1
# Copyright (C) 2005-2010 Canonical Ltd
1
# Copyright (C) 2005 Canonical Ltd
3
3
# This program is free software; you can redistribute it and/or modify
4
4
# it under the terms of the GNU General Public License as published by
5
5
# the Free Software Foundation; either version 2 of the License, or
6
6
# (at your option) any later version.
8
8
# This program is distributed in the hope that it will be useful,
9
9
# but WITHOUT ANY WARRANTY; without even the implied warranty of
10
10
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11
11
# GNU General Public License for more details.
13
13
# You should have received a copy of the GNU General Public License
14
14
# along with this program; if not, write to the Free Software
15
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
18
"""Locking using OS file locks or file existence.
20
Note: This method of locking is generally deprecated in favour of LockDir, but
21
is used to lock local WorkingTrees, and by some old formats. It's accessed
22
through Transport.lock_read(), etc.
15
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20
This only does local locking using OS locks for now.
24
22
This module causes two methods, lock() and unlock() to be defined in
25
23
any way that works on the current platform.
27
25
It is not specified whether these locks are reentrant (i.e. can be
28
26
taken repeatedly by a single process) or whether they exclude
29
different threads in a single process. That reentrancy is provided by
27
different threads in a single process.
29
Eventually we may need to use some kind of lock representation that
30
will work on a dumb filesystem without actual locking primitives.
32
32
This defines two classes: ReadLock and WriteLock, which can be
33
33
implemented in different ways on different platforms. Both have an
48
from bzrlib.hooks import HookPoint, Hooks
51
class LockHooks(Hooks):
55
self.create_hook(HookPoint('lock_acquired',
56
"Called with a bzrlib.lock.LockResult when a physical lock is "
57
"acquired.", (1, 8), None))
58
self.create_hook(HookPoint('lock_released',
59
"Called with a bzrlib.lock.LockResult when a physical lock is "
60
"released.", (1, 8), None))
61
self.create_hook(HookPoint('lock_broken',
62
"Called with a bzrlib.lock.LockResult when a physical lock is "
63
"broken.", (1, 15), None))
67
"""Base class for locks.
69
:cvar hooks: Hook dictionary for operations on locks.
75
class LockResult(object):
76
"""Result of an operation on a lock; passed to a hook"""
78
def __init__(self, lock_url, details=None):
79
"""Create a lock result for lock with optional details about the lock."""
80
self.lock_url = lock_url
81
self.details = details
83
def __eq__(self, other):
84
return self.lock_url == other.lock_url and self.details == other.details
87
return '%s(%s%s)' % (self.__class__.__name__,
88
self.lock_url, self.details)
91
def cant_unlock_not_held(locked_object):
92
"""An attempt to unlock failed because the object was not locked.
94
This provides a policy point from which we can generate either a warning
97
# This is typically masking some other error and called from a finally
98
# block, so it's useful to have the option not to generate a new error
99
# here. You can use -Werror to make it fatal. It should possibly also
101
if 'unlock' in debug.debug_flags:
102
warnings.warn("%r is already unlocked" % (locked_object,),
105
raise errors.LockNotHeld(locked_object)
115
have_ctypes_win32 = False
116
if sys.platform == 'win32':
119
import win32file, pywintypes, winerror
126
have_ctypes_win32 = True
131
class _OSLock(object):
41
from bzrlib.trace import mutter, note, warning
42
from bzrlib.errors import LockError
44
class _base_Lock(object):
137
45
def _open(self, filename, filemode):
138
self.filename = osutils.realpath(filename)
140
self.f = open(self.filename, filemode)
48
self.f = open(filename, filemode)
142
50
except IOError, e:
143
if e.errno in (errno.EACCES, errno.EPERM):
144
raise errors.LockFailed(self.filename, str(e))
145
51
if e.errno != errno.ENOENT:
148
54
# maybe this is an old branch (before may 2005)
149
trace.mutter("trying to create missing lock %r", self.filename)
151
self.f = open(self.filename, 'wb+')
55
mutter("trying to create missing branch lock %r" % filename)
57
self.f = open(filename, 'wb')
155
"""Clear the self.f attribute cleanly."""
