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drm: gm12u320: Do not take a mutex from a wait_event condition

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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: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190811143725.5951-1-hdegoede@redhat.com
This commit is contained in:
Hans de Goede 2019-08-11 16:37:24 +02:00
parent 4abfa2e4e7
commit 9b61db1aed
1 changed files with 2 additions and 12 deletions
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14
drivers/gpu/drm/tiny/gm12u320.c
View File

@ -342,17 +342,6 @@ unlock:
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;