41
from bzrlib.errors import LockError
42
from bzrlib.osutils import realpath
43
from bzrlib.trace import mutter
46
class _base_Lock(object):
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):
48
137
def _open(self, filename, filemode):
138
self.filename = osutils.realpath(filename)
50
self.f = open(filename, filemode)
140
self.f = open(self.filename, filemode)
52
142
except IOError, e:
143
if e.errno in (errno.EACCES, errno.EPERM):
144
raise errors.LockFailed(self.filename, str(e))
53
145
if e.errno != errno.ENOENT:
56
148
# maybe this is an old branch (before may 2005)
57
mutter("trying to create missing branch lock %r", filename)
59
self.f = open(filename, 'wb+')
149
trace.mutter("trying to create missing lock %r", self.filename)
151
self.f = open(self.filename, 'wb+')
155
"""Clear the self.f attribute cleanly."""
62
160
def __del__(self):
64
162
from warnings import warn
65
163
warn("lock on %r not released" % self.f)
69
167
raise NotImplementedError()
72
############################################################
79
class _fcntl_FileLock(_base_Lock):
175
class _fcntl_FileLock(_OSLock):
83
177
def _unlock(self):
84
178
fcntl.lockf(self.f, fcntl.LOCK_UN)
88
"""Clear the self.f attribute cleanly."""
93
182
class _fcntl_WriteLock(_fcntl_FileLock):
97
186
def __init__(self, filename):
98
# standard IO errors get exposed directly.
99
self._open(filename, 'wb')
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)
194
self._open(self.filename, 'rb+')
195
# reserve a slot for this lock - even if the lockf call fails,
196
# at thisi point unlock() will be called, because self.f is set.
197
# TODO: make this fully threadsafe, if we decide we care.
198
_fcntl_WriteLock._open_locks.add(self.filename)
101
self.filename = realpath(filename)
102
if self.filename in self.open_locks:
104
raise LockError("Lock already held.")
105
# reserve a slot for this lock - even if the lockf call fails,
106
# at thisi point unlock() will be called, because self.f is set.
107
# TODO: make this fully threadsafe, if we decide we care.
108
self.open_locks[self.filename] = self.filename
109
fcntl.lockf(self.f, fcntl.LOCK_EX)
200
# LOCK_NB will cause IOError to be raised if we can't grab a
202
fcntl.lockf(self.f, fcntl.LOCK_EX | fcntl.LOCK_NB)
110
203
except IOError, e:
204
if e.errno in (errno.EAGAIN, errno.EACCES):
205
# We couldn't grab the lock
111
207
# we should be more precise about whats a locking
112
208
# error and whats a random-other error
209
raise errors.LockContention(self.filename, e)
115
211
def unlock(self):
116
del self.open_locks[self.filename]
212
_fcntl_WriteLock._open_locks.remove(self.filename)
120
216
class _fcntl_ReadLock(_fcntl_FileLock):
122
220
def __init__(self, filename):
123
# standard IO errors get exposed directly.
221
super(_fcntl_ReadLock, self).__init__()
222
self.filename = osutils.realpath(filename)
223
_fcntl_ReadLock._open_locks.setdefault(self.filename, 0)
224
_fcntl_ReadLock._open_locks[self.filename] += 1
124
225
self._open(filename, 'rb')
126
fcntl.lockf(self.f, fcntl.LOCK_SH)
227
# LOCK_NB will cause IOError to be raised if we can't grab a
229
fcntl.lockf(self.f, fcntl.LOCK_SH | fcntl.LOCK_NB)
127
230
except IOError, e:
128
231
# we should be more precise about whats a locking
129
232
# error and whats a random-other error
233
raise errors.LockContention(self.filename, e)
132
235
def unlock(self):
236
count = _fcntl_ReadLock._open_locks[self.filename]
238
del _fcntl_ReadLock._open_locks[self.filename]
240
_fcntl_ReadLock._open_locks[self.filename] = count - 1
136
WriteLock = _fcntl_WriteLock
137
ReadLock = _fcntl_ReadLock
142
import win32con, win32file, pywintypes
145
LOCK_SH = 0 # the default
146
LOCK_EX = win32con.LOCKFILE_EXCLUSIVE_LOCK
147
LOCK_NB = win32con.LOCKFILE_FAIL_IMMEDIATELY
149
class _w32c_FileLock(_base_Lock):
150
def _lock(self, filename, openmode, lockmode):
152
self._open(filename, openmode)
153
self.hfile = win32file._get_osfhandle(self.f.fileno())
154
overlapped = pywintypes.OVERLAPPED()
155
win32file.LockFileEx(self.hfile, lockmode, 0, 0x7fff0000, overlapped)
164
overlapped = pywintypes.OVERLAPPED()
165
win32file.UnlockFileEx(self.hfile, 0, 0x7fff0000, overlapped)
172
class _w32c_ReadLock(_w32c_FileLock):
173
def __init__(self, filename):
174
_w32c_FileLock._lock(self, filename, 'rb',
177
class _w32c_WriteLock(_w32c_FileLock):
178
def __init__(self, filename):
