eval.c:9203
void
rb_thread_sleep_forever()
{
    if (curr_thread == curr_thread->next ||
	curr_thread->status == THREAD_TO_KILL) {
	TRAP_BEG;
	pause();
	TRAP_END;
	return;
    }

    curr_thread->delay = DELAY_INFTY;
    curr_thread->wait_for = WAIT_TIME;
    curr_thread->status = THREAD_STOPPED;
    rb_thread_schedule();
}
