Comment 11 for bug 598335

Could this be a duplicate of https://bugs.launchpad.net/ubuntu/+source/libcgroup/+bug/693594?

I had problems with "modprobe -r" hanging, and after that any attempt to do anything with modules also hung. After much testing I discovered that cgroups was to blame, and setting cpu.rt_runtime_us in the sysdefault cgroup as suggested in comment 13 in that bug fixed the problem.