code: private void eventuallyExpand(int _segmentIndex) {
      long[] _stamps = lockAll();
      try {
        long _size = segmentSize[_segmentIndex].get();
        if (_size <= segmentMaxFill) {
          return;
        }
        rehash();
      } finally {
        unlockAll(_stamps);
      }
    }
docs: Acquire all segment locks and rehash, if really needed.