Ah, nevermind; it wanted to write /sys/fs/cgroup/cpuset//cgroup.clone_children, which is probably an artifact of cpuset not being included in the "join all controllers" bits.
Ah, nevermind; it wanted to write /sys/fs/ cgroup/ cpuset/ /cgroup. clone_children, which is probably an artifact of cpuset not being included in the "join all controllers" bits.