/usr/lib/python3/dist-packages/beaker/synchronization.py is in python3-beaker 1.6.3-1.1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 | """Synchronization functions.
File- and mutex-based mutual exclusion synchronizers are provided,
as well as a name-based mutex which locks within an application
based on a string name.
"""
import os
import sys
import tempfile
try:
import threading as _threading
except ImportError:
import dummy_threading as _threading
# check for fcntl module
try:
sys.getwindowsversion()
has_flock = False
except:
try:
import fcntl
has_flock = True
except ImportError:
has_flock = False
from beaker import util
from beaker.exceptions import LockError
__all__ = ["file_synchronizer", "mutex_synchronizer", "null_synchronizer",
"NameLock", "_threading"]
class NameLock(object):
"""a proxy for an RLock object that is stored in a name based
registry.
Multiple threads can get a reference to the same RLock based on the
name alone, and synchronize operations related to that name.
"""
locks = util.WeakValuedRegistry()
class NLContainer(object):
def __init__(self, reentrant):
if reentrant:
self.lock = _threading.RLock()
else:
self.lock = _threading.Lock()
def __call__(self):
return self.lock
def __init__(self, identifier = None, reentrant = False):
if identifier is None:
self._lock = NameLock.NLContainer(reentrant)
else:
self._lock = NameLock.locks.get(identifier, NameLock.NLContainer,
reentrant)
def acquire(self, wait = True):
return self._lock().acquire(wait)
def release(self):
self._lock().release()
_synchronizers = util.WeakValuedRegistry()
def _synchronizer(identifier, cls, **kwargs):
return _synchronizers.sync_get((identifier, cls), cls, identifier, **kwargs)
def file_synchronizer(identifier, **kwargs):
if not has_flock or 'lock_dir' not in kwargs:
return mutex_synchronizer(identifier)
else:
return _synchronizer(identifier, FileSynchronizer, **kwargs)
def mutex_synchronizer(identifier, **kwargs):
return _synchronizer(identifier, ConditionSynchronizer, **kwargs)
class null_synchronizer(object):
"""A 'null' synchronizer, which provides the :class:`.SynchronizerImpl` interface
without any locking.
"""
def acquire_write_lock(self, wait=True):
return True
def acquire_read_lock(self):
pass
def release_write_lock(self):
pass
def release_read_lock(self):
pass
acquire = acquire_write_lock
release = release_write_lock
class SynchronizerImpl(object):
"""Base class for a synchronization object that allows
multiple readers, single writers.
"""
def __init__(self):
self._state = util.ThreadLocal()
class SyncState(object):
__slots__ = 'reentrantcount', 'writing', 'reading'
def __init__(self):
self.reentrantcount = 0
self.writing = False
self.reading = False
def state(self):
if not self._state.has():
state = SynchronizerImpl.SyncState()
self._state.put(state)
return state
else:
return self._state.get()
state = property(state)
def release_read_lock(self):
state = self.state
if state.writing:
raise LockError("lock is in writing state")
if not state.reading:
raise LockError("lock is not in reading state")
if state.reentrantcount == 1:
self.do_release_read_lock()
state.reading = False
state.reentrantcount -= 1
def acquire_read_lock(self, wait = True):
state = self.state
if state.writing:
raise LockError("lock is in writing state")
if state.reentrantcount == 0:
x = self.do_acquire_read_lock(wait)
if (wait or x):
state.reentrantcount += 1
state.reading = True
return x
elif state.reading:
state.reentrantcount += 1
return True
def release_write_lock(self):
state = self.state
if state.reading:
raise LockError("lock is in reading state")
if not state.writing:
raise LockError("lock is not in writing state")
if state.reentrantcount == 1:
self.do_release_write_lock()
state.writing = False
state.reentrantcount -= 1
release = release_write_lock
def acquire_write_lock(self, wait = True):
state = self.state
if state.reading:
raise LockError("lock is in reading state")
if state.reentrantcount == 0:
x = self.do_acquire_write_lock(wait)
if (wait or x):
state.reentrantcount += 1
state.writing = True
return x
elif state.writing:
state.reentrantcount += 1
return True
acquire = acquire_write_lock
def do_release_read_lock(self):
raise NotImplementedError()
def do_acquire_read_lock(self):
raise NotImplementedError()
def do_release_write_lock(self):
raise NotImplementedError()
def do_acquire_write_lock(self):
raise NotImplementedError()
class FileSynchronizer(SynchronizerImpl):
"""A synchronizer which locks using flock().
