drm/ttm: Warn on pinning without holding a reference

Not technically a problem for ttm, but very likely a driver bug and
pretty big time confusing for reviewing code.

So warn about it, both at cleanup time (so we catch these for sure)
and at pin/unpin time (so we know who's the culprit).

Reviewed-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Christian Koenig <christian.koenig@amd.com>
Cc: Huang Rui <ray.huang@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201028113120.3641237-1-daniel.vetter@ffwll.ch

1 files changed, 2 insertions, 0 deletions

diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
index 2564e66e67d7..79b9367e0ffd 100644
--- a/include/drm/ttm/ttm_bo_api.h
+++ b/include/drm/ttm/ttm_bo_api.h
@@ -600,6 +600,7 @@ static inline bool ttm_bo_uses_embedded_gem_object(struct ttm_buffer_object *bo)
 static inline void ttm_bo_pin(struct ttm_buffer_object *bo)
 {
 	dma_resv_assert_held(bo->base.resv);
+	WARN_ON_ONCE(!kref_read(&bo->kref));
 	++bo->pin_count;
 }
 
@@ -613,6 +614,7 @@ 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;
 }