ibm emac: Don't call napi_complete if napi_reschedule failed

This patch fixes a bug which would trigger the BUG_ON() at
net/core/dev.c:4156. It was found that this was due to continuing
processing in the current poll call even when the call to
napi_reschedule failed, indicating the device was already on the
polling list. This resulted in an extra call to napi_complete which
triggered the BUG_ON().

This patch ensures that we only contine processing rotting packets in
the current mal_poll call if we are not already on the polling list.
Signed-off-by: Alistair Popple <alistair@popple.id.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ibm/emac/mal.c

@@ -442,15 +442,11 @@ static int mal_poll(struct napi_struct *napi, int budget)
 		if (unlikely(mc->ops->peek_rx(mc->dev) ||
 			     test_bit(MAL_COMMAC_RX_STOPPED, &mc->flags))) {
 			MAL_DBG2(mal, "rotting packet" NL);
-			if (napi_reschedule(napi))
-				mal_disable_eob_irq(mal);
-			else
-				MAL_DBG2(mal, "already in poll list" NL);
-
-			if (budget > 0)
-				goto again;
-			else
+			if (!napi_reschedule(napi))
 				goto more_work;
+
+			mal_disable_eob_irq(mal);
+			goto again;
 		}
 		mc->ops->poll_tx(mc->dev);
 	}