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#
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# Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Google Inc.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301, USA.
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"""Module implementing the Ganeti locking code."""
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# pylint: disable=W0212
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# W0212 since e.g. LockSet methods use (a lot) the internals of
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# SharedLock
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import os |
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import select |
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import threading |
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import errno |
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import weakref |
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import logging |
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import heapq |
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import itertools |
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import time |
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from ganeti import errors |
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from ganeti import utils |
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from ganeti import compat |
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from ganeti import query |
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_EXCLUSIVE_TEXT = "exclusive"
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_SHARED_TEXT = "shared"
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_DELETED_TEXT = "deleted"
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_DEFAULT_PRIORITY = 0
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def ssynchronized(mylock, shared=0): |
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"""Shared Synchronization decorator.
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Calls the function holding the given lock, either in exclusive or shared
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mode. It requires the passed lock to be a SharedLock (or support its
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semantics).
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@type mylock: lockable object or string
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@param mylock: lock to acquire or class member name of the lock to acquire
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"""
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def wrap(fn): |
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def sync_function(*args, **kwargs): |
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if isinstance(mylock, basestring): |
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assert args, "cannot ssynchronize on non-class method: self not found" |
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# args[0] is "self"
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lock = getattr(args[0], mylock) |
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else:
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lock = mylock |
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lock.acquire(shared=shared) |
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try:
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return fn(*args, **kwargs)
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finally:
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lock.release() |
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return sync_function
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return wrap
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class _SingleNotifyPipeConditionWaiter(object): |
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"""Helper class for SingleNotifyPipeCondition
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"""
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__slots__ = [ |
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"_fd",
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"_poller",
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] |
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def __init__(self, poller, fd): |
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"""Constructor for _SingleNotifyPipeConditionWaiter
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@type poller: select.poll
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@param poller: Poller object
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@type fd: int
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@param fd: File descriptor to wait for
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"""
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object.__init__(self) |
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self._poller = poller
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self._fd = fd
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def __call__(self, timeout): |
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"""Wait for something to happen on the pipe.
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@type timeout: float or None
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@param timeout: Timeout for waiting (can be None)
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"""
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running_timeout = utils.RunningTimeout(timeout, True)
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while True: |
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remaining_time = running_timeout.Remaining() |
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if remaining_time is not None: |
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if remaining_time < 0.0: |
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break
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# Our calculation uses seconds, poll() wants milliseconds
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remaining_time *= 1000
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try:
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result = self._poller.poll(remaining_time)
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except EnvironmentError, err: |
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if err.errno != errno.EINTR:
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raise
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result = None
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# Check whether we were notified
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if result and result[0][0] == self._fd: |
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break
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class _BaseCondition(object): |
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"""Base class containing common code for conditions.
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Some of this code is taken from python's threading module.
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"""
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__slots__ = [ |
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"_lock",
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"acquire",
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"release",
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"_is_owned",
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"_acquire_restore",
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"_release_save",
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] |
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def __init__(self, lock): |
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"""Constructor for _BaseCondition.
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@type lock: threading.Lock
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@param lock: condition base lock
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"""
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object.__init__(self) |
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try:
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self._release_save = lock._release_save
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except AttributeError: |
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self._release_save = self._base_release_save |
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try:
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self._acquire_restore = lock._acquire_restore
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except AttributeError: |
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self._acquire_restore = self._base_acquire_restore |
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try:
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self._is_owned = lock.is_owned
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except AttributeError: |
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self._is_owned = self._base_is_owned |
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self._lock = lock
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# Export the lock's acquire() and release() methods
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self.acquire = lock.acquire
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self.release = lock.release
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def _base_is_owned(self): |
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"""Check whether lock is owned by current thread.
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"""
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if self._lock.acquire(0): |
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self._lock.release()
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return False |
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return True |
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def _base_release_save(self): |
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self._lock.release()
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def _base_acquire_restore(self, _): |
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self._lock.acquire()
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def _check_owned(self): |
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"""Raise an exception if the current thread doesn't own the lock.
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"""
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if not self._is_owned(): |
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raise RuntimeError("cannot work with un-aquired lock") |
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class SingleNotifyPipeCondition(_BaseCondition): |
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"""Condition which can only be notified once.
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This condition class uses pipes and poll, internally, to be able to wait for
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notification with a timeout, without resorting to polling. It is almost
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compatible with Python's threading.Condition, with the following differences:
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- notifyAll can only be called once, and no wait can happen after that
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- notify is not supported, only notifyAll
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"""
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__slots__ = [ |
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"_poller",
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"_read_fd",
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"_write_fd",
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"_nwaiters",
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"_notified",
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] |
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_waiter_class = _SingleNotifyPipeConditionWaiter |
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def __init__(self, lock): |
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"""Constructor for SingleNotifyPipeCondition
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"""
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_BaseCondition.__init__(self, lock)
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self._nwaiters = 0 |
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self._notified = False |
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self._read_fd = None |
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self._write_fd = None |
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self._poller = None |
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def _check_unnotified(self): |
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"""Throws an exception if already notified.
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"""
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if self._notified: |
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raise RuntimeError("cannot use already notified condition") |
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def _Cleanup(self): |
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"""Cleanup open file descriptors, if any.
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"""
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if self._read_fd is not None: |
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os.close(self._read_fd)
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self._read_fd = None |
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if self._write_fd is not None: |
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os.close(self._write_fd)
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self._write_fd = None |
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self._poller = None |
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def wait(self, timeout): |
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"""Wait for a notification.
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@type timeout: float or None
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@param timeout: Waiting timeout (can be None)
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"""
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self._check_owned()
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self._check_unnotified()
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self._nwaiters += 1 |
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try:
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if self._poller is None: |
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(self._read_fd, self._write_fd) = os.pipe() |
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self._poller = select.poll()
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self._poller.register(self._read_fd, select.POLLHUP) |
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wait_fn = self._waiter_class(self._poller, self._read_fd) |
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state = self._release_save()
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try:
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# Wait for notification
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wait_fn(timeout) |
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finally:
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# Re-acquire lock
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self._acquire_restore(state)
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finally:
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self._nwaiters -= 1 |
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if self._nwaiters == 0: |
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self._Cleanup()
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def notifyAll(self): # pylint: disable=C0103 |
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"""Close the writing side of the pipe to notify all waiters.
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"""
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self._check_owned()
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self._check_unnotified()
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self._notified = True |
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if self._write_fd is not None: |
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os.close(self._write_fd)
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self._write_fd = None |
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class PipeCondition(_BaseCondition): |
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"""Group-only non-polling condition with counters.
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This condition class uses pipes and poll, internally, to be able to wait for
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notification with a timeout, without resorting to polling. It is almost
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compatible with Python's threading.Condition, but only supports notifyAll and
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non-recursive locks. As an additional features it's able to report whether
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there are any waiting threads.
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"""
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__slots__ = [ |
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"_waiters",
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"_single_condition",
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] |
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_single_condition_class = SingleNotifyPipeCondition |
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def __init__(self, lock): |
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"""Initializes this class.
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"""
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_BaseCondition.__init__(self, lock)
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self._waiters = set() |
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self._single_condition = self._single_condition_class(self._lock) |
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def wait(self, timeout): |
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"""Wait for a notification.
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@type timeout: float or None
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@param timeout: Waiting timeout (can be None)
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"""
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self._check_owned()
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# Keep local reference to the pipe. It could be replaced by another thread
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# notifying while we're waiting.
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cond = self._single_condition
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self._waiters.add(threading.currentThread())
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try:
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cond.wait(timeout) |
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finally:
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self._check_owned()
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self._waiters.remove(threading.currentThread())
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def notifyAll(self): # pylint: disable=C0103 |
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"""Notify all currently waiting threads.
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"""
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self._check_owned()
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self._single_condition.notifyAll()
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self._single_condition = self._single_condition_class(self._lock) |
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def get_waiting(self): |
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"""Returns a list of all waiting threads.
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"""
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self._check_owned()
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return self._waiters |
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def has_waiting(self): |
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"""Returns whether there are active waiters.
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"""
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self._check_owned()
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return bool(self._waiters) |
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def __repr__(self): |
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return ("<%s.%s waiters=%s at %#x>" % |
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(self.__class__.__module__, self.__class__.__name__, |
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self._waiters, id(self))) |
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class _PipeConditionWithMode(PipeCondition): |
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__slots__ = [ |
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"shared",
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] |
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def __init__(self, lock, shared): |
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"""Initializes this class.
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"""
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self.shared = shared
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PipeCondition.__init__(self, lock)
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class SharedLock(object): |
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"""Implements a shared lock.
