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[Gordon Dracup <1318116@xxxxxxxxxxxxxxxxxx>]

*** This bug is a duplicate of bug 1322407 ***
    https://bugs.launchpad.net/bugs/1322407

** This bug has been marked a duplicate of bug 1322407
   NFS kernel server creates a kworker with 100% CPU usage, then hangs randomly

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https://bugs.launchpad.net/bugs/1318116

Title:
  kworker uses 100% CPU when nfs-kernel-server is active

Status in “linux” package in Ubuntu:
  Triaged

Bug description:
  I have a clean install of 14.04 on an i7-860 with 16GB RAM.

  I'm using NFS to share a home directory.  The volume is ~2TB,
  formatted JFS, and it has a single client.

  I recently noticed that I had a [kworker] process using 100% CPU:

    PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND
   9253 root      20   0       0      0      0 R  99.9  0.0   0:30.17 [kworker/3:1]

  Rebooting didn't help.

  After some troubleshooting I found that it went away immediately when
  I stopped the nfs-kernel-server daemon.  When I start it, it comes
  back after a minute or two, still using 99-100% CPU.  The load goes
  away when the client is turned off and the NFS server is restarted,
  but it comes back as soon as it reconnects.

  The only line in /etc/exports is:
  /home 192.168.1.0/24(rw,sync,no_root_squash)

  version_signature:
  Ubuntu 3.13.0-24.47-generic 3.13.9

  # dpkg -l nfs-kernel-server
  Desired=Unknown/Install/Remove/Purge/Hold
  | Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
  |/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
  ||/ Name           Version      Architecture Description
  +++-==============-============-============-==================================
  ii  nfs-kernel-ser 1:1.2.8-6ubu amd64        support for NFS kernel server

  Description:    Ubuntu 14.04 LTS
  Release:        14.04

  I don't think this is related to my hardware but I can provide lspci output if necessary.
  ---
  ApportVersion: 2.14.1-0ubuntu3
  Architecture: amd64
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC1:  username   4414 F.... pulseaudio
                        username   4778 F.... pulseaudio
   /dev/snd/controlC0:  username   4414 F.... pulseaudio
                        username   4778 F.... pulseaudio
  DistroRelease: Ubuntu 14.04
  HibernationDevice: RESUME=UUID=de6e2d52-86c9-4867-8d37-31964953e1e6
  InstallationDate: Installed on 2014-05-01 (9 days ago)
  InstallationMedia: Kubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140416.1)
  IwConfig:
   eth0      no wireless extensions.

   eth1      no wireless extensions.

   lo        no wireless extensions.
  MachineType: Gigabyte Technology Co., Ltd. P55A-UD4P
  NonfreeKernelModules: nvidia
  Package: linux (not installed)
  ProcEnviron:
   TERM=xterm
   PATH=(custom, no user)
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  ProcFB:

  ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.13.0-24-generic root=/dev/mapper/hostname-newestroot ro quiet splash
  ProcVersionSignature: Ubuntu 3.13.0-24.47-generic 3.13.9
  PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No PulseAudio daemon running, or not running as session daemon.
  RelatedPackageVersions:
   linux-restricted-modules-3.13.0-24-generic N/A
   linux-backports-modules-3.13.0-24-generic  N/A
   linux-firmware                             1.127
  RfKill:

  Tags:  trusty
  Uname: Linux 3.13.0-24-generic x86_64
  UpgradeStatus: No upgrade log present (probably fresh install)
  UserGroups:

  _MarkForUpload: True
  dmi.bios.date: 10/16/2009
  dmi.bios.vendor: Award Software International, Inc.
  dmi.bios.version: F3
  dmi.board.name: P55A-UD4P
  dmi.board.vendor: Gigabyte Technology Co., Ltd.
  dmi.board.version: x.x
  dmi.chassis.type: 3
  dmi.chassis.vendor: Gigabyte Technology Co., Ltd.
  dmi.modalias: dmi:bvnAwardSoftwareInternational,Inc.:bvrF3:bd10/16/2009:svnGigabyteTechnologyCo.,Ltd.:pnP55A-UD4P:pvr:rvnGigabyteTechnologyCo.,Ltd.:rnP55A-UD4P:rvrx.x:cvnGigabyteTechnologyCo.,Ltd.:ct3:cvr:
  dmi.product.name: P55A-UD4P
  dmi.sys.vendor: Gigabyte Technology Co., Ltd.

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