3 files changed, 42 insertions, 7 deletions

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index ef3026f46a37..d4eb8d2e9cb7 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -165,6 +165,7 @@ struct xenvif_queue { /* Per-queue data for xenvif */
         u16 dealloc_ring[MAX_PENDING_REQS];
         struct task_struct *dealloc_task;
         wait_queue_head_t dealloc_wq;
+        atomic_t inflight_packets;
 
         /* Use kthread for guest RX */
         struct task_struct *task;
@@ -329,4 +330,8 @@ extern unsigned int xenvif_max_queues;
 extern struct dentry *xen_netback_dbg_root;
 #endif
 
+void xenvif_skb_zerocopy_prepare(struct xenvif_queue *queue,
+                                 struct sk_buff *skb);
+void xenvif_skb_zerocopy_complete(struct xenvif_queue *queue);
+
 #endif /* __XEN_NETBACK__COMMON_H__ */
diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 5f3d6c06fcf7..0aaca902699a 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -43,6 +43,23 @@
 #define XENVIF_QUEUE_LENGTH 32
 #define XENVIF_NAPI_WEIGHT  64
 
+/* This function is used to set SKBTX_DEV_ZEROCOPY as well as
+ * increasing the inflight counter. We need to increase the inflight
+ * counter because core driver calls into xenvif_zerocopy_callback
+ * which calls xenvif_skb_zerocopy_complete.
+ */
+void xenvif_skb_zerocopy_prepare(struct xenvif_queue *queue,
+                                 struct sk_buff *skb)
+{
+        skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
+        atomic_inc(&queue->inflight_packets);
+}
+
+void xenvif_skb_zerocopy_complete(struct xenvif_queue *queue)
+{
+        atomic_dec(&queue->inflight_packets);
+}
+
 static inline void xenvif_stop_queue(struct xenvif_queue *queue)
 {
         struct net_device *dev = queue->vif->dev;
@@ -557,6 +574,7 @@ int xenvif_connect(struct xenvif_queue *queue, unsigned long tx_ring_ref,
 
         init_waitqueue_head(&queue->wq);
         init_waitqueue_head(&queue->dealloc_wq);
+        atomic_set(&queue->inflight_packets, 0);
 
         if (tx_evtchn == rx_evtchn) {
                 /* feature-split-event-channels == 0 */
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 4734472aa620..08f65996534c 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -1525,10 +1525,12 @@ static int xenvif_handle_frag_list(struct xenvif_queue *queue, struct sk_buff *s
         /* remove traces of mapped pages and frag_list */
         skb_frag_list_init(skb);
         uarg = skb_shinfo(skb)->destructor_arg;
+        /* increase inflight counter to offset decrement in callback */
+        atomic_inc(&queue->inflight_packets);
         uarg->callback(uarg, true);
         skb_shinfo(skb)->destructor_arg = NULL;
 
-        skb_shinfo(nskb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
+        xenvif_skb_zerocopy_prepare(queue, nskb);
         kfree_skb(nskb);
 
         return 0;
@@ -1589,7 +1591,7 @@ static int xenvif_tx_submit(struct xenvif_queue *queue)
                                 if (net_ratelimit())
                                         netdev_err(queue->vif->dev,
                                                    "Not enough memory to consolidate frag_list!\n");
-                                skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
+                                xenvif_skb_zerocopy_prepare(queue, skb);
                                 kfree_skb(skb);
                                 continue;
                         }
@@ -1609,7 +1611,7 @@ static int xenvif_tx_submit(struct xenvif_queue *queue)
                                    "Can't setup checksum in net_tx_action\n");
                         /* We have to set this flag to trigger the callback */
                         if (skb_shinfo(skb)->destructor_arg)
-                                skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
+                                xenvif_skb_zerocopy_prepare(queue, skb);
                         kfree_skb(skb);
                         continue;
                 }
@@ -1641,7 +1643,7 @@ static int xenvif_tx_submit(struct xenvif_queue *queue)
                  * skb. E.g. the __pskb_pull_tail earlier can do such thing.
                  */
                 if (skb_shinfo(skb)->destructor_arg) {
-                        skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
+                        xenvif_skb_zerocopy_prepare(queue, skb);
                         queue->stats.tx_zerocopy_sent++;
                 }
 
@@ -1681,6 +1683,7 @@ void xenvif_zerocopy_callback(struct ubuf_info *ubuf, bool zerocopy_success)
                 queue->stats.tx_zerocopy_success++;
         else
                 queue->stats.tx_zerocopy_fail++;
+        xenvif_skb_zerocopy_complete(queue);
 }
 
 static inline void xenvif_tx_dealloc_action(struct xenvif_queue *queue)
@@ -2058,15 +2061,24 @@ int xenvif_kthread_guest_rx(void *data)
         return 0;
 }
 
+static bool xenvif_dealloc_kthread_should_stop(struct xenvif_queue *queue)
+{
+        /* Dealloc thread must remain running until all inflight
+         * packets complete.
+         */
+        return kthread_should_stop() &&
+                !atomic_read(&queue->inflight_packets);
+}
+
 int xenvif_dealloc_kthread(void *data)
 {
         struct xenvif_queue *queue = data;
 
-        while (!kthread_should_stop()) {
+        for (;;) {
                 wait_event_interruptible(queue->dealloc_wq,
                                          tx_dealloc_work_todo(queue) ||
-                                         kthread_should_stop());
-                if (kthread_should_stop())
+                                         xenvif_dealloc_kthread_should_stop(queue));
+                if (xenvif_dealloc_kthread_should_stop(queue))
                         break;
 
                 xenvif_tx_dealloc_action(queue);