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Multiple threads can acquire the lock in a shared way by calling
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C{acquire(shared=1)}. In order to acquire the lock in an exclusive way
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threads can call C{acquire(shared=0)}.
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Notes on data structures: C{__pending} contains a priority queue (heapq) of
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all pending acquires: C{[(priority1: prioqueue1), (priority2: prioqueue2),
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...]}. Each per-priority queue contains a normal in-order list of conditions
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to be notified when the lock can be acquired. Shared locks are grouped
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together by priority and the condition for them is stored in
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C{__pending_shared} if it already exists. C{__pending_by_prio} keeps
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references for the per-priority queues indexed by priority for faster access.
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@type name: string
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@ivar name: the name of the lock
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"""
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__slots__ = [ |
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"__weakref__",
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"__deleted",
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"__exc",
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"__lock",
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"__pending",
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"__pending_by_prio",
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"__pending_shared",
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"__shr",
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"__time_fn",
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"name",
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] |
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__condition_class = _PipeConditionWithMode |
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def __init__(self, name, monitor=None, _time_fn=time.time): |
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"""Construct a new SharedLock.
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@param name: the name of the lock
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@type monitor: L{LockMonitor}
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@param monitor: Lock monitor with which to register
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"""
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object.__init__(self) |
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self.name = name
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# Used for unittesting
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self.__time_fn = _time_fn
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# Internal lock
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self.__lock = threading.Lock()
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# Queue containing waiting acquires
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self.__pending = []
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self.__pending_by_prio = {}
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self.__pending_shared = {}
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# Current lock holders
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self.__shr = set() |
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self.__exc = None |
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# is this lock in the deleted state?
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self.__deleted = False |
443 |
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# Register with lock monitor
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if monitor:
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logging.debug("Adding lock %s to monitor", name)
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monitor.RegisterLock(self)
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def __repr__(self): |
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return ("<%s.%s name=%s at %#x>" % |
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(self.__class__.__module__, self.__class__.__name__, |
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self.name, id(self))) |
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def GetLockInfo(self, requested): |
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"""Retrieves information for querying locks.
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@type requested: set
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@param requested: Requested information, see C{query.LQ_*}
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"""
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self.__lock.acquire()
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try:
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# Note: to avoid unintentional race conditions, no references to
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# modifiable objects should be returned unless they were created in this
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# function.
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mode = None
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owner_names = None
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if query.LQ_MODE in requested: |
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if self.__deleted: |
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mode = _DELETED_TEXT |
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assert not (self.__exc or self.__shr) |
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elif self.__exc: |
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mode = _EXCLUSIVE_TEXT |
475 |
elif self.__shr: |
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mode = _SHARED_TEXT |
477 |
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# Current owner(s) are wanted
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if query.LQ_OWNER in requested: |
480 |
if self.__exc: |
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owner = [self.__exc]
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else:
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owner = self.__shr
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|
485 |
if owner:
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assert not self.__deleted |
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owner_names = [i.getName() for i in owner] |
488 |
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# Pending acquires are wanted
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if query.LQ_PENDING in requested: |
491 |
pending = [] |
492 |
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# Sorting instead of copying and using heaq functions for simplicity
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for (_, prioqueue) in sorted(self.__pending): |
495 |
for cond in prioqueue: |
496 |
if cond.shared:
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pendmode = _SHARED_TEXT |
498 |
else:
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pendmode = _EXCLUSIVE_TEXT |
500 |
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# List of names will be sorted in L{query._GetLockPending}
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pending.append((pendmode, [i.getName() |
503 |
for i in cond.get_waiting()])) |
504 |
else:
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pending = None
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return [(self.name, mode, owner_names, pending)] |
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finally:
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509 |
self.__lock.release()
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511 |
def __check_deleted(self): |
512 |
"""Raises an exception if the lock has been deleted.
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513 |
|
514 |
"""
|
515 |
if self.__deleted: |
516 |
raise errors.LockError("Deleted lock %s" % self.name) |
517 |
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518 |
def __is_sharer(self): |
519 |
"""Is the current thread sharing the lock at this time?
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520 |
|
521 |
"""
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522 |
return threading.currentThread() in self.__shr |
523 |
|
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def __is_exclusive(self): |
525 |
"""Is the current thread holding the lock exclusively at this time?
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526 |
|
527 |
"""
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return threading.currentThread() == self.__exc |
529 |
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def __is_owned(self, shared=-1): |
531 |
"""Is the current thread somehow owning the lock at this time?
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532 |
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533 |
This is a private version of the function, which presumes you're holding
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the internal lock.
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535 |
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"""
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537 |
if shared < 0: |
538 |
return self.__is_sharer() or self.__is_exclusive() |
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elif shared:
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return self.__is_sharer() |
541 |
else:
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return self.__is_exclusive() |
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def is_owned(self, shared=-1): |
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"""Is the current thread somehow owning the lock at this time?
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|
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@param shared:
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- < 0: check for any type of ownership (default)
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- 0: check for exclusive ownership
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- > 0: check for shared ownership
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551 |
|
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"""
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553 |
self.__lock.acquire()
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554 |
try:
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return self.__is_owned(shared=shared) |
556 |
finally:
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557 |
self.__lock.release()
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558 |
|
559 |
#: Necessary to remain compatible with threading.Condition, which tries to
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560 |
#: retrieve a locks' "_is_owned" attribute
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_is_owned = is_owned |
562 |
|
563 |
def _count_pending(self): |
564 |
"""Returns the number of pending acquires.
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565 |
|
566 |
@rtype: int
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567 |
|
568 |
"""
|
569 |
self.__lock.acquire()
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570 |
try:
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return sum(len(prioqueue) for (_, prioqueue) in self.__pending) |
572 |
finally:
|
573 |
self.__lock.release()
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574 |
|
575 |
def _check_empty(self): |
576 |
"""Checks whether there are any pending acquires.
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577 |
|
578 |
@rtype: bool
|
579 |
|
580 |
"""
|
581 |
self.__lock.acquire()
|
582 |
try:
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583 |
# Order is important: __find_first_pending_queue modifies __pending
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584 |
(_, prioqueue) = self.__find_first_pending_queue()
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585 |
|
586 |
return not (prioqueue or |
587 |
self.__pending or |
588 |
self.__pending_by_prio or |
589 |
self.__pending_shared)
|
590 |
finally:
|
591 |
self.__lock.release()
|
592 |
|
593 |
def __do_acquire(self, shared): |
594 |
"""Actually acquire the lock.
|
595 |
|
596 |
"""
|
597 |
if shared:
|
598 |
self.__shr.add(threading.currentThread())
|
599 |
else:
|
600 |
self.__exc = threading.currentThread()
|
601 |
|
602 |
def __can_acquire(self, shared): |
603 |
"""Determine whether lock can be acquired.
|
604 |
|
605 |
"""
|
606 |
if shared:
|
607 |
return self.__exc is None |
608 |
else:
|
609 |
return len(self.__shr) == 0 and self.__exc is None |
610 |
|
611 |
def __find_first_pending_queue(self): |
612 |
"""Tries to find the topmost queued entry with pending acquires.
|
613 |
|
614 |
Removes empty entries while going through the list.
|
615 |
|
616 |
"""
|
617 |
while self.__pending: |
618 |
(priority, prioqueue) = self.__pending[0] |
619 |
|
620 |
if prioqueue:
|
621 |
return (priority, prioqueue)
|
622 |
|
623 |
# Remove empty queue
|
624 |
heapq.heappop(self.__pending)
|
625 |
del self.__pending_by_prio[priority] |
626 |
assert priority not in self.__pending_shared |
627 |
|
628 |
return (None, None) |
629 |
|
630 |
def __is_on_top(self, cond): |
631 |
"""Checks whether the passed condition is on top of the queue.
|
632 |
|
633 |
The caller must make sure the queue isn't empty.
|
634 |
|
635 |
"""
|
636 |
(_, prioqueue) = self.__find_first_pending_queue()
|
637 |
|
638 |
return cond == prioqueue[0] |
639 |
|
640 |
def __acquire_unlocked(self, shared, timeout, priority): |
641 |
"""Acquire a shared lock.
