USB: total removal of multithreaded probing in usb

The whole approach is simply wrong.  Forking a thread means that
  - errors are ignored
  - locking is ignored

Doing this correctly would require major surgery for questionable benefit.
Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/hub.c

@@ -87,9 +87,6 @@ static DECLARE_WAIT_QUEUE_HEAD(khubd_wait);
 
 static struct task_struct *khubd_task;
 
-/* multithreaded probe logic */
-static int multithread_probe = 0;
-
 /* cycle leds on hubs that aren't blinking for attention */
 static int blinkenlights = 0;
 module_param (blinkenlights, bool, S_IRUGO);
@@ -1256,9 +1253,28 @@ static inline void show_string(struct usb_device *udev, char *id, char *string)
 static int __usb_port_suspend(struct usb_device *, int port1);
 #endif
 
-static int __usb_new_device(void *void_data)
+/**
+ * usb_new_device - perform initial device setup (usbcore-internal)
+ * @udev: newly addressed device (in ADDRESS state)
+ *
+ * This is called with devices which have been enumerated, but not yet
+ * configured.  The device descriptor is available, but not descriptors
+ * for any device configuration.  The caller must have locked either
+ * the parent hub (if udev is a normal device) or else the
+ * usb_bus_list_lock (if udev is a root hub).  The parent's pointer to
+ * udev has already been installed, but udev is not yet visible through
+ * sysfs or other filesystem code.
+ *
+ * It will return if the device is configured properly or not.  Zero if
+ * the interface was registered with the driver core; else a negative
+ * errno value.
+ *
+ * This call is synchronous, and may not be used in an interrupt context.
+ *
+ * Only the hub driver or root-hub registrar should ever call this.
+ */
+int usb_new_device(struct usb_device *udev)
 {
-	struct usb_device *udev = void_data;
 	int err;
 
 	/* Lock ourself into memory in order to keep a probe sequence
@@ -1375,44 +1391,6 @@ fail:
 	goto exit;
 }
 
-/**
- * usb_new_device - perform initial device setup (usbcore-internal)
- * @udev: newly addressed device (in ADDRESS state)
- *
- * This is called with devices which have been enumerated, but not yet
- * configured.  The device descriptor is available, but not descriptors
- * for any device configuration.  The caller must have locked either
- * the parent hub (if udev is a normal device) or else the
- * usb_bus_list_lock (if udev is a root hub).  The parent's pointer to
- * udev has already been installed, but udev is not yet visible through
- * sysfs or other filesystem code.
- *
- * The return value for this function depends on if the
- * multithread_probe variable is set or not.  If it's set, it will
- * return a if the probe thread was successfully created or not.  If the
- * variable is not set, it will return if the device is configured
- * properly or not.  interfaces, in sysfs); else a negative errno value.
- *
- * This call is synchronous, and may not be used in an interrupt context.
- *
- * Only the hub driver or root-hub registrar should ever call this.
- */
-int usb_new_device(struct usb_device *udev)
-{
-	struct task_struct *probe_task;
-	int ret = 0;
-
-	if (multithread_probe) {
-		probe_task = kthread_run(__usb_new_device, udev,
-					 "usb-probe-%s", udev->devnum);
-		if (IS_ERR(probe_task))
-			ret = PTR_ERR(probe_task);
-	} else
-		ret = __usb_new_device(udev);
-
-	return ret;
-}
-
 static int hub_port_status(struct usb_hub *hub, int port1,
 			       u16 *status, u16 *change)
 {