160
61
def __del__(self):
162
63
from warnings import warn
163
64
warn("lock on %r not released" % self.f)
167
69
raise NotImplementedError()
175
class _fcntl_FileLock(_OSLock):
76
############################################################
83
class _fcntl_FileLock(_base_Lock):
178
87
fcntl.lockf(self.f, fcntl.LOCK_UN)
182
92
class _fcntl_WriteLock(_fcntl_FileLock):
186
93
def __init__(self, filename):
187
super(_fcntl_WriteLock, self).__init__()
188
# Check we can grab a lock before we actually open the file.
189
self.filename = osutils.realpath(filename)
190
if self.filename in _fcntl_WriteLock._open_locks:
192
raise errors.LockContention(self.filename)
193
if self.filename in _fcntl_ReadLock._open_locks:
194
if 'strict_locks' in debug.debug_flags:
196
raise errors.LockContention(self.filename)
198
trace.mutter('Write lock taken w/ an open read lock on: %s'
201
self._open(self.filename, 'rb+')
202
# reserve a slot for this lock - even if the lockf call fails,
203
# at this point unlock() will be called, because self.f is set.
204
# TODO: make this fully threadsafe, if we decide we care.
205
_fcntl_WriteLock._open_locks.add(self.filename)
207
# LOCK_NB will cause IOError to be raised if we can't grab a
209
fcntl.lockf(self.f, fcntl.LOCK_EX | fcntl.LOCK_NB)
211
if e.errno in (errno.EAGAIN, errno.EACCES):
212
# We couldn't grab the lock
214
# we should be more precise about whats a locking
215
# error and whats a random-other error
216
raise errors.LockContention(self.filename, e)
219
_fcntl_WriteLock._open_locks.remove(self.filename)
95
fcntl.lockf(self._open(filename, 'wb'), fcntl.LOCK_EX)
223
100
class _fcntl_ReadLock(_fcntl_FileLock):
227
def __init__(self, filename):
228
super(_fcntl_ReadLock, self).__init__()
229
self.filename = osutils.realpath(filename)
230
if self.filename in _fcntl_WriteLock._open_locks:
231
if 'strict_locks' in debug.debug_flags:
232
# We raise before calling _open so we don't need to
234
raise errors.LockContention(self.filename)
236
trace.mutter('Read lock taken w/ an open write lock on: %s'
238
_fcntl_ReadLock._open_locks.setdefault(self.filename, 0)
239
_fcntl_ReadLock._open_locks[self.filename] += 1
240
self._open(filename, 'rb')
242
# LOCK_NB will cause IOError to be raised if we can't grab a
244
fcntl.lockf(self.f, fcntl.LOCK_SH | fcntl.LOCK_NB)
246
# we should be more precise about whats a locking
247
# error and whats a random-other error
248
raise errors.LockContention(self.filename, e)
251
count = _fcntl_ReadLock._open_locks[self.filename]
253
del _fcntl_ReadLock._open_locks[self.filename]
255
_fcntl_ReadLock._open_locks[self.filename] = count - 1
258
def temporary_write_lock(self):
259
"""Try to grab a write lock on the file.
261
On platforms that support it, this will upgrade to a write lock
262
without unlocking the file.
263
Otherwise, this will release the read lock, and try to acquire a
266
:return: A token which can be used to switch back to a read lock.
268
if self.filename in _fcntl_WriteLock._open_locks:
269
raise AssertionError('file already locked: %r'
272
wlock = _fcntl_TemporaryWriteLock(self)
273
except errors.LockError:
274
# We didn't unlock, so we can just return 'self'
279
class _fcntl_TemporaryWriteLock(_OSLock):
280
"""A token used when grabbing a temporary_write_lock.
282
Call restore_read_lock() when you are done with the write lock.
