/usr/share/pyshared/aptdaemon/lock.py is in python-aptdaemon 0.43+bzr805-0ubuntu1.
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 | #!/usr/bin/env python
# -*- coding: utf-8 -*-
"""Handles the apt system lock"""
# Copyright (C) 2010 Sebastian Heinlein <devel@glatzor.de>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
__author__ = "Sebastian Heinlein <devel@glatzor.de>"
__all__ = ("LockFailedError", "system")
import fcntl
import os
import struct
import apt_pkg
from gi.repository import GObject
from aptdaemon import enums
from aptdaemon.errors import TransactionCancelled
class LockFailedError(Exception):
"""The locking of file failed."""
def __init__(self, flock, process=None):
"""Return a new LockFailedError instance.
Keyword arguments:
flock -- the path of the file lock
process -- the process which holds the lock or None
"""
msg = "Could not acquire lock on %s." % flock
if process:
msg += " The lock is hold by %s." % process
Exception.__init__(self, msg)
self.flock = flock
self.process = process
class FileLock(object):
"""Represents a file lock."""
def __init__(self, path):
self.path = path
self.fd = None
@property
def locked(self):
return self.fd is not None
def acquire(self):
"""Return the file descriptor of the lock file or raise
LockFailedError if the lock cannot be obtained.
"""
if self.fd:
return self.fd
fd_lock = apt_pkg.get_lock(self.path)
if fd_lock < 0:
process = get_locking_process_name(self.path)
raise LockFailedError(self.path, process)
else:
self.fd = fd_lock
return fd_lock
def release(self):
"""Relase the lock."""
if self.fd:
os.close(self.fd)
self.fd = None
def get_locking_process_name(lock_path):
"""Return the name of a process which holds a lock. It will be None if
the name cannot be retrivied.
"""
try:
fd_lock_read = open(lock_path, "r")
except IOError:
return None
else:
# Get the pid of the locking application
flk = struct.pack('hhQQi', fcntl.F_WRLCK, os.SEEK_SET, 0, 0, 0)
flk_ret = fcntl.fcntl(fd_lock_read, fcntl.F_GETLK, flk)
pid = struct.unpack("hhQQi", flk_ret)[4]
# Get the command of the pid
try:
with open("/proc/%s/status" % pid, "r") as fd_status:
try:
for key, value in (line.split(":") for line in \
fd_status.readlines()):
if key == "Name":
return value.strip()
except Exception:
return None
except IOError:
return None
finally:
fd_lock_read
return None
apt_pkg.init()
#: The lock for dpkg status file
_status_dir = os.path.dirname(apt_pkg.config.find_file("Dir::State::status"))
status_lock = FileLock(os.path.join(_status_dir, "lock"))
#: The lock for the package archive
_archives_dir = apt_pkg.config.find_dir("Dir::Cache::Archives")
archive_lock = FileLock(os.path.join(_archives_dir, "lock"))
#: The lock for the repository indexes
lists_lock = FileLock(os.path.join(apt_pkg.config.find_dir("Dir::State::lists"),
"lock"))
def acquire():
"""Acquire an exclusive lock for the package management system."""
try:
for lock in archive_lock, status_lock, lists_lock:
if not lock.locked:
lock.acquire()
except:
release()
raise
def release():
"""Release an exclusive lock for the package management system."""
for lock in archive_lock, status_lock, lists_lock:
lock.release()
def wait_for_lock(trans, alt_lock=None):
"""Acquire the system lock or the optionally given one. If the lock
cannot be obtained pause the transaction in the meantime.
:param trans: the transaction
:param lock: optional alternative lock
"""
def watch_lock():
"""Helper to unpause the transaction if the lock can be obtained.
Keyword arguments:
trans -- the corresponding transaction
alt_lock -- alternative lock to the system lock
"""
try:
if alt_lock:
alt_lock.acquire()
else:
acquire()
except LockFailedError:
return True
trans.paused = False
return True
try:
if alt_lock:
alt_lock.acquire()
else:
acquire()
except LockFailedError as error:
trans.paused = True
trans.status = enums.STATUS_WAITING_LOCK
if error.process:
#TRANSLATORS: %s is the name of a package manager
msg = trans.gettext("Waiting for %s to exit")
trans.status_details = msg % error.process
lock_watch = GObject.timeout_add_seconds(3, watch_lock)
while trans.paused and not trans.cancelled:
GObject.main_context_default().iteration()
GObject.source_remove(lock_watch)
if trans.cancelled:
raise TransactionCancelled()
# vim:ts=4:sw=4:et
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