cpython/Lib/asyncio/proactor_events.py
CtrlZvi 4151061855 bpo-26819: Prevent proactor double read on resume (#6921)
The proactor event loop has a race condition when reading with
pausing/resuming. `resume_reading()` unconditionally schedules the read
function to read from the current future. If `resume_reading()` was
called before the previously scheduled done callback fires, this results
in two attempts to get the data from the most recent read and an
assertion failure. This commit tracks whether or not `resume_reading`
needs to reschedule the callback to restart the loop, preventing a
second attempt to read the data.
2018-05-20 13:21:10 +03:00

730 lines
26 KiB
Python

"""Event loop using a proactor and related classes.
A proactor is a "notify-on-completion" multiplexer. Currently a
proactor is only implemented on Windows with IOCP.
"""
__all__ = 'BaseProactorEventLoop',
import io
import os
import socket
import warnings
from . import base_events
from . import constants
from . import events
from . import futures
from . import protocols
from . import sslproto
from . import transports
from .log import logger
class _ProactorBasePipeTransport(transports._FlowControlMixin,
transports.BaseTransport):
"""Base class for pipe and socket transports."""
def __init__(self, loop, sock, protocol, waiter=None,
extra=None, server=None):
super().__init__(extra, loop)
self._set_extra(sock)
self._sock = sock
self._protocol = protocol
self._server = server
self._buffer = None # None or bytearray.
self._read_fut = None
self._write_fut = None
self._pending_write = 0
self._conn_lost = 0
self._closing = False # Set when close() called.
self._eof_written = False
if self._server is not None:
self._server._attach()
self._loop.call_soon(self._protocol.connection_made, self)
if waiter is not None:
# only wake up the waiter when connection_made() has been called
self._loop.call_soon(futures._set_result_unless_cancelled,
waiter, None)
def __repr__(self):
info = [self.__class__.__name__]
if self._sock is None:
info.append('closed')
elif self._closing:
info.append('closing')
if self._sock is not None:
info.append(f'fd={self._sock.fileno()}')
if self._read_fut is not None:
info.append(f'read={self._read_fut!r}')
if self._write_fut is not None:
info.append(f'write={self._write_fut!r}')
if self._buffer:
info.append(f'write_bufsize={len(self._buffer)}')
if self._eof_written:
info.append('EOF written')
return '<{}>'.format(' '.join(info))
def _set_extra(self, sock):
self._extra['pipe'] = sock
def set_protocol(self, protocol):
self._protocol = protocol
def get_protocol(self):
return self._protocol
def is_closing(self):
return self._closing
def close(self):
if self._closing:
return
self._closing = True
self._conn_lost += 1
if not self._buffer and self._write_fut is None:
self._loop.call_soon(self._call_connection_lost, None)
if self._read_fut is not None:
self._read_fut.cancel()
self._read_fut = None
def __del__(self):
if self._sock is not None:
warnings.warn(f"unclosed transport {self!r}", ResourceWarning,
source=self)
self.close()
def _fatal_error(self, exc, message='Fatal error on pipe transport'):
try:
if isinstance(exc, base_events._FATAL_ERROR_IGNORE):
if self._loop.get_debug():
logger.debug("%r: %s", self, message, exc_info=True)
else:
self._loop.call_exception_handler({
'message': message,
'exception': exc,
'transport': self,
'protocol': self._protocol,
})
finally:
self._force_close(exc)
def _force_close(self, exc):
if self._empty_waiter is not None:
if exc is None:
self._empty_waiter.set_result(None)
else:
self._empty_waiter.set_exception(exc)
if self._closing:
return
self._closing = True
self._conn_lost += 1
if self._write_fut:
self._write_fut.cancel()
self._write_fut = None
if self._read_fut:
self._read_fut.cancel()
self._read_fut = None
self._pending_write = 0
self._buffer = None
self._loop.call_soon(self._call_connection_lost, exc)
def _call_connection_lost(self, exc):
try:
self._protocol.connection_lost(exc)
finally:
