Merge pull request #9178 from JiayiFeng/fix_bugs_in_reader

Fix bugs in c++ readers

paddle/fluid/operators/reader/create_double_buffer_reader_op.cc

@@ -48,20 +48,24 @@ class DoubleBufferReader : public framework::DecoratedReader {
 
   void start_thread() {
     buffer_ = framework::MakeChannel<Item>(kDoubleBufferSize);
-    std::thread prefetch([this] { PrefetchThreadFunc(); });
-    prefetch.detach();
+    prefetcher_ = std::thread([this] { PrefetchThreadFunc(); });
   }
 
   void ReadNext(std::vector<framework::LoDTensor>* out) override;
   void ReInit() override;
 
-  ~DoubleBufferReader() { buffer_->Close(); }
+  ~DoubleBufferReader() {
+    buffer_->Close();
+    prefetcher_.join();
+    delete buffer_;
+  }
 
   bool HasNext() const override;
 
  private:
   void PrefetchThreadFunc();
 
+  std::thread prefetcher_;
   framework::Channel<Item>* buffer_;
   platform::Place place_;
   std::vector<std::unique_ptr<platform::DeviceContext>> ctxs_;
@@ -134,6 +138,8 @@ void DoubleBufferReader::ReadNext(std::vector<framework::LoDTensor>* out) {
 void DoubleBufferReader::ReInit() {
   reader_->ReInit();
   buffer_->Close();
+  prefetcher_.join();
+  delete buffer_;
   start_thread();
 }
 
@@ -159,11 +165,12 @@ void DoubleBufferReader::PrefetchThreadFunc() {
 
     if (!buffer_->Send(&batch)) {
       VLOG(5) << "WARNING: The double buffer channel has been closed. The "
-                 "prefetch thread terminates.";
+                 "prefetch thread will terminate.";
       break;
     }
   }
   buffer_->Close();
+  VLOG(5) << "Prefetch thread terminates.";
 }
 
 bool DoubleBufferReader::HasNext() const {

paddle/fluid/operators/reader/create_shuffle_reader_op.cc

@@ -34,6 +34,9 @@ class ShuffleReader : public framework::DecoratedReader {
   }
 
   void ReadNext(std::vector<framework::LoDTensor>* out) override {
+    if (!HasNext()) {
+      PADDLE_THROW("There is no next data!");
+    }
     if (iteration_pos_ >= buffer_.size()) {
       VLOG(10) << "Resetting shuffle buffer";
       ReadIntoBuffers();
@@ -50,7 +53,6 @@ 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;