On my system i'm using NFS4 with autofs. I think autofs decided to umount one of the NFS4 shares and this might caused the crash.
The client usually mounts 2 shares from the server. One is the home directory and the second one is the root directory exported by the server. e.g.:
server:/home/username mounted to /home/username
server:/ mounted to /network/server
The home directory is still present and mounted (still working correctly). The second directory is no longer mounted after the crash occured. Trying to remount it fails (mount hangs).
[ 1391.824331] BUG: Dentry ffff880091c7d300{i=40b2a,n=} still in use (1) [unmount of nfs4 0:1a]
[ 1391.824353] ------------[ cut here ]------------
[ 1391.824354] kernel BUG at /build/buildd/linux-2.6.38/fs/dcache.c:947!
[ 1391.824356] invalid opcode: 0000 [#1] SMP
[ 1391.824358] last sysfs file: /sys/devices/virtual/sound/timer/uevent
[ 1391.824360] CPU 1
[ 1391.824361] Modules linked in: binfmt_misc vboxnetadp vboxnetflt vboxdrv autofs4 dm_crypt snd_hda_codec_hdmi nvidia(P) snd_hda_codec_via uvcvideo videodev v4l2_compat_ioctl32 snd_usb_audio snd_usbmidi_lib snd_hda_intel joydev snd_seq_midi snd_hda_codec snd_rawmidi snd_hwdep snd_pcm snd_seq_midi_event rpcsec_gss_krb5 nfsd exportfs nfs snd_seq snd_timer snd_seq_device lockd fscache nfs_acl auth_rpcgss psmouse sunrpc asus_atk0110 serio_raw snd soundcore snd_page_alloc lp parport dm_raid45 xor uvesafb hid_logitech ff_memless usbhid hid firewire_ohci firewire_core crc_itu_t e1000 atl1e ahci libahci
[ 1391.824392]
[ 1391.824394] Pid: 17308, comm: umount.nfs4 Tainted: P 2.6.38-8-generic #42-Ubuntu System manufacturer System Product Name/P5QD TURBO
[ 1391.824398] RIP: 0010:[<ffffffff81179945>] [<ffffffff81179945>] shrink_dcache_for_umount_subtree+0x285/0x290
[ 1391.824405] RSP: 0018:ffff8800af4e1d78 EFLAGS: 00010292
[ 1391.824407] RAX: 0000000000000066 RBX: ffff880091c7d300 RCX: 00000000000000d1
[ 1391.824408] RDX: 0000000000000000 RSI: 0000000000000082 RDI: 0000000000000246
[ 1391.824410] RBP: ffff8800af4e1db8 R08: 0000000000000033 R09: 000000000000e425
[ 1391.824411] R10: 0000000000000000 R11: 0000000000000000 R12: ffff880091c7d35c
[ 1391.824413] R13: ffff880091c7d300 R14: ffff8800637b35e0 R15: ffff880091c7db9c
[ 1391.824415] FS: 00007fc4461e6720(0000) GS:ffff8800bfc80000(0000) knlGS:0000000000000000
[ 1391.824417] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 1391.824418] CR2: 00007fc445d480d0 CR3: 000000013349a000 CR4: 00000000000406e0
[ 1391.824420] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 1391.824422] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[ 1391.824423] Process umount.nfs4 (pid: 17308, threadinfo ffff8800af4e0000, task ffff8800b9360000)
[ 1391.824425] Stack:
[ 1391.824426] ffff88008c193a58 ffff88013f80b2a8 0000000000000000 ffff88008c193800
[ 1391.824429] ffff880091c7d59c ffff880091c7d540 ffff8800637b3540 0000000000000000
[ 1391.824432] ffff8800af4e1de8 ffffffff8117c2b9 ffffffff8105f640 ffff88008c193800
[ 1391.824435] Call Trace:
[ 1391.824438] [<ffffffff8117c2b9>] shrink_dcache_for_umount+0x69/0x90
[ 1391.824442] [<ffffffff8105f640>] ? default_wake_function+0x0/0x20
[ 1391.824445] [<ffffffff81166bfc>] generic_shutdown_super+0x2c/0x100
[ 1391.824447] [<ffffffff81166d66>] kill_anon_super+0x16/0x60
[ 1391.824460] [<ffffffffa01d82e9>] nfs4_kill_super+0x39/0x90 [nfs]
[ 1391.824463] [<ffffffff811671d5>] deactivate_locked_super+0x45/0x70
[ 1391.824465] [<ffffffff81167e5a>] deactivate_super+0x4a/0x70
[ 1391.824469] [<ffffffff81183254>] mntput_no_expire+0xa4/0xf0
[ 1391.824471] [<ffffffff811832bf>] mntput+0x1f/0x30
[ 1391.824473] [<ffffffff81183b72>] release_mounts+0x72/0x90
[ 1391.824475] [<ffffffff81184162>] do_umount+0xd2/0x1f0
[ 1391.824478] [<ffffffff81184343>] sys_umount+0xc3/0xd0
[ 1391.824481] [<ffffffff8100c002>] system_call_fastpath+0x16/0x1b
[ 1391.824482] Code: 8b 40 28 4c 8b 08 49 8b 45 30 48 85 c0 74 07 48 8b 90 a8 00 00 00 48 89 34 24 48 c7 c7 50 6c 7e 81 4c 89 ee 31 c0 e8 94 66 44 00 <0f> 0b 0f 0b 0f 1f 80 00 00 00 00 55 48 89 e5 48 83 ec 20 48 89
[ 1391.824506] RIP [<ffffffff81179945>] shrink_dcache_for_umount_subtree+0x285/0x290
[ 1391.824509] RSP <ffff8800af4e1d78>
[ 1391.824512] ---[ end trace 2f5476b7c0d03692 ]---
---
.etc.asound.conf:
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.23.
