cgroup_attach_lock
void cgroup_attach_lock(enum cgroup_attach_lock_mode lock_mode,
cgroup_attach_lock(CGRP_ATTACH_LOCK_GLOBAL, NULL);
cgroup_attach_lock(CGRP_ATTACH_LOCK_GLOBAL, NULL);
cgroup_attach_lock(*lock_mode, tsk);
cgroup_attach_lock(lock_mode, NULL);