Merge pull request #10188 from kpayson64/another_gil_fix

Initialize GIL at startup

src/python/grpcio/grpc/_cython/cygrpc.pyx

@@ -47,14 +47,14 @@ include "_cygrpc/server.pyx.pxi"
 #
 # initialize gRPC
 #
-
-
 cdef extern from "Python.h":
 
-  int Py_AtExit(void(*func)())
-
+  int PyEval_InitThreads()
 
-def _initialize():
+cdef _initialize():
+  # We have Python callbacks called by c-core threads, this ensures the GIL
+  # is initialized.
+  PyEval_InitThreads()
   grpc_set_ssl_roots_override_callback(
           <grpc_ssl_roots_override_callback>ssl_roots_override_callback)