Merge branch 'for-4.14/driver-lock-removal' into for-linus

- Arnd pointed out that driver_lock semaphore is superfluous, as
  driver core already provides all the necessary concurency protection.
  Removal patch from Binoy Jayan

Author: Jiri Kosina

drivers/hid/hid-core.c

@@ -2488,11 +2488,9 @@ static int hid_device_probe(struct device *dev)
 	const struct hid_device_id *id;
 	int ret = 0;
 
-	if (down_interruptible(&hdev->driver_lock))
-		return -EINTR;
 	if (down_interruptible(&hdev->driver_input_lock)) {
 		ret = -EINTR;
-		goto unlock_driver_lock;
+		goto end;
 	}
 	hdev->io_started = false;
 
@@ -2519,8 +2517,7 @@ static int hid_device_probe(struct device *dev)
 unlock:
 	if (!hdev->io_started)
 		up(&hdev->driver_input_lock);
-unlock_driver_lock:
-	up(&hdev->driver_lock);
+end:
 	return ret;
 }
 
@@ -2530,11 +2527,9 @@ static int hid_device_remove(struct device *dev)
 	struct hid_driver *hdrv;
 	int ret = 0;
 
-	if (down_interruptible(&hdev->driver_lock))
-		return -EINTR;
 	if (down_interruptible(&hdev->driver_input_lock)) {
 		ret = -EINTR;
-		goto unlock_driver_lock;
+		goto end;
 	}
 	hdev->io_started = false;
 
@@ -2550,8 +2545,7 @@ static int hid_device_remove(struct device *dev)
 
 	if (!hdev->io_started)
 		up(&hdev->driver_input_lock);
-unlock_driver_lock:
-	up(&hdev->driver_lock);
+end:
 	return ret;
 }
 
@@ -3009,7 +3003,6 @@ struct hid_device *hid_allocate_device(void)
 	init_waitqueue_head(&hdev->debug_wait);
 	INIT_LIST_HEAD(&hdev->debug_list);
 	spin_lock_init(&hdev->debug_list_lock);
-	sema_init(&hdev->driver_lock, 1);
 	sema_init(&hdev->driver_input_lock, 1);
 	mutex_init(&hdev->ll_open_lock);
 

include/linux/hid.h

@@ -526,7 +526,6 @@ struct hid_device {							/* device report descriptor */
 	struct hid_report_enum report_enum[HID_REPORT_TYPES];
 	struct work_struct led_work;					/* delayed LED worker */
 
-	struct semaphore driver_lock;					/* protects the current driver, except during input */
 	struct semaphore driver_input_lock;				/* protects the current driver */
 	struct device dev;						/* device */
 	struct hid_driver *driver;
@@ -553,7 +552,7 @@ struct hid_device {							/* device report descriptor */
 	unsigned int status;						/* see STAT flags above */
 	unsigned claimed;						/* Claimed by hidinput, hiddev? */
 	unsigned quirks;						/* Various quirks the device can pull on us */
-	bool io_started;						/* Protected by driver_lock. If IO has started */
+	bool io_started;						/* If IO has started */
 
 	struct list_head inputs;					/* The list of inputs */
 	void *hiddev;							/* The hiddev structure */