生活随笔
收集整理的這篇文章主要介紹了
ARM Linux 如何--注册和触发--软中断
小編覺得挺不錯的,現在分享給大家,幫大家做個參考.
1. 注冊軟中斷當然是通過open_softirq
例子如下：
[cpp]?view plain
?copy void?__init?init_timers(void)??{??????int?err?=?timer_cpu_notify(&timers_nb,?(unsigned?long)CPU_UP_PREPARE,??????????????????(void?*)(long)smp_processor_id());????????init_timer_stats();????????BUG_ON(err?==?NOTIFY_BAD);??????register_cpu_notifier(&timers_nb);??????open_softirq(TIMER_SOFTIRQ,?run_timer_softirq);??}????void?open_softirq(int?nr,?void?(*action)(struct?softirq_action?*))??{??????softirq_vec[nr].action?=?action;??}?? 軟中斷TIMER_SOFTIRQ的中斷處理函數為：run_timer_softirq
之所以成為softirq，是因為這些中斷是由硬件中斷來間接觸發的,如何間接觸發的呢：
硬件中斷處理函數-->對軟中斷的相應位置位-->喚醒ksoftirqd線程-->執行軟中斷的中斷處理函數
?
2. 硬件中斷如何通過置位喚醒ksoftirqd線程
timer interrupt handler->
timer_tick->
update_process_times->
run_local_timers->
hrtimer_run_queues()和raise_softirq(TIMER_SOFTIRQ)->
raise_softirq_irqoff->
__raise_softirq_irqoff { or_softirq_pending(1UL << (nr)); }
即(local_softirq_pending() |= (x))
?
3. 如何執行軟中斷的action<中斷處理函數>
對于TIMER_SOFTIRQ來說，每次system clock產生中斷時，即一個tick 到來時，在system clock的中斷處理函數中會調用run_local_timers來設置TIMER_SOFTIRQ觸發條件；也就是當前CPU對應的irq_cpustat_t結構體中的__softirq_pending成員的第TIMER_SOFTIRQ個BIT被置為1。 而當這個條件滿足時，ksoftirqd線程(入口函數run_ksoftirqd,cpu_callback:kthread_create(run_ksoftirqd, hcpu, "ksoftirqd/%d", hotcpu);)會被喚醒，然后按照下面的流程調用TIMER_SOFTIRQ在數組softirq_vec中注冊的action，即run_timer_softirq。
run_ksoftirqd--->do_softirq--->__do_softirq--->softirq_vec[TIMER_SOFTIRQ].action
?
[cpp]?view plain
?copy static?int?run_ksoftirqd(void?*?__bind_cpu)??{??????set_current_state(TASK_INTERRUPTIBLE);????????while?(!kthread_should_stop())?{??????????preempt_disable();??????????if?(!local_softirq_pending())?{??????????????preempt_enable_no_resched();??????????????schedule();??????????????preempt_disable();??????????}????????????__set_current_state(TASK_RUNNING);????????????while?(local_softirq_pending())?{??????????????????????????if?(cpu_is_offline((long)__bind_cpu))??????????????????goto?wait_to_die;??????????????do_softirq();??????????????preempt_enable_no_resched();??????????????cond_resched();??????????????preempt_disable();??????????????rcu_sched_qs((long)__bind_cpu);??????????}??????????preempt_enable();??????????set_current_state(TASK_INTERRUPTIBLE);??????}??????__set_current_state(TASK_RUNNING);??????return?0;????wait_to_die:??????preempt_enable();??????????set_current_state(TASK_INTERRUPTIBLE);??????while?(!kthread_should_stop())?{??????????schedule();??????????set_current_state(TASK_INTERRUPTIBLE);??????}??????__set_current_state(TASK_RUNNING);??????return?0;??}??
?
?
總結
以上是生活随笔為你收集整理的ARM Linux 如何--注册和触发--软中断的全部內容，希望文章能夠幫你解決所遇到的問題。
如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。