# XXX If there is a pending overlapped read on the other
# end then it may fail with ERROR_NETNAME_DELETED if we
# just close our end. First calling shutdown() seems to
# cure it, but maybe using DisconnectEx() would be better.
if hasattr(self._sock, 'shutdown'):
self._sock.shutdown(socket.SHUT_RDWR)
self._sock.close()
self._sock = None
server = self._server
if server is not None:
server._detach()
self._server = None
def get_write_buffer_size(self):
size = self._pending_write
if self._buffer is not None:
size += len(self._buffer)
return size
class _ProactorReadPipeTransport(_ProactorBasePipeTransport,
transports.ReadTransport):
"""Transport for read pipes."""
def __init__(self, loop, sock, protocol, waiter=None,
extra=None, server=None):
super().__init__(loop, sock, protocol, waiter, extra, server)
self._paused = False
self._reschedule_on_resume = False
if protocols._is_buffered_protocol(protocol):
self._loop_reading = self._loop_reading__get_buffer
else:
self._loop_reading = self._loop_reading__data_received
self._loop.call_soon(self._loop_reading)
def is_reading(self):
return not self._paused and not self._closing
def pause_reading(self):
if self._closing or self._paused:
return
self._paused = True
if self._read_fut is not None and not self._read_fut.done():
self._read_fut.cancel()
self._read_fut = None
self._reschedule_on_resume = True
if self._loop.get_debug():
logger.debug("%r pauses reading", self)
def resume_reading(self):
if self._closing or not self._paused:
return
self._paused = False
if self._reschedule_on_resume:
self._loop.call_soon(self._loop_reading, self._read_fut)
self._reschedule_on_resume = False
if self._loop.get_debug():
logger.debug("%r resumes reading", self)
def _loop_reading__on_eof(self):
if self._loop.get_debug():
logger.debug("%r received EOF", self)
try:
keep_open = self._protocol.eof_received()
except Exception as exc:
self._fatal_error(
exc, 'Fatal error: protocol.eof_received() call failed.')
return
if not keep_open:
self.close()
def _loop_reading__data_received(self, fut=None):
if self._paused:
self._reschedule_on_resume = True
return
data = None
try:
if fut is not None:
assert self._read_fut is fut or (self._read_fut is None and
self._closing)
self._read_fut = None
if fut.done():
# deliver data later in "finally" clause
data = fut.result()
else:
# the future will be replaced by next proactor.recv call
fut.cancel()
if self._closing:
# since close() has been called we ignore any read data
data = None
return
if data == b'':
# we got end-of-file so no need to reschedule a new read
return
# reschedule a new read
self._read_fut = self._loop._proactor.recv(self._sock, 32768)
except ConnectionAbortedError as exc:
if not self._closing:
self._fatal_error(exc, 'Fatal read error on pipe transport')
elif self._loop.get_debug():
logger.debug("Read error on pipe transport while closing",
exc_info=True)
except ConnectionResetError as exc:
self._force_close(exc)
except OSError as exc:
self._fatal_error(exc, 'Fatal read error on pipe transport')
except futures.CancelledError:
if not self._closing:
raise
else:
self._read_fut.add_done_callback(self._loop_reading)
finally:
if data:
self._protocol.data_received(data)
elif data == b'':
self._loop_reading__on_eof()
def _loop_reading__get_buffer(self, fut=None):
if self._paused:
self._reschedule_on_resume = True
return
nbytes = None
if fut is not None:
assert self._read_fut is fut or (self._read_fut is None and
self._closing)
self._read_fut = None
try:
if fut.done():
nbytes = fut.result()
else:
# the future will be replaced by next proactor.recv call
fut.cancel()
except ConnectionAbortedError as exc:
if not self._closing:
self._fatal_error(
exc, 'Fatal read error on pipe transport')
elif self._loop.get_debug():
logger.debug("Read error on pipe transport while closing",
exc_info=True)
except ConnectionResetError as exc:
self._force_close(exc)
except OSError as exc:
self._fatal_error(exc, 'Fatal read error on pipe transport')
except futures.CancelledError:
if not self._closing:
raise
if nbytes is not None:
if nbytes == 0:
# we got end-of-file so no need to reschedule a new read
self._loop_reading__on_eof()
else:
try:
self._protocol.buffer_updated(nbytes)
except Exception as exc:
self._fatal_error(
exc,
'Fatal error: '
'protocol.buffer_updated() call failed.')
