final RubyThread rubyThread = new RubyThread(runtime, (RubyClass) recv);
rubyThread.threadImpl = new NativeThread(rubyThread, t);
ThreadContext context = runtime.getThreadService().registerNewThread(rubyThread);
context.preAdoptThread();
// set to default thread group
runtime.getDefaultThreadGroup().addDirectly(rubyThread);
return rubyThread;