HID: usbhid: remove custom locking from usbhid_open/close

Now that HID core enforces serialization of transport driver open/close
calls we can remove custom locking from usbhid driver.
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/usbhid/hid-core.c

@@ -70,8 +70,6 @@ MODULE_PARM_DESC(quirks, "Add/modify USB HID quirks by specifying "
 /*
  * Input submission and I/O error handler.
  */
-static DEFINE_MUTEX(hid_open_mut);
-
 static void hid_io_error(struct hid_device *hid);
 static int hid_submit_out(struct hid_device *hid);
 static int hid_submit_ctrl(struct hid_device *hid);
@@ -680,21 +678,22 @@ static int hid_get_class_descriptor(struct usb_device *dev, int ifnum,
 static int usbhid_open(struct hid_device *hid)
 {
 	struct usbhid_device *usbhid = hid->driver_data;
-	int res = 0;
+	int res;
+
+	if (hid->quirks & HID_QUIRK_ALWAYS_POLL)
+		return 0;
 
-	mutex_lock(&hid_open_mut);
-	if (!hid->open++) {
 	res = usb_autopm_get_interface(usbhid->intf);
 	/* the device must be awake to reliably request remote wakeup */
-		if (res < 0) {
-			hid->open--;
-			res = -EIO;
-			goto done;
-		}
+	if (res < 0)
+		return -EIO;
+
 	usbhid->intf->needs_remote_wakeup = 1;
+
+	set_bit(HID_RESUME_RUNNING, &usbhid->iofl);
 	set_bit(HID_OPENED, &usbhid->iofl);
 	set_bit(HID_IN_POLLING, &usbhid->iofl);
-		set_bit(HID_RESUME_RUNNING, &usbhid->iofl);
+
 	res = hid_start_in(hid);
 	if (res) {
 		if (res != -ENOSPC) {
@@ -702,14 +701,13 @@ static int usbhid_open(struct hid_device *hid)
 			res = 0;
 		} else {
 			/* no use opening if resources are insufficient */
-				hid->open--;
+			res = -EBUSY;
 			clear_bit(HID_OPENED, &usbhid->iofl);
-				if (!(hid->quirks & HID_QUIRK_ALWAYS_POLL))
 			clear_bit(HID_IN_POLLING, &usbhid->iofl);
-				res = -EBUSY;
 			usbhid->intf->needs_remote_wakeup = 0;
 		}
 	}
+
 	usb_autopm_put_interface(usbhid->intf);
 
 	/*
@@ -718,12 +716,10 @@ static int usbhid_open(struct hid_device *hid)
 	 * Wait 50 msec for the queue to empty before allowing events
 	 * to go through hid.
 	 */
-		if (res == 0 && !(hid->quirks & HID_QUIRK_ALWAYS_POLL))
+	if (res == 0)
 		msleep(50);
+
 	clear_bit(HID_RESUME_RUNNING, &usbhid->iofl);
-	}
-done:
-	mutex_unlock(&hid_open_mut);
 	return res;
 }
 
@@ -731,27 +727,22 @@ static void usbhid_close(struct hid_device *hid)
 {
 	struct usbhid_device *usbhid = hid->driver_data;
 
-	mutex_lock(&hid_open_mut);
+	if (hid->quirks & HID_QUIRK_ALWAYS_POLL)
+		return;
 
-	/* protecting hid->open to make sure we don't restart
-	 * data acquistion due to a resumption we no longer
-	 * care about
+	/*
+	 * Make sure we don't restart data acquisition due to
+	 * a resumption we no longer care about by avoiding racing
+	 * with hid_start_in().
 	 */
 	spin_lock_irq(&usbhid->lock);
-	if (!--hid->open) {
-		if (!(hid->quirks & HID_QUIRK_ALWAYS_POLL))
 	clear_bit(HID_IN_POLLING, &usbhid->iofl);
 	clear_bit(HID_OPENED, &usbhid->iofl);
 	spin_unlock_irq(&usbhid->lock);
+
 	hid_cancel_delayed_stuff(usbhid);
-		if (!(hid->quirks & HID_QUIRK_ALWAYS_POLL)) {
 	usb_kill_urb(usbhid->urbin);
 	usbhid->intf->needs_remote_wakeup = 0;
-		}
-	} else {
-		spin_unlock_irq(&usbhid->lock);
-	}
-	mutex_unlock(&hid_open_mut);
 }
 
 /*