thread_create_core  527 thread.c           return thread_create_core(rb_thread_alloc(klass), args, 0);
thread_create_core  553 thread.c           return thread_create_core(thread, args, 0);
thread_create_core  559 thread.c           return thread_create_core(rb_thread_alloc(rb_cThread), (VALUE)arg, fn);