Commit fba594a8 authored Sep 02, 2014 by Peter Hurley Committed by Greg Kroah-Hartman Sep 08, 2014

serial: core: Remove unsafe x_char optimization

uart_unthrottle() attempts to avoid sending START and the previous
x_char if the previous x_char has not yet been sent. However, this
optimization could leave the sender in a throttled state; for example,
if the sender is throttled and this unthrottle coincides with a manual
tcflow(TCION) from user-space, then neither START would be sent.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent c235ccc1

drivers/tty/serial/serial_core.c

+2 −6

Original line number	Diff line number	Diff line
		@@ -647,12 +647,8 @@ static void uart_unthrottle(struct tty_struct *tty)
		mask &= ~port->flags;
		}

		if (mask & UPF_SOFT_FLOW) {
		if (port->x_char)
		port->x_char = 0;
		else
		if (mask & UPF_SOFT_FLOW)
		uart_send_xchar(tty, START_CHAR(tty));
		}

		if (mask & UPF_HARD_FLOW)
		uart_set_mctrl(port, TIOCM_RTS);