kernel-packages team mailing list archive

[Mark Haidekker <mhaidekk@xxxxxxxxx>]

I made one more observation, and it is fully reproducible. Frankly, it
would appear that the bug may not be as impactful as originally though
(if this is a bug, to begin with). Here it is:

On one of the Linux clients, Windows runs in Virtualbox. The NFS share
is mounted within the Linux host, and the mount point is available in
the virtual environment as a vboxdrv shared folder. Within Windows, the
user uses a translation automation tool called "Trados".  If -- and only
if -- this program is running, the apparent runaway kworker uses 100%
CPU. When Trados is closed, the CPU core returns to idle within ~20 to
30 seconds.

This, finally, explains many observations I made before, which are mere
coincidences. It also explains why a second NFS server that I brought
online today does not exhibit the runaway behavior. Only the combination
of all three: NFS, Virtualbox (Win 7 guest), and Trados, puts a heavy
load on the rpc daemon. No other Windows program in the virtual box does
that.

Why and how? I used tcpdump to see if anything insane is going on, but
it is not -- neither on the client's physical eth0 interface nor on the
virtual vboxnet0 interface. I did not find anything suspicious. Also, I
cannot explain why the old 10.04 NFS server didn't show this behavior.
NFSv3 perhaps? And why does it affect the rpc daemon?

In conclusion, I believe that I found the cause (albeit not the reason)
for the runaway behavior. I also believe that the combination of
software packages is very unusual, and this bug is not likely to affect
many people. I propose to reduce the importance level of this bug to
"low".

Latsly, it makes me shudder to think about what Trados might do to the
hard disks of people who use it locally, with natively installed
Windows.

-- 
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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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