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>

4 files changed, 56 insertions, 65 deletions

diff --git a/drivers/hwmon/ams/ams-core.c b/drivers/hwmon/ams/ams-core.c
index fbefa82a015..9b4a0e7a564 100644
--- a/drivers/hwmon/ams/ams-core.c
+++ b/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");
diff --git a/drivers/hwmon/ams/ams-i2c.c b/drivers/hwmon/ams/ams-i2c.c
index da26de01068..2cbf8a6506c 100644
--- a/drivers/hwmon/ams/ams-i2c.c
+++ b/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;
 }
diff --git a/drivers/hwmon/ams/ams-input.c b/drivers/hwmon/ams/ams-input.c
index 48dbf7d6a66..8a712392cd3 100644
--- a/drivers/hwmon/ams/ams-input.c
+++ b/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);
 }
diff --git a/drivers/hwmon/ams/ams-pmu.c b/drivers/hwmon/ams/ams-pmu.c
index 9463e9768f6..fb18b3d3162 100644
--- a/drivers/hwmon/ams/ams-pmu.c
+++ b/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;
 }