內核軟中斷的延遲執行

 static int ksoftirqd(void * __bind_cpu)
362 {
363         int bind_cpu = (int) (long) __bind_cpu;
364         int cpu = cpu_logical_map(bind_cpu);
365 
366         daemonize();
367         current->nice = 19;
368         sigfillset(&current->blocked);
369 
370         /* Migrate to the right CPU */
371         current->cpus_allowed = 1UL << cpu;
372         while (smp_processor_id() != cpu)
373                 schedule();
374 
375         sprintf(current->comm, "ksoftirqd_CPU%d", bind_cpu);
376 
377         __set_current_state(TASK_INTERRUPTIBLE);
378         mb();
379 
380         ksoftirqd_task(cpu) = current;
381 
382         for (;;) {
383                 if (!softirq_pending(cpu))
384                         schedule();
385 
386                 __set_current_state(TASK_RUNNING);
387 
388                 while (softirq_pending(cpu)) {
389                         do_softirq();
390                         if (current->need_resched) /*進行調度，以防長期佔用CPU*/
391                                 schedule();
392                 }
393 
394                 __set_current_state(TASK_INTERRUPTIBLE);
395         }
396 }

 61 asmlinkage void do_softirq()
 62 {
 63         int cpu = smp_processor_id();
 64         __u32 pending;
 65         unsigned long flags;
 66         __u32 mask;
 67 
 68         if (in_interrupt())
 69                 return;
 70 
 71         local_irq_save(flags);
 72 
 73         pending = softirq_pending(cpu);
 74 
 75         if (pending) {
 76                 struct softirq_action *h;
 77 
 78                 mask = ~pending;
 79                 local_bh_disable();
 80 restart:
 81                 /* Reset the pending bitmask before enabling irqs */
 82                 softirq_pending(cpu) = 0;
 83 
 84                 local_irq_enable();
 85 
 86                 h = softirq_vec;
 87 
 88                 do {
 89                         if (pending & 1)
 90                                 h->action(h); /* 執行註冊的handler */
 91                         h++;
 92                         pending >>= 1;
 93                 } while (pending);
 94 
 95                 local_irq_disable();
 96 
 97                 pending = softirq_pending(cpu);
 98                 if (pending & mask) {
 99                         mask &= ~pending;
100                         goto restart;
101                 }
102                 __local_bh_enable();
103 
104                 if (pending)
105                         wakeup_softirqd(cpu);
106         }
107 
108         local_irq_restore(flags);
109 }