|
642 |
|
643 |
@param shared: whether to acquire in shared mode; by default an
|
644 |
exclusive lock will be acquired
|
645 |
@param timeout: maximum waiting time before giving up
|
646 |
@type priority: integer
|
647 |
@param priority: Priority for acquiring lock
|
648 |
|
649 |
"""
|
650 |
self.__check_deleted()
|
651 |
|
652 |
# We cannot acquire the lock if we already have it
|
653 |
assert not self.__is_owned(), ("double acquire() on a non-recursive lock" |
654 |
" %s" % self.name) |
655 |
|
656 |
# Remove empty entries from queue
|
657 |
self.__find_first_pending_queue()
|
658 |
|
659 |
# Check whether someone else holds the lock or there are pending acquires.
|
660 |
if not self.__pending and self.__can_acquire(shared): |
661 |
# Apparently not, can acquire lock directly.
|
662 |
self.__do_acquire(shared)
|
663 |
return True |
664 |
|
665 |
prioqueue = self.__pending_by_prio.get(priority, None) |
666 |
|
667 |
if shared:
|
668 |
# Try to re-use condition for shared acquire
|
669 |
wait_condition = self.__pending_shared.get(priority, None) |
670 |
assert (wait_condition is None or |
671 |
(wait_condition.shared and wait_condition in prioqueue)) |
672 |
else:
|
673 |
wait_condition = None
|
674 |
|
675 |
if wait_condition is None: |
676 |
if prioqueue is None: |
677 |
assert priority not in self.__pending_by_prio |
678 |
|
679 |
prioqueue = [] |
680 |
heapq.heappush(self.__pending, (priority, prioqueue))
|
681 |
self.__pending_by_prio[priority] = prioqueue
|
682 |
|
683 |
wait_condition = self.__condition_class(self.__lock, shared) |
684 |
prioqueue.append(wait_condition) |
685 |
|
686 |
if shared:
|
687 |
# Keep reference for further shared acquires on same priority. This is
|
688 |
# better than trying to find it in the list of pending acquires.
|
689 |
assert priority not in self.__pending_shared |
690 |
self.__pending_shared[priority] = wait_condition
|
691 |
|
692 |
wait_start = self.__time_fn()
|
693 |
acquired = False
|
694 |
|
695 |
try:
|
696 |
# Wait until we become the topmost acquire in the queue or the timeout
|
697 |
# expires.
|
698 |
while True: |
699 |
if self.__is_on_top(wait_condition) and self.__can_acquire(shared): |
700 |
self.__do_acquire(shared)
|
701 |
acquired = True
|
702 |
break
|
703 |
|
704 |
# A lot of code assumes blocking acquires always succeed, therefore we
|
705 |
# can never return False for a blocking acquire
|
706 |
if (timeout is not None and |
707 |
utils.TimeoutExpired(wait_start, timeout, _time_fn=self.__time_fn)):
|
708 |
break
|
709 |
|
710 |
# Wait for notification
|
711 |
wait_condition.wait(timeout) |
712 |
self.__check_deleted()
|
713 |
finally:
|
714 |
# Remove condition from queue if there are no more waiters
|
715 |
if not wait_condition.has_waiting(): |
716 |
prioqueue.remove(wait_condition) |
717 |
if wait_condition.shared:
|
718 |
# Remove from list of shared acquires if it wasn't while releasing
|
719 |
# (e.g. on lock deletion)
|
720 |
self.__pending_shared.pop(priority, None) |
721 |
|
722 |
return acquired
|
723 |
|
724 |
def acquire(self, shared=0, timeout=None, priority=None, |
725 |
test_notify=None):
|
726 |
"""Acquire a shared lock.
|
727 |
|
728 |
@type shared: integer (0/1) used as a boolean
|
729 |
@param shared: whether to acquire in shared mode; by default an
|
730 |
exclusive lock will be acquired
|
731 |
@type timeout: float
|
732 |
@param timeout: maximum waiting time before giving up
|
733 |
@type priority: integer
|
734 |
@param priority: Priority for acquiring lock
|
735 |
@type test_notify: callable or None
|
736 |
@param test_notify: Special callback function for unittesting
|
737 |
|
738 |
"""
|
739 |
if priority is None: |
740 |
priority = _DEFAULT_PRIORITY |
741 |
|
742 |
self.__lock.acquire()
|
743 |
try:
|
744 |
# We already got the lock, notify now
|
745 |
if __debug__ and callable(test_notify): |
746 |
test_notify() |
747 |
|
748 |
return self.__acquire_unlocked(shared, timeout, priority) |
749 |
finally:
|
750 |
self.__lock.release()
|
751 |
|
752 |
def downgrade(self): |
753 |
"""Changes the lock mode from exclusive to shared.
|
754 |
|
755 |
Pending acquires in shared mode on the same priority will go ahead.
|
756 |
|
757 |
"""
|
758 |
self.__lock.acquire()
|
759 |
try:
|
760 |
assert self.__is_owned(), "Lock must be owned" |
761 |
|
762 |
if self.__is_exclusive(): |
763 |
# Do nothing if the lock is already acquired in shared mode
|
764 |
self.__exc = None |
765 |
self.__do_acquire(1) |
766 |
|
767 |
# Important: pending shared acquires should only jump ahead if there
|
768 |
# was a transition from exclusive to shared, otherwise an owner of a
|
769 |
# shared lock can keep calling this function to push incoming shared
|
770 |
# acquires
|
771 |
(priority, prioqueue) = self.__find_first_pending_queue()
|
772 |
if prioqueue:
|
773 |
# Is there a pending shared acquire on this priority?
|
774 |
cond = self.__pending_shared.pop(priority, None) |
775 |
if cond:
|
776 |
assert cond.shared
|
777 |
assert cond in prioqueue |
778 |
|
779 |
# Ensure shared acquire is on top of queue
|
780 |
if len(prioqueue) > 1: |
781 |
prioqueue.remove(cond) |
782 |
prioqueue.insert(0, cond)
|
783 |
|
784 |
# Notify
|
785 |
cond.notifyAll() |
786 |
|
787 |
assert not self.__is_exclusive() |
788 |
assert self.__is_sharer() |
789 |
|
790 |
return True |
791 |
finally:
|
792 |
self.__lock.release()
|
793 |
|
794 |
def release(self): |
795 |
"""Release a Shared Lock.
|
796 |
|
797 |
You must have acquired the lock, either in shared or in exclusive mode,
|
798 |
before calling this function.
|
799 |
|
800 |
"""
|
801 |
self.__lock.acquire()
|
802 |
try:
|
803 |
assert self.__is_exclusive() or self.__is_sharer(), \ |
804 |
"Cannot release non-owned lock"
|
805 |
|
806 |
# Autodetect release type
|
807 |
if self.__is_exclusive(): |
808 |
self.__exc = None |
809 |
notify = True
|
810 |
else:
|
811 |
self.__shr.remove(threading.currentThread())
|
812 |
notify = not self.__shr |
813 |
|
814 |
# Notify topmost condition in queue if there are no owners left (for
|
815 |
# shared locks)
|
816 |
if notify:
|
817 |
self.__notify_topmost()
|
818 |
finally:
|
819 |
self.__lock.release()
|
820 |
|
821 |
def __notify_topmost(self): |
822 |
"""Notifies topmost condition in queue of pending acquires.
|
823 |
|
824 |
"""
|
825 |
(priority, prioqueue) = self.__find_first_pending_queue()
|
826 |
if prioqueue:
|
827 |
cond = prioqueue[0]
|
828 |
cond.notifyAll() |
829 |
if cond.shared:
|
830 |
# Prevent further shared acquires from sneaking in while waiters are
|
831 |
# notified
|
832 |
self.__pending_shared.pop(priority, None) |
833 |
|
834 |
def _notify_topmost(self): |
835 |
"""Exported version of L{__notify_topmost}.
|
836 |
|
837 |
"""
|
838 |
self.__lock.acquire()
|
839 |
try:
|
840 |
return self.__notify_topmost() |
841 |
finally:
|
842 |
self.__lock.release()
|
843 |
|
844 |
def delete(self, timeout=None, priority=None): |
845 |
"""Delete a Shared Lock.
|
846 |
|
847 |
This operation will declare the lock for removal. First the lock will be
|
848 |
acquired in exclusive mode if you don't already own it, then the lock
|
849 |
will be put in a state where any future and pending acquire() fail.