"""
def __init__(self, identifier, lock_dir):
super(FileSynchronizer, self).__init__()
self._filedescriptor = util.ThreadLocal()
if lock_dir is None:
lock_dir = tempfile.gettempdir()
else:
lock_dir = lock_dir
self.filename = util.encoded_path(
lock_dir,
[identifier],
extension='.lock'
)
def _filedesc(self):
return self._filedescriptor.get()
_filedesc = property(_filedesc)
def _open(self, mode):
filedescriptor = self._filedesc
if filedescriptor is None:
filedescriptor = os.open(self.filename, mode)
self._filedescriptor.put(filedescriptor)
return filedescriptor
def do_acquire_read_lock(self, wait):
filedescriptor = self._open(os.O_CREAT | os.O_RDONLY)
if not wait:
try:
fcntl.flock(filedescriptor, fcntl.LOCK_SH | fcntl.LOCK_NB)
return True
except IOError:
os.close(filedescriptor)
self._filedescriptor.remove()
return False
else:
fcntl.flock(filedescriptor, fcntl.LOCK_SH)
return True
def do_acquire_write_lock(self, wait):
filedescriptor = self._open(os.O_CREAT | os.O_WRONLY)
if not wait:
try:
fcntl.flock(filedescriptor, fcntl.LOCK_EX | fcntl.LOCK_NB)
return True
except IOError:
os.close(filedescriptor)
self._filedescriptor.remove()
return False
else:
fcntl.flock(filedescriptor, fcntl.LOCK_EX)
return True
def do_release_read_lock(self):
self._release_all_locks()
def do_release_write_lock(self):
self._release_all_locks()
def _release_all_locks(self):
filedescriptor = self._filedesc
if filedescriptor is not None:
fcntl.flock(filedescriptor, fcntl.LOCK_UN)
os.close(filedescriptor)
self._filedescriptor.remove()
class ConditionSynchronizer(SynchronizerImpl):
"""a synchronizer using a Condition."""
def __init__(self, identifier):
super(ConditionSynchronizer, self).__init__()
# counts how many asynchronous methods are executing
self.async = 0
# pointer to thread that is the current sync operation
self.current_sync_operation = None
# condition object to lock on
self.condition = _threading.Condition(_threading.Lock())
def do_acquire_read_lock(self, wait = True):
self.condition.acquire()
try:
# see if a synchronous operation is waiting to start
# or is already running, in which case we wait (or just
# give up and return)
if wait:
while self.current_sync_operation is not None:
self.condition.wait()
else:
if self.current_sync_operation is not None:
return False
self.async += 1
finally:
self.condition.release()
if not wait:
return True
def do_release_read_lock(self):
self.condition.acquire()
try:
self.async -= 1
# check if we are the last asynchronous reader thread
# out the door.
if self.async == 0:
# yes. so if a sync operation is waiting, notifyAll to wake
# it up
if self.current_sync_operation is not None:
self.condition.notifyAll()
elif self.async < 0:
raise LockError("Synchronizer error - too many "
"release_read_locks called")
finally:
self.condition.release()
def do_acquire_write_lock(self, wait = True):
self.condition.acquire()
try:
# here, we are not a synchronous reader, and after returning,
# assuming waiting or immediate availability, we will be.
if wait:
# if another sync is working, wait
while self.current_sync_operation is not None:
self.condition.wait()
else:
# if another sync is working,
# we dont want to wait, so forget it
if self.current_sync_operation is not None:
return False
# establish ourselves as the current sync
# this indicates to other read/write operations
# that they should wait until this is None again
self.current_sync_operation = _threading.currentThread()
# now wait again for asyncs to finish
if self.async > 0:
if wait:
# wait
self.condition.wait()
else:
# we dont want to wait, so forget it
self.current_sync_operation = None
return False
finally:
self.condition.release()
if not wait:
return True
def do_release_write_lock(self):
self.condition.acquire()
try:
if self.current_sync_operation is not _threading.currentThread():
raise LockError("Synchronizer error - current thread doesnt "
"have the write lock")
# reset the current sync operation so
# another can get it
self.current_sync_operation = None
# tell everyone to get ready
self.condition.notifyAll()
finally:
# everyone go !!
self.condition.release()
|