3 files changed, 123 insertions, 38 deletions

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index 4a92fc19f410..ef3026f46a37 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -176,9 +176,9 @@ struct xenvif_queue { /* Per-queue data for xenvif */
         struct xen_netif_rx_back_ring rx;
         struct sk_buff_head rx_queue;
         RING_IDX rx_last_skb_slots;
-        bool rx_queue_purge;
+        unsigned long status;
 
-        struct timer_list wake_queue;
+        struct timer_list rx_stalled;
 
         struct gnttab_copy grant_copy_op[MAX_GRANT_COPY_OPS];
 
@@ -200,7 +200,16 @@ struct xenvif_queue { /* Per-queue data for xenvif */
 
 enum state_bit_shift {
         /* This bit marks that the vif is connected */
-        VIF_STATUS_CONNECTED
+        VIF_STATUS_CONNECTED,
+        /* This bit signals the RX thread that queuing was stopped (in
+         * start_xmit), and either the timer fired or an RX interrupt came
+         */
+        QUEUE_STATUS_RX_PURGE_EVENT,
+        /* This bit tells the interrupt handler that this queue was the reason
+         * for the carrier off, so it should kick the thread. Only queues which
+         * brought it down can turn on the carrier.
+         */
+        QUEUE_STATUS_RX_STALLED
 };
 
 struct xenvif {
diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index fbdadb3d8220..48a55cda979b 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -78,8 +78,12 @@ int xenvif_poll(struct napi_struct *napi, int budget)
         /* This vif is rogue, we pretend we've there is nothing to do
          * for this vif to deschedule it from NAPI. But this interface
          * will be turned off in thread context later.
+         * Also, if a guest doesn't post enough slots to receive data on one of
+         * its queues, the carrier goes down and NAPI is descheduled here so
+         * the guest can't send more packets until it's ready to receive.
          */
-        if (unlikely(queue->vif->disabled)) {
+        if (unlikely(queue->vif->disabled ||
+                     !netif_carrier_ok(queue->vif->dev))) {
                 napi_complete(napi);
                 return 0;
         }
@@ -97,7 +101,16 @@ int xenvif_poll(struct napi_struct *napi, int budget)
 static irqreturn_t xenvif_rx_interrupt(int irq, void *dev_id)
 {
         struct xenvif_queue *queue = dev_id;
+        struct netdev_queue *net_queue =
+                netdev_get_tx_queue(queue->vif->dev, queue->id);
 
+        /* QUEUE_STATUS_RX_PURGE_EVENT is only set if either QDisc was off OR
+         * the carrier went down and this queue was previously blocked
+         */
+        if (unlikely(netif_tx_queue_stopped(net_queue) ||
+                     (!netif_carrier_ok(queue->vif->dev) &&
+                      test_bit(QUEUE_STATUS_RX_STALLED, &queue->status))))
+                set_bit(QUEUE_STATUS_RX_PURGE_EVENT, &queue->status);
         xenvif_kick_thread(queue);
 
         return IRQ_HANDLED;
@@ -125,16 +138,14 @@ void xenvif_wake_queue(struct xenvif_queue *queue)
         netif_tx_wake_queue(netdev_get_tx_queue(dev, id));
 }
 
-/* Callback to wake the queue and drain it on timeout */
-static void xenvif_wake_queue_callback(unsigned long data)
+/* Callback to wake the queue's thread and turn the carrier off on timeout */
+static void xenvif_rx_stalled(unsigned long data)
 {
         struct xenvif_queue *queue = (struct xenvif_queue *)data;
 
         if (xenvif_queue_stopped(queue)) {
-                netdev_err(queue->vif->dev, "draining TX queue\n");
-                queue->rx_queue_purge = true;
+                set_bit(QUEUE_STATUS_RX_PURGE_EVENT, &queue->status);
                 xenvif_kick_thread(queue);
-                xenvif_wake_queue(queue);
         }
 }
 
