To add some more observations: After running umount in the context of an "at" job, the issue nearly disappeared completely. Before this change, i already suspected power saving mechanisms to increase the probability of a freeze. Last week i had a freeze again, as the lid of my laptop has been closed during the backup. Turning the display off via DPMS appears to have a similar effect.
Maybe the "at" assumption has been wrong and the issue is more related to the graphics subystem. It would, at least to a certain degree, explain why i never was able to reproduce it by running the script manually. At the other hand, i remember cases in which i had been working and at the end of the backup, the system stopped responding. This might be a red herring again ... -- 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: Incomplete 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