drm/i915: Catch premature unpinning of pages

Try to catch the violation of unpinning the backing storage whilst still
bound to the GPU.

Signed-off-by: Chris Wilson <[e-mail]>
Link: http://patchwork.freedesktop.org/patch/msgid/[e-mail]
Reviewed-by: Joonas Lahtinen <[e-mail]>

drivers/gpu/drm/i915/i915_drv.h

···
 
 static inline void i915_gem_object_pin_pages(struct drm_i915_gem_object *obj)
 {
-	BUG_ON(obj->pages == NULL);
+	GEM_BUG_ON(obj->pages == NULL);
 	obj->pages_pin_count++;
 }
 
 static inline void i915_gem_object_unpin_pages(struct drm_i915_gem_object *obj)
 {
-	BUG_ON(obj->pages_pin_count == 0);
+	GEM_BUG_ON(obj->pages_pin_count == 0);
 	obj->pages_pin_count--;
+	GEM_BUG_ON(obj->pages_pin_count < obj->bind_count);
 }
 
 enum i915_map_type {