[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, 13 insertions, 6 deletions

diff --git a/drivers/usb/serial/keyspan_pda.c b/drivers/usb/serial/keyspan_pda.c
index 7fd0aa9eccf6..635c384cb15a 100644
--- a/drivers/usb/serial/keyspan_pda.c
+++ b/drivers/usb/serial/keyspan_pda.c
@@ -520,9 +520,13 @@ static int keyspan_pda_write(struct usb_serial_port *port,
            the TX urb is in-flight (wait until it completes)
            the device is full (wait until it says there is room)
         */
-        if (port->write_urb->status == -EINPROGRESS || priv->tx_throttled ) {
-                return( 0 );
+        spin_lock(&port->lock);
+        if (port->write_urb_busy || priv->tx_throttled) {
+                spin_unlock(&port->lock);
+                return 0;
         }
+        port->write_urb_busy = 1;
+        spin_unlock(&port->lock);
 
         /* At this point the URB is in our control, nobody else can submit it
            again (the only sudden transition was the one from EINPROGRESS to
@@ -570,7 +574,7 @@ static int keyspan_pda_write(struct usb_serial_port *port,
                 memcpy (port->write_urb->transfer_buffer, buf, count);
                 /* send the data out the bulk port */
                 port->write_urb->transfer_buffer_length = count;
-                
+
                 priv->tx_room -= count;
 
                 port->write_urb->dev = port->serial->dev;
@@ -593,6 +597,8 @@ static int keyspan_pda_write(struct usb_serial_port *port,
 
         rc = count;
 exit:
+        if (rc < 0)
+                port->write_urb_busy = 0;
         return rc;
 }
 
@@ -602,6 +608,7 @@ static void keyspan_pda_write_bulk_callback (struct urb *urb, struct pt_regs *re
         struct usb_serial_port *port = (struct usb_serial_port *)urb->context;
         struct keyspan_pda_private *priv;
 
+        port->write_urb_busy = 0;
         priv = usb_get_serial_port_data(port);
 
         /* queue up a wakeup at scheduler time */
@@ -626,12 +633,12 @@ static int keyspan_pda_write_room (struct usb_serial_port *port)
 static int keyspan_pda_chars_in_buffer (struct usb_serial_port *port)
 {
         struct keyspan_pda_private *priv;
-        
+
         priv = usb_get_serial_port_data(port);
-        
+
         /* when throttled, return at least WAKEUP_CHARS to tell select() (via
            n_tty.c:normal_poll() ) that we're not writeable. */
-        if( port->write_urb->status == -EINPROGRESS || priv->tx_throttled )
+        if (port->write_urb_busy || priv->tx_throttled)
                 return 256;
         return 0;
 }