flake TestFreezeBeforeSet on CentOS 7 and 8

[kolyshkin]

Happened once in Cirrus CI (https://cirrus-ci.com/task/5418288451682304?logs=unit_tests#L549) while running CI for #3512

=== RUN   TestFreezeBeforeSet
=== RUN   TestFreezeBeforeSet/slice,skip-devices
    freeze_test.go:171: failed to write "0\n": write /sys/fs/cgroup/cpuset/system.slice/system-runc_test_freeze_1.slice/cpuset.mems: no such device
=== RUN   TestFreezeBeforeSet/scope,skip-devices
=== RUN   TestFreezeBeforeSet/slice,will-freeze
=== RUN   TestFreezeBeforeSet/slice,pre-frozen,will-freeze
=== RUN   TestFreezeBeforeSet/scope,pre-frozen,skip-devices
=== RUN   TestFreezeBeforeSet/scope,pre-frozen
--- FAIL: TestFreezeBeforeSet (0.41s)
    --- FAIL: TestFreezeBeforeSet/slice,skip-devices (0.06s)
    --- PASS: TestFreezeBeforeSet/scope,skip-devices (0.07s)
    --- PASS: TestFreezeBeforeSet/slice,will-freeze (0.07s)
    --- PASS: TestFreezeBeforeSet/slice,pre-frozen,will-freeze (0.06s)
    --- PASS: TestFreezeBeforeSet/scope,pre-frozen,skip-devices (0.09s)
    --- PASS: TestFreezeBeforeSet/scope,pre-frozen (0.05s)

I've seen similar bugs but not this one. Filing just to ensure it's not lost.

[kolyshkin]

In general we seem to have a problem with disappearing cgroups on CentOS 7, e.g. from https://cirrus-ci.com/task/5772431724904448 (while testing #3379):

=== RUN   TestPodSkipDevicesUpdate
    systemd_test.go:86: failed to write 6485: write /sys/fs/cgroup/cpuset/system.slice/system-runc_test_podTestPodSkipDevicesUpdate.slice/test-PodSkipDevicesUpdate.scope/cgroup.procs: no such device
--- FAIL: TestPodSkipDevicesUpdate (0.75s)

[kolyshkin]

See also #3351

[kolyshkin]

Similar but a different test:

=== RUN   TestSkipDevicesFalse
time="2022-08-08T20:52:16Z" level=info msg="thaw container after SetUnitProperties failed: open /sys/fs/cgroup/freezer/system.slice/system-runc_test_pods.slice/freezer.state: no such file or directory"
    systemd_test.go:187: failed to write 6493: open /sys/fs/cgroup/net_cls,net_prio/system.slice/system-runc_test_pods.slice/test-SkipDevices.scope/cgroup.procs: no such file or directory
--- FAIL: TestSkipDevicesFalse (0.25s)

[kolyshkin]

Happened again (https://cirrus-ci.com/task/4792862578573312):

=== RUN   TestSkipDevicesFalse
    systemd_test.go:136: read /sys/fs/cgroup/cpuset/system.slice/system-runc_test_pods.slice/cpuset.mems: no such device
--- FAIL: TestSkipDevicesFalse (0.13s)

[kolyshkin]

Happened again, this time on CentOS Stream 8 (https://cirrus-ci.com/task/4931391389958144)

=== RUN   TestFreezeBeforeSet/slice,will-freeze
    freeze_test.go:170: failed to write "0-3\n": write /sys/fs/cgroup/cpuset/system.slice/system-runc_test_freeze_3.slice/cpuset.cpus: no such device
=== RUN   TestFreezeBeforeSet/slice,pre-frozen,will-freeze
=== RUN   TestFreezeBeforeSet/scope,pre-frozen,skip-devices
=== RUN   TestFreezeBeforeSet/scope,pre-frozen
--- FAIL: TestFreezeBeforeSet (0.14s)
    --- PASS: TestFreezeBeforeSet/slice,skip-devices (0.01s)
    --- PASS: TestFreezeBeforeSet/scope,skip-devices (0.03s)
    --- FAIL: TestFreezeBeforeSet/slice,will-freeze (0.01s)
    --- PASS: TestFreezeBeforeSet/slice,pre-frozen,will-freeze (0.01s)
    --- PASS: TestFreezeBeforeSet/scope,pre-frozen,skip-devices (0.05s)
    --- PASS: TestFreezeBeforeSet/scope,pre-frozen (0.01s)

[kolyshkin]

Another failure on CentOS 7:

=== RUN   TestFreezeBeforeSet/slice,skip-devices
    freeze_test.go:170: open /sys/fs/cgroup/cpuset/system.slice/cpuset.cpus: no such file or directory
=== RUN   TestFreezeBeforeSet/scope,skip-devices
=== RUN   TestFreezeBeforeSet/slice,will-freeze
=== RUN   TestFreezeBeforeSet/slice,pre-frozen,will-freeze
=== RUN   TestFreezeBeforeSet/scope,pre-frozen,skip-devices
=== RUN   TestFreezeBeforeSet/scope,pre-frozen
--- FAIL: TestFreezeBeforeSet (0.32s)
    --- FAIL: TestFreezeBeforeSet/slice,skip-devices (0.08s)
    --- PASS: TestFreezeBeforeSet/scope,skip-devices (0.05s)
    --- PASS: TestFreezeBeforeSet/slice,will-freeze (0.05s)
    --- PASS: TestFreezeBeforeSet/slice,pre-frozen,will-freeze (0.04s)
    --- PASS: TestFreezeBeforeSet/scope,pre-frozen,skip-devices (0.06s)
    --- PASS: TestFreezeBeforeSet/scope,pre-frozen (0.04s)

[kolyshkin]

The last one is more interesting as it's really hard to imagine how /sys/fs/cgroup/cpuset/system.slice/cpuset.cpus can ever be non-existent.

[tomaszduda23]

The last one is more interesting as it's really hard to imagine how /sys/fs/cgroup/cpuset/system.slice/cpuset.cpus can ever be non-existent.

You could mount cgroup with noprefix to make it non-exist. See #4443

[kolyshkin]

The last one is more interesting as it's really hard to imagine how /sys/fs/cgroup/cpuset/system.slice/cpuset.cpus can ever be non-existent.

You could mount cgroup with noprefix to make it non-exist. See #4443

Alas it is different in this case as no one remounts cgroupfs in CI.