[PATCH 029/102] USB: serial: fix hang when opening port

[Luis Henriques]

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

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

From: Ming Lei <tom.leiming at gmail.com>

commit eba0e3c3a0ba7b96f01cbe997680f6a4401a0bfc upstream.

Johan's 'fix use-after-free in TIOCMIWAIT' patchset[1] introduces
one bug which can cause kernel hang when opening port.

This patch initialized the 'port->delta_msr_wait' waitqueue head
to fix the bug which is introduced in 3.9-rc4.

[1], http://marc.info/?l=linux-usb&m=136368139627876&w=2

Signed-off-by: Ming Lei <tom.leiming at gmail.com>
Acked-by: Johan Hovold <jhovold at gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/usb/serial/usb-serial.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index 2418551..fb09885 100644
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -899,6 +899,7 @@ static int usb_serial_probe(struct usb_interface *interface,
 		port->port.ops = &serial_port_ops;
 		port->serial = serial;
 		spin_lock_init(&port->lock);
+		init_waitqueue_head(&port->delta_msr_wait);
 		/* Keep this for private driver use for the moment but
 		   should probably go away */
 		INIT_WORK(&port->work, usb_serial_port_work);
-- 
1.8.1.2