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[Brad Figg <brad.figg@xxxxxxxxxxxxx>]

This bug is missing log files that will aid in diagnosing the problem.
>From a terminal window please run:

apport-collect 1588056

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable
to run this command, please add a comment stating that fact and change
the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the
Ubuntu Kernel Team.

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

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https://bugs.launchpad.net/bugs/1588056

Title:
  cgroupfs mounts can hang

Status in linux package in Ubuntu:
  Incomplete

Bug description:
  Consider the following,

  root@dev:/tmp# mkdir foo
  root@dev:/tmp# mount -t cgroup -o none,name=foo none foo
  root@dev:/tmp# mkdir -p foo/bad
  root@dev:/tmp# umount -l foo
  root@dev:/tmp# mount -t cgroup -o none,name=foo none foo # hangs forever
  ^C
  root@dev:/tmp# uname -a
  Linux dev 4.4.0-22-generic #40-Ubuntu SMP Thu May 12 22:03:46 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

  When I strace the mount task, I get a whole bunch of,

  mount("none", "/tmp/foo", "cgroup", MS_MGC_VAL, "none,name=foo") = ? ERESTARTNOINTR (To be restarted)
  mount("none", "/tmp/foo", "cgroup", MS_MGC_VAL, "none,name=foo") = ? ERESTARTNOINTR (To be restarted)
  mount("none", "/tmp/foo", "cgroup", MS_MGC_VAL, "none,name=foo") = ? ERESTARTNOINTR (To be restarted)
  mount("none", "/tmp/foo", "cgroup", MS_MGC_VAL, "none,name=foo") = ? ERESTARTNOINTR (To be restarted)
  mount("none", "/tmp/foo", "cgroup", MS_MGC_VAL, "none,name=foo") = ? ERESTARTNOINTR (To be restarted)
  mount("none", "/tmp/foo", "cgroup", MS_MGC_VAL, "none,name=foo") = ? ERESTARTNOINTR (To be restarted)
  mount("none", "/tmp/foo", "cgroup", MS_MGC_VAL, "none,name=foo") = ? ERESTARTNOINTR (To be restarted)
  mount("none", "/tmp/foo", "cgroup", MS_MGC_VAL, "none,name=foo") = ? ERESTARTNOINTR (To be restarted)
  mount("none", "/tmp/foo", "cgroup", MS_MGC_VAL, "none,name=foo") = ? ERESTARTNOINTR (To be restarted)
  mount("none", "/tmp/foo", "cgroup", MS_MGC_VAL, "none,name=foo") = ? ERESTARTNOINTR (To be restarted)
  mount("none", "/tmp/foo", "cgroup", MS_MGC_VAL, "none,name=foo") = ? ERESTARTNOINTR (To be restarted)
  mount("none", "/tmp/foo", "cgroup", MS_MGC_VAL, "none,name=foo") = ? ERESTARTNOINTR (To be restarted)
  mount("none", "/tmp/foo", "cgroup", MS_MGC_VAL, "none,name=foo") = ? ERESTARTNOINTR (To be restarted)
  mount("none", "/tmp/foo", "cgroup", MS_MGC_VAL, "none,name=foo") = ? ERESTARTNOINTR (To be restarted)
  mount("none", "/tmp/foo", "cgroup", MS_MGC_VAL, "none,name=foo") = ? ERESTARTNOINTR (To be restarted)
  mount("none", "/tmp/foo", "cgroup", MS_MGC_VAL, "none,name=foo") = ? ERESTARTNOINTR (To be restarted)
  mount("none", "/tmp/foo", "cgroup", MS_MGC_VAL, "none,name=foo") = ? ERESTARTNOINTR (To be restarted)

  Which I think means that we're looping on,

  https://github.com/torvalds/linux/blob/master/kernel/cgroup.c#L2137

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