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Commit aecbd9b1 authored by Adrien Schildknecht's avatar Adrien Schildknecht Committed by Rafael J. Wysocki
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ACPI / video: driver must be registered before checking for keypresses 



acpi_video_handles_brightness_key_presses() may use an uninitialized mutex.
The error has been reported by lockdep: DEBUG_LOCKS_WARN_ON(l->magic != l).
The function assumes that the video driver has been registered before being
called. As explained in the comment of acpi_video_init(), the registration
of the video class may be defered and thus may not take place in the init
function of the module.

Use completion mechanisms to make sure that
acpi_video_handles_brightness_key_presses() wait for the completion of
acpi_video_register() before using the mutex.
Also get rid of register_count since task completion can replace it.

Signed-off-by: default avatarAdrien Schildknecht <adrien+dev@schischi.me>
Reviewed-by: default avatarHans de Goede <hdegoede@redhat.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 49eb5208

drivers/acpi/acpi_video.c

+14 −13
Original line number Diff line number Diff line
@@ -90,8 +90,8 @@ module_param(device_id_scheme, bool, 0444); 
static bool only_lcd = false;

module_param(only_lcd, bool, 0444);



static int register_count;

static DEFINE_MUTEX(register_count_mutex);

static DECLARE_COMPLETION(register_done);

static DEFINE_MUTEX(register_done_mutex);

static struct mutex video_list_lock;

static struct list_head video_bus_head;

static int acpi_video_bus_add(struct acpi_device *device);
@@ -2049,8 +2049,8 @@ int acpi_video_register(void) 
{

	int ret = 0;



	mutex_lock(&register_count_mutex);

	if (register_count) {

	mutex_lock(&register_done_mutex);

	if (completion_done(&register_done)) {

		/*

		 * if the function of acpi_video_register is already called,

		 * don't register the acpi_vide_bus again and return no error.
@@ -2071,22 +2071,22 @@ int acpi_video_register(void) 
	 * When the acpi_video_bus is loaded successfully, increase

	 * the counter reference.

	 */

	register_count = 1;

	complete(&register_done);



leave:

	mutex_unlock(&register_count_mutex);

	mutex_unlock(&register_done_mutex);

	return ret;

}

EXPORT_SYMBOL(acpi_video_register);



void acpi_video_unregister(void)

{

	mutex_lock(&register_count_mutex);

	if (register_count) {

	mutex_lock(&register_done_mutex);

	if (completion_done(&register_done)) {

		acpi_bus_unregister_driver(&acpi_video_bus);

		register_count = 0;

		reinit_completion(&register_done);

	}

	mutex_unlock(&register_count_mutex);

	mutex_unlock(&register_done_mutex);

}

EXPORT_SYMBOL(acpi_video_unregister);
@@ -2094,20 +2094,21 @@ void acpi_video_unregister_backlight(void) 
{

	struct acpi_video_bus *video;



	mutex_lock(&register_count_mutex);

	if (register_count) {

	mutex_lock(&register_done_mutex);

	if (completion_done(&register_done)) {

		mutex_lock(&video_list_lock);

		list_for_each_entry(video, &video_bus_head, entry)

			acpi_video_bus_unregister_backlight(video);

		mutex_unlock(&video_list_lock);

	}

	mutex_unlock(&register_count_mutex);

	mutex_unlock(&register_done_mutex);

}



bool acpi_video_handles_brightness_key_presses(void)

{

	bool have_video_busses;



	wait_for_completion(&register_done);

	mutex_lock(&video_list_lock);

	have_video_busses = !list_empty(&video_bus_head);

	mutex_unlock(&video_list_lock);