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Message-ID: <Y3XUrOGAV4I7bB3M@kroah.com>
Date: Thu, 17 Nov 2022 07:29:00 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: Jim Cromie <jim.cromie@...il.com>
Cc: jbaron@...mai.com, dri-devel@...ts.freedesktop.org,
amd-gfx@...ts.freedesktop.org, intel-gvt-dev@...ts.freedesktop.org,
intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
daniel.vetter@...ll.ch, seanpaul@...omium.org, robdclark@...il.com,
linux@...musvillemoes.dk, joe@...ches.com
Subject: Re: [PATCH 1/7] drm: mark drm.debug-on-dyndbg as BROKEN for now
On Fri, Nov 11, 2022 at 03:17:09PM -0700, Jim Cromie wrote:
> drm.debug-on-dyndbg has a regression, due to a chicken-egg
> initialization problem:
>
> 1- modprobe i915
> i915 needs drm.ko, which is loaded 1st
>
> 2- "modprobe drm drm.debug=0x1ff" (virtual/implied)
> drm.debug is set post-initialization, from boot-args etc
>
> 3- `modprobe i915` finishes
>
> W/O drm.debug-on-dyndbg that just works, because all drm_dbg*
> callsites use drm_debug_enabled() to check __drm_debug & DEM_UT_<CAT>
> before printing.
>
> But the whole point of drm.debug-on-dyndbg is to avoid that runtime
> test, by enabling (at post-modinit) a static-key at each callsite in
> the just-loaded module.
>
> And since drm.ko is loaded before all dependent modules, none are
> "just-loaded", and no drm.debug callsites are present yet, except
> those in drm.ko itself.
>
> Signed-off-by: Jim Cromie <jim.cromie@...il.com>
> ---
> drivers/gpu/drm/Kconfig | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index 34f5a092c99e..0d1e59e6bb7e 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -54,6 +54,7 @@ config DRM_DEBUG_MM
> config DRM_USE_DYNAMIC_DEBUG
> bool "use dynamic debug to implement drm.debug"
> default y
> + depends on BROKEN # chicken-egg initial enable problem
> depends on DRM
> depends on DYNAMIC_DEBUG || DYNAMIC_DEBUG_CORE
> depends on JUMP_LABEL
> --
> 2.38.1
This should go through the drm tree now. The rest probably should also
go that way and not through my tree as well.
thanks,
greg k-h
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