be2net: Synchronize be_update_queues with dev_watchdog

As pointed out by Firo Yang, a netdev tx timeout may trigger just before an
ethtool set_channels operation is started. be_tx_timeout(), which dumps
some queue structures, is not written to run concurrently with
be_update_queues(), which frees/allocates those queues structures. Add some
synchronization between the two.

Message-id: <CH2PR18MB31898E033896F9760D36BFF288C90@CH2PR18MB3189.namprd18.prod.outlook.com>
Signed-off-by: Benjamin Poirier <bpoirier@suse.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/emulex/benet/be_main.c

@@ -4698,8 +4698,13 @@ int be_update_queues(struct be_adapter *adapter)
 	int status;
 
 	if (netif_running(netdev)) {
+		/* be_tx_timeout() must not run concurrently with this
+		 * function, synchronize with an already-running dev_watchdog
+		 */
+		netif_tx_lock_bh(netdev);
 		/* device cannot transmit now, avoid dev_watchdog timeouts */
 		netif_carrier_off(netdev);
+		netif_tx_unlock_bh(netdev);
 
 		be_close(netdev);
 	}