Re: [PATCH] drm: Disable dynamic debug as broken

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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>