Implementation of the standard :mod:`threading` using greenlets.
This module is a helper for :mod:`gevent.monkey` and is not
intended to be used directly. For spawning greenlets in your
applications, prefer higher level constructs like
:class:`gevent.Greenlet` class or :func:`gevent.spawn`. Attributes
in this module like ``__threading__`` are implementation artifacts subject
to change at any time.
.. versionchanged:: 1.2.3
Defer adjusting the stdlib's list of active threads until we are
monkey patched. Previously this was done at import time. We are
documented to only be used as a helper for monkey patching, so this should
functionally be the same, but some applications ignore the documentation and
directly import this module anyway.
A positive consequence is that ``import gevent.threading,
threading; threading.current_thread()`` will no longer return a DummyThread
from __future__ import absolute_import
__implements__ = [
# RLock cannot go here, even though we need to import it.
# If it goes here, it replaces the RLock from the native
# threading module, but we really just need it here when some
# things import this module.
import threading as __threading__
_DummyThread_ = __threading__._DummyThread
from gevent.local import local
from gevent.thread import start_new_thread as _start_new_thread
from gevent.thread import allocate_lock as _allocate_lock
from gevent.thread import get_ident as _get_ident
from gevent.hub import sleep as _sleep, getcurrent
from gevent.lock import RLock
from gevent._util import LazyOnClass
# Exports, prevent unused import warnings.
# XXX: Why don't we use __all__?
local = local
start_new_thread = _start_new_thread
allocate_lock = _allocate_lock
_get_ident = _get_ident
_sleep = _sleep
getcurrent = getcurrent
Lock = _allocate_lock
RLock = RLock
_weakref = None
# We avoid calling the superclass constructor. This makes us about
# twice as fast (1.16 vs 0.68usec on PyPy, 29.3 vs 17.7usec on
# CPython 2.7), and has the important effect of avoiding
# allocation and then immediate deletion of _Thread__block, a
# lock. This is especially important on PyPy where locks go
# through the cpyext API and Cython, which is known to be slow and
# potentially buggy (e.g.,
# These objects are constructed quite frequently in some cases, so
# the optimization matters: for example, in gunicorn, which uses
# pywsgi.WSGIServer, most every request is handled in a new greenlet,
# and every request uses a logging.Logger to write the access log,
# and every call to a log method captures the current thread (by
# (Obviously we have to duplicate the effects of the constructor,
# at least for external state purposes, which is potentially
# slightly fragile.)
# For the same reason, instances of this class will cleanup their own entry
# in ``threading._active``
# This class also solves a problem forking process with subprocess: after forking,
# Thread.__stop is called, which throws an exception when __block doesn't
# Capture the static things as class vars to save on memory/
# construction time.
# In Py2, they're all private; in Py3, they become protected
_Thread__stopped = _is_stopped = _stopped = False
_Thread__initialized = _initialized = True
_Thread__daemonic = _daemonic = True
_Thread__args = _args = ()
_Thread__kwargs = _kwargs = None
_Thread__target = _target = None
_Thread_ident = _ident = None
_Thread__started = _started = __threading__.Event()
_tstate_lock = None
def __init__(self): # pylint:disable=super-init-not-called
# It'd be nice to use a pattern like "greenlet-%d", but there are definitely
# third-party libraries checking thread names to detect DummyThread objects.
self._name = self._Thread__name = __threading__._newname("Dummy-%d")
# All dummy threads in the same native thread share the same ident
# (that of the native thread), unless we're monkey-patched.
g = getcurrent()
gid = _get_ident(g)
__threading__._active[gid] = self
rawlink = getattr(g, 'rawlink', None)
if rawlink is not None:
# raw greenlet.greenlet greenlets don't
# have rawlink...
# ... so for them we use weakrefs.
# See https://github.com/gevent/gevent/issues/918
ref = self.__weakref_ref
ref = ref(g, _make_cleanup_id(gid)) # pylint:disable=too-many-function-args
self.__raw_ref = ref
assert self.__raw_ref is ref # prevent pylint thinking its unused
_stop = _Thread__stop # py3
def _wait_for_tstate_lock(self, *args, **kwargs): # pylint:disable=signature-differs
if hasattr(__threading__, 'main_thread'): # py 3.4+
return __threading__.main_thread() # pylint:disable=no-member
main_threads = [v for v in __threading__._active.values()
if isinstance(v, __threading__._MainThread)]
assert len(main_threads) == 1, "Too many main threads"
# XXX: Issue 18808 breaks us on Python 3.4+.
# Thread objects now expect a callback from the interpreter itself
# (threadmodule.c:release_sentinel) when the C-level PyThreadState
# object is being deallocated. Because this never happens
# when a greenlet exits, join() and friends will block forever.
# Fortunately this is easy to fix: just ensure that the allocation of the
# lock, _set_sentinel, creates a *gevent* lock, and release it when
# we're done. The main _shutdown code is in Python and deals with
# this gracefully.
greenlet = getcurrent()
def __greenlet_finished(self, _):
class Timer(Thread, __threading__.Timer): # pylint:disable=abstract-method,inherit-non-class
_set_sentinel = allocate_lock
# The main thread is patched up with more care
# in _gevent_will_monkey_patch
get_ident = _get_ident
if hasattr(__threading__, '_CRLock'):
# Python 3 changed the implementation of threading.RLock
# Previously it was a factory function around threading._RLock
# which in turn used _allocate_lock. Now, it wants to use
# threading._CRLock, which is imported from _thread.RLock and as such
# is implemented in C. So it bypasses our _allocate_lock function.
# Fortunately they left the Python fallback in place and use it
# if the imported _CRLock is None; this arranges for that to be the case.
# This was also backported to PyPy 2.7-7.0
_CRLock = None
def _gevent_will_monkey_patch(native_module, items, warn): # pylint:disable=unused-argument
# Make sure the MainThread can be found by our current greenlet ID,
# otherwise we get a new DummyThread, which cannot be joined.
# Fixes tests in test_threading_2 under PyPy.
main_thread = main_native_thread()
if __threading__.current_thread() != main_thread:
warn("Monkey-patching outside the main native thread. Some APIs "
"will not be available. Expect a KeyError to be printed at shutdown.")
if _get_ident() not in __threading__._active:
main_id = main_thread.ident
main_thread._ident = main_thread._Thread__ident = _get_ident()
__threading__._active[_get_ident()] = main_thread