drm/i915: Park the signaler before sleeping

drm/i915: Park the signaler before sleeping

If the signal to park arrives before we sleep, then we need to check
kthread_should_park() before sleeping to avoid missing the signal.
Otherwise, if the signal arrives whilst we are processing completed
requests, we will reset the current->state back to TASK_INTERRUPTIBLE
and so miss the wakeup.

Fixes: fe3288b5da2c ("drm/i915: Park the breadcrumbs signaler across a GPU reset")
Signed-off-by: Chris Wilson <[email protected]>
Cc: Mika Kuoppala <[email protected]>
Cc: Tvrtko Ursulin <[email protected]>
Link: http://patchwork.freedesktop.org/patch/msgid/[email protected]
Reviewed-by: Tvrtko Ursulin <[email protected]>