--- x/drivers/tty/serial/serial_core.c
+++ y/drivers/tty/serial/serial_core.c
@@ -622,8 +622,9 @@ static ssize_t uart_write(struct tty_str
 		return -EL3HLT;
 
 	port = uart_port_lock(state, flags);
-	if (WARN_ON_ONCE(!state->port.xmit_buf)) {
+	if (!state->port.xmit_buf) {
 		uart_port_unlock(port, flags);
+		WARN_ON_ONCE(1);
 		return 0;
 	}