Add mutex for decorated_chain

Author: reyoung

paddle/fluid/framework/reader.cc

@@ -21,6 +21,7 @@ ReaderBase::~ReaderBase() {}
 
 void ReaderBase::InsertDecoratedReader(
     const std::shared_ptr<ReaderBase> &decorated_reader) {
+  std::lock_guard<std::mutex> guard(decorated_readers_mtx_);
   decorated_readers_.emplace_back(decorated_reader);
 }
 

paddle/fluid/framework/reader.h

@@ -45,6 +45,7 @@ class ReaderBase {
       const std::shared_ptr<ReaderBase>& decorated_reader);
   // A set of which readers that decorated this reader.
   std::vector<std::weak_ptr<ReaderBase>> decorated_readers_;
+  std::mutex decorated_readers_mtx_;
 };
 
 class DecoratedReader : public ReaderBase,