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@xxxxxxxxxxxxxxxxxx>
Tested-by: Venkata Sandeep Dhanalakota <venkata.s.dhanalakota@xxxxxxxxx>
Reviewed-by: Venkata Sandeep Dhanalakota <venkata.s.dhanalakota@xxxxxxxxx>
---
drivers/dma-buf/dma-fence-chain.c | 7 +++++++
1 file changed, 7 insertions(+)
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.
--
2.20.1
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