code: static WorkQueue commonSubmitterQueue() {
          ForkJoinPool p = common;
          int r = ThreadLocalRandom.getProbe();
          WorkQueue[] ws; int wl;
          return (p != null && (ws = p.workQueues) != null &&
                  (wl = ws.length) > 0) ?
              ws[(wl - 1) & r & SQMASK] : null;
      }
docs: Returns common pool queue for an external thread.