Merge branch 'xen-netfront'

David Vrabel says:

====================
xen-netfront: multi-queue related locking fixes

Two fixes to the per-queue locking bugs in xen-netfront that were
introduced in 3.16-rc1 with the multi-queue support.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/xen-netfront.c

@@ -1439,16 +1439,11 @@ static void xennet_disconnect_backend(struct netfront_info *info)
 	unsigned int i = 0;
 	unsigned int num_queues = info->netdev->real_num_tx_queues;
 
+	netif_carrier_off(info->netdev);
+
 	for (i = 0; i < num_queues; ++i) {
 		struct netfront_queue *queue = &info->queues[i];
 
-		/* Stop old i/f to prevent errors whilst we rebuild the state. */
-		spin_lock_bh(&queue->rx_lock);
-		spin_lock_irq(&queue->tx_lock);
-		netif_carrier_off(queue->info->netdev);
-		spin_unlock_irq(&queue->tx_lock);
-		spin_unlock_bh(&queue->rx_lock);
-
 		if (queue->tx_irq && (queue->tx_irq == queue->rx_irq))
 			unbind_from_irqhandler(queue->tx_irq, queue);
 		if (queue->tx_irq && (queue->tx_irq != queue->rx_irq)) {
@@ -1458,6 +1453,8 @@ static void xennet_disconnect_backend(struct netfront_info *info)
 		queue->tx_evtchn = queue->rx_evtchn = 0;
 		queue->tx_irq = queue->rx_irq = 0;
 
+		napi_synchronize(&queue->napi);
+
 		/* End access and free the pages */
 		xennet_end_access(queue->tx_ring_ref, queue->tx.sring);
 		xennet_end_access(queue->rx_ring_ref, queue->rx.sring);
@@ -2046,13 +2043,15 @@ static int xennet_connect(struct net_device *dev)
 	/* By now, the queue structures have been set up */
 	for (j = 0; j < num_queues; ++j) {
 		queue = &np->queues[j];
-		spin_lock_bh(&queue->rx_lock);
-		spin_lock_irq(&queue->tx_lock);
 
 		/* Step 1: Discard all pending TX packet fragments. */
+		spin_lock_irq(&queue->tx_lock);
 		xennet_release_tx_bufs(queue);
+		spin_unlock_irq(&queue->tx_lock);
 
 		/* Step 2: Rebuild the RX buffer freelist and the RX ring itself. */
+		spin_lock_bh(&queue->rx_lock);
+
 		for (requeue_idx = 0, i = 0; i < NET_RX_RING_SIZE; i++) {
 			skb_frag_t *frag;
 			const struct page *page;
@@ -2076,6 +2075,8 @@ static int xennet_connect(struct net_device *dev)
 		}
 
 		queue->rx.req_prod_pvt = requeue_idx;
+
+		spin_unlock_bh(&queue->rx_lock);
 	}
 
 	/*
@@ -2087,13 +2088,17 @@ static int xennet_connect(struct net_device *dev)
 	netif_carrier_on(np->netdev);
 	for (j = 0; j < num_queues; ++j) {
 		queue = &np->queues[j];
+
 		notify_remote_via_irq(queue->tx_irq);
 		if (queue->tx_irq != queue->rx_irq)
 			notify_remote_via_irq(queue->rx_irq);
-		xennet_tx_buf_gc(queue);
-		xennet_alloc_rx_buffers(queue);
 
+		spin_lock_irq(&queue->tx_lock);
+		xennet_tx_buf_gc(queue);
 		spin_unlock_irq(&queue->tx_lock);
+
+		spin_lock_bh(&queue->rx_lock);
+		xennet_alloc_rx_buffers(queue);
 		spin_unlock_bh(&queue->rx_lock);
 	}