PowerPC芯片PPC4601移植RT-Thread问题：线程不调度

int rtthread_startup(void)
{
    rt_hw_interrupt_disable();
    /* board level initialization
     * NOTE: please initialize heap inside board initialization.
     */
    rt_hw_board_init();
    /* show RT-Thread version */
    rt_show_version();
    /* timer system initialization */
    rt_system_timer_init();
    /* scheduler system initialization */
    rt_system_scheduler_init();
#ifdef RT_USING_SIGNALS
    /* signal system initialization */
    rt_system_signal_init();
#endif
    /* create init_thread */
    rt_application_init();
    /* timer thread initialization */
    rt_system_timer_thread_init();
    /* idle thread initialization */
    rt_thread_idle_init();
#ifdef RT_USING_SMP
    rt_hw_spin_lock(&_cpus_lock);
#endif /*RT_USING_SMP*/
    /* start scheduler */
    rt_system_scheduler_start();
    /* never reach here */
    return 0;
}