ibmvnic: don't stop queue in xmit

If adapter's resetting bit is on, discard the packet but don't stop the
transmit queue - instead leave that to the reset code. With this change,
it is possible that we may get several calls to ibmvnic_xmit() that simply
discard packets and return.

But if we stop the queue here, we might end up doing so just after
__ibmvnic_open() started the queues (during a hard/soft reset) and before
the ->resetting bit was cleared. If that happens, there will be no one to
restart queue and transmissions will be blocked indefinitely.

This can cause a TIMEOUT reset and with auto priority failover enabled,
an unnecessary FAILOVER reset to less favored backing device and then a
FAILOVER back to the most favored backing device. If we hit the window
repeatedly, we can get stuck in a loop of TIMEOUT, FAILOVER, FAILOVER
resets leaving the adapter unusable for extended periods of time.

Fixes: 7f5b030 ("ibmvnic: Free skb's in cases of failure in transmit")
Reported-by: Abdul Haleem <abdhalee@in.ibm.com>
Reported-by: Vaishnavi Bhat <vaish123@in.ibm.com>
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.ibm.com>
Reviewed-by: Dany Madden <drt@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: sukadev

drivers/net/ethernet/ibm/ibmvnic.c

@@ -1724,8 +1724,6 @@ static netdev_tx_t ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
 	ind_bufp = &tx_scrq->ind_buf;
 
 	if (test_bit(0, &adapter->resetting)) {
-		if (!netif_subqueue_stopped(netdev, skb))
-			netif_stop_subqueue(netdev, queue_num);
 		dev_kfree_skb_any(skb);
 
 		tx_send_failed++;