[PATCH] drm/amdgpu: fix sched fence slab teardown

[zhoucm1]

Acked-by: Chunming Zhou <david1.zhou at amd.com>

On 2016年10月24日 02:31, Grazvydas Ignotas wrote:
> 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 at 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);
>   }