drm/i915/selftests: Hold rpm for unparking

The call to i915_gem_unpark() checks that we hold a rpm wakeref before
taking a long term wakeref for i915->gt.awake. We should therefore make
sure we do hold the wakeref when directly calling unpark to disable
the retire worker.

Fixes: 932cac1 ("drm/i915/selftests: Prevent background reaping of active objects")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180809063449.4474-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/selftests/i915_gem_object.c

@@ -499,6 +499,19 @@ static bool assert_mmap_offset(struct drm_i915_private *i915,
 	return err == expected;
 }
 
+static void disable_retire_worker(struct drm_i915_private *i915)
+{
+	mutex_lock(&i915->drm.struct_mutex);
+	if (!i915->gt.active_requests++) {
+		intel_runtime_pm_get(i915);
+		i915_gem_unpark(i915);
+		intel_runtime_pm_put(i915);
+	}
+	mutex_unlock(&i915->drm.struct_mutex);
+	cancel_delayed_work_sync(&i915->gt.retire_work);
+	cancel_delayed_work_sync(&i915->gt.idle_work);
+}
+
 static int igt_mmap_offset_exhaustion(void *arg)
 {
 	struct drm_i915_private *i915 = arg;
@@ -509,12 +522,7 @@ static int igt_mmap_offset_exhaustion(void *arg)
 	int loop, err;
 
 	/* Disable background reaper */
-	mutex_lock(&i915->drm.struct_mutex);
-	if (!i915->gt.active_requests++)
-		i915_gem_unpark(i915);
-	mutex_unlock(&i915->drm.struct_mutex);
-	cancel_delayed_work_sync(&i915->gt.retire_work);
-	cancel_delayed_work_sync(&i915->gt.idle_work);
+	disable_retire_worker(i915);
 	GEM_BUG_ON(!i915->gt.awake);
 
 	/* Trim the device mmap space to only a page */