[GitHub] [arrow] westonpace commented on a change in pull request #9941: ARROW-12220: [C++][CI] Thread sanitizer failure

[GitBox <gi...@apache.org>]

westonpace commented on a change in pull request #9941:
URL: https://github.com/apache/arrow/pull/9941#discussion_r609106645



##########
File path: cpp/src/arrow/util/async_generator.h
##########
@@ -1195,25 +1199,48 @@ class BackgroundGenerator {
             ClearQueue();
             queue.push(spawn_status);
           }
+          task_finished.MarkFinished();
         }
       }
     }
 
     internal::Executor* io_executor;
     Iterator<T> it;
+    bool started;
     bool running;
     bool finished;
+    bool should_shutdown;
     int max_q;
     int q_restart;
     std::queue<Result<T>> queue;
     util::optional<Future<T>> waiting_future;
     util::Mutex mutex;
+    Future<> task_finished;
+  };
+
+  struct Cleanup {
+    explicit Cleanup(State* state) : state(state) {}
+    ~Cleanup() {
+      Future<> finish_fut;
+      {
+        auto lock = state->mutex.Lock();
+        if (!state->started) {

Review comment:
       I don't think running works.  Consider the cleanup happens while the background thread is about to call `waiting_future.MarkFinished(next);` and the queue has just filled up so `running` is false.  If we don't wait and just return then it is possible the callback accesses deleted state.




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