To free fences, call_rcu() is used, which calls amd_sched_fence_free() after a grace period. During teardown, there is no guarantee all callbacks have finished, so sched_fence_slab may be destroyed before all fences have been freed. If we are lucky, this results in some slab warnings, if not, we get a crash in one of rcu threads because callback is called after amdgpu has already been unloaded.
Fix it with a rcu_barrier().
Fixes: 189e0fb76304 ("drm/amdgpu: RCU protected amd_sched_fence_release") Signed-off-by: Grazvydas Ignotas notasas@gmail.com --- drivers/gpu/drm/amd/scheduler/gpu_scheduler.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c b/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c index 963a24d..910b8d5 100644 --- a/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c +++ b/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c @@ -645,6 +645,7 @@ void amd_sched_fini(struct amd_gpu_scheduler *sched) { if (sched->thread) kthread_stop(sched->thread); + rcu_barrier(); if (atomic_dec_and_test(&sched_fence_slab_ref)) kmem_cache_destroy(sched_fence_slab); }