activate_task()

更新唤醒进程p的平均睡眠时间sleep_avg和动态优先级prio;记录该进程唤醒前的睡眠状态；将该进程插入活跃优先级数组

---

static void activate_task(task_t *p, runqueue_t *rq, int local)
{
    unsigned long long now;
    now = sched_clock();

如果目标CPU不是本地CPU，就要补偿本地时钟器中断的偏差，这是通过计算本地CPU和目标CPU上最近一次发生时钟中断的相对时间戳来达到的
|---------------------------------------------------|
|#ifdef CONFIG_SMP                                  |
|   if (!local) {                                   |
|       runqueue_t *this_rq = this_rq();            |
|       now = (now - this_rq->timestamp_last_tick)  |
|           + rq->timestamp_last_tick;              |
|   }                                               |
|#endif                                             |
|---------------------------------------------------|

更新唤醒进程p的平均睡眠时间sleep_avg和动态优先级prio
|--------------------------------|
|   recalc_task_prio(p, now);    |
|--------------------------------|

记录该进程唤醒前的睡眠状态，如果是中断服务程序调用的activate_task()，也就是说进程由中断激活，则该进程最有可能是交互式的，因此，置activated=2；否则置activated=1
|-----------------------------|
|   if (!p->activated) {      |
|       if (in_interrupt())   |
|           p->activated = 2; |
|       else {                |
|           p->activated = 1; |
|       }                     |
|   }                         |
|-----------------------------|

    p->timestamp = now;

将进程p插入可执行队列rq的活跃优先级数组rq->active中
|----------------------------|
|   __activate_task(p, rq);  |
|----------------------------|
}


static inline void __activate_task(task_t *p, runqueue_t *rq)
{
    enqueue_task(p, rq->active);
    rq->nr_running++;
}



static void enqueue_task(struct task_struct *p, prio_array_t *array)
{
    sched_info_queued(p);
    list_add_tail(&p->run_list, array->queue + p->prio);
    __set_bit(p->prio, array->bitmap);
    array->nr_active++;
    p->array = array;
}