[PATCH 1/2] drm/sched: Guard against NULL dev in drm_sched_job trace event

[oushixiong1025]

From: Shixiong Ou <oushixiong@xxxxxxxxxx>

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.

Add a NULL check following the same pattern used by the CXL
subsystem (drivers/cxl/core/trace.h). When dev is NULL, the
trace output will show "none" instead of crashing.

  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@xxxxxxxxxx>
---
 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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