|
850 |
|
851 |
@type timeout: float
|
852 |
@param timeout: maximum waiting time before giving up
|
853 |
@type priority: integer
|
854 |
@param priority: Priority for acquiring lock
|
855 |
|
856 |
"""
|
857 |
if priority is None: |
858 |
priority = _DEFAULT_PRIORITY |
859 |
|
860 |
self.__lock.acquire()
|
861 |
try:
|
862 |
assert not self.__is_sharer(), "Cannot delete() a lock while sharing it" |
863 |
|
864 |
self.__check_deleted()
|
865 |
|
866 |
# The caller is allowed to hold the lock exclusively already.
|
867 |
acquired = self.__is_exclusive()
|
868 |
|
869 |
if not acquired: |
870 |
acquired = self.__acquire_unlocked(0, timeout, priority) |
871 |
|
872 |
if acquired:
|
873 |
assert self.__is_exclusive() and not self.__is_sharer(), \ |
874 |
"Lock wasn't acquired in exclusive mode"
|
875 |
|
876 |
self.__deleted = True |
877 |
self.__exc = None |
878 |
|
879 |
assert not (self.__exc or self.__shr), "Found owner during deletion" |
880 |
|
881 |
# Notify all acquires. They'll throw an error.
|
882 |
for (_, prioqueue) in self.__pending: |
883 |
for cond in prioqueue: |
884 |
cond.notifyAll() |
885 |
|
886 |
assert self.__deleted |
887 |
|
888 |
return acquired
|
889 |
finally:
|
890 |
self.__lock.release()
|
891 |
|
892 |
def _release_save(self): |
893 |
shared = self.__is_sharer()
|
894 |
self.release()
|
895 |
return shared
|
896 |
|
897 |
def _acquire_restore(self, shared): |
898 |
self.acquire(shared=shared)
|
899 |
|
900 |
|
901 |
# Whenever we want to acquire a full LockSet we pass None as the value
|
902 |
# to acquire. Hide this behind this nicely named constant.
|
903 |
ALL_SET = None
|
904 |
|
905 |
|
906 |
class _AcquireTimeout(Exception): |
907 |
"""Internal exception to abort an acquire on a timeout.
|
908 |
|
909 |
"""
|
910 |
|
911 |
|
912 |
class LockSet: |
913 |
"""Implements a set of locks.
|
914 |
|
915 |
This abstraction implements a set of shared locks for the same resource type,
|
916 |
distinguished by name. The user can lock a subset of the resources and the
|
917 |
LockSet will take care of acquiring the locks always in the same order, thus
|
918 |
preventing deadlock.
|
919 |
|
920 |
All the locks needed in the same set must be acquired together, though.
|
921 |
|
922 |
@type name: string
|
923 |
@ivar name: the name of the lockset
|
924 |
|
925 |
"""
|
926 |
def __init__(self, members, name, monitor=None): |
927 |
"""Constructs a new LockSet.
|
928 |
|
929 |
@type members: list of strings
|
930 |
@param members: initial members of the set
|
931 |
@type monitor: L{LockMonitor}
|
932 |
@param monitor: Lock monitor with which to register member locks
|
933 |
|
934 |
"""
|
935 |
assert members is not None, "members parameter is not a list" |
936 |
self.name = name
|
937 |
|
938 |
# Lock monitor
|
939 |
self.__monitor = monitor
|
940 |
|
941 |
# Used internally to guarantee coherency
|
942 |
self.__lock = SharedLock(self._GetLockName("[lockset]"), monitor=monitor) |
943 |
|
944 |
# The lockdict indexes the relationship name -> lock
|
945 |
# The order-of-locking is implied by the alphabetical order of names
|
946 |
self.__lockdict = {}
|
947 |
|
948 |
for mname in members: |
949 |
self.__lockdict[mname] = SharedLock(self._GetLockName(mname), |
950 |
monitor=monitor) |
951 |
|
952 |
# The owner dict contains the set of locks each thread owns. For
|
953 |
# performance each thread can access its own key without a global lock on
|
954 |
# this structure. It is paramount though that *no* other type of access is
|
955 |
# done to this structure (eg. no looping over its keys). *_owner helper
|
956 |
# function are defined to guarantee access is correct, but in general never
|
957 |
# do anything different than __owners[threading.currentThread()], or there
|
958 |
# will be trouble.
|
959 |
self.__owners = {}
|
960 |
|
961 |
def _GetLockName(self, mname): |
962 |
"""Returns the name for a member lock.
|
963 |
|
964 |
"""
|
965 |
return "%s/%s" % (self.name, mname) |
966 |
|
967 |
def _get_lock(self): |
968 |
"""Returns the lockset-internal lock.
|
969 |
|
970 |
"""
|
971 |
return self.__lock |
972 |
|
973 |
def _get_lockdict(self): |
974 |
"""Returns the lockset-internal lock dictionary.
|
975 |
|
976 |
Accessing this structure is only safe in single-thread usage or when the
|
977 |
lockset-internal lock is held.
|
978 |
|
979 |
"""
|
980 |
return self.__lockdict |
981 |
|
982 |
def is_owned(self): |
983 |
"""Is the current thread a current level owner?
|
984 |
|
985 |
@note: Use L{check_owned} to check if a specific lock is held
|
986 |
|
987 |
"""
|
988 |
return threading.currentThread() in self.__owners |
989 |
|
990 |
def check_owned(self, names, shared=-1): |
991 |
"""Check if locks are owned in a specific mode.
|
992 |
|
993 |
@type names: sequence or string
|
994 |
@param names: Lock names (or a single lock name)
|
995 |
@param shared: See L{SharedLock.is_owned}
|
996 |
@rtype: bool
|
997 |
@note: Use L{is_owned} to check if the current thread holds I{any} lock and
|
998 |
L{list_owned} to get the names of all owned locks
|
999 |
|
1000 |
"""
|
1001 |
if isinstance(names, basestring): |
1002 |
names = [names] |
1003 |
|
1004 |
# Avoid check if no locks are owned anyway
|
1005 |
if names and self.is_owned(): |
1006 |
candidates = [] |
1007 |
|
1008 |
# Gather references to all locks (in case they're deleted in the meantime)
|
1009 |
for lname in names: |
1010 |
try:
|
1011 |
lock = self.__lockdict[lname]
|
1012 |
except KeyError: |
1013 |
raise errors.LockError("Non-existing lock '%s' in set '%s' (it may" |
1014 |
" have been removed)" % (lname, self.name)) |
1015 |
else:
|
1016 |
candidates.append(lock) |
1017 |
|
1018 |
return compat.all(lock.is_owned(shared=shared) for lock in candidates) |
1019 |
else:
|
1020 |
return False |
1021 |
|
1022 |
def _add_owned(self, name=None): |
1023 |
"""Note the current thread owns the given lock"""
|
1024 |
if name is None: |
1025 |
if not self.is_owned(): |
1026 |
self.__owners[threading.currentThread()] = set() |
1027 |
else:
|
1028 |
if self.is_owned(): |
1029 |
self.__owners[threading.currentThread()].add(name)
|
1030 |
else:
|
1031 |
self.__owners[threading.currentThread()] = set([name]) |
1032 |
|
1033 |
def _del_owned(self, name=None): |
1034 |
"""Note the current thread owns the given lock"""
|
1035 |
|
1036 |
assert not (name is None and self.__lock.is_owned()), \ |
1037 |
"Cannot hold internal lock when deleting owner status"
|
1038 |
|
1039 |
if name is not None: |
1040 |
self.__owners[threading.currentThread()].remove(name)
|
1041 |
|
1042 |
# Only remove the key if we don't hold the set-lock as well
|
1043 |
if (not self.__lock.is_owned() and |
1044 |
not self.__owners[threading.currentThread()]): |
1045 |
del self.__owners[threading.currentThread()] |
1046 |
|
1047 |
def list_owned(self): |
1048 |
"""Get the set of resource names owned by the current thread"""
|
1049 |
if self.is_owned(): |
1050 |
return self.__owners[threading.currentThread()].copy() |
1051 |
else:
|
1052 |
return set() |
1053 |
|
1054 |
def _release_and_delete_owned(self): |
1055 |
"""Release and delete all resources owned by the current thread"""
|
1056 |
for lname in self.list_owned(): |
1057 |
lock = self.__lockdict[lname]
|
1058 |
if lock.is_owned():
|
1059 |
lock.release() |
1060 |
self._del_owned(name=lname)
|
1061 |
|
1062 |
def __names(self): |
1063 |
"""Return the current set of names.
|
1064 |
|
1065 |
Only call this function while holding __lock and don't iterate on the
|
1066 |
result after releasing the lock.
|
1067 |
|
1068 |
"""
|
1069 |
return self.__lockdict.keys() |
1070 |
|
1071 |
def _names(self): |
1072 |
"""Return a copy of the current set of elements.
|
1073 |
|
1074 |
Used only for debugging purposes.
|
1075 |
|
1076 |
"""
|
1077 |
# If we don't already own the set-level lock acquired
|
1078 |
# we'll get it and note we need to release it later.
|
1079 |
release_lock = False
|
1080 |
if not self.__lock.is_owned(): |
1081 |
release_lock = True
|
1082 |
self.__lock.acquire(shared=1) |
1083 |
try:
|
1084 |
result = self.__names()
|
1085 |
finally:
|
1086 |
if release_lock:
|
1087 |
self.__lock.release()
|
1088 |
return set(result) |
1089 |
|
1090 |
def acquire(self, names, timeout=None, shared=0, priority=None, |
1091 |
test_notify=None):
|
1092 |
"""Acquire a set of resource locks.
