static int dev_cpu_dead(unsigned int oldcpu)

 {

     struct sk_buff **list_skb;

     struct sk_buff *skb;

     unsigned int cpu;

     struct softnet_data *sd, *oldsd, *remsd = NULL;

     //禁用本地中断

     local_irq_disable();

     //获取当前cpu

     cpu = smp_processor_id();

     //找到sd

     sd = &per_cpu(softnet_data, cpu);

     //原sd

     oldsd = &per_cpu(softnet_data, oldcpu);

     /* Find end of our completion_queue. */

     //找到当前cpu完成队列尾部

     list_skb = &sd->completion_queue;

     while (*list_skb)

         list_skb = &(*list_skb)->next;

     /* Append completion queue from offline CPU. */

     //将旧cpu队列连接到当前cpu队列尾部

     *list_skb = oldsd->completion_queue;

     oldsd->completion_queue = NULL;

     /* Append output queue from offline CPU. */

     //将旧cpu的outputqueue挂到当前cpu尾部

     if (oldsd->output_queue) {

         *sd->output_queue_tailp = oldsd->output_queue;

         sd->output_queue_tailp = oldsd->output_queue_tailp;

         oldsd->output_queue = NULL;

         oldsd->output_queue_tailp = &oldsd->output_queue;

     }

     /* Append NAPI poll list from offline CPU, with one exception :

      * process_backlog() must be called by cpu owning percpu backlog.

      * We properly handle process_queue & input_pkt_queue later.

      */

     //将napi poll list挂到当前cpu poll list尾部

     while (!list_empty(&oldsd->poll_list)) {

         struct napi_struct *napi = list_first_entry(&oldsd->poll_list,

                                 struct napi_struct,

                                 poll_list);

         list_del_init(&napi->poll_list);

         if (napi->poll == process_backlog)

             napi->state = ;

         else

             ____napi_schedule(sd, napi);

     }

     //触发发送软中断

     raise_softirq_irqoff(NET_TX_SOFTIRQ);

     //启用中断

     local_irq_enable();

 #ifdef CONFIG_RPS

     remsd = oldsd->rps_ipi_list;

     oldsd->rps_ipi_list = NULL;

 #endif

     /* send out pending IPI's on offline CPU */

     net_rps_send_ipi(remsd);

     /* Process offline CPU's input_pkt_queue */

     //把process_queue和input_queue中的skb添加到当前cpu的backlog中

     while ((skb = __skb_dequeue(&oldsd->process_queue))) {

         netif_rx_ni(skb);

         input_queue_head_incr(oldsd);

     }

     while ((skb = skb_dequeue(&oldsd->input_pkt_queue))) {

         netif_rx_ni(skb);

         input_queue_head_incr(oldsd);

     }

     return ;

 }