""" Implementation of the standard :mod:`threading` using greenlets. .. note:: 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 before monkey-patching. """ from __future__ import absolute_import __implements__ = [ 'local', '_start_new_thread', '_allocate_lock', 'Lock', '_get_ident', '_sleep', '_DummyThread', # 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. #'RLock', ] 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 def _cleanup(g): __threading__._active.pop(_get_ident(g), None) def _make_cleanup_id(gid): def _(_r): __threading__._active.pop(gid, None) return _ _weakref = None class _DummyThread(_DummyThread_): # 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., # https://bitbucket.org/pypy/pypy/issues/2149/memory-leak-for-python-subclass-of-cpyext#comment-22347393) # 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 # default). # # (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 # exist. # 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() _Thread__started.set() _tstate_lock = None def __init__(self): # pylint:disable=super-init-not-called #_DummyThread_.__init__(self) # 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. self._set_ident() 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... rawlink(_cleanup) else: # ... 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 def _Thread__stop(self): pass _stop = _Thread__stop # py3 def _wait_for_tstate_lock(self, *args, **kwargs): # pylint:disable=signature-differs pass @LazyOnClass def __weakref_ref(self): return __import__('weakref').ref if hasattr(__threading__, 'main_thread'): # py 3.4+ def main_native_thread(): return __threading__.main_thread() # pylint:disable=no-member else: def main_native_thread(): main_threads = [v for v in __threading__._active.values() if isinstance(v, __threading__._MainThread)] assert len(main_threads) == 1, "Too many main threads" return main_threads[0] # 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. class Thread(__threading__.Thread): def _set_tstate_lock(self): super(Thread, self)._set_tstate_lock() greenlet = getcurrent() greenlet.rawlink(self.__greenlet_finished) def __greenlet_finished(self, _): if self._tstate_lock: self._tstate_lock.release() self._stop() __implements__.append('Thread') class Timer(Thread, __threading__.Timer): # pylint:disable=abstract-method,inherit-non-class pass __implements__.append('Timer') _set_sentinel = allocate_lock __implements__.append('_set_sentinel') # The main thread is patched up with more care # in _gevent_will_monkey_patch __implements__.remove('_get_ident') __implements__.append('get_ident') get_ident = _get_ident __implements__.remove('_sleep') 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 __implements__.append('_CRLock') 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.") return if _get_ident() not in __threading__._active: main_id = main_thread.ident del __threading__._active[main_id] main_thread._ident = main_thread._Thread__ident = _get_ident() __threading__._active[_get_ident()] = main_thread