code: private void tryCreateExternalQueue(int index) {
          AuxState aux;
          if ((aux = auxState) != null && index >= 0) {
              WorkQueue q = new WorkQueue(this, null);
              q.config = index;
              q.scanState = ~UNSIGNALLED;
              q.qlock = 1;                   // lock queue
              boolean installed = false;
              aux.lock();
              try {                          // lock pool to install
                  WorkQueue[] ws;
                  if ((ws = workQueues) != null && index < ws.length &&
                      ws[index] == null) {
                      ws[index] = q;         // else throw away
                      installed = true;
                  }
              } finally {
                  aux.unlock();
              }
              if (installed) {
                  try {
                      q.growArray();
                  } finally {
                      q.qlock = 0;
                  }
              }
          }
      }
docs: Constructs and tries to install a new external queue,
  failing if the workQueues array already has a queue at
  the given index.
  
  @param index the index of the new queue