Patch "xen-netfront: Rework the fix for Rx stall during OOM and network stress" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

xen-netfront: Rework the fix for Rx stall during OOM and network stress

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
xen-netfront-rework-the-fix-for-rx-stall-during-oom-and-network-stress.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Vineeth Remanan Pillai <[email protected]>
Date: Tue, 7 Feb 2017 18:59:01 +0000
Subject: xen-netfront: Rework the fix for Rx stall during OOM and network stress

From: Vineeth Remanan Pillai <[email protected]>

commit 538d92912d3190a1dd809233a0d57277459f37b2 upstream.

The commit 90c311b0eeea ("xen-netfront: Fix Rx stall during network stress and OOM") caused the refill timer to be triggerred almost on all invocations of xennet_alloc_rx_buffers for certain workloads. This reworks the fix by reverting to the old behaviour and taking into consideration the skb allocation failure. Refill timer is now triggered on insufficient requests or skb allocation failure.

---
 drivers/net/xen-netfront.c |   14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

@@ -281,6 +281,7 @@ static void xennet_alloc_rx_buffers(stru
 {
 	RING_IDX req_prod = queue->rx.req_prod_pvt;
 	int notify;
+	int err = 0;
 
 	if (unlikely(!netif_carrier_ok(queue->info->netdev)))
 		return;

@@ -295,8 +296,10 @@ static void xennet_alloc_rx_buffers(stru
 		struct xen_netif_rx_request *req;
 
 		skb = xennet_alloc_one_rx_buffer(queue);
-		if (!skb)
+		if (!skb) {
+			err = -ENOMEM;
 			break;
+		}
 
 		id = xennet_rxidx(req_prod);
 

@@ -320,8 +323,13 @@ static void xennet_alloc_rx_buffers(stru
 
 	queue->rx.req_prod_pvt = req_prod;
 
-	/* Not enough requests? Try again later. */
-	if (req_prod - queue->rx.sring->req_prod < NET_RX_SLOTS_MIN) {
+	/* Try again later if there are not enough requests or skb allocation
+	 * failed.
+	 * Enough requests is quantified as the sum of newly created slots and
+	 * the unconsumed slots at the backend.
+	 */
+	if (req_prod - queue->rx.rsp_cons < NET_RX_SLOTS_MIN ||
+	    unlikely(err)) {
 		mod_timer(&queue->rx_refill_timer, jiffies + (HZ/10));
 		return;
 	}

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/xen-netfront-rework-the-fix-for-rx-stall-during-oom-and-network-stress.patch