Cleanup properly proactor event loop

* store the "self reading" future when the "self pipe" is closed (when the
  event loop is closed)
* store "accept" futures to cancel them when we stop serving
* close the "accept socket" if the "accept future" is cancelled

Fix many warnings which can be seen when unit tests are run in verbose mode.

Lib/asyncio/proactor_events.py

@@ -330,6 +330,8 @@ class BaseProactorEventLoop(base_events.BaseEventLoop):
         logger.debug('Using proactor: %s', proactor.__class__.__name__)
         self._proactor = proactor
         self._selector = proactor   # convenient alias
+        self._self_reading_future = None
+        self._accept_futures = {}   # socket file descriptor => Future
         proactor.set_loop(self)
         self._make_self_pipe()
 
@@ -365,6 +367,7 @@ class BaseProactorEventLoop(base_events.BaseEventLoop):
             self._proactor = None
             self._selector = None
             super().close()
+        self._accept_futures.clear()
 
     def sock_recv(self, sock, n):
         return self._proactor.recv(sock, n)
@@ -382,6 +385,9 @@ class BaseProactorEventLoop(base_events.BaseEventLoop):
         raise NotImplementedError
 
     def _close_self_pipe(self):
+        if self._self_reading_future is not None:
+            self._self_reading_future.cancel()
+            self._self_reading_future = None
         self._ssock.close()
         self._ssock = None
         self._csock.close()
@@ -405,6 +411,7 @@ class BaseProactorEventLoop(base_events.BaseEventLoop):
             self.close()
             raise
         else:
+            self._self_reading_future = f
             f.add_done_callback(self._loop_self_reading)
 
     def _write_to_self(self):
@@ -430,6 +437,7 @@ class BaseProactorEventLoop(base_events.BaseEventLoop):
             except futures.CancelledError:
                 sock.close()
             else:
+                self._accept_futures[sock.fileno()] = f
                 f.add_done_callback(loop)
 
         self.call_soon(loop)
@@ -438,5 +446,7 @@ class BaseProactorEventLoop(base_events.BaseEventLoop):
         pass    # XXX hard work currently done in poll
 
     def _stop_serving(self, sock):
+        for future in self._accept_futures.values():
+            future.cancel()
         self._proactor._stop_serving(sock)
         sock.close()

Lib/asyncio/windows_events.py

@@ -168,9 +168,6 @@ class ProactorEventLoop(proactor_events.BaseProactorEventLoop):
         self.call_soon(loop)
         return [server]
 
-    def _stop_serving(self, server):
-        server.close()
-
     @tasks.coroutine
     def _make_subprocess_transport(self, protocol, args, shell,
                                    stdin, stdout, stderr, bufsize,
@@ -260,7 +257,19 @@ class IocpProactor:
             conn.settimeout(listener.gettimeout())
             return conn, conn.getpeername()
 
-        return self._register(ov, listener, finish_accept)
+        @tasks.coroutine
+        def accept_coro(future, conn):
+            # Coroutine closing the accept socket if the future is cancelled
+            try:
+                yield from future
+            except futures.CancelledError:
+                conn.close()
+                raise
+
+        future = self._register(ov, listener, finish_accept)
+        coro = accept_coro(future, conn)
+        tasks.async(coro, loop=self._loop)
+        return future
 
     def connect(self, conn, address):
         self._register_with_iocp(conn)