tty: USB can now use the shutdown method for kref based freeing of ports

Signed-off-by: Alan Cox <alan@linux.intel.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 7 insertions, 21 deletions

diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index 21dd72a5a715..31c7a0939b98 100644
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -316,16 +316,19 @@ static void serial_do_down(struct usb_serial_port *port)
  *
  *      Do the resource freeing and refcount dropping for the port. We must
  *      be careful about ordering and we must avoid freeing up the console.
+ *
+ *      Called when the last tty kref is dropped.
  */
 
-static void serial_do_free(struct usb_serial_port *port)
+static void serial_do_free(struct tty_struct *tty)
 {
+        struct usb_serial_port *port = tty->driver_data;
         struct usb_serial *serial;
         struct module *owner;
 
         /* The console is magical, do not hang up the console hardware
            or there will be tears */
-        if (port->console)
+        if (port == NULL || port->console)
                 return;
 
         serial = port->serial;
@@ -350,30 +353,12 @@ static void serial_close(struct tty_struct *tty, struct file *filp)
 
         dbg("%s - port %d", __func__, port->number);
 
-        /* FIXME:
-           This leaves a very narrow race. Really we should do the
-           serial_do_free() on tty->shutdown(), but tty->shutdown can
-           be called from IRQ context and serial_do_free can sleep.
-
-           The right fix is probably to make the tty free (which is rare)
-           and thus tty->shutdown() occur via a work queue and simplify all
-           the drivers that use it.
-        */
-        if (tty_hung_up_p(filp)) {
-                /* serial_hangup already called serial_down at this point.
-                   Another user may have already reopened the port but
-                   serial_do_free is refcounted */
-                serial_do_free(port);
-                return;
-        }
-
         if (tty_port_close_start(&port->port, tty, filp) == 0)
                 return;
-
         serial_do_down(port);           
         tty_port_close_end(&port->port, tty);
         tty_port_tty_set(&port->port, NULL);
-        serial_do_free(port);
+
 }
 
 static void serial_hangup(struct tty_struct *tty)
@@ -1243,6 +1228,7 @@ static const struct tty_operations serial_ops = {
         .chars_in_buffer =      serial_chars_in_buffer,
         .tiocmget =             serial_tiocmget,
         .tiocmset =             serial_tiocmset,
+        .shutdown =             serial_do_free,
         .proc_fops =            &serial_proc_fops,
 };