Ordering problem in serial_core.c

[Eugene Bordenkircher <eugebo@gmail.com>]

There is an ordering problem with closing a UART in the serial core.
If the line discipline is throttling the port when close is called, it
tries to unthrottle the port which, in the case of soft flow, tries to
send the XON character.  This doesn't work well since at this point
the uart has been shutdown.

The simple reordering shown below will seems to fix the problem, but
please comment if there are other side effects I am not seeing.

Eugene T. Bordenkircher

--- linux_kernel/drivers/serial/serial_core.c.orig	2009-08-13
14:58:04.000000000 -0700
+++ linux_kernel/drivers/serial/serial_core.c	2009-08-13
15:29:02.000000000 -0700
@@ -1317,11 +1317,11 @@
 		uart_wait_until_sent(tty, port->timeout);
 	}

+	tty_ldisc_flush(tty);
+
 	uart_shutdown(state);
 	uart_flush_buffer(tty);

-	tty_ldisc_flush(tty);
-
 	tty->closing = 0;
 	state->info.port.tty = NULL;