|
1093 |
|
1094 |
@type names: list of strings (or string)
|
1095 |
@param names: the names of the locks which shall be acquired
|
1096 |
(special lock names, or instance/node names)
|
1097 |
@type shared: integer (0/1) used as a boolean
|
1098 |
@param shared: whether to acquire in shared mode; by default an
|
1099 |
exclusive lock will be acquired
|
1100 |
@type timeout: float or None
|
1101 |
@param timeout: Maximum time to acquire all locks
|
1102 |
@type priority: integer
|
1103 |
@param priority: Priority for acquiring locks
|
1104 |
@type test_notify: callable or None
|
1105 |
@param test_notify: Special callback function for unittesting
|
1106 |
|
1107 |
@return: Set of all locks successfully acquired or None in case of timeout
|
1108 |
|
1109 |
@raise errors.LockError: when any lock we try to acquire has
|
1110 |
been deleted before we succeed. In this case none of the
|
1111 |
locks requested will be acquired.
|
1112 |
|
1113 |
"""
|
1114 |
assert timeout is None or timeout >= 0.0 |
1115 |
|
1116 |
# Check we don't already own locks at this level
|
1117 |
assert not self.is_owned(), ("Cannot acquire locks in the same set twice" |
1118 |
" (lockset %s)" % self.name) |
1119 |
|
1120 |
if priority is None: |
1121 |
priority = _DEFAULT_PRIORITY |
1122 |
|
1123 |
# We need to keep track of how long we spent waiting for a lock. The
|
1124 |
# timeout passed to this function is over all lock acquires.
|
1125 |
running_timeout = utils.RunningTimeout(timeout, False)
|
1126 |
|
1127 |
try:
|
1128 |
if names is not None: |
1129 |
# Support passing in a single resource to acquire rather than many
|
1130 |
if isinstance(names, basestring): |
1131 |
names = [names] |
1132 |
|
1133 |
return self.__acquire_inner(names, False, shared, priority, |
1134 |
running_timeout.Remaining, test_notify) |
1135 |
|
1136 |
else:
|
1137 |
# If no names are given acquire the whole set by not letting new names
|
1138 |
# being added before we release, and getting the current list of names.
|
1139 |
# Some of them may then be deleted later, but we'll cope with this.
|
1140 |
#
|
1141 |
# We'd like to acquire this lock in a shared way, as it's nice if
|
1142 |
# everybody else can use the instances at the same time. If we are
|
1143 |
# acquiring them exclusively though they won't be able to do this
|
1144 |
# anyway, though, so we'll get the list lock exclusively as well in
|
1145 |
# order to be able to do add() on the set while owning it.
|
1146 |
if not self.__lock.acquire(shared=shared, priority=priority, |
1147 |
timeout=running_timeout.Remaining()): |
1148 |
raise _AcquireTimeout()
|
1149 |
try:
|
1150 |
# note we own the set-lock
|
1151 |
self._add_owned()
|
1152 |
|
1153 |
return self.__acquire_inner(self.__names(), True, shared, priority, |
1154 |
running_timeout.Remaining, test_notify) |
1155 |
except:
|
1156 |
# We shouldn't have problems adding the lock to the owners list, but
|
1157 |
# if we did we'll try to release this lock and re-raise exception.
|
1158 |
# Of course something is going to be really wrong, after this.
|
1159 |
self.__lock.release()
|
1160 |
self._del_owned()
|
1161 |
raise
|
1162 |
|
1163 |
except _AcquireTimeout:
|
1164 |
return None |
1165 |
|
1166 |
def __acquire_inner(self, names, want_all, shared, priority, |
1167 |
timeout_fn, test_notify): |
1168 |
"""Inner logic for acquiring a number of locks.
|
1169 |
|
1170 |
@param names: Names of the locks to be acquired
|
1171 |
@param want_all: Whether all locks in the set should be acquired
|
1172 |
@param shared: Whether to acquire in shared mode
|
1173 |
@param timeout_fn: Function returning remaining timeout
|
1174 |
@param priority: Priority for acquiring locks
|
1175 |
@param test_notify: Special callback function for unittesting
|
1176 |
|
1177 |
"""
|
1178 |
acquire_list = [] |
1179 |
|
1180 |
# First we look the locks up on __lockdict. We have no way of being sure
|
1181 |
# they will still be there after, but this makes it a lot faster should
|
1182 |
# just one of them be the already wrong. Using a sorted sequence to prevent
|
1183 |
# deadlocks.
|
1184 |
for lname in sorted(utils.UniqueSequence(names)): |
1185 |
try:
|
1186 |
lock = self.__lockdict[lname] # raises KeyError if lock is not there |
1187 |
except KeyError: |
1188 |
if want_all:
|
1189 |
# We are acquiring all the set, it doesn't matter if this particular
|
1190 |
# element is not there anymore.
|
1191 |
continue
|
1192 |
|
1193 |
raise errors.LockError("Non-existing lock %s in set %s (it may have" |
1194 |
" been removed)" % (lname, self.name)) |
1195 |
|
1196 |
acquire_list.append((lname, lock)) |
1197 |
|
1198 |
# This will hold the locknames we effectively acquired.
|
1199 |
acquired = set()
|
1200 |
|
1201 |
try:
|
1202 |
# Now acquire_list contains a sorted list of resources and locks we
|
1203 |
# want. In order to get them we loop on this (private) list and
|
1204 |
# acquire() them. We gave no real guarantee they will still exist till
|
1205 |
# this is done but .acquire() itself is safe and will alert us if the
|
1206 |
# lock gets deleted.
|
1207 |
for (lname, lock) in acquire_list: |
1208 |
if __debug__ and callable(test_notify): |
1209 |
test_notify_fn = lambda: test_notify(lname)
|
1210 |
else:
|
1211 |
test_notify_fn = None
|
1212 |
|
1213 |
timeout = timeout_fn() |
1214 |
|
1215 |
try:
|
1216 |
# raises LockError if the lock was deleted
|
1217 |
acq_success = lock.acquire(shared=shared, timeout=timeout, |
1218 |
priority=priority, |
1219 |
test_notify=test_notify_fn) |
1220 |
except errors.LockError:
|
1221 |
if want_all:
|
1222 |
# We are acquiring all the set, it doesn't matter if this
|
1223 |
# particular element is not there anymore.
|
1224 |
continue
|
1225 |
|
1226 |
raise errors.LockError("Non-existing lock %s in set %s (it may" |
1227 |
" have been removed)" % (lname, self.name)) |
1228 |
|
1229 |
if not acq_success: |
1230 |
# Couldn't get lock or timeout occurred
|
1231 |
if timeout is None: |
1232 |
# This shouldn't happen as SharedLock.acquire(timeout=None) is
|
1233 |
# blocking.
|
1234 |
raise errors.LockError("Failed to get lock %s (set %s)" % |
1235 |
(lname, self.name))
|
1236 |
|
1237 |
raise _AcquireTimeout()
|
1238 |
|
1239 |
try:
|
1240 |
# now the lock cannot be deleted, we have it!
|
1241 |
self._add_owned(name=lname)
|
1242 |
acquired.add(lname) |
1243 |
|
1244 |
except:
|
1245 |
# We shouldn't have problems adding the lock to the owners list, but
|
1246 |
# if we did we'll try to release this lock and re-raise exception.
|
1247 |
# Of course something is going to be really wrong after this.
|
1248 |
if lock.is_owned():
|
1249 |
lock.release() |
1250 |
raise
|
1251 |
|
1252 |
except:
|
1253 |
# Release all owned locks
|
1254 |
self._release_and_delete_owned()
|
1255 |
raise
|
1256 |
|
1257 |
return acquired
|
1258 |
|
1259 |
def downgrade(self, names=None): |
1260 |
"""Downgrade a set of resource locks from exclusive to shared mode.
|
1261 |
|
1262 |
The locks must have been acquired in exclusive mode.
