Make cgroup.threads file delegatable.
The behavior of cgroup.threads should follow the behavior of cgroup.procs.
Signed-off-by: Roman Gushchin <guro@fb.com>
Discovered-by: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
        },
        {
                .name = "cgroup.threads",
+               .flags = CFTYPE_NS_DELEGATABLE,
                .release = cgroup_procs_release,
                .seq_start = cgroup_threads_start,
                .seq_next = cgroup_procs_next,