thread_create_core  776 thread.c           return thread_create_core(rb_thread_alloc(klass), args, 0);
thread_create_core  803 thread.c           return thread_create_core(thread, args, 0);
thread_create_core  809 thread.c           return thread_create_core(rb_thread_alloc(rb_cThread), (VALUE)arg, fn);