[ 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: 01d6c3578379 ("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>
[ Upstream commit 7621350c6bb20fb6ab7eb988833ab96eac3dcbef ]
DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT can't be used when we hold locks
since we are basically waiting for userspace to do something.
Holding a lock while doing so can trivial deadlock with page faults
etc...
So make lockdep complain when a driver tries to do this.
v2: Add lockdep_assert_none_held() macro.
v3: Add might_sleep() and also use lockdep_assert_none_held() in the
IOCTL path.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patchwork.freedesktop.org/patch/414944/
Stable-dep-of: 3c43177ffb54 ("drm/syncobj: call drm_syncobj_fence_add_wait when WAIT_AVAILABLE flag is set")
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 101c9f637efa1655f55876644d4439e552267527 ]
If DRM_IOCTL_SYNCOBJ_TIMELINE_WAIT is invoked with the
DRM_SYNCOBJ_WAIT_FLAGS_WAIT_AVAILABLE flag set but no fence has yet been
submitted for the given timeline point the call will fail immediately
with EINVAL. This does not match the intended behavior where the call
should wait until the fence has been submitted (or the timeout expires).
The following small example program illustrates the issue. It should
wait for 5 seconds and then print ETIME, but instead it terminates right
away after printing EINVAL.
#include <stdio.h>
#include <fcntl.h>
#include <time.h>
#include <errno.h>
#include <xf86drm.h>
int main(void)
{
int fd = open("/dev/dri/card0", O_RDWR);
uint32_t syncobj;
drmSyncobjCreate(fd, 0, &syncobj);
struct timespec ts;
clock_gettime(CLOCK_MONOTONIC, &ts);
uint64_t point = 1;
if (drmSyncobjTimelineWait(fd, &syncobj, &point, 1,
ts.tv_sec * 1000000000 + ts.tv_nsec + 5000000000, // 5s
DRM_SYNCOBJ_WAIT_FLAGS_WAIT_AVAILABLE, NULL)) {
printf("drmSyncobjTimelineWait failed %d\n", errno);
}
}
Fixes: 01d6c3578379 ("drm/syncobj: add support for timeline point wait v8")
Signed-off-by: Erik Kurzinger <ekurzinger@nvidia.com>
Reviewed by: Simon Ser <contact@emersion.fd>
Signed-off-by: Simon Ser <contact@emersion.fr>
Link: https://patchwork.freedesktop.org/patch/msgid/1fac96f1-2f3f-f9f9-4eb0-340f27a8f6c0@nvidia.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
