|
|
# lock.py - simple advisory locking scheme for mercurial
|
|
|
#
|
|
|
# Copyright 2005, 2006 Matt Mackall <mpm@selenic.com>
|
|
|
#
|
|
|
# This software may be used and distributed according to the terms of the
|
|
|
# GNU General Public License version 2 or any later version.
|
|
|
|
|
|
from __future__ import absolute_import
|
|
|
|
|
|
import contextlib
|
|
|
import errno
|
|
|
import os
|
|
|
import socket
|
|
|
import time
|
|
|
import warnings
|
|
|
|
|
|
from . import (
|
|
|
encoding,
|
|
|
error,
|
|
|
pycompat,
|
|
|
util,
|
|
|
)
|
|
|
|
|
|
def _getlockprefix():
|
|
|
"""Return a string which is used to differentiate pid namespaces
|
|
|
|
|
|
It's useful to detect "dead" processes and remove stale locks with
|
|
|
confidence. Typically it's just hostname. On modern linux, we include an
|
|
|
extra Linux-specific pid namespace identifier.
|
|
|
"""
|
|
|
result = socket.gethostname()
|
|
|
if pycompat.ispy3:
|
|
|
result = result.encode(pycompat.sysstr(encoding.encoding), 'replace')
|
|
|
if pycompat.sysplatform.startswith('linux'):
|
|
|
try:
|
|
|
result += '/%x' % os.stat('/proc/self/ns/pid').st_ino
|
|
|
except OSError as ex:
|
|
|
if ex.errno not in (errno.ENOENT, errno.EACCES, errno.ENOTDIR):
|
|
|
raise
|
|
|
return result
|
|
|
|
|
|
class lock(object):
|
|
|
'''An advisory lock held by one process to control access to a set
|
|
|
of files. Non-cooperating processes or incorrectly written scripts
|
|
|
can ignore Mercurial's locking scheme and stomp all over the
|
|
|
repository, so don't do that.
|
|
|
|
|
|
Typically used via localrepository.lock() to lock the repository
|
|
|
store (.hg/store/) or localrepository.wlock() to lock everything
|
|
|
else under .hg/.'''
|
|
|
|
|
|
# lock is symlink on platforms that support it, file on others.
|
|
|
|
|
|
# symlink is used because create of directory entry and contents
|
|
|
# are atomic even over nfs.
|
|
|
|
|
|
# old-style lock: symlink to pid
|
|
|
# new-style lock: symlink to hostname:pid
|
|
|
|
|
|
_host = None
|
|
|
|
|
|
def __init__(self, vfs, file, timeout=-1, releasefn=None, acquirefn=None,
|
|
|
desc=None, inheritchecker=None, parentlock=None):
|
|
|
self.vfs = vfs
|
|
|
self.f = file
|
|
|
self.held = 0
|
|
|
self.timeout = timeout
|
|
|
self.releasefn = releasefn
|
|
|
self.acquirefn = acquirefn
|
|
|
self.desc = desc
|
|
|
self._inheritchecker = inheritchecker
|
|
|
self.parentlock = parentlock
|
|
|
self._parentheld = False
|
|
|
self._inherited = False
|
|
|
self.postrelease = []
|
|
|
self.pid = self._getpid()
|
|
|
self.delay = self.lock()
|
|
|
if self.acquirefn:
|
|
|
self.acquirefn()
|
|
|
|
|
|
def __enter__(self):
|
|
|
return self
|
|
|
|
|
|
def __exit__(self, exc_type, exc_value, exc_tb):
|
|
|
self.release()
|
|
|
|
|
|
def __del__(self):
|
|
|
if self.held:
|
|
|
warnings.warn("use lock.release instead of del lock",
|
|
|
category=DeprecationWarning,
|
|
|
stacklevel=2)
|
|
|
|
|
|
# ensure the lock will be removed
|
|
|
# even if recursive locking did occur
|
|
|
self.held = 1
|
|
|
|
|
|
self.release()
|
|
|
|
|
|
def _getpid(self):
|
|
|
# wrapper around util.getpid() to make testing easier
|
|
|
return util.getpid()
|
|
|
|
|
|
def lock(self):
|
|
|
timeout = self.timeout
|
|
|
while True:
|
|
|
try:
|
|
|
self._trylock()
|
|
|
return self.timeout - timeout
|
|
|
except error.LockHeld as inst:
|
|
|
if timeout != 0:
|
|
|
time.sleep(1)
|
|
|
if timeout > 0:
|
|
|
timeout -= 1
|
|
|
continue
|
|
|
raise error.LockHeld(errno.ETIMEDOUT, inst.filename, self.desc,
|
|
|
inst.locker)
|
|
|
|
|
|
def _trylock(self):
|
|
|
if self.held:
|
|
|
self.held += 1
|
|
|
return
|
|
|
if lock._host is None:
|
|
|
lock._host = _getlockprefix()
|
|
|
lockname = '%s:%d' % (lock._host, self.pid)
|
|
|
retry = 5
|
|
|
while not self.held and retry:
|
|
|
retry -= 1
|
|
|
try:
|
|
|
self.vfs.makelock(lockname, self.f)
|
|
|
self.held = 1
|
|
|
except (OSError, IOError) as why:
|
|
|
if why.errno == errno.EEXIST:
|
|
|
locker = self._readlock()
