netdev: Fix lockdep warnings in multiqueue configurations.

When support for multiple TX queues were added, the
netif_tx_lock() routines we converted to iterate over
all TX queues and grab each queue's spinlock.

This causes heartburn for lockdep and it's not a healthy
thing to do with lots of TX queues anyways.

So modify this to use a top-level lock and a "frozen"
state for the individual TX queues.

Signed-off-by: David S. Miller <davem@davemloft.net>

7 files changed, 78 insertions, 44 deletions

diff --git a/drivers/net/ifb.c b/drivers/net/ifb.c
index 0960e69b2da4..e4fbefc8c82f 100644
--- a/drivers/net/ifb.c
+++ b/drivers/net/ifb.c
@@ -69,18 +69,20 @@ static void ri_tasklet(unsigned long dev)
         struct net_device *_dev = (struct net_device *)dev;
         struct ifb_private *dp = netdev_priv(_dev);
         struct net_device_stats *stats = &_dev->stats;
+        struct netdev_queue *txq;
         struct sk_buff *skb;
 
+        txq = netdev_get_tx_queue(_dev, 0);
         dp->st_task_enter++;
         if ((skb = skb_peek(&dp->tq)) == NULL) {
                 dp->st_txq_refl_try++;
-                if (netif_tx_trylock(_dev)) {
+                if (__netif_tx_trylock(txq)) {
                         dp->st_rxq_enter++;
                         while ((skb = skb_dequeue(&dp->rq)) != NULL) {
                                 skb_queue_tail(&dp->tq, skb);
                                 dp->st_rx2tx_tran++;
                         }
-                        netif_tx_unlock(_dev);
+                        __netif_tx_unlock(txq);
                 } else {
                         /* reschedule */
                         dp->st_rxq_notenter++;
@@ -115,7 +117,7 @@ static void ri_tasklet(unsigned long dev)
                         BUG();
         }
 
-        if (netif_tx_trylock(_dev)) {
+        if (__netif_tx_trylock(txq)) {
                 dp->st_rxq_check++;
                 if ((skb = skb_peek(&dp->rq)) == NULL) {
                         dp->tasklet_pending = 0;
@@ -123,10 +125,10 @@ static void ri_tasklet(unsigned long dev)
                                 netif_wake_queue(_dev);
                 } else {
                         dp->st_rxq_rsch++;
-                        netif_tx_unlock(_dev);
+                        __netif_tx_unlock(txq);
                         goto resched;
                 }
-                netif_tx_unlock(_dev);
+                __netif_tx_unlock(txq);
         } else {
 resched:
                 dp->tasklet_pending = 1;
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index b4d056ceab96..ee583f642a9f 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -440,6 +440,7 @@ static inline void napi_synchronize(const struct napi_struct *n)
 enum netdev_queue_state_t
 {
         __QUEUE_STATE_XOFF,
+        __QUEUE_STATE_FROZEN,
 };
 
 struct netdev_queue {
@@ -636,7 +637,7 @@ struct net_device
         unsigned int            real_num_tx_queues;
 
         unsigned long           tx_queue_len;   /* Max frames per queue allowed */
-
+        spinlock_t              tx_global_lock;
 /*
  * One part is mostly used on xmit path (device)
  */
@@ -1099,6 +1100,11 @@ static inline int netif_queue_stopped(const struct net_device *dev)
         return netif_tx_queue_stopped(netdev_get_tx_queue(dev, 0));
 }
 
+static inline int netif_tx_queue_frozen(const struct netdev_queue *dev_queue)
+{
+        return test_bit(__QUEUE_STATE_FROZEN, &dev_queue->state);
+}
+
 /**
  *      netif_running - test if up
  *      @dev: network device
@@ -1475,6 +1481,26 @@ static inline void __netif_tx_lock_bh(struct netdev_queue *txq)
         txq->xmit_lock_owner = smp_processor_id();
 }
 
