There was probably a misunderstand on how the dma-fence-chain is
supposed to work or what dma_fence_chain_find_seqno() is supposed to
return.
dma_fence_chain_find_seqno() is here to give us the fence to wait upon
for a particular point in the timeline. The timeline progresses only
when all the points prior to a given number have completed.
Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
Fixes: dc2f7e67a28a5c ("dma-buf: Exercise dma-fence-chain under selftests")
---
drivers/dma-buf/st-dma-fence-chain.c | 43 ++++++++++++++--------------
1 file changed, 21 insertions(+), 22 deletions(-)
diff --git a/drivers/dma-buf/st-dma-fence-chain.c b/drivers/dma-buf/st-dma-fence-chain.c
index 5d45ba7ba3cd..9525f7f56119 100644
--- a/drivers/dma-buf/st-dma-fence-chain.c
+++ b/drivers/dma-buf/st-dma-fence-chain.c
@@ -318,15 +318,16 @@ static int find_out_of_order(void *arg)
goto err;
}
- if (fence && fence != fc.chains[1]) {
+ /*
+ * We signaled the middle fence (2) of the 1-2-3 chain. The behavior
+ * of the dma-fence-chain is to make us wait for all the fences up to
+ * the point we want. Since fence 1 is still not signaled, this what
+ * we should get as fence to wait upon (fence 2 being garbage
+ * collected during the traversal of the chain).
+ */
+ if (fence != fc.chains[0]) {
pr_err("Incorrect chain-fence.seqno:%lld reported for completed seqno:2\n",
- fence->seqno);
-
- dma_fence_get(fence);
- err = dma_fence_chain_find_seqno(&fence, 2);
- dma_fence_put(fence);
- if (err)
- pr_err("Reported %d for finding self!\n", err);
+ fence ? fence->seqno : 0);
err = -EINVAL;
}
@@ -415,20 +416,18 @@ static int __find_race(void *arg)
if (!fence)
goto signal;
- err = dma_fence_chain_find_seqno(&fence, seqno);
- if (err) {
- pr_err("Reported an invalid fence for find-self:%d\n",
- seqno);
- dma_fence_put(fence);
- break;
- }
-
- if (fence->seqno < seqno) {
- pr_err("Reported an earlier fence.seqno:%lld for seqno:%d\n",
- fence->seqno, seqno);
- err = -EINVAL;
- dma_fence_put(fence);
- break;
+ /*
+ * We can only find ourselves if we are on fence we were
+ * looking for.
+ */
+ if (fence->seqno == seqno) {
+ err = dma_fence_chain_find_seqno(&fence, seqno);
+ if (err) {
+ pr_err("Reported an invalid fence for find-self:%d\n",
+ seqno);
+ dma_fence_put(fence);
+ break;
+ }
}
dma_fence_put(fence);
--
2.27.0
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