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drm/syncobj: handle NULL fence in syncobj_eventfd_entry_func

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[ Upstream commit 2aa6f5b0fd052e363bb9d4b547189f0bf6b3d6d3 ]

During syncobj_eventfd_entry_func, dma_fence_chain_find_seqno may set
the fence to NULL if the given seqno is signaled and a later seqno has
already been submitted. In that case, the eventfd should be signaled
immediately which currently does not happen.

This is a similar issue to the one addressed by commit b19926d4f3a6
("drm/syncobj: Deal with signalled fences in drm_syncobj_find_fence.").

As a fix, if the return value of dma_fence_chain_find_seqno indicates
success but it sets the fence to NULL, we will assign a stub fence to
ensure the following code still signals the eventfd.

v1 -> v2: assign a stub fence instead of signaling the eventfd

Signed-off-by: Erik Kurzinger <ekurzinger@nvidia.com>
Fixes: c7a472297169 ("drm/syncobj: add IOCTL to register an eventfd")
Signed-off-by: Simon Ser <contact@emersion.fr>
Link: https://patchwork.freedesktop.org/patch/msgid/20240221184527.37667-1-ekurzinger@nvidia.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Erik Kurzinger 2024-02-21 10:44:28 -08:00 committed by Greg Kroah-Hartman
parent 716cfee805
commit 20e1e1a2b8
1 changed files with 12 additions and 1 deletions
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13
drivers/gpu/drm/drm_syncobj.c
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@ -1380,10 +1380,21 @@ syncobj_eventfd_entry_func(struct drm_syncobj *syncobj,
/* This happens inside the syncobj lock */
fence = dma_fence_get(rcu_dereference_protected(syncobj->fence, 1));
if (!fence)
return;
ret = dma_fence_chain_find_seqno(&fence, entry->point);
if (ret != 0 || !fence) {
if (ret != 0) {
/* The given seqno has not been submitted yet. */
dma_fence_put(fence);
return;
} else if (!fence) {
/* If dma_fence_chain_find_seqno returns 0 but sets the fence
* to NULL, it implies that the given seqno is signaled and a
* later seqno has already been submitted. Assign a stub fence
* so that the eventfd still gets signaled below.
*/
fence = dma_fence_get_stub();
}
list_del_init(&entry->node);