Hi, Christian
On 3/12/21 10:38 AM, Christian König wrote:
We seem to have some more driver bugs than thought.
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
---
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,
Since I now have been staring for half a year at the code of the driver
that made pinning an art, I have a couple of suggestions here, Could we
use an atomic for pin_count, allowing unlocked unpinning but require the
lock only for pin_count transition 0->1, (but unlocked for
pin_if_already_pinned). In particular I think vmwgfx would benefit from
unlocked unpins. Also if the atomic were a refcount_t, that would
probably give you the above behaviour?
/Thomas
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