285
def __init__(self, read_lock):
286
super(_fcntl_TemporaryWriteLock, self).__init__()
287
self._read_lock = read_lock
288
self.filename = read_lock.filename
290
count = _fcntl_ReadLock._open_locks[self.filename]
292
# Something else also has a read-lock, so we cannot grab a
294
raise errors.LockContention(self.filename)
296
if self.filename in _fcntl_WriteLock._open_locks:
297
raise AssertionError('file already locked: %r'
300
# See if we can open the file for writing. Another process might
301
# have a read lock. We don't use self._open() because we don't want
302
# to create the file if it exists. That would have already been
303
# done by _fcntl_ReadLock
305
new_f = open(self.filename, 'rb+')
307
if e.errno in (errno.EACCES, errno.EPERM):
308
raise errors.LockFailed(self.filename, str(e))
311
# LOCK_NB will cause IOError to be raised if we can't grab a
313
fcntl.lockf(new_f, fcntl.LOCK_EX | fcntl.LOCK_NB)
315
# TODO: Raise a more specific error based on the type of error
316
raise errors.LockContention(self.filename, e)
317
_fcntl_WriteLock._open_locks.add(self.filename)
321
def restore_read_lock(self):
322
"""Restore the original ReadLock."""
323
# For fcntl, since we never released the read lock, just release the
324
# write lock, and return the original lock.
325
fcntl.lockf(self.f, fcntl.LOCK_UN)
327
_fcntl_WriteLock._open_locks.remove(self.filename)
328
# Avoid reference cycles
329
read_lock = self._read_lock
330
self._read_lock = None
334
_lock_classes.append(('fcntl', _fcntl_WriteLock, _fcntl_ReadLock))
337
if have_pywin32 and sys.platform == 'win32':
338
if os.path.supports_unicode_filenames:
339
# for Windows NT/2K/XP/etc
340
win32file_CreateFile = win32file.CreateFileW
343
win32file_CreateFile = win32file.CreateFile
345
class _w32c_FileLock(_OSLock):
347
def _open(self, filename, access, share, cflags, pymode):
348
self.filename = osutils.realpath(filename)
350
self._handle = win32file_CreateFile(filename, access, share,
351
None, win32file.OPEN_ALWAYS,
352
win32file.FILE_ATTRIBUTE_NORMAL, None)
353
except pywintypes.error, e:
354
if e.args[0] == winerror.ERROR_ACCESS_DENIED:
355
raise errors.LockFailed(filename, e)
356
if e.args[0] == winerror.ERROR_SHARING_VIOLATION:
357
raise errors.LockContention(filename, e)
359
fd = win32file._open_osfhandle(self._handle, cflags)
360
self.f = os.fdopen(fd, pymode)
368
class _w32c_ReadLock(_w32c_FileLock):
369
def __init__(self, filename):
370
super(_w32c_ReadLock, self).__init__()
371
self._open(filename, win32file.GENERIC_READ,
372
win32file.FILE_SHARE_READ, os.O_RDONLY, "rb")
374
def temporary_write_lock(self):
375
"""Try to grab a write lock on the file.
377
On platforms that support it, this will upgrade to a write lock
378
without unlocking the file.
379
Otherwise, this will release the read lock, and try to acquire a
382
:return: A token which can be used to switch back to a read lock.
384
# I can't find a way to upgrade a read lock to a write lock without
385
# unlocking first. So here, we do just that.
388
wlock = _w32c_WriteLock(self.filename)
389
except errors.LockError:
390
return False, _w32c_ReadLock(self.filename)
394
class _w32c_WriteLock(_w32c_FileLock):
395
def __init__(self, filename):
396
super(_w32c_WriteLock, self).__init__()
398
win32file.GENERIC_READ | win32file.GENERIC_WRITE, 0,
401
def restore_read_lock(self):
402
"""Restore the original ReadLock."""
