bpo-36626: fix asyncio run_forever blocks indefinitely

Lib/asyncio/base_events.py

@@ -412,6 +412,7 @@ def create_task(self, coro, *, name=None):
         else:
             task = self._task_factory(self, coro)
             tasks._set_task_name(task, name)
+        self._write_to_self()
 
         return task
 
@@ -595,6 +596,7 @@ def stop(self):
         Every callback already scheduled will still run.  This simply informs
         run_forever to stop looping after a complete iteration.
         """
+        self._write_to_self()
         self._stopping = True
 
     def close(self):

Lib/test/test_asyncio/test_base_events.py

@@ -255,6 +255,7 @@ def cb(arg):
             calls.append(arg)
 
         self.loop._process_events = mock.Mock()
+        self.loop._write_to_self = mock.Mock()
         self.loop.call_later(-1, cb, 'a')
         self.loop.call_later(-2, cb, 'b')
         test_utils.run_briefly(self.loop)
@@ -265,6 +266,7 @@ def cb():
             self.loop.stop()
 
         self.loop._process_events = mock.Mock()
+        self.loop._write_to_self = mock.Mock()
         delay = 0.1
 
         when = self.loop.time() + delay
@@ -486,6 +488,7 @@ def throw():
             raise ShowStopper
 
         self.loop._process_events = mock.Mock()
+        self.loop._write_to_self = mock.Mock()
         self.loop.call_soon(throw)
         try:
             self.loop.run_until_complete(foo(0.1))
@@ -547,6 +550,7 @@ def test_subprocess_shell_invalid_args(self):
 
     def test_default_exc_handler_callback(self):
         self.loop._process_events = mock.Mock()
+        self.loop._write_to_self = mock.Mock()
 
         def zero_error(fut):
             fut.set_result(True)
@@ -574,6 +578,7 @@ def zero_error(fut):
 
     def test_default_exc_handler_coro(self):
         self.loop._process_events = mock.Mock()
+        self.loop._write_to_self = mock.Mock()
 
         @asyncio.coroutine
         def zero_error_coro():
@@ -719,6 +724,7 @@ def test_set_task_factory_invalid(self):
 
     def test_set_task_factory(self):
         self.loop._process_events = mock.Mock()
+        self.loop._write_to_self = mock.Mock()
 
         class MyTask(asyncio.Task):
             pass
@@ -835,6 +841,7 @@ def raise_keyboard_interrupt():
             raise KeyboardInterrupt
 
         self.loop._process_events = mock.Mock()
+        self.loop._write_to_self = mock.Mock()
         self.loop.call_exception_handler = mock.Mock()
 
         try:
@@ -854,6 +861,7 @@ def raise_keyboard_interrupt():
             raise KeyboardInterrupt
 
         self.loop._process_events = mock.Mock()
+        self.loop._write_to_self = mock.Mock()
 
         try:
             self.loop.run_until_complete(raise_keyboard_interrupt())
@@ -894,6 +902,7 @@ def clear_selector():
 
         self.loop._process_events = proc_events
         self.loop._selector.select.return_value = (event_sentinel,)
+        self.loop._write_to_self = mock.Mock()
 
         for i in range(1, 3):
             with self.subTest('Loop %d/2' % i):
@@ -913,13 +922,15 @@ def callback():
             count += 1
 
         self.loop._process_events = mock.Mock()
+        self.loop._write_to_self = mock.Mock()
         self.loop.call_soon(callback)
         test_utils.run_once(self.loop)
         self.assertEqual(count, 1)
 
     def test_run_forever_pre_stopped(self):
         # Test that the old idiom for pre-stopping the loop works.
         self.loop._process_events = mock.Mock()
+        self.loop._write_to_self = mock.Mock()
         self.loop.stop()
         self.loop.run_forever()
         self.loop._selector.select.assert_called_once_with(0)
@@ -1860,6 +1871,7 @@ def simple_coroutine():
 
     @mock.patch('asyncio.base_events.logger')
     def test_log_slow_callbacks(self, m_logger):
+        self.loop._write_to_self = mock.Mock()
         def stop_loop_cb(loop):
             loop.stop()
 

Lib/test/test_asyncio/test_pep492.py

@@ -38,6 +38,7 @@ def setUp(self):
         self.loop._process_events = mock.Mock()
         self.loop._selector = mock.Mock()
         self.loop._selector.select.return_value = ()
+        self.loop._write_to_self = mock.Mock()
         self.set_event_loop(self.loop)
 
 

Lib/test/test_asyncio/test_runners.py

@@ -38,6 +38,7 @@ async def shutdown_asyncgens():
             loop.shutdown_ag_run = True
         loop.shutdown_asyncgens = shutdown_asyncgens
 
+        loop._write_to_self = mock.Mock()
         return loop
 
     def setUp(self):

Misc/NEWS.d/next/Library/2019-04-15-17-19-29.bpo-36626.9Ps8cq.rst

@@ -0,0 +1 @@
+wake up loop