code: private void tryPollForAndExec(WorkQueue joiner, ForkJoinTask<?> task) {
          WorkQueue[] ws;
          if ((ws = workQueues) != null) {
              for (int j = 1; j < ws.length && task.status >= 0; j += 2) {
                  WorkQueue q = ws[j];
                  if (q != null && q.pollFor(task)) {
                      joiner.runSubtask(task);
                      break;
                  }
              }
          }
      }
docs: If task is at base of some steal queue, steals and executes it.
  
  @param joiner the joining worker
  @param task the task