Patch "xen-netfront: Fix Rx stall during network stress and OOM" has been added to the 4.4-stable tree

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

xen-netfront: Fix Rx stall during network stress and OOM

to the 4.4-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-fix-rx-stall-during-network-stress-and-oom.patch
and it can be found in the queue-4.4 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: Thu, 19 Jan 2017 08:35:39 -0800
Subject: xen-netfront: Fix Rx stall during network stress and OOM

From: Vineeth Remanan Pillai <[email protected]>

[ Upstream commit 90c311b0eeead647b708a723dbdde1eda3dcad05 ]

During an OOM scenario, request slots could not be created as skb allocation fails. So the netback cannot pass in packets and netfront wrongly assumes that there is no more work to be done and it disables polling. This causes Rx to stall.

The issue is with the retry logic which schedules the timer if the created slots are less than NET_RX_SLOTS_MIN. The count of new request slots to be pushed are calculated as a difference between new req_prod and rsp_cons which could be more than the actual slots, if there are unconsumed responses.

The fix is to calculate the count of newly created slots as the difference between new req_prod and old req_prod.

---
 drivers/net/xen-netfront.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -321,7 +321,7 @@ 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.rsp_cons < NET_RX_SLOTS_MIN) {
+	if (req_prod - queue->rx.sring->req_prod < NET_RX_SLOTS_MIN) {
 		mod_timer(&queue->rx_refill_timer, jiffies + (HZ/10));
 		return;
 	}

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

queue-4.4/xen-netfront-fix-rx-stall-during-network-stress-and-oom.patch