From 14a1c7511b3081979084b5d78bbbf3f171466490 Mon Sep 17 00:00:00 2001
From: Clyraz <111095996+Clyraz@users.noreply.github.com>
Date: Wed, 17 Jun 2026 13:48:00 +0200
Subject: [PATCH 1/3] Fix race conditions in cancellable_promise

---
 strings/base_coroutine_threadpool.h | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/strings/base_coroutine_threadpool.h b/strings/base_coroutine_threadpool.h
index 057d5b548..c85e53f9c 100644
--- a/strings/base_coroutine_threadpool.h
+++ b/strings/base_coroutine_threadpool.h
@@ -151,7 +151,7 @@ WINRT_EXPORT namespace winrt
 
         void revoke_canceller()
         {
-            while (m_canceller.exchange(nullptr, std::memory_order_acquire) == cancelling_ptr)
+            while (m_canceller.load(std::memory_order_acquire) == cancelling_ptr)
             {
                 std::this_thread::yield();
             }
@@ -160,6 +160,11 @@ WINRT_EXPORT namespace winrt
         void cancel()
         {
             auto canceller = m_canceller.exchange(cancelling_ptr, std::memory_order_acquire);
+            if (canceller == cancelling_ptr)
+            {
+                return;
+            }
+
             struct unique_cancellation_lock
             {
                 cancellable_promise* promise;
@@ -169,7 +174,7 @@ WINRT_EXPORT namespace winrt
                 }
             } lock{ this };
 
-            if ((canceller != nullptr) && (canceller != cancelling_ptr))
+            if (canceller != nullptr)
             {
                 canceller(m_context);
             }

From 0031352e93f1d442d1ffeef97de79d90968178be Mon Sep 17 00:00:00 2001
From: Clyraz <111095996+Clyraz@users.noreply.github.com>
Date: Thu, 18 Jun 2026 21:23:57 +0200
Subject: [PATCH 2/3] Properly revoke canceller

---
 strings/base_coroutine_threadpool.h | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/strings/base_coroutine_threadpool.h b/strings/base_coroutine_threadpool.h
index c85e53f9c..b7dc7e7fb 100644
--- a/strings/base_coroutine_threadpool.h
+++ b/strings/base_coroutine_threadpool.h
@@ -151,10 +151,15 @@ WINRT_EXPORT namespace winrt
 
         void revoke_canceller()
         {
-            while (m_canceller.load(std::memory_order_acquire) == cancelling_ptr)
+            auto canceller = m_canceller.load(std::memory_order_relaxed);
+            do
             {
-                std::this_thread::yield();
-            }
+                if (canceller == cancelling_ptr) {
+
+                    std::this_thread::yield();
+                    canceller = nullptr;
+                }
+            } while (!m_canceller.compare_exchange_strong(canceller, nullptr, std::memory_order_acquire, std::memory_order_relaxed));
         }
 
         void cancel()

From f0bb08aef49e2f9ceaf76f632b4e7bfd0fdc3067 Mon Sep 17 00:00:00 2001
From: Clyraz <111095996+Clyraz@users.noreply.github.com>
Date: Thu, 18 Jun 2026 22:34:27 +0200
Subject: [PATCH 3/3] Format changes

---
 strings/base_coroutine_threadpool.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/strings/base_coroutine_threadpool.h b/strings/base_coroutine_threadpool.h
index b7dc7e7fb..312daef3b 100644
--- a/strings/base_coroutine_threadpool.h
+++ b/strings/base_coroutine_threadpool.h
@@ -154,8 +154,8 @@ WINRT_EXPORT namespace winrt
             auto canceller = m_canceller.load(std::memory_order_relaxed);
             do
             {
-                if (canceller == cancelling_ptr) {
-
+                if (canceller == cancelling_ptr)
+                {
                     std::this_thread::yield();
                     canceller = nullptr;
                 }