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Current Path : /lib/python3.6/site-packages/dnf/ |
Current File : //lib/python3.6/site-packages/dnf/lock.py |
# lock.py # DNF Locking Subsystem. # # Copyright (C) 2013-2016 Red Hat, Inc. # # This copyrighted material is made available to anyone wishing to use, # modify, copy, or redistribute it subject to the terms and conditions of # the GNU General Public License v.2, or (at your option) any later version. # This program is distributed in the hope that it will be useful, but WITHOUT # ANY WARRANTY expressed or implied, including the implied warranties 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. Any Red Hat trademarks that are incorporated in the # source code or documentation are not subject to the GNU General Public # License and may only be used or replicated with the express permission of # Red Hat, Inc. # from __future__ import absolute_import from __future__ import unicode_literals from dnf.exceptions import ProcessLockError, ThreadLockError, LockError from dnf.i18n import _ from dnf.yum import misc import dnf.logging import dnf.util import errno import fcntl import hashlib import logging import os import threading import time logger = logging.getLogger("dnf") def _fit_lock_dir(dir_): if not dnf.util.am_i_root(): # for regular users the best we currently do is not to clash with # another DNF process of the same user. Since dir_ is quite definitely # not writable for us, yet significant, use its hash: hexdir = hashlib.sha1(dir_.encode('utf-8')).hexdigest() dir_ = os.path.join(misc.getCacheDir(), 'locks', hexdir) return dir_ def build_download_lock(cachedir, exit_on_lock): return ProcessLock(os.path.join(_fit_lock_dir(cachedir), 'download_lock.pid'), 'cachedir', not exit_on_lock) def build_metadata_lock(cachedir, exit_on_lock): return ProcessLock(os.path.join(_fit_lock_dir(cachedir), 'metadata_lock.pid'), 'metadata', not exit_on_lock) def build_rpmdb_lock(persistdir, exit_on_lock): return ProcessLock(os.path.join(_fit_lock_dir(persistdir), 'rpmdb_lock.pid'), 'RPMDB', not exit_on_lock) def build_log_lock(logdir, exit_on_lock): return ProcessLock(os.path.join(_fit_lock_dir(logdir), 'log_lock.pid'), 'log', not exit_on_lock) class ProcessLock(object): def __init__(self, target, description, blocking=False): self.blocking = blocking self.count = 0 self.description = description self.target = target self.thread_lock = threading.RLock() def _lock_thread(self): if not self.thread_lock.acquire(blocking=False): msg = '%s already locked by a different thread' % self.description raise ThreadLockError(msg) self.count += 1 def _try_lock(self, pid): fd = os.open(self.target, os.O_CREAT | os.O_RDWR, 0o644) try: try: fcntl.flock(fd, fcntl.LOCK_EX | fcntl.LOCK_NB) except OSError as e: if e.errno == errno.EWOULDBLOCK: return -1 raise old_pid = os.read(fd, 20) if len(old_pid) == 0: # empty file, write our pid os.write(fd, str(pid).encode('utf-8')) return pid try: old_pid = int(old_pid) except ValueError: msg = _('Malformed lock file found: %s.\n' 'Ensure no other dnf/yum process is running and ' 'remove the lock file manually or run ' 'systemd-tmpfiles --remove dnf.conf.') % (self.target) raise LockError(msg) if old_pid == pid: # already locked by this process return pid if not os.access('/proc/%d/stat' % old_pid, os.F_OK): # locked by a dead process, write our pid os.lseek(fd, 0, os.SEEK_SET) os.ftruncate(fd, 0) os.write(fd, str(pid).encode('utf-8')) return pid return old_pid finally: os.close(fd) def _unlock_thread(self): self.count -= 1 self.thread_lock.release() def __enter__(self): dnf.util.ensure_dir(os.path.dirname(self.target)) self._lock_thread() prev_pid = -1 my_pid = os.getpid() pid = self._try_lock(my_pid) while pid != my_pid: if pid != -1: if not self.blocking: self._unlock_thread() msg = '%s already locked by %d' % (self.description, pid) raise ProcessLockError(msg, pid) if prev_pid != pid: msg = _('Waiting for process with pid %d to finish.') % (pid) logger.info(msg) prev_pid = pid time.sleep(1) pid = self._try_lock(my_pid) def __exit__(self, *exc_args): if self.count == 1: os.unlink(self.target) self._unlock_thread()