From 9922968dacb39bbdf18c12a6ae7d3d1b590cc7b3 Mon Sep 17 00:00:00 2001
From: Simon Hengel <sol@typeful.net>
Date: Tue, 19 May 2026 06:54:39 +0700
Subject: [PATCH] Warden: Don't spawn new threads when canceling

---
 Control/Concurrent/Async/Warden.hs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Control/Concurrent/Async/Warden.hs b/Control/Concurrent/Async/Warden.hs
index a3b19a5..013f2d0 100644
--- a/Control/Concurrent/Async/Warden.hs
+++ b/Control/Concurrent/Async/Warden.hs
@@ -62,7 +62,7 @@ create = Warden <$> newMVar (Just mempty)
 shutdown :: Warden -> IO ()
 shutdown (Warden v) = do
   r <- swapMVar v Nothing
-  mapM_ (Async.mapConcurrently_ Async.cancel) r
+  mapM_ (Async.cancelMany . HashSet.toList) r
 
 forget :: Warden -> Async a -> IO ()
 forget (Warden v) async = modifyMVar_ v $ \x -> case x of