1
# Copyright (C) 2005 Canonical Ltd
1
# Copyright (C) 2005, 2006, 2007, 2008, 2009 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20
This only does local locking using OS locks for now.
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.
22
24
This module causes two methods, lock() and unlock() to be defined in
23
25
any way that works on the current platform.
25
27
It is not specified whether these locks are reentrant (i.e. can be
26
28
taken repeatedly by a single process) or whether they exclude
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.
29
different threads in a single process. That reentrancy is provided by
32
32
This defines two classes: ReadLock and WriteLock, which can be
33
33
implemented in different ways on different platforms. Both have an
41
from bzrlib.trace import mutter, note, warning
42
from bzrlib.errors import LockError
44
class _base_Lock(object):
45
from bzrlib.hooks import HookPoint, Hooks
48
class LockHooks(Hooks):
52
self.create_hook(HookPoint('lock_acquired',
53
"Called with a bzrlib.lock.LockResult when a physical lock is "
54
"acquired.", (1, 8), None))
55
self.create_hook(HookPoint('lock_released',
56
"Called with a bzrlib.lock.LockResult when a physical lock is "
57
"released.", (1, 8), None))
61
"""Base class for locks.
63
:cvar hooks: Hook dictionary for operations on locks.
69
class LockResult(object):
70
"""Result of an operation on a lock; passed to a hook"""
72
def __init__(self, lock_url, details=None):
73
"""Create a lock result for lock with optional details about the lock."""
74
self.lock_url = lock_url
75
self.details = details
77
def __eq__(self, other):
78
return self.lock_url == other.lock_url and self.details == other.details
88
have_ctypes_win32 = False
89
if sys.platform == 'win32':
92
import win32con, win32file, pywintypes, winerror
99
have_ctypes_win32 = True
104
class _OSLock(object):
45
110
def _open(self, filename, filemode):
111
self.filename = osutils.realpath(filename)
48
self.f = open(filename, filemode)
113
self.f = open(self.filename, filemode)
50
115
except IOError, e:
116
if e.errno in (errno.EACCES, errno.EPERM):
117
raise errors.LockFailed(self.filename, str(e))
51
118
if e.errno != errno.ENOENT:
54
121
# maybe this is an old branch (before may 2005)
55
mutter("trying to create missing branch lock %r" % filename)
57
self.f = open(filename, 'wb')
122
trace.mutter("trying to create missing lock %r", self.filename)
124
self.f = open(self.filename, 'wb+')
128
"""Clear the self.f attribute cleanly."""
61
133
def __del__(self):
63
135
from warnings import warn
64
136
warn("lock on %r not released" % self.f)
69
140
raise NotImplementedError()
76
############################################################
83
class _fcntl_FileLock(_base_Lock):
87
fcntl.flock(self.f, fcntl.LOCK_UN)
147
LOCK_SH = fcntl.LOCK_SH
148
LOCK_NB = fcntl.LOCK_NB
149
lock_EX = fcntl.LOCK_EX
152
class _fcntl_FileLock(_OSLock):
155
fcntl.lockf(self.f, fcntl.LOCK_UN)
92
159
class _fcntl_WriteLock(_fcntl_FileLock):
93
163
def __init__(self, filename):
164
super(_fcntl_WriteLock, self).__init__()
165
# Check we can grab a lock before we actually open the file.
166
self.filename = osutils.realpath(filename)
167
if self.filename in _fcntl_WriteLock._open_locks:
169
raise errors.LockContention(self.filename)
171
self._open(self.filename, 'rb+')
