Solved deadlock in python windows.

Author: viferga

source/loaders/py_loader/include/py_loader/py_loader_impl.h

@@ -62,6 +62,8 @@ PY_LOADER_NO_EXPORT int py_loader_impl_finalizer_object(loader_impl impl, PyObje
 
 PY_LOADER_NO_EXPORT PyObject *py_loader_impl_capsule_new_null(void);
 
+PY_LOADER_NO_EXPORT int py_loader_impl_initialize_asyncio_module(loader_impl_py py_impl, const int host);
+
 #ifdef __cplusplus
 }
 #endif

source/loaders/py_loader/source/py_loader_impl.c

@@ -2610,7 +2610,12 @@ int py_loader_impl_initialize_argv(loader_impl_py py_impl, int argc, char **argv
 
 static void PyCFunction_dealloc(PyObject *obj)
 {
-	py_loader_thread_acquire();
+	const int gil_status = PyGILState_Check();
+
+	if (gil_status == 0)
+	{
+		py_loader_thread_acquire();
+	}
 
 	/* Check if we are passing our own hook to the callback */
 	if (PyCFunction_Check(obj) && PyCFunction_GET_FUNCTION(obj) == py_loader_impl_function_type_invoke)
@@ -2624,6 +2629,7 @@ static void PyCFunction_dealloc(PyObject *obj)
 
 		loader_impl_py_function_type_invoke_state invoke_state = PyCapsule_GetPointer(invoke_state_capsule, NULL);
 
+		/* Release the GIL and let the destroy be executed outside of Python (if it belongs to another language) */
 		py_loader_thread_release();
 		value_type_destroy(invoke_state->callback);
 		py_loader_thread_acquire();
@@ -2636,7 +2642,10 @@ static void PyCFunction_dealloc(PyObject *obj)
 	/* Call to the original meth_dealloc function */
 	py_loader_impl_pycfunction_dealloc(obj);
 
-	py_loader_thread_release();
+	if (gil_status == 0)
+	{
+		py_loader_thread_release();
+	}
 }
 
 loader_impl_data py_loader_impl_initialize(loader_impl impl, configuration config)
@@ -2760,10 +2769,16 @@ loader_impl_data py_loader_impl_initialize(loader_impl impl, configuration confi
 		goto error_after_import;
 	}
 
-	/* Initialize asyncio module for supporting async */
-	if (py_loader_impl_initialize_asyncio_module(py_impl, host) != 0)
+#if defined(WIN32) || defined(_WIN32)
+	/* On Windows, the initialization of this module deadlocks, we delay it to the port on this case */
+	if (host == 0)
+#endif
 	{
-		goto error_after_thread_background_module;
+		/* Initialize asyncio module for supporting async */
+		if (py_loader_impl_initialize_asyncio_module(py_impl, host) != 0)
+		{
+			goto error_after_thread_background_module;
+		}
 	}
 
 	/* Initialize custom dict type */

source/loaders/py_loader/source/py_loader_port.c

@@ -890,6 +890,26 @@ static PyObject *py_loader_port_atexit(PyObject *self, PyObject *args)
 	return Py_ReturnNone();
 }
 
+static PyObject *py_loader_port_asyncio_initialize(PyObject *self, PyObject *args)
+{
+	loader_impl impl = loader_get_impl(py_loader_tag);
+	const int host = loader_impl_get_option_host(impl);
+	loader_impl_py py_impl = loader_impl_get(impl);
+
+	(void)self;
+	(void)args;
+
+	if (impl != NULL)
+	{
+		if (py_loader_impl_initialize_asyncio_module(py_impl, host) != 0)
+		{
+			PyErr_SetString(PyExc_RuntimeErrorPtr(), "Failed to initialize asyncio module of Python Loader on MetaCall.");
+		}
+	}
+
+	return Py_ReturnNone();
+}
+
 static PyMethodDef metacall_methods[] = {
 	{ "metacall_load_from_file", py_loader_port_load_from_file, METH_VARARGS,
 		"Loads a script from file." },
@@ -913,6 +933,8 @@ static PyMethodDef metacall_methods[] = {
 		"Get the data which a value of type Pointer is pointing to." },
 	{ "py_loader_port_atexit", py_loader_port_atexit, METH_NOARGS,
 		"At exit function that will be executed when Python is host, for internal cleanup purposes." },
+	{ "py_loader_port_asyncio_initialize", py_loader_port_asyncio_initialize, METH_NOARGS,
+		"Initialization function that will be executed when Python is host, for internal initialization purposes." },
 	{ NULL, NULL, 0, NULL }
 };
 

source/loaders/py_loader/source/py_loader_threading.cpp

@@ -69,7 +69,7 @@ int py_loader_thread_initialize(const int host)
 
 	if (host == 1)
 	{
-		int gil_status = PyGILState_Check();
+		const int gil_status = PyGILState_Check();
 
 		PyGILState_STATE gstate = PyGILState_Ensure();
 		main_thread_state = PyThreadState_Get();

source/ports/py_port/metacall/api.py

@@ -95,7 +95,14 @@ def metacall_module_load():
 
 	# Python Port must have been loaded at this point
 	if 'py_port_impl_module' in sys.modules:
-		return sys.modules['py_port_impl_module']
+		port = sys.modules['py_port_impl_module']
+
+		# For some reason, Windows deadlocks on initializing asyncio
+		# but if it is delayed, it works, so we initialize it after here
+		if sys.platform == 'win32':
+			port.py_loader_port_asyncio_initialize()
+
+		return port
 	else:
 		raise ImportError(
 			'MetaCall was found but failed to load'