Input: use full RCU API

RT guys alerted me to the fact that in their tree spinlocks
are preemptible and it is better to use full RCU API
(rcu_read_lock()/rcu_read_unlock()) to be safe.
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/evdev.c

@@ -63,10 +63,7 @@ static void evdev_pass_event(struct evdev_client *client,
 }
 
 /*
- * Pass incoming event to all connected clients. Note that we are
- * caleld under a spinlock with interrupts off so we don't need
- * to use rcu_read_lock() here. Writers will be using syncronize_sched()
- * instead of synchrnoize_rcu().
+ * Pass incoming event to all connected clients.
  */
 static void evdev_event(struct input_handle *handle,
 			unsigned int type, unsigned int code, int value)
@@ -80,6 +77,8 @@ static void evdev_event(struct input_handle *handle,
 	event.code = code;
 	event.value = value;
 
+	rcu_read_lock();
+
 	client = rcu_dereference(evdev->grab);
 	if (client)
 		evdev_pass_event(client, &event);
@@ -87,6 +86,8 @@ static void evdev_event(struct input_handle *handle,
 		list_for_each_entry_rcu(client, &evdev->client_list, node)
 			evdev_pass_event(client, &event);
 
+	rcu_read_unlock();
+
 	wake_up_interruptible(&evdev->wait);
 }
 
@@ -142,12 +143,7 @@ static int evdev_grab(struct evdev *evdev, struct evdev_client *client)
 		return error;
 
 	rcu_assign_pointer(evdev->grab, client);
-	/*
-	 * We don't use synchronize_rcu() here because read-side
-	 * critical section is protected by a spinlock instead
-	 * of rcu_read_lock().
-	 */
-	synchronize_sched();
+	synchronize_rcu();
 
 	return 0;
 }
@@ -158,7 +154,7 @@ static int evdev_ungrab(struct evdev *evdev, struct evdev_client *client)
 		return  -EINVAL;
 
 	rcu_assign_pointer(evdev->grab, NULL);
-	synchronize_sched();
+	synchronize_rcu();
 	input_release_device(&evdev->handle);
 
 	return 0;
@@ -170,7 +166,7 @@ static void evdev_attach_client(struct evdev *evdev,
 	spin_lock(&evdev->client_lock);
 	list_add_tail_rcu(&client->node, &evdev->client_list);
 	spin_unlock(&evdev->client_lock);
-	synchronize_sched();
+	synchronize_rcu();
 }
 
 static void evdev_detach_client(struct evdev *evdev,
@@ -179,7 +175,7 @@ static void evdev_detach_client(struct evdev *evdev,
 	spin_lock(&evdev->client_lock);
 	list_del_rcu(&client->node);
 	spin_unlock(&evdev->client_lock);
-	synchronize_sched();
+	synchronize_rcu();
 }
 
 static int evdev_open_device(struct evdev *evdev)

drivers/input/input.c

@@ -65,16 +65,16 @@ static int input_defuzz_abs_event(int value, int old_val, int fuzz)
 
 /*
  * Pass event through all open handles. This function is called with
- * dev->event_lock held and interrupts disabled. Because of that we
- * do not need to use rcu_read_lock() here although we are using RCU
- * to access handle list. Note that because of that write-side uses
- * synchronize_sched() instead of synchronize_ru().
+ * dev->event_lock held and interrupts disabled.
  */
 static void input_pass_event(struct input_dev *dev,
 			     unsigned int type, unsigned int code, int value)
 {
-	struct input_handle *handle = rcu_dereference(dev->grab);
+	struct input_handle *handle;
+
+	rcu_read_lock();
 
+	handle = rcu_dereference(dev->grab);
 	if (handle)
 		handle->handler->event(handle, type, code, value);
 	else
@@ -82,6 +82,7 @@ static void input_pass_event(struct input_dev *dev,
 			if (handle->open)
 				handle->handler->event(handle,
 							type, code, value);
+	rcu_read_unlock();
 }
 
 /*
@@ -293,9 +294,11 @@ void input_inject_event(struct input_handle *handle,
 	if (is_event_supported(type, dev->evbit, EV_MAX)) {
 		spin_lock_irqsave(&dev->event_lock, flags);
 
+		rcu_read_lock();
 		grab = rcu_dereference(dev->grab);
 		if (!grab || grab == handle)
 			input_handle_event(dev, type, code, value);
+		rcu_read_unlock();
 
 		spin_unlock_irqrestore(&dev->event_lock, flags);
 	}
@@ -325,11 +328,7 @@ int input_grab_device(struct input_handle *handle)
 	}
 
 	rcu_assign_pointer(dev->grab, handle);
-	/*
-	 * Not using synchronize_rcu() because read-side is protected
-	 * by a spinlock with interrupts off instead of rcu_read_lock().
-	 */
-	synchronize_sched();
+	synchronize_rcu();
 
  out:
 	mutex_unlock(&dev->mutex);
@@ -344,7 +343,7 @@ static void __input_release_device(struct input_handle *handle)
 	if (dev->grab == handle) {
 		rcu_assign_pointer(dev->grab, NULL);
 		/* Make sure input_pass_event() notices that grab is gone */
-		synchronize_sched();
+		synchronize_rcu();
 
 		list_for_each_entry(handle, &dev->h_list, d_node)
 			if (handle->open && handle->handler->start)
@@ -404,7 +403,7 @@ int input_open_device(struct input_handle *handle)
 			 * Make sure we are not delivering any more events
 			 * through this handle
 			 */
-			synchronize_sched();
+			synchronize_rcu();
 		}
 	}
 
