Cgroup hung system with rt patch, tested under 4.4.32/4.4.66/4.9.30

[Journey Journey]

Hi RT Devs,

I enabled cpu/cpuacct/cpuset/devices/freezer subsystems in cgroup.

Attach serveral thread ids to these systems' tasks file frequently
last 4 or 5 hours(start process,  echo thread ids to tasks, stop
process). The system will hung, no response to user keyboard input.
Through I have enabled kdmp, but this scenario didn't trigger kdump.

Pls help.


Thanks