Re: [PATCH] gpu: drm: remove redundant dma_fence_put() when drm_sched_job_add_dependency() fails

[Andrey Grodzovsky]

On 2022-04-25 04:36, Hangyu Hua wrote:

When drm_sched_job_add_dependency() fails, dma_fence_put() will be called
internally. Calling it again after drm_sched_job_add_dependency() finishes
may result in a dangling pointer.

Fix this by removing redundant dma_fence_put().

Signed-off-by: Hangyu Hua <hbh...@gmail.com>
---
  drivers/gpu/drm/lima/lima_gem.c        | 1 -
  drivers/gpu/drm/scheduler/sched_main.c | 1 -
  2 files changed, 2 deletions(-)

diff --git a/drivers/gpu/drm/lima/lima_gem.c b/drivers/gpu/drm/lima/lima_gem.c
index 55bb1ec3c4f7..99c8e7f6bb1c 100644
--- a/drivers/gpu/drm/lima/lima_gem.c
+++ b/drivers/gpu/drm/lima/lima_gem.c
@@ -291,7 +291,6 @@ static int lima_gem_add_deps(struct drm_file *file, struct 
lima_submit *submit)

err = drm_sched_job_add_dependency(&submit->task->base, fence);

                if (err) {
-                       dma_fence_put(fence);
                        return err;

Makes sense here

                }
        }
diff --git a/drivers/gpu/drm/scheduler/sched_main.c 
b/drivers/gpu/drm/scheduler/sched_main.c
index b81fceb0b8a2..ebab9eca37a8 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -708,7 +708,6 @@ int drm_sched_job_add_implicit_dependencies(struct 
drm_sched_job *job,
                dma_fence_get(fence);
                ret = drm_sched_job_add_dependency(job, fence);
                if (ret) {
-                       dma_fence_put(fence);

Not sure about this one since if you look at the relevant commits -
'drm/scheduler: fix drm_sched_job_add_implicit_dependencies' and
'drm/scheduler: fix drm_sched_job_add_implicit_dependencies harder'
You will see that the dma_fence_put here balances the extra dma_fence_get
above

Andrey

                        return ret;
                }
        }