gh-105836: Fix asyncio.run_coroutine_threadsafe leaving underlying cancelled asyncio task running

Lib/asyncio/futures.py

@@ -389,7 +389,7 @@ def _set_state(future, other):
 
     def _call_check_cancel(destination):
         if destination.cancelled():
-            if source_loop is None or source_loop is dest_loop:
+            if source_loop is None or source_loop is events._get_running_loop():
                 source.cancel()
             else:
                 source_loop.call_soon_threadsafe(source.cancel)
@@ -398,7 +398,7 @@ def _call_set_state(source):
         if (destination.cancelled() and
                 dest_loop is not None and dest_loop.is_closed()):
             return
-        if dest_loop is None or dest_loop is source_loop:
+        if dest_loop is None or dest_loop is events._get_running_loop():
             _set_state(destination, source)
         else:
             if dest_loop.is_closed():

Lib/test/test_asyncio/test_tasks.py

@@ -8,6 +8,7 @@
 import random
 import re
 import sys
+from threading import Event
 import traceback
 import types
 import unittest
@@ -3680,6 +3681,24 @@ def task_factory(loop, coro):
         (loop, context), kwargs = callback.call_args
         self.assertEqual(context['exception'], exc_context.exception)
 
+    def test_run_coroutine_threadsafe_and_cancel(self):
+        target_started = Event()
+        async def _target():
+            target_started.set()
+            await asyncio.sleep(0.1)
+            return 1
+
+        def _in_thread():
+            thread_future = asyncio.run_coroutine_threadsafe(_target(), self.loop)
+            # wait target started then cancel
+            target_started.wait()
+            thread_future.cancel()
+        _ = self.loop.run_in_executor(None, _in_thread)
+
+        # start main loop to do things
+        self.loop.run_until_complete(asyncio.sleep(0.05))
+        self.assertEqual(0, len(self.loop._ready))
+
 
 class SleepTests(test_utils.TestCase):
     def setUp(self):

Misc/ACKS

@@ -2118,6 +2118,7 @@ Xiang Zhang
 Robert Xiao
 Florent Xicluna
 Yanbo, Xie
+Kaisheng Xu
 Xinhang Xu
 Arnon Yaari
 Alakshendra Yadav

Misc/NEWS.d/next/Library/2025-11-18-15-48-13.gh-issue-105836.sbUw24.rst

@@ -0,0 +1,2 @@
+Fix :meth:`asyncio.run_coroutine_threadsafe` leaving underlying cancelled
+asyncio task running