[Intel-gfx] [PATCH 1/2] drm/i915: Fix locking in DRRS flush/invalidate hooks

[Chris Wilson]

On Thu, Apr 09, 2015 at 04:44:15PM +0200, Daniel Vetter wrote:
> We must acquire the mutex before we can check drrs.dp, otherwise
> someone might sneak in with a modeset, clear the pointer after we've
> checked it and then the code will Oops.
> 
> This issue has been introduced in
> 
> commit a93fad0f7fb8a3ff12e8814b630648f6d187954c
> Author: Vandana Kannan <vandana.kannan at intel.com>
> Date:   Sat Jan 10 02:25:59 2015 +0530
> 
>     drm/i915: DRRS calls based on frontbuffer
> 
> v2: Don't blow up on uninitialized mutex and work item by checking
> whether DRRS is support or not first. Also unconditionally initialize
> the mutex/work item to avoid future trouble.
> 
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Cc: Ramalingam C <ramalingam.c at intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> Cc: Vandana Kannan <vandana.kannan at intel.com>
> Cc: stable at vger.kernel.org (4.0+ only)
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>

Happier,
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
Tested-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre