On Tue Aug 25, 2026 at 12:36 PM CEST, oushixiong1025 wrote: > From: Shixiong Ou <[email protected]> > > 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 <[email protected]> > --- > v1->v2: > Change each line of the message to be within 75 characters > > 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")
I don't think that we should make such changes for Kunit tests only; it implies that a NULL dev now would be a valid value for the scheduler. Why can't we have the Kunit test create a fake device for this? For instance, this is where struct faux_device becomes useful.
