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