If you pass --nodeps to start or restart the cgroup is not created. This is a problem especially for udev. UDev expects to run in its own cgroup and may kill random processes from its cgroup in the wake of a trigger event. So if the cgroup is the root one then typically sshd dies (not cool for physical remote machines where console access is difficult).
Steps to Reproduce:
1. /etc/init.d/udev -D restart
2. ls -ld /sys/fs/cgroup/unified/udev
3. /etc/init.d/udev restart
4. ls -ld /sys/fs/cgroup/unified/udev
cgroup is not created
cgroup should be created also with --nodeps