kernel-packages team mailing list archive

[markusj <1115753@xxxxxxxxxxxxxxxxxx>]

Craig:
> The lockup is a little different now. Whereas previously the system would hang before any of the snapshots were removed, now some of the snapshots are successfully umount'd and lvremove'd before the hang. This could be the result of changes made to the script that does the umount and lvremove, reordering the sequence of the snapshots, which consist of home, root, and var partitions.

That is a red herring. I had done the umounting/removing alternating
until this issue appeared to me. I first assumed that lvremove caused
the hangs but after dividing the script into a split phase operation
(unmount all first, lvremove all as second) the issue appeared always
during the unmount step.


But maybe i have found a workaround: Instead of running the script in context of bacula-fd, i use "at" to decouple the unmount/lvremove step from bacula-fd and delay it for about two minutes. I had freezes at maybe two out of three backup jobs before and no one during the last three backup jobs after implementing this change.

I guess the issue lies somewhere in the way kernel, bacula-fd, bash and
unmount interact together. Breaking up this chain by running the
unmount/lvremove part outside bacula-fd and after the backup job itself
has been finished circumvents the issue to appear.

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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.

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