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：
1 "/net/core/dev.c" "static int __init net_dev_init(void)"
2 for_each_possible_cpu(i) {
3 struct softnet_data *queue;
5 queue = &per_cpu(softnet_data, i);
6 skb_queue_head_init(&queue->input_pkt_queue);
7 queue->completion_queue = NULL;
8 INIT_LIST_HEAD(&queue->poll_list);
9
10 queue->backlog.poll = process_backlog;
11 queue->backlog.weight = weight_p;
12 queue->backlog.gro_list = NULL;
13 queue->backlog.gro_count = 0;
14 }
15
16 "include/linux/netdevice.h"
17 struct softnet_data
18 {
19 struct Qdisc *output_queue;
20 struct sk_buff_head input_pkt_queue;
21 struct list_head poll_list;
22 struct sk_buff *completion_queue;
23
24 struct napi_struct backlog;
25 };
26
27 struct napi_struct {
28 /* 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 */
34 struct list_head poll_list;
35
36 unsigned long state;
37 int weight;
38 int (*poll)(struct napi_struct *, int);
39 #ifdef CONFIG_NETPOLL
40 spinlock_t poll_lock;
41 int poll_owner;
42 #endif
43
44 unsigned int gro_count;
45
46 struct net_device *dev;
47 struct list_head dev_list;
48 struct sk_buff *gro_list;
49 struct sk_buff *skb;
50 };
