Lib/threading.py

   1 """Thread module emulating a subset of Java's threading model."""
   2
   3 import sys as _sys
   4
   5 try:
   6     import thread
   7 except ImportError:
   8     del _sys.modules[__name__]
   9     raise
  10
  11 import warnings
  12
  13 from functools import wraps
  14 from time import time as _time, sleep as _sleep
  15 from traceback import format_exc as _format_exc
  16 from collections import deque
  17
  18 # Rename some stuff so "from threading import *" is safe
  19 __all__ = ['activeCount', 'active_count', 'Condition', 'currentThread',
  20            'current_thread', 'enumerate', 'Event',
  21            'Lock', 'RLock', 'Semaphore', 'BoundedSemaphore', 'Thread',
  22            'Timer', 'setprofile', 'settrace', 'local', 'stack_size']
  23
  24 _start_new_thread = thread.start_new_thread
  25 _allocate_lock = thread.allocate_lock
  26 _get_ident = thread.get_ident
  27 ThreadError = thread.error
  28 del thread
  29
  30
  31 # sys.exc_clear is used to work around the fact that except blocks
  32 # don't fully clear the exception until 3.0.
  33 warnings.filterwarnings('ignore', category=DeprecationWarning,
  34                         module='threading', message='sys.exc_clear')
  35
  36
  37 def _old_api(callable, old_name):
  38     if not _sys.py3kwarning:
  39         return callable
  40     @wraps(callable)
  41     def old(*args, **kwargs):
  42         warnings.warnpy3k("In 3.x, {0} is renamed to {1}."
  43                           .format(old_name, callable.__name__),
  44                           stacklevel=3)
  45         return callable(*args, **kwargs)
  46     old.__name__ = old_name
  47     return old
  48
  49 # Debug support (adapted from ihooks.py).
  50 # All the major classes here derive from _Verbose.  We force that to
  51 # be a new-style class so that all the major classes here are new-style.
  52 # This helps debugging (type(instance) is more revealing for instances
  53 # of new-style classes).
  54
  55 _VERBOSE = False
  56
  57 if __debug__:
  58
  59     class _Verbose(object):
  60
  61         def __init__(self, verbose=None):
  62             if verbose is None:
  63                 verbose = _VERBOSE
  64             self.__verbose = verbose
  65
  66         def _note(self, format, *args):
  67             if self.__verbose:
  68                 format = format % args
  69                 format = "%s: %s\n" % (
  70                     current_thread().get_name(), format)
  71                 _sys.stderr.write(format)
  72
  73 else:
  74     # Disable this when using "python -O"
  75     class _Verbose(object):
  76         def __init__(self, verbose=None):
  77             pass
  78         def _note(self, *args):
  79             pass
  80
  81 # Support for profile and trace hooks
  82
  83 _profile_hook = None
  84 _trace_hook = None
  85
  86 def setprofile(func):
  87     global _profile_hook
  88     _profile_hook = func
  89
  90 def settrace(func):
  91     global _trace_hook
  92     _trace_hook = func
  93
  94 # Synchronization classes
  95
  96 Lock = _allocate_lock
  97
  98 def RLock(*args, **kwargs):
  99     return _RLock(*args, **kwargs)
 100
 101 class _RLock(_Verbose):
 102
 103     def __init__(self, verbose=None):
 104         _Verbose.__init__(self, verbose)
 105         self.__block = _allocate_lock()
 106         self.__owner = None
 107         self.__count = 0
 108
 109     def __repr__(self):
 110         owner = self.__owner
 111         return "<%s(%s, %d)>" % (
 112                 self.__class__.__name__,
 113                 owner and owner.get_name(),
 114                 self.__count)
 115
 116     def acquire(self, blocking=1):
 117         me = current_thread()
 118         if self.__owner is me:
 119             self.__count = self.__count + 1
 120             if __debug__:
 121                 self._note("%s.acquire(%s): recursive success", self, blocking)
 122             return 1
 123         rc = self.__block.acquire(blocking)
 124         if rc:
 125             self.__owner = me
 126             self.__count = 1
 127             if __debug__:
 128                 self._note("%s.acquire(%s): initial success", self, blocking)
 129         else:
 130             if __debug__:
 131                 self._note("%s.acquire(%s): failure", self, blocking)