return
if self._closing or nbytes == 0:
# since close() has been called we ignore any read data
return
try:
buf = self._protocol.get_buffer()
except Exception as exc:
self._fatal_error(
exc, 'Fatal error: protocol.get_buffer() call failed.')
return
try:
# schedule a new read
self._read_fut = self._loop._proactor.recv_into(self._sock, buf)
self._read_fut.add_done_callback(self._loop_reading)
except ConnectionAbortedError as exc:
if not self._closing:
self._fatal_error(exc, 'Fatal read error on pipe transport')
elif self._loop.get_debug():
logger.debug("Read error on pipe transport while closing",
exc_info=True)
except ConnectionResetError as exc:
self._force_close(exc)
except OSError as exc:
self._fatal_error(exc, 'Fatal read error on pipe transport')
except futures.CancelledError:
if not self._closing:
raise
class _ProactorBaseWritePipeTransport(_ProactorBasePipeTransport,
transports.WriteTransport):
"""Transport for write pipes."""
_start_tls_compatible = True
def __init__(self, *args, **kw):
super().__init__(*args, **kw)
self._empty_waiter = None
def write(self, data):
if not isinstance(data, (bytes, bytearray, memoryview)):
raise TypeError(
f"data argument must be a bytes-like object, "
f"not {type(data).__name__}")
if self._eof_written:
raise RuntimeError('write_eof() already called')
if self._empty_waiter is not None:
raise RuntimeError('unable to write; sendfile is in progress')
if not data:
return
if self._conn_lost:
if self._conn_lost >= constants.LOG_THRESHOLD_FOR_CONNLOST_WRITES:
logger.warning('socket.send() raised exception.')
self._conn_lost += 1
return
# Observable states:
# 1. IDLE: _write_fut and _buffer both None
# 2. WRITING: _write_fut set; _buffer None
# 3. BACKED UP: _write_fut set; _buffer a bytearray
# We always copy the data, so the caller can't modify it
# while we're still waiting for the I/O to happen.
if self._write_fut is None: # IDLE -> WRITING
assert self._buffer is None
# Pass a copy, except if it's already immutable.
self._loop_writing(data=bytes(data))
elif not self._buffer: # WRITING -> BACKED UP
# Make a mutable copy which we can extend.
self._buffer = bytearray(data)
self._maybe_pause_protocol()
else: # BACKED UP
# Append to buffer (also copies).
self._buffer.extend(data)
self._maybe_pause_protocol()
def _loop_writing(self, f=None, data=None):
try:
assert f is self._write_fut
self._write_fut = None
self._pending_write = 0
if f:
f.result()
if data is None:
data = self._buffer
self._buffer = None
if not data:
if self._closing:
self._loop.call_soon(self._call_connection_lost, None)
if self._eof_written:
self._sock.shutdown(socket.SHUT_WR)
