make clone thread safe (#15363)

paddle/fluid/inference/api/analysis_predictor.cc

@@ -561,6 +561,7 @@ AnalysisPredictor::~AnalysisPredictor() {
 }
 
 std::unique_ptr<PaddlePredictor> AnalysisPredictor::Clone() {
+  std::lock_guard<std::mutex> lk(clone_mutex_);
   auto *x = new AnalysisPredictor(config_);
   x->Init(scope_, inference_program_);
   return std::unique_ptr<PaddlePredictor>(x);

paddle/fluid/inference/api/analysis_predictor.h

@@ -115,6 +115,8 @@ class AnalysisPredictor : public PaddlePredictor {
   // concurrency problems, wrong results and memory leak, so cache them.
   std::vector<framework::LoDTensor> feed_tensors_;
   details::TensorArrayBatchCleaner tensor_array_batch_cleaner_;
+  // A mutex help to make Clone thread safe.
+  std::mutex clone_mutex_;
 
  private:
   // Some status here that help to determine the status inside the predictor.

paddle/fluid/inference/api/analysis_predictor_tester.cc

@@ -179,8 +179,9 @@ TEST(AnalysisPredictor, Clone) {
     threads.emplace_back([&predictors, &inputs, i] {
       LOG(INFO) << "thread #" << i << " running";
       std::vector<PaddleTensor> outputs;
+      auto predictor = predictors.front()->Clone();
       for (int j = 0; j < 10; j++) {
-        ASSERT_TRUE(predictors[i]->Run(inputs, &outputs));
+        ASSERT_TRUE(predictor->Run(inputs, &outputs));
       }
     });
   }

paddle/fluid/inference/api/api_impl.cc

@@ -161,6 +161,8 @@ bool NativePaddlePredictor::Run(const std::vector<PaddleTensor> &inputs,
 }
 
 std::unique_ptr<PaddlePredictor> NativePaddlePredictor::Clone() {
+  std::lock_guard<std::mutex> lk(clone_mutex_);
+  VLOG(3) << "Predictor::clone";
   std::unique_ptr<PaddlePredictor> cls(new NativePaddlePredictor(config_));
   // Hot fix the bug that result diff in multi-thread.
   // TODO(Superjomn) re-implement a real clone here.

paddle/fluid/inference/api/api_impl.h

@@ -74,6 +74,8 @@ class NativePaddlePredictor : public PaddlePredictor {
   // Do not use unique_ptr, use parent scope to delete
   framework::Scope *sub_scope_{nullptr};
   details::TensorArrayBatchCleaner tensor_array_batch_cleaner_;
+  // A mutex to make Clone thread safe.
+  std::mutex clone_mutex_;
 };
 
 }  // namespace paddle