From 062d5a56b401162ebd0232e42135c87177ad68ec Mon Sep 17 00:00:00 2001
From: gongweibao <weibao.gong@gmail.com>
Date: Mon, 11 Jun 2018 09:42:54 +0800
Subject: [PATCH] Add comments to a singleton. (#11333)

---
 paddle/fluid/framework/data_type.cc | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/paddle/fluid/framework/data_type.cc b/paddle/fluid/framework/data_type.cc
index b6b93cf422..60382faffb 100644
--- a/paddle/fluid/framework/data_type.cc
+++ b/paddle/fluid/framework/data_type.cc
@@ -28,6 +28,9 @@ struct DataTypeMap {
 };
 
 static DataTypeMap* InitDataTypeMap();
+// 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
 static DataTypeMap& gDataTypeMap() {
   static DataTypeMap* g_data_type_map_ = InitDataTypeMap();
   return *g_data_type_map_;
-- 
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