code: final int externalHelpComplete(CountedCompleter<?> task, int maxTasks) {
          WorkQueue[] ws; int wl;
          int r = ThreadLocalRandom.getProbe();
          return ((ws = workQueues) != null && (wl = ws.length) > 0) ?
              helpComplete(ws[(wl - 1) & r & SQMASK], task, maxTasks) : 0;
      }
docs: Performs helpComplete for an external submitter.