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>
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index b4d056c..ee583f6 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -440,6 +440,7 @@
enum netdev_queue_state_t
{
__QUEUE_STATE_XOFF,
+ __QUEUE_STATE_FROZEN,
};
struct netdev_queue {
@@ -636,7 +637,7 @@
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 @@
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
@@ -1475,30 +1481,6 @@
txq->xmit_lock_owner = smp_processor_id();
}
-/**
- * netif_tx_lock - grab network device transmit lock
- * @dev: network device
- * @cpu: cpu number of lock owner
- *
- * Get network device transmit lock
- */
-static inline void netif_tx_lock(struct net_device *dev)
-{
- int cpu = smp_processor_id();
- unsigned int i;
-
- for (i = 0; i < dev->num_tx_queues; i++) {
- struct netdev_queue *txq = netdev_get_tx_queue(dev, i);
- __netif_tx_lock(txq, cpu);
- }
-}
-
-static inline void netif_tx_lock_bh(struct net_device *dev)
-{
- local_bh_disable();
- netif_tx_lock(dev);
-}
-
static inline int __netif_tx_trylock(struct netdev_queue *txq)
{
int ok = spin_trylock(&txq->_xmit_lock);
@@ -1507,11 +1489,6 @@
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;
@@ -1524,15 +1501,57 @@
spin_unlock_bh(&txq->_xmit_lock);
}
+/**
+ * netif_tx_lock - grab network device transmit lock
+ * @dev: network device
+ * @cpu: cpu number of lock owner
+ *
+ * Get network device transmit lock
+ */
+static inline void netif_tx_lock(struct net_device *dev)
+{
+ 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);
+ }
+}
+
+static inline void netif_tx_lock_bh(struct net_device *dev)
+{
+ local_bh_disable();
+ netif_tx_lock(dev);
+}
+
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_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)