395 lines
11 KiB
Python
395 lines
11 KiB
Python
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#
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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 tempfile
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import _multiprocessing
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import time
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from . import context
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from . import process
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from . import util
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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, sem_unlink
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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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_rand = tempfile._RandomNameSequence()
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def __init__(self, kind, value, maxvalue, *, ctx):
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if ctx is None:
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ctx = context._default_context.get_context()
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name = ctx.get_start_method()
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unlink_now = sys.platform == 'win32' or name == 'fork'
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for i in range(100):
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try:
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sl = self._semlock = _multiprocessing.SemLock(
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kind, value, maxvalue, self._make_name(),
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unlink_now)
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except FileExistsError:
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pass
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else:
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break
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else:
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raise FileExistsError('cannot find name for semaphore')
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util.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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util.register_after_fork(self, _after_fork)
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if self._semlock.name is not None:
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# We only get here if we are on Unix with forking
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# disabled. When the object is garbage collected or the
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# process shuts down we unlink the semaphore name
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from .resource_tracker import register
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register(self._semlock.name, "semaphore")
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util.Finalize(self, SemLock._cleanup, (self._semlock.name,),
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exitpriority=0)
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@staticmethod
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def _cleanup(name):
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from .resource_tracker import unregister
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sem_unlink(name)
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unregister(name, "semaphore")
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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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context.assert_spawning(self)
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sl = self._semlock
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if sys.platform == 'win32':
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h = context.get_spawning_popen().duplicate_for_child(sl.handle)
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else:
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h = sl.handle
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return (h, sl.kind, sl.maxvalue, sl.name)
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def __setstate__(self, state):
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self._semlock = _multiprocessing.SemLock._rebuild(*state)
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util.debug('recreated blocker with handle %r' % state[0])
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self._make_methods()
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@staticmethod
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def _make_name():
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return '%s-%s' % (process.current_process()._config['semprefix'],
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next(SemLock._rand))
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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, *, ctx):
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SemLock.__init__(self, SEMAPHORE, value, SEM_VALUE_MAX, ctx=ctx)
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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 '<%s(value=%s)>' % (self.__class__.__name__, 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, *, ctx):
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SemLock.__init__(self, SEMAPHORE, value, value, ctx=ctx)
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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 '<%s(value=%s, maxvalue=%s)>' % \
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(self.__class__.__name__, 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, *, ctx):
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SemLock.__init__(self, SEMAPHORE, 1, 1, ctx=ctx)
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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 = process.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 '<%s(owner=%s)>' % (self.__class__.__name__, 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, *, ctx):
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SemLock.__init__(self, RECURSIVE_MUTEX, 1, 1, ctx=ctx)
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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 = process.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 '<%s(%s, %s)>' % (self.__class__.__name__, 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, *, ctx):
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self._lock = lock or ctx.RLock()
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self._sleeping_count = ctx.Semaphore(0)
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self._woken_count = ctx.Semaphore(0)
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self._wait_semaphore = ctx.Semaphore(0)
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self._make_methods()
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def __getstate__(self):
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context.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 = 'unknown'
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return '<%s(%s, %s)>' % (self.__class__.__name__, 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, n=1):
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assert self._lock._semlock._is_mine(), 'lock is not owned'
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assert not self._wait_semaphore.acquire(
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False), ('notify: Should not have been able to acquire '
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+ '_wait_semaphore')
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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, ('notify: Bug in sleeping_count.acquire'
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+ '- res should not be False')
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sleepers = 0
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while sleepers < n and 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 notify_all(self):
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self.notify(n=sys.maxsize)
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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.monotonic() + 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.monotonic()
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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, *, ctx):
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self._cond = ctx.Condition(ctx.Lock())
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self._flag = ctx.Semaphore(0)
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def is_set(self):
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with self._cond:
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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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def set(self):
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with self._cond:
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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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def clear(self):
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with self._cond:
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self._flag.acquire(False)
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def wait(self, timeout=None):
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with self._cond:
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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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#
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# Barrier
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#
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class Barrier(threading.Barrier):
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def __init__(self, parties, action=None, timeout=None, *, ctx):
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import struct
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from .heap import BufferWrapper
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wrapper = BufferWrapper(struct.calcsize('i') * 2)
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cond = ctx.Condition()
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self.__setstate__((parties, action, timeout, cond, wrapper))
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self._state = 0
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self._count = 0
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def __setstate__(self, state):
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(self._parties, self._action, self._timeout,
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self._cond, self._wrapper) = state
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self._array = self._wrapper.create_memoryview().cast('i')
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def __getstate__(self):
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return (self._parties, self._action, self._timeout,
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self._cond, self._wrapper)
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@property
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def _state(self):
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return self._array[0]
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@_state.setter
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def _state(self, value):
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self._array[0] = value
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@property
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def _count(self):
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return self._array[1]
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@_count.setter
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def _count(self, value):
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self._array[1] = value
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