Re: [PATCH] drm/scheduler: Fix sched hang when killing app with dependent jobs

[cao, lin]

[AMD Official Use Only - AMD Internal Distribution Only]

Hi Christian,

Thanks for your suggestion, I modified the patch as:

diff --git a/drivers/gpu/drm/scheduler/sched_entity.c 
b/drivers/gpu/drm/scheduler/sched_entity.c
index e671aa241720..66f2a43c58fd 100644
--- a/drivers/gpu/drm/scheduler/sched_entity.c
+++ b/drivers/gpu/drm/scheduler/sched_entity.c
@@ -177,6 +177,7 @@ static void drm_sched_entity_kill_jobs_work(struct 
work_struct *wrk)
    struct drm_sched_job *job = container_of(wrk, typeof(*job), work);

    drm_sched_fence_scheduled(job->s_fence, NULL);
+   drm_sched_wakeup(job->sched);
    drm_sched_fence_finished(job->s_fence, -ESRCH);
    WARN_ON(job->s_fence->parent);
    job->sched->ops->free_job(job);
--

Thanks,
Lin

________________________________
From: Koenig, Christian <christian.koe...@amd.com>
Sent: Thursday, July 10, 2025 15:52
To: cao, lin <lin....@amd.com>; dri-devel@lists.freedesktop.org 
<dri-devel@lists.freedesktop.org>; amd-...@lists.freedesktop.org 
<amd-...@lists.freedesktop.org>
Cc: Yin, ZhenGuo (Chris) <zhenguo....@amd.com>; Deng, Emily 
<emily.d...@amd.com>; Matthew Brost <matthew.br...@intel.com>; Danilo Krummrich 
<d...@kernel.org>; Philipp Stanner <pha...@kernel.org>
Subject: Re: [PATCH] drm/scheduler: Fix sched hang when killing app with 
dependent jobs

First of all you need to CC the scheduler maintainers, try to use the 
get_maintainer.pl script. Adding them on CC.

On 10.07.25 08:36, Lin.Cao wrote:
> When Application A submits jobs (a1, a2, a3) and application B submits
> job b1 with a dependency on a2's scheduler fence, killing application A
> before run_job(a1) causes drm_sched_entity_kill_jobs_work() to force
> signal all jobs sequentially. However, due to missing work_run_job or
> work_free_job in entity_kill_job_work(), the scheduler enters sleep
> state, causing application B hang.

Ah! Because of optimizing the dependency when submitting to the same scheduler 
in drm_sched_entity_add_dependency_cb().

Yeah that suddenly starts to make sense.

> Add drm_sched_wakeup() when entity_kill_job_work() to preventing
> scheduler sleep and subsequent application hangs.
>
> Signed-off-by: Lin.Cao <linca...@amd.com>
> ---
>  drivers/gpu/drm/scheduler/sched_entity.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/gpu/drm/scheduler/sched_entity.c 
> b/drivers/gpu/drm/scheduler/sched_entity.c
> index e671aa241720..a22b0f65558a 100644
> --- a/drivers/gpu/drm/scheduler/sched_entity.c
> +++ b/drivers/gpu/drm/scheduler/sched_entity.c
> @@ -180,6 +180,7 @@ static void drm_sched_entity_kill_jobs_work(struct 
> work_struct *wrk)
>        drm_sched_fence_finished(job->s_fence, -ESRCH);
>        WARN_ON(job->s_fence->parent);
>        job->sched->ops->free_job(job);
> +     drm_sched_wakeup(job->sched);

That should probably be after drm_sched_fence_scheduled().

Alternatively we could also drop the optimization in 
drm_sched_entity_add_dependency_cb(), scheduling the work item again has only 
minimal overhead.

Apart from that looks good to me.

Regards,
Christian.

>  }
>
>  /* Signal the scheduler finished fence when the entity in question is 
> killed. */