fix bugs

Author: JiayiFeng

paddle/fluid/operators/reader/create_double_buffer_reader_op.cc

@@ -159,11 +159,12 @@ void DoubleBufferReader::PrefetchThreadFunc() {
 
     if (!buffer_->Send(&batch)) {
       VLOG(5) << "WARNING: The double buffer channel has been closed. The "
-                 "prefetch thread terminates.";
-      break;
+                 "prefetch thread terminate.";
+      return;
     }
   }
   buffer_->Close();
+  VLOG(5) << "Prefetch thread terminates.";
 }
 
 bool DoubleBufferReader::HasNext() const {

paddle/fluid/operators/reader/create_shuffle_reader_op.cc

@@ -50,7 +50,6 @@ class ShuffleReader : public framework::DecoratedReader {
     buffer_.clear();
     buffer_.reserve(buffer_size_);
     iteration_pos_ = 0;
-    PADDLE_ENFORCE(reader_->HasNext());
     for (size_t i = 0; i < buffer_size_; ++i) {
       if (!reader_->HasNext()) {
         break;