 132         return rc
 133
 134     __enter__ = acquire
 135
 136     def release(self):
 137         if self.__owner is not current_thread():
 138             raise RuntimeError("cannot release un-aquired lock")
 139         self.__count = count = self.__count - 1
 140         if not count:
 141             self.__owner = None
 142             self.__block.release()
 143             if __debug__:
 144                 self._note("%s.release(): final release", self)
 145         else:
 146             if __debug__:
 147                 self._note("%s.release(): non-final release", self)
 148
 149     def __exit__(self, t, v, tb):
 150         self.release()
 151
 152     # Internal methods used by condition variables
 153
 154     def _acquire_restore(self, count_owner):
 155         count, owner = count_owner
 156         self.__block.acquire()
 157         self.__count = count
 158         self.__owner = owner
 159         if __debug__:
 160             self._note("%s._acquire_restore()", self)
 161
 162     def _release_save(self):
 163         if __debug__:
 164             self._note("%s._release_save()", self)
 165         count = self.__count
 166         self.__count = 0
 167         owner = self.__owner
 168         self.__owner = None
 169         self.__block.release()
 170         return (count, owner)
 171
 172     def _is_owned(self):
 173         return self.__owner is current_thread()
 174
 175
 176 def Condition(*args, **kwargs):
 177     return _Condition(*args, **kwargs)
 178
 179 class _Condition(_Verbose):
 180
 181     def __init__(self, lock=None, verbose=None):
 182         _Verbose.__init__(self, verbose)
 183         if lock is None:
 184             lock = RLock()
 185         self.__lock = lock
 186         # Export the lock's acquire() and release() methods
 187         self.acquire = lock.acquire
 188         self.release = lock.release
 189         # If the lock defines _release_save() and/or _acquire_restore(),
 190         # these override the default implementations (which just call
 191         # release() and acquire() on the lock).  Ditto for _is_owned().
 192         try:
 193             self._release_save = lock._release_save
 194         except AttributeError:
 195             pass
 196         try:
 197             self._acquire_restore = lock._acquire_restore
 198         except AttributeError:
 199             pass
 200         try:
 201             self._is_owned = lock._is_owned
 202         except AttributeError:
 203             pass
 204         self.__waiters = []
 205
 206     def __enter__(self):
 207         return self.__lock.__enter__()
 208
 209     def __exit__(self, *args):
 210         return self.__lock.__exit__(*args)
 211
 212     def __repr__(self):
 213         return "<Condition(%s, %d)>" % (self.__lock, len(self.__waiters))
 214
 215     def _release_save(self):
 216         self.__lock.release()           # No state to save
 217
 218     def _acquire_restore(self, x):
 219         self.__lock.acquire()           # Ignore saved state
 220
 221     def _is_owned(self):
 222         # Return True if lock is owned by current_thread.
 223         # This method is called only if __lock doesn't have _is_owned().
 224         if self.__lock.acquire(0):
 225             self.__lock.release()
 226             return False
 227         else:
 228             return True
 229
 230     def wait(self, timeout=None):
 231         if not self._is_owned():
 232             raise RuntimeError("cannot wait on un-aquired lock")
 233         waiter = _allocate_lock()
 234         waiter.acquire()
 235         self.__waiters.append(waiter)
 236         saved_state = self._release_save()
 237         try:    # restore state no matter what (e.g., KeyboardInterrupt)
 238             if timeout is None:
 239                 waiter.acquire()
 240                 if __debug__:
 241                     self._note("%s.wait(): got it", self)
 242             else:
 243                 # Balancing act:  We can't afford a pure busy loop, so we
 244                 # have to sleep; but if we sleep the whole timeout time,
 245                 # we'll be unresponsive.  The scheme here sleeps very
 246                 # little at first, longer as time goes on, but never longer
 247                 # than 20 times per second (or the timeout time remaining).
 248                 endtime = _time() + timeout
 249                 delay = 0.0005 # 500 us -> initial delay of 1 ms
 250                 while True:
 251                     gotit = waiter.acquire(0)
 252                     if gotit:
 253                         break
 254                     remaining = endtime - _time()
 255                     if remaining <= 0:
 256                         break
 257                     delay = min(delay * 2, remaining, .05)
 258                     _sleep(delay)
 259                 if not gotit:
 260                     if __debug__:
 261                         self._note("%s.wait(%s): timed out", self, timeout)
 262                     try:
 263                         self.__waiters.remove(waiter)
 264                     except ValueError:
 265                         pass
 266                 else:
 267                     if __debug__:
 268                         self._note("%s.wait(%s): got it", self, timeout)
 269         finally:
 270             self._acquire_restore(saved_state)
 271
 272     def notify(self, n=1):
 273         if not self._is_owned():
 274             raise RuntimeError("cannot notify on un-aquired lock")
 275         __waiters = self.__waiters
 276         waiters = __waiters[:n]
 277         if not waiters:
 278             if __debug__:
 279                 self._note("%s.notify(): no waiters", self)
 280             return
 281         self._note("%s.notify(): notifying %d waiter%s", self, n,
 282                    n!=1 and "s" or "")
 283         for waiter in waiters:
 284             waiter.release()
 285             try:
 286                 __waiters.remove(waiter)
 287             except ValueError:
 288                 pass
 289
 290     def notify_all(self):
 291         self.notify(len(self.__waiters))
 292
 293     notifyAll = _old_api(notify_all, "notifyAll")
 294
 295
 296 def Semaphore(*args, **kwargs):
 297     return _Semaphore(*args, **kwargs)
 298
 299 class _Semaphore(_Verbose):
 300
 301     # After Tim Peters' semaphore class, but not quite the same (no maximum)
 302
 303     def __init__(self, value=1, verbose=None):
 304         if value < 0:
 305             raise ValueError("semaphore initial value must be >= 0")
 306         _Verbose.__init__(self, verbose)
 307         self.__cond = Condition(Lock())
 308         self.__value = value
 309
 310     def acquire(self, blocking=1):
 311         rc = False
 312         self.__cond.acquire()
 313         while self.__value == 0:
 314             if not blocking:
 315                 break
 316             if __debug__:
 317                 self._note("%s.acquire(%s): blocked waiting, value=%s",
 318                            self, blocking, self.__value)
 319             self.__cond.wait()
 320         else:
 321             self.__value = self.__value - 1
 322             if __debug__:
 323                 self._note("%s.acquire: success, value=%s",
 324                            self, self.__value)
 325             rc = True
 326         self.__cond.release()
 327         return rc
 328
 329     __enter__ = acquire
 330
 331     def release(self):
 332         self.__cond.acquire()
 333         self.__value = self.__value + 1
 334         if __debug__:
 335             self._note("%s.release: success, value=%s",
 336                        self, self.__value)
 337         self.__cond.notify()
 338         self.__cond.release()
 339
 340     def __exit__(self, t, v, tb):
 341         self.release()
 342
 343
 344 def BoundedSemaphore(*args, **kwargs):
 345     return _BoundedSemaphore(*args, **kwargs)
 346
 347 class _BoundedSemaphore(_Semaphore):
 348     """Semaphore that checks that # releases is <= # acquires"""
 349     def __init__(self, value=1, verbose=None):
 350         _Semaphore.__init__(self, value, verbose)
 351         self._initial_value = value
 352
 353     def release(self):
 354         if self._Semaphore__value >= self._initial_value:
 355             raise ValueError, "Semaphore released too many times"
 356         return _Semaphore.release(self)
 357
 358
 359 def Event(*args, **kwargs):
 360     return _Event(*args, **kwargs)
 361
 362 class _Event(_Verbose):
 363
 364     # After Tim Peters' event class (without is_posted())
 365
 366     def __init__(self, verbose=None):
 367         _Verbose.__init__(self, verbose)
 368         self.__cond = Condition(Lock())
 369         self.__flag = False
 370
 371     def is_set(self):
 372         return self.__flag
 373
 374     isSet = _old_api(is_set, "isSet")
 375
 376     def set(self):
 377         self.__cond.acquire()
 378         try:
 379             self.__flag = True
 380             self.__cond.notify_all()
 381         finally:
 382             self.__cond.release()
 383
 384     def clear(self):
 385         self.__cond.acquire()
 386         try:
 387             self.__flag = False
 388         finally:
 389             self.__cond.release()
 390
 391     def wait(self, timeout=None):
 392         self.__cond.acquire()
 393         try:
 394             if not self.__flag:
 395                 self.__cond.wait(timeout)
 396         finally:
 397             self.__cond.release()
 398
 399 # Helper to generate new thread names
 400 _counter = 0
 401 def _newname(template="Thread-%d"):
 402     global _counter
 403     _counter = _counter + 1
 404     return template % _counter
 405
 406 # Active thread administration
 407 _active_limbo_lock = _allocate_lock()
 408 _active = {}    # maps thread id to Thread object
 409 _limbo = {}
 410
 411
 412 # Main class for threads
 413
 414 class Thread(_Verbose):
 415
 416     __initialized = False
 417     # Need to store a reference to sys.exc_info for printing
 418     # out exceptions when a thread tries to use a global var. during interp.
 419     # shutdown and thus raises an exception about trying to perform some
 420     # operation on/with a NoneType
 421     __exc_info = _sys.exc_info
 422     # Keep sys.exc_clear too to clear the exception just before
 423     # allowing .join() to return.
 424     __exc_clear = _sys.exc_clear
 425
 426     def __init__(self, group=None, target=None, name=None,
 427                  args=(), kwargs=None, verbose=None):
 428         assert group is None, "group argument must be None for now"
 429         _Verbose.__init__(self, verbose)
 430         if kwargs is None:
 431             kwargs = {}
 432         self.__target = target
 433         self.__name = str(name or _newname())
 434         self.__args = args
 435         self.__kwargs = kwargs
 436         self.__daemonic = self._set_daemon()
 437         self.__ident = None
 438         self.__started = Event()
 439         self.__stopped = False
 440         self.__block = Condition(Lock())
 441         self.__initialized = True
 442         # sys.stderr is not stored in the class like
 443         # sys.exc_info since it can be changed between instances
 444         self.__stderr = _sys.stderr
 445
 446     def _set_daemon(self):
 447         # Overridden in _MainThread and _DummyThread
 448         return current_thread().is_daemon()
 449
 450     def __repr__(self):
 451         assert self.__initialized, "Thread.__init__() was not called"
 452         status = "initial"
 453         if self.__started.is_set():
 454             status = "started"
 455         if self.__stopped:
 456             status = "stopped"
 457         if self.__daemonic:
 458             status += " daemon"
 459         if self.__ident is not None:
 460             status += " %s" % self.__ident
 461         return "<%s(%s, %s)>" % (self.__class__.__name__, self.__name, status)
 462
 463     def start(self):
 464         if not self.__initialized:
 465             raise RuntimeError("thread.__init__() not called")
 466         if self.__started.is_set():
 467             raise RuntimeError("thread already started")
 468         if __debug__:
 469             self._note("%s.start(): starting thread", self)
 470         _active_limbo_lock.acquire()
 471         _limbo[self] = self
 472         _active_limbo_lock.release()
 473         _start_new_thread(self.__bootstrap, ())
 474         self.__started.wait()
 475
 476     def run(self):
 477         try:
 478             if self.__target:
 479                 self.__target(*self.__args, **self.__kwargs)
 480         finally:
 481             # Avoid a refcycle if the thread is running a function with
 482             # an argument that has a member that points to the thread.
 483             del self.__target, self.__args, self.__kwargs
 484
 485     def __bootstrap(self):
 486         # Wrapper around the real bootstrap code that ignores
 487         # exceptions during interpreter cleanup.  Those typically
 488         # happen when a daemon thread wakes up at an unfortunate
 489         # moment, finds the world around it destroyed, and raises some
 490         # random exception *** while trying to report the exception in
 491         # __bootstrap_inner() below ***.  Those random exceptions
 492         # don't help anybody, and they confuse users, so we suppress
 493         # them.  We suppress them only when it appears that the world
 494         # indeed has already been destroyed, so that exceptions in
 495         # __bootstrap_inner() during normal business hours are properly
 496         # reported.  Also, we only suppress them for daemonic threads;
 497         # if a non-daemonic encounters this, something else is wrong.
 498         try:
 499             self.__bootstrap_inner()
 500         except:
 501             if self.__daemonic and _sys is None:
 502                 return
 503             raise
 504
 505     def __bootstrap_inner(self):
 506         try:
 507             self.__ident = _get_ident()
 508             self.__started.set()
 509             _active_limbo_lock.acquire()
 510             _active[self.__ident] = self
 511             del _limbo[self]
 512             _active_limbo_lock.release()
 513             if __debug__:
 514                 self._note("%s.__bootstrap(): thread started", self)
 515
 516             if _trace_hook:
 517                 self._note("%s.__bootstrap(): registering trace hook", self)
 518                 _sys.settrace(_trace_hook)
 519             if _profile_hook:
 520                 self._note("%s.__bootstrap(): registering profile hook", self)
 521                 _sys.setprofile(_profile_hook)
 522
 523             try:
 524                 self.run()
 525             except SystemExit:
 526                 if __debug__:
 527                     self._note("%s.__bootstrap(): raised SystemExit", self)
 528             except:
 529                 if __debug__:
 530                     self._note("%s.__bootstrap(): unhandled exception", self)
 531                 # If sys.stderr is no more (most likely from interpreter
 532                 # shutdown) use self.__stderr.  Otherwise still use sys (as in
 533                 # _sys) in case sys.stderr was redefined since the creation of
 534                 # self.
 535                 if _sys:
 536                     _sys.stderr.write("Exception in thread %s:\n%s\n" %
 537                                       (self.get_name(), _format_exc()))
 538                 else:
 539                     # Do the best job possible w/o a huge amt. of code to
 540                     # approximate a traceback (code ideas from
 541                     # Lib/traceback.py)
 542                     exc_type, exc_value, exc_tb = self.__exc_info()
 543                     try:
 544                         print>>self.__stderr, (
 545                             "Exception in thread " + self.get_name() +
 546                             " (most likely raised during interpreter shutdown):")
 547                         print>>self.__stderr, (
 548                             "Traceback (most recent call last):")
 549                         while exc_tb:
 550                             print>>self.__stderr, (
 551                                 '  File "%s", line %s, in %s' %
 552                                 (exc_tb.tb_frame.f_code.co_filename,
 553                                     exc_tb.tb_lineno,
 554                                     exc_tb.tb_frame.f_code.co_name))
 555                             exc_tb = exc_tb.tb_next
 556                         print>>self.__stderr, ("%s: %s" % (exc_type, exc_value))
 557                     # Make sure that exc_tb gets deleted since it is a memory
 558                     # hog; deleting everything else is just for thoroughness
 559                     finally:
 560                         del exc_type, exc_value, exc_tb
 561             else:
 562                 if __debug__:
 563                     self._note("%s.__bootstrap(): normal return", self)
 564             finally:
 565                 # Prevent a race in
 566                 # test_threading.test_no_refcycle_through_target when
 567                 # the exception keeps the target alive past when we
 568                 # assert that it's dead.
 569                 self.__exc_clear()
 570         finally:
 571             with _active_limbo_lock:
 572                 self.__stop()
 573                 try:
 574                     # We don't call self.__delete() because it also
 575                     # grabs _active_limbo_lock.
 576                     del _active[_get_ident()]
 577                 except:
 578                     pass
 579
 580     def __stop(self):
 581         self.__block.acquire()
 582         self.__stopped = True
 583         self.__block.notify_all()
 584         self.__block.release()
 585
 586     def __delete(self):
 587         "Remove current thread from the dict of currently running threads."
 588
 589         # Notes about running with dummy_thread:
 590         #
 591         # Must take care to not raise an exception if dummy_thread is being
 592         # used (and thus this module is being used as an instance of
 593         # dummy_threading).  dummy_thread.get_ident() always returns -1 since
 594         # there is only one thread if dummy_thread is being used.  Thus
 595         # len(_active) is always <= 1 here, and any Thread instance created
 596         # overwrites the (if any) thread currently registered in _active.
 597         #
 598         # An instance of _MainThread is always created by 'threading'.  This
 599         # gets overwritten the instant an instance of Thread is created; both
 600         # threads return -1 from dummy_thread.get_ident() and thus have the
 601         # same key in the dict.  So when the _MainThread instance created by
 602         # 'threading' tries to clean itself up when atexit calls this method
 603         # it gets a KeyError if another Thread instance was created.
 604         #
 605         # This all means that KeyError from trying to delete something from
 606         # _active if dummy_threading is being used is a red herring.  But
 607         # since it isn't if dummy_threading is *not* being used then don't
 608         # hide the exception.
 609
 610         try:
 611             with _active_limbo_lock:
 612                 del _active[_get_ident()]
 613                 # There must not be any python code between the previous line
 614                 # and after the lock is released.  Otherwise a tracing function
 615                 # could try to acquire the lock again in the same thread, (in
 616                 # current_thread()), and would block.
 617         except KeyError:
 618             if 'dummy_threading' not in _sys.modules:
 619                 raise
 620
 621     def join(self, timeout=None):
 622         if not self.__initialized:
 623             raise RuntimeError("Thread.__init__() not called")
 624         if not self.__started.is_set():
 625             raise RuntimeError("cannot join thread before it is started")
 626         if self is current_thread():
 627             raise RuntimeError("cannot join current thread")
 628
 629         if __debug__:
 630             if not self.__stopped:
 631                 self._note("%s.join(): waiting until thread stops", self)
 632         self.__block.acquire()
 633         try:
 634             if timeout is None:
 635                 while not self.__stopped:
 636                     self.__block.wait()
 637                 if __debug__:
 638                     self._note("%s.join(): thread stopped", self)
 639             else:
 640                 deadline = _time() + timeout
 641                 while not self.__stopped:
 642                     delay = deadline - _time()
 643                     if delay <= 0:
 644                         if __debug__:
 645                             self._note("%s.join(): timed out", self)
 646                         break
 647                     self.__block.wait(delay)
 648                 else:
 649                     if __debug__:
 650                         self._note("%s.join(): thread stopped", self)
 651         finally:
 652             self.__block.release()
 653
 654     def get_name(self):
 655         assert self.__initialized, "Thread.__init__() not called"
 656         return self.__name
 657
 658     getName = _old_api(get_name, "getName")
 659
 660     def set_name(self, name):
 661         assert self.__initialized, "Thread.__init__() not called"
 662         self.__name = str(name)
 663
 664     setName = _old_api(set_name, "setName")
 665
 666     def get_ident(self):
 667         assert self.__initialized, "Thread.__init__() not called"
 668         return self.__ident
 669
 670     def is_alive(self):
 671         assert self.__initialized, "Thread.__init__() not called"
 672         return self.__started.is_set() and not self.__stopped
 673
 674     isAlive = _old_api(is_alive, "isAlive")
 675
 676     def is_daemon(self):
 677         assert self.__initialized, "Thread.__init__() not called"
 678         return self.__daemonic
 679
 680     isDaemon = _old_api(is_daemon, "isDaemon")
 681
 682     def set_daemon(self, daemonic):
 683         if not self.__initialized:
 684             raise RuntimeError("Thread.__init__() not called")
 685         if self.__started.is_set():
 686             raise RuntimeError("cannot set daemon status of active thread");
 687         self.__daemonic = daemonic
 688
 689     setDaemon = _old_api(set_daemon, "setDaemon")
 690
 691 # The timer class was contributed by Itamar Shtull-Trauring
 692
 693 def Timer(*args, **kwargs):
 694     return _Timer(*args, **kwargs)
 695
 696 class _Timer(Thread):
 697     """Call a function after a specified number of seconds:
 698
 699     t = Timer(30.0, f, args=[], kwargs={})
 700     t.start()
 701     t.cancel() # stop the timer's action if it's still waiting
 702     """
 703
 704     def __init__(self, interval, function, args=[], kwargs={}):
 705         Thread.__init__(self)
 706         self.interval = interval
 707         self.function = function
 708         self.args = args
 709         self.kwargs = kwargs
 710         self.finished = Event()
 711
 712     def cancel(self):
 713         """Stop the timer if it hasn't finished yet"""
 714         self.finished.set()
 715
 716     def run(self):
 717         self.finished.wait(self.interval)
 718         if not self.finished.is_set():
 719             self.function(*self.args, **self.kwargs)
 720         self.finished.set()
 721
 722 # Special thread class to represent the main thread
 723 # This is garbage collected through an exit handler
 724
 725 class _MainThread(Thread):
 726
 727     def __init__(self):
 728         Thread.__init__(self, name="MainThread")
 729         self._Thread__started.set()
 730         _active_limbo_lock.acquire()
 731         _active[_get_ident()] = self
 732         _active_limbo_lock.release()
 733
 734     def _set_daemon(self):
 735         return False
 736
 737     def _exitfunc(self):
 738         self._Thread__stop()
 739         t = _pickSomeNonDaemonThread()
 740         if t:
 741             if __debug__:
 742                 self._note("%s: waiting for other threads", self)
 743         while t:
 744             t.join()
 745             t = _pickSomeNonDaemonThread()
 746         if __debug__:
 747             self._note("%s: exiting", self)
 748         self._Thread__delete()
 749
 750 def _pickSomeNonDaemonThread():
 751     for t in enumerate():
 752         if not t.is_daemon() and t.is_alive():
 753             return t
 754     return None
 755
 756
 757 # Dummy thread class to represent threads not started here.
 758 # These aren't garbage collected when they die, nor can they be waited for.
 759 # If they invoke anything in threading.py that calls current_thread(), they
 760 # leave an entry in the _active dict forever after.
 761 # Their purpose is to return *something* from current_thread().
 762 # They are marked as daemon threads so we won't wait for them
 763 # when we exit (conform previous semantics).
 764
 765 class _DummyThread(Thread):
 766
 767     def __init__(self):
 768         Thread.__init__(self, name=_newname("Dummy-%d"))
 769
 770         # Thread.__block consumes an OS-level locking primitive, which
 771         # can never be used by a _DummyThread.  Since a _DummyThread
 772         # instance is immortal, that's bad, so release this resource.
 773         del self._Thread__block
 774
 775         self._Thread__started.set()
 776         _active_limbo_lock.acquire()
 777         _active[_get_ident()] = self
 778         _active_limbo_lock.release()
 779
 780     def _set_daemon(self):
 781         return True
 782
 783     def join(self, timeout=None):
 784         assert False, "cannot join a dummy thread"
 785
 786
 787 # Global API functions
 788
 789 def current_thread():
 790     try:
 791         return _active[_get_ident()]
 792     except KeyError:
 793         ##print "current_thread(): no current thread for", _get_ident()
 794         return _DummyThread()
 795
 796 currentThread = _old_api(current_thread, "currentThread")
 797
 798 def active_count():
 799     _active_limbo_lock.acquire()
 800     count = len(_active) + len(_limbo)
 801     _active_limbo_lock.release()
 802     return count
 803
 804 activeCount = _old_api(active_count, "activeCount")
 805
 806 def enumerate():
 807     _active_limbo_lock.acquire()
 808     active = _active.values() + _limbo.values()
 809     _active_limbo_lock.release()
 810     return active
 811
 812 from thread import stack_size
 813
 814 # Create the main thread object,
 815 # and make it available for the interpreter
 816 # (Py_Main) as threading._shutdown.
