void rt_system_scheduler_start(void)
{
    register struct rt_thread *to_thread;
    rt_ubase_t highest_ready_priority;
    to_thread = _get_highest_priority_thread(&highest_ready_priority);
#ifdef RT_USING_SMP
    to_thread->oncpu = rt_hw_cpu_id();
#else
    rt_current_thread = to_thread;
#endif /*RT_USING_SMP*/
    rt_schedule_remove_thread(to_thread);
    to_thread->stat = RT_THREAD_RUNNING;
    /* switch to new thread */
#ifdef RT_USING_SMP
    rt_hw_context_switch_to((rt_ubase_t)&to_thread->sp, to_thread);
#else
    rt_kprintf("[%s, %d]\r\n", __func__, __LINE__);
    rt_kprintf("to_thread->name = %s\r\n", to_thread->name);
    rt_kprintf("to_thread->sp = 0x%016X\r\n", to_thread->sp);
    rt_kprintf("to_thread->entry = 0x%016X\r\n", to_thread->entry);
    rt_hw_context_switch_to((rt_ubase_t)&to_thread->sp);
    rt_kprintf("[%s, %d]\r\n", __func__, __LINE__);
#endif /*RT_USING_SMP*/
    /* never come back */
}