Add recursion guard when cancelling tasks

Summary: As in title, fixes stack overflow when cancellation is triggered on tasks with mutual dependencies

Reviewed By: carljm

Differential Revision: D44685444

fbshipit-source-id: 966426a5eb5c7cd86ad79b2ef4f94f3baf091411

Lib/test/test_cinder.py

@@ -2653,7 +2653,38 @@ async def test_suspended_duplicate_success(self):
  await self.run_duplicate_success_test("test_suspended_duplicate_success", True)
 
 
+@cinder_support.skipUnderJIT("Recursion checks are not consistent in JIT")
+class TestTaskCancel(unittest.TestCase):
+ def test_recursive_cancel(self):
+ def run(TaskConstructor):
+ async def main():
+ # create first task
+ fut = asyncio.Future()
+ t1 = TaskConstructor(f1(fut))
+ t2 = TaskConstructor(f2(t1))
+ fut.set_result(t2)
+ await asyncio.sleep(1)
+ t1.cancel()
+
+ async def f1(fut):
+ task = await fut
+ await task
+
+ async def f2(task):
+ await task
+
+ with self.assertRaises(RecursionError):
+ asyncio.run(main())
+
+ with self.subTest("PyTask"):
+ run(asyncio.tasks._PyTask)
+
+ with self.subTest("asyncio.Task"):
+ run(asyncio.Task)
+
+
 class GeneralRegressionTests(unittest.TestCase):
+
  # This tests a fix for an issue reported in T130047792
  @async_test
  async def test_skip_duplicated_coro_on_earlier_failure(self):

Modules/_asynciomodule.c

@@ -1,6 +1,7 @@
 #include "Python.h"
 #include "pycore_list.h" // _PyList_ITEMS()
 #include "pycore_pyerrors.h" // _PyErr_ClearExcState()
+#include "pycore_ceval.h" // _Py_EnterRecursiveCall()
 #include "pycore_pystate.h"
 #include "pycore_call.h"
 #include <stddef.h> // offsetof()
@@ -3780,7 +3781,12 @@ task_cancel_impl(TaskObj *self, PyObject *msg) {
  if (tableref == NULL) {
  return -1;
  }
+ PyThreadState *tstate = PyThreadState_GET();
+ if (_Py_EnterRecursiveCall(tstate, " while calling 'cancel' on the task")) {
+ return -1;
+ }
  is_true = tableref->cancel(self->task_fut_waiter, msg);
+ _Py_LeaveRecursiveCall(tstate);
 
  if (is_true < 0) {
  return -1;