polish (#11363)

paddle/fluid/framework/op_info.cc

@@ -17,12 +17,11 @@ limitations under the License. */
 namespace paddle {
 namespace framework {
 
-static OpInfoMap* g_op_info_map = nullptr;
-
+// C++11 removes the need for manual locking. Concurrent execution shall wait if
+// a static local variable is already being initialized.
+// https://stackoverflow.com/questions/11711920/how-to-implement-multithread-safe-singleton-in-c11-without-using-mutex
 OpInfoMap& OpInfoMap::Instance() {
-  if (g_op_info_map == nullptr) {
-    g_op_info_map = new OpInfoMap();
-  }
+  static OpInfoMap* g_op_info_map = new OpInfoMap();
   return *g_op_info_map;
 }
 }  // namespace framework