403
# For win32 we had to completely let go of the original lock, so we
404
# just unlock and create a new read lock.
406
return _w32c_ReadLock(self.filename)
409
_lock_classes.append(('pywin32', _w32c_WriteLock, _w32c_ReadLock))
412
if have_ctypes_win32:
413
from ctypes.wintypes import DWORD, LPCSTR, LPCWSTR
414
LPSECURITY_ATTRIBUTES = ctypes.c_void_p # used as NULL no need to declare
415
HANDLE = ctypes.c_int # rather than unsigned as in ctypes.wintypes
416
if os.path.supports_unicode_filenames:
417
_function_name = "CreateFileW"
420
_function_name = "CreateFileA"
421
class LPTSTR(LPCSTR):
422
def __new__(cls, obj):
423
return LPCSTR.__new__(cls, obj.encode("mbcs"))
425
# CreateFile <http://msdn.microsoft.com/en-us/library/aa363858.aspx>
426
_CreateFile = ctypes.WINFUNCTYPE(
427
HANDLE, # return value
429
DWORD, # dwDesiredAccess
431
LPSECURITY_ATTRIBUTES, # lpSecurityAttributes
432
DWORD, # dwCreationDisposition
433
DWORD, # dwFlagsAndAttributes
434
HANDLE # hTemplateFile
435
)((_function_name, ctypes.windll.kernel32))
437
INVALID_HANDLE_VALUE = -1
439
GENERIC_READ = 0x80000000
440
GENERIC_WRITE = 0x40000000
443
FILE_ATTRIBUTE_NORMAL = 128
445
ERROR_ACCESS_DENIED = 5
446
ERROR_SHARING_VIOLATION = 32
448
class _ctypes_FileLock(_OSLock):
450
def _open(self, filename, access, share, cflags, pymode):
451
self.filename = osutils.realpath(filename)
452
handle = _CreateFile(filename, access, share, None, OPEN_ALWAYS,
453
FILE_ATTRIBUTE_NORMAL, 0)
454
if handle in (INVALID_HANDLE_VALUE, 0):
455
e = ctypes.WinError()
456
if e.args[0] == ERROR_ACCESS_DENIED:
457
raise errors.LockFailed(filename, e)
458
if e.args[0] == ERROR_SHARING_VIOLATION:
459
raise errors.LockContention(filename, e)
461
fd = msvcrt.open_osfhandle(handle, cflags)
462
self.f = os.fdopen(fd, pymode)
469
class _ctypes_ReadLock(_ctypes_FileLock):
470
def __init__(self, filename):
471
super(_ctypes_ReadLock, self).__init__()
472
self._open(filename, GENERIC_READ, FILE_SHARE_READ, os.O_RDONLY,
475
def temporary_write_lock(self):
476
"""Try to grab a write lock on the file.
478
On platforms that support it, this will upgrade to a write lock
479
without unlocking the file.
480
Otherwise, this will release the read lock, and try to acquire a
483
:return: A token which can be used to switch back to a read lock.
485
# I can't find a way to upgrade a read lock to a write lock without
486
# unlocking first. So here, we do just that.
489
wlock = _ctypes_WriteLock(self.filename)
490
except errors.LockError:
491
return False, _ctypes_ReadLock(self.filename)
494
class _ctypes_WriteLock(_ctypes_FileLock):
495
def __init__(self, filename):
496
super(_ctypes_WriteLock, self).__init__()
497
self._open(filename, GENERIC_READ | GENERIC_WRITE, 0, os.O_RDWR,
500
def restore_read_lock(self):
501
"""Restore the original ReadLock."""
502
# For win32 we had to completely let go of the original lock, so we
503
# just unlock and create a new read lock.
505
return _ctypes_ReadLock(self.filename)
508
_lock_classes.append(('ctypes', _ctypes_WriteLock, _ctypes_ReadLock))
511
if len(_lock_classes) == 0:
512
raise NotImplementedError(
513
"We must have one of fcntl, pywin32, or ctypes available"
514
" to support OS locking."
518
# We default to using the first available lock class.
519
_lock_type, WriteLock, ReadLock = _lock_classes[0]
522
class _RelockDebugMixin(object):
523
"""Mixin support for -Drelock flag.
