From: Vitaly Prosyak vitaly.prosyak@amd.com
[ Upstream commit 2da5bffe9eaa5819a868e8eaaa11b3fd0f16a691 ]
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.
v1: Corrections to commit message (Luben)
Fixes: 11b3b9f461c5c4 ("drm/sched: Check scheduler ready before calling timeout handling") Signed-off-by: Vitaly Prosyak vitaly.prosyak@amd.com Link: https://lore.kernel.org/r/20230510135111.58631-1-vitaly.prosyak@amd.com Reviewed-by: Luben Tuikov luben.tuikov@amd.com Signed-off-by: Luben Tuikov luben.tuikov@amd.com Signed-off-by: Sasha Levin sashal@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 1e08cc5a17029..78c959eaef0c5 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);