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[Bug 1087010] Status changed to Confirmed


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** Changed in: linux (Ubuntu)
       Status: New => Confirmed

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  kworker uses 70-90% of a CPU core (hyperthreaded)

Status in “linux” package in Ubuntu:

Bug description:
  I see high cpu usage from a kworker thread. Usually kworker/0:1 or kworker/0:2. I tested various kernels from Ubuntu and mainline (3.5.0-x, 3.6.x, 3.7.0-rcx) and they all showed the same behavior. This does not always happen.
  I wasn't able to determine on which basis it happens. Some observations that may as well be wrong (duh!):
  On some boot all is fine but once it shows, no matter how many reboots it does not seem to want to go away again.
  The laptop seems to have to rest a while to have a chance that it won't happen.
  If it does not happen a reboot will show the behavior.

  I saw similar bug reports in various places but it seems that this can
  have a multitude of causes and the presented workarounds or fixes did
  not apply to me.

  ProblemType: Bug
  DistroRelease: Ubuntu 12.10
  Package: linux-image-3.5.0-19-generic 3.5.0-19.30
  ProcVersionSignature: Ubuntu 3.5.0-19.30-generic 3.5.7
  Uname: Linux 3.5.0-19-generic x86_64
  ApportVersion: 2.6.1-0ubuntu6
  Architecture: amd64
   /dev/snd/controlC0:  mio        1965 F.... pulseaudio
   /dev/snd/pcmC0D0p:   mio        1965 F...m pulseaudio
  Date: Wed Dec  5 22:37:00 2012
  HibernationDevice: RESUME=UUID=a371882c-0fe7-45e5-9adb-83da8374bc11
  InstallationDate: Installed on 2012-10-10 (55 days ago)
  InstallationMedia: Ubuntu 12.04.1 LTS "Precise Pangolin" - Release amd64 (20120823.1)
  MarkForUpload: True
   PATH=(custom, no user)
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.5.0-19-generic root=UUID=79674508-93de-43e0-b313-f6a9b480c606 ro crashkernel=384M-2G:64M,2G-:128M acpi_osi=Linux pcie_aspm=force i915.modeset=1 i915.i915_enable_rc6=1 i915.lvds_downclock=1 i915.semaphores=1 i915.powersave=1 snd_hda_intel.power_save_controller=1 snd_hda_intel.power_save=1 quiet splash vt.handoff=7
   Error: command ['pacmd', 'list'] failed with exit code 1: Home directory /home/mio not ours.
   No PulseAudio daemon running, or not running as session daemon.
   linux-restricted-modules-3.5.0-19-generic N/A
   linux-backports-modules-3.5.0-19-generic  N/A
   linux-firmware                            1.95
  SourcePackage: linux
  UpgradeStatus: Upgraded to quantal on 2012-10-11 (55 days ago)
  dmi.bios.date: 08/02/2012
  dmi.bios.vendor: Phoenix Technologies Ltd.
  dmi.bios.version: P04AAE
  dmi.board.asset.tag: Base Board Asset Tag
  dmi.board.name: SAMSUNG_NP1234567890
  dmi.board.vendor: SAMSUNG ELECTRONICS CO., LTD.
  dmi.board.version: FAB1
  dmi.chassis.asset.tag: No Asset Tag
  dmi.chassis.type: 9
  dmi.chassis.vendor: SAMSUNG ELECTRONICS CO., LTD.
  dmi.chassis.version: 0.1
  dmi.modalias: dmi:bvnPhoenixTechnologiesLtd.:bvrP04AAE:bd08/02/2012:svnSAMSUNGELECTRONICSCO.,LTD.:pn700Z7C:pvr0.1:rvnSAMSUNGELECTRONICSCO.,LTD.:rnSAMSUNG_NP1234567890:rvrFAB1:cvnSAMSUNGELECTRONICSCO.,LTD.:ct9:cvr0.1:
  dmi.product.name: 700Z7C
  dmi.product.version: 0.1
  dmi.sys.vendor: SAMSUNG ELECTRONICS CO., LTD.

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