1 files changed, 17 insertions, 9 deletions

diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 829b26cd4549..8397f6c92451 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -165,13 +165,17 @@ static int xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
         struct xenvif *vif = netdev_priv(dev);
         struct xenvif_queue *queue = NULL;
-        unsigned int num_queues = vif->num_queues;
+        unsigned int num_queues;
         u16 index;
         struct xenvif_rx_cb *cb;
 
         BUG_ON(skb->dev != dev);
 
-        /* Drop the packet if queues are not set up */
+        /* Drop the packet if queues are not set up.
+         * This handler should be called inside an RCU read section
+         * so we don't need to enter it here explicitly.
+         */
+        num_queues = READ_ONCE(vif->num_queues);
         if (num_queues < 1)
                 goto drop;
 
@@ -222,18 +226,18 @@ static struct net_device_stats *xenvif_get_stats(struct net_device *dev)
 {
         struct xenvif *vif = netdev_priv(dev);
         struct xenvif_queue *queue = NULL;
+        unsigned int num_queues;
         u64 rx_bytes = 0;
         u64 rx_packets = 0;
         u64 tx_bytes = 0;
         u64 tx_packets = 0;
         unsigned int index;
 
-        spin_lock(&vif->lock);
-        if (vif->queues == NULL)
-                goto out;
+        rcu_read_lock();
+        num_queues = READ_ONCE(vif->num_queues);
 
         /* Aggregate tx and rx stats from each queue */
-        for (index = 0; index < vif->num_queues; ++index) {
+        for (index = 0; index < num_queues; ++index) {
                 queue = &vif->queues[index];
                 rx_bytes += queue->stats.rx_bytes;
                 rx_packets += queue->stats.rx_packets;
@@ -241,8 +245,7 @@ static struct net_device_stats *xenvif_get_stats(struct net_device *dev)
                 tx_packets += queue->stats.tx_packets;
         }
 
-out:
-        spin_unlock(&vif->lock);
+        rcu_read_unlock();
 
         vif->dev->stats.rx_bytes = rx_bytes;
         vif->dev->stats.rx_packets = rx_packets;
@@ -378,10 +381,13 @@ static void xenvif_get_ethtool_stats(struct net_device *dev,
                                      struct ethtool_stats *stats, u64 * data)
 {
         struct xenvif *vif = netdev_priv(dev);
-        unsigned int num_queues = vif->num_queues;
+        unsigned int num_queues;
         int i;
         unsigned int queue_index;
 
+        rcu_read_lock();
+        num_queues = READ_ONCE(vif->num_queues);
+
         for (i = 0; i < ARRAY_SIZE(xenvif_stats); i++) {
                 unsigned long accum = 0;
                 for (queue_index = 0; queue_index < num_queues; ++queue_index) {
@@ -390,6 +396,8 @@ static void xenvif_get_ethtool_stats(struct net_device *dev,
                 }
                 data[i] = accum;
         }
+
+        rcu_read_unlock();
 }
 
 static void xenvif_get_strings(struct net_device *dev, u32 stringset, u8 * data)