[llvm] [Support] Join threads when stopping the ThreadPoolExecutor (PR #166054)

[Maurice Heumann via llvm-commits]

https://github.com/momo5502 updated https://github.com/llvm/llvm-project/pull/166054

>From 8a3f2ef0415663b17aba61bfb2a51bd7284271d0 Mon Sep 17 00:00:00 2001
From: momo5502 <mauriceheumann at gmail.com>
Date: Sun, 2 Nov 2025 11:56:45 +0100
Subject: [PATCH] [Support] Join threads when stopping ThreadPoolExecutor

---
 llvm/lib/Support/Parallel.cpp | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/llvm/lib/Support/Parallel.cpp b/llvm/lib/Support/Parallel.cpp
index 8e0c724accb36..2fd3dee8010a1 100644
--- a/llvm/lib/Support/Parallel.cpp
+++ b/llvm/lib/Support/Parallel.cpp
@@ -82,26 +82,26 @@ class ThreadPoolExecutor : public Executor {
   ThreadPoolExecutor() = delete;
 
   void stop() {
+    Stop = true;
+    Cond.notify_all();
+    ThreadsCreated.get_future().wait();
+
+    std::vector<std::thread> ThreadsToJoin;
     {
       std::lock_guard<std::mutex> Lock(Mutex);
-      if (Stop)
-        return;
-      Stop = true;
+      ThreadsToJoin.swap(Threads);
     }
-    Cond.notify_all();
-    ThreadsCreated.get_future().wait();
-  }
 
-  ~ThreadPoolExecutor() override {
-    stop();
     std::thread::id CurrentThreadId = std::this_thread::get_id();
-    for (std::thread &T : Threads)
+    for (std::thread &T : ThreadsToJoin)
       if (T.get_id() == CurrentThreadId)
         T.detach();
       else
         T.join();
   }
 
+  ~ThreadPoolExecutor() override { stop(); }
+
   struct Creator {
     static void *call() { return new ThreadPoolExecutor(strategy); }
   };