[PATCH] drm/amdgpu: fix task hang from failed job submission during process kill

[Philipp Stanner]

Hi,

title: this patch changes nothing in amdgpu.

Thus, the prefix must be drm/sched: Fix […]


Furthermore, please use scripts/get_maintainer. A few relevant folks
are missing. +Cc Danilo, Matthew


On Mon, 2025-08-11 at 15:20 +0800, Liu01 Tong wrote:
> During process kill, drm_sched_entity_flush() will kill the vm
> entities.
> 

What is a "vm entity"? This seems to be driver-specific language.


>  The following job submissions of this process will fail, and
> the resources of these jobs have not been released, nor have the fences
> been signalled, causing tasks to hang.
> 
> Fix by not doing job init when the entity is stopped. And when the job
> is already submitted, free the job resource if the entity is stopped.

I'm not sure I can fully follow. Can you give more details on why that
bug doesn't always occur?

In general: Why is this something that needs to be fixed in the
scheduler? amdgpu knows when it killed an entity. Why can't it stop
submitting thereafter?

> 
> Signed-off-by: Liu01 Tong <Tong.Liu01 at amd.com>
> Signed-off-by: Lin.Cao <lincao12 at amd.com>

Two authors? AFAIK should contain a Co-authored-by tag then.

> ---
>  drivers/gpu/drm/scheduler/sched_entity.c | 13 +++++++------
>  drivers/gpu/drm/scheduler/sched_main.c   |  5 +++++
>  2 files changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
> index ac678de7fe5e..1e744b2eb2db 100644
> --- a/drivers/gpu/drm/scheduler/sched_entity.c
> +++ b/drivers/gpu/drm/scheduler/sched_entity.c
> @@ -570,6 +570,13 @@ void drm_sched_entity_push_job(struct drm_sched_job *sched_job)
>  	bool first;
>  	ktime_t submit_ts;
>  
> +	if (entity->stopped) {

This screams "race!" because you're checking for the entity being
stopped now without the lock, as was done before.

That's definitely a no-go because that has caused big trouble and the
past and is still causing trouble right now at other places where the
lock was not taken:

https://lore.kernel.org/dri-devel/20250731093008.45267-2-phasta@kernel.org/


> +		DRM_ERROR("Trying to push job to a killed entity\n");
> +		INIT_WORK(&sched_job->work, drm_sched_entity_kill_jobs_work);
> +		schedule_work(&sched_job->work);
> +		return;
> +	}
> +
>  	trace_drm_sched_job(sched_job, entity);
>  	atomic_inc(entity->rq->sched->score);
>  	WRITE_ONCE(entity->last_user, current->group_leader);
> @@ -589,12 +596,6 @@ void drm_sched_entity_push_job(struct drm_sched_job *sched_job)
>  
>  		/* Add the entity to the run queue */
>  		spin_lock(&entity->lock);
> -		if (entity->stopped) {
> -			spin_unlock(&entity->lock);
> -
> -			DRM_ERROR("Trying to push to a killed entity\n");
> -			return;
> -		}
>  
>  		rq = entity->rq;
>  		sched = rq->sched;
> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> index bfea608a7106..c15b17d9ffe3 100644
> --- a/drivers/gpu/drm/scheduler/sched_main.c
> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> @@ -795,6 +795,11 @@ int drm_sched_job_init(struct drm_sched_job *job,
>  		return -ENOENT;
>  	}
>  
> +	if (unlikely(entity->stopped)) {
> +		pr_err("*ERROR* %s: entity is stopped!\n", __func__);
> +		return -EINVAL;
> +	}

Same here, racy.


Regards,
Philipp

> +
>  	if (unlikely(!credits)) {
>  		pr_err("*ERROR* %s: credits cannot be 0!\n", __func__);
>  		return -EINVAL;