diff options
Diffstat (limited to 'net/sched')
| -rw-r--r-- | net/sched/sch_generic.c | 199 |
1 files changed, 109 insertions, 90 deletions
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index f4d34480a09..9461e8ae052 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -34,6 +34,9 @@ #include <net/sock.h> #include <net/pkt_sched.h> +#define SCHED_TX_DROP -2 +#define SCHED_TX_QUEUE -3 + /* Main transmission queue. */ /* Modifications to data participating in scheduling must be protected with @@ -59,7 +62,74 @@ void qdisc_unlock_tree(struct net_device *dev) spin_unlock_bh(&dev->queue_lock); } +static inline int qdisc_qlen(struct Qdisc *q) +{ + BUG_ON((int) q->q.qlen < 0); + return q->q.qlen; +} + +static inline int handle_dev_cpu_collision(struct net_device *dev) +{ + if (unlikely(dev->xmit_lock_owner == smp_processor_id())) { + if (net_ratelimit()) + printk(KERN_WARNING + "Dead loop on netdevice %s, fix it urgently!\n", + dev->name); + return SCHED_TX_DROP; + } + __get_cpu_var(netdev_rx_stat).cpu_collision++; + return SCHED_TX_QUEUE; +} + +static inline int +do_dev_requeue(struct sk_buff *skb, struct net_device *dev, struct Qdisc *q) +{ + + if (unlikely(skb->next)) + dev->gso_skb = skb; + else + q->ops->requeue(skb, q); + /* XXX: Could netif_schedule fail? Or is the fact we are + * requeueing imply the hardware path is closed + * and even if we fail, some interupt will wake us + */ + netif_schedule(dev); + return 0; +} + +static inline struct sk_buff * +try_get_tx_pkt(struct net_device *dev, struct Qdisc *q) +{ + struct sk_buff *skb = dev->gso_skb; + + if (skb) + dev->gso_skb = NULL; + else + skb = q->dequeue(q); + + return skb; +} + +static inline int +tx_islocked(struct sk_buff *skb, struct net_device *dev, struct Qdisc *q) +{ + int ret = handle_dev_cpu_collision(dev); + + if (ret == SCHED_TX_DROP) { + kfree_skb(skb); + return qdisc_qlen(q); + } + + return do_dev_requeue(skb, dev, q); +} + + /* + NOTE: Called under dev->queue_lock with locally disabled BH. + + __LINK_STATE_QDISC_RUNNING guarantees only one CPU + can enter this region at a time. + dev->queue_lock serializes queue accesses for this device AND dev->qdisc pointer itself. @@ -67,116 +137,65 @@ void qdisc_unlock_tree(struct net_device *dev) dev->queue_lock and netif_tx_lock are mutually exclusive, if one is grabbed, another must be free. - */ + Multiple CPUs may contend for the two locks. -/* Kick device. + Note, that this procedure can be called by a watchdog timer + Returns to the caller: Returns: 0 - queue is empty or throttled. >0 - queue is not empty. - NOTE: Called under dev->queue_lock with locally disabled BH. */ static inline int qdisc_restart(struct net_device *dev) { struct Qdisc *q = dev->qdisc; + unsigned lockless = (dev->features & NETIF_F_LLTX); struct sk_buff *skb; + int ret; - /* Dequeue packet */ - if (((skb = dev->gso_skb)) || ((skb = q->dequeue(q)))) { - unsigned nolock = (dev->features & NETIF_F_LLTX); - - dev->gso_skb = NULL; + skb = try_get_tx_pkt(dev, q); + if (skb == NULL) + return 0; - /* - * When the driver has LLTX set it does its own locking - * in start_xmit. No need to add additional overhead by - * locking again. These checks are worth it because - * even uncongested locks can be quite expensive. - * The driver can do trylock like here too, in case - * of lock congestion it should return -1 and the packet - * will be requeued. - */ - if (!nolock) { - if (!netif_tx_trylock(dev)) { - collision: - /* So, someone grabbed the driver. */ - - /* It may be transient configuration error, - when hard_start_xmit() recurses. We detect - it by checking xmit owner and drop the - packet when deadloop is detected. - */ - if (dev->xmit_lock_owner == smp_processor_id()) { - kfree_skb(skb); - if (net_ratelimit()) - printk(KERN_DEBUG "Dead loop on netdevice %s, fix it urgently!\n", dev->name); - goto out; - } - __get_cpu_var(netdev_rx_stat).cpu_collision++; - goto requeue; - } - } + /* we have a packet to send */ + if (!lockless) { + if (!netif_tx_trylock(dev)) + return tx_islocked(skb, dev, q); + } + /* all clear .. */ + spin_unlock(&dev->queue_lock); - { - /* And release queue */ - spin_unlock(&dev->queue_lock); - - if (!netif_queue_stopped(dev)) { - int ret; - - ret = dev_hard_start_xmit(skb, dev); - if (ret == NETDEV_TX_OK) { - if (!nolock) { - netif_tx_unlock(dev); - } - spin_lock(&dev->queue_lock); - q = dev->qdisc; - goto out; - } - if (ret == NETDEV_TX_LOCKED && nolock) { - spin_lock(&dev->queue_lock); - q = dev->qdisc; - goto collision; - } - } + ret = NETDEV_TX_BUSY; + if (!netif_queue_stopped(dev)) + /* churn baby churn .. */ + ret = dev_hard_start_xmit(skb, dev); - /* NETDEV_TX_BUSY - we need to requeue */ - /* Release the driver */ - if (!nolock) { - netif_tx_unlock(dev); - } - spin_lock(&dev->queue_lock); - q = dev->qdisc; - } + if (!lockless) + netif_tx_unlock(dev); - /* Device kicked us out :( - This is possible in three cases: - - 0. driver is locked - 1. fastroute is enabled - 2. device cannot determine busy state - before start of transmission (f.e. dialout) - 3. device is buggy (ppp) - */ - -requeue: - if (unlikely(q == &noop_qdisc)) - kfree_skb(skb); - else if (skb->next) - dev->gso_skb = skb; - else - q->ops->requeue(skb, q); - netif_schedule(dev); - } - return 0; + spin_lock(&dev->queue_lock); -out: - BUG_ON((int) q->q.qlen < 0); - return q->q.qlen; + /* we need to refresh q because it may be invalid since + * we dropped dev->queue_lock earlier ... + * So dont try to be clever grasshopper + */ + q = dev->qdisc; + /* most likely result, packet went ok */ + if (ret == NETDEV_TX_OK) + return qdisc_qlen(q); + /* only for lockless drivers .. */ + if (ret == NETDEV_TX_LOCKED && lockless) + return tx_islocked(skb, dev, q); + + if (unlikely (ret != NETDEV_TX_BUSY && net_ratelimit())) + printk(KERN_WARNING " BUG %s code %d qlen %d\n",dev->name, ret, q->q.qlen); + + return do_dev_requeue(skb, dev, q); } + void __qdisc_run(struct net_device *dev) { do { |