Public bug reported:

Almost half of the ubuntu_ltp_controllers tests 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's an issue with the transition to
cgroup-v2, which on the ltp mailing list has been rumored that one of
these days the tests would break. Its likely this was caused by a
systemd update, switching to cgroup-v2 causing these tests to break due
to different mount and cgroup hierarchy semantics.

After setting systemd.unified_cgroup_hierarchy=0 on the kernel command
line which sets cgroup back to v1, we get the expected failures that we
saw in previous cycles, pointing to this not being a kernel regression.

** Affects: ubuntu-kernel-tests
     Importance: Undecided
         Status: New

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: 5.13 hinted impish linux-kvm sru-20211018 ubuntu-ltp 
ubuntu-ltp-controllers

** Also affects: ubuntu-kernel-tests
   Importance: Undecided
       Status: New

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

Title:
  ubuntu_ltp_controllers tests failing on Impish

Status in ubuntu-kernel-tests:
  New
Status in linux package in Ubuntu:
  New

Bug description:
  Almost half of the ubuntu_ltp_controllers tests 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's an issue with the transition to
  cgroup-v2, which on the ltp mailing list has been rumored that one of
  these days the tests would break. Its likely this was caused by a
  systemd update, switching to cgroup-v2 causing these tests to break
  due to different mount and cgroup hierarchy semantics.

  After setting systemd.unified_cgroup_hierarchy=0 on the kernel command
  line which sets cgroup back to v1, we get the expected failures that
  we saw in previous cycles, pointing to this not being a kernel
  regression.

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