Drivers that can delegate waits to the firmware/GPU pass the scheduled
fence to drm_sched_job_add_dependency(), and issue wait commands to
the firmware/GPU at job submission time. For this to be possible, they
need all their 'native' dependencies to have a valid parent since this
is where the actual HW fence information are encoded.
In drm_sched_main(), we currently call drm_sched_fence_set_parent()
after drm_sched_fence_scheduled(), leaving a short period of time
during which the job depending on this fence can be submitted.
Since setting parent and signaling the fence are two things that are
kinda related (you can't have a parent if the job hasn't been scheduled),
it probably makes sense to pass the parent fence to
drm_sched_fence_scheduled() and let it call drm_sched_fence_set_parent()
before it signals the scheduled fence.
Here is a detailed description of the race we are fixing here:
Thread A Thread B
- calls drm_sched_fence_scheduled()
- signals s_fence->scheduled which
wakes up thread B
- entity dep signaled, checking
the next dep
- no more deps waiting
- entity is picked for job
submission by drm_gpu_scheduler
- run_job() is called
- run_job() tries to
collect native fence info from
s_fence->parent, but it's
NULL =>
BOOM, we can't do our native
wait
- calls drm_sched_fence_set_parent()
v2:
* Fix commit message
v3:
* Add a detailed description of the race to the commit message
* Add Luben's R-b
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Cc: Frank Binns <frank.binns@imgtec.com>
Cc: Sarah Walker <sarah.walker@imgtec.com>
Cc: Donald Robson <donald.robson@imgtec.com>
Cc: Luben Tuikov <luben.tuikov@amd.com>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: "Christian König" <christian.koenig@amd.com>
Reviewed-by: Luben Tuikov <luben.tuikov@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230623075204.382350-1-boris.brezillon@collabora.com
As the finished fence is the one that is exposed to userspace, and
therefore the one that other operations, like atomic update, would
block on, we need to propagate the deadline from from the finished
fence to the actual hw fence.
v2: Split into drm_sched_fence_set_parent() (ckoenig)
v3: Ensure a thread calling drm_sched_fence_set_deadline_finished() sees
fence->parent set before drm_sched_fence_set_parent() does this
test_bit(DMA_FENCE_FLAG_HAS_DEADLINE_BIT).
Signed-off-by: Rob Clark <robdclark@chromium.org>
Acked-by: Luben Tuikov <luben.tuikov@amd.com>
drm_sched_job_cleanup() will pass an uninitialized fence to
drm_sched_fence_free(), which will cause to_drm_sched_fence() to return
a NULL fence object, causing a NULL pointer deref when this NULL object
is passed to kmem_cache_free().
Let's create a new drm_sched_fence_free() function that takes a
drm_sched_fence pointer and suffix the old function with _rcu. While at
it, complain if drm_sched_fence_free() is passed an initialized fence
or if drm_sched_fence_free_rcu() is passed an uninitialized fence.
Fixes: dbe48d030b ("drm/sched: Split drm_sched_job_init")
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210903120554.444101-1-boris.brezillon@collabora.com
Fix kernel-doc warnings.
drivers/gpu/drm/scheduler/sched_fence.c:110: warning: Function parameter or
member 'f' not described in 'drm_sched_fence_release_scheduled'
drivers/gpu/drm/scheduler/sched_fence.c:110: warning: Excess function
parameter 'fence' description in 'drm_sched_fence_release_scheduled'
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
The scheduler of the entity is decided by the run queue on which
it is queued. This patch avoids us the effort required to maintain
a sync between rq and sched field when we start shifting entites
among different rqs.
Signed-off-by: Nayan Deshmukh <nayan26deshmukh@gmail.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
To free the fence from the amdgpu_fence_slab, need twice call_rcu, to avoid
the amdgpu_fence_slab_fini call kmem_cache_destroy(amdgpu_fence_slab) before
kmem_cache_free(amdgpu_fence_slab, fence), add rcu_barrier after drm_sched_entity_fini.
The kmem_cache_free(amdgpu_fence_slab, fence)'s call trace as below:
1.drm_sched_entity_fini ->
drm_sched_entity_cleanup ->
dma_fence_put(entity->last_scheduled) ->
drm_sched_fence_release_finished ->
drm_sched_fence_release_scheduled ->
call_rcu(&fence->finished.rcu, drm_sched_fence_free)
2.drm_sched_fence_free ->
dma_fence_put(fence->parent) ->
amdgpu_fence_release ->
call_rcu(&f->rcu, amdgpu_fence_free) ->
kmem_cache_free(amdgpu_fence_slab, fence);
v2:put the barrier before the kmem_cache_destroy
v3:put the dma_fence_put(fence->parent) before call_rcu in
drm_sched_fence_release_scheduled
Signed-off-by: Emily Deng <Emily.Deng@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This moves and renames the AMDGPU scheduler to a common location in DRM
in order to facilitate re-use by other drivers. This is mostly a straight
forward rename with no code changes.
One notable exception is the function to_drm_sched_fence(), which is no
longer a inline header function to avoid the need to export the
drm_sched_fence_ops_scheduled and drm_sched_fence_ops_finished structures.
Reviewed-by: Chunming Zhou <david1.zhou@amd.com>
Tested-by: Dieter Nützel <Dieter@nuetzel-hh.de>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
