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# lock.py
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# DNF Locking Subsystem.
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#
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# Copyright (C) 2013-2016 Red Hat, Inc.
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#
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# This copyrighted material is made available to anyone wishing to use,
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# modify, copy, or redistribute it subject to the terms and conditions of
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# the GNU General Public License v.2, or (at your option) any later version.
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# This program is distributed in the hope that it will be useful, but WITHOUT
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# ANY WARRANTY expressed or implied, including the implied warranties of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
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# Public License for more details. You should have received a copy of the
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# GNU General Public License along with this program; if not, write to the
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# Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301, USA. Any Red Hat trademarks that are incorporated in the
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# source code or documentation are not subject to the GNU General Public
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# License and may only be used or replicated with the express permission of
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# Red Hat, Inc.
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#
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from __future__ import absolute_import
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from __future__ import unicode_literals
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from dnf.exceptions import ProcessLockError, ThreadLockError, LockError
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from dnf.i18n import _
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from dnf.yum import misc
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import dnf.logging
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import dnf.util
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import errno
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import fcntl
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import hashlib
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import logging
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import os
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import threading
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import time
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logger = logging.getLogger("dnf")
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def _fit_lock_dir(dir_):
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if not dnf.util.am_i_root():
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# for regular users the best we currently do is not to clash with
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# another DNF process of the same user. Since dir_ is quite definitely
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# not writable for us, yet significant, use its hash:
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hexdir = hashlib.sha1(dir_.encode('utf-8')).hexdigest()
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dir_ = os.path.join(misc.getCacheDir(), 'locks', hexdir)
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return dir_
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def build_download_lock(cachedir, exit_on_lock):
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return ProcessLock(os.path.join(_fit_lock_dir(cachedir), 'download_lock.pid'),
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'cachedir', not exit_on_lock)
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def build_metadata_lock(cachedir, exit_on_lock):
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return ProcessLock(os.path.join(_fit_lock_dir(cachedir), 'metadata_lock.pid'),
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'metadata', not exit_on_lock)
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def build_rpmdb_lock(persistdir, exit_on_lock):
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return ProcessLock(os.path.join(_fit_lock_dir(persistdir), 'rpmdb_lock.pid'),
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'RPMDB', not exit_on_lock)
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def build_log_lock(logdir, exit_on_lock):
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return ProcessLock(os.path.join(_fit_lock_dir(logdir), 'log_lock.pid'),
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'log', not exit_on_lock)
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class ProcessLock(object):
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def __init__(self, target, description, blocking=False):
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self.blocking = blocking
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self.count = 0
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self.description = description
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self.target = target
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self.thread_lock = threading.RLock()
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def _lock_thread(self):
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if not self.thread_lock.acquire(blocking=False):
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msg = '%s already locked by a different thread' % self.description
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raise ThreadLockError(msg)
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self.count += 1
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def _try_lock(self, pid):
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fd = os.open(self.target, os.O_CREAT | os.O_RDWR, 0o644)
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try:
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try:
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fcntl.flock(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
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except OSError as e:
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if e.errno == errno.EWOULDBLOCK:
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return -1
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raise
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old_pid = os.read(fd, 20)
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if len(old_pid) == 0:
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# empty file, write our pid
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os.write(fd, str(pid).encode('utf-8'))
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return pid
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try:
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old_pid = int(old_pid)
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except ValueError:
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msg = _('Malformed lock file found: %s.\n'
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'Ensure no other dnf/yum process is running and '
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'remove the lock file manually or run '
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'systemd-tmpfiles --remove dnf.conf.') % (self.target)
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raise LockError(msg)
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if old_pid == pid:
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# already locked by this process
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return pid
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if not os.access('/proc/%d/stat' % old_pid, os.F_OK):
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# locked by a dead process, write our pid
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os.lseek(fd, 0, os.SEEK_SET)
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os.ftruncate(fd, 0)
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os.write(fd, str(pid).encode('utf-8'))
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return pid
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return old_pid
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finally:
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os.close(fd)
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def _unlock_thread(self):
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self.count -= 1
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self.thread_lock.release()
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def __enter__(self):
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dnf.util.ensure_dir(os.path.dirname(self.target))
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self._lock_thread()
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prev_pid = -1
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my_pid = os.getpid()
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pid = self._try_lock(my_pid)
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while pid != my_pid:
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if pid != -1:
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if not self.blocking:
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self._unlock_thread()
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msg = '%s already locked by %d' % (self.description, pid)
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raise ProcessLockError(msg, pid)
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if prev_pid != pid:
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msg = _('Waiting for process with pid %d to finish.') % (pid)
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logger.info(msg)
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prev_pid = pid
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time.sleep(1)
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pid = self._try_lock(my_pid)
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def __exit__(self, *exc_args):
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if self.count == 1:
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os.unlink(self.target)
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self._unlock_thread()
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