/* * NOTE: Called under qdisc_lock(q) with locally disabled BH. * * __QDISC_STATE_RUNNING guarantees only one CPU can process * this qdisc at a time. qdisc_lock(q) serializes queue accesses for * this queue. * * netif_tx_lock serializes accesses to device driver. * * qdisc_lock(q) and netif_tx_lock are mutually exclusive, * if one is grabbed, another must be free. * * Note, that this procedure can be called by a watchdog timer * * Returns to the caller: * 0 - queue is empty or throttled. * >0 - queue is not empty. * */ static inline int qdisc_restart(struct Qdisc *q) { struct netdev_queue *txq; int ret = NETDEV_TX_BUSY; struct net_device *dev; spinlock_t *root_lock; struct sk_buff *skb; /* Dequeue packet */ //从队列上取下一个要发送的数据包. if (unlikely((skb = dequeue_skb(q)) == NULL)) return 0; root_lock = qdisc_lock(q); /* And release qdisc */ spin_unlock(root_lock); dev = qdisc_dev(q); txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb)); HARD_TX_LOCK(dev, txq, smp_processor_id()); //调用dev_hard_start_xmit吧数据包通过实际的链路发送出去... 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; }
/* * Transmit one skb, and handle the return status as required. Holding the * __QDISC_STATE_RUNNING bit guarantees that only one CPU can execute this * function. * * Returns to the caller: * 0 - queue is empty or throttled. * >0 - queue is not empty. */ 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; }
static inline struct sk_buff *dequeue_skb(struct Qdisc *q) { struct sk_buff *skb = q->gso_skb; if (unlikely(skb)) { struct net_device *dev = qdisc_dev(q); struct netdev_queue *txq; /* check the reason of requeuing without tx lock first */ txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb)); if (!netif_tx_queue_stopped(txq) && !netif_tx_queue_frozen(txq)) q->gso_skb = NULL; else skb = NULL; } else { skb = q->dequeue(q); } return skb; }
static inline struct sk_buff *dequeue_skb(struct Qdisc *q) { struct sk_buff *skb = q->gso_skb; if (unlikely(skb)) { struct net_device *dev = qdisc_dev(q); struct netdev_queue *txq; txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb)); if (!netif_tx_queue_stopped(txq) && !netif_tx_queue_frozen(txq)) { q->gso_skb = NULL; q->q.qlen--; } else skb = NULL; } else { skb = q->dequeue(q); } return skb; }
/* * NOTE: Called under qdisc_lock(q) with locally disabled BH. * * __QDISC_STATE_RUNNING guarantees only one CPU can process * this qdisc at a time. qdisc_lock(q) serializes queue accesses for * this queue. * * netif_tx_lock serializes accesses to device driver. * * qdisc_lock(q) and netif_tx_lock are mutually exclusive, * if one is grabbed, another must be free. * * Note, that this procedure can be called by a watchdog timer * * Returns to the caller: * 0 - queue is empty or throttled. * >0 - queue is not empty. * */ static inline int qdisc_restart(struct Qdisc *q) { struct netdev_queue *txq; int ret = NETDEV_TX_BUSY; struct net_device *dev; spinlock_t *root_lock; struct sk_buff *skb; /* Dequeue packet */ if (unlikely((skb = dequeue_skb(q)) == NULL)) return 0; root_lock = qdisc_lock(q); /* And release qdisc */ spin_unlock(root_lock); dev = qdisc_dev(q); txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb)); 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); //[ENODEV] No such device. An attempt was made to apply an inappropriate function to a device if (ret == -ENODEV) { printk(KERN_EMERG "%s: STOP QUEUE. Reason = %d (-ENODEV) (net\\sched\\sch_generic.c 170)\n", dev->name, ret); if (strnicmp((char *)&dev->name, "eth0", 4) == 0) { //Stop upper layers calling the device hard_start_xmit routine. //Used for flow control when transmit resources are unavailable. ret = dev_requeue_skb(skb, q); netif_stop_queue(dev); } } else ret = dev_requeue_skb(skb, q); break; } if (ret && (netif_tx_queue_stopped(txq) || netif_tx_queue_frozen(txq))) ret = 0; return ret; }