use unique ptr to hold auto_grown_mutex_ for default copy and move constructor

paddle/fluid/framework/selected_rows.cc

@@ -153,7 +153,7 @@ bool SelectedRows::Set(int64_t key, const framework::Tensor& value) {
   }
   PADDLE_ENFORCE_EQ(value.dims()[0], static_cast<size_t>(1),
                     "The first dim of value should be 1.");
-  std::lock_guard<std::mutex> lock(auto_grown_mutex_);
+  std::lock_guard<std::mutex> lock(*auto_grown_mutex_.get());
   auto index = Index(key);
   bool is_new_key = false;
   if (index == -1) {

paddle/fluid/framework/selected_rows.h

@@ -15,6 +15,7 @@ limitations under the License. */
 #pragma once
 
 #include <algorithm>
+#include <memory>
 #include <utility>
 #include <vector>
 
@@ -46,11 +47,13 @@ class SelectedRows {
   SelectedRows(const std::vector<int64_t>& rows, const int64_t& height)
       : rows_(rows), height_(height) {
     value_.reset(new Tensor());
+    auto_grown_mutex_.reset(new std::mutex);
   }
 
   SelectedRows() {
     height_ = 0;
     value_.reset(new Tensor());
+    auto_grown_mutex_.reset(new std::mutex);
   }
 
   platform::Place place() const { return value_->place(); }
@@ -125,7 +128,7 @@ class SelectedRows {
   Vector<int64_t> rows_;
   std::unique_ptr<Tensor> value_{nullptr};
   int64_t height_;
-  std::mutex auto_grown_mutex_;
+  std::unique_ptr<std::mutex> auto_grown_mutex_{nullptr};
 };
 
 /*