5 进入临界区时, 中断可抢占?

void rt_enter_critical(void)
{
    register rt_base_t level;
    /* disable interrupt */
    level = rt_hw_interrupt_disable();
    /*
     * the maximal number of nest is RT_UINT16_MAX, which is big
     * enough and does not check here
     */
    rt_scheduler_lock_nest ++;
    /* enable interrupt */
    rt_hw_interrupt_enable(level);
}
#endif /*RT_USING_SMP*/
RTM_EXPORT(rt_enter_critical);