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 | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c index b81fceb0b8a2..c5437ee03e3f 100644 --- a/drivers/gpu/drm/scheduler/sched_main.c +++ b/drivers/gpu/drm/scheduler/sched_main.c @@ -419,6 +419,8 @@ 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)) { + dma_fence_put(s_job->s_fence->parent); + s_job->s_fence->parent = NULL; atomic_dec(&sched->hw_rq_count); } else { /* @@ -548,7 +550,6 @@ 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 +559,11 @@ 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 +957,9 @@ 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 +967,6 @@ 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)); -- 2.25.1
