Lib/threading.py

   1 """Proposed new threading module, emulating a subset of Java's threading model."""
   2
   3 import sys
   4 import time
   5 import thread
   6 import traceback
   7 import StringIO
   8
   9 # Rename some stuff so "from threading import *" is safe
  10
  11 _sys = sys
  12 del sys
  13
  14 _time = time.time
  15 _sleep = time.sleep
  16 del time
  17
  18 _start_new_thread = thread.start_new_thread
  19 _allocate_lock = thread.allocate_lock
  20 _get_ident = thread.get_ident
  21 ThreadError = thread.error
  22 del thread
  23
  24 _print_exc = traceback.print_exc
  25 del traceback
  26
  27 _StringIO = StringIO.StringIO
  28 del StringIO
  29
  30
  31 # Debug support (adapted from ihooks.py)
  32
  33 _VERBOSE = 0
  34
  35 if __debug__:
  36
  37     class _Verbose:
  38
  39         def __init__(self, verbose=None):
  40             if verbose is None:
  41                 verbose = _VERBOSE
  42             self.__verbose = verbose
  43
  44         def _note(self, format, *args):
  45             if self.__verbose:
  46                 format = format % args
  47                 format = "%s: %s\n" % (
  48                     currentThread().getName(), format)
  49                 _sys.stderr.write(format)
  50
  51 else:
  52     # Disable this when using "python -O"
  53     class _Verbose:
  54         def __init__(self, verbose=None):
  55             pass
  56         def _note(self, *args):
  57             pass
  58
  59
  60 # Synchronization classes
  61
  62 Lock = _allocate_lock
  63
  64 def RLock(*args, **kwargs):
  65     return apply(_RLock, args, kwargs)
  66
  67 class _RLock(_Verbose):
  68
  69     def __init__(self, verbose=None):
  70         _Verbose.__init__(self, verbose)
  71         self.__block = _allocate_lock()
  72         self.__owner = None
  73         self.__count = 0
  74
  75     def __repr__(self):
  76         return "<%s(%s, %d)>" % (
  77                 self.__class__.__name__,
  78                 self.__owner and self.__owner.getName(),
  79                 self.__count)
  80
  81     def acquire(self, blocking=1):
  82         me = currentThread()
  83         if self.__owner is me:
  84             self.__count = self.__count + 1
  85             if __debug__:
  86                 self._note("%s.acquire(%s): recursive success", self, blocking)
  87             return 1
  88         rc = self.__block.acquire(blocking)
  89         if rc:
  90             self.__owner = me
  91             self.__count = 1
  92             if __debug__:
  93                 self._note("%s.acquire(%s): initial succes", self, blocking)
  94         else:
  95             if __debug__:
  96                 self._note("%s.acquire(%s): failure", self, blocking)
  97         return rc
  98
  99     def release(self):
 100         me = currentThread()
 101         assert self.__owner is me, "release() of un-acquire()d lock"
 102         self.__count = count = self.__count - 1
 103         if not count:
 104             self.__owner = None
 105             self.__block.release()
 106             if __debug__:
 107                 self._note("%s.release(): final release", self)
 108         else:
 109             if __debug__:
 110                 self._note("%s.release(): non-final release", self)
 111
 112     # Internal methods used by condition variables
 113
 114     def _acquire_restore(self, (count, owner)):
 115         self.__block.acquire()
 116         self.__count = count
 117         self.__owner = owner
 118         if __debug__:
 119             self._note("%s._acquire_restore()", self)
 120
 121     def _release_save(self):
 122         if __debug__:
 123             self._note("%s._release_save()", self)
 124         count = self.__count
 125         self.__count = 0
 126         owner = self.__owner
 127         self.__owner = None
 128         self.__block.release()
 129         return (count, owner)
 130
 131     def _is_owned(self):
 132         return self.__owner is currentThread()
 133
 134
 135 def Condition(*args, **kwargs):
 136     return apply(_Condition, args, kwargs)
 137
 138 class _Condition(_Verbose):
 139
 140     def __init__(self, lock=None, verbose=None):
 141         _Verbose.__init__(self, verbose)
 142         if lock is None:
 143             lock = RLock()
 144         self.__lock = lock
 145         # Export the lock's acquire() and release() methods
 146         self.acquire = lock.acquire
 147         self.release = lock.release
 148         # If the lock defines _release_save() and/or _acquire_restore(),
 149         # these override the default implementations (which just call
 150         # release() and acquire() on the lock).  Ditto for _is_owned().
 151         try:
 152             self._release_save = lock._release_save
 153         except AttributeError:
 154             pass
 155         try:
 156             self._acquire_restore = lock._acquire_restore
 157         except AttributeError:
 158             pass
 159         try:
 160             self._is_owned = lock._is_owned
 161         except AttributeError:
 162             pass
 163         self.__waiters = []
 164
 165     def __repr__(self):
 166         return "<Condition(%s, %d)>" % (self.__lock, len(self.__waiters))
 167
 168     def _release_save(self):
 169         self.__lock.release()           # No state to save
 170
 171     def _acquire_restore(self, x):
 172         self.__lock.acquire()           # Ignore saved state
 173
 174     def _is_owned(self):
 175         if self.__lock.acquire(0):
 176             self.__lock.release()
 177             return 0
 178         else:
 179             return 1
 180
 181     def wait(self, timeout=None):
 182         me = currentThread()
 183         assert self._is_owned(), "wait() of un-acquire()d lock"
 184         waiter = _allocate_lock()
 185         waiter.acquire()
 186         self.__waiters.append(waiter)
 187         saved_state = self._release_save()
 188         try:    # restore state no matter what (e.g., KeyboardInterrupt)
 189             if timeout is None:
 190                 waiter.acquire()
 191                 if __debug__:
 192                     self._note("%s.wait(): got it", self)
 193             else:
 194                 # Balancing act:  We can't afford a pure busy loop, so we
 195                 # have to sleep; but if we sleep the whole timeout time,
 196                 # we'll be unresponsive.  The scheme here sleeps very
 197                 # little at first, longer as time goes on, but never longer
 198                 # than 20 times per second (or the timeout time remaining).
 199                 endtime = _time() + timeout
 200                 delay = 0.0005 # 500 us -> initial delay of 1 ms
 201                 while 1:
 202                     gotit = waiter.acquire(0)
 203                     if gotit:
 204                         break
 205                     remaining = endtime - _time()
 206                     if remaining <= 0:
 207                         break
 208                     delay = min(delay * 2, remaining, .05)
 209                     _sleep(delay)
 210                 if not gotit:
 211                     if __debug__:
 212                         self._note("%s.wait(%s): timed out", self, timeout)
 213                     try:
 214                         self.__waiters.remove(waiter)
 215                     except ValueError:
 216                         pass
 217                 else:
 218                     if __debug__:
 219                         self._note("%s.wait(%s): got it", self, timeout)
 220         finally:
 221             self._acquire_restore(saved_state)
 222
 223     def notify(self, n=1):
 224         me = currentThread()
 225         assert self._is_owned(), "notify() of un-acquire()d lock"
 226         __waiters = self.__waiters
 227         waiters = __waiters[:n]
 228         if not waiters:
 229             if __debug__:
 230                 self._note("%s.notify(): no waiters", self)
 231             return
 232         self._note("%s.notify(): notifying %d waiter%s", self, n,
 233                    n!=1 and "s" or "")
 234         for waiter in waiters:
 235             waiter.release()
 236             try:
 237                 __waiters.remove(waiter)
 238             except ValueError:
 239                 pass
 240
 241     def notifyAll(self):
 242         self.notify(len(self.__waiters))
 243
 244
 245 def Semaphore(*args, **kwargs):
 246     return apply(_Semaphore, args, kwargs)
 247
 248 class _Semaphore(_Verbose):
 249
 250     # After Tim Peters' semaphore class, but not quite the same (no maximum)
 251
 252     def __init__(self, value=1, verbose=None):
 253         assert value >= 0, "Semaphore initial value must be >= 0"
 254         _Verbose.__init__(self, verbose)
 255         self.__cond = Condition(Lock())
 256         self.__value = value
 257
 258     def acquire(self, blocking=1):
 259         rc = 0
 260         self.__cond.acquire()
 261         while self.__value == 0:
 262             if not blocking:
 263                 break
 264             if __debug__:
 265                 self._note("%s.acquire(%s): blocked waiting, value=%s",
 266                            self, blocking, self.__value)
 267             self.__cond.wait()
 268         else:
 269             self.__value = self.__value - 1
 270             if __debug__:
 271                 self._note("%s.acquire: success, value=%s",
 272                            self, self.__value)
 273             rc = 1
 274         self.__cond.release()
 275         return rc
 276
 277     def release(self):
 278         self.__cond.acquire()
 279         self.__value = self.__value + 1
 280         if __debug__:
 281             self._note("%s.release: success, value=%s",
 282                        self, self.__value)
 283         self.__cond.notify()
 284         self.__cond.release()
 285
 286
 287 def BoundedSemaphore(*args, **kwargs):
 288     return apply(_BoundedSemaphore, args, kwargs)
 289
 290 class _BoundedSemaphore(_Semaphore):
 291     """Semaphore that checks that # releases is <= # acquires"""
 292     def __init__(self, value=1, verbose=None):
 293         _Semaphore.__init__(self, value, verbose)
 294         self._initial_value = value
 295
 296     def release(self):
 297         if self._Semaphore__value >= self._initial_value:
 298             raise ValueError, "Semaphore released too many times"
 299         return _Semaphore.release(self)
 300
 301
 302 def Event(*args, **kwargs):
 303     return apply(_Event, args, kwargs)
 304
 305 class _Event(_Verbose):
 306
 307     # After Tim Peters' event class (without is_posted())
 308
 309     def __init__(self, verbose=None):
 310         _Verbose.__init__(self, verbose)
 311         self.__cond = Condition(Lock())
 312         self.__flag = 0
 313
 314     def isSet(self):
 315         return self.__flag
 316
 317     def set(self):
 318         self.__cond.acquire()
 319         self.__flag = 1
 320         self.__cond.notifyAll()
 321         self.__cond.release()
 322
 323     def clear(self):
 324         self.__cond.acquire()
 325         self.__flag = 0
 326         self.__cond.release()
 327
 328     def wait(self, timeout=None):
 329         self.__cond.acquire()
 330         if not self.__flag:
 331             self.__cond.wait(timeout)
 332         self.__cond.release()
 333
 334 # Helper to generate new thread names
 335 _counter = 0
 336 def _newname(template="Thread-%d"):
 337     global _counter
 338     _counter = _counter + 1
 339     return template % _counter
 340
 341 # Active thread administration
 342 _active_limbo_lock = _allocate_lock()
 343 _active = {}
 344 _limbo = {}
 345
 346
 347 # Main class for threads
 348
 349 class Thread(_Verbose):
 350
 351     __initialized = 0
 352
 353     def __init__(self, group=None, target=None, name=None,
 354                  args=(), kwargs={}, verbose=None):
 355         assert group is None, "group argument must be None for now"
 356         _Verbose.__init__(self, verbose)
 357         self.__target = target
 358         self.__name = str(name or _newname())
 359         self.__args = args
 360         self.__kwargs = kwargs
 361         self.__daemonic = self._set_daemon()
 362         self.__started = 0
 363         self.__stopped = 0
 364         self.__block = Condition(Lock())
 365         self.__initialized = 1
 366
 367     def _set_daemon(self):
 368         # Overridden in _MainThread and _DummyThread
 369         return currentThread().isDaemon()
 370
 371     def __repr__(self):
 372         assert self.__initialized, "Thread.__init__() was not called"
 373         status = "initial"
 374         if self.__started:
 375             status = "started"
 376         if self.__stopped:
 377             status = "stopped"
 378         if self.__daemonic:
 379             status = status + " daemon"
 380         return "<%s(%s, %s)>" % (self.__class__.__name__, self.__name, status)
 381
 382     def start(self):
 383         assert self.__initialized, "Thread.__init__() not called"
 384         assert not self.__started, "thread already started"
 385         if __debug__:
 386             self._note("%s.start(): starting thread", self)
 387         _active_limbo_lock.acquire()
 388         _limbo[self] = self
 389         _active_limbo_lock.release()
 390         _start_new_thread(self.__bootstrap, ())
 391         self.__started = 1
 392         _sleep(0.000001)    # 1 usec, to let the thread run (Solaris hack)
 393
 394     def run(self):
 395         if self.__target:
 396             apply(self.__target, self.__args, self.__kwargs)
 397
 398     def __bootstrap(self):
 399         try:
 400             self.__started = 1
 401             _active_limbo_lock.acquire()
 402             _active[_get_ident()] = self
 403             del _limbo[self]
 404             _active_limbo_lock.release()
 405             if __debug__:
 406                 self._note("%s.__bootstrap(): thread started", self)
 407             try:
 408                 self.run()
 409             except SystemExit:
 410                 if __debug__:
 411                     self._note("%s.__bootstrap(): raised SystemExit", self)
 412             except:
 413                 if __debug__:
 414                     self._note("%s.__bootstrap(): unhandled exception", self)
 415                 s = _StringIO()
 416                 _print_exc(file=s)
 417                 _sys.stderr.write("Exception in thread %s:\n%s\n" %
 418                                  (self.getName(), s.getvalue()))
 419             else:
 420                 if __debug__:
 421                     self._note("%s.__bootstrap(): normal return", self)
 422         finally:
 423             self.__stop()
 424             self.__delete()
 425
 426     def __stop(self):
 427         self.__block.acquire()
 428         self.__stopped = 1
 429         self.__block.notifyAll()
 430         self.__block.release()
 431
 432     def __delete(self):
 433         _active_limbo_lock.acquire()
 434         del _active[_get_ident()]
 435         _active_limbo_lock.release()
 436
 437     def join(self, timeout=None):
 438         assert self.__initialized, "Thread.__init__() not called"
 439         assert self.__started, "cannot join thread before it is started"
 440         assert self is not currentThread(), "cannot join current thread"
 441         if __debug__:
 442             if not self.__stopped:
 443                 self._note("%s.join(): waiting until thread stops", self)
 444         self.__block.acquire()
 445         if timeout is None:
 446             while not self.__stopped:
 447                 self.__block.wait()
 448             if __debug__:
 449                 self._note("%s.join(): thread stopped", self)
 450         else:
 451             deadline = _time() + timeout
 452             while not self.__stopped:
 453                 delay = deadline - _time()
 454                 if delay <= 0:
 455                     if __debug__:
 456                         self._note("%s.join(): timed out", self)
 457                     break
 458                 self.__block.wait(delay)
 459             else:
 460                 if __debug__:
 461                     self._note("%s.join(): thread stopped", self)
 462         self.__block.release()
 463
 464     def getName(self):
 465         assert self.__initialized, "Thread.__init__() not called"
 466         return self.__name
 467
 468     def setName(self, name):
 469         assert self.__initialized, "Thread.__init__() not called"
 470         self.__name = str(name)
 471
 472     def isAlive(self):
 473         assert self.__initialized, "Thread.__init__() not called"
 474         return self.__started and not self.__stopped
 475
 476     def isDaemon(self):
 477         assert self.__initialized, "Thread.__init__() not called"
 478         return self.__daemonic
 479
 480     def setDaemon(self, daemonic):
 481         assert self.__initialized, "Thread.__init__() not called"
 482         assert not self.__started, "cannot set daemon status of active thread"
 483         self.__daemonic = daemonic
 484
 485 # The timer class was contributed by Itamar Shtull-Trauring
 486
 487 def Timer(*args, **kwargs):
 488     return _Timer(*args, **kwargs)
 489
 490 class _Timer(Thread):
 491     """Call a function after a specified number of seconds:
 492
 493     t = Timer(30.0, f, args=[], kwargs={})
 494     t.start()
 495     t.cancel() # stop the timer's action if it's still waiting
 496     """
 497
 498     def __init__(self, interval, function, args=[], kwargs={}):
 499         Thread.__init__(self)
 500         self.interval = interval
 501         self.function = function
 502         self.args = args
 503         self.kwargs = kwargs
 504         self.finished = Event()
 505
 506     def cancel(self):
 507         """Stop the timer if it hasn't finished yet"""
 508         self.finished.set()
 509
 510     def run(self):
 511         self.finished.wait(self.interval)
 512         if not self.finished.isSet():
 513             self.function(*self.args, **self.kwargs)
 514         self.finished.set()
 515
 516 # Special thread class to represent the main thread
 517 # This is garbage collected through an exit handler
 518
 519 class _MainThread(Thread):
 520
 521     def __init__(self):
 522         Thread.__init__(self, name="MainThread")
 523         self._Thread__started = 1
 524         _active_limbo_lock.acquire()
 525         _active[_get_ident()] = self
 526         _active_limbo_lock.release()
 527         import atexit
 528         atexit.register(self.__exitfunc)
 529
 530     def _set_daemon(self):
 531         return 0
 532
 533     def __exitfunc(self):
 534         self._Thread__stop()
 535         t = _pickSomeNonDaemonThread()
 536         if t:
 537             if __debug__:
 538                 self._note("%s: waiting for other threads", self)
 539         while t:
 540             t.join()
 541             t = _pickSomeNonDaemonThread()
 542         if __debug__:
 543             self._note("%s: exiting", self)
 544         self._Thread__delete()
 545
 546 def _pickSomeNonDaemonThread():
 547     for t in enumerate():
 548         if not t.isDaemon() and t.isAlive():
 549             return t
 550     return None
 551
 552
 553 # Dummy thread class to represent threads not started here.
 554 # These aren't garbage collected when they die,
 555 # nor can they be waited for.
 556 # Their purpose is to return *something* from currentThread().
 557 # They are marked as daemon threads so we won't wait for them
 558 # when we exit (conform previous semantics).
 559
 560 class _DummyThread(Thread):
 561
 562     def __init__(self):
 563         Thread.__init__(self, name=_newname("Dummy-%d"))
 564         self._Thread__started = 1
 565         _active_limbo_lock.acquire()
 566         _active[_get_ident()] = self
 567         _active_limbo_lock.release()
 568
 569     def _set_daemon(self):
 570         return 1
 571
 572     def join(self):
 573         assert 0, "cannot join a dummy thread"
 574
 575
 576 # Global API functions
 577
 578 def currentThread():
 579     try:
 580         return _active[_get_ident()]
 581     except KeyError:
 582         ##print "currentThread(): no current thread for", _get_ident()
 583         return _DummyThread()
 584
 585 def activeCount():
 586     _active_limbo_lock.acquire()
 587     count = len(_active) + len(_limbo)
 588     _active_limbo_lock.release()
 589     return count
 590
 591 def enumerate():
 592     _active_limbo_lock.acquire()
 593     active = _active.values() + _limbo.values()
 594     _active_limbo_lock.release()
 595     return active
 596
 597
 598 # Create the main thread object
 599
 600 _MainThread()
 601
 602
 603 # Self-test code
 604
 605 def _test():
 606
 607     class BoundedQueue(_Verbose):
 608
 609         def __init__(self, limit):
 610             _Verbose.__init__(self)
 611             self.mon = RLock()
 612             self.rc = Condition(self.mon)
 613             self.wc = Condition(self.mon)
 614             self.limit = limit
 615             self.queue = []
 616
 617         def put(self, item):
 618             self.mon.acquire()
 619             while len(self.queue) >= self.limit:
 620                 self._note("put(%s): queue full", item)
 621                 self.wc.wait()
 622             self.queue.append(item)
 623             self._note("put(%s): appended, length now %d",
 624                        item, len(self.queue))
 625             self.rc.notify()
 626             self.mon.release()
 627
 628         def get(self):
 629             self.mon.acquire()
 630             while not self.queue:
 631                 self._note("get(): queue empty")
 632                 self.rc.wait()
 633             item = self.queue[0]
 634             del self.queue[0]
 635             self._note("get(): got %s, %d left", item, len(self.queue))
 636             self.wc.notify()
 637             self.mon.release()
 638             return item
 639
 640     class ProducerThread(Thread):
 641
 642         def __init__(self, queue, quota):
 643             Thread.__init__(self, name="Producer")
 644             self.queue = queue
 645             self.quota = quota
 646
 647         def run(self):
 648             from random import random
 649             counter = 0
 650             while counter < self.quota:
 651                 counter = counter + 1
 652                 self.queue.put("%s.%d" % (self.getName(), counter))
 653                 _sleep(random() * 0.00001)
 654
 655
 656     class ConsumerThread(Thread):
 657
 658         def __init__(self, queue, count):
 659             Thread.__init__(self, name="Consumer")
 660             self.queue = queue
 661             self.count = count
 662
 663         def run(self):
 664             while self.count > 0:
 665                 item = self.queue.get()
 666                 print item
 667                 self.count = self.count - 1
 668
 669     NP = 3
 670     QL = 4
 671     NI = 5
 672
 673     Q = BoundedQueue(QL)
 674     P = []
 675     for i in range(NP):
 676         t = ProducerThread(Q, NI)
 677         t.setName("Producer-%d" % (i+1))
 678         P.append(t)
 679     C = ConsumerThread(Q, NI*NP)
 680     for t in P:
 681         t.start()
 682         _sleep(0.000001)
 683     C.start()
 684     for t in P:
 685         t.join()
 686     C.join()
 687
 688 if __name__ == '__main__':
 689     _test()