Hi,
On 04-01-16 23:22, Adrien Schildknecht wrote:
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@xxxxxxxxxxx>
Thanks for the fix, my first instinct was that there should be an easier
fix, but thinking more about it this and how this function is used
in thinkpad_acpi. this is indeed the correct way to fix this:
Reviewed-by: Hans de Goede <hdegoede@xxxxxxxxxx>
Rafael, can you please add this fix to acpi-next ?
Regards,
Hans
---
drivers/acpi/acpi_video.c | 27 ++++++++++++++-------------
1 file changed, 14 insertions(+), 13 deletions(-)
diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c
index 80b13d4..06a006f 100644
--- a/drivers/acpi/acpi_video.c
+++ b/drivers/acpi/acpi_video.c
@@ -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(®ister_count_mutex);
- if (register_count) {
+ mutex_lock(®ister_done_mutex);
+ if (completion_done(®ister_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(®ister_done);
leave:
- mutex_unlock(®ister_count_mutex);
+ mutex_unlock(®ister_done_mutex);
return ret;
}
EXPORT_SYMBOL(acpi_video_register);
void acpi_video_unregister(void)
{
- mutex_lock(®ister_count_mutex);
- if (register_count) {
+ mutex_lock(®ister_done_mutex);
+ if (completion_done(®ister_done)) {
acpi_bus_unregister_driver(&acpi_video_bus);
- register_count = 0;
+ reinit_completion(®ister_done);
}
- mutex_unlock(®ister_count_mutex);
+ mutex_unlock(®ister_done_mutex);
}
EXPORT_SYMBOL(acpi_video_unregister);
@@ -2094,20 +2094,21 @@ void acpi_video_unregister_backlight(void)
{
struct acpi_video_bus *video;
- mutex_lock(®ister_count_mutex);
- if (register_count) {
+ mutex_lock(®ister_done_mutex);
+ if (completion_done(®ister_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(®ister_count_mutex);
+ mutex_unlock(®ister_done_mutex);
}
bool acpi_video_handles_brightness_key_presses(void)
{
bool have_video_busses;
+ wait_for_completion(®ister_done);
mutex_lock(&video_list_lock);
have_video_busses = !list_empty(&video_bus_head);
mutex_unlock(&video_list_lock);
--
To unsubscribe from this list: send the line "unsubscribe linux-acpi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
