ixgbe: do not stop tx queues in ixgbe_set_tso

Disabling TSO can cause the dev_watchdog timer to be triggered because
when TSO is disabled netif_tx_stop_all_queues is called.  If the watchdog
timer fires while the queues are stopped and traffic has not recently been
sent on a paticular queue this is falsly identified as a hang and
ndo_tx_timeout() is called.  This is ocossionally seen during testing.

This removes the netif_tx_stop_all_queues() it is not needed.  The scheduler
submits skb's with dev_hard_start_xmit(), this checks if netif_needs_gso and
if so it calls dev_gso_segment.  Disabling TSO will cause dev_hard_start_xmit()
to do the gso processing.   However ixgbe does not use the features flags to
determine if it needs to use tso or not instead it uses skb->gso_size so
ixgbe will process these frames correctly regardless of the netdev features
flag.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Acked-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ixgbe/ixgbe_ethtool.c

@@ -441,10 +441,8 @@ static int ixgbe_set_tso(struct net_device *netdev, u32 data)
 		netdev->features |= NETIF_F_TSO;
 		netdev->features |= NETIF_F_TSO6;
 	} else {
-		netif_tx_stop_all_queues(netdev);
 		netdev->features &= ~NETIF_F_TSO;
 		netdev->features &= ~NETIF_F_TSO6;
-		netif_tx_start_all_queues(netdev);
 	}
 	return 0;
 }