| # |
| # 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 _multiprocessing |
| from multiprocessing.process import current_process |
| from multiprocessing.util import register_after_fork, debug |
| from multiprocessing.forking import assert_spawning, Popen |
| from time import time as _time |
| |
| # 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 |
| 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): |
| |
| def __init__(self, kind, value, maxvalue): |
| sl = self._semlock = _multiprocessing.SemLock(kind, value, maxvalue) |
| debug('created semlock with handle %s' % sl.handle) |
| self._make_methods() |
| |
| if sys.platform != 'win32': |
| def _after_fork(obj): |
| obj._semlock._after_fork() |
| register_after_fork(self, _after_fork) |
| |
| 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): |
| assert_spawning(self) |
| sl = self._semlock |
| return (Popen.duplicate_for_child(sl.handle), sl.kind, sl.maxvalue) |
| |
| def __setstate__(self, state): |
| self._semlock = _multiprocessing.SemLock._rebuild(*state) |
| debug('recreated blocker with handle %r' % state[0]) |
| self._make_methods() |
| |
| # |
| # Semaphore |
| # |
| |
| class Semaphore(SemLock): |
| |
| def __init__(self, value=1): |
| SemLock.__init__(self, SEMAPHORE, value, SEM_VALUE_MAX) |
| |
| def get_value(self): |
| return self._semlock._get_value() |
| |
| def __repr__(self): |
| try: |
| value = self._semlock._get_value() |
| except Exception: |
| value = 'unknown' |
| return '<Semaphore(value=%s)>' % value |
| |
| # |
| # Bounded semaphore |
| # |
| |
| class BoundedSemaphore(Semaphore): |
| |
| def __init__(self, value=1): |
| SemLock.__init__(self, SEMAPHORE, value, value) |
| |
| def __repr__(self): |
| try: |
| value = self._semlock._get_value() |
| except Exception: |
| value = 'unknown' |
| return '<BoundedSemaphore(value=%s, maxvalue=%s)>' % \ |
| (value, self._semlock.maxvalue) |
| |
| # |
| # Non-recursive lock |
| # |
| |
| class Lock(SemLock): |
| |
| def __init__(self): |
| SemLock.__init__(self, SEMAPHORE, 1, 1) |
| |
| def __repr__(self): |
| try: |
| if self._semlock._is_mine(): |
| name = 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 '<Lock(owner=%s)>' % name |
| |
| # |
| # Recursive lock |
| # |
| |
| class RLock(SemLock): |
| |
| def __init__(self): |
| SemLock.__init__(self, RECURSIVE_MUTEX, 1, 1) |
| |
| def __repr__(self): |
| try: |
| if self._semlock._is_mine(): |
| name = 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 '<RLock(%s, %s)>' % (name, count) |
| |
| # |
| # Condition variable |
| # |
| |
| class Condition(object): |
| |
| def __init__(self, lock=None): |
| self._lock = lock or RLock() |
| self._sleeping_count = Semaphore(0) |
| self._woken_count = Semaphore(0) |
| self._wait_semaphore = Semaphore(0) |
| self._make_methods() |
| |
| def __getstate__(self): |
| 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 = 'unkown' |
| return '<Condition(%s, %s)>' % (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() + timeout |
| else: |
| endtime = None |
| waittime = None |
| while not result: |
| if endtime is not None: |
| waittime = endtime - _time() |
| if waittime <= 0: |
| break |
| self.wait(waittime) |
| result = predicate() |
| return result |
| |
| # |
| # Event |
| # |
| |
| class Event(object): |
| |
| def __init__(self): |
| self._cond = Condition(Lock()) |
| self._flag = Semaphore(0) |
| |
| def is_set(self): |
| self._cond.acquire() |
| try: |
| if self._flag.acquire(False): |
| self._flag.release() |
| return True |
| return False |
| finally: |
| self._cond.release() |
| |
| def set(self): |
| self._cond.acquire() |
| try: |
| self._flag.acquire(False) |
| self._flag.release() |
| self._cond.notify_all() |
| finally: |
| self._cond.release() |
| |
| def clear(self): |
| self._cond.acquire() |
| try: |
| self._flag.acquire(False) |
| finally: |
| self._cond.release() |
| |
| def wait(self, timeout=None): |
| self._cond.acquire() |
| try: |
| 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 |
| finally: |
| self._cond.release() |