staging: usbip: bugfix prevent driver unbind

Implemented pre_reset and post_reset methods of the driver to prevent the
driver from being unbound upon a device reset. Because of this also the
asynchronous reset introduced to prevent a race condition is no longer necessary
(and sometimes causes problems, because it comes later then expected).

Signed-off-by: Arjan Mels <arjan.mels@gmx.net>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Takahiro Hirofuchi <hirofuchi@users.sourceforge.net>
Cc: Max Vozeler <max@vozeler.com>
Cc: usbip-devel <usbip-devel@lists.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/usbip/stub_dev.c

@@ -26,6 +26,8 @@
 static int stub_probe(struct usb_interface *interface,
 		      const struct usb_device_id *id);
 static void stub_disconnect(struct usb_interface *interface);
+static int stub_pre_reset(struct usb_interface *interface);
+static int stub_post_reset(struct usb_interface *interface);
 
 /*
  * Define device IDs here if you want to explicitly limit exportable devices.
@@ -59,6 +61,8 @@ struct usb_driver stub_driver = {
 	.probe		= stub_probe,
 	.disconnect	= stub_disconnect,
 	.id_table	= stub_table,
+	.pre_reset	= stub_pre_reset,
+	.post_reset	= stub_post_reset,
 };
 
 /*
@@ -541,3 +545,20 @@ static void stub_disconnect(struct usb_interface *interface)
 		del_match_busid((char *)udev_busid);
 	}
 }
+
+/* 
+ * Presence of pre_reset and post_reset prevents the driver from being unbound
+ * when the device is being reset
+ */
+
+int stub_pre_reset(struct usb_interface *interface)
+{
+	dev_dbg(&interface->dev, "pre_reset\n");
+	return 0;
+}
+
+int stub_post_reset(struct usb_interface *interface)
+{
+	dev_dbg(&interface->dev, "post_reset\n");
+	return 0;
+}

drivers/staging/usbip/stub_rx.c

@@ -175,16 +175,18 @@ static int tweak_reset_device_cmd(struct urb *urb)
 	dev_info(&urb->dev->dev, "usb_queue_reset_device\n");
 
 	/*
-	 * usb_lock_device_for_reset caused a deadlock: it causes the driver
-	 * to unbind. In the shutdown the rx thread is signalled to shut down
-	 * but this thread is pending in the usb_lock_device_for_reset.
-	 *
-	 * Instead queue the reset.
-	 *
-	 * Unfortunatly an existing usbip connection will be dropped due to
-	 * driver unbinding.
+	 * With the implementation of pre_reset and post_reset the driver no 
+	 * longer unbinds. This allows the use of synchronous reset.
 	 */
-	usb_queue_reset_device(sdev->interface);
+
+	if (usb_lock_device_for_reset(sdev->udev, sdev->interface)<0)
+	{
+		dev_err(&urb->dev->dev, "could not obtain lock to reset device\n");
+		return 0;
+	}
+	usb_reset_device(sdev->udev);
+	usb_unlock_device(sdev->udev);
+
 	return 0;
 }