[PATCH v4 06/11] drm/fb-helper: Make top-level lock more robust

[Thierry Reding]

On Wed, Mar 29, 2017 at 04:43:56PM +0200, Thierry Reding wrote:
> From: Thierry Reding <treding at nvidia.com>
> 
> The existing drm_fb_helper_hotplug_event() function needs to take the
> top-level fb-helper lock. However, the function can also be called from
> code that has already taken this lock. Introduce an unlocked variant of
> this function that can be used in the latter case.
> 
> This function calls drm_fb_helper_restore_fbdev_mode_unlocked(), via
> drm_fb_helper_set_par(), so we also need to introduce an unlocked copy
> of that to avoid recursive locking issues.
> 
> Similarly, the drm_fb_helper_initial_config() function ends up calling
> drm_fb_helper_set_par(), via register_framebuffer(), and needs an
> unlocked variant to avoid recursive locking.
> 
> Signed-off-by: Thierry Reding <treding at nvidia.com>
> ---
>  drivers/gpu/drm/drm_fb_helper.c | 167 +++++++++++++++++++++++++---------------
>  1 file changed, 104 insertions(+), 63 deletions(-)

Note that this could probably be squashed into 05/11, but I left it
separate for easier review since it's the only new patch in the series.

Also I had originally split this into three separate patches, but the
recursive call stack for the drm_fb_helper_hotplug_event() function and
drm_fb_helper_restore_fbdev_mode_unlocked() made it impossible to keep
bisectibility across the series.

Thierry
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