Am 21.06.22 um 00:03 schrieb Andrey Grodzovsky:
Problem:
This patch caused negative refcount as described in [1] because
for that case parent fence did not signal by the time of drm_sched_stop and hence
kept in pending list the assumption was they will not signal and
so fence was put to account for the s_fence->parent refcount but for
amdgpu which has embedded HW fence (always same parent fence)
drm_sched_fence_release_scheduled was always called and would
still drop the count for parent fence once more. For jobs that
never signaled this imbalance was masked by refcount bug in
amdgpu_fence_driver_clear_job_fences that would not drop
refcount on the fences that were removed from fence drive
fences array (against prevois insertion into the array in
get in amdgpu_fence_emit).
Fix:
Revert this patch and by setting s_job->s_fence->parent to NULL
as before prevent the extra refcount drop in amdgpu when
drm_sched_fence_release_scheduled is called on job release.
Also - align behaviour in drm_sched_resubmit_jobs_ext with that of
drm_sched_main when submitting jobs - take a refcount for the
new parent fence pointer and drop refcount for original kref_init
for new HW fence creation (or fake new HW fence in amdgpu - see next patch).
[1] - https://lore.kernel.org/all/731b7ff1-3cc9-e314-df2a-7c51b76d4db0@xxxxxxx/t/#r00c728fcc069b1276642c325bfa9d82bf8fa21a3
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@xxxxxxx>
Tested-by: Yiqing Yao <yiqing.yao@xxxxxxx>
---
drivers/gpu/drm/scheduler/sched_main.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index b81fceb0b8a2..b38394f5694f 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -419,6 +419,11 @@ void drm_sched_stop(struct drm_gpu_scheduler *sched, struct drm_sched_job *bad)
if (s_job->s_fence->parent &&
dma_fence_remove_callback(s_job->s_fence->parent,
&s_job->cb)) {
+ /* Revert drm/sched: Keep s_fence->parent pointer, no
+ * need anymore for amdgpu and creates only troubles
+ */
Please no amdgpu specific comments in common code.
Apart from that looks like a step into the right direction to me.
Regards,
Christian.
+ dma_fence_put(s_job->s_fence->parent);
+ s_job->s_fence->parent = NULL;
atomic_dec(&sched->hw_rq_count);
} else {
/*
@@ -548,7 +553,6 @@ void drm_sched_resubmit_jobs_ext(struct drm_gpu_scheduler *sched, int max)
if (found_guilty && s_job->s_fence->scheduled.context == guilty_context)
dma_fence_set_error(&s_fence->finished, -ECANCELED);
- dma_fence_put(s_job->s_fence->parent);
fence = sched->ops->run_job(s_job);
i++;
@@ -558,7 +562,11 @@ void drm_sched_resubmit_jobs_ext(struct drm_gpu_scheduler *sched, int max)
s_job->s_fence->parent = NULL;
} else {
- s_job->s_fence->parent = fence;
+
+ s_job->s_fence->parent = dma_fence_get(fence);
+
+ /* Drop for orignal kref_init */
+ dma_fence_put(fence);
}
}
}
@@ -952,6 +960,9 @@ static int drm_sched_main(void *param)
if (!IS_ERR_OR_NULL(fence)) {
s_fence->parent = dma_fence_get(fence);
+ /* Drop for original kref_init of the fence */
+ dma_fence_put(fence);
+
r = dma_fence_add_callback(fence, &sched_job->cb,
drm_sched_job_done_cb);
if (r == -ENOENT)
@@ -959,7 +970,6 @@ static int drm_sched_main(void *param)
else if (r)
DRM_DEV_ERROR(sched->dev, "fence add callback failed (%d)\n",
r);
- dma_fence_put(fence);
} else {
if (IS_ERR(fence))
dma_fence_set_error(&s_fence->finished, PTR_ERR(fence));