172
# reserve a slot for this lock - even if the lockf call fails,
173
# at thisi point unlock() will be called, because self.f is set.
174
# TODO: make this fully threadsafe, if we decide we care.
175
_fcntl_WriteLock._open_locks.add(self.filename)
95
fcntl.flock(self._open(filename, 'wb'), fcntl.LOCK_EX)
177
# LOCK_NB will cause IOError to be raised if we can't grab a
179
fcntl.lockf(self.f, fcntl.LOCK_EX | fcntl.LOCK_NB)
181
if e.errno in (errno.EAGAIN, errno.EACCES):
182
# We couldn't grab the lock
184
# we should be more precise about whats a locking
185
# error and whats a random-other error
186
raise errors.LockContention(self.filename, e)
189
_fcntl_WriteLock._open_locks.remove(self.filename)
100
193
class _fcntl_ReadLock(_fcntl_FileLock):
101
def __init__(self, filename):
103
fcntl.flock(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):
173
class _msvc_ReadLock(_msvc_FileLock):
174
def __init__(self, filename):
175
_msvc_lock(self._open(filename, 'rb'), self.LOCK_SH)
178
class _msvc_WriteLock(_msvc_FileLock):
179
def __init__(self, filename):
180
_msvc_lock(self._open(filename, 'wb'), self.LOCK_EX)
184
def _msvc_lock(f, flags):
186
# Unfortunately, msvcrt.LK_RLCK is equivalent to msvcrt.LK_LOCK
187
# according to the comments, LK_RLCK is open the lock for writing.
189
# Unfortunately, msvcrt.locking() also has the side effect that it
190
# will only block for 10 seconds at most, and then it will throw an
191
# exception, this isn't terrible, though.
198
fpos = os.lseek(fn, 0,0)
201
if flags & _msvc_FileLock.LOCK_SH:
202
if flags & _msvc_FileLock.LOCK_NB:
203
lock_mode = msvcrt.LK_NBLCK
205
lock_mode = msvcrt.LK_LOCK
206
elif flags & _msvc_FileLock.LOCK_EX:
207
if flags & _msvc_FileLock.LOCK_NB:
208
lock_mode = msvcrt.LK_NBRLCK
210
lock_mode = msvcrt.LK_RLCK
212
raise ValueError('Invalid lock mode: %r' % flags)
214
msvcrt.locking(fn, lock_mode, -1)
216
os.lseek(fn, fpos, 0)
228
fpos = os.lseek(fn, 0,0)
232
msvcrt.locking(fn, msvcrt.LK_UNLCK, -1)
234
os.lseek(fn, fpos, 0)
240
WriteLock = _msvc_WriteLock
241
ReadLock = _msvc_ReadLock
243
raise NotImplementedError("please write a locking method "
244
"for platform %r" % sys.platform)
197
def __init__(self, filename):
198
super(_fcntl_ReadLock, self).__init__()
199
self.filename = osutils.realpath(filename)
200
_fcntl_ReadLock._open_locks.setdefault(self.filename, 0)
201
_fcntl_ReadLock._open_locks[self.filename] += 1
202
self._open(filename, 'rb')
204
# LOCK_NB will cause IOError to be raised if we can't grab a
206
fcntl.lockf(self.f, fcntl.LOCK_SH | fcntl.LOCK_NB)
208
# we should be more precise about whats a locking
209
# error and whats a random-other error
210
raise errors.LockContention(self.filename, e)
213
count = _fcntl_ReadLock._open_locks[self.filename]
215
del _fcntl_ReadLock._open_locks[self.filename]
217
_fcntl_ReadLock._open_locks[self.filename] = count - 1
220
def temporary_write_lock(self):
221
"""Try to grab a write lock on the file.
223
On platforms that support it, this will upgrade to a write lock
224
without unlocking the file.
225
Otherwise, this will release the read lock, and try to acquire a
228
:return: A token which can be used to switch back to a read lock.
230
if self.filename in _fcntl_WriteLock._open_locks:
231
raise AssertionError('file already locked: %r'
234
wlock = _fcntl_TemporaryWriteLock(self)
235
except errors.LockError:
236
# We didn't unlock, so we can just return 'self'
241
class _fcntl_TemporaryWriteLock(_OSLock):
242
"""A token used when grabbing a temporary_write_lock.
244
Call restore_read_lock() when you are done with the write lock.
