code: private WorkQueue findNonEmptyStealQueue() {
          WorkQueue[] ws; int wl;  // one-shot version of scan loop
          int r = ThreadLocalRandom.nextSecondarySeed();
          if ((ws = workQueues) != null && (wl = ws.length) > 0) {
              int m = wl - 1, origin = r & m;
              for (int k = origin, oldSum = 0, checkSum = 0;;) {
                  WorkQueue q; int b;
                  if ((q = ws[k]) != null) {
                      if ((b = q.base) - q.top < 0)
                          return q;
                      checkSum += b;
                  }
                  if ((k = (k + 1) & m) == origin) {
                      if (oldSum == (oldSum = checkSum))
                          break;
                      checkSum = 0;
                  }
              }
          }
          return null;
      }
docs: Returns a (probably) non-empty steal queue, if one is found
  during a scan, else null.  This method must be retried by
  caller if, by the time it tries to use the queue, it is empty.