} while (oldHead != Waiter.TOMBSTONE);
      }
      // re-read value, if we get here then we must have observed a TOMBSTONE while trying to add a
      // waiter.
      // requireNonNull is safe because value is always set before TOMBSTONE.
      return getDoneValue(requireNonNull(value));
    }
    // If we get here then we have remainingNanos < SPIN_THRESHOLD_NANOS and there is no node on the
    // waiters list