247
def __init__(self, read_lock):
248
super(_fcntl_TemporaryWriteLock, self).__init__()
249
self._read_lock = read_lock
250
self.filename = read_lock.filename
252
count = _fcntl_ReadLock._open_locks[self.filename]
254
# Something else also has a read-lock, so we cannot grab a
256
raise errors.LockContention(self.filename)
258
if self.filename in _fcntl_WriteLock._open_locks:
259
raise AssertionError('file already locked: %r'
262
# See if we can open the file for writing. Another process might
263
# have a read lock. We don't use self._open() because we don't want
264
# to create the file if it exists. That would have already been
265
# done by _fcntl_ReadLock
267
new_f = open(self.filename, 'rb+')
269
if e.errno in (errno.EACCES, errno.EPERM):
270
raise errors.LockFailed(self.filename, str(e))
273
# LOCK_NB will cause IOError to be raised if we can't grab a
275
fcntl.lockf(new_f, fcntl.LOCK_EX | fcntl.LOCK_NB)
277
# TODO: Raise a more specific error based on the type of error
278
raise errors.LockContention(self.filename, e)
279
_fcntl_WriteLock._open_locks.add(self.filename)
283
def restore_read_lock(self):
284
"""Restore the original ReadLock."""
285
# For fcntl, since we never released the read lock, just release the
286
# write lock, and return the original lock.
287
fcntl.lockf(self.f, fcntl.LOCK_UN)
289
_fcntl_WriteLock._open_locks.remove(self.filename)
290
# Avoid reference cycles
291
read_lock = self._read_lock
292
self._read_lock = None
296
_lock_classes.append(('fcntl', _fcntl_WriteLock, _fcntl_ReadLock))
299
if have_pywin32 and sys.platform == 'win32':
300
LOCK_SH = 0 # the default
301
LOCK_EX = win32con.LOCKFILE_EXCLUSIVE_LOCK
302
LOCK_NB = win32con.LOCKFILE_FAIL_IMMEDIATELY
305
class _w32c_FileLock(_OSLock):
307
def _lock(self, filename, openmode, lockmode):
308
self._open(filename, openmode)
310
self.hfile = msvcrt.get_osfhandle(self.f.fileno())
311
overlapped = pywintypes.OVERLAPPED()
313
win32file.LockFileEx(self.hfile, lockmode, 0, 0x7fff0000,
315
except pywintypes.error, e:
317
if e.args[0] in (winerror.ERROR_LOCK_VIOLATION,):
318
raise errors.LockContention(filename)
319
## import pdb; pdb.set_trace()
323
raise errors.LockContention(filename, e)
326
overlapped = pywintypes.OVERLAPPED()
328
win32file.UnlockFileEx(self.hfile, 0, 0x7fff0000, overlapped)
331
raise errors.LockContention(self.filename, e)
334
class _w32c_ReadLock(_w32c_FileLock):
335
def __init__(self, filename):
336
super(_w32c_ReadLock, self).__init__()
337
self._lock(filename, 'rb', LOCK_SH + LOCK_NB)
339
def temporary_write_lock(self):
340
"""Try to grab a write lock on the file.
342
On platforms that support it, this will upgrade to a write lock
343
without unlocking the file.
344
Otherwise, this will release the read lock, and try to acquire a
347
:return: A token which can be used to switch back to a read lock.
349
# I can't find a way to upgrade a read lock to a write lock without
350
# unlocking first. So here, we do just that.
353
wlock = _w32c_WriteLock(self.filename)
354
except errors.LockError:
355
return False, _w32c_ReadLock(self.filename)
359
class _w32c_WriteLock(_w32c_FileLock):
360
def __init__(self, filename):
361
super(_w32c_WriteLock, self).__init__()
362
self._lock(filename, 'rb+', LOCK_EX + LOCK_NB)
364
def restore_read_lock(self):
365
"""Restore the original ReadLock."""
366
# For win32 we had to completely let go of the original lock, so we
367
# just unlock and create a new read lock.
369
return _w32c_ReadLock(self.filename)
372
_lock_classes.append(('pywin32', _w32c_WriteLock, _w32c_ReadLock))
375
if have_ctypes_win32:
