On Wed, Oct 28, 2020 at 07:31:20PM +0800, Daniel Vetter wrote:
> 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).
>
> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
Reviewed-by: Huang Rui <ray.huang@xxxxxxx>
> Cc: Christian Koenig <christian.koenig@xxxxxxx>
> Cc: Huang Rui <ray.huang@xxxxxxx>
> ---
> drivers/gpu/drm/ttm/ttm_bo.c | 2 +-
> include/drm/ttm/ttm_bo_api.h | 2 ++
> 2 files changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index f51b5e20fa17..a011072ab61d 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -509,7 +509,7 @@ static void ttm_bo_release(struct kref *kref)
> * shrinkers, now that they are queued for
> * destruction.
> */
> - if (bo->pin_count) {
> + if (WARN_ON(bo->pin_count)) {
> bo->pin_count = 0;
> ttm_bo_del_from_lru(bo);
> ttm_bo_add_mem_to_lru(bo, &bo->mem);
> diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
> index 37102e45e496..b45aee23d7d0 100644
> --- a/include/drm/ttm/ttm_bo_api.h
> +++ b/include/drm/ttm/ttm_bo_api.h
> @@ -571,6 +571,7 @@ 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;
> }
>
> @@ -584,6 +585,7 @@ 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;
> }
>
> --
> 2.28.0
>
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