数据收发的软中断以及数据从网卡发送

注册软中断

static int __init net_dev_init(void){         ......        open_softirq(NET_TX_SOFTIRQ, net_tx_action);open_softirq(NET_RX_SOFTIRQ, net_rx_action);      ......}static void net_tx_action(struct softirq_action *h){struct softnet_data *sd = &__get_cpu_var(softnet_data);if (sd->completion_queue) {struct sk_buff *clist;local_irq_disable();clist = sd->completion_queue;sd->completion_queue = NULL;local_irq_enable();while (clist) {struct sk_buff *skb = clist;clist = clist->next;WARN_ON(atomic_read(&skb->users));__kfree_skb(skb);}}if (sd->output_queue) {struct Qdisc *head;local_irq_disable();head = sd->output_queue;sd->output_queue = NULL;local_irq_enable();                      //这里不是发送某个网卡的某个包,而是针对所有流控对象Qdisc的调度,逻辑上与网卡没有直接关系while (head) { struct Qdisc *q = head;spinlock_t *root_lock;head = head->next_sched;root_lock = qdisc_lock(q);if (spin_trylock(root_lock)) {smp_mb__before_clear_bit();clear_bit(__QDISC_STATE_SCHED,  &q->state);qdisc_run(q);spin_unlock(root_lock);} else {if (!test_bit(__QDISC_STATE_DEACTIVATED,      &q->state)) {__netif_reschedule(q);} else {smp_mb__before_clear_bit();clear_bit(__QDISC_STATE_SCHED,  &q->state);}}}}}static inline int qdisc_restart(struct Qdisc *q){struct netdev_queue *txq;struct net_device *dev;spinlock_t *root_lock;struct sk_buff *skb;/* Dequeue packet */skb = dequeue_skb(q);if (unlikely(!skb))return 0;root_lock = qdisc_lock(q);dev = qdisc_dev(q);txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));return sch_direct_xmit(skb, q, dev, txq, root_lock);}调用dev_hard_start_xmit将数据包发送出去int sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,struct net_device *dev, struct netdev_queue *txq,spinlock_t *root_lock){int ret = NETDEV_TX_BUSY;/* And release qdisc */spin_unlock(root_lock);HARD_TX_LOCK(dev, txq, smp_processor_id());if (!netif_tx_queue_stopped(txq) &&  !netif_tx_queue_frozen(txq))ret = dev_hard_start_xmit(skb, dev, txq);HARD_TX_UNLOCK(dev, txq);spin_lock(root_lock);switch (ret) {case NETDEV_TX_OK:/* Driver sent out skb successfully */ret = qdisc_qlen(q);break;case NETDEV_TX_LOCKED:/* Driver try lock failed */ret = handle_dev_cpu_collision(skb, txq, q);break;default:/* Driver returned NETDEV_TX_BUSY - requeue skb */if (unlikely (ret != NETDEV_TX_BUSY && net_ratelimit()))printk(KERN_WARNING "BUG %s code %d qlen %d\n",       dev->name, ret, q->q.qlen);ret = dev_requeue_skb(skb, q);break;}if (ret && (netif_tx_queue_stopped(txq) ||netif_tx_queue_frozen(txq)))ret = 0;return ret;}int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,struct netdev_queue *txq){const struct net_device_ops *ops = dev->netdev_ops;int rc;if (likely(!skb->next))         {if (!list_empty(&ptype_all))dev_queue_xmit_nit(skb, dev);if (netif_needs_gso(dev, skb)) {if (unlikely(dev_gso_segment(skb)))goto out_kfree_skb;if (skb->next)goto gso;}if (dev->priv_flags & IFF_XMIT_DST_RELEASE)skb_dst_drop(skb);rc = ops->ndo_start_xmit(skb, dev);if (rc == NETDEV_TX_OK)txq_trans_update(txq);return rc;}gso:      rc = ops->ndo_start_xmit(skb, dev); }

ndo_start_xmit调用驱动的发送方法将包发出