[PATCH] USB: add ability for usb-serial drivers to determine if their write urb is currently being used.

This removes a lot of racy and buggy code by trying to check the status of the urb.

Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 9 insertions, 4 deletions

diff --git a/drivers/usb/serial/safe_serial.c b/drivers/usb/serial/safe_serial.c
index 0e85ed6c6c19..96a17568cbf1 100644
--- a/drivers/usb/serial/safe_serial.c
+++ b/drivers/usb/serial/safe_serial.c
@@ -299,10 +299,14 @@ static int safe_write (struct usb_serial_port *port, const unsigned char *buf, i
                 dbg ("%s - write request of 0 bytes", __FUNCTION__);
                 return (0);
         }
-        if (port->write_urb->status == -EINPROGRESS) {
-                dbg ("%s - already writing", __FUNCTION__);
-                return (0);
+        spin_lock(&port->lock);
+        if (port->write_urb_busy) {
+                spin_unlock(&port->lock);
+                dbg("%s - already writing", __FUNCTION__);
+                return 0;
         }
+        port->write_urb_busy = 1;
+        spin_unlock(&port->lock);
 
         packet_length = port->bulk_out_size;    // get max packetsize
 
@@ -354,6 +358,7 @@ static int safe_write (struct usb_serial_port *port, const unsigned char *buf, i
 #endif
         port->write_urb->dev = port->serial->dev;
         if ((result = usb_submit_urb (port->write_urb, GFP_KERNEL))) {
+                port->write_urb_busy = 0;
                 err ("%s - failed submitting write urb, error %d", __FUNCTION__, result);
                 return 0;
         }
@@ -368,7 +373,7 @@ static int safe_write_room (struct usb_serial_port *port)
 
         dbg ("%s", __FUNCTION__);
 
-        if (port->write_urb->status != -EINPROGRESS)
+        if (port->write_urb_busy)
                 room = port->bulk_out_size - (safe ? 2 : 0);
 
         if (room) {