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EDIT :: synchronize.py

# # Module implementing synchronization primitives # # multiprocessing/synchronize.py # # Copyright (c) 2006-2008, R Oudkerk # Licensed to PSF under a Contributor Agreement. # __all__ = [ 'Lock', 'RLock', 'Semaphore', 'BoundedSemaphore', 'Condition', 'Event' ] import threading import sys import tempfile import _multiprocessing import time from . import context from . import process from . import util # Try to import the mp.synchronize module cleanly, if it fails # raise ImportError for platforms lacking a working sem_open implementation. # See issue 3770 try: from _multiprocessing import SemLock, sem_unlink except (ImportError): raise ImportError("This platform lacks a functioning sem_open" + " implementation, therefore, the required" + " synchronization primitives needed will not" + " function, see issue 3770.") # # Constants # RECURSIVE_MUTEX, SEMAPHORE = list(range(2)) SEM_VALUE_MAX = _multiprocessing.SemLock.SEM_VALUE_MAX # # Base class for semaphores and mutexes; wraps `_multiprocessing.SemLock` # class SemLock(object): _rand = tempfile._RandomNameSequence() def __init__(self, kind, value, maxvalue, *, ctx): if ctx is None: ctx = context._default_context.get_context() name = ctx.get_start_method() unlink_now = sys.platform == 'win32' or name == 'fork' for i in range(100): try: sl = self._semlock = _multiprocessing.SemLock( kind, value, maxvalue, self._make_name(), unlink_now) except FileExistsError: pass else: break else: raise FileExistsError('cannot find name for semaphore') util.debug('created semlock with handle %s' % sl.handle) self._make_methods() if sys.platform != 'win32': def _after_fork(obj): obj._semlock._after_fork() util.register_after_fork(self, _after_fork) if self._semlock.name is not None: # We only get here if we are on Unix with forking # disabled. When the object is garbage collected or the # process shuts down we unlink the semaphore name from .semaphore_tracker import register register(self._semlock.name) util.Finalize(self, SemLock._cleanup, (self._semlock.name,), exitpriority=0) @staticmethod def _cleanup(name): from .semaphore_tracker import unregister sem_unlink(name) unregister(name) def _make_methods(self): self.acquire = self._semlock.acquire self.release = self._semlock.release def __enter__(self): return self._semlock.__enter__() def __exit__(self, *args): return self._semlock.__exit__(*args) def __getstate__(self): context.assert_spawning(self) sl = self._semlock if sys.platform == 'win32': h = context.get_spawning_popen().duplicate_for_child(sl.handle) else: h = sl.handle return (h, sl.kind, sl.maxvalue, sl.name) def __setstate__(self, state): self._semlock = _multiprocessing.SemLock._rebuild(*state) util.debug('recreated blocker with handle %r' % state[0]) self._make_methods() @staticmethod def _make_name(): return '%s-%s' % (process.current_process()._config['semprefix'], next(SemLock._rand)) # # Semaphore # class Semaphore(SemLock): def __init__(self, value=1, *, ctx): SemLock.__init__(self, SEMAPHORE, value, SEM_VALUE_MAX, ctx=ctx) def get_value(self): return self._semlock._get_value() def __repr__(self): try: value = self._semlock._get_value() except Exception: value = 'unknown' return '<%s(value=%s)>' % (self.__class__.__name__, value) # # Bounded semaphore # class BoundedSemaphore(Semaphore): def __init__(self, value=1, *, ctx): SemLock.__init__(self, SEMAPHORE, value, value, ctx=ctx) def __repr__(self): try: value = self._semlock._get_value() except Exception: value = 'unknown' return '<%s(value=%s, maxvalue=%s)>' % \ (self.__class__.__name__, value, self._semlock.maxvalue) # # Non-recursive lock # class Lock(SemLock): def __init__(self, *, ctx): SemLock.__init__(self, SEMAPHORE, 1, 1, ctx=ctx) def __repr__(self): try: if self._semlock._is_mine(): name = process.current_process().name if threading.current_thread().name != 'MainThread': name += '|' + threading.current_thread().name elif self._semlock._get_value() == 1: name = 'None' elif self._semlock._count() > 0: name = 'SomeOtherThread' else: name = 'SomeOtherProcess' except Exception: name = 'unknown' return '<%s(owner=%s)>' % (self.__class__.__name__, name) # # Recursive lock # class RLock(SemLock): def __init__(self, *, ctx): SemLock.__init__(self, RECURSIVE_MUTEX, 1, 1, ctx=ctx) def __repr__(self): try: if self._semlock._is_mine(): name = process.current_process().name if threading.current_thread().name != 'MainThread': name += '|' + threading.current_thread().name count = self._semlock._count() elif self._semlock._get_value() == 1: name, count = 'None', 0 elif self._semlock._count() > 0: name, count = 'SomeOtherThread', 'nonzero' else: name, count = 'SomeOtherProcess', 'nonzero' except Exception: name, count = 'unknown', 'unknown' return '<%s(%s, %s)>' % (self.__class__.__name__, name, count) # # Condition variable # class Condition(object): def __init__(self, lock=None, *, ctx): self._lock = lock or ctx.RLock() self._sleeping_count = ctx.Semaphore(0) self._woken_count = ctx.Semaphore(0) self._wait_semaphore = ctx.Semaphore(0) self._make_methods() def __getstate__(self): context.assert_spawning(self) return (self._lock, self._sleeping_count, self._woken_count, self._wait_semaphore) def __setstate__(self, state): (self._lock, self._sleeping_count, self._woken_count, self._wait_semaphore) = state self._make_methods() def __enter__(self): return self._lock.__enter__() def __exit__(self, *args): return self._lock.__exit__(*args) def _make_methods(self): self.acquire = self._lock.acquire self.release = self._lock.release def __repr__(self): try: num_waiters = (self._sleeping_count._semlock._get_value() - self._woken_count._semlock._get_value()) except Exception: num_waiters = 'unknown' return '<%s(%s, %s)>' % (self.__class__.__name__, self._lock, num_waiters) def wait(self, timeout=None): assert self._lock._semlock._is_mine(), \ 'must acquire() condition before using wait()' # indicate that this thread is going to sleep self._sleeping_count.release() # release lock count = self._lock._semlock._count() for i in range(count): self._lock.release() try: # wait for notification or timeout return self._wait_semaphore.acquire(True, timeout) finally: # indicate that this thread has woken self._woken_count.release() # reacquire lock for i in range(count): self._lock.acquire() def notify(self): assert self._lock._semlock._is_mine(), 'lock is not owned' assert not self._wait_semaphore.acquire(False) # to take account of timeouts since last notify() we subtract # woken_count from sleeping_count and rezero woken_count while self._woken_count.acquire(False): res = self._sleeping_count.acquire(False) assert res if self._sleeping_count.acquire(False): # try grabbing a sleeper self._wait_semaphore.release() # wake up one sleeper self._woken_count.acquire() # wait for the sleeper to wake # rezero _wait_semaphore in case a timeout just happened self._wait_semaphore.acquire(False) def notify_all(self): assert self._lock._semlock._is_mine(), 'lock is not owned' assert not self._wait_semaphore.acquire(False) # to take account of timeouts since last notify*() we subtract # woken_count from sleeping_count and rezero woken_count while self._woken_count.acquire(False): res = self._sleeping_count.acquire(False) assert res sleepers = 0 while self._sleeping_count.acquire(False): self._wait_semaphore.release() # wake up one sleeper sleepers += 1 if sleepers: for i in range(sleepers): self._woken_count.acquire() # wait for a sleeper to wake # rezero wait_semaphore in case some timeouts just happened while self._wait_semaphore.acquire(False): pass def wait_for(self, predicate, timeout=None): result = predicate() if result: return result if timeout is not None: endtime = time.monotonic() + timeout else: endtime = None waittime = None while not result: if endtime is not None: waittime = endtime - time.monotonic() if waittime <= 0: break self.wait(waittime) result = predicate() return result # # Event # class Event(object): def __init__(self, *, ctx): self._cond = ctx.Condition(ctx.Lock()) self._flag = ctx.Semaphore(0) def is_set(self): with self._cond: if self._flag.acquire(False): self._flag.release() return True return False def set(self): with self._cond: self._flag.acquire(False) self._flag.release() self._cond.notify_all() def clear(self): with self._cond: self._flag.acquire(False) def wait(self, timeout=None): with self._cond: if self._flag.acquire(False): self._flag.release() else: self._cond.wait(timeout) if self._flag.acquire(False): self._flag.release() return True return False # # Barrier # class Barrier(threading.Barrier): def __init__(self, parties, action=None, timeout=None, *, ctx): import struct from .heap import BufferWrapper wrapper = BufferWrapper(struct.calcsize('i') * 2) cond = ctx.Condition() self.__setstate__((parties, action, timeout, cond, wrapper)) self._state = 0 self._count = 0 def __setstate__(self, state): (self._parties, self._action, self._timeout, self._cond, self._wrapper) = state self._array = self._wrapper.create_memoryview().cast('i') def __getstate__(self): return (self._parties, self._action, self._timeout, self._cond, self._wrapper) @property def _state(self): return self._array[0] @_state.setter def _state(self, value): self._array[0] = value @property def _count(self): return self._array[1] @_count.setter def _count(self, value): self._array[1] = value

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