+static inline int __netif_tx_trylock(struct netdev_queue *txq)
+{
+        int ok = spin_trylock(&txq->_xmit_lock);
+        if (likely(ok))
+                txq->xmit_lock_owner = smp_processor_id();
+        return ok;
+}
+
+static inline void __netif_tx_unlock(struct netdev_queue *txq)
+{
+        txq->xmit_lock_owner = -1;
+        spin_unlock(&txq->_xmit_lock);
+}
+
+static inline void __netif_tx_unlock_bh(struct netdev_queue *txq)
+{
+        txq->xmit_lock_owner = -1;
+        spin_unlock_bh(&txq->_xmit_lock);
+}
+
 /**
  *      netif_tx_lock - grab network device transmit lock
  *      @dev: network device
@@ -1484,12 +1510,23 @@ static inline void __netif_tx_lock_bh(struct netdev_queue *txq)
  */
 static inline void netif_tx_lock(struct net_device *dev)
 {
-        int cpu = smp_processor_id();
         unsigned int i;
+        int cpu;
 
+        spin_lock(&dev->tx_global_lock);
+        cpu = smp_processor_id();
         for (i = 0; i < dev->num_tx_queues; i++) {
                 struct netdev_queue *txq = netdev_get_tx_queue(dev, i);
+
+                /* We are the only thread of execution doing a
+                 * freeze, but we have to grab the _xmit_lock in
+                 * order to synchronize with threads which are in
+                 * the ->hard_start_xmit() handler and already
+                 * checked the frozen bit.
+                 */
                 __netif_tx_lock(txq, cpu);
+                set_bit(__QUEUE_STATE_FROZEN, &txq->state);
+                __netif_tx_unlock(txq);
         }
 }
 
@@ -1499,40 +1536,22 @@ static inline void netif_tx_lock_bh(struct net_device *dev)
         netif_tx_lock(dev);
 }
 
-static inline int __netif_tx_trylock(struct netdev_queue *txq)
-{
-        int ok = spin_trylock(&txq->_xmit_lock);
-        if (likely(ok))
-                txq->xmit_lock_owner = smp_processor_id();
-        return ok;
-}
-
-static inline int netif_tx_trylock(struct net_device *dev)
-{
-        return __netif_tx_trylock(netdev_get_tx_queue(dev, 0));
-}
-
-static inline void __netif_tx_unlock(struct netdev_queue *txq)
-{
-        txq->xmit_lock_owner = -1;
-        spin_unlock(&txq->_xmit_lock);
-}
-
-static inline void __netif_tx_unlock_bh(struct netdev_queue *txq)
-{
-        txq->xmit_lock_owner = -1;
-        spin_unlock_bh(&txq->_xmit_lock);
-}
-
 static inline void netif_tx_unlock(struct net_device *dev)
 {
         unsigned int i;
 
         for (i = 0; i < dev->num_tx_queues; i++) {
                 struct netdev_queue *txq = netdev_get_tx_queue(dev, i);
-                __netif_tx_unlock(txq);
-        }
 
+                /* No need to grab the _xmit_lock here.  If the
+                 * queue is not stopped for another reason, we
+                 * force a schedule.
+                 */
+                clear_bit(__QUEUE_STATE_FROZEN, &txq->state);
+                if (!test_bit(__QUEUE_STATE_XOFF, &txq->state))
+                        __netif_schedule(txq->qdisc);
+        }
+        spin_unlock(&dev->tx_global_lock);
 }
 
 static inline void netif_tx_unlock_bh(struct net_device *dev)
@@ -1556,13 +1575,18 @@ static inline void netif_tx_unlock_bh(struct net_device *dev)
 static inline void netif_tx_disable(struct net_device *dev)
 {
         unsigned int i;
+        int cpu;
 
-        netif_tx_lock_bh(dev);
+        local_bh_disable();
+        cpu = smp_processor_id();
         for (i = 0; i < dev->num_tx_queues; i++) {
                 struct netdev_queue *txq = netdev_get_tx_queue(dev, i);
+
+                __netif_tx_lock(txq, cpu);
                 netif_tx_stop_queue(txq);
+                __netif_tx_unlock(txq);
         }
-        netif_tx_unlock_bh(dev);
+        local_bh_enable();
 }
 
 static inline void netif_addr_lock(struct net_device *dev)
diff --git a/net/core/dev.c b/net/core/dev.c
index 63d6bcddbf46..69320a56a084 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4200,6 +4200,7 @@ static void netdev_init_queues(struct net_device *dev)
 {
         netdev_init_one_queue(dev, &dev->rx_queue, NULL);
         netdev_for_each_tx_queue(dev, netdev_init_one_queue, NULL);
+        spin_lock_init(&dev->tx_global_lock);
 }
 
