tty_port: add "tty_port_open" helper

For the moment this just moves the USB logic over and fixes the 'what if
we open and hangup at the same time' race noticed by Oliver Neukum.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

3 files changed, 64 insertions, 31 deletions

diff --git a/drivers/char/tty_port.c b/drivers/char/tty_port.c
index c63f3d33914a..b22a61a4fbe5 100644
--- a/drivers/char/tty_port.c
+++ b/drivers/char/tty_port.c
@@ -99,10 +99,11 @@ EXPORT_SYMBOL(tty_port_tty_set);
 
 static void tty_port_shutdown(struct tty_port *port)
 {
+        mutex_lock(&port->mutex);
         if (port->ops->shutdown &&
                 test_and_clear_bit(ASYNCB_INITIALIZED, &port->flags))
                         port->ops->shutdown(port);
-
+        mutex_unlock(&port->mutex);
 }
 
 /**
@@ -381,3 +382,36 @@ void tty_port_close(struct tty_port *port, struct tty_struct *tty,
         tty_port_tty_set(port, NULL);
 }
 EXPORT_SYMBOL(tty_port_close);
+
+int tty_port_open(struct tty_port *port, struct tty_struct *tty,
+                                                        struct file *filp)
+{
+        spin_lock_irq(&port->lock);
+        if (!tty_hung_up_p(filp))
+                ++port->count;
+        spin_unlock_irq(&port->lock);
+        tty_port_tty_set(port, tty);
+
+        /*
+         * Do the device-specific open only if the hardware isn't
+         * already initialized. Serialize open and shutdown using the
+         * port mutex.
+         */
+
+        mutex_lock(&port->mutex);
+
+        if (!test_bit(ASYNCB_INITIALIZED, &port->flags)) {
+                if (port->ops->activate) {
+                        int retval = port->ops->activate(port, tty);
+                        if (retval) {
+                                mutex_unlock(&port->mutex);
+                                return retval;
+                        }
+                }
+                set_bit(ASYNCB_INITIALIZED, &port->flags);
+        }
+        mutex_unlock(&port->mutex);
+        return tty_port_block_til_ready(port, tty, filp);
+}
+
+EXPORT_SYMBOL(tty_port_open);
diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index bd3fa7ff15b1..b0649d92251f 100644
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -247,41 +247,31 @@ static int serial_install(struct tty_driver *driver, struct tty_struct *tty)
         return retval;
 }
 
-static int serial_open(struct tty_struct *tty, struct file *filp)
+static int serial_activate(struct tty_port *tport, struct tty_struct *tty)
 {
-        struct usb_serial_port *port = tty->driver_data;
+        struct usb_serial_port *port =
+                container_of(tport, struct usb_serial_port, port);
         struct usb_serial *serial = port->serial;
         int retval;
 
-        dbg("%s - port %d", __func__, port->number);
-
-        spin_lock_irq(&port->port.lock);
-        if (!tty_hung_up_p(filp))
-                ++port->port.count;
-        spin_unlock_irq(&port->port.lock);
-        tty_port_tty_set(&port->port, tty);
+        if (mutex_lock_interruptible(&port->mutex))
+                return -ERESTARTSYS;
+        mutex_lock(&serial->disc_mutex);
+        if (serial->disconnected)
+                retval = -ENODEV;
+        else
+                retval = port->serial->type->open(tty, port);
+        mutex_unlock(&serial->disc_mutex);
+        mutex_unlock(&port->mutex);
+        return retval;
+}
 
-        /* Do the device-specific open only if the hardware isn't
-         * already initialized.
-         */
-        if (!test_bit(ASYNCB_INITIALIZED, &port->port.flags)) {
-                if (mutex_lock_interruptible(&port->mutex))
-                        return -ERESTARTSYS;
-                mutex_lock(&serial->disc_mutex);
-                if (serial->disconnected)
-                        retval = -ENODEV;
-                else
-                        retval = port->serial->type->open(tty, port);
-                mutex_unlock(&serial->disc_mutex);
-                mutex_unlock(&port->mutex);
-                if (retval)
-                        return retval;
-                set_bit(ASYNCB_INITIALIZED, &port->port.flags);
-        }
+static int serial_open(struct tty_struct *tty, struct file *filp)
+{
+        struct usb_serial_port *port = tty->driver_data;
 
-        /* Now do the correct tty layer semantics */
-        retval = tty_port_block_til_ready(&port->port, tty, filp);
-        return retval;
+        dbg("%s - port %d", __func__, port->number);
+        return tty_port_open(&port->port, tty, filp);
 }
 
 /**
@@ -725,6 +715,7 @@ static void serial_dtr_rts(struct tty_port *port, int on)
 static const struct tty_port_operations serial_port_ops = {
         .carrier_raised = serial_carrier_raised,
         .dtr_rts = serial_dtr_rts,
+        .activate = serial_activate,
 };
 
 int usb_serial_probe(struct usb_interface *interface,
diff --git a/include/linux/tty.h b/include/linux/tty.h
index f0f43d08d8b8..6352ac257fcb 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -190,9 +190,15 @@ struct tty_port_operations {
         /* Control the DTR line */
         void (*dtr_rts)(struct tty_port *port, int raise);
         /* Called when the last close completes or a hangup finishes
-           IFF the port was initialized. Do not use to free resources */
+           IFF the port was initialized. Do not use to free resources. Called
+           under the port mutex to serialize against activate/shutdowns */
         void (*shutdown)(struct tty_port *port);
         void (*drop)(struct tty_port *port);
+        /* Called under the port mutex from tty_port_open, serialized using
+           the port mutex */
+        /* FIXME: long term getting the tty argument *out* of this would be
+           good for consoles */
+        int (*activate)(struct tty_port *port, struct tty_struct *tty);
 };
         
 struct tty_port {
@@ -467,6 +473,8 @@ extern int tty_port_close_start(struct tty_port *port,
 extern void tty_port_close_end(struct tty_port *port, struct tty_struct *tty);
 extern void tty_port_close(struct tty_port *port,
                                 struct tty_struct *tty, struct file *filp);
+extern int tty_port_open(struct tty_port *port,
+                                struct tty_struct *tty, struct file *filp);
 extern inline int tty_port_users(struct tty_port *port)
 {
         return port->count + port->blocked_open;