Lock the bare minimum, instead of the entire world, and
use interruptible locking because we can.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171110113503.16253-6-maarten.lankhorst@linux.intel.comReviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>