xen/netback: don't call kfree_skb() under spin_lock_irqsave()

It is not allowed to call kfree_skb() from hardware interrupt
context or with interrupts being disabled. So replace kfree_skb()
with dev_kfree_skb_irq() under spin_lock_irqsave().

Fixes: be81992 ("xen/netback: don't queue unlimited number of packages")
Signed-off-by: Yang Yingliang <[email protected]>
Reviewed-by: Paul Durrant <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Paolo Abeni <[email protected]>

Author: Yang Yingliang

drivers/net/xen-netback/rx.c

@@ -92,7 +92,7 @@ void xenvif_rx_queue_tail(struct xenvif_queue *queue, struct sk_buff *skb)
 		struct net_device *dev = queue->vif->dev;
 
 		netif_tx_stop_queue(netdev_get_tx_queue(dev, queue->id));
-		kfree_skb(skb);
+		dev_kfree_skb_irq(skb);
 		queue->vif->dev->stats.rx_dropped++;
 	} else {
 		if (skb_queue_empty(&queue->rx_queue))