# Now that we've reduced the buffer size, tell the
# protocol to resume writing if it was paused. Note that
# we do this last since the callback is called immediately
# and it may add more data to the buffer (even causing the
# protocol to be paused again).
self._maybe_resume_protocol()
else:
self._write_fut = self._loop._proactor.send(self._sock, data)
if not self._write_fut.done():
assert self._pending_write == 0
self._pending_write = len(data)
self._write_fut.add_done_callback(self._loop_writing)
self._maybe_pause_protocol()
else:
self._write_fut.add_done_callback(self._loop_writing)
if self._empty_waiter is not None and self._write_fut is None:
self._empty_waiter.set_result(None)
except ConnectionResetError as exc:
self._force_close(exc)
except OSError as exc:
self._fatal_error(exc, 'Fatal write error on pipe transport')
def can_write_eof(self):
return True
def write_eof(self):
self.close()
def abort(self):
self._force_close(None)
def _make_empty_waiter(self):
if self._empty_waiter is not None:
raise RuntimeError("Empty waiter is already set")
self._empty_waiter = self._loop.create_future()
if self._write_fut is None:
self._empty_waiter.set_result(None)
return self._empty_waiter
def _reset_empty_waiter(self):
self._empty_waiter = None
class _ProactorWritePipeTransport(_ProactorBaseWritePipeTransport):
def __init__(self, *args, **kw):
super().__init__(*args, **kw)
self._read_fut = self._loop._proactor.recv(self._sock, 16)
self._read_fut.add_done_callback(self._pipe_closed)
def _pipe_closed(self, fut):
if fut.cancelled():
# the transport has been closed
return
assert fut.result() == b''
if self._closing:
assert self._read_fut is None
return
assert fut is self._read_fut, (fut, self._read_fut)
self._read_fut = None
if self._write_fut is not None:
self._force_close(BrokenPipeError())
else:
self.close()
class _ProactorDuplexPipeTransport(_ProactorReadPipeTransport,
_ProactorBaseWritePipeTransport,
transports.Transport):
"""Transport for duplex pipes."""
def can_write_eof(self):
return False
def write_eof(self):
raise NotImplementedError
class _ProactorSocketTransport(_ProactorReadPipeTransport,
_ProactorBaseWritePipeTransport,
transports.Transport):
"""Transport for connected sockets."""
_sendfile_compatible = constants._SendfileMode.TRY_NATIVE
def _set_extra(self, sock):
self._extra['socket'] = sock
try:
self._extra['sockname'] = sock.getsockname()
except (socket.error, AttributeError):
if self._loop.get_debug():
logger.warning(
"getsockname() failed on %r", sock, exc_info=True)
if 'peername' not in self._extra:
try:
self._extra['peername'] = sock.getpeername()
except (socket.error, AttributeError):
if self._loop.get_debug():
logger.warning("getpeername() failed on %r",
sock, exc_info=True)
def can_write_eof(self):
return True
def write_eof(self):
if self._closing or self._eof_written:
return
self._eof_written = True
if self._write_fut is None:
self._sock.shutdown(socket.SHUT_WR)
class BaseProactorEventLoop(base_events.BaseEventLoop):
def __init__(self, proactor):
super().__init__()
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()
def _make_socket_transport(self, sock, protocol, waiter=None,
extra=None, server=None):
return _ProactorSocketTransport(self, sock, protocol, waiter,
extra, server)
def _make_ssl_transport(
self, rawsock, protocol, sslcontext, waiter=None,
*, server_side=False, server_hostname=None,
extra=None, server=None,
ssl_handshake_timeout=None):
ssl_protocol = sslproto.SSLProtocol(
self, protocol, sslcontext, waiter,
server_side, server_hostname,
ssl_handshake_timeout=ssl_handshake_timeout)
_ProactorSocketTransport(self, rawsock, ssl_protocol,
extra=extra, server=server)
return ssl_protocol._app_transport
def _make_duplex_pipe_transport(self, sock, protocol, waiter=None,
extra=None):
return _ProactorDuplexPipeTransport(self,
sock, protocol, waiter, extra)
def _make_read_pipe_transport(self, sock, protocol, waiter=None,
extra=None):
return _ProactorReadPipeTransport(self, sock, protocol, waiter, extra)
def _make_write_pipe_transport(self, sock, protocol, waiter=None,
extra=None):
# We want connection_lost() to be called when other end closes
return _ProactorWritePipeTransport(self,
sock, protocol, waiter, extra)
def close(self):
if self.is_running():
raise RuntimeError("Cannot close a running event loop")
if self.is_closed():
