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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: Adrien Schildknecht <adrien+dev@schischi.me>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Adrien Schildknecht 2016-01-04 23:22:28 +01:00 committed by Rafael J. Wysocki
parent 49eb520822
commit aecbd9b1bf
1 changed files with 14 additions and 13 deletions
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27
drivers/acpi/acpi_video.c
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@ -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);