code: private int acquireExpedite() {
          int a;
          while ((a = expeditesAvailable.get()) > 0 && !expeditesAvailable.compareAndSet(a, a - 1));
          return a; // returning the value rather than true/false will enable better debug
      }
docs: Attempt to acquire a permit to expedite, which involves decrementing the available expedites.
  Only allow decrement of a positive value, and otherwise indicate there are no available expedites.
  
  @return number of available expedites at the time we acquired a permit. 0 if none remains and we did not get a permit.