[PATCH 5/5] drm: Nerf drm_global_mutex BKL for good drivers

[Chris Wilson]

Quoting Daniel Vetter (2020-02-04 15:01:46)
> This catches the majority of drivers (unfortunately not if we take
> users into account, because all the big drivers have at least a
> lastclose hook).
> 
> With the prep patches out of the way all drm state is fully protected
> and either prevents or can deal with the races from dropping the BKL
> around open/close. The only thing left to audit are the various driver
> hooks - by keeping the BKL around if any of them are set we have a
> very simple cop-out!
> 
> Note that one of the biggest prep pieces to get here was making
> dev->open_count atomic, which was done in
> 
> commit 7e13ad896484a0165a68197a2e64091ea28c9602
> Author: Chris Wilson <chris at chris-wilson.co.uk>
> Date:   Fri Jan 24 13:01:07 2020 +0000
> 
>     drm: Avoid drm_global_mutex for simple inc/dec of dev->open_count
> 
> v2:
> - Rebase and fix locking in drm_open() (Chris)
> - Indentation fix in drm_release
> - Typo fix in the commit message (Sam)
> 
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Sam Ravnborg <sam at ravnborg.org>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris