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Commit 9b61db1a authored by Hans de Goede's avatar Hans de Goede
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drm: gm12u320: Do not take a mutex from a wait_event condition 



I made the condition of the wait_event_timeout call in
gm12u320_fb_update_work a helper which takes a mutex to make sure
that any writes to fb_update.run or fb_update.fb from other CPU cores
are seen before the check is done.

This is not necessary as the wait_event helpers contain the necessary
barriers for this themselves.

More over it is harmfull since by the time the check is done the task
is no longer in the TASK_RUNNING state and calling mutex_lock while not
in task-running is not allowed, leading to this warning when the kernel
is build with some extra locking checks enabled:

[11947.450011] do not call blocking ops when !TASK_RUNNING; state=2 set at
               [<00000000e4306de6>] prepare_to_wait_event+0x61/0x190

This commit fixes this by dropping the helper and simply directly
checking the condition (without unnecessary locking) in the
wait_event_timeout call.

Acked-by: default avatarSam Ravnborg <sam@ravnborg.org>
Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190811143725.5951-1-hdegoede@redhat.com
parent 4abfa2e4

drivers/gpu/drm/tiny/gm12u320.c

+2 −12
Original line number Diff line number Diff line
@@ -342,17 +342,6 @@ static void gm12u320_copy_fb_to_blocks(struct gm12u320_device *gm12u320) 
	mutex_unlock(&gm12u320->fb_update.lock);

}



static int gm12u320_fb_update_ready(struct gm12u320_device *gm12u320)

{

	int ret;



	mutex_lock(&gm12u320->fb_update.lock);

	ret = !gm12u320->fb_update.run || gm12u320->fb_update.fb != NULL;

	mutex_unlock(&gm12u320->fb_update.lock);



	return ret;

}



static void gm12u320_fb_update_work(struct work_struct *work)

{

	struct gm12u320_device *gm12u320 =
@@ -426,7 +415,8 @@ static void gm12u320_fb_update_work(struct work_struct *work) 
		 * switches back to showing its logo.

		 */

		wait_event_timeout(gm12u320->fb_update.waitq,

				   gm12u320_fb_update_ready(gm12u320),

				   !gm12u320->fb_update.run ||

					gm12u320->fb_update.fb != NULL,

				   IDLE_TIMEOUT);

	}

	return;