@@ -183,11 +194,11 @@ static int xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev)
          * drain.
          */
         if (!xenvif_rx_ring_slots_available(queue, min_slots_needed)) {
-                queue->wake_queue.function = xenvif_wake_queue_callback;
-                queue->wake_queue.data = (unsigned long)queue;
+                queue->rx_stalled.function = xenvif_rx_stalled;
+                queue->rx_stalled.data = (unsigned long)queue;
                 xenvif_stop_queue(queue);
-                mod_timer(&queue->wake_queue,
-                        jiffies + rx_drain_timeout_jiffies);
+                mod_timer(&queue->rx_stalled,
+                          jiffies + rx_drain_timeout_jiffies);
         }
 
         skb_queue_tail(&queue->rx_queue, skb);
@@ -515,7 +526,7 @@ int xenvif_init_queue(struct xenvif_queue *queue)
                 queue->grant_tx_handle[i] = NETBACK_INVALID_HANDLE;
         }
 
-        init_timer(&queue->wake_queue);
+        init_timer(&queue->rx_stalled);
 
         netif_napi_add(queue->vif->dev, &queue->napi, xenvif_poll,
                         XENVIF_NAPI_WEIGHT);
@@ -666,7 +677,7 @@ void xenvif_disconnect(struct xenvif *vif)
                 queue = &vif->queues[queue_index];
 
                 if (queue->task) {
-                        del_timer_sync(&queue->wake_queue);
+                        del_timer_sync(&queue->rx_stalled);
                         kthread_stop(queue->task);
                         queue->task = NULL;
                 }
@@ -708,16 +719,12 @@ void xenvif_free(struct xenvif *vif)
         /* Here we want to avoid timeout messages if an skb can be legitimately
          * stuck somewhere else. Realistically 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 stuck packets are not interesting
-         * for us here.
+         * rx_drain_timeout_msecs timeout, so give it time to drain out.
+         * Although if that other guest wakes up just before its timeout happens
+         * and takes only one skb from QDisc, it can hold onto other skbs for a
+         * longer period.
          */
-        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));
+        unsigned int worst_case_skb_lifetime = (rx_drain_timeout_msecs/1000);
 
         unregister_netdev(vif->dev);
 
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 6c4cc0f44da5..aa2093325be1 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -1869,8 +1869,7 @@ void xenvif_idx_unmap(struct xenvif_queue *queue, u16 pending_idx)
 static inline int rx_work_todo(struct xenvif_queue *queue)
 {
         return (!skb_queue_empty(&queue->rx_queue) &&
-               xenvif_rx_ring_slots_available(queue, queue->rx_last_skb_slots)) ||
-               queue->rx_queue_purge;
+               xenvif_rx_ring_slots_available(queue, queue->rx_last_skb_slots));
 }
 
 static inline int tx_work_todo(struct xenvif_queue *queue)
@@ -1935,6 +1934,75 @@ static void xenvif_start_queue(struct xenvif_queue *queue)
                 xenvif_wake_queue(queue);
 }
 
