[Intel-gfx] [PATCH 08/35] drm: Protect dev->filelist with its own mutex

[Chris Wilson]

On Tue, Apr 26, 2016 at 07:29:41PM +0200, Daniel Vetter wrote:
> amdgpu gained dev->struct_mutex usage, and that's because it's walking
> the dev->filelist list. Protect that list with it's own lock to take
> one more step towards getting rid of struct_mutex usage in drivers
> once and for all.
> 
> While doing the conversion I noticed that 2 debugfs files in i915
> completely lacked appropriate locking. Fix that up too.
> 
> v2: don't forget to switch to drm_gem_object_unreference_unlocked.
> 
> Cc: Alex Deucher <alexander.deucher at amd.com>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>

Just wondering if this worth converting over. Opening/closing isn't
going to be high contention, I hope, though we can certainly write
stress cases for it! The goal for drivers to stop using the struct_mutex
as their BKL, which doesn't preclude keeping the struct_mutex around for
where it makes sense to have a single mutex rather than a multitude.

I have some misgivings over this, but only because I think its overkill.
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre