[GitHub] [arrow] bkietz commented on a diff in pull request #36536: GH-36523: [C++] Fix TSan-detected lock ordering issues in S3

[via GitHub]

bkietz commented on code in PR #36536:
URL: https://github.com/apache/arrow/pull/36536#discussion_r1256088406


##########
cpp/src/arrow/filesystem/s3fs.cc:
##########
@@ -1158,7 +1179,7 @@ class ObjectInputFile final : public io::RandomAccessFile 
{
     req.SetKey(ToAwsString(path_.key));
 
     ARROW_ASSIGN_OR_RAISE(auto client_lock, holder_->Lock());
-    auto outcome = client_lock->HeadObject(req);
+    auto outcome = std::move(client_lock)->HeadObject(req);

Review Comment:
   Or you might even prefer
   ```c++
   template <auto MemberPtr, typename... Args>
   auto S3ClientHolder::LockThenCall(Args&&... args) {
     return Lock().Map([&](S3ClientLock client_lock) {
       return (client_lock.get()->*MemberPtr)(std::forward<Args>(args)...);
     });
   }
   ```
   
   used like
   ```suggestion
       ARROW_ASSIGN_OR_RAISE(auto outcome, 
holder_->LockThenCall<&S3Client::HeadObject>(req));
   ```



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