Polish reshape op

paddle/fluid/operators/reshape_op.h

@@ -119,13 +119,15 @@ class ReshapeKernel : public framework::OpKernel<T> {
     auto *shape_tensor = ctx.Input<framework::LoDTensor>("Shape");
 
     framework::DDim out_dims = out->dims();
+
     if (shape_tensor) {
       auto *shape_data = shape_tensor->data<int>();
-      if (platform::is_gpu_place(ctx.GetPlace())) {
       framework::Tensor cpu_shape_tensor;
+      if (platform::is_gpu_place(ctx.GetPlace())) {
         TensorCopy(*shape_tensor, platform::CPUPlace(), ctx.device_context(),
                    &cpu_shape_tensor);
         shape_data = cpu_shape_tensor.data<int>();
+        ctx.device_context().Wait();
       }
       auto shape =
           std::vector<int>(shape_data, shape_data + shape_tensor->numel());