Finally there is a bug report for my issue, yay! This bug hits me on precise with any of the current LTS kernels, i am struggling with it for more than a year, maybe even two. Sometimes all just works fine, sometimes the system locks up. I wasn't able to see the error message since i never had the console open when the issue appeared. Nothing in the log files, too.
Environment: Kernel 3.8.0-27-generic on Ubuntu 12.04. LVM on top of cryptsetup/LUKS, seven logical volumes (six data, one swap) Bacula file daemon running for backups (I use a shell script to set up lvm snapshots (ro) and mount them ro, like Craig.) Last lines from bacula log: 03-Aug 17:39 markusnb-fd JobId 1706: ClientAfterJob: Unmounting Snapshot of vgluks/storage ... + udevadm settle --quiet 03-Aug 17:39 markusnb-fd JobId 1706: ClientAfterJob: + sync 03-Aug 17:39 markusnb-fd JobId 1706: ClientAfterJob: + local out 03-Aug 17:39 markusnb-fd JobId 1706: ClientAfterJob: ++ umount -f /var/run/lvm-snapshot/storage -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1115753 Title: Umount of Multiple LVM Snapshots Causes 'soft lockup CPU#0 stuck for' Status in “linux” package in Ubuntu: Confirmed Bug description: Simultaneous umount of multiple lvm snapshots causes system to hang / freeze / deadlock. Window manager freezes. If umount is executed in a non window-manager tty, messages containing "BUG", "blocked for more than xx seconds", and a list of tasks associated with each of the 8 cpu cores will scroll up at regular intervals. The tasks assigned to each cpu core are unchanging over time, appearing to be deadlocked. No relevant information is left in system logs. Hard reset / poweroff is required. Problem does not occur 100% of the time. It is less likely to occur if umount is done shortly after mount. Problem still occurs -- but less frequently -- if lazy umount -l is used. Snapshots are read-only, and are mounted read-only. ProblemType: Bug DistroRelease: Ubuntu 12.04 Package: linux-image-3.2.0-37-generic 3.2.0-37.58 ProcVersionSignature: Ubuntu 3.2.0-37.58-generic 3.2.35 Uname: Linux 3.2.0-37-generic x86_64 AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24. ApportVersion: 2.0.1-0ubuntu17.1 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC1: craig 3257 F.... pulseaudio /dev/snd/controlC0: craig 3257 F.... pulseaudio CRDA: Error: command ['iw', 'reg', 'get'] failed with exit code 1: nl80211 not found. Card0.Amixer.info: Card hw:0 'SB'/'HDA ATI SB at 0xfeb00000 irq 16' Mixer name : 'Realtek ALC889' Components : 'HDA:10ec0889,1043846b,00100004' Controls : 49 Simple ctrls : 24 Card1.Amixer.info: Card hw:1 'HDMI'/'HDA ATI HDMI at 0xfea30000 irq 98' Mixer name : 'ATI R6xx HDMI' Components : 'HDA:1002aa01,00aa0100,00100100' Controls : 6 Simple ctrls : 1 Card1.Amixer.values: Simple mixer control 'IEC958',0 Capabilities: pswitch pswitch-joined penum Playback channels: Mono Mono: Playback [on] Date: Mon Feb 4 18:58:37 2013 HibernationDevice: RESUME=UUID=b788f786-ba76-4eb0-991f-d3bbc339d3f7 InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111011) IwConfig: lo no wireless extensions. eth0 no wireless extensions. MachineType: To be filled by O.E.M. To be filled by O.E.M. MarkForUpload: True ProcEnviron: TERM=xterm PATH=(custom, no user) LANG=en_US.UTF-8 SHELL=/bin/bash ProcFB: 0 VESA VGA ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.2.0-37-generic root=/dev/mapper/volgroup0-root ro RelatedPackageVersions: linux-restricted-modules-3.2.0-37-generic N/A linux-backports-modules-3.2.0-37-generic N/A linux-firmware 1.79.1 RfKill: SourcePackage: linux UpgradeStatus: Upgraded to precise on 2012-10-23 (104 days ago) dmi.bios.date: 09/27/2011 dmi.bios.vendor: American Megatrends Inc. dmi.bios.version: 0813 dmi.board.asset.tag: To be filled by O.E.M. dmi.board.name: Crosshair V Formula dmi.board.vendor: ASUSTeK Computer INC. dmi.board.version: Rev 1.xx 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.:bvr0813:bd09/27/2011:svnTobefilledbyO.E.M.:pnTobefilledbyO.E.M.:pvrTobefilledbyO.E.M.:rvnASUSTeKComputerINC.:rnCrosshairVFormula:rvrRev1.xx: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. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1115753/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp