238 lines
8.6 KiB
Python
238 lines
8.6 KiB
Python
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"""
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Implementation of the standard :mod:`threading` using greenlets.
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.. note::
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This module is a helper for :mod:`gevent.monkey` and is not
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intended to be used directly. For spawning greenlets in your
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applications, prefer higher level constructs like
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:class:`gevent.Greenlet` class or :func:`gevent.spawn`. Attributes
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in this module like ``__threading__`` are implementation artifacts subject
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to change at any time.
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.. versionchanged:: 1.2.3
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Defer adjusting the stdlib's list of active threads until we are
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monkey patched. Previously this was done at import time. We are
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documented to only be used as a helper for monkey patching, so this should
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functionally be the same, but some applications ignore the documentation and
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directly import this module anyway.
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A positive consequence is that ``import gevent.threading,
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threading; threading.current_thread()`` will no longer return a DummyThread
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before monkey-patching.
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"""
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from __future__ import absolute_import
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__implements__ = [
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'local',
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'_start_new_thread',
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'_allocate_lock',
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'Lock',
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'_get_ident',
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'_sleep',
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'_DummyThread',
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# RLock cannot go here, even though we need to import it.
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# If it goes here, it replaces the RLock from the native
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# threading module, but we really just need it here when some
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# things import this module.
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#'RLock',
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]
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import threading as __threading__
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_DummyThread_ = __threading__._DummyThread
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from gevent.local import local
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from gevent.thread import start_new_thread as _start_new_thread
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from gevent.thread import allocate_lock as _allocate_lock
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from gevent.thread import get_ident as _get_ident
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from gevent.hub import sleep as _sleep, getcurrent
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from gevent.lock import RLock
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from gevent._util import LazyOnClass
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# Exports, prevent unused import warnings.
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# XXX: Why don't we use __all__?
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local = local
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start_new_thread = _start_new_thread
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allocate_lock = _allocate_lock
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_get_ident = _get_ident
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_sleep = _sleep
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getcurrent = getcurrent
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Lock = _allocate_lock
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RLock = RLock
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def _cleanup(g):
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__threading__._active.pop(_get_ident(g), None)
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def _make_cleanup_id(gid):
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def _(_r):
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__threading__._active.pop(gid, None)
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return _
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_weakref = None
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class _DummyThread(_DummyThread_):
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# We avoid calling the superclass constructor. This makes us about
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# twice as fast (1.16 vs 0.68usec on PyPy, 29.3 vs 17.7usec on
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# CPython 2.7), and has the important effect of avoiding
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# allocation and then immediate deletion of _Thread__block, a
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# lock. This is especially important on PyPy where locks go
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# through the cpyext API and Cython, which is known to be slow and
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# potentially buggy (e.g.,
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# https://bitbucket.org/pypy/pypy/issues/2149/memory-leak-for-python-subclass-of-cpyext#comment-22347393)
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# These objects are constructed quite frequently in some cases, so
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# the optimization matters: for example, in gunicorn, which uses
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# pywsgi.WSGIServer, most every request is handled in a new greenlet,
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# and every request uses a logging.Logger to write the access log,
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# and every call to a log method captures the current thread (by
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# default).
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#
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# (Obviously we have to duplicate the effects of the constructor,
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# at least for external state purposes, which is potentially
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# slightly fragile.)
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# For the same reason, instances of this class will cleanup their own entry
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# in ``threading._active``
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# This class also solves a problem forking process with subprocess: after forking,
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# Thread.__stop is called, which throws an exception when __block doesn't
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# exist.
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# Capture the static things as class vars to save on memory/
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# construction time.
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# In Py2, they're all private; in Py3, they become protected
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_Thread__stopped = _is_stopped = _stopped = False
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_Thread__initialized = _initialized = True
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_Thread__daemonic = _daemonic = True
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_Thread__args = _args = ()
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_Thread__kwargs = _kwargs = None
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_Thread__target = _target = None
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_Thread_ident = _ident = None
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_Thread__started = _started = __threading__.Event()
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_Thread__started.set()
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_tstate_lock = None
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def __init__(self): # pylint:disable=super-init-not-called
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#_DummyThread_.__init__(self)
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# It'd be nice to use a pattern like "greenlet-%d", but there are definitely
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# third-party libraries checking thread names to detect DummyThread objects.
