[Intel-gfx] [PATCH 1/2] drm/crtc-helper: fix locking for drm_helper_disable_unused_functions

[Chris Wilson]

On Thu, Mar 20, 2014 at 02:26:34PM +0100, Daniel Vetter wrote:
> We have two calling contexts for thise function:
> 
> - In the crtc helper code itself as part of the ->set_config
>   implementation. In this calling context all modeset locks are
>   already held, as they should.
> 
> - In drivers not implementing fastboot before the fbdev/fbcon setup
>   and initialization. This has been added for all drivers in
> 
>   commit 76a39dbfb2d1bc45219839e5a95d4ceaf6ca114f
>   Author: Daniel Vetter <daniel.vetter at ffwll.ch>
>   Date:   Sun Jan 20 23:12:54 2013 +0100
> 
>       drm/fb-helper: don't disable everything in initial_config
> 
>   In this calling context we do not hold any modeset locks since the
>   immediately following call to initialize the fbev emulation grabs
>   all these locks themselves.
> 
> - There are two exceptions to the above rule: shmob doesn't have fbdev
>   emulation support. I've manually checked the callchain up to the
>   driver load function and no kms locks are held.
> 
> The right fix therefore is to split this helper into an internal and
> external version and add the required locking to the function exported
> to drivers.
> 
> This remedies locking inconsistencies exposed by me adding locking
> WARNs as part of the recent kerneldoc abi polishing done in
> 
> commit 62ff94a5492175759546f8bc61383189d6b49122
> Author: Daniel Vetter <daniel.vetter at ffwll.ch>
> Date:   Thu Jan 23 22:18:47 2014 +0100
> 
>     drm/crtc-helper: remove LOCKING from kerneldoc
> 
> and
> 
> commit 63951385052f7974155fa38f962f0f4e9847f90a
> Author: Daniel Vetter <daniel.vetter at ffwll.ch>
> Date:   Thu Jan 23 15:14:15 2014 +0100
> 
>     drm/doc: Repleace LOCKING kerneldoc sections in drm_modes.c
> 
> v2: It helps when I actually git add the entire thing.
> 
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre