hwmon: (ams) Fix locking issues

Use a separate mutex to serialize input device creation/removal,
otheriwse we deadlock if we try to remove input device while it is
being polled. Also do not take ams_info.lock when it is not needed.
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

drivers/hwmon/ams/ams-core.c

@@ -223,34 +223,28 @@ int __init ams_init(void)
 
 void ams_exit(void)
 {
-	mutex_lock(&ams_info.lock);
-
-	if (ams_info.has_device) {
-		/* Remove input device */
-		ams_input_exit();
+	/* Remove input device */
+	ams_input_exit();
 
-		/* Shut down implementation */
-		ams_info.exit();
-
-		/* Flush interrupt worker
-		 *
-		 * We do this after ams_info.exit(), because an interrupt might
-		 * have arrived before disabling them.
-		 */
-		flush_scheduled_work();
+	/* Remove attributes */
+	device_remove_file(&ams_info.of_dev->dev, &dev_attr_current);
 
-		/* Remove attributes */
-		device_remove_file(&ams_info.of_dev->dev, &dev_attr_current);
+	/* Shut down implementation */
+	ams_info.exit();
 
-		/* Remove device */
-		of_device_unregister(ams_info.of_dev);
+	/* Flush interrupt worker
+	 *
+	 * We do this after ams_info.exit(), because an interrupt might
+	 * have arrived before disabling them.
+	 */
+	flush_scheduled_work();
 
-		/* Remove handler */
-		pmf_unregister_irq_client(&ams_shock_client);
-		pmf_unregister_irq_client(&ams_freefall_client);
-	}
+	/* Remove device */
+	of_device_unregister(ams_info.of_dev);
 
-	mutex_unlock(&ams_info.lock);
+	/* Remove handler */
+	pmf_unregister_irq_client(&ams_shock_client);
+	pmf_unregister_irq_client(&ams_freefall_client);
 }
 
 MODULE_AUTHOR("Stelian Pop, Michael Hanselmann");

drivers/hwmon/ams/ams-i2c.c

@@ -261,8 +261,6 @@ int __init ams_i2c_init(struct device_node *np)
 {
 	int result;
 
-	mutex_lock(&ams_info.lock);
-
 	/* Set implementation stuff */
 	ams_info.of_node = np;
 	ams_info.exit = ams_i2c_exit;
@@ -273,7 +271,5 @@ int __init ams_i2c_init(struct device_node *np)
 
 	result = i2c_add_driver(&ams_i2c_driver);
 
-	mutex_unlock(&ams_info.lock);
-
 	return result;
 }

drivers/hwmon/ams/ams-input.c

@@ -27,6 +27,8 @@ static unsigned int invert;
 module_param(invert, bool, S_IWUSR | S_IRUGO);
 MODULE_PARM_DESC(invert, "Invert input data on X and Y axis");
 
+static DEFINE_MUTEX(ams_input_mutex);
+
 static void ams_idev_poll(struct input_polled_dev *dev)
 {
 	struct input_dev *idev = dev->input;
@@ -50,13 +52,11 @@ static void ams_idev_poll(struct input_polled_dev *dev)
 }
 
 /* Call with ams_info.lock held! */
-static void ams_input_enable(void)
+static int ams_input_enable(void)
 {
 	struct input_dev *input;
 	s8 x, y, z;
-
-	if (ams_info.idev)
-		return;
+	int error;
 
 	ams_sensors(&x, &y, &z);
 	ams_info.xcalib = x;
@@ -65,7 +65,7 @@ static void ams_input_enable(void)
 
 	ams_info.idev = input_allocate_polled_device();
 	if (!ams_info.idev)
-		return;
+		return -ENOMEM;
 
 	ams_info.idev->poll = ams_idev_poll;
 	ams_info.idev->poll_interval = 25;
@@ -84,14 +84,18 @@ static void ams_input_enable(void)
 	set_bit(EV_KEY, input->evbit);
 	set_bit(BTN_TOUCH, input->keybit);
 
