After 8231999, it seems the test stuck inside the following loop:

 public static void testGC(boolean clear, boolean precompile) throws Throwable {

...

       do {
            System.gc();
            try {
                Reference ref1 = rq.remove(100);
                if (ref1 == ref) {
                    break;
                }
            } catch(InterruptedException e) { /* ignore */ }
        } while (true);