From: jsg <jsg@openbsd.org>
Date: Tue, 14 Dec 2021 13:32:09 +0000 (+0000)
Subject: drm/syncobj: Deal with signalled fences in drm_syncobj_find_fence.
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=6115a8aab61c2617a33d0a21d67f50f585d4730a;p=openbsd

drm/syncobj: Deal with signalled fences in drm_syncobj_find_fence.

From Bas Nieuwenhuizen
2737d0bc21b6db199b4145e12b9f1745577d7944 in linux 5.10.y/5.10.85
b19926d4f3a660a8b76e5d989ffd1168e619a5c4 in mainline linux
---

diff --git a/sys/dev/pci/drm/drm_syncobj.c b/sys/dev/pci/drm/drm_syncobj.c
index 2d157a1fd37..f792dd15501 100644
--- a/sys/dev/pci/drm/drm_syncobj.c
+++ b/sys/dev/pci/drm/drm_syncobj.c
@@ -395,8 +395,17 @@ int drm_syncobj_find_fence(struct drm_file *file_private,
 
 	if (*fence) {
 		ret = dma_fence_chain_find_seqno(fence, point);
-		if (!ret)
+		if (!ret) {
+			/* If the requested seqno is already signaled
+			 * drm_syncobj_find_fence may return a NULL
+			 * fence. To make sure the recipient gets
+			 * signalled, use a new fence instead.
+			 */
+			if (!*fence)
+				*fence = dma_fence_get_stub();
+
 			goto out;
+		}
 		dma_fence_put(*fence);
 	} else {
 		ret = -EINVAL;