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self._name = self._Thread__name = __threading__._newname("Dummy-%d")
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# All dummy threads in the same native thread share the same ident
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# (that of the native thread), unless we're monkey-patched.
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self._set_ident()
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g = getcurrent()
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gid = _get_ident(g)
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__threading__._active[gid] = self
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rawlink = getattr(g, 'rawlink', None)
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if rawlink is not None:
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# raw greenlet.greenlet greenlets don't
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# have rawlink...
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rawlink(_cleanup)
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else:
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# ... so for them we use weakrefs.
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# See https://github.com/gevent/gevent/issues/918
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ref = self.__weakref_ref
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ref = ref(g, _make_cleanup_id(gid)) # pylint:disable=too-many-function-args
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self.__raw_ref = ref
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assert self.__raw_ref is ref # prevent pylint thinking its unused
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def _Thread__stop(self):
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pass
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_stop = _Thread__stop # py3
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def _wait_for_tstate_lock(self, *args, **kwargs): # pylint:disable=signature-differs
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pass
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@LazyOnClass
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def __weakref_ref(self):
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return __import__('weakref').ref
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if hasattr(__threading__, 'main_thread'): # py 3.4+
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def main_native_thread():
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return __threading__.main_thread() # pylint:disable=no-member
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else:
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def main_native_thread():
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main_threads = [v for v in __threading__._active.values()
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if isinstance(v, __threading__._MainThread)]
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assert len(main_threads) == 1, "Too many main threads"
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return main_threads[0]
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# XXX: Issue 18808 breaks us on Python 3.4+.
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# Thread objects now expect a callback from the interpreter itself
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# (threadmodule.c:release_sentinel) when the C-level PyThreadState
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# object is being deallocated. Because this never happens
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# when a greenlet exits, join() and friends will block forever.
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# Fortunately this is easy to fix: just ensure that the allocation of the
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# lock, _set_sentinel, creates a *gevent* lock, and release it when
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# we're done. The main _shutdown code is in Python and deals with
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# this gracefully.
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class Thread(__threading__.Thread):
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def _set_tstate_lock(self):
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super(Thread, self)._set_tstate_lock()
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greenlet = getcurrent()
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greenlet.rawlink(self.__greenlet_finished)
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def __greenlet_finished(self, _):
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if self._tstate_lock:
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self._tstate_lock.release()
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self._stop()
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__implements__.append('Thread')
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class Timer(Thread, __threading__.Timer): # pylint:disable=abstract-method,inherit-non-class
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pass
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__implements__.append('Timer')
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_set_sentinel = allocate_lock
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__implements__.append('_set_sentinel')
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# The main thread is patched up with more care
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# in _gevent_will_monkey_patch
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__implements__.remove('_get_ident')
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__implements__.append('get_ident')
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get_ident = _get_ident
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__implements__.remove('_sleep')
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if hasattr(__threading__, '_CRLock'):
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# Python 3 changed the implementation of threading.RLock
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# Previously it was a factory function around threading._RLock
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# which in turn used _allocate_lock. Now, it wants to use
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# threading._CRLock, which is imported from _thread.RLock and as such
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# is implemented in C. So it bypasses our _allocate_lock function.
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# Fortunately they left the Python fallback in place and use it
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# if the imported _CRLock is None; this arranges for that to be the case.
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# This was also backported to PyPy 2.7-7.0
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_CRLock = None
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__implements__.append('_CRLock')
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def _gevent_will_monkey_patch(native_module, items, warn): # pylint:disable=unused-argument
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# Make sure the MainThread can be found by our current greenlet ID,
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# otherwise we get a new DummyThread, which cannot be joined.
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# Fixes tests in test_threading_2 under PyPy.
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main_thread = main_native_thread()
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if __threading__.current_thread() != main_thread:
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warn("Monkey-patching outside the main native thread. Some APIs "
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"will not be available. Expect a KeyError to be printed at shutdown.")
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return
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if _get_ident() not in __threading__._active:
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main_id = main_thread.ident
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del __threading__._active[main_id]
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main_thread._ident = main_thread._Thread__ident = _get_ident()
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__threading__._active[_get_ident()] = main_thread
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