Re: [PATCH] drm/sched: Don't crash kernel on wrong params

[Tvrtko Ursulin]

On 07/11/2025 12:55, Philipp Stanner wrote:
drm_sched_job_arm() just panics the kernel with BUG_ON() in case of an
entity being NULL. While drm_sched_job_arm() crashing or not effectively
arming jobs is certainly a huge issue that needs to be noticed,
completely shooting down the kernel reduces the probability of reaching
and debugging a system to 0.

Moreover, the checkpatch script by now strongly discourages all new uses
of BUG_ON() for this reason.

Replace the BUG_ON() in drm_sched_job_arm() with a WARN_ON().

Signed-off-by: Philipp Stanner <pha...@kernel.org>
---
  drivers/gpu/drm/scheduler/sched_main.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/scheduler/sched_main.c 
b/drivers/gpu/drm/scheduler/sched_main.c
index 1d4f1b822e7b..3bf4ae0ca4bc 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -857,7 +857,7 @@ void drm_sched_job_arm(struct drm_sched_job *job)
        struct drm_gpu_scheduler *sched;
        struct drm_sched_entity *entity = job->entity;
  
-	BUG_ON(!entity);
+       WARN_ON(!entity);
        drm_sched_entity_select_rq(entity);

void drm_sched_entity_select_rq(struct drm_sched_entity *entity)
{
        struct dma_fence *fence;
        struct drm_gpu_scheduler *sched;
        struct drm_sched_rq *rq;

        /* single possible engine and already selected */
        if (!entity->sched_list)

Still the same end result.

I believe best practice is to simply not have BUG_ON's followed by null 
pointer dereferences since they add no value. Ie. it should just be 
removed and not replaced.

Regards,

Tvrtko

Regards,

Tvrtko

        sched = entity->rq->sched;