dma-buf: fix dma-fence-chain out of order test

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@intel.com>
Fixes: dc2f7e67a28a5c ("dma-buf: Exercise dma-fence-chain under selftests")
Link: https://patchwork.freedesktop.org/patch/372960/
Signed-off-by: Christian König <christian.koenig@amd.com>

diff --git a/drivers/dma-buf/st-dma-fence-chain.c b/drivers/dma-buf/st-dma-fence-chain.c
index 5d45ba7ba3cd3df187f7ced6d46a6a77075fe69c..9525f7f561194eef69695b1f9da217ea24a643d6 100644 (file)
--- 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);