linux软中断 - Chinaunix - Powered by Discuz!

01.static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp;

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01.enum
02.{
03. HI_SOFTIRQ=0,
04. TIMER_SOFTIRQ,
05. NET_TX_SOFTIRQ,
06. NET_RX_SOFTIRQ,
07. BLOCK_SOFTIRQ,
08. BLOCK_IOPOLL_SOFTIRQ,
09. TASKLET_SOFTIRQ,
10. SCHED_SOFTIRQ,
11. HRTIMER_SOFTIRQ,
12. RCU_SOFTIRQ, /* Preferable RCU should always be the last softirq */
13.
14. NR_SOFTIRQS
15.};

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01.struct softirq_action
02.{
03. void (*action)(struct softirq_action *);
04.};

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01./*初始化软中断*/
02.void open_softirq(int nr, void (*action)(struct softirq_action *))
03.{
04. softirq_vec[nr].action = action;
05.}

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01./*激活软中断*/
02.void raise_softirq(unsigned int nr)
03.{
04. unsigned long flags;
05. /*保存eflags寄存器IF标志的状态值
06. 并禁用本地CPU上得中断*/
07. local_irq_save(flags);
08.
09. raise_softirq_irqoff(nr);
10. local_irq_restore(flags);
11.}

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01./*
02. * This function must run with irqs disabled!
03. */
04.inline void raise_softirq_irqoff(unsigned int nr)
05.{
06. /*把软中断标记为挂起*/
07. __raise_softirq_irqoff(nr);
08.
09. /*
10. * If we're in an interrupt or softirq, we're done
11. * (this also catches softirq-disabled code). We will
12. * actually run the softirq once we return from
13. * the irq or softirq.
14. *
15. * Otherwise we wake up ksoftirqd to make sure we
16. * schedule the softirq soon.
17. */
18. if (!in_interrupt())
19. wakeup_softirqd();/*唤醒本地的内核线程*/
20.}

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01.static int ksoftirqd(void * __bind_cpu)
02.{
03. /*设置进程状态为可中断*/
04. set_current_state(TASK_INTERRUPTIBLE);
05.
06. while (!kthread_should_stop()) {/*不应该马上返回*/
07. preempt_disable();
08. /*实现软中断中一个关键数据结构是每个
09. CPU都有的32位掩码(描述挂起的软中断)，
10. 他存放在irq_cpustat_t数据结构的__softirq_pending
11. 字段中。为了获取或设置位掩码的值，
12. 内核使用宏local_softirq_pending，他选择cpu的
13. 软中断为掩码*/
14. if (!local_softirq_pending()) {/*位掩码为0，标示没有软中断*/
15. preempt_enable_no_resched();
16. schedule();
17. preempt_disable();
18. }
19.
20. __set_current_state(TASK_RUNNING);
21.
22. while (local_softirq_pending()) {
23. /* Preempt disable stops cpu going offline.
24. If already offline, we'll be on wrong CPU:
25. don't process */
26. if (cpu_is_offline((long)__bind_cpu))
27. goto wait_to_die;
28. do_softirq();/*调用软中断处理函数*/
29. preempt_enable_no_resched();
30. cond_resched();
31. preempt_disable();
32. rcu_sched_qs((long)__bind_cpu);
33. }
34. preempt_enable();
35. set_current_state(TASK_INTERRUPTIBLE);
36. }
37. __set_current_state(TASK_RUNNING);
38. return 0;
39.
40.wait_to_die:
41. preempt_enable();
42. /* Wait for kthread_stop */
43. set_current_state(TASK_INTERRUPTIBLE);
44. while (!kthread_should_stop()) {
45. schedule();
46. set_current_state(TASK_INTERRUPTIBLE);
47. }
48. __set_current_state(TASK_RUNNING);
49. return 0;
50.}

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01.<pre class="cpp" name="code">/*如果在这样的一个检查点(local_softirq_pending()不为0)
02.检测到挂起的软中断，内核调用下面函数处理*/
03.asmlinkage void do_softirq(void)
04.{
05. __u32 pending;
06. unsigned long flags;
07.
08. if (in_interrupt())
09. return;
10.
11. local_irq_save(flags);
12.
13. pending = local_softirq_pending();
14.
15. if (pending)
16. __do_softirq();
17.
18. local_irq_restore(flags);
19.}

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01./*读取本地CPU的软中断掩码并执行与每个设置位
02.相关的可延迟函数,__do_softirq只做固定次数的循环
03.然后就返回。如果还有其余挂起的软中断，那么
04.内核线程ksofirqd将会在预期的时间内处理他们*/
05.asmlinkage void __do_softirq(void)
06.{
07. struct softirq_action *h;
08. __u32 pending;
09. /*把循环计数器的值初始化为10*/
10. int max_restart = MAX_SOFTIRQ_RESTART;
11. int cpu;
12. /*把本地CPU(被local_softirq_pending选中的)软件中断的
13. 位掩码复制到局部变量pending中*/
14. pending = local_softirq_pending();
15. account_system_vtime(current);
16. /*增加软中断计数器的值*/
17. __local_bh_disable((unsigned long)__builtin_return_address(0));
18. lockdep_softirq_enter();
19.
20. cpu = smp_processor_id();
21.restart:
22. /* Reset the pending bitmask before enabling irqs */
23. set_softirq_pending(0);/*清除本地CPU的软中断位图，
24. 以便可以激活新的软中断*/
25.
26. /*激活本地中断*/
27. local_irq_enable();
28.
29. h = softirq_vec;
30.
31. do {/*根据pending每一位的的设置，执行对应的软中断
32. 处理函数*/
33. if (pending & 1) {
34. int prev_count = preempt_count();
35. kstat_incr_softirqs_this_cpu(h - softirq_vec);
36.
37. trace_softirq_entry(h, softirq_vec);
38. h->action(h);/*执行注册的具体的软中断函数*/
39. trace_softirq_exit(h, softirq_vec);
40. if (unlikely(prev_count != preempt_count())) {
41. printk(KERN_ERR "huh, entered softirq %td %s %p"
42. "with preempt_count %08x,"
43. " exited with %08x?\n", h - softirq_vec,
44. softirq_to_name[h - softirq_vec],
45. h->action, prev_count, preempt_count());
46. preempt_count() = prev_count;
47. }
48.
49. rcu_bh_qs(cpu);
50. }
51. h++;
52. pending >>= 1;
53. } while (pending);
54.
55. local_irq_disable();
56.
57. pending = local_softirq_pending();
58. if (pending && --max_restart)
59. goto restart;
60.
61. if (pending)/*如果还有挂起的软中断，唤醒内核线程
62. 来处理本地CPU的软中断*/
63. wakeup_softirqd();
64.
65. lockdep_softirq_exit();
66.
67. account_system_vtime(current);
68. _local_bh_enable();/*软中断计数器-1，因而重新激活可延迟函数*/
69.}

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