179
_w32c_FileLock._lock(self, filename, 'wb',
183
WriteLock = _w32c_WriteLock
184
ReadLock = _w32c_ReadLock
191
# Unfortunately, msvcrt.locking() doesn't distinguish between
192
# read locks and write locks. Also, the way the combinations
193
# work to get non-blocking is not the same, so we
194
# have to write extra special functions here.
197
class _msvc_FileLock(_base_Lock):
207
class _msvc_ReadLock(_msvc_FileLock):
208
def __init__(self, filename):
209
_msvc_lock(self._open(filename, 'rb'), self.LOCK_SH)
212
class _msvc_WriteLock(_msvc_FileLock):
213
def __init__(self, filename):
214
_msvc_lock(self._open(filename, 'wb'), self.LOCK_EX)
217
def _msvc_lock(f, flags):
219
# Unfortunately, msvcrt.LK_RLCK is equivalent to msvcrt.LK_LOCK
220
# according to the comments, LK_RLCK is open the lock for writing.
222
# Unfortunately, msvcrt.locking() also has the side effect that it
223
# will only block for 10 seconds at most, and then it will throw an
224
# exception, this isn't terrible, though.
231
fpos = os.lseek(fn, 0,0)
234
if flags & _msvc_FileLock.LOCK_SH:
235
if flags & _msvc_FileLock.LOCK_NB:
236
lock_mode = msvcrt.LK_NBLCK
238
lock_mode = msvcrt.LK_LOCK
239
elif flags & _msvc_FileLock.LOCK_EX:
240
if flags & _msvc_FileLock.LOCK_NB:
241
lock_mode = msvcrt.LK_NBRLCK
243
lock_mode = msvcrt.LK_RLCK
245
raise ValueError('Invalid lock mode: %r' % flags)
247
msvcrt.locking(fn, lock_mode, -1)
249
os.lseek(fn, fpos, 0)
261
fpos = os.lseek(fn, 0,0)
265
msvcrt.locking(fn, msvcrt.LK_UNLCK, -1)
267
os.lseek(fn, fpos, 0)
272
WriteLock = _msvc_WriteLock
273
ReadLock = _msvc_ReadLock
275
raise NotImplementedError("please write a locking method "
276
"for platform %r" % sys.platform)
243
def temporary_write_lock(self):
244
"""Try to grab a write lock on the file.
246
On platforms that support it, this will upgrade to a write lock
247
without unlocking the file.
248
Otherwise, this will release the read lock, and try to acquire a
251
:return: A token which can be used to switch back to a read lock.
253
if self.filename in _fcntl_WriteLock._open_locks:
254
raise AssertionError('file already locked: %r'
257
wlock = _fcntl_TemporaryWriteLock(self)
258
except errors.LockError:
259
# We didn't unlock, so we can just return 'self'
264
class _fcntl_TemporaryWriteLock(_OSLock):
265
"""A token used when grabbing a temporary_write_lock.
267
Call restore_read_lock() when you are done with the write lock.
270
def __init__(self, read_lock):
271
super(_fcntl_TemporaryWriteLock, self).__init__()
272
self._read_lock = read_lock
273
self.filename = read_lock.filename
275
count = _fcntl_ReadLock._open_locks[self.filename]
277
# Something else also has a read-lock, so we cannot grab a
279
raise errors.LockContention(self.filename)
281
if self.filename in _fcntl_WriteLock._open_locks:
282
raise AssertionError('file already locked: %r'
285
# See if we can open the file for writing. Another process might
286
# have a read lock. We don't use self._open() because we don't want
287
# to create the file if it exists. That would have already been
288
# done by _fcntl_ReadLock
290
new_f = open(self.filename, 'rb+')
292
if e.errno in (errno.EACCES, errno.EPERM):
293
raise errors.LockFailed(self.filename, str(e))
296
# LOCK_NB will cause IOError to be raised if we can't grab a
298
fcntl.lockf(new_f, fcntl.LOCK_EX | fcntl.LOCK_NB)
300
# TODO: Raise a more specific error based on the type of error
301
raise errors.LockContention(self.filename, e)
302
_fcntl_WriteLock._open_locks.add(self.filename)
306
def restore_read_lock(self):
307
"""Restore the original ReadLock."""
