[lldb-vscode] Fix data race in lldb-vscode when running with ThreadSanitizer

[PRESIDENT810]

Summary

This patch fixes https://github.com/llvm/llvm-project/issues/54768. A ProgressEventReporter creates a dedicated thread that keeps checking whether there are new events that need to be sent to IDE as long as m_thread_should_exit is true. When the VSCode instance is destructed, it will set m_thread_should_exit to false, which caused a data race because at the same time its ProgressEventReporter is reading this value to determine whether it should quit. This fix simply uses mutex to ensure they cannot read and write this value at the same time.

[wallace]

Thanks for doing this fix. I hope tsan doesn't report this anymore

[clayborg]

Another solution would be to make m_thread_should_exit a std::atomic<bool> type instead of just a bool.

[PRESIDENT810]

Update to using std::atomic to avoid data race instead of mutex lock.

[clayborg]

Much easier and cleaner. LGTM

[PRESIDENT810]

Hi, I just forgot to mention that I don't really have access to commit... So if any people see this and this patch looks good to them, maybe please help me commit this one?

[wallace]

Hi! I'll push it for you :)

lldb/tools/lldb-vscode/ProgressEvent.h

 //===-- ProgressEvent.cpp ---------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
+#include <atomic>
 #include <mutex>
 #include <queue>
 #include <thread>
 
 #include "VSCodeForward.h"
 
 #include "llvm/Support/JSON.h"
 
private:
   void ReportStartEvents();
 
   ProgressEventReportCallback m_report_callback;
   std::map<uint64_t, ProgressEventManagerSP> m_event_managers;
   /// Queue of start events in chronological order
   std::queue<ProgressEventManagerSP> m_unreported_start_events;
   /// Thread used to invoke \a ReportStartEvents periodically.
   std::thread m_thread;
-  bool m_thread_should_exit;
+  std::atomic<bool> m_thread_should_exit;
   /// Mutex that prevents running \a Push and \a ReportStartEvents
   /// simultaneously, as both read and modify the same underlying objects.
   std::mutex m_mutex;
 };
 
 } // namespace lldb_vscode