Architecture: amd64
Card0.Amixer.info:
Card hw:0 'Intel'/'HDA Intel at 0xfcff8000 irq 45'
Mixer name : 'VIA VT1708S'
Components : 'HDA:11060397,104383ae,00100000'
Controls : 38
Simple ctrls : 22
Card1.Amixer.info:
Card hw:1 'Device'/'C-Media Electronics Inc. USB Advanced Audio Device at usb-0000:00:1d.2-1, full '
Mixer name : 'USB Mixer'
Components : 'USB0b05:1743'
Controls : 10
Simple ctrls : 7
Card2.Amixer.info:
Card hw:2 'NVidia'/'HDA NVidia at 0xfe8fc000 irq 17'
Mixer name : 'Nvidia GPU 0d HDMI/DP'
Components : 'HDA:10de000d,10de0101,00100100'
Controls : 16
Simple ctrls : 4
Card3.Amixer.info:
Card hw:3 'CAMERA'/'ARKMICRO USB2.0 PC CAMERA at usb-0000:00:1d.7-2.4, high speed'
Mixer name : 'USB Mixer'
Components : 'USB18ec:3288'
Controls : 2
Simple ctrls : 1
CurrentDmesg: Error: command ['sh', '-c', 'dmesg | comm -13 --nocheck-order /var/log/dmesg -'] failed with exit code 1: comm: /var/log/dmesg: Permission denied
DistroRelease: Ubuntu 11.04
InstallationMedia: Kubuntu 10.04 LTS "Lucid Lynx" - Release amd64 (20100427)
MachineType: System manufacturer System Product Name
NonfreeKernelModules: nvidia
Package: linux (not installed)
ProcEnviron:
LANGUAGE=
PATH=(custom, user)
LANG=en_US.UTF-8
SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.38-8-generic root=UUID=7d9982e1-e7c9-4fa4-87a9-a04720fef389 ro quiet splash nomodeset video=uvesafb:mode_option=1680x1050-32,mtrr=3,scroll=ywrap
ProcVersionSignature: Ubuntu 2.6.38-8.42-generic 2.6.38.2
Tags: natty
Uname: Linux 2.6.38-8-generic x86_64
UpgradeStatus: Upgraded to natty on 2011-05-09 (58 days ago)
UserGroups: 3dprotect audio cdrom dip domainUsers fastprotect plugdev users video
dmi.bios.date: 08/04/2009
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 0301
dmi.board.asset.tag: To Be Filled By O.E.M.
dmi.board.name: P5QD TURBO
dmi.board.vendor: ASUSTeK Computer INC.
dmi.board.version: Rev 1.xx
dmi.chassis.asset.tag: Asset-1234567890
dmi.chassis.type: 3
dmi.chassis.vendor: Chassis Manufacture
dmi.chassis.version: Chassis Version
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr0301:bd08/04/2009:svnSystemmanufacturer:pnSystemProductName:pvrSystemVersion:rvnASUSTeKComputerINC.:rnP5QDTURBO:rvrRev1.xx:cvnChassisManufacture:ct3:cvrChassisVersion:
dmi.product.name: System Product Name
dmi.product.version: System Version
dmi.sys.vendor: System manufacturer
---
.etc.asound.conf:
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.23.
Architecture: amd64
ArecordDevices:
**** List of CAPTURE Hardware Devices ****
card 0: SB [HDA ATI SB], device 0: ALC892 Analog [ALC892 Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
Card0.Amixer.info:
Card hw:0 'SB'/'HDA ATI SB at 0xf9ff4000 irq 16'
Mixer name : 'Realtek ALC892'
Components : 'HDA:10ec0892,18491892,00100302'
Controls : 33
Simple ctrls : 19
CurrentDmesg: Error: command ['sh', '-c', 'dmesg | comm -13 --nocheck-order /var/log/dmesg -'] failed with exit code 1: comm: /var/log/dmesg: Permission denied
DistroRelease: Ubuntu 11.04
MachineType: To Be Filled By O.E.M. To Be Filled By O.E.M.
NonfreeKernelModules: nvidia
Package: linux (not installed)
ProcEnviron:
LANGUAGE=
PATH=(custom, user)
LANG=en_US.UTF-8
SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-2.6.38-10-generic root=/dev/mapper/midas-root ro quiet splash nomodeset video=uvesafb:mode_option=1680x1050-32,mtrr=3,scroll=ywrap
ProcVersionSignature: Ubuntu 2.6.38-10.46-generic 2.6.38.7
Tags: natty
Uname: Linux 2.6.38-10-generic x86_64
UpgradeStatus: Upgraded to natty on 2011-04-12 (111 days ago)
UserAsoundrc:
UserGroups: audio cdrom developer dip domainAdmins domainUsers mythtv plugdev smartprot users video
dmi.bios.date: 08/05/2010
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: P1.40
dmi.board.name: 880GMH/USB3.
dmi.board.vendor: ASRock
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: To Be Filled By O.E.M.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrP1.40:bd08/05/2010:svnToBeFilledByO.E.M.:pnToBeFilledByO.E.M.:pvrToBeFilledByO.E.M.:rvnASRock:rn880GMH/USB3.:rvr:cvnToBeFilledByO.E.M.:ct3:cvrToBeFilledByO.E.M.:
dmi.product.name: To Be Filled By O.E.M.
dmi.product.version: To Be Filled By O.E.M.
dmi.sys.vendor: To Be Filled By O.E.M.
apport information