Re: [PATCH v3 6/9] dma-buf/fence-array: Add fence deadline support

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Am 08.09.21 um 20:00 schrieb Daniel Vetter:
On Fri, Sep 03, 2021 at 11:47:57AM -0700, Rob Clark wrote:
From: Rob Clark <robdclark@xxxxxxxxxxxx>

Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
---
  drivers/dma-buf/dma-fence-array.c | 11 +++++++++++
  1 file changed, 11 insertions(+)

diff --git a/drivers/dma-buf/dma-fence-array.c b/drivers/dma-buf/dma-fence-array.c
index d3fbd950be94..8d194b09ee3d 100644
--- a/drivers/dma-buf/dma-fence-array.c
+++ b/drivers/dma-buf/dma-fence-array.c
@@ -119,12 +119,23 @@ static void dma_fence_array_release(struct dma_fence *fence)
  	dma_fence_free(fence);
  }
+static void dma_fence_array_set_deadline(struct dma_fence *fence,
+					 ktime_t deadline)
+{
+	struct dma_fence_array *array = to_dma_fence_array(fence);
+	unsigned i;
+
+	for (i = 0; i < array->num_fences; ++i)
+		dma_fence_set_deadline(array->fences[i], deadline);
Hm I wonder whether this can go wrong, and whether we need Christian's
massive fence iterator that I've seen flying around. If you nest these
things too much it could all go wrong I think. I looked at other users
which inspect dma_fence_array and none of them have a risk for unbounded
recursion.

That should work fine or at least doesn't add anything new which could go boom.

The dma_fence_array() can't contain other dma_fence_array or dma_fence_chain objects or it could end up in a recursion and corrupt the kernel stack.

That's a well known limitation for other code paths as well.

So Reviewed-by: Christian König <christian.koenig@xxxxxxx> for this one.

Regards,
Christian.


Maybe check with Christian.
-Daniel


+}
+
  const struct dma_fence_ops dma_fence_array_ops = {
  	.get_driver_name = dma_fence_array_get_driver_name,
  	.get_timeline_name = dma_fence_array_get_timeline_name,
  	.enable_signaling = dma_fence_array_enable_signaling,
  	.signaled = dma_fence_array_signaled,
  	.release = dma_fence_array_release,
+	.set_deadline = dma_fence_array_set_deadline,
  };
  EXPORT_SYMBOL(dma_fence_array_ops);
--
2.31.1





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