Softnet_data的初始化：

每个CPU的softnet_data是在net_dev_init中初始化的，代码如下：

  "/net/core/dev.c" "static int __init net_dev_init(void)"

  for_each_possible_cpu(i) {

  struct softnet_data *queue;

  queue = &per_cpu(softnet_data, i);

  skb_queue_head_init(&queue->input_pkt_queue);

  queue->completion_queue = NULL;

  INIT_LIST_HEAD(&queue->poll_list);

 queue->backlog.poll = process_backlog;

 queue->backlog.weight = weight_p;

 queue->backlog.gro_list = NULL;

 queue->backlog.gro_count = ;

 }

 "include/linux/netdevice.h"

 struct softnet_data

 {

         struct Qdisc            *output_queue;

         struct sk_buff_head     input_pkt_queue;

         struct list_head        poll_list;

         struct sk_buff          *completion_queue;

         struct napi_struct      backlog;

 };

 struct napi_struct {

         /* The poll_list must only be managed by the entity which

29          * changes the state of the NAPI_STATE_SCHED bit.  This means

30          * whoever atomically sets that bit can add this napi_struct

31          * to the per-cpu poll_list, and whoever clears that bit

32          * can remove from the list right before clearing the bit.

33          */

         struct list_head        poll_list;

         unsigned long           state;

         int                     weight;

         int                     (*poll)(struct napi_struct *, int);

 #ifdef CONFIG_NETPOLL

         spinlock_t              poll_lock;

         int                     poll_owner;

 #endif

         unsigned int            gro_count;

         struct net_device       *dev;

         struct list_head        dev_list;

         struct sk_buff          *gro_list;

         struct sk_buff          *skb;

 };