336 lines
9.5 KiB
Python
336 lines
9.5 KiB
Python
#
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# Module implementing synchronization primitives
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#
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# multiprocessing/synchronize.py
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#
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# Copyright (c) 2006-2008, R Oudkerk
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# Licensed to PSF under a Contributor Agreement.
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#
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__all__ = [
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'Lock', 'RLock', 'Semaphore', 'BoundedSemaphore', 'Condition', 'Event'
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]
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import threading
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import sys
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import _multiprocessing
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from multiprocessing.process import current_process
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from multiprocessing.util import register_after_fork, debug
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from multiprocessing.forking import assert_spawning, Popen
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from time import time as _time
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# Try to import the mp.synchronize module cleanly, if it fails
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# raise ImportError for platforms lacking a working sem_open implementation.
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# See issue 3770
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try:
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from _multiprocessing import SemLock
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except (ImportError):
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raise ImportError("This platform lacks a functioning sem_open" +
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" implementation, therefore, the required" +
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" synchronization primitives needed will not" +
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" function, see issue 3770.")
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#
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# Constants
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#
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RECURSIVE_MUTEX, SEMAPHORE = list(range(2))
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SEM_VALUE_MAX = _multiprocessing.SemLock.SEM_VALUE_MAX
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#
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# Base class for semaphores and mutexes; wraps `_multiprocessing.SemLock`
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#
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class SemLock(object):
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def __init__(self, kind, value, maxvalue):
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sl = self._semlock = _multiprocessing.SemLock(kind, value, maxvalue)
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debug('created semlock with handle %s' % sl.handle)
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self._make_methods()
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if sys.platform != 'win32':
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def _after_fork(obj):
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obj._semlock._after_fork()
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register_after_fork(self, _after_fork)
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def _make_methods(self):
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self.acquire = self._semlock.acquire
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self.release = self._semlock.release
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def __enter__(self):
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return self._semlock.__enter__()
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def __exit__(self, *args):
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return self._semlock.__exit__(*args)
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def __getstate__(self):
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assert_spawning(self)
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sl = self._semlock
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return (Popen.duplicate_for_child(sl.handle), sl.kind, sl.maxvalue)
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def __setstate__(self, state):
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self._semlock = _multiprocessing.SemLock._rebuild(*state)
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debug('recreated blocker with handle %r' % state[0])
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self._make_methods()
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#
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# Semaphore
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#
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class Semaphore(SemLock):
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def __init__(self, value=1):
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SemLock.__init__(self, SEMAPHORE, value, SEM_VALUE_MAX)
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def get_value(self):
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return self._semlock._get_value()
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def __repr__(self):
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try:
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value = self._semlock._get_value()
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except Exception:
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value = 'unknown'
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return '<Semaphore(value=%s)>' % value
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#
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# Bounded semaphore
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#
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class BoundedSemaphore(Semaphore):
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def __init__(self, value=1):
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SemLock.__init__(self, SEMAPHORE, value, value)
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def __repr__(self):
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try:
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value = self._semlock._get_value()
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except Exception:
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value = 'unknown'
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return '<BoundedSemaphore(value=%s, maxvalue=%s)>' % \
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(value, self._semlock.maxvalue)
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#
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# Non-recursive lock
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#
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class Lock(SemLock):
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def __init__(self):
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SemLock.__init__(self, SEMAPHORE, 1, 1)
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def __repr__(self):
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try:
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if self._semlock._is_mine():
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name = current_process().name
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if threading.current_thread().name != 'MainThread':
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name += '|' + threading.current_thread().name
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elif self._semlock._get_value() == 1:
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name = 'None'
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elif self._semlock._count() > 0:
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name = 'SomeOtherThread'
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else:
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name = 'SomeOtherProcess'
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except Exception:
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name = 'unknown'
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return '<Lock(owner=%s)>' % name
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#
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# Recursive lock
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#
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class RLock(SemLock):
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def __init__(self):
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SemLock.__init__(self, RECURSIVE_MUTEX, 1, 1)
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def __repr__(self):
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try:
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if self._semlock._is_mine():
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name = current_process().name
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if threading.current_thread().name != 'MainThread':
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name += '|' + threading.current_thread().name
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count = self._semlock._count()
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elif self._semlock._get_value() == 1:
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name, count = 'None', 0
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elif self._semlock._count() > 0:
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name, count = 'SomeOtherThread', 'nonzero'
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else:
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name, count = 'SomeOtherProcess', 'nonzero'
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except Exception:
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name, count = 'unknown', 'unknown'
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return '<RLock(%s, %s)>' % (name, count)
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#
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# Condition variable
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#
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class Condition(object):
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def __init__(self, lock=None):
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self._lock = lock or RLock()
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self._sleeping_count = Semaphore(0)
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self._woken_count = Semaphore(0)
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self._wait_semaphore = Semaphore(0)
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self._make_methods()
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def __getstate__(self):
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assert_spawning(self)
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return (self._lock, self._sleeping_count,
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self._woken_count, self._wait_semaphore)
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def __setstate__(self, state):
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(self._lock, self._sleeping_count,
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self._woken_count, self._wait_semaphore) = state
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self._make_methods()
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def __enter__(self):
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return self._lock.__enter__()
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def __exit__(self, *args):
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return self._lock.__exit__(*args)
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def _make_methods(self):
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self.acquire = self._lock.acquire
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self.release = self._lock.release
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def __repr__(self):
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try:
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num_waiters = (self._sleeping_count._semlock._get_value() -
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self._woken_count._semlock._get_value())
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except Exception:
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num_waiters = 'unkown'
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return '<Condition(%s, %s)>' % (self._lock, num_waiters)
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def wait(self, timeout=None):
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assert self._lock._semlock._is_mine(), \
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'must acquire() condition before using wait()'
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# indicate that this thread is going to sleep
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self._sleeping_count.release()
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# release lock
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count = self._lock._semlock._count()
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for i in range(count):
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self._lock.release()
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try:
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# wait for notification or timeout
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return self._wait_semaphore.acquire(True, timeout)
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finally:
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# indicate that this thread has woken
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self._woken_count.release()
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# reacquire lock
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for i in range(count):
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self._lock.acquire()
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def notify(self):
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assert self._lock._semlock._is_mine(), 'lock is not owned'
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assert not self._wait_semaphore.acquire(False)
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# to take account of timeouts since last notify() we subtract
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# woken_count from sleeping_count and rezero woken_count
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while self._woken_count.acquire(False):
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res = self._sleeping_count.acquire(False)
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assert res
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if self._sleeping_count.acquire(False): # try grabbing a sleeper
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self._wait_semaphore.release() # wake up one sleeper
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self._woken_count.acquire() # wait for the sleeper to wake
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# rezero _wait_semaphore in case a timeout just happened
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self._wait_semaphore.acquire(False)
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def notify_all(self):
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assert self._lock._semlock._is_mine(), 'lock is not owned'
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assert not self._wait_semaphore.acquire(False)
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# to take account of timeouts since last notify*() we subtract
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# woken_count from sleeping_count and rezero woken_count
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while self._woken_count.acquire(False):
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res = self._sleeping_count.acquire(False)
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assert res
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sleepers = 0
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while self._sleeping_count.acquire(False):
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self._wait_semaphore.release() # wake up one sleeper
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sleepers += 1
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if sleepers:
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for i in range(sleepers):
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self._woken_count.acquire() # wait for a sleeper to wake
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# rezero wait_semaphore in case some timeouts just happened
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while self._wait_semaphore.acquire(False):
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pass
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def wait_for(self, predicate, timeout=None):
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result = predicate()
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if result:
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return result
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if timeout is not None:
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endtime = _time() + timeout
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else:
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endtime = None
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waittime = None
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while not result:
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if endtime is not None:
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waittime = endtime - _time()
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if waittime <= 0:
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break
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self.wait(waittime)
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result = predicate()
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return result
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#
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# Event
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#
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class Event(object):
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def __init__(self):
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self._cond = Condition(Lock())
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self._flag = Semaphore(0)
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def is_set(self):
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self._cond.acquire()
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try:
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if self._flag.acquire(False):
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self._flag.release()
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return True
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return False
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finally:
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self._cond.release()
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def set(self):
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self._cond.acquire()
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try:
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self._flag.acquire(False)
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self._flag.release()
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self._cond.notify_all()
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finally:
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self._cond.release()
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def clear(self):
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self._cond.acquire()
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try:
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self._flag.acquire(False)
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finally:
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self._cond.release()
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def wait(self, timeout=None):
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self._cond.acquire()
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try:
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if self._flag.acquire(False):
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self._flag.release()
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else:
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self._cond.wait(timeout)
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if self._flag.acquire(False):
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self._flag.release()
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return True
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return False
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finally:
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self._cond.release()
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