bool do_card_ptr(jbyte* card_ptr, int worker_i) {

  {- -------------------------------------------
  (1) G1RemSet::concurrentRefineOneCard() を呼び出して, 処理を行う.
      ---------------------------------------- -}

        bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false);
        // This path is executed by the concurrent refine or mutator threads,
        // concurrently, and so we do not care if card_ptr contains references
        // that point into the collection set.
        assert(!oops_into_cset, "should be");

  {- -------------------------------------------
  (1) 一旦待機する必要があれば false, そうでなければ true をリターンする.
      ---------------------------------------- -}

        if (_concurrent && _sts->should_yield()) {
          // Caller will actually yield.
          return false;
        }
        // Otherwise, we finished successfully; return true.
        return true;
      }