Wrap rb_objspace_reachable_objects_from_root with RB_VM_LOCK
rb_objspace_reachable_objects_from has it too, so I figure it's most likely required for _from_root as well.
Wrap rb_objspace_reachable_objects_from_root with RB_VM_LOCK
rb_objspace_reachable_objects_from has it too, so I figure it's most
likely required for _from_root as well.