[PATCH] drm/panic: depends on !VT_CONSOLE

[Javier Martinez Canillas]

Jocelyn Falempe <jfalempe at redhat.com> writes:

Hello Jocelyn,

> The race condition between fbcon and drm_panic can only occurs if
> VT_CONSOLE is set. So update drm_panic dependency accordingly.
> This will make it easier for Linux distributions to enable drm_panic
> by disabling VT_CONSOLE, and keeping fbcon terminal.
> The only drawback is that fbcon won't display the boot kmsg, so it
> should rely on userspace to do that.
> At least plymouth already handle this case with
> https://gitlab.freedesktop.org/plymouth/plymouth/-/merge_requests/224
>
> Suggested-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> Signed-off-by: Jocelyn Falempe <jfalempe at redhat.com>
> ---
>  drivers/gpu/drm/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index a9df94291622..f5c989aed7e9 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -107,7 +107,7 @@ config DRM_KMS_HELPER
>  
>  config DRM_PANIC
>  	bool "Display a user-friendly message when a kernel panic occurs"
> -	depends on DRM && !FRAMEBUFFER_CONSOLE
> +	depends on DRM && !(FRAMEBUFFER_CONSOLE && VT_CONSOLE)

I thought the idea was to only make it depend on !VT_CONSOLE, so that
distros could also enable fbcon / VT but prevent the race condition to
happen due the VT not being a system console for the kernel to print
messages ?

In other words, my understanding from the discussion with Sima was that
this should be instead:

 +	depends on DRM && !VT_CONSOLE

I've tested that and at least I see that a framebuffer console is present
and `echo c > /proc/sysrq-trigger` triggers the DRM panic handler message
(but don't know if the race exists and is just that I was not hitting it).

If my understanding is correct and should only be a depends on !VT_CONSOLE
then feel free to add my:

Tested-by: Javier Martinez Canillas <javierm at redhat.com>

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat