process_backlog函数

kernel:linux-2.6.18

/* net_rx_action会把剩下budget传递给process_backlog */
static int process_backlog(struct net_device *backlog_dev, int *budget)
{
    int work = 0;
    /* 获取最小配额值，即sk_buff 数量 */
    int quota = min(backlog_dev->quota, *budget);
    struct softnet_data *queue = &__get_cpu_var(softnet_data);
    unsigned long start_time = jiffies;

    backlog_dev->weight = weight_p;

    /* 循环执行直到__skb_dequeue取出的skb为NULL*/
    for (;;) {
        struct sk_buff *skb;
        struct net_device *dev;

        local_irq_disable();
        /* 从双向链表中取出sk_buff指针 */
        skb = __skb_dequeue(&queue->input_pkt_queue);
        if (!skb)
            goto job_done;
        local_irq_enable();

        dev = skb->dev;

        /* 把sk_buff送入上层协议进行处理 */
        netif_receive_skb(skb);

        dev_put(dev);

        work++;
        /*
        (jiffies - start_time>1)保证执行时间超过一个时间片
        work >= quota表明从queue->input_pkt_queue中取出的sk_buff数量超过预先设定的quota值
        */

        if (work >= quota || jiffies - start_time > 1)
            break;

    }
    /* 更新配额 */
    backlog_dev->quota -= work;
    /* 更新预算 */
    *budget -= work;
    return -1;

job_done:
    backlog_dev->quota -= work;
    *budget -= work;

    /* 处理成功后，从链表删除 */
    list_del(&backlog_dev->poll_list);
    smp_mb__before_clear_bit();
    /* 清空__LINK_STATE_RX_SCHED，表明接收状态完毕 */
    netif_poll_enable(backlog_dev);

    local_irq_enable();
    return 0;
}