Softnet_data

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;
 };