 /**
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index c12720895ecf..6c7af390be0a 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -70,6 +70,7 @@ static void queue_process(struct work_struct *work)
                 local_irq_save(flags);
                 __netif_tx_lock(txq, smp_processor_id());
                 if (netif_tx_queue_stopped(txq) ||
+                    netif_tx_queue_frozen(txq) ||
                     dev->hard_start_xmit(skb, dev) != NETDEV_TX_OK) {
                         skb_queue_head(&npinfo->txq, skb);
                         __netif_tx_unlock(txq);
diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index c7d484f7e1c4..3284605f2ec7 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -3305,6 +3305,7 @@ static __inline__ void pktgen_xmit(struct pktgen_dev *pkt_dev)
 
         txq = netdev_get_tx_queue(odev, queue_map);
         if (netif_tx_queue_stopped(txq) ||
+            netif_tx_queue_frozen(txq) ||
             need_resched()) {
                 idle_start = getCurUs();
 
@@ -3320,7 +3321,8 @@ static __inline__ void pktgen_xmit(struct pktgen_dev *pkt_dev)
 
                 pkt_dev->idle_acc += getCurUs() - idle_start;
 
-                if (netif_tx_queue_stopped(txq)) {
+                if (netif_tx_queue_stopped(txq) ||
+                    netif_tx_queue_frozen(txq)) {
                         pkt_dev->next_tx_us = getCurUs();       /* TODO */
                         pkt_dev->next_tx_ns = 0;
                         goto out;       /* Try the next interface */
@@ -3352,7 +3354,8 @@ static __inline__ void pktgen_xmit(struct pktgen_dev *pkt_dev)
         txq = netdev_get_tx_queue(odev, queue_map);
 
         __netif_tx_lock_bh(txq);
-        if (!netif_tx_queue_stopped(txq)) {
+        if (!netif_tx_queue_stopped(txq) &&
+            !netif_tx_queue_frozen(txq)) {
 
                 atomic_inc(&(pkt_dev->skb->users));
               retry_now:
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 345838a2e369..9c9cd4d94890 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -135,7 +135,8 @@ static inline int qdisc_restart(struct Qdisc *q)
         txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));
 
         HARD_TX_LOCK(dev, txq, smp_processor_id());
-        if (!netif_subqueue_stopped(dev, skb))
+        if (!netif_tx_queue_stopped(txq) &&
+            !netif_tx_queue_frozen(txq))
                 ret = dev_hard_start_xmit(skb, dev, txq);
         HARD_TX_UNLOCK(dev, txq);
 
@@ -162,7 +163,8 @@ static inline int qdisc_restart(struct Qdisc *q)
                 break;
         }
 
-        if (ret && netif_tx_queue_stopped(txq))
+        if (ret && (netif_tx_queue_stopped(txq) ||
+                    netif_tx_queue_frozen(txq)))
                 ret = 0;
 
         return ret;
diff --git a/net/sched/sch_teql.c b/net/sched/sch_teql.c
index 537223642b6e..2c35c678563b 100644
--- a/net/sched/sch_teql.c
+++ b/net/sched/sch_teql.c
@@ -305,10 +305,11 @@ restart:
 
                 switch (teql_resolve(skb, skb_res, slave)) {
                 case 0:
-                        if (netif_tx_trylock(slave)) {
-                                if (!__netif_subqueue_stopped(slave, subq) &&
+                        if (__netif_tx_trylock(slave_txq)) {
+                                if (!netif_tx_queue_stopped(slave_txq) &&
+                                    !netif_tx_queue_frozen(slave_txq) &&
                                     slave->hard_start_xmit(skb, slave) == 0) {
-                                        netif_tx_unlock(slave);
+                                        __netif_tx_unlock(slave_txq);
                                         master->slaves = NEXT_SLAVE(q);
                                         netif_wake_queue(dev);
                                         master->stats.tx_packets++;
@@ -316,7 +317,7 @@ restart:
                                                 qdisc_pkt_len(skb);
                                         return 0;
                                 }
-                                netif_tx_unlock(slave);
+                                __netif_tx_unlock(slave_txq);
                         }
                         if (netif_queue_stopped(dev))
                                 busy = 1;