Make sure multiple add_reader/add_writer calls manage refs correctly

Author: 1st1

tests/test_sockets.py

@@ -564,6 +564,48 @@ async def client(sock, addr):
                 w = asyncio.wait_for(c, timeout=5.0, loop=self.loop)
                 self.loop.run_until_complete(w)
 
+    def test_socket_close_many_add_readers(self):
+        s = socket.socket()
+        with s:
+            s.setblocking(False)
+            self.loop.add_reader(s, lambda: None)
+            self.loop.add_reader(s, lambda: None)
+            self.loop.add_reader(s, lambda: None)
+            self.loop.remove_reader(s.fileno())
+            s.close()
+            self.assertEqual(s.fileno(), -1)
+
+        s = socket.socket()
+        with s:
+            s.setblocking(False)
+            self.loop.add_reader(s, lambda: None)
+            self.loop.add_reader(s, lambda: None)
+            self.loop.add_reader(s, lambda: None)
+            self.loop.remove_reader(s)
+            s.close()
+            self.assertEqual(s.fileno(), -1)
+
+    def test_socket_close_many_remove_writers(self):
+        s = socket.socket()
+        with s:
+            s.setblocking(False)
+            self.loop.add_writer(s, lambda: None)
+            self.loop.add_writer(s, lambda: None)
+            self.loop.add_writer(s, lambda: None)
+            self.loop.remove_writer(s.fileno())
+            s.close()
+            self.assertEqual(s.fileno(), -1)
+
+        s = socket.socket()
+        with s:
+            s.setblocking(False)
+            self.loop.add_writer(s, lambda: None)
+            self.loop.add_writer(s, lambda: None)
+            self.loop.add_writer(s, lambda: None)
+            self.loop.remove_writer(s)
+            s.close()
+            self.assertEqual(s.fileno(), -1)
+
 
 class TestAIOSockets(_TestSockets, tb.AIOTestCase):
     pass

uvloop/loop.pyx

@@ -666,6 +666,10 @@ cdef class Loop:
 
         poll.start_reading(handle)
 
+        old_fileobj = self._fd_to_reader_fileobj.pop(fd, None)
+        if old_fileobj is not None:
+            socket_dec_io_ref(old_fileobj)
+
         self._fd_to_reader_fileobj[fd] = fileobj
         socket_inc_io_ref(fileobj)
 
@@ -711,6 +715,10 @@ cdef class Loop:
 
         poll.start_writing(handle)
 
+        old_fileobj = self._fd_to_writer_fileobj.pop(fd, None)
+        if old_fileobj is not None:
+            socket_dec_io_ref(old_fileobj)
+
         self._fd_to_writer_fileobj[fd] = fileobj
         socket_inc_io_ref(fileobj)