When cpuset of a container (docker/lxc both uses underlying cgroup) becomes empty (due to hotplug/hotunplug) then processes running in that container can be scheduled on any cpus in cpuset of its nearest non-empty ancestor.
    But, when cpuset of a running container (docker/lxc)becomes non-empty from an empty state (adding cpu to the empty cpuset) by updating the cpuset of the running container (by using echo method), the  processes running in that container still uses the same cpuset as that of its nearest non-empty ancestor.