376
# These constants were copied from the win32con.py module.
377
LOCKFILE_FAIL_IMMEDIATELY = 1
378
LOCKFILE_EXCLUSIVE_LOCK = 2
379
# Constant taken from winerror.py module
380
ERROR_LOCK_VIOLATION = 33
383
LOCK_EX = LOCKFILE_EXCLUSIVE_LOCK
384
LOCK_NB = LOCKFILE_FAIL_IMMEDIATELY
385
_LockFileEx = ctypes.windll.kernel32.LockFileEx
386
_UnlockFileEx = ctypes.windll.kernel32.UnlockFileEx
387
_GetLastError = ctypes.windll.kernel32.GetLastError
389
### Define the OVERLAPPED structure.
390
# http://msdn2.microsoft.com/en-us/library/ms684342.aspx
391
# typedef struct _OVERLAPPED {
392
# ULONG_PTR Internal;
393
# ULONG_PTR InternalHigh;
404
class _inner_struct(ctypes.Structure):
405
_fields_ = [('Offset', ctypes.c_uint), # DWORD
406
('OffsetHigh', ctypes.c_uint), # DWORD
409
class _inner_union(ctypes.Union):
410
_fields_ = [('anon_struct', _inner_struct), # struct
411
('Pointer', ctypes.c_void_p), # PVOID
414
class OVERLAPPED(ctypes.Structure):
415
_fields_ = [('Internal', ctypes.c_void_p), # ULONG_PTR
416
('InternalHigh', ctypes.c_void_p), # ULONG_PTR
417
('_inner_union', _inner_union),
418
('hEvent', ctypes.c_void_p), # HANDLE
421
class _ctypes_FileLock(_OSLock):
423
def _lock(self, filename, openmode, lockmode):
424
self._open(filename, openmode)
426
self.hfile = msvcrt.get_osfhandle(self.f.fileno())
427
overlapped = OVERLAPPED()
428
result = _LockFileEx(self.hfile, # HANDLE hFile
429
lockmode, # DWORD dwFlags
430
0, # DWORD dwReserved
431
0x7fffffff, # DWORD nNumberOfBytesToLockLow
432
0x00000000, # DWORD nNumberOfBytesToLockHigh
433
ctypes.byref(overlapped), # lpOverlapped
437
last_err = _GetLastError()
438
if last_err in (ERROR_LOCK_VIOLATION,):
439
raise errors.LockContention(filename)
440
raise errors.LockContention(filename,
441
'Unknown locking error: %s' % (last_err,))
444
overlapped = OVERLAPPED()
445
result = _UnlockFileEx(self.hfile, # HANDLE hFile
446
0, # DWORD dwReserved
447
0x7fffffff, # DWORD nNumberOfBytesToLockLow
448
0x00000000, # DWORD nNumberOfBytesToLockHigh
449
ctypes.byref(overlapped), # lpOverlapped
454
last_err = _GetLastError()
455
raise errors.LockContention(self.filename,
456
'Unknown unlocking error: %s' % (last_err,))
459
class _ctypes_ReadLock(_ctypes_FileLock):
460
def __init__(self, filename):
461
super(_ctypes_ReadLock, self).__init__()
462
self._lock(filename, 'rb', LOCK_SH + LOCK_NB)
464
def temporary_write_lock(self):
465
"""Try to grab a write lock on the file.
467
On platforms that support it, this will upgrade to a write lock
468
without unlocking the file.
469
Otherwise, this will release the read lock, and try to acquire a
472
:return: A token which can be used to switch back to a read lock.
474
# I can't find a way to upgrade a read lock to a write lock without
475
# unlocking first. So here, we do just that.
478
wlock = _ctypes_WriteLock(self.filename)
479
except errors.LockError:
480
return False, _ctypes_ReadLock(self.filename)
483
class _ctypes_WriteLock(_ctypes_FileLock):
484
def __init__(self, filename):
485
super(_ctypes_WriteLock, self).__init__()
486
self._lock(filename, 'rb+', LOCK_EX + LOCK_NB)
488
def restore_read_lock(self):
489
"""Restore the original ReadLock."""
490
# For win32 we had to completely let go of the original lock, so we
491
# just unlock and create a new read lock.
493
return _ctypes_ReadLock(self.filename)
496
_lock_classes.append(('ctypes', _ctypes_WriteLock, _ctypes_ReadLock))
499
if len(_lock_classes) == 0:
500
raise NotImplementedError(
501
"We must have one of fcntl, pywin32, or ctypes available"
502
" to support OS locking."
506
# We default to using the first available lock class.
507
_lock_type, WriteLock, ReadLock = _lock_classes[0]
added
removed
bzrlib/lock.py