+/* Only called from the queue's thread, it handles the situation when the guest
+ * doesn't post enough requests on the receiving ring.
+ * First xenvif_start_xmit disables QDisc and start a timer, and then either the
+ * timer fires, or the guest send an interrupt after posting new request. If it
+ * is the timer, the carrier is turned off here.
+ * */
+static void xenvif_rx_purge_event(struct xenvif_queue *queue)
+{
+        /* Either the last unsuccesful skb or at least 1 slot should fit */
+        int needed = queue->rx_last_skb_slots ?
+                     queue->rx_last_skb_slots : 1;
+
+        /* It is assumed that if the guest post new slots after this, the RX
+         * interrupt will set the QUEUE_STATUS_RX_PURGE_EVENT bit and wake up
+         * the thread again
+         */
+        set_bit(QUEUE_STATUS_RX_STALLED, &queue->status);
+        if (!xenvif_rx_ring_slots_available(queue, needed)) {
+                rtnl_lock();
+                if (netif_carrier_ok(queue->vif->dev)) {
+                        /* Timer fired and there are still no slots. Turn off
+                         * everything except the interrupts
+                         */
+                        netif_carrier_off(queue->vif->dev);
+                        skb_queue_purge(&queue->rx_queue);
+                        queue->rx_last_skb_slots = 0;
+                        if (net_ratelimit())
+                                netdev_err(queue->vif->dev, "Carrier off due to lack of guest response on queue %d\n", queue->id);
+                } else {
+                        /* Probably an another queue already turned the carrier
+                         * off, make sure nothing is stucked in the internal
+                         * queue of this queue
+                         */
+                        skb_queue_purge(&queue->rx_queue);
+                        queue->rx_last_skb_slots = 0;
+                }
+                rtnl_unlock();
+        } else if (!netif_carrier_ok(queue->vif->dev)) {
+                unsigned int num_queues = queue->vif->num_queues;
+                unsigned int i;
+                /* The carrier was down, but an interrupt kicked
+                 * the thread again after new requests were
+                 * posted
+                 */
+                clear_bit(QUEUE_STATUS_RX_STALLED,
+                          &queue->status);
+                rtnl_lock();
+                netif_carrier_on(queue->vif->dev);
+                netif_tx_wake_all_queues(queue->vif->dev);
+                rtnl_unlock();
+
+                for (i = 0; i < num_queues; i++) {
+                        struct xenvif_queue *temp = &queue->vif->queues[i];
+
+                        xenvif_napi_schedule_or_enable_events(temp);
+                }
+                if (net_ratelimit())
+                        netdev_err(queue->vif->dev, "Carrier on again\n");
+        } else {
+                /* Queuing were stopped, but the guest posted
+                 * new requests and sent an interrupt
+                 */
+                clear_bit(QUEUE_STATUS_RX_STALLED,
+                          &queue->status);
+                del_timer_sync(&queue->rx_stalled);
+                xenvif_start_queue(queue);
+        }
+}
+
 int xenvif_kthread_guest_rx(void *data)
 {
         struct xenvif_queue *queue = data;
@@ -1944,8 +2012,12 @@ int xenvif_kthread_guest_rx(void *data)
                 wait_event_interruptible(queue->wq,
                                          rx_work_todo(queue) ||
                                          queue->vif->disabled ||
+                                         test_bit(QUEUE_STATUS_RX_PURGE_EVENT, &queue->status) ||
                                          kthread_should_stop());
 
+                if (kthread_should_stop())
+                        break;
+
                 /* This frontend is found to be rogue, disable it in
                  * kthread context. Currently this is only set when
                  * netback finds out frontend sends malformed packet,
@@ -1955,24 +2027,21 @@ int xenvif_kthread_guest_rx(void *data)
                  */
                 if (unlikely(queue->vif->disabled && queue->id == 0))
                         xenvif_carrier_off(queue->vif);
-
-                if (kthread_should_stop())
-                        break;
-
-                if (queue->rx_queue_purge) {
+                else if (unlikely(test_and_clear_bit(QUEUE_STATUS_RX_PURGE_EVENT,
+                                                     &queue->status))) {
+                        xenvif_rx_purge_event(queue);
+                } else if (!netif_carrier_ok(queue->vif->dev)) {
+                        /* Another queue stalled and turned the carrier off, so
+                         * purge the internal queue of queues which were not
+                         * blocked
+                         */
                         skb_queue_purge(&queue->rx_queue);
-                        queue->rx_queue_purge = false;
+                        queue->rx_last_skb_slots = 0;
                 }
 
                 if (!skb_queue_empty(&queue->rx_queue))
                         xenvif_rx_action(queue);
 
-                if (skb_queue_empty(&queue->rx_queue) &&
-                    xenvif_queue_stopped(queue)) {
-                        del_timer_sync(&queue->wake_queue);
-                        xenvif_start_queue(queue);
-                }
-
                 cond_resched();
         }