 817
 818 _shutdown = _MainThread()._exitfunc
 819
 820 # get thread-local implementation, either from the thread
 821 # module, or from the python fallback
 822
 823 try:
 824     from thread import _local as local
 825 except ImportError:
 826     from _threading_local import local
 827
 828
 829 def _after_fork():
 830     # This function is called by Python/ceval.c:PyEval_ReInitThreads which
 831     # is called from PyOS_AfterFork.  Here we cleanup threading module state
 832     # that should not exist after a fork.
 833
 834     # Reset _active_limbo_lock, in case we forked while the lock was held
 835     # by another (non-forked) thread.  http://bugs.python.org/issue874900
 836     global _active_limbo_lock
 837     _active_limbo_lock = _allocate_lock()
 838
 839     # fork() only copied the current thread; clear references to others.
 840     new_active = {}
 841     current = current_thread()
 842     with _active_limbo_lock:
 843         for ident, thread in _active.iteritems():
 844             if thread is current:
 845                 # There is only one active thread.
 846                 new_active[ident] = thread
 847             else:
 848                 # All the others are already stopped.
 849                 # We don't call _Thread__stop() because it tries to acquire
 850                 # thread._Thread__block which could also have been held while
 851                 # we forked.
 852                 thread._Thread__stopped = True
 853
 854         _limbo.clear()
 855         _active.clear()
 856         _active.update(new_active)
 857         assert len(_active) == 1
 858
 859
 860 # Self-test code
 861
 862 def _test():
 863
 864     class BoundedQueue(_Verbose):
 865
 866         def __init__(self, limit):
 867             _Verbose.__init__(self)
 868             self.mon = RLock()
 869             self.rc = Condition(self.mon)
 870             self.wc = Condition(self.mon)
 871             self.limit = limit
 872             self.queue = deque()
 873
 874         def put(self, item):
 875             self.mon.acquire()
 876             while len(self.queue) >= self.limit:
 877                 self._note("put(%s): queue full", item)
 878                 self.wc.wait()
 879             self.queue.append(item)
 880             self._note("put(%s): appended, length now %d",
 881                        item, len(self.queue))
 882             self.rc.notify()
 883             self.mon.release()
 884
 885         def get(self):
 886             self.mon.acquire()
 887             while not self.queue:
 888                 self._note("get(): queue empty")
 889                 self.rc.wait()
 890             item = self.queue.popleft()
 891             self._note("get(): got %s, %d left", item, len(self.queue))
 892             self.wc.notify()
 893             self.mon.release()
 894             return item
 895
 896     class ProducerThread(Thread):
 897
 898         def __init__(self, queue, quota):
 899             Thread.__init__(self, name="Producer")
 900             self.queue = queue
 901             self.quota = quota
 902
 903         def run(self):
 904             from random import random
 905             counter = 0
 906             while counter < self.quota:
 907                 counter = counter + 1
 908                 self.queue.put("%s.%d" % (self.get_name(), counter))
 909                 _sleep(random() * 0.00001)
 910
 911
 912     class ConsumerThread(Thread):
 913
 914         def __init__(self, queue, count):
 915             Thread.__init__(self, name="Consumer")
 916             self.queue = queue
 917             self.count = count
 918
 919         def run(self):
 920             while self.count > 0:
 921                 item = self.queue.get()
 922                 print item
 923                 self.count = self.count - 1
 924
 925     NP = 3
 926     QL = 4
 927     NI = 5
 928
 929     Q = BoundedQueue(QL)
 930     P = []
 931     for i in range(NP):
 932         t = ProducerThread(Q, NI)
 933         t.setName("Producer-%d" % (i+1))
 934         P.append(t)
 935     C = ConsumerThread(Q, NI*NP)
 936     for t in P:
 937         t.start()
 938         _sleep(0.000001)
 939     C.start()
 940     for t in P:
 941         t.join()
 942     C.join()
 943
 944 if __name__ == '__main__':
 945     _test()