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>

1 files changed, 35 insertions, 1 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);