525
Add this as a base class then call self._note_lock with 'r' or 'w' when
526
acquiring a read- or write-lock. If this object was previously locked (and
527
locked the same way), and -Drelock is set, then this will trace.note a
533
def _note_lock(self, lock_type):
534
if 'relock' in debug.debug_flags and self._prev_lock == lock_type:
539
trace.note('%r was %s locked again', self, type_name)
540
self._prev_lock = lock_type
101
def __init__(self, filename):
103
fcntl.lockf(self._open(filename, 'rb'), fcntl.LOCK_SH)
107
WriteLock = _fcntl_WriteLock
108
ReadLock = _fcntl_ReadLock
112
import win32con, win32file, pywintypes
115
#LOCK_SH = 0 # the default
116
#LOCK_EX = win32con.LOCKFILE_EXCLUSIVE_LOCK
117
#LOCK_NB = win32con.LOCKFILE_FAIL_IMMEDIATELY
119
class _w32c_FileLock(_base_Lock):
120
def _lock(self, filename, openmode, lockmode):
122
self._open(filename, openmode)
123
self.hfile = win32file._get_osfhandle(self.f.fileno())
124
overlapped = pywintypes.OVERLAPPED()
125
win32file.LockFileEx(self.hfile, lockmode, 0, 0x7fff0000, overlapped)
131
overlapped = pywintypes.OVERLAPPED()
132
win32file.UnlockFileEx(self.hfile, 0, 0x7fff0000, overlapped)
140
class _w32c_ReadLock(_w32c_FileLock):
141
def __init__(self, filename):
142
_w32c_FileLock._lock(self, filename, 'rb', 0)
144
class _w32c_WriteLock(_w32c_FileLock):
145
def __init__(self, filename):
146
_w32c_FileLock._lock(self, filename, 'wb',
147
win32con.LOCKFILE_EXCLUSIVE_LOCK)
151
WriteLock = _w32c_WriteLock
152
ReadLock = _w32c_ReadLock
159
# Unfortunately, msvcrt.locking() doesn't distinguish between
160
# read locks and write locks. Also, the way the combinations
161
# work to get non-blocking is not the same, so we
162
# have to write extra special functions here.
165
class _msvc_FileLock(_base_Lock):
175
class _msvc_ReadLock(_msvc_FileLock):
176
def __init__(self, filename):
177
_msvc_lock(self._open(filename, 'rb'), self.LOCK_SH)
180
class _msvc_WriteLock(_msvc_FileLock):
181
def __init__(self, filename):
182
_msvc_lock(self._open(filename, 'wb'), self.LOCK_EX)
186
def _msvc_lock(f, flags):
188
# Unfortunately, msvcrt.LK_RLCK is equivalent to msvcrt.LK_LOCK
189
# according to the comments, LK_RLCK is open the lock for writing.
191
# Unfortunately, msvcrt.locking() also has the side effect that it
192
# will only block for 10 seconds at most, and then it will throw an
193
# exception, this isn't terrible, though.
200
fpos = os.lseek(fn, 0,0)
203
if flags & _msvc_FileLock.LOCK_SH:
204
if flags & _msvc_FileLock.LOCK_NB:
205
lock_mode = msvcrt.LK_NBLCK
207
lock_mode = msvcrt.LK_LOCK
208
elif flags & _msvc_FileLock.LOCK_EX:
209
if flags & _msvc_FileLock.LOCK_NB:
210
lock_mode = msvcrt.LK_NBRLCK
212
lock_mode = msvcrt.LK_RLCK
214
raise ValueError('Invalid lock mode: %r' % flags)
216
msvcrt.locking(fn, lock_mode, -1)
218
os.lseek(fn, fpos, 0)
230
fpos = os.lseek(fn, 0,0)
234
msvcrt.locking(fn, msvcrt.LK_UNLCK, -1)
236
os.lseek(fn, fpos, 0)
242
WriteLock = _msvc_WriteLock
243
ReadLock = _msvc_ReadLock
245
raise NotImplementedError("please write a locking method "
246
"for platform %r" % sys.platform)
added
removed
bzrlib/lock.py
