bpo-33694: Fix race condition in asyncio proactor (GH-7498)

The cancellation of an overlapped WSARecv() has a race condition
which causes data loss because of the current implementation of
proactor in asyncio.

No longer cancel overlapped WSARecv() in _ProactorReadPipeTransport
to work around the race condition.

Remove the optimized recv_into() implementation to get simple
implementation of pause_reading() using the single _pending_data
attribute.

Move _feed_data_to_bufferred_proto() to protocols.py.

Remove set_protocol() method which became useless.

1 files changed, 1 insertions, 20 deletions

diff --git a/Lib/asyncio/sslproto.py b/Lib/asyncio/sslproto.py
index fac2ae7..5578c6f 100644
--- a/Lib/asyncio/sslproto.py
+++ b/Lib/asyncio/sslproto.py
@@ -535,7 +535,7 @@ class SSLProtocol(protocols.Protocol):
             if chunk:
                 try:
                     if self._app_protocol_is_buffer:
-                        _feed_data_to_bufferred_proto(
+                        protocols._feed_data_to_bufferred_proto(
                             self._app_protocol, chunk)
                     else:
                         self._app_protocol.data_received(chunk)
@@ -721,22 +721,3 @@ class SSLProtocol(protocols.Protocol):
                 self._transport.abort()
         finally:
             self._finalize()
-
-
-def _feed_data_to_bufferred_proto(proto, data):
-    data_len = len(data)
-    while data_len:
-        buf = proto.get_buffer(data_len)
-        buf_len = len(buf)
-        if not buf_len:
-            raise RuntimeError('get_buffer() returned an empty buffer')
-
-        if buf_len >= data_len:
-            buf[:data_len] = data
-            proto.buffer_updated(data_len)
-            return
-        else:
-            buf[:buf_len] = data[:buf_len]
-            proto.buffer_updated(buf_len)
-            data = data[buf_len:]
-            data_len = len(data)