[GitHub] [arrow] westonpace commented on a change in pull request #9842: ARROW-12040: [R] [CI] [C++] test-r-rstudio-r-base-3.6-opensuse15 timing out during tests

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

westonpace commented on a change in pull request #9842:
URL: https://github.com/apache/arrow/pull/9842#discussion_r608204235



##########
File path: cpp/src/arrow/filesystem/s3fs.cc
##########
@@ -1142,82 +1145,67 @@ struct TreeWalker : public std::enable_shared_from_this<TreeWalker> {
         recursion_handler_(std::move(recursion_handler)) {}
 
  private:
-  std::mutex mutex_;
-  Future<> future_;
-  std::atomic<int32_t> num_in_flight_;
+  std::shared_ptr<TaskGroup> task_group_;
+  util::Mutex mutex_;
 
   Status DoWalk() {
-    future_ = decltype(future_)::Make();
-    num_in_flight_ = 0;
+    task_group_ =
+        TaskGroup::MakeThreaded(io_context_.executor(), io_context_.stop_token());
     WalkChild(base_dir_, /*nesting_depth=*/0);
     // When this returns, ListObjectsV2 tasks either have finished or will exit early
-    return future_.status();
+    return task_group_->Finish();
   }
 
-  bool is_finished() const { return future_.is_finished(); }
-
-  void ListObjectsFinished(Status st) {
-    const auto in_flight = --num_in_flight_;
-    if (!st.ok() || !in_flight) {
-      future_.MarkFinished(std::move(st));
-    }
-  }
+  bool ok() const { return task_group_->ok(); }
 
   struct ListObjectsV2Handler {
     std::shared_ptr<TreeWalker> walker;
     std::string prefix;
     int32_t nesting_depth;
     S3Model::ListObjectsV2Request req;
 
-    void operator()(const Result<S3Model::ListObjectsV2Outcome>& result) {
+    Status operator()(const Result<S3Model::ListObjectsV2Outcome>& result) {
       // Serialize calls to operation-specific handlers
-      std::unique_lock<std::mutex> guard(walker->mutex_);
-      if (walker->is_finished()) {
+      if (!walker->ok()) {
         // Early exit: avoid executing handlers if DoWalk() returned
-        return;
+        return Status::OK();
       }
       if (!result.ok()) {
-        HandleError(result.status());
-        return;
+        return result.status();
       }
       const auto& outcome = *result;
       if (!outcome.IsSuccess()) {
-        Status st = walker->error_handler_(outcome.GetError());
-        HandleError(std::move(st));
-        return;
+        {
+          auto guard = walker->mutex_.Lock();
+          return walker->error_handler_(outcome.GetError());
+        }
       }
-      HandleResult(outcome.GetResult());
+      return HandleResult(outcome.GetResult());
     }
 
     void SpawnListObjectsV2() {
       auto walker = this->walker;
       auto req = this->req;
-      auto maybe_fut = walker->io_context_.executor()->Submit(
-          walker->io_context_.stop_token(),
-          [walker, req]() { return walker->client_->ListObjectsV2(req); });
-      if (!maybe_fut.ok()) {
-        HandleError(maybe_fut.status());
-        return;
-      }
-      maybe_fut->AddCallback(*this);
+      auto cb = *this;

Review comment:
       Removed the extraneous captures.




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