|
|
|
# special case where a parent process holds the lock -- this
|
|
|
# is different from the pid being different because we do
|
|
|
# want the unlock and postrelease functions to be called,
|
|
|
# but the lockfile to not be removed.
|
|
|
if locker == self.parentlock:
|
|
|
self._parentheld = True
|
|
|
self.held = 1
|
|
|
return
|
|
|
locker = self._testlock(locker)
|
|
|
if locker is not None:
|
|
|
raise error.LockHeld(errno.EAGAIN,
|
|
|
self.vfs.join(self.f), self.desc,
|
|
|
locker)
|
|
|
else:
|
|
|
raise error.LockUnavailable(why.errno, why.strerror,
|
|
|
why.filename, self.desc)
|
|
|
|
|
|
def _readlock(self):
|
|
|
"""read lock and return its value
|
|
|
|
|
|
Returns None if no lock exists, pid for old-style locks, and host:pid
|
|
|
for new-style locks.
|
|
|
"""
|
|
|
try:
|
|
|
return self.vfs.readlock(self.f)
|
|
|
except (OSError, IOError) as why:
|
|
|
if why.errno == errno.ENOENT:
|
|
|
return None
|
|
|
raise
|
|
|
|
|
|
def _testlock(self, locker):
|
|
|
if locker is None:
|
|
|
return None
|
|
|
try:
|
|
|
host, pid = locker.split(":", 1)
|
|
|
except ValueError:
|
|
|
return locker
|
|
|
if host != lock._host:
|
|
|
return locker
|
|
|
try:
|
|
|
pid = int(pid)
|
|
|
except ValueError:
|
|
|
return locker
|
|
|
if util.testpid(pid):
|
|
|
return locker
|
|
|
# if locker dead, break lock. must do this with another lock
|
|
|
# held, or can race and break valid lock.
|
|
|
try:
|
|
|
l = lock(self.vfs, self.f + '.break', timeout=0)
|
|
|
self.vfs.unlink(self.f)
|
|
|
l.release()
|
|
|
except error.LockError:
|
|
|
return locker
|
|
|
|
|
|
def testlock(self):
|
|
|
"""return id of locker if lock is valid, else None.
|
|
|
|
|
|
If old-style lock, we cannot tell what machine locker is on.
|
|
|
with new-style lock, if locker is on this machine, we can
|
|
|
see if locker is alive. If locker is on this machine but
|
|
|
not alive, we can safely break lock.
|
|
|
|
|
|
The lock file is only deleted when None is returned.
|
|
|
|
|
|
"""
|
|
|
locker = self._readlock()
|
|
|
return self._testlock(locker)
|
|
|
|
|
|
@contextlib.contextmanager
|
|
|
def inherit(self):
|
|
|
"""context for the lock to be inherited by a Mercurial subprocess.
|
|
|
|
|
|
Yields a string that will be recognized by the lock in the subprocess.
|
|
|
Communicating this string to the subprocess needs to be done separately
|
|
|
-- typically by an environment variable.
|
|
|
"""
|
|
|
if not self.held:
|
|
|
raise error.LockInheritanceContractViolation(
|
|
|
'inherit can only be called while lock is held')
|
|
|
if self._inherited:
|
|
|
raise error.LockInheritanceContractViolation(
|
|
|
'inherit cannot be called while lock is already inherited')
|
|
|
if self._inheritchecker is not None:
|
|
|
self._inheritchecker()
|
|
|
if self.releasefn:
|
|
|
self.releasefn()
|
|
|
if self._parentheld:
|
|
|
lockname = self.parentlock
|
|
|
else:
|
|
|
lockname = '%s:%s' % (lock._host, self.pid)
|
|
|
self._inherited = True
|
|
|
try:
|
|
|
yield lockname
|
|
|
finally:
|
|
|
if self.acquirefn:
|
|
|
self.acquirefn()
|
|
|
self._inherited = False
|
|
|
|
|
|
def release(self):
|
|
|
"""release the lock and execute callback function if any
|
|
|
|
|
|
If the lock has been acquired multiple times, the actual release is
|
|
|
delayed to the last release call."""
|
|
|
if self.held > 1:
|
|
|
self.held -= 1
|
|
|
elif self.held == 1:
|
|
|
self.held = 0
|
|
|
if self._getpid() != self.pid:
|
|
|
# we forked, and are not the parent
|
|
|
return
|
|
|
try:
|
|
|
if self.releasefn:
|
|
|
self.releasefn()
|
|
|
finally:
|
|
|
if not self._parentheld:
|
|
|
try:
|
|
|
self.vfs.unlink(self.f)
|
|
|
except OSError:
|
|
|
pass
|
|
|
# The postrelease functions typically assume the lock is not held
|
|
|
# at all.
|
|
|
if not self._parentheld:
|
|
|
for callback in self.postrelease:
|
|
|
callback()
|
|
|
# Prevent double usage and help clear cycles.
|
|
|
self.postrelease = None
|
|
|
|
|
|
def release(*locks):
|
|
|
for lock in locks:
|
|
|
if lock is not None:
|
|
|
lock.release()
|
|
|
|
