void MarkingCodeBlobClosure::do_code_blob(CodeBlob* cb) {

      nmethod* nm = cb->as_nmethod_or_null();
      if (nm == NULL)  return;
      if (!nm->test_set_oops_do_mark()) {
        NOT_PRODUCT(if (TraceScavenge)  nm->print_on(tty, "oops_do, 1st visit\n"));
        do_newly_marked_nmethod(nm);
      } else {
        NOT_PRODUCT(if (TraceScavenge)  nm->print_on(tty, "oops_do, skipped on 2nd visit\n"));
      }
    }