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Commit b17075d5 authored by Igor Druzhinin's avatar Igor Druzhinin Committed by David S. Miller
Browse files

xen-netback: fix race condition on XenBus disconnect 



In some cases during XenBus disconnect event handling and subsequent
queue resource release there may be some TX handlers active on
other processors. Use RCU in order to synchronize with them.

Signed-off-by: default avatarIgor Druzhinin <igor.druzhinin@citrix.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e37791ec

drivers/net/xen-netback/interface.c

+17 −9
Original line number Diff line number Diff line
@@ -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)

drivers/net/xen-netback/netback.c

+1 −1
Original line number Diff line number Diff line
@@ -214,7 +214,7 @@ static void xenvif_fatal_tx_err(struct xenvif *vif) 
	netdev_err(vif->dev, "fatal error; disabling device\n");

	vif->disabled = true;

	/* Disable the vif from queue 0's kthread */

	if (vif->queues)

	if (vif->num_queues)

		xenvif_kick_thread(&vif->queues[0]);

}

drivers/net/xen-netback/xenbus.c

+10 −10
Original line number Diff line number Diff line
@@ -495,26 +495,26 @@ static void backend_disconnect(struct backend_info *be) 
	struct xenvif *vif = be->vif;



	if (vif) {

		unsigned int num_queues = vif->num_queues;

		unsigned int queue_index;

		struct xenvif_queue *queues;



		xen_unregister_watchers(vif);

#ifdef CONFIG_DEBUG_FS

		xenvif_debugfs_delif(vif);

#endif /* CONFIG_DEBUG_FS */

		xenvif_disconnect_data(vif);

		for (queue_index = 0;

		     queue_index < vif->num_queues;

		     ++queue_index)

			xenvif_deinit_queue(&vif->queues[queue_index]);



		spin_lock(&vif->lock);

		queues = vif->queues;

		/* At this point some of the handlers may still be active

		 * so we need to have additional synchronization here.

		 */

		vif->num_queues = 0;

		vif->queues = NULL;

		spin_unlock(&vif->lock);

		synchronize_net();



		vfree(queues);

		for (queue_index = 0; queue_index < num_queues; ++queue_index)

			xenvif_deinit_queue(&vif->queues[queue_index]);



		vfree(vif->queues);

		vif->queues = NULL;



		xenvif_disconnect_ctrl(vif);

	}