fix cpu pynative coredump

mindspore/ccsrc/backend/session/session_basic.cc

@@ -1718,6 +1718,11 @@ void SessionBasic::UpdateGraphDynamicShapeAttr(const NotNull<KernelGraphPtr> &ro
 }
 
 void SessionBasic::CleanUselessTensorsImpl(const std::shared_ptr<std::vector<tensor::TensorPtr>> &useless_tensors) {
+  auto ms_context = MsContext::GetInstance();
+  std::string device_target = ms_context->get_param<std::string>(MS_CTX_DEVICE_TARGET);
+  if (device_target == "CPU") {
+    return;
+  }
   for (const auto &tensor : *useless_tensors) {
     tensor->set_device_address(nullptr);
   }

tests/st/pynative/test_pynative_lenet.py

@@ -131,9 +131,11 @@ class GradWrap(nn.Cell):
 @pytest.mark.level0
 @pytest.mark.platform_arm_ascend_training
 @pytest.mark.platform_x86_ascend_training
+@pytest.mark.platform_x86_cpu
+@pytest.mark.platform_x86_gpu_training
 @pytest.mark.env_onecard
 def test_ascend_pynative_lenet():
-    context.set_context(mode=context.PYNATIVE_MODE, device_target="Ascend")
+    context.set_context(mode=context.PYNATIVE_MODE)
 
     epoch_size = 20
     batch_size = 32