code: def _lockstep_fcn(values):
      
      numrequired, fcn, args = values
      with _process_lock:
          _numdone.value += 1
      # yep this is an ugly busy loop, do something better please
      # when we care about the performance of this call and not just the
      # guarantee it provides (ok... maybe never)
      while 1:
          if _numdone.value == numrequired:
              return fcn(args)
docs: Wrapper to ensure that all processes execute together