xen-netback: notify immediately after pushing Tx response.

This fixes a performance regression introduced by
7fbb9d8415d4a51cf542e87cf3a717a9f7e6aedc (xen-netback: release pending
index before pushing Tx responses)

Moving the notify outside of the spin locks means it can be delayed a
long time (if the dealloc thread is descheduled or there is an
interrupt or softirq).

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Zoltan Kiss <zoltan.kiss@linaro.org>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 11 deletions

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index cab9f5257f57..997cf0901ac2 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -96,6 +96,7 @@ static void xenvif_idx_release(struct xenvif_queue *queue, u16 pending_idx,
 static void make_tx_response(struct xenvif_queue *queue,
                              struct xen_netif_tx_request *txp,
                              s8       st);
+static void push_tx_responses(struct xenvif_queue *queue);
 
 static inline int tx_work_todo(struct xenvif_queue *queue);
 
@@ -655,15 +656,10 @@ static void xenvif_tx_err(struct xenvif_queue *queue,
         unsigned long flags;
 
         do {
-                int notify;
-
                 spin_lock_irqsave(&queue->response_lock, flags);
                 make_tx_response(queue, txp, XEN_NETIF_RSP_ERROR);
-                RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&queue->tx, notify);
+                push_tx_responses(queue);
                 spin_unlock_irqrestore(&queue->response_lock, flags);
-                if (notify)
-                        notify_remote_via_irq(queue->tx_irq);
-
                 if (cons == end)
                         break;
                 txp = RING_GET_REQUEST(&queue->tx, cons++);
@@ -1657,7 +1653,6 @@ static void xenvif_idx_release(struct xenvif_queue *queue, u16 pending_idx,
 {
         struct pending_tx_info *pending_tx_info;
         pending_ring_idx_t index;
-        int notify;
         unsigned long flags;
 
         pending_tx_info = &queue->pending_tx_info[pending_idx];
@@ -1673,12 +1668,9 @@ static void xenvif_idx_release(struct xenvif_queue *queue, u16 pending_idx,
         index = pending_index(queue->pending_prod++);
         queue->pending_ring[index] = pending_idx;
 
-        RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&queue->tx, notify);
+        push_tx_responses(queue);
 
         spin_unlock_irqrestore(&queue->response_lock, flags);
-
-        if (notify)
-                notify_remote_via_irq(queue->tx_irq);
 }
 
 
@@ -1699,6 +1691,15 @@ static void make_tx_response(struct xenvif_queue *queue,
         queue->tx.rsp_prod_pvt = ++i;
 }
 
+static void push_tx_responses(struct xenvif_queue *queue)
+{
+        int notify;
+
+        RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&queue->tx, notify);
+        if (notify)
+                notify_remote_via_irq(queue->tx_irq);
+}
+
 static struct xen_netif_rx_response *make_rx_response(struct xenvif_queue *queue,
                                              u16      id,
                                              s8       st,