drm/i915: Fix locking in DRRS flush/invalidate hooks

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 <[email protected]>
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 <[email protected]>
Cc: Ville Syrjälä <[email protected]>
Cc: Ramalingam C <[email protected]>
Cc: Rodrigo Vivi <[email protected]>
Cc: Vandana Kannan <[email protected]>
Cc: [email protected] (4.0+ only)
Reviewed-by: Chris Wilson <[email protected]>
Tested-by: Chris Wilson <[email protected]>
Signed-off-by: Daniel Vetter <[email protected]>
Signed-off-by: Jani Nikula <[email protected]>

0 files changed, 0 insertions, 0 deletions