From: Vitaly Prosyak <vitaly.prosyak@xxxxxxx>
During an IGT GPU reset test we see again oops despite of
commit 0c8c901aaaebc9 (drm/sched: Check scheduler ready before calling
timeout handling).
It uses ready condition whether to call drm_sched_fault which unwind
the TDR leads to GPU reset.
However it looks the ready condition is overloaded with other meanings,
for example, for the following stack is related GPU reset :
0 gfx_v9_0_cp_gfx_start
1 gfx_v9_0_cp_gfx_resume
2 gfx_v9_0_cp_resume
3 gfx_v9_0_hw_init
4 gfx_v9_0_resume
5 amdgpu_device_ip_resume_phase2
does the following:
/* start the ring */
gfx_v9_0_cp_gfx_start(adev);
ring->sched.ready = true;
The same approach is for other ASICs as well :
gfx_v8_0_cp_gfx_resume
gfx_v10_0_kiq_resume, etc...
As a result, our GPU reset test causes GPU fault which calls unconditionally gfx_v9_0_fault
and then drm_sched_fault. However now it depends on whether the interrupt service routine
drm_sched_fault is executed after gfx_v9_0_cp_gfx_start is completed which sets the ready
field of the scheduler to true even for uninitialized schedulers and causes oops vs
no fault or when ISR drm_sched_fault is completed prior gfx_v9_0_cp_gfx_start and
NULL pointer dereference does not occur.
Use the field timeout_wq to prevent oops for uninitialized schedulers.
The field could be initialized by the work queue of resetting the domain.
Fixes: 0c8c901aaaebc9 ("drm/sched: Check scheduler ready before calling timeout handling")
v1: Corrections to commit message (Luben)
Signed-off-by: Vitaly Prosyak <vitaly.prosyak@xxxxxxx>
Reviewed-by: Luben Tuikov <luben.tuikov@xxxxxxx>
---
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 649fac2e1ccb..670b7997f389 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -308,7 +308,7 @@ static void drm_sched_start_timeout(struct drm_gpu_scheduler *sched)
*/
void drm_sched_fault(struct drm_gpu_scheduler *sched)
{
- if (sched->ready)
+ if (sched->timeout_wq)
mod_delayed_work(sched->timeout_wq, &sched->work_tdr, 0);
}
EXPORT_SYMBOL(drm_sched_fault);
--
2.25.1
