Fix copy bug for same src and dst Tensor (#44992)

* Fix copy bug for same src and dst Tensor

* Improve code design

* Fix errors

paddle/phi/core/tensor_utils.cc

@@ -35,6 +35,19 @@ void Copy(const Context& dev_ctx,
   auto* src_ptr = src.data();
   const auto& src_place = src.place();
 
+  if (&src == dst) {
+    if (paddle::platform::is_same_place(src_place, dst_place)) {
+      VLOG(6) << "Skip copy the same data(" << src_ptr << ") from " << src_place
+              << " to " << dst_place;
+    } else {
+      VLOG(6) << "Src and dst are the same Tensor, in-place copy data("
+              << src_ptr << ") from " << src_place << " to " << dst_place;
+      const DenseTensor src_copy = src;
+      Copy(dev_ctx, src_copy, dst_place, blocking, dst);
+    }
+    return;
+  }
+
   VLOG(3) << "TensorCopy " << src.dims() << " from " << src.place() << " to "
           << dst_place;
 

paddle/phi/kernels/gpu/class_center_sample_kernel.cu

@@ -571,13 +571,11 @@ void ClassCenterSampleKernel(const Context& dev_ctx,
           dev_ctx.template Alloc<T>(remapped_label));
 
   // step 14: Get sampled class center for output
-  paddle::framework::TensorCopySync(
-      num_classes_per_device, phi::CPUPlace(), &num_classes_per_device);
-  //  phi::Copy<Context>(dev_ctx,
-  //                     num_classes_per_device,
-  //                     phi::CPUPlace(),
-  //                     true,
-  //                     &num_classes_per_device);
+  phi::Copy<Context>(dev_ctx,
+                     num_classes_per_device,
+                     phi::CPUPlace(),
+                     true,
+                     &num_classes_per_device);
   T actual_num_samples = num_classes_per_device.data<T>()[rank + 1];
   sampled_local_class_center->Resize(phi::make_ddim({actual_num_samples}));