-	if (input_register_polled_device(ams_info.idev)) {
+	error = input_register_polled_device(ams_info.idev);
+	if (error) {
 		input_free_polled_device(ams_info.idev);
 		ams_info.idev = NULL;
-		return;
+		return error;
 	}
+
+	joystick = 1;
+
+	return 0;
 }
 
-/* Call with ams_info.lock held! */
 static void ams_input_disable(void)
 {
 	if (ams_info.idev) {
@@ -99,6 +103,8 @@ static void ams_input_disable(void)
 		input_free_polled_device(ams_info.idev);
 		ams_info.idev = NULL;
 	}
+
+	joystick = 0;
 }
 
 static ssize_t ams_input_show_joystick(struct device *dev,
@@ -110,39 +116,42 @@ static ssize_t ams_input_show_joystick(struct device *dev,
 static ssize_t ams_input_store_joystick(struct device *dev,
 	struct device_attribute *attr, const char *buf, size_t count)
 {
-	if (sscanf(buf, "%d\n", &joystick) != 1)
+	unsigned long enable;
+	int error = 0;
+
+	if (strict_strtoul(buf, 0, &enable) || enable > 1)
 		return -EINVAL;
 
-	mutex_lock(&ams_info.lock);
+	mutex_lock(&ams_input_mutex);
 
-	if (joystick)
-		ams_input_enable();
-	else
-		ams_input_disable();
+	if (enable != joystick) {
+		if (enable)
+			error = ams_input_enable();
+		else
+			ams_input_disable();
+	}
 
-	mutex_unlock(&ams_info.lock);
+	mutex_unlock(&ams_input_mutex);
 
-	return count;
+	return error ? error : count;
 }
 
 static DEVICE_ATTR(joystick, S_IRUGO | S_IWUSR,
 	ams_input_show_joystick, ams_input_store_joystick);
 
-/* Call with ams_info.lock held! */
 int ams_input_init(void)
 {
-	int result;
-
-	result = device_create_file(&ams_info.of_dev->dev, &dev_attr_joystick);
-
-	if (!result && joystick)
+	if (joystick)
 		ams_input_enable();
-	return result;
+
+	return device_create_file(&ams_info.of_dev->dev, &dev_attr_joystick);
 }
 
-/* Call with ams_info.lock held! */
 void ams_input_exit(void)
 {
-	ams_input_disable();
 	device_remove_file(&ams_info.of_dev->dev, &dev_attr_joystick);
+
+	mutex_lock(&ams_input_mutex);
+	ams_input_disable();
+	mutex_unlock(&ams_input_mutex);
 }

drivers/hwmon/ams/ams-pmu.c

@@ -149,8 +149,6 @@ int __init ams_pmu_init(struct device_node *np)
 	const u32 *prop;
 	int result;
 
-	mutex_lock(&ams_info.lock);
-
 	/* Set implementation stuff */
 	ams_info.of_node = np;
 	ams_info.exit = ams_pmu_exit;
@@ -161,10 +159,9 @@ int __init ams_pmu_init(struct device_node *np)
 
 	/* Get PMU command, should be 0x4e, but we can never know */
 	prop = of_get_property(ams_info.of_node, "reg", NULL);
-	if (!prop) {
-		result = -ENODEV;
-		goto exit;
-	}
+	if (!prop)
+		return -ENODEV;
+
 	ams_pmu_cmd = ((*prop) >> 8) & 0xff;
 
 	/* Disable interrupts */
@@ -175,7 +172,7 @@ int __init ams_pmu_init(struct device_node *np)
 
 	result = ams_sensor_attach();
 	if (result < 0)
-		goto exit;
+		return result;
 
 	/* Set default values */
 	ams_pmu_set_register(AMS_FF_LOW_LIMIT, 0x15);
@@ -198,10 +195,5 @@ int __init ams_pmu_init(struct device_node *np)
 
 	printk(KERN_INFO "ams: Found PMU based motion sensor\n");
 
-	result = 0;
-
-exit:
-	mutex_unlock(&ams_info.lock);
-
-	return result;
+	return 0;
 }