8fe47
>   InstallationMedia: Ubuntu 10.04.1 LTS "Lucid Lynx" - Release amd64 (20100729)
>   MachineType: Apple Inc. MacBookPro7,1
>   ProcFB: 0 VESA VGA
>   ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.5.0-2-generic root=UUID=2228fdfe-3834-40b2-b7b4-efea7463e3c1 ro quiet splash reboot=pci vt.handoff=7
>   RelatedPackageVersions:
>    linux-restricted-modules-3.5.0-2-generic N/A
>    linux-backports-modules-3.5.0-2-generic  N/A
>    linux-firmware                           1.82
>   SourcePackage: linux
>   UpgradeStatus: Upgraded to quantal on 2012-01-13 (173 days ago)
>   dmi.bios.date: 03/25/10
>   dmi.bios.vendor: Apple Inc.
>   dmi.bios.version: MBP71.88Z.0039.B05.1003251322
>   dmi.board.name: Mac-F222BEC8
>   dmi.board.vendor: Apple Inc.
>   dmi.chassis.type: 10
>   dmi.chassis.vendor: Apple Inc.
>   dmi.chassis.version: Mac-F222BEC8
>   dmi.modalias: dmi:bvnAppleInc.:bvrMBP71.88Z.0039.B05.1003251322:bd03/25/10:svnAppleInc.:pnMacBookPro7,1:pvr1.0:rvnAppleInc.:rnMac-F222BEC8:rvr:cvnAppleInc.:ct10:cvrMac-F222BEC8:
>   dmi.product.name: MacBookPro7,1
>   dmi.product.version: 1.0
>   dmi.sys.vendor: Apple Inc.
> 
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