From: Shixiong Ou <oushixiong@kylinos.cn>

The drm_sched_job trace event class calls dev_name() on
sched_job->sched->dev without checking for NULL. Since the
dev field in drm_sched_init_args is optional (used for
debugging), a NULL dev causes a kernel oops when the trace
event fires.

The DRM scheduler KUnit tests do not set the dev field in
drm_sched_init_args, leaving sched->dev as NULL. This causes
a NULL pointer dereference when the drm_sched_job trace event
fires during test execution, as dev_name(NULL) is called.

  Unable to handle kernel NULL pointer dereference at virtual address 0000000000000050
  Call trace:
   trace_event_raw_event_drm_sched_job+0x90/0x258
   __traceiter_drm_sched_job_queue+0x4c/0x78
   drm_sched_entity_push_job+0x188/0x380
   drm_sched_basic_entity_cleanup+0xfc/0x240
   kunit_try_run_case+0x74/0x170

Signed-off-by: Shixiong Ou <oushixiong@kylinos.cn>
---
 drivers/gpu/drm/scheduler/gpu_scheduler_trace.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/scheduler/gpu_scheduler_trace.h b/drivers/gpu/drm/scheduler/gpu_scheduler_trace.h
index 261713dd7d5a..319a3ec54bec 100644
--- a/drivers/gpu/drm/scheduler/gpu_scheduler_trace.h
+++ b/drivers/gpu/drm/scheduler/gpu_scheduler_trace.h
@@ -61,7 +61,8 @@ DECLARE_EVENT_CLASS(drm_sched_job,
 			     __string(name, sched_job->sched->name)
 			     __field(u32, job_count)
 			     __field(int, hw_job_count)
-			     __string(dev, dev_name(sched_job->sched->dev))
+			     __string(dev, sched_job->sched->dev ?
+				      dev_name(sched_job->sched->dev) : "none")
 			     __field(u64, fence_context)
 			     __field(u64, fence_seqno)
 			     __field(u64, client_id)
-- 
2.25.1


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On Fri, 2026-08-21 at 16:47 +0800, oushixiong1025@163.com wrote:
> From: Shixiong Ou <oushixiong@kylinos.cn>
> 
> The drm_sched_job trace event class calls dev_name() on
> sched_job->sched->dev without checking for NULL. Since the
> dev field in drm_sched_init_args is optional (used for
> debugging), a NULL dev causes a kernel oops when the trace
> event fires.
> 
> The DRM scheduler KUnit tests do not set the dev field in
> drm_sched_init_args, leaving sched->dev as NULL. This causes
> a NULL pointer dereference when the drm_sched_job trace event
> fires during test execution, as dev_name(NULL) is called.
> 
>   Unable to handle kernel NULL pointer dereference at virtual address 0000000000000050
>   Call trace:
>    trace_event_raw_event_drm_sched_job+0x90/0x258
>    __traceiter_drm_sched_job_queue+0x4c/0x78
>    drm_sched_entity_push_job+0x188/0x380
>    drm_sched_basic_entity_cleanup+0xfc/0x240
>    kunit_try_run_case+0x74/0x170

Yes, that looks correct, thx for fixing.

Can you send a v2 with your commit message's line length set to 72
characters? Only the title line should be aimed to be 50 chars wide.


Regards,
P.

> 
> Signed-off-by: Shixiong Ou <oushixiong@kylinos.cn>
> ---
>  drivers/gpu/drm/scheduler/gpu_scheduler_trace.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/scheduler/gpu_scheduler_trace.h b/drivers/gpu/drm/scheduler/gpu_scheduler_trace.h
> index 261713dd7d5a..319a3ec54bec 100644
> --- a/drivers/gpu/drm/scheduler/gpu_scheduler_trace.h
> +++ b/drivers/gpu/drm/scheduler/gpu_scheduler_trace.h
> @@ -61,7 +61,8 @@ DECLARE_EVENT_CLASS(drm_sched_job,
>  			     __string(name, sched_job->sched->name)
>  			     __field(u32, job_count)
>  			     __field(int, hw_job_count)
> -			     __string(dev, dev_name(sched_job->sched->dev))
> +			     __string(dev, sched_job->sched->dev ?
> +				      dev_name(sched_job->sched->dev) : "none")
>  			     __field(u64, fence_context)
>  			     __field(u64, fence_seqno)
>  			     __field(u64, client_id)