pythongh-128002: fix many thread safety issues in asyncio (python#128147)

* Makes `_asyncio.Task` and `_asyncio.Future` thread-safe by adding critical sections
* Add assertions to check for thread safety checking locking of object by critical sections in internal functions
* Make `_asyncio.all_tasks` thread safe when eager tasks are used
* Add a thread safety test

Author: kumaraditya303

Lib/test/test_asyncio/test_free_threading.py

@@ -0,0 +1,82 @@
+import asyncio
+import unittest
+from threading import Thread
+from unittest import TestCase
+
+from test.support import threading_helper
+
+threading_helper.requires_working_threading(module=True)
+
+def tearDownModule():
+    asyncio._set_event_loop_policy(None)
+
+
+class TestFreeThreading:
+    def test_all_tasks_race(self) -> None:
+        async def main():
+            loop = asyncio.get_running_loop()
+            future = loop.create_future()
+
+            async def coro():
+                await future
+
+            tasks = set()
+
+            async with asyncio.TaskGroup() as tg:
+                for _ in range(100):
+                    tasks.add(tg.create_task(coro()))
+
+                all_tasks = self.all_tasks(loop)
+                self.assertEqual(len(all_tasks), 101)
+
+                for task in all_tasks:
+                    self.assertEqual(task.get_loop(), loop)
+                    self.assertFalse(task.done())
+
+                current = self.current_task()
+                self.assertEqual(current.get_loop(), loop)
+                self.assertSetEqual(all_tasks, tasks | {current})
+                future.set_result(None)
+
+        def runner():
+            with asyncio.Runner() as runner:
+                loop = runner.get_loop()
+                loop.set_task_factory(self.factory)
+                runner.run(main())
+
+        threads = []
+
+        for _ in range(10):
+            thread = Thread(target=runner)
+            threads.append(thread)
+
+        with threading_helper.start_threads(threads):
+            pass
+
+
+class TestPyFreeThreading(TestFreeThreading, TestCase):
+    all_tasks = staticmethod(asyncio.tasks._py_all_tasks)
+    current_task = staticmethod(asyncio.tasks._py_current_task)
+
+    def factory(self, loop, coro, context=None):
+        return asyncio.tasks._PyTask(coro, loop=loop, context=context)
+
+
+@unittest.skipUnless(hasattr(asyncio.tasks, "_c_all_tasks"), "requires _asyncio")
+class TestCFreeThreading(TestFreeThreading, TestCase):
+    all_tasks = staticmethod(getattr(asyncio.tasks, "_c_all_tasks", None))
+    current_task = staticmethod(getattr(asyncio.tasks, "_c_current_task", None))
+
+    def factory(self, loop, coro, context=None):
+        return asyncio.tasks._CTask(coro, loop=loop, context=context)
+
+
+class TestEagerPyFreeThreading(TestPyFreeThreading):
+    def factory(self, loop, coro, context=None):
+        return asyncio.tasks._PyTask(coro, loop=loop, context=context, eager_start=True)
+
+
+@unittest.skipUnless(hasattr(asyncio.tasks, "_c_all_tasks"), "requires _asyncio")
+class TestEagerCFreeThreading(TestCFreeThreading, TestCase):
+    def factory(self, loop, coro, context=None):
+        return asyncio.tasks._CTask(coro, loop=loop, context=context, eager_start=True)