tasklet_1

1.

任何时刻只有一个CPU在运行tasklet的处理函数。

在哪个cpu上激活的，就在哪个cpu上运行tasklet的处理函数。

tasklet api:

1. 初始化(init)

515 void tasklet_init(struct tasklet_struct *t,

516                   void (*func)(unsigned long), unsigned long data)

2. 激活(raise)

561 static inline void tasklet_schedule(struct tasklet_struct *t)

515 void tasklet_init(struct tasklet_struct *t,
516                   void (*func)(unsigned long), unsigned long data)
517 {
518         t->next = NULL;
519         t->state = 0;
520         atomic_set(&t->count, 0);
521         t->func = func;
522         t->data = data;
523 }

561 static inline void tasklet_schedule(struct tasklet_struct *t)
562 {
563         if (!test_and_set_bit(TASKLET_STATE_SCHED, &t->state))
564                 __tasklet_schedule(t);
565 }
566

514
515 struct tasklet_struct
516 {
517         struct tasklet_struct *next;
518         unsigned long state;
519         atomic_t count;
520         void (*func)(unsigned long);
521         unsigned long data;
522 };
523

402 static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec);
403 static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec);

393 /*
394 * Tasklets
395 */
396 struct tasklet_head
397 {
398         struct tasklet_struct *head;
399         struct tasklet_struct **tail;
400 };
401

561 static inline void tasklet_schedule(struct tasklet_struct *t)
562 {
563         if (!test_and_set_bit(TASKLET_STATE_SCHED, &t->state))
564                 __tasklet_schedule(t);
565 }
566

405 void __tasklet_schedule(struct tasklet_struct *t)
406 {
407         unsigned long flags;
408
409         local_irq_save(flags);
410         t->next = NULL;
411         *__this_cpu_read(tasklet_vec.tail) = t;
412         __this_cpu_write(tasklet_vec.tail, &(t->next));
413         raise_softirq_irqoff(TASKLET_SOFTIRQ);
414         local_irq_restore(flags);
415 }

444 static void tasklet_action(struct softirq_action *a)
445 {
446 struct tasklet_struct *list;
447
448 local_irq_disable();
449 list = __this_cpu_read(tasklet_vec.head);
450 __this_cpu_write(tasklet_vec.head, NULL);
451 __this_cpu_write(tasklet_vec.tail, &__get_cpu_var(tasklet_vec).head);
452 local_irq_enable();
453
454 while (list) {
455 struct tasklet_struct *t = list;
456
457 list = list->next;
458
459 if (tasklet_trylock(t)) {
460 if (!atomic_read(&t->count)) {
461 if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
462 BUG();
463 t->func(t->data);
464 tasklet_unlock(t);
465 continue;
466 }
467 tasklet_unlock(t);
468 }
469
470 local_irq_disable();
471 t->next = NULL;
472 *__this_cpu_read(tasklet_vec.tail) = t;
473 __this_cpu_write(tasklet_vec.tail, &(t->next));
474 __raise_softirq_irqoff(TASKLET_SOFTIRQ);
475 local_irq_enable();
476 }
477 }