|
1263 |
|
1264 |
"""
|
1265 |
assert self.is_owned(), ("downgrade on lockset %s while not owning any" |
1266 |
" lock" % self.name) |
1267 |
|
1268 |
# Support passing in a single resource to downgrade rather than many
|
1269 |
if isinstance(names, basestring): |
1270 |
names = [names] |
1271 |
|
1272 |
owned = self.list_owned()
|
1273 |
|
1274 |
if names is None: |
1275 |
names = owned |
1276 |
else:
|
1277 |
names = set(names)
|
1278 |
assert owned.issuperset(names), \
|
1279 |
("downgrade() on unheld resources %s (set %s)" %
|
1280 |
(names.difference(owned), self.name))
|
1281 |
|
1282 |
for lockname in names: |
1283 |
self.__lockdict[lockname].downgrade()
|
1284 |
|
1285 |
# Do we own the lockset in exclusive mode?
|
1286 |
if self.__lock.is_owned(shared=0): |
1287 |
# Have all locks been downgraded?
|
1288 |
if not compat.any(lock.is_owned(shared=0) |
1289 |
for lock in self.__lockdict.values()): |
1290 |
self.__lock.downgrade()
|
1291 |
assert self.__lock.is_owned(shared=1) |
1292 |
|
1293 |
return True |
1294 |
|
1295 |
def release(self, names=None): |
1296 |
"""Release a set of resource locks, at the same level.
|
1297 |
|
1298 |
You must have acquired the locks, either in shared or in exclusive mode,
|
1299 |
before releasing them.
|
1300 |
|
1301 |
@type names: list of strings, or None
|
1302 |
@param names: the names of the locks which shall be released
|
1303 |
(defaults to all the locks acquired at that level).
|
1304 |
|
1305 |
"""
|
1306 |
assert self.is_owned(), ("release() on lock set %s while not owner" % |
1307 |
self.name)
|
1308 |
|
1309 |
# Support passing in a single resource to release rather than many
|
1310 |
if isinstance(names, basestring): |
1311 |
names = [names] |
1312 |
|
1313 |
if names is None: |
1314 |
names = self.list_owned()
|
1315 |
else:
|
1316 |
names = set(names)
|
1317 |
assert self.list_owned().issuperset(names), ( |
1318 |
"release() on unheld resources %s (set %s)" %
|
1319 |
(names.difference(self.list_owned()), self.name)) |
1320 |
|
1321 |
# First of all let's release the "all elements" lock, if set.
|
1322 |
# After this 'add' can work again
|
1323 |
if self.__lock.is_owned(): |
1324 |
self.__lock.release()
|
1325 |
self._del_owned()
|
1326 |
|
1327 |
for lockname in names: |
1328 |
# If we are sure the lock doesn't leave __lockdict without being
|
1329 |
# exclusively held we can do this...
|
1330 |
self.__lockdict[lockname].release()
|
1331 |
self._del_owned(name=lockname)
|
1332 |
|
1333 |
def add(self, names, acquired=0, shared=0): |
1334 |
"""Add a new set of elements to the set
|
1335 |
|
1336 |
@type names: list of strings
|
1337 |
@param names: names of the new elements to add
|
1338 |
@type acquired: integer (0/1) used as a boolean
|
1339 |
@param acquired: pre-acquire the new resource?
|
1340 |
@type shared: integer (0/1) used as a boolean
|
1341 |
@param shared: is the pre-acquisition shared?
|
1342 |
|
1343 |
"""
|
1344 |
# Check we don't already own locks at this level
|
1345 |
assert not self.is_owned() or self.__lock.is_owned(shared=0), \ |
1346 |
("Cannot add locks if the set %s is only partially owned, or shared" %
|
1347 |
self.name)
|
1348 |
|
1349 |
# Support passing in a single resource to add rather than many
|
1350 |
if isinstance(names, basestring): |
1351 |
names = [names] |
1352 |
|
1353 |
# If we don't already own the set-level lock acquired in an exclusive way
|
1354 |
# we'll get it and note we need to release it later.
|
1355 |
release_lock = False
|
1356 |
if not self.__lock.is_owned(): |
1357 |
release_lock = True
|
1358 |
self.__lock.acquire()
|
1359 |
|
1360 |
try:
|
1361 |
invalid_names = set(self.__names()).intersection(names) |
1362 |
if invalid_names:
|
1363 |
# This must be an explicit raise, not an assert, because assert is
|
1364 |
# turned off when using optimization, and this can happen because of
|
1365 |
# concurrency even if the user doesn't want it.
|
1366 |
raise errors.LockError("duplicate add(%s) on lockset %s" % |
1367 |
(invalid_names, self.name))
|
1368 |
|
1369 |
for lockname in names: |
1370 |
lock = SharedLock(self._GetLockName(lockname), monitor=self.__monitor) |
1371 |
|
1372 |
if acquired:
|
1373 |
# No need for priority or timeout here as this lock has just been
|
1374 |
# created
|
1375 |
lock.acquire(shared=shared) |
1376 |
# now the lock cannot be deleted, we have it!
|
1377 |
try:
|
1378 |
self._add_owned(name=lockname)
|
1379 |
except:
|
1380 |
# We shouldn't have problems adding the lock to the owners list,
|
1381 |
# but if we did we'll try to release this lock and re-raise
|
1382 |
# exception. Of course something is going to be really wrong,
|
1383 |
# after this. On the other hand the lock hasn't been added to the
|
1384 |
# __lockdict yet so no other threads should be pending on it. This
|
1385 |
# release is just a safety measure.
|
1386 |
lock.release() |
1387 |
raise
|
1388 |
|
1389 |
self.__lockdict[lockname] = lock
|
1390 |
|
1391 |
finally:
|
1392 |
# Only release __lock if we were not holding it previously.
|
1393 |
if release_lock:
|
1394 |
self.__lock.release()
|
1395 |
|
1396 |
return True |
1397 |
|
1398 |
def remove(self, names): |
1399 |
"""Remove elements from the lock set.
|
1400 |
|
1401 |
You can either not hold anything in the lockset or already hold a superset
|
1402 |
of the elements you want to delete, exclusively.
|
1403 |
|
1404 |
@type names: list of strings
|
1405 |
@param names: names of the resource to remove.
|
1406 |
|
1407 |
@return: a list of locks which we removed; the list is always
|
1408 |
equal to the names list if we were holding all the locks
|
1409 |
exclusively
|
1410 |
|
1411 |
"""
|
1412 |
# Support passing in a single resource to remove rather than many
|
1413 |
if isinstance(names, basestring): |
1414 |
names = [names] |
1415 |
|
1416 |
# If we own any subset of this lock it must be a superset of what we want
|
1417 |
# to delete. The ownership must also be exclusive, but that will be checked
|
1418 |
# by the lock itself.
|
1419 |
assert not self.is_owned() or self.list_owned().issuperset(names), ( |
1420 |
"remove() on acquired lockset %s while not owning all elements" %
|
1421 |
self.name)
|
1422 |
|
1423 |
removed = [] |
1424 |
|
1425 |
for lname in names: |
1426 |
# Calling delete() acquires the lock exclusively if we don't already own
|
1427 |
# it, and causes all pending and subsequent lock acquires to fail. It's
|
1428 |
# fine to call it out of order because delete() also implies release(),
|
1429 |
# and the assertion above guarantees that if we either already hold
|
1430 |
# everything we want to delete, or we hold none.
|
1431 |
try:
|
1432 |
self.__lockdict[lname].delete()
|
1433 |
removed.append(lname) |
1434 |
except (KeyError, errors.LockError): |
1435 |
# This cannot happen if we were already holding it, verify:
|
1436 |
assert not self.is_owned(), ("remove failed while holding lockset %s" % |
1437 |
self.name)
|
1438 |
else:
|
1439 |
# If no LockError was raised we are the ones who deleted the lock.
|
1440 |
# This means we can safely remove it from lockdict, as any further or
|
1441 |
# pending delete() or acquire() will fail (and nobody can have the lock
|
1442 |
# since before our call to delete()).
|
1443 |
#
|
1444 |
# This is done in an else clause because if the exception was thrown
|
1445 |
# it's the job of the one who actually deleted it.
|
1446 |
del self.__lockdict[lname] |
1447 |
# And let's remove it from our private list if we owned it.
|
1448 |
if self.is_owned(): |
1449 |
self._del_owned(name=lname)
