sfc: Don't wake TX queues while they're being flushed

Signed-off-by: NBen Hutchings <bhutchings@solarflare.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/sfc/tx.c

@@ -400,7 +400,7 @@ void efx_xmit_done(struct efx_tx_queue *tx_queue, unsigned int index)
 	 * separates the update of read_count from the test of
 	 * stopped. */
 	smp_mb();
-	if (unlikely(tx_queue->stopped)) {
+	if (unlikely(tx_queue->stopped) && likely(efx->port_enabled)) {
 		fill_level = tx_queue->insert_count - tx_queue->read_count;
 		if (fill_level < EFX_NETDEV_TX_THRESHOLD(tx_queue)) {
 			EFX_BUG_ON_PARANOID(!efx_dev_registered(efx));