This is a note to let you know that I've just added the patch titled
drm/syncobj: Deal with signalled fences in drm_syncobj_find_fence.
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-syncobj-deal-with-signalled-fences-in-drm_syncobj_find_fence.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b19926d4f3a660a8b76e5d989ffd1168e619a5c4 Mon Sep 17 00:00:00 2001
From: Bas Nieuwenhuizen <bas@xxxxxxxxxxxxxxxxxxx>
Date: Wed, 8 Dec 2021 03:39:35 +0100
Subject: drm/syncobj: Deal with signalled fences in drm_syncobj_find_fence.
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From: Bas Nieuwenhuizen <bas@xxxxxxxxxxxxxxxxxxx>
commit b19926d4f3a660a8b76e5d989ffd1168e619a5c4 upstream.
dma_fence_chain_find_seqno only ever returns the top fence in the
chain or an unsignalled fence. Hence if we request a seqno that
is already signalled it returns a NULL fence. Some callers are
not prepared to handle this, like the syncobj transfer functions
for example.
This behavior is "new" with timeline syncobj and it looks like
not all callers were updated. To fix this behavior make sure
that a successful drm_sync_find_fence always returns a non-NULL
fence.
v2: Move the fix to drm_syncobj_find_fence from the transfer
functions.
Fixes: ea569910cbab ("drm/syncobj: add transition iotcls between binary and timeline v2")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Bas Nieuwenhuizen <bas@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Christian König <christian.koenig@xxxxxxx>
Acked-by: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20211208023935.17018-1-bas@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/drm_syncobj.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
--- a/drivers/gpu/drm/drm_syncobj.c
+++ b/drivers/gpu/drm/drm_syncobj.c
@@ -329,8 +329,17 @@ int drm_syncobj_find_fence(struct drm_fi
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;
Patches currently in stable-queue which might be from bas@xxxxxxxxxxxxxxxxxxx are
queue-5.4/drm-syncobj-deal-with-signalled-fences-in-drm_syncobj_find_fence.patch