|
1450 |
|
1451 |
return removed
|
1452 |
|
1453 |
|
1454 |
# Locking levels, must be acquired in increasing order.
|
1455 |
# Current rules are:
|
1456 |
# - at level LEVEL_CLUSTER resides the Big Ganeti Lock (BGL) which must be
|
1457 |
# acquired before performing any operation, either in shared or in exclusive
|
1458 |
# mode. acquiring the BGL in exclusive mode is discouraged and should be
|
1459 |
# avoided.
|
1460 |
# - at levels LEVEL_NODE and LEVEL_INSTANCE reside node and instance locks.
|
1461 |
# If you need more than one node, or more than one instance, acquire them at
|
1462 |
# the same time.
|
1463 |
LEVEL_CLUSTER = 0
|
1464 |
LEVEL_INSTANCE = 1
|
1465 |
LEVEL_NODEGROUP = 2
|
1466 |
LEVEL_NODE = 3
|
1467 |
LEVEL_NODE_RES = 4
|
1468 |
LEVEL_NETWORK = 5
|
1469 |
|
1470 |
LEVELS = [ |
1471 |
LEVEL_CLUSTER, |
1472 |
LEVEL_INSTANCE, |
1473 |
LEVEL_NODEGROUP, |
1474 |
LEVEL_NODE, |
1475 |
LEVEL_NODE_RES, |
1476 |
LEVEL_NETWORK, |
1477 |
] |
1478 |
|
1479 |
# Lock levels which are modifiable
|
1480 |
LEVELS_MOD = frozenset([
|
1481 |
LEVEL_NODE_RES, |
1482 |
LEVEL_NODE, |
1483 |
LEVEL_NODEGROUP, |
1484 |
LEVEL_INSTANCE, |
1485 |
LEVEL_NETWORK, |
1486 |
]) |
1487 |
|
1488 |
#: Lock level names (make sure to use singular form)
|
1489 |
LEVEL_NAMES = { |
1490 |
LEVEL_CLUSTER: "cluster",
|
1491 |
LEVEL_INSTANCE: "instance",
|
1492 |
LEVEL_NODEGROUP: "nodegroup",
|
1493 |
LEVEL_NODE: "node",
|
1494 |
LEVEL_NODE_RES: "node-res",
|
1495 |
LEVEL_NETWORK: "network",
|
1496 |
} |
1497 |
|
1498 |
# Constant for the big ganeti lock
|
1499 |
BGL = "BGL"
|
1500 |
|
1501 |
|
1502 |
class GanetiLockManager: |
1503 |
"""The Ganeti Locking Library
|
1504 |
|
1505 |
The purpose of this small library is to manage locking for ganeti clusters
|
1506 |
in a central place, while at the same time doing dynamic checks against
|
1507 |
possible deadlocks. It will also make it easier to transition to a different
|
1508 |
lock type should we migrate away from python threads.
|
1509 |
|
1510 |
"""
|
1511 |
_instance = None
|
1512 |
|
1513 |
def __init__(self, nodes, nodegroups, instances, networks): |
1514 |
"""Constructs a new GanetiLockManager object.
|
1515 |
|
1516 |
There should be only a GanetiLockManager object at any time, so this
|
1517 |
function raises an error if this is not the case.
|
1518 |
|
1519 |
@param nodes: list of node names
|
1520 |
@param nodegroups: list of nodegroup uuids
|
1521 |
@param instances: list of instance names
|
1522 |
|
1523 |
"""
|
1524 |
assert self.__class__._instance is None, \ |
1525 |
"double GanetiLockManager instance"
|
1526 |
|
1527 |
self.__class__._instance = self |
1528 |
|
1529 |
self._monitor = LockMonitor()
|
1530 |
|
1531 |
# The keyring contains all the locks, at their level and in the correct
|
1532 |
# locking order.
|
1533 |
self.__keyring = {
|
1534 |
LEVEL_CLUSTER: LockSet([BGL], "cluster", monitor=self._monitor), |
1535 |
LEVEL_NODE: LockSet(nodes, "node", monitor=self._monitor), |
1536 |
LEVEL_NODE_RES: LockSet(nodes, "node-res", monitor=self._monitor), |
1537 |
LEVEL_NODEGROUP: LockSet(nodegroups, "nodegroup", monitor=self._monitor), |
1538 |
LEVEL_INSTANCE: LockSet(instances, "instance", monitor=self._monitor), |
1539 |
LEVEL_NETWORK: LockSet(networks, "network", monitor=self._monitor), |
1540 |
} |
1541 |
|
1542 |
assert compat.all(ls.name == LEVEL_NAMES[level]
|
1543 |
for (level, ls) in self.__keyring.items()) |
1544 |
|
1545 |
def AddToLockMonitor(self, provider): |
1546 |
"""Registers a new lock with the monitor.
|
1547 |
|
1548 |
See L{LockMonitor.RegisterLock}.
|
1549 |
|
1550 |
"""
|
1551 |
return self._monitor.RegisterLock(provider) |
1552 |
|
1553 |
def QueryLocks(self, fields): |
1554 |
"""Queries information from all locks.
|
1555 |
|
1556 |
See L{LockMonitor.QueryLocks}.
|
1557 |
|
1558 |
"""
|
1559 |
return self._monitor.QueryLocks(fields) |
1560 |
|
1561 |
def _names(self, level): |
1562 |
"""List the lock names at the given level.
|
1563 |
|
1564 |
This can be used for debugging/testing purposes.
|
1565 |
|
1566 |
@param level: the level whose list of locks to get
|
1567 |
|
1568 |
"""
|
1569 |
assert level in LEVELS, "Invalid locking level %s" % level |
1570 |
return self.__keyring[level]._names() |
1571 |
|
1572 |
def is_owned(self, level): |
1573 |
"""Check whether we are owning locks at the given level
|
1574 |
|
1575 |
"""
|
1576 |
return self.__keyring[level].is_owned() |
1577 |
|
1578 |
def list_owned(self, level): |
1579 |
"""Get the set of owned locks at the given level
|
1580 |
|
1581 |
"""
|
1582 |
return self.__keyring[level].list_owned() |
1583 |
|
1584 |
def check_owned(self, level, names, shared=-1): |
1585 |
"""Check if locks at a certain level are owned in a specific mode.
|
1586 |
|
1587 |
@see: L{LockSet.check_owned}
|
1588 |
|
1589 |
"""
|
1590 |
return self.__keyring[level].check_owned(names, shared=shared) |
1591 |
|
1592 |
def _upper_owned(self, level): |
1593 |
"""Check that we don't own any lock at a level greater than the given one.
|
1594 |
|
1595 |
"""
|
1596 |
# This way of checking only works if LEVELS[i] = i, which we check for in
|
1597 |
# the test cases.
|
1598 |
return compat.any((self.is_owned(l) for l in LEVELS[level + 1:])) |
1599 |
|
1600 |
def _BGL_owned(self): # pylint: disable=C0103 |
1601 |
"""Check if the current thread owns the BGL.
|
1602 |
|
1603 |
Both an exclusive or a shared acquisition work.
|
1604 |
|
1605 |
"""
|
1606 |
return BGL in self.__keyring[LEVEL_CLUSTER].list_owned() |
1607 |
|
1608 |
@staticmethod
|
1609 |
def _contains_BGL(level, names): # pylint: disable=C0103 |
1610 |
"""Check if the level contains the BGL.
|
1611 |
|
1612 |
Check if acting on the given level and set of names will change
|
1613 |
the status of the Big Ganeti Lock.
|
1614 |
|
1615 |
"""
|
1616 |
return level == LEVEL_CLUSTER and (names is None or BGL in names) |
1617 |
|
1618 |
def acquire(self, level, names, timeout=None, shared=0, priority=None): |
1619 |
"""Acquire a set of resource locks, at the same level.
|
1620 |
|
1621 |
@type level: member of locking.LEVELS
|
1622 |
@param level: the level at which the locks shall be acquired
|
1623 |
@type names: list of strings (or string)
|
1624 |
@param names: the names of the locks which shall be acquired
|
1625 |
(special lock names, or instance/node names)
|
1626 |
@type shared: integer (0/1) used as a boolean
|
1627 |
@param shared: whether to acquire in shared mode; by default
|
1628 |
an exclusive lock will be acquired
|
1629 |
@type timeout: float
|
1630 |
@param timeout: Maximum time to acquire all locks
|
1631 |
@type priority: integer
|
1632 |
@param priority: Priority for acquiring lock
|
1633 |
|
1634 |
"""
|
1635 |
assert level in LEVELS, "Invalid locking level %s" % level |
1636 |
|
1637 |
# Check that we are either acquiring the Big Ganeti Lock or we already own
|
1638 |
# it. Some "legacy" opcodes need to be sure they are run non-concurrently
|
1639 |
# so even if we've migrated we need to at least share the BGL to be
|
1640 |
# compatible with them. Of course if we own the BGL exclusively there's no
|
1641 |
# point in acquiring any other lock, unless perhaps we are half way through
|
1642 |
# the migration of the current opcode.
|
1643 |
assert (self._contains_BGL(level, names) or self._BGL_owned()), ( |
1644 |
"You must own the Big Ganeti Lock before acquiring any other")
|
1645 |
|
1646 |
# Check we don't own locks at the same or upper levels.
|
1647 |
assert not self._upper_owned(level), ("Cannot acquire locks at a level" |
1648 |
" while owning some at a greater one")
|
1649 |
|
1650 |
# Acquire the locks in the set.
|
1651 |
return self.__keyring[level].acquire(names, shared=shared, timeout=timeout, |
1652 |
priority=priority) |
1653 |
|
1654 |
def downgrade(self, level, names=None): |
1655 |
"""Downgrade a set of resource locks from exclusive to shared mode.
