网络子系统3_do_softirq调用点

//中断退出时1.void irq_exit(void){       ...       //递减中断嵌套深度       sub_preempt_count(IRQ_EXIT_OFFSET);       //如果已经退出中断，并且软中断标志被置位       if (!in_interrupt() && local_softirq_pending())       //执行软中断           do_softirq();                  ...}//APIC时钟中断中2.void __irq_entry smp_apic_timer_interrupt(struct pt_regs *regs){        ...        irq_exit();        ...}//重新激活下半部时3.void local_bh_enable(void){        _local_bh_enable_ip((unsigned long)__builtin_return_address(0));}static inline void _local_bh_enable_ip(unsigned long ip){...        if (unlikely(!in_interrupt() && local_softirq_pending()))                do_softirq();        ...}