Re: [Intel-gfx] [PATCH] drm: Disable dynamic debug as broken

[Jani Nikula <jani.nikula@intel.com>]

On Fri, 10 Feb 2023, Jani Nikula <jani.nikula@intel.com> wrote:
> On Tue, 07 Feb 2023, Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
>> On Tue, Feb 07, 2023 at 04:33:37PM +0200, Jani Nikula wrote:
>>> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>>> 
>>> CONFIG_DRM_USE_DYNAMIC_DEBUG breaks debug prints for (at least modular)
>>> drm drivers. The debug prints can be reinstated by manually frobbing
>>> /sys/module/drm/parameters/debug after the fact, but at that point the
>>> damage is done and all debugs from driver probe are lost. This makes
>>> drivers totally undebuggable.
>>> 
>>> There's a more complete fix in progress [1], with further details, but
>>> we need this fixed in stable kernels. Mark the feature as broken and
>>> disable it by default, with hopes distros follow suit and disable it as
>>> well.
>>> 
>>> [1] https://lore.kernel.org/r/20230125203743.564009-1-jim.cromie@gmail.com
>>> 
>>> Fixes: 84ec67288c10 ("drm_print: wrap drm_*_dbg in dyndbg descriptor factory macro")
>>> Cc: Jim Cromie <jim.cromie@gmail.com>
>>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>>> Cc: Maxime Ripard <mripard@kernel.org>
>>> Cc: Thomas Zimmermann <tzimmermann@suse.de>
>>> Cc: David Airlie <airlied@gmail.com>
>>> Cc: Daniel Vetter <daniel@ffwll.ch>
>>> Cc: dri-devel@lists.freedesktop.org
>>> Cc: <stable@vger.kernel.org> # v6.1+
>>> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
>>> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>>> ---
>>>  drivers/gpu/drm/Kconfig | 3 ++-
>>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>> 
>>> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
>>> index f42d4c6a19f2..dc0f94f02a82 100644
>>> --- a/drivers/gpu/drm/Kconfig
>>> +++ b/drivers/gpu/drm/Kconfig
>>> @@ -52,7 +52,8 @@ config DRM_DEBUG_MM
>>>  
>>>  config DRM_USE_DYNAMIC_DEBUG
>>>  	bool "use dynamic debug to implement drm.debug"
>>> -	default y
>>> +	default n
>>> +	depends on BROKEN
>>>  	depends on DRM
>>>  	depends on DYNAMIC_DEBUG || DYNAMIC_DEBUG_CORE
>>>  	depends on JUMP_LABEL
>>
>> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
> Thanks Greg, any more acks from anyone?
>
> Maxime, since there's going to be an -rc8, I suggest taking this via
> drm-misc-fixes. Is that okay with you? (You're doing drm-misc-fixes this
> round, right?)

Pushed to drm-misc-fixes with Maxime's IRC ack and Jim's ack elsewhere
in the thread. Thanks.

BR,
Jani.


>
> BR,
> Jani.

-- 
Jani Nikula, Intel Open Source Graphics Center