[05/12] dma-buf: Report signaled links inside dma-fence-chain
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Message ID 20200323134348.8513-5-chris@chris-wilson.co.uk
State New
Headers show
Series
  • [01/12] drm/i915/selftests: Add request throughput measurement to perf
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Commit Message

Chris Wilson March 23, 2020, 1:43 p.m. UTC
Whenever we walk along the dma-fence-chain, we prune signaled links to
keep the chain nice and tidy. This leads to situations where we can
prune a link and report the earlier fence as the target seqno --
violating our own consistency checks that the seqno is not more advanced
than the last element in a dma-fence-chain.

Report a NULL fence and success if the seqno has already been signaled.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 drivers/dma-buf/dma-fence-chain.c | 7 +++++++
 1 file changed, 7 insertions(+)

Patch
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diff --git a/drivers/dma-buf/dma-fence-chain.c b/drivers/dma-buf/dma-fence-chain.c
index 3d123502ff12..c435bbba851c 100644
--- a/drivers/dma-buf/dma-fence-chain.c
+++ b/drivers/dma-buf/dma-fence-chain.c
@@ -99,6 +99,12 @@  int dma_fence_chain_find_seqno(struct dma_fence **pfence, uint64_t seqno)
 		return -EINVAL;
 
 	dma_fence_chain_for_each(*pfence, &chain->base) {
+		if ((*pfence)->seqno < seqno) { /* already signaled */
+			dma_fence_put(*pfence);
+			*pfence = NULL;
+			break;
+		}
+
 		if ((*pfence)->context != chain->base.context ||
 		    to_dma_fence_chain(*pfence)->prev_seqno < seqno)
 			break;
@@ -222,6 +228,7 @@  EXPORT_SYMBOL(dma_fence_chain_ops);
  * @chain: the chain node to initialize
  * @prev: the previous fence
  * @fence: the current fence
+ * @seqno: the sequence number (syncpt) of the fence within the chain
  *
  * Initialize a new chain node and either start a new chain or add the node to
  * the existing chain of the previous fence.