Commit ab3b5d51 authored Jan 19, 2024 by Erik Kurzinger Committed by sanglipeng1 Jul 23, 2024

drm/syncobj: call drm_syncobj_fence_add_wait when WAIT_AVAILABLE flag is set

stable inclusion
from stable-v5.10.211
commit c6551ff227f69f315e38eb2e726f023cc4c139d2
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IAF2J4

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c6551ff227f69f315e38eb2e726f023cc4c139d2

--------------------------------

[ Upstream commit 3c43177ffb54ea5be97505eb8e2690e99ac96bc9 ]

When waiting for a syncobj timeline point whose fence has not yet been
submitted with the WAIT_FOR_SUBMIT flag, a callback is registered using
drm_syncobj_fence_add_wait and the thread is put to sleep until the
timeout expires. If the fence is submitted before then,
drm_syncobj_add_point will wake up the sleeping thread immediately which
will proceed to wait for the fence to be signaled.

However, if the WAIT_AVAILABLE flag is used instead,
drm_syncobj_fence_add_wait won't get called, meaning the waiting thread
will always sleep for the full timeout duration, even if the fence gets
submitted earlier. If it turns out that the fence *has* been submitted
by the time it eventually wakes up, it will still indicate to userspace
that the wait completed successfully (it won't return -ETIME), but it
will have taken much longer than it should have.

To fix this, we must call drm_syncobj_fence_add_wait if *either* the
WAIT_FOR_SUBMIT flag or the WAIT_AVAILABLE flag is set. The only
difference being that with WAIT_FOR_SUBMIT we will also wait for the
fence to be signaled after it has been submitted while with
WAIT_AVAILABLE we will return immediately.

IGT test patch: https://lists.freedesktop.org/archives/igt-dev/2024-January/067537.html



v1 -> v2: adjust lockdep_assert_none_held_once condition

(cherry picked from commit 8c44ea81634a4a337df70a32621a5f3791be23df)

Fixes: 01d6c357 ("drm/syncobj: add support for timeline point wait v8")
Signed-off-by: Erik Kurzinger <ekurzinger@nvidia.com>
Signed-off-by: Simon Ser <contact@emersion.fr>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Simon Ser <contact@emersion.fr>
Link: https://patchwork.freedesktop.org/patch/msgid/20240119163208.3723457-1-ekurzinger@nvidia.com


Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng1 <sanglipeng1@jd.com>

parent 440fb4af

drivers/gpu/drm/drm_syncobj.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -960,7 +960,8 @@ static signed long drm_syncobj_array_wait_timeout(struct drm_syncobj **syncobjs,
		uint64_t *points;
		uint32_t signaled_count, i;

		if (flags & DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT)
		if (flags & (DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT \|
		DRM_SYNCOBJ_WAIT_FLAGS_WAIT_AVAILABLE))
		lockdep_assert_none_held_once();

		points = kmalloc_array(count, sizeof(*points), GFP_KERNEL);
		@@ -1029,7 +1030,8 @@ static signed long drm_syncobj_array_wait_timeout(struct drm_syncobj **syncobjs,
		* fallthough and try a 0 timeout wait!
		*/

		if (flags & DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT) {
		if (flags & (DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT \|
		DRM_SYNCOBJ_WAIT_FLAGS_WAIT_AVAILABLE)) {
		for (i = 0; i < count; ++i)
		drm_syncobj_fence_add_wait(syncobjs[i], &entries[i]);
		}