fix(mge/distributed): fix deadlock by mixing thread and fork

GitOrigin-RevId: c138cb9c280aeb37d83d2ca31549df0661ebbbc9

imperative/python/megengine/distributed/launcher.py

@@ -12,7 +12,7 @@ import multiprocessing as mp
 from ..core._imperative_rt.core2 import sync
 from .group import group_barrier, init_process_group
 from .helper import get_device_count_by_fork
-from .server import Server
+from .server import Client, Server
 from .util import get_free_ports
 
 

imperative/python/megengine/distributed/server.py

@@ -6,11 +6,11 @@
 # Unless required by applicable law or agreed to in writing,
 # software distributed under the License is distributed on an
 # "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+import multiprocessing as mp
 import threading
 import time
 from collections import defaultdict
 from functools import partial
-from queue import Queue
 from socketserver import ThreadingMixIn
 from xmlrpc.client import ServerProxy
 from xmlrpc.server import SimpleXMLRPCServer
@@ -133,7 +133,7 @@ class ThreadXMLRPCServer(ThreadingMixIn, SimpleXMLRPCServer):
     pass
 
 
-def _start_server(py_server_port, mm_server_port, queue):
+def _start_server(py_server_port, queue):
     """
     Start python distributed server and multiple machine server.
 
@@ -142,10 +142,11 @@ def _start_server(py_server_port, mm_server_port, queue):
     :param queue: server port will put in this queue, puts exception when process fails.
     """
     try:
+        mm_server_port = create_mm_server("0.0.0.0", 0)
         server = ThreadXMLRPCServer(("0.0.0.0", py_server_port), logRequests=False)
         server.register_instance(Methods(mm_server_port))
-        _, port = server.server_address
-        queue.put(port)
+        _, py_server_port = server.server_address
+        queue.put((py_server_port, mm_server_port))
         server.serve_forever()
     except Exception as e:
         queue.put(e)
@@ -160,17 +161,17 @@ class Server:
     """
 
     def __init__(self, port=0):
-        self.mm_server_port = create_mm_server("0.0.0.0", 0)
-        q = Queue()
-        self.proc = threading.Thread(
-            target=_start_server, args=(port, self.mm_server_port, q), daemon=True,
-        )
+        q = mp.Queue()
+        self.proc = mp.Process(target=_start_server, args=(port, q), daemon=True)
         self.proc.start()
         ret = q.get()
         if isinstance(ret, Exception):
             raise ret
         else:
-            self.py_server_port = ret
+            self.py_server_port, self.mm_server_port = ret
+
+    def __del__(self):
+        self.proc.terminate()
 
 
 class Client: