usb-serial: straighten out serial_open

This patch (as1291) removes a bunch of code from serial_open(), things
that were rendered unnecessary by earlier patches.  A missing spinlock
is added to protect port->port.count, which needs to be incremented
even if the open fails but not if the tty has gotten a hangup.  The
test for whether the hardware has been initialized, based on the use
count, is replaced by a more transparent test of the
ASYNCB_INITIALIZED bit in the port flags.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 22 insertions, 37 deletions

diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index 9a3258046c8c..9d7ca4868d37 100644
--- a/drivers/usb/serial/usb-serial.c
+++ b/drivers/usb/serial/usb-serial.c
@@ -245,55 +245,40 @@ 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_open(struct tty_struct *tty, struct file *filp)
 {
-        struct usb_serial *serial;
-        struct usb_serial_port *port;
-        int retval = 0;
-        int first = 0;
-
-        port = tty->driver_data;
-        serial = port->serial;
+        struct usb_serial_port *port = tty->driver_data;
+        struct usb_serial *serial = port->serial;
+        int retval;
 
         dbg("%s - port %d", __func__, port->number);
 
-        if (mutex_lock_interruptible(&port->mutex))
-                return -ERESTARTSYS;
-
-        ++port->port.count;
+        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 the console is attached, the device is already open */
-        if (port->port.count == 1 && !port->console) {
-                first = 1;
+        /* 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);
-
-                /* only call the device specific open if this
-                 * is the first time the port is opened */
-                retval = serial->type->open(tty, port);
-                if (retval)
-                        goto bailout_module_put;
+                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);
         }
-        mutex_unlock(&port->mutex);
+
         /* Now do the correct tty layer semantics */
         retval = tty_port_block_til_ready(&port->port, tty, filp);
-        if (retval == 0) {
-                if (!first)
-                        usb_serial_put(serial);
-                return 0;
-        }
-        mutex_lock(&port->mutex);
-        if (first == 0)
-                goto bailout_mutex_unlock;
-        /* Undo the initial port actions */
-        mutex_lock(&serial->disc_mutex);
-bailout_module_put:
-        mutex_unlock(&serial->disc_mutex);
-bailout_mutex_unlock:
-        port->port.count = 0;
-        mutex_unlock(&port->mutex);
         return retval;
 }