[PATCH] drm/ttm: make ttm_bo_unpin more defensive

[Christian König]

We seem to have some more driver bugs than thought.

Signed-off-by: Christian König <christian.koenig at amd.com>
---
 include/drm/ttm/ttm_bo_api.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
index 4fb523dfab32..df9fe596e7c5 100644
--- a/include/drm/ttm/ttm_bo_api.h
+++ b/include/drm/ttm/ttm_bo_api.h
@@ -603,9 +603,11 @@ static inline void ttm_bo_pin(struct ttm_buffer_object *bo)
 static inline void ttm_bo_unpin(struct ttm_buffer_object *bo)
 {
 	dma_resv_assert_held(bo->base.resv);
-	WARN_ON_ONCE(!bo->pin_count);
 	WARN_ON_ONCE(!kref_read(&bo->kref));
-	--bo->pin_count;
+	if (bo->pin_count)
+		--bo->pin_count;
+	else
+		WARN_ON_ONCE(true);
 }
 
 int ttm_mem_evict_first(struct ttm_device *bdev,
-- 
2.25.1