fix: prevent crash when a service is deleted before finishing predict

Author: Bycob

src/mlservice.h

@@ -187,6 +187,9 @@ namespace dd
             }
           ++hit;
         }
+
+      // wait for predict to finish
+      boost::unique_lock<boost::shared_mutex> lock2(_train_or_predict_mutex);
     }
 
     /**
@@ -323,7 +326,7 @@ namespace dd
                                // XXX: due to lock below, queued jobs may not
                                // start in requested order
                                boost::unique_lock<boost::shared_mutex> lock(
-                                   _train_mutex);
+                                   _train_or_predict_mutex);
                                APIData out;
                                int run_code = this->train(ad, out);
                                std::pair<int, APIData> p(local_tcounter,
@@ -336,7 +339,8 @@ namespace dd
         }
       else
         {
-          boost::unique_lock<boost::shared_mutex> lock(_train_mutex);
+          boost::unique_lock<boost::shared_mutex> lock(
+              _train_or_predict_mutex);
           this->_has_predict = false;
           int status = this->train(ad, out);
           APIData ad_params_out = ad.getobj("parameters").getobj("output");
@@ -498,7 +502,7 @@ namespace dd
     oatpp::Object<DTO::PredictBody> predict_job(const APIData &ad,
                                                 const bool &chain = false)
     {
-      if (!_train_mutex.try_lock_shared())
+      if (!_train_or_predict_mutex.try_lock_shared())
         throw MLServiceLockException(
             "Predict call while training with an offline learning algorithm");
 
@@ -513,13 +517,13 @@ namespace dd
         }
       catch (std::exception &e)
         {
-          _train_mutex.unlock_shared();
+          _train_or_predict_mutex.unlock_shared();
           this->_stats.predict_end(false);
           throw;
         }
       this->_stats.predict_end(true);
 
-      _train_mutex.unlock_shared();
+      _train_or_predict_mutex.unlock_shared();
       return out;
     }
 
@@ -533,7 +537,7 @@ namespace dd
         _training_jobs; // XXX: the futures' dtor blocks if the object is being
                         // terminated
     std::unordered_map<int, APIData> _training_out;
-    boost::shared_mutex _train_mutex;
+    boost::shared_mutex _train_or_predict_mutex;
   };
 
 }