code: static final void cancelIgnoringExceptions(ForkJoinTask<?> t) {
          if (t != null && t.status >= 0) {
              try {
                  t.cancel(false);
              } catch (Throwable ignore) {
              }
          }
      }
docs: Cancels, ignoring any exceptions thrown by cancel. Used during
  worker and pool shutdown. Cancel is spec'ed not to throw any
  exceptions, but if it does anyway, we have no recourse during
  shutdown, so guard against this case.