Comment 7 for bug 616745

Repro:

[ 6295.349006] BUG: soft lockup - CPU#1 stuck for 61s! [netns:13]
[ 6295.349006] Modules linked in: ppp_deflate bsd_comp ppp_async crc_ccitt cdc_ether cdc_phonet phonet
 usbnet mii cdc_acm usb_storage binfmt_misc rfcomm ppdev sco bridge stp bnep l2cap vboxdrv deflate zlib_deflate ctr twofish twofish_
common camellia serpent blowfish cast5 des_generic aes_i586 aes_generic xcbc rmd160 sha256_generic sha1_generic crypto_null af_key d
m_crypt joydev snd_hda_codec_idt snd_hda_intel snd_hda_codec snd_hwdep snd_pcm_oss snd_mixer_oss snd_pcm snd_seq_dummy snd_seq_oss s
nd_seq_midi arc4 snd_rawmidi snd_seq_midi_event snd_seq snd_timer snd_seq_device iwl3945 iwlcore snd dell_wmi uvcvideo videodev v4l1
_compat btusb bluetooth sdhci_pci sdhci ricoh_mmc mac80211 led_class dell_laptop dcdbas psmouse serio_raw soundcore snd_page_alloc c
fg80211 uinput lp parport fbcon tileblit font bitblit softcursor vga16fb vgastate usbhid hid i915 drm_kms_helper ohci1394 drm ieee13
94 intel_agp ahci i2c_algo_bit video output tg3 agpgart
[ 6295.349006]
[ 6295.349006] Pid: 13, comm: netns Not tainted (2.6.32-25-generic #44-Ubuntu) Inspiron 1420

[ 6295.349006] EIP: 0060:[<c012a4f5>] EFLAGS: 00000217 CPU: 1
[ 6295.349006] EIP is at __ticket_spin_lock+0x15/0x20
[ 6295.349006] EAX: f0d6f878 EBX: f0d6f878 ECX: efdc4c00 EDX: 00009400
[ 6295.349006] ESI: 00000000 EDI: efdc4c00 EBP: f70b1e88 ESP: f70b1e88
[ 6295.349006] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
[ 6295.349006] CR0: 8005003b CR2: b361b000 CR3: 0084e000 CR4: 000006d0
[ 6295.349006] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
[ 6295.349006] DR6: ffff0ff0 DR7: 00000400
[ 6295.349006] Call Trace:
[ 6295.349006] [<c058d437>] _spin_lock_bh+0x17/0x20
[ 6295.349006] [<fabd914c>] phonet_device_destroy+0x4c/0x160 [phonet]
[ 6295.349006] [<c05469a9>] ? addrconf_notify+0x99/0x470
[ 6295.349006] [<c0512e34>] ? arp_ifdown+0x14/0x20
[ 6295.349006] [<c056ab76>] ? packet_notifier+0x26/0x1a0
[ 6295.349006] [<fabd95d9>] phonet_device_notify+0x19/0x40 [phonet]
[ 6295.349006] [<c058fa03>] notifier_call_chain+0x43/0x60