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[Jürg Häfliger <1949532@xxxxxxxxxxxxxxxxxx>]

** Tags added: kernel-daily-bug

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https://bugs.launchpad.net/bugs/1949532

Title:
  ubuntu_ltp_controllers tests failing on Impish ($cgroup_name already
  mounted or mount point busy)

Status in ubuntu-kernel-tests:
  Fix Released
Status in linux package in Ubuntu:
  Invalid
Status in linux source package in Impish:
  Won't Fix

Bug description:
  Almost half of the ubuntu_ltp_controllers tests (142 out of 198) are
  failing due to the general pattern 'cgroup_name already mounted or
  mount point busy' causing the tests to fail.

  e.g.
  mount: /dev/cgroup: ltp_cgroup already mounted or mount point busy.
  cgroup_fj_function2_memory 1 TBROK: mount -t cgroup -o memory ltp_cgroup /dev/cgroup failed

  From investigation it seems there could be an issue with the
  transition to cgroup-v2. There have been rumors on the ltp mailing
  list that one of these days the tests could break due to the
  transition. Switching to cgroup-v2, likely due to a systemd update,
  could cause these tests to break due to different mount and cgroup
  hierarchy semantics.

  I could only reproduce a subset of the new failures we are seeing, but
  after setting systemd.unified_cgroup_hierarchy=0 on the kernel command
  line which sets cgroup back to v1, a lot of the failures I could
  produce went away.

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