|
1656 |
|
1657 |
You must have acquired the locks in exclusive mode.
|
1658 |
|
1659 |
@type level: member of locking.LEVELS
|
1660 |
@param level: the level at which the locks shall be downgraded
|
1661 |
@type names: list of strings, or None
|
1662 |
@param names: the names of the locks which shall be downgraded
|
1663 |
(defaults to all the locks acquired at the level)
|
1664 |
|
1665 |
"""
|
1666 |
assert level in LEVELS, "Invalid locking level %s" % level |
1667 |
|
1668 |
return self.__keyring[level].downgrade(names=names) |
1669 |
|
1670 |
def release(self, level, names=None): |
1671 |
"""Release a set of resource locks, at the same level.
|
1672 |
|
1673 |
You must have acquired the locks, either in shared or in exclusive
|
1674 |
mode, before releasing them.
|
1675 |
|
1676 |
@type level: member of locking.LEVELS
|
1677 |
@param level: the level at which the locks shall be released
|
1678 |
@type names: list of strings, or None
|
1679 |
@param names: the names of the locks which shall be released
|
1680 |
(defaults to all the locks acquired at that level)
|
1681 |
|
1682 |
"""
|
1683 |
assert level in LEVELS, "Invalid locking level %s" % level |
1684 |
assert (not self._contains_BGL(level, names) or |
1685 |
not self._upper_owned(LEVEL_CLUSTER)), ( |
1686 |
"Cannot release the Big Ganeti Lock while holding something"
|
1687 |
" at upper levels (%r)" %
|
1688 |
(utils.CommaJoin(["%s=%r" % (LEVEL_NAMES[i], self.list_owned(i)) |
1689 |
for i in self.__keyring.keys()]), )) |
1690 |
|
1691 |
# Release will complain if we don't own the locks already
|
1692 |
return self.__keyring[level].release(names) |
1693 |
|
1694 |
def add(self, level, names, acquired=0, shared=0): |
1695 |
"""Add locks at the specified level.
|
1696 |
|
1697 |
@type level: member of locking.LEVELS_MOD
|
1698 |
@param level: the level at which the locks shall be added
|
1699 |
@type names: list of strings
|
1700 |
@param names: names of the locks to acquire
|
1701 |
@type acquired: integer (0/1) used as a boolean
|
1702 |
@param acquired: whether to acquire the newly added locks
|
1703 |
@type shared: integer (0/1) used as a boolean
|
1704 |
@param shared: whether the acquisition will be shared
|
1705 |
|
1706 |
"""
|
1707 |
assert level in LEVELS_MOD, "Invalid or immutable level %s" % level |
1708 |
assert self._BGL_owned(), ("You must own the BGL before performing other" |
1709 |
" operations")
|
1710 |
assert not self._upper_owned(level), ("Cannot add locks at a level" |
1711 |
" while owning some at a greater one")
|
1712 |
return self.__keyring[level].add(names, acquired=acquired, shared=shared) |
1713 |
|
1714 |
def remove(self, level, names): |
1715 |
"""Remove locks from the specified level.
|
1716 |
|
1717 |
You must either already own the locks you are trying to remove
|
1718 |
exclusively or not own any lock at an upper level.
|
1719 |
|
1720 |
@type level: member of locking.LEVELS_MOD
|
1721 |
@param level: the level at which the locks shall be removed
|
1722 |
@type names: list of strings
|
1723 |
@param names: the names of the locks which shall be removed
|
1724 |
(special lock names, or instance/node names)
|
1725 |
|
1726 |
"""
|
1727 |
assert level in LEVELS_MOD, "Invalid or immutable level %s" % level |
1728 |
assert self._BGL_owned(), ("You must own the BGL before performing other" |
1729 |
" operations")
|
1730 |
# Check we either own the level or don't own anything from here
|
1731 |
# up. LockSet.remove() will check the case in which we don't own
|
1732 |
# all the needed resources, or we have a shared ownership.
|
1733 |
assert self.is_owned(level) or not self._upper_owned(level), ( |
1734 |
"Cannot remove locks at a level while not owning it or"
|
1735 |
" owning some at a greater one")
|
1736 |
return self.__keyring[level].remove(names) |
1737 |
|
1738 |
|
1739 |
def _MonitorSortKey((item, idx, num)): |
1740 |
"""Sorting key function.
|
1741 |
|
1742 |
Sort by name, registration order and then order of information. This provides
|
1743 |
a stable sort order over different providers, even if they return the same
|
1744 |
name.
|
1745 |
|
1746 |
"""
|
1747 |
(name, _, _, _) = item |
1748 |
|
1749 |
return (utils.NiceSortKey(name), num, idx)
|
1750 |
|
1751 |
|
1752 |
class LockMonitor(object): |
1753 |
_LOCK_ATTR = "_lock"
|
1754 |
|
1755 |
def __init__(self): |
1756 |
"""Initializes this class.
|
1757 |
|
1758 |
"""
|
1759 |
self._lock = SharedLock("LockMonitor") |
1760 |
|
1761 |
# Counter for stable sorting
|
1762 |
self._counter = itertools.count(0) |
1763 |
|
1764 |
# Tracked locks. Weak references are used to avoid issues with circular
|
1765 |
# references and deletion.
|
1766 |
self._locks = weakref.WeakKeyDictionary()
|
1767 |
|
1768 |
@ssynchronized(_LOCK_ATTR)
|
1769 |
def RegisterLock(self, provider): |
1770 |
"""Registers a new lock.
|
1771 |
|
1772 |
@param provider: Object with a callable method named C{GetLockInfo}, taking
|
1773 |
a single C{set} containing the requested information items
|
1774 |
@note: It would be nicer to only receive the function generating the
|
1775 |
requested information but, as it turns out, weak references to bound
|
1776 |
methods (e.g. C{self.GetLockInfo}) are tricky; there are several
|
1777 |
workarounds, but none of the ones I found works properly in combination
|
1778 |
with a standard C{WeakKeyDictionary}
|
1779 |
|
1780 |
"""
|
1781 |
assert provider not in self._locks, "Duplicate registration" |
1782 |
|
1783 |
# There used to be a check for duplicate names here. As it turned out, when
|
1784 |
# a lock is re-created with the same name in a very short timeframe, the
|
1785 |
# previous instance might not yet be removed from the weakref dictionary.
|
1786 |
# By keeping track of the order of incoming registrations, a stable sort
|
1787 |
# ordering can still be guaranteed.
|
1788 |
|
1789 |
self._locks[provider] = self._counter.next() |
1790 |
|
1791 |
def _GetLockInfo(self, requested): |
1792 |
"""Get information from all locks.
|
1793 |
|
1794 |
"""
|
1795 |
# Must hold lock while getting consistent list of tracked items
|
1796 |
self._lock.acquire(shared=1) |
1797 |
try:
|
1798 |
items = self._locks.items()
|
1799 |
finally:
|
1800 |
self._lock.release()
|
1801 |
|
1802 |
return [(info, idx, num)
|
1803 |
for (provider, num) in items |
1804 |
for (idx, info) in enumerate(provider.GetLockInfo(requested))] |
1805 |
|
1806 |
def _Query(self, fields): |
1807 |
"""Queries information from all locks.
|
1808 |
|
1809 |
@type fields: list of strings
|
1810 |
@param fields: List of fields to return
|
1811 |
|
1812 |
"""
|
1813 |
qobj = query.Query(query.LOCK_FIELDS, fields) |
1814 |
|
1815 |
# Get all data with internal lock held and then sort by name and incoming
|
1816 |
# order
|
1817 |
lockinfo = sorted(self._GetLockInfo(qobj.RequestedData()), |
1818 |
key=_MonitorSortKey) |
1819 |
|
1820 |
# Extract lock information and build query data
|
1821 |
return (qobj, query.LockQueryData(map(compat.fst, lockinfo))) |
1822 |
|
1823 |
def QueryLocks(self, fields): |
1824 |
"""Queries information from all locks.
|
1825 |
|
1826 |
@type fields: list of strings
|
1827 |
@param fields: List of fields to return
|
1828 |
|
1829 |
"""
|
1830 |
(qobj, ctx) = self._Query(fields)
|
1831 |
|
1832 |
# Prepare query response
|
1833 |
return query.GetQueryResponse(qobj, ctx)
|