net_dev_init中通過open_softirq(NET_RX_SOFTIRQ, net_rx_action);注冊(cè)了軟中斷處理函數(shù)，napi調(diào)度中激發(fā)了軟中斷調(diào)用net_rx_action：
static void net_rx_action(struct softirq_action *h)
{
struct list_head *list = &__get_cpu_var(softnet_data).poll_list;
unsigned long start_time = jiffies;
int budget = netdev_budget;
void *have;
local_irq_disable();
while (!list_empty(list)) {
struct napi_struct *n;
int work, weight;
/* If softirq window is exhuasted then punt.
*
* Note that this is a slight policy change from the
* previous NAPI code, which would allow up to 2
* jiffies to pass before breaking out. The test
* used to be "jiffies - start_time > 1".
*/
if (unlikely(budget <= 0 || jiffies != start_time))
goto softnet_break;
local_irq_enable();
/* Even though interrupts have been re-enabled, this
* access is safe because interrupts can only add new
* entries to the tail of this list, and only ->poll()
* calls can remove this head entry from the list.
*/
n = list_entry(list->next, struct napi_struct, poll_list);
have = netpoll_poll_lock(n);
//weight 每次輪詢最大數(shù)量
weight = n->weight;
/* This NAPI_STATE_SCHED test is for avoiding a race
* with netpoll's poll_napi(). Only the entity which
* obtains the lock and sees NAPI_STATE_SCHED set will
* actually make the ->poll() call. Therefore we avoid
* accidently calling ->poll() when NAPI is not scheduled.
*/
work = 0;
if (test_bit(NAPI_STATE_SCHED, &n->state)) //napi的狀態(tài)是否為NAPI_STATE_SCHED
work = n->poll(n, weight); //執(zhí)行輪詢,，輪詢函數(shù)初始化是在net_dev_init中：
//queue->backlog.poll = process_backlog;（默認(rèn)）
WARN_ON_ONCE(work > weight);
budget -= work;
local_irq_disable();
/* Drivers must not modify the NAPI state if they
* consume the entire weight. In such cases this code
* still "owns" the NAPI instance and therefore can
* move the instance around on the list at-will.
*/
if (unlikely(work == weight)) {
if (unlikely(napi_disable_pending(n)))
__napi_complete(n);
else
list_move_tail(&n->poll_list, list);
}
netpoll_poll_unlock(have);
}
out:
local_irq_enable();
,。。,。,。。,。,。。,。,。。,。,。,。,。。,。,。。,。,。。,。,。。,。,。。,。,。。,。,。。,。,。。。,。,。。,。,。。,。,。。,。
}
static int process_backlog(struct napi_struct *napi, int quota)
{
int work = 0;
struct softnet_data *queue = &__get_cpu_var(softnet_data);
unsigned long start_time = jiffies;
napi->weight = weight_p;
do {
struct sk_buff *skb;
local_irq_disable();
skb = __skb_dequeue(&queue->input_pkt_queue);
if (!skb) {
__napi_complete(napi); //從poll隊(duì)列中刪除napi
local_irq_enable();
break;
}
local_irq_enable();
netif_receive_skb(skb);
} while (++work < quota && jiffies == start_time);
return work;
}
在netif_receive_skb中,，會(huì)輪詢ptype_all list找到與packet_bind中協(xié)議類型相符的packet_type，然后通過deliver_skb調(diào)用packet type所注冊(cè)的接收處理函數(shù),。
static inline int deliver_skb(struct sk_buff *skb,
struct packet_type *pt_prev,
struct net_device *orig_dev)
{
atomic_inc(&skb->users);
return pt_prev->func(skb, skb->dev, pt_prev, orig_dev); //packet_create時(shí)初始化func指向packet_rcv
}
