private V value;
      private Throwable exception;

      /*
       * Acquisition succeeds if the future is done, otherwise it fails.
       */
      @Override
      protected int tryAcquireShared(int ignored) {
        if (isDone()) {
          return 1;
        }
        return -1;
      }

      /*
       * We always allow a release to go through, this means the state has been