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Diffstat (limited to 'net/sched')
-rw-r--r--net/sched/sch_generic.c167
1 files changed, 86 insertions, 81 deletions
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 9461e8a..983c32c 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -34,9 +34,6 @@
#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
@@ -68,41 +65,24 @@ static inline int qdisc_qlen(struct Qdisc *q)
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)
+static inline int dev_requeue_skb(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)
+static inline struct sk_buff *dev_dequeue_skb(struct net_device *dev,
+ struct Qdisc *q)
{
- struct sk_buff *skb = dev->gso_skb;
+ struct sk_buff *skb;
- if (skb)
+ if ((skb = dev->gso_skb))
dev->gso_skb = NULL;
else
skb = q->dequeue(q);
@@ -110,92 +90,117 @@ try_get_tx_pkt(struct net_device *dev, struct Qdisc *q)
return skb;
}
-static inline int
-tx_islocked(struct sk_buff *skb, struct net_device *dev, struct Qdisc *q)
+static inline int handle_dev_cpu_collision(struct sk_buff *skb,
+ struct net_device *dev,
+ struct Qdisc *q)
{
- int ret = handle_dev_cpu_collision(dev);
+ int ret;
- if (ret == SCHED_TX_DROP) {
+ if (unlikely(dev->xmit_lock_owner == smp_processor_id())) {
+ /*
+ * Same CPU holding the lock. It may be a transient
+ * configuration error, when hard_start_xmit() recurses. We
+ * detect it by checking xmit owner and drop the packet when
+ * deadloop is detected. Return OK to try the next skb.
+ */
kfree_skb(skb);
- return qdisc_qlen(q);
+ if (net_ratelimit())
+ printk(KERN_WARNING "Dead loop on netdevice %s, "
+ "fix it urgently!\n", dev->name);
+ ret = qdisc_qlen(q);
+ } else {
+ /*
+ * Another cpu is holding lock, requeue & delay xmits for
+ * some time.
+ */
+ __get_cpu_var(netdev_rx_stat).cpu_collision++;
+ ret = dev_requeue_skb(skb, dev, q);
}
- return do_dev_requeue(skb, dev, q);
+ return ret;
}
-
/*
- 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.
-
- netif_tx_lock serializes accesses to device driver.
-
- 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.
-
- 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.
+ *
+ * __LINK_STATE_QDISC_RUNNING guarantees only one CPU can process this
+ * device at a time. dev->queue_lock serializes queue accesses for
+ * this device AND dev->qdisc pointer itself.
+ *
+ * netif_tx_lock serializes accesses to device driver.
+ *
+ * dev->queue_lock 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 net_device *dev)
{
struct Qdisc *q = dev->qdisc;
- unsigned lockless = (dev->features & NETIF_F_LLTX);
struct sk_buff *skb;
+ unsigned lockless;
int ret;
- skb = try_get_tx_pkt(dev, q);
- if (skb == NULL)
+ /* Dequeue packet */
+ if (unlikely((skb = dev_dequeue_skb(dev, q)) == NULL))
return 0;
- /* we have a packet to send */
- if (!lockless) {
- if (!netif_tx_trylock(dev))
- return tx_islocked(skb, dev, q);
+ /*
+ * When the driver has LLTX set, it does its own locking in
+ * start_xmit. These checks are worth it because even uncongested
+ * locks can be quite expensive. The driver can do a trylock, as
+ * is being done here; in case of lock contention it should return
+ * NETDEV_TX_LOCKED and the packet will be requeued.
+ */
+ lockless = (dev->features & NETIF_F_LLTX);
+
+ if (!lockless && !netif_tx_trylock(dev)) {
+ /* Another CPU grabbed the driver tx lock */
+ return handle_dev_cpu_collision(skb, dev, q);
}
- /* all clear .. */
+
+ /* And release queue */
spin_unlock(&dev->queue_lock);
ret = NETDEV_TX_BUSY;
if (!netif_queue_stopped(dev))
- /* churn baby churn .. */
ret = dev_hard_start_xmit(skb, dev);
if (!lockless)
netif_tx_unlock(dev);
spin_lock(&dev->queue_lock);
-
- /* 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);
+ 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, dev, 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, dev, q);
+ break;
+ }
- return do_dev_requeue(skb, dev, q);
+ return ret;
}
-
void __qdisc_run(struct net_device *dev)
{
do {
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