return
# Call these methods before closing the event loop (before calling
# BaseEventLoop.close), because they can schedule callbacks with
# call_soon(), which is forbidden when the event loop is closed.
self._stop_accept_futures()
self._close_self_pipe()
self._proactor.close()
self._proactor = None
self._selector = None
# Close the event loop
super().close()
async def sock_recv(self, sock, n):
return await self._proactor.recv(sock, n)
async def sock_recv_into(self, sock, buf):
return await self._proactor.recv_into(sock, buf)
async def sock_sendall(self, sock, data):
return await self._proactor.send(sock, data)
async def sock_connect(self, sock, address):
return await self._proactor.connect(sock, address)
async def sock_accept(self, sock):
return await self._proactor.accept(sock)
async def _sock_sendfile_native(self, sock, file, offset, count):
try:
fileno = file.fileno()
except (AttributeError, io.UnsupportedOperation) as err:
raise events.SendfileNotAvailableError("not a regular file")
try:
fsize = os.fstat(fileno).st_size
except OSError as err:
raise events.SendfileNotAvailableError("not a regular file")
blocksize = count if count else fsize
if not blocksize:
return 0 # empty file
blocksize = min(blocksize, 0xffff_ffff)
end_pos = min(offset + count, fsize) if count else fsize
offset = min(offset, fsize)
total_sent = 0
try:
while True:
blocksize = min(end_pos - offset, blocksize)
if blocksize <= 0:
return total_sent
await self._proactor.sendfile(sock, file, offset, blocksize)
offset += blocksize
total_sent += blocksize
finally:
if total_sent > 0:
file.seek(offset)
async def _sendfile_native(self, transp, file, offset, count):
resume_reading = transp.is_reading()
transp.pause_reading()
await transp._make_empty_waiter()
try:
return await self.sock_sendfile(transp._sock, file, offset, count,
fallback=False)
finally:
transp._reset_empty_waiter()
if resume_reading:
transp.resume_reading()
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()
self._csock = None
self._internal_fds -= 1
def _make_self_pipe(self):
# A self-socket, really. :-)
self._ssock, self._csock = socket.socketpair()
self._ssock.setblocking(False)
self._csock.setblocking(False)
self._internal_fds += 1
self.call_soon(self._loop_self_reading)
def _loop_self_reading(self, f=None):
try:
if f is not None:
f.result() # may raise
f = self._proactor.recv(self._ssock, 4096)
except futures.CancelledError:
# _close_self_pipe() has been called, stop waiting for data
return
except Exception as exc:
self.call_exception_handler({
'message': 'Error on reading from the event loop self pipe',
'exception': exc,
'loop': self,
})
else:
self._self_reading_future = f
f.add_done_callback(self._loop_self_reading)
def _write_to_self(self):
self._csock.send(b'\0')
def _start_serving(self, protocol_factory, sock,
sslcontext=None, server=None, backlog=100,
ssl_handshake_timeout=None):
def loop(f=None):
try:
if f is not None:
conn, addr = f.result()
if self._debug:
logger.debug("%r got a new connection from %r: %r",
server, addr, conn)
protocol = protocol_factory()
if sslcontext is not None:
self._make_ssl_transport(
conn, protocol, sslcontext, server_side=True,
extra={'peername': addr}, server=server,
ssl_handshake_timeout=ssl_handshake_timeout)
else:
self._make_socket_transport(
conn, protocol,
extra={'peername': addr}, server=server)
if self.is_closed():
return
f = self._proactor.accept(sock)
except OSError as exc:
if sock.fileno() != -1:
self.call_exception_handler({
'message': 'Accept failed on a socket',
'exception': exc,
'socket': sock,
})
sock.close()
elif self._debug:
logger.debug("Accept failed on socket %r",
sock, exc_info=True)
except futures.CancelledError:
sock.close()
else:
self._accept_futures[sock.fileno()] = f
f.add_done_callback(loop)
self.call_soon(loop)
def _process_events(self, event_list):
# Events are processed in the IocpProactor._poll() method
pass
def _stop_accept_futures(self):
for future in self._accept_futures.values():
future.cancel()
self._accept_futures.clear()
def _stop_serving(self, sock):
future = self._accept_futures.pop(sock.fileno(), None)
if future:
future.cancel()
self._proactor._stop_serving(sock)
sock.close()