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[Stefan Bader <stefan.bader@xxxxxxxxxxxxx>]

If /proc/mounts shows nvsvers=4 I would assume as well that nfsv4 is
used. Formally I had the feeling that the examples looked like for
really using nfsv4 one would need to have one entry in /etc/exports
declaring a fsid=0 (iow the root) and then clients would ask for paths
relative to that root. On one hand I *think* that I remember someone
asking on irc and having issues when not following that. Which was
another thing that seemed to have worked before.

For the debugging, I think it does give me a rough idea, just need to
match that up against some code. Which will probably take a bit. But
somehow it appears to try to connect but then to think the socket needs
to be released for some reason. And possibly it either is failing to
release it with some unexpected condition or incorrectly assumes it is
still connected and repeats this forever. Cannot really think of a
reason why this is related (or not) to another server running (at least
yet).

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https://bugs.launchpad.net/bugs/1322407

Title:
  NFS kernel server creates a kworker with 100% CPU usage, then hangs
  randomly

Status in “linux” package in Ubuntu:
  Confirmed

Bug description:
  This concerns the server edition of 14.04. I have set up a NFS server.
  Once I attach at least one client, one kworker process starts to use
  100% CPU. The runaway kworker returns to idle when I reset the NFS
  server daemon with "service nfs-kernel-server stop" followed by
  "service nfs-kernel-server start". With the nfs kernel server stopped,
  the CPU remains idle. With the nfs kernel server running, as soon as
  one client requests a connection, the kworker process jumps to 100%
  CPU again.

  After some random time, the nfs kernel server no longer accepts
  requests from clients. Restarting the service allows clients to
  reconnect. The syslog shows no relevant information.

  This problem has never appeared on a very similar server setup with
  12.04.

  Configration: The svcgssd is not running. I played with various
  configurations (enabling/disabling NFSv3 and NFSv4), but it makes no
  difference.

  I tried to enable event debugging:

  #> echo workqueue:workqueue_queue_work > /sys/kernel/debug/tracing/set_event
  #> cat /sys/kernel/debug/tracing/trace_pipe > /var/tmp/kerntrace.txt

  and found the following kernel trace in a tight loop:

  [...]
       kworker/2:1-86    [002] d... 161940.910668: workqueue_queue_work: work struct=ffff8804140675e0 function=xs_tcp_setup_socket [sunrpc] workqueue=ffff8800cfbb6a00 req_cpu=256 cpu=2
       kworker/2:1-86    [002] d.s. 161940.910674: workqueue_queue_work: work struct=ffff8800cef9f488 function=rpc_async_schedule [sunrpc] workqueue=ffff8800cfbb6a00 req_cpu=256 cpu=2
       kworker/2:1-86    [002] d... 161940.910675: workqueue_queue_work: work struct=ffff8804140675e0 function=xs_tcp_setup_socket [sunrpc] workqueue=ffff8800cfbb6a00 req_cpu=256 cpu=2
       kworker/2:1-86    [002] d.s. 161940.910681: workqueue_queue_work: work struct=ffff8800cef9f488 function=rpc_async_schedule [sunrpc] workqueue=ffff8800cfbb6a00 req_cpu=256 cpu=2
       kworker/2:1-86    [002] d... 161940.910682: workqueue_queue_work: work struct=ffff8804140675e0 function=xs_tcp_setup_socket [sunrpc] workqueue=ffff8800cfbb6a00 req_cpu=256 cpu=2
       kworker/2:1-86    [002] d.s. 161940.910688: workqueue_queue_work: work struct=ffff8800cef9f488 function=rpc_async_schedule [sunrpc] workqueue=ffff8800cfbb6a00 req_cpu=256 cpu=2
       kworker/2:1-86    [002] d... 161940.910689: workqueue_queue_work: work struct=ffff8804140675e0 function=xs_tcp_setup_socket [sunrpc] workqueue=ffff8800cfbb6a00 req_cpu=256 cpu=2
       kworker/2:1-86    [002] d.s. 161940.910695: workqueue_queue_work: work struct=ffff8800cef9f488 function=rpc_async_schedule [sunrpc] workqueue=ffff8800cfbb6a00 req_cpu=256 cpu=2
       kworker/2:1-86    [002] d... 161940.910696: workqueue_queue_work: work struct=ffff8804140675e0 function=xs_tcp_setup_socket [sunrpc] workqueue=ffff8800cfbb6a00 req_cpu=256 cpu=2
       kworker/2:1-86    [002] d.s. 161940.910702: workqueue_queue_work: work struct=ffff8800cef9f488 function=rpc_async_schedule [sunrpc] workqueue=ffff8800cfbb6a00 req_cpu=256 cpu=2
  [...]

  At present, I have to consider NFS fubar.

  Thanks,
  Mark

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: linux-image-3.13.0-24-generic 3.13.0-24.47
  ProcVersionSignature: Ubuntu 3.13.0-24.47-generic 3.13.9
  Uname: Linux 3.13.0-24-generic x86_64
  AlsaVersion: Advanced Linux Sound Architecture Driver Version k3.13.0-24-generic.
  AplayDevices: Error: [Errno 2] No such file or directory: 'aplay'
  ApportVersion: 2.14.1-0ubuntu3.1
  Architecture: amd64
  ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord'
  AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/by-path', '/dev/snd/controlC0', '/dev/snd/hwC0D0', '/dev/snd/pcmC0D0c', '/dev/snd/pcmC0D0p', '/dev/snd/pcmC0D1p', '/dev/snd/pcmC0D2c', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
  CRDA: Error: [Errno 2] No such file or directory: 'iw'
  Card0.Amixer.info: Error: [Errno 2] No such file or directory: 'amixer'
  Card0.Amixer.values: Error: [Errno 2] No such file or directory: 'amixer'
  Date: Thu May 22 22:48:48 2014
  HibernationDevice: RESUME=UUID=adcdeef5-9b46-4ea4-b9f4-b6e642ea91e8
  InstallationDate: Installed on 2014-05-12 (10 days ago)
  InstallationMedia: Ubuntu-Server 14.04 LTS "Trusty Tahr" - Release amd64 (20140416.2)
  IwConfig:
   eth0      no wireless extensions.

   lo        no wireless extensions.
  MachineType: Gigabyte Technology Co., Ltd. GA-990XA-UD3
  ProcEnviron:
   TERM=xterm
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  ProcFB: 0 nouveaufb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.13.0-24-generic root=UUID=6cf411b3-3e8e-41e5-8670-db14ad259f58 ro IOMMU=soft nomdmonddf nomdmonisw
  RelatedPackageVersions:
   linux-restricted-modules-3.13.0-24-generic N/A
   linux-backports-modules-3.13.0-24-generic  N/A
   linux-firmware                             1.127.2
  RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
  SourcePackage: linux
  UpgradeStatus: No upgrade log present (probably fresh install)
  WifiSyslog:

  dmi.bios.date: 10/13/2011
  dmi.bios.vendor: Award Software International, Inc.
  dmi.bios.version: F9
  dmi.board.name: GA-990XA-UD3
  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.:bvrF9:bd10/13/2011:svnGigabyteTechnologyCo.,Ltd.:pnGA-990XA-UD3:pvr:rvnGigabyteTechnologyCo.,Ltd.:rnGA-990XA-UD3:rvrx.x:cvnGigabyteTechnologyCo.,Ltd.:ct3:cvr:
  dmi.product.name: GA-990XA-UD3
  dmi.sys.vendor: Gigabyte Technology Co., Ltd.

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