3 files changed, 61 insertions, 5 deletions

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index f2f8a02afc36..0355f8767e3b 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -148,6 +148,9 @@ struct xenvif {
         struct xen_netif_rx_back_ring rx;
         struct sk_buff_head rx_queue;
         RING_IDX rx_last_skb_slots;
+        bool rx_queue_purge;
+
+        struct timer_list wake_queue;
 
         /* This array is allocated seperately as it is large */
         struct gnttab_copy *grant_copy_op;
@@ -259,4 +262,7 @@ void xenvif_zerocopy_callback(struct ubuf_info *ubuf, bool zerocopy_success);
 
 extern bool separate_tx_rx_irq;
 
+extern unsigned int rx_drain_timeout_msecs;
+extern unsigned int rx_drain_timeout_jiffies;
+
 #endif /* __XEN_NETBACK__COMMON_H__ */
diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index b646039e539b..9cc9f638f442 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -115,6 +115,18 @@ static irqreturn_t xenvif_interrupt(int irq, void *dev_id)
         return IRQ_HANDLED;
 }
 
+static void xenvif_wake_queue(unsigned long data)
+{
+        struct xenvif *vif = (struct xenvif *)data;
+
+        if (netif_queue_stopped(vif->dev)) {
+                netdev_err(vif->dev, "draining TX queue\n");
+                vif->rx_queue_purge = true;
+                xenvif_kick_thread(vif);
+                netif_wake_queue(vif->dev);
+        }
+}
+
 static int xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
         struct xenvif *vif = netdev_priv(dev);
@@ -144,8 +156,13 @@ static int xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev)
          * then turn off the queue to give the ring a chance to
          * drain.
          */
-        if (!xenvif_rx_ring_slots_available(vif, min_slots_needed))
+        if (!xenvif_rx_ring_slots_available(vif, min_slots_needed)) {
+                vif->wake_queue.function = xenvif_wake_queue;
+                vif->wake_queue.data = (unsigned long)vif;
                 xenvif_stop_queue(vif);
+                mod_timer(&vif->wake_queue,
+                        jiffies + rx_drain_timeout_jiffies);
+        }
 
         skb_queue_tail(&vif->rx_queue, skb);
         xenvif_kick_thread(vif);
@@ -353,6 +370,8 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
         init_timer(&vif->credit_timeout);
         vif->credit_window_start = get_jiffies_64();
 
+        init_timer(&vif->wake_queue);
+
         dev->netdev_ops = &xenvif_netdev_ops;
         dev->hw_features = NETIF_F_SG |
                 NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM |
@@ -531,6 +550,7 @@ void xenvif_disconnect(struct xenvif *vif)
                 xenvif_carrier_off(vif);
 
         if (vif->task) {
+                del_timer_sync(&vif->wake_queue);
                 kthread_stop(vif->task);
                 vif->task = NULL;
         }
@@ -556,12 +576,25 @@ void xenvif_disconnect(struct xenvif *vif)
 void xenvif_free(struct xenvif *vif)
 {
         int i, unmap_timeout = 0;
+        /* Here we want to avoid timeout messages if an skb can be legitimatly
+         * stucked somewhere else. Realisticly this could be an another vif's
+         * internal or QDisc queue. That another vif also has this
+         * rx_drain_timeout_msecs timeout, but the timer only ditches the
+         * internal queue. After that, the QDisc queue can put in worst case
+         * XEN_NETIF_RX_RING_SIZE / MAX_SKB_FRAGS skbs into that another vif's
+         * internal queue, so we need several rounds of such timeouts until we
+         * can be sure that no another vif should have skb's from us. We are
+         * not sending more skb's, so newly stucked packets are not interesting
+         * for us here.
+         */
+        unsigned int worst_case_skb_lifetime = (rx_drain_timeout_msecs/1000) *
+                DIV_ROUND_UP(XENVIF_QUEUE_LENGTH, (XEN_NETIF_RX_RING_SIZE / MAX_SKB_FRAGS));
 
         for (i = 0; i < MAX_PENDING_REQS; ++i) {
                 if (vif->grant_tx_handle[i] != NETBACK_INVALID_HANDLE) {
                         unmap_timeout++;
                         schedule_timeout(msecs_to_jiffies(1000));
-                        if (unmap_timeout > 9 &&
+                        if (unmap_timeout > worst_case_skb_lifetime &&
                             net_ratelimit())
                                 netdev_err(vif->dev,
                                            "Page still granted! Index: %x\n",
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 58effc49f526..8518a0d1f6f9 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -55,6 +55,13 @@
 bool separate_tx_rx_irq = 1;
 module_param(separate_tx_rx_irq, bool, 0644);
 
+/* When guest ring is filled up, qdisc queues the packets for us, but we have
+ * to timeout them, otherwise other guests' packets can get stucked there
+ */
+unsigned int rx_drain_timeout_msecs = 10000;
+module_param(rx_drain_timeout_msecs, uint, 0444);
+unsigned int rx_drain_timeout_jiffies;
+
 /*
  * This is the maximum slots a skb can have. If a guest sends a skb
  * which exceeds this limit it is considered malicious.
@@ -1694,8 +1701,9 @@ void xenvif_idx_unmap(struct xenvif *vif, u16 pending_idx)
 
 static inline int rx_work_todo(struct xenvif *vif)
 {
-        return !skb_queue_empty(&vif->rx_queue) &&
-               xenvif_rx_ring_slots_available(vif, vif->rx_last_skb_slots);
+        return (!skb_queue_empty(&vif->rx_queue) &&
+               xenvif_rx_ring_slots_available(vif, vif->rx_last_skb_slots)) ||
+               vif->rx_queue_purge;
 }
 
 static inline int tx_work_todo(struct xenvif *vif)
@@ -1782,12 +1790,19 @@ int xenvif_kthread_guest_rx(void *data)
                 if (kthread_should_stop())
                         break;
 
+                if (vif->rx_queue_purge) {
+                        skb_queue_purge(&vif->rx_queue);
+                        vif->rx_queue_purge = false;
+                }
+
                 if (!skb_queue_empty(&vif->rx_queue))
                         xenvif_rx_action(vif);
 
                 if (skb_queue_empty(&vif->rx_queue) &&
-                    netif_queue_stopped(vif->dev))
+                    netif_queue_stopped(vif->dev)) {
+                        del_timer_sync(&vif->wake_queue);
                         xenvif_start_queue(vif);
+                }
 
                 cond_resched();
         }
@@ -1838,6 +1853,8 @@ static int __init netback_init(void)
         if (rc)
                 goto failed_init;
 
+        rx_drain_timeout_jiffies = msecs_to_jiffies(rx_drain_timeout_msecs);
+
         return 0;
 
 failed_init: