#
# Module implementing synchronization primitives
#
# multiprocessing/synchronize.py
#
# Copyright (c) 2006-2008, R Oudkerk
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# 1. Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in the
# documentation and/or other materials provided with the distribution.
# 3. Neither the name of author nor the names of any contributors may be
# used to endorse or promote products derived from this software
# without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.
#

__all__ = [
'Lock', 'RLock', 'Semaphore', 'BoundedSemaphore', 'Condition', 'Event'
]

import threading
import os
import sys

from time import time as _time, sleep as _sleep

import _multiprocessing
from multiprocessing.process import current_process
from multiprocessing.util import Finalize, register_after_fork, debug
from multiprocessing.forking import assert_spawning, Popen

# 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 = 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 = 'unknown'
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 xrange(count):
self._lock.release()

try:
# wait for notification or timeout
self._wait_semaphore.acquire(True, timeout)
finally:
# indicate that this thread has woken
self._woken_count.release()

# reacquire lock
for i in xrange(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 xrange(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

#
# 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()