[PATCH 3.16.y-ckt 093/165] USB: serial: fix infinite wait_until_sent timeout

[Luis Henriques]

3.16.7-ckt9 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Johan Hovold <johan at kernel.org>

commit f528bf4f57e43d1af4b2a5c97f09e43e0338c105 upstream.

Make sure to handle an infinite timeout (0).

Note that wait_until_sent is currently never called with a 0-timeout
argument due to a bug in tty_wait_until_sent.

Fixes: dcf010503966 ("USB: serial: add generic wait_until_sent
implementation")

Signed-off-by: Johan Hovold <johan at kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/usb/serial/generic.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c
index 1bd192290b08..904ab353ecf2 100644
--- a/drivers/usb/serial/generic.c
+++ b/drivers/usb/serial/generic.c
@@ -258,7 +258,8 @@ void usb_serial_generic_wait_until_sent(struct tty_struct *tty, long timeout)
 	 * character or at least one jiffy.
 	 */
 	period = max_t(unsigned long, (10 * HZ / bps), 1);
-	period = min_t(unsigned long, period, timeout);
+	if (timeout)
+		period = min_t(unsigned long, period, timeout);
 
 	dev_dbg(&port->dev, "%s - timeout = %u ms, period = %u ms\n",
 					__func__, jiffies_to_msecs(timeout),
@@ -268,7 +269,7 @@ void usb_serial_generic_wait_until_sent(struct tty_struct *tty, long timeout)
 		schedule_timeout_interruptible(period);
 		if (signal_pending(current))
 			break;
-		if (time_after(jiffies, expire))
+		if (timeout && time_after(jiffies, expire))
 			break;
 	}
 }