@@ -451,11 +450,11 @@ void input_close_device(struct input_handle *handle)
 
 	if (!--handle->open) {
 		/*
-		 * synchronize_sched() makes sure that input_pass_event()
+		 * synchronize_rcu() makes sure that input_pass_event()
 		 * completed and that no more input events are delivered
 		 * through this handle
 		 */
-		synchronize_sched();
+		synchronize_rcu();
 	}
 
 	mutex_unlock(&dev->mutex);
@@ -1477,12 +1476,7 @@ int input_register_handle(struct input_handle *handle)
 		return error;
 	list_add_tail_rcu(&handle->d_node, &dev->h_list);
 	mutex_unlock(&dev->mutex);
-	/*
-	 * We don't use synchronize_rcu() here because we rely
-	 * on dev->event_lock to protect read-side critical
-	 * section in input_pass_event().
-	 */
-	synchronize_sched();
+	synchronize_rcu();
 
 	/*
 	 * Since we are supposed to be called from ->connect()
@@ -1521,7 +1515,7 @@ void input_unregister_handle(struct input_handle *handle)
 	mutex_lock(&dev->mutex);
 	list_del_rcu(&handle->d_node);
 	mutex_unlock(&dev->mutex);
-	synchronize_sched();
+	synchronize_rcu();
 }
 EXPORT_SYMBOL(input_unregister_handle);
 

drivers/input/joydev.c

@@ -149,8 +149,10 @@ static void joydev_event(struct input_handle *handle,
 
 	event.time = jiffies_to_msecs(jiffies);
 
+	rcu_read_lock();
 	list_for_each_entry_rcu(client, &joydev->client_list, node)
 		joydev_pass_event(client, &event);
+	rcu_read_unlock();
 
 	wake_up_interruptible(&joydev->wait);
 }
@@ -178,12 +180,7 @@ static void joydev_attach_client(struct joydev *joydev,
 	spin_lock(&joydev->client_lock);
 	list_add_tail_rcu(&client->node, &joydev->client_list);
 	spin_unlock(&joydev->client_lock);
-	/*
-	 * We don't use synchronize_rcu() here because read-side
-	 * critical section is protected by a spinlock (dev->event_lock)
-	 * instead of rcu_read_lock().
-	 */
-	synchronize_sched();
+	synchronize_rcu();
 }
 
 static void joydev_detach_client(struct joydev *joydev,
@@ -192,7 +189,7 @@ static void joydev_detach_client(struct joydev *joydev,
 	spin_lock(&joydev->client_lock);
 	list_del_rcu(&client->node);
 	spin_unlock(&joydev->client_lock);
-	synchronize_sched();
+	synchronize_rcu();
 }
 
 static int joydev_open_device(struct joydev *joydev)

drivers/input/mousedev.c

@@ -265,6 +265,7 @@ static void mousedev_notify_readers(struct mousedev *mousedev,
 	unsigned int new_head;
 	int wake_readers = 0;
 
+	rcu_read_lock();
 	list_for_each_entry_rcu(client, &mousedev->client_list, node) {
 
 		/* Just acquire the lock, interrupts already disabled */
@@ -309,6 +310,7 @@ static void mousedev_notify_readers(struct mousedev *mousedev,
 			wake_readers = 1;
 		}
 	}
+	rcu_read_unlock();
 
 	if (wake_readers)
 		wake_up_interruptible(&mousedev->wait);
@@ -499,12 +501,7 @@ static void mousedev_attach_client(struct mousedev *mousedev,
 	spin_lock(&mousedev->client_lock);
 	list_add_tail_rcu(&client->node, &mousedev->client_list);
 	spin_unlock(&mousedev->client_lock);
-	/*
-	 * We don't use synchronize_rcu() here because read-side
-	 * critical section is protected by a spinlock (dev->event_lock)
-	 * instead of rcu_read_lock().
-	 */
-	synchronize_sched();
+	synchronize_rcu();
 }
 
 static void mousedev_detach_client(struct mousedev *mousedev,
@@ -513,7 +510,7 @@ static void mousedev_detach_client(struct mousedev *mousedev,
 	spin_lock(&mousedev->client_lock);
 	list_del_rcu(&client->node);
 	spin_unlock(&mousedev->client_lock);
-	synchronize_sched();
+	synchronize_rcu();
 }
 
 static int mousedev_release(struct inode *inode, struct file *file)