dma-buf: add a warning when drv try to reserve 0 fence slots
Commit Message
When dma_resv_reserve_fences() is called with num_fences=0 it usually
means that a driver or other component messed up its calculation how
many fences are needed. Warn in that situation.
When no fence are needed the function shouldn't be called in the first
place.
Signed-off-by: Christian König <christian.koenig@amd.com>
---
drivers/dma-buf/dma-resv.c | 7 +++++++
1 file changed, 7 insertions(+)
Comments
On 29/05/2024 09:43, Christian König wrote:
> When dma_resv_reserve_fences() is called with num_fences=0 it usually
> means that a driver or other component messed up its calculation how
> many fences are needed. Warn in that situation.
>
> When no fence are needed the function shouldn't be called in the first
> place.
>
> Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
@@ -186,6 +186,13 @@ int dma_resv_reserve_fences(struct dma_resv *obj, unsigned int num_fences)
dma_resv_assert_held(obj);
+ /* Driver and component code should never call this function with
+ * num_fences=0. If they do it usually points to bugs when calculating
+ * the number of needed fences dynamically.
+ */
+ if (WARN_ON(!num_fences))
+ return -EINVAL;
+
old = dma_resv_fences_list(obj);
if (old && old->max_fences) {
if ((old->num_fences + num_fences) <= old->max_fences)