WARNING: CPU: 2 PID: 42 at drivers/gpu/drm/drm_modeset_lock.c:276

[Maíra Canal]

On 12/29/22 05:37, Maxime Ripard wrote:
> On Wed, Dec 28, 2022 at 11:16:11PM +0100, Stefan Wahren wrote:
>> Hi Maíra,
>>
>> Am 28.12.22 um 20:49 schrieb Maíra Canal:
>>> Hi Stefan,
>>>
>>> I was able to reproduce this error on drm-misc-next. I bisected,
>>> and I got into commit 6bed2ea3cb38. I noticed that the crtc->mutex is
>>> being locked twice, and this might be causing the problem. I wrote a
>>> patch to try to fix this issue, and after applying the patch, I wasn't
>>> able to reproduce the error anymore.
>>>
>>> Let me know if you were able to reproduce the warning after applying
>>> this patch.
>>
>> the patch works as expected and avoid the warning. I tested it on top of
>> v6.1 with RPi 3 B+ and RPi 4 B.
>>
>> In case you send the patch please add the Fixes tag so the patch get
>> backported to stable.
> 
> This isn't a proper fix, we do need to take the crtc mutex: it protects
> the crtc->state pointer we dereference next, and vc4_hdmi_reset_link can
> be called outside of a modeset through the interrupt handler.

Do you suggest calling drm_modeset_unlock after dereferencing crtc->state?

Best Regards,
- Maíra Canal

> 
> Maxime