Re: [PATCH] dma-buf: fix reservation_object_wait_timeout_rcu to wait correctly

[zhoucm1 <david1.zhou@amd.com>]

On 2017年07月22日 00:20, Christian König wrote:
> From: Christian König <christian.koenig@amd.com>
>
> With hardware resets in mind it is possible that all shared fences are
> signaled, but the exlusive isn't. Fix waiting for everything in this situation.
>
> Signed-off-by: Christian König <christian.koenig@amd.com>
> ---
>   drivers/dma-buf/reservation.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c
> index e2eff86..ce3f9c1 100644
> --- a/drivers/dma-buf/reservation.c
> +++ b/drivers/dma-buf/reservation.c
> @@ -461,7 +461,7 @@ long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
>   		}
>   	}
>   
> -	if (!shared_count) {
> +	if (!fence) {
previous code seems be a bug, the exclusive fence isn't be waited at all 
if shared_count != 0.

With your fix, there still is a case the exclusive fence could be 
skipped, that when fobj->shared[shared_count-1] isn't signalled.

Regards,
David Zhou
>   		struct dma_fence *fence_excl = rcu_dereference(obj->fence_excl);
>   
>   		if (fence_excl &&