308
# For fcntl, since we never released the read lock, just release the
309
# write lock, and return the original lock.
310
fcntl.lockf(self.f, fcntl.LOCK_UN)
312
_fcntl_WriteLock._open_locks.remove(self.filename)
313
# Avoid reference cycles
314
read_lock = self._read_lock
315
self._read_lock = None
319
_lock_classes.append(('fcntl', _fcntl_WriteLock, _fcntl_ReadLock))
322
if have_pywin32 and sys.platform == 'win32':
323
if os.path.supports_unicode_filenames:
324
# for Windows NT/2K/XP/etc
325
win32file_CreateFile = win32file.CreateFileW
328
win32file_CreateFile = win32file.CreateFile
330
class _w32c_FileLock(_OSLock):
332
def _open(self, filename, access, share, cflags, pymode):
333
self.filename = osutils.realpath(filename)
335
self._handle = win32file_CreateFile(filename, access, share,
336
None, win32file.OPEN_ALWAYS,
337
win32file.FILE_ATTRIBUTE_NORMAL, None)
338
except pywintypes.error, e:
339
if e.args[0] == winerror.ERROR_ACCESS_DENIED:
340
raise errors.LockFailed(filename, e)
341
if e.args[0] == winerror.ERROR_SHARING_VIOLATION:
342
raise errors.LockContention(filename, e)
344
fd = win32file._open_osfhandle(self._handle, cflags)
345
self.f = os.fdopen(fd, pymode)
353
class _w32c_ReadLock(_w32c_FileLock):
354
def __init__(self, filename):
355
super(_w32c_ReadLock, self).__init__()
356
self._open(filename, win32file.GENERIC_READ,
357
win32file.FILE_SHARE_READ, os.O_RDONLY, "rb")
359
def temporary_write_lock(self):
360
"""Try to grab a write lock on the file.
362
On platforms that support it, this will upgrade to a write lock
363
without unlocking the file.
364
Otherwise, this will release the read lock, and try to acquire a
367
:return: A token which can be used to switch back to a read lock.
369
# I can't find a way to upgrade a read lock to a write lock without
370
# unlocking first. So here, we do just that.
373
wlock = _w32c_WriteLock(self.filename)
374
except errors.LockError:
375
return False, _w32c_ReadLock(self.filename)
379
class _w32c_WriteLock(_w32c_FileLock):
380
def __init__(self, filename):
381
super(_w32c_WriteLock, self).__init__()
383
win32file.GENERIC_READ | win32file.GENERIC_WRITE, 0,
386
def restore_read_lock(self):
387
"""Restore the original ReadLock."""
388
# For win32 we had to completely let go of the original lock, so we
389
# just unlock and create a new read lock.
391
return _w32c_ReadLock(self.filename)
394
_lock_classes.append(('pywin32', _w32c_WriteLock, _w32c_ReadLock))
397
if have_ctypes_win32:
398
from ctypes.wintypes import DWORD, LPCSTR, LPCWSTR
399
LPSECURITY_ATTRIBUTES = ctypes.c_void_p # used as NULL no need to declare
400
HANDLE = ctypes.c_int # rather than unsigned as in ctypes.wintypes
401
if os.path.supports_unicode_filenames:
402
_function_name = "CreateFileW"
405
_function_name = "CreateFileA"
406
class LPTSTR(LPCSTR):
407
def __new__(cls, obj):
408
return LPCSTR.__new__(cls, obj.encode("mbcs"))
410
# CreateFile <http://msdn.microsoft.com/en-us/library/aa363858.aspx>
411
_CreateFile = ctypes.WINFUNCTYPE(
412
HANDLE, # return value
414
DWORD, # dwDesiredAccess
416
LPSECURITY_ATTRIBUTES, # lpSecurityAttributes
417
DWORD, # dwCreationDisposition
418
DWORD, # dwFlagsAndAttributes
419
HANDLE # hTemplateFile
420
)((_function_name, ctypes.windll.kernel32))
422
INVALID_HANDLE_VALUE = -1
424
GENERIC_READ = 0x80000000
425
GENERIC_WRITE = 0x40000000
428
FILE_ATTRIBUTE_NORMAL = 128
430
ERROR_ACCESS_DENIED = 5
431
ERROR_SHARING_VIOLATION = 32
433
class _ctypes_FileLock(_OSLock):
435
def _open(self, filename, access, share, cflags, pymode):
436
self.filename = osutils.realpath(filename)
437
handle = _CreateFile(filename, access, share, None, OPEN_ALWAYS,
438
FILE_ATTRIBUTE_NORMAL, 0)
439
if handle in (INVALID_HANDLE_VALUE, 0):
440
e = ctypes.WinError()
441
if e.args[0] == ERROR_ACCESS_DENIED:
442
raise errors.LockFailed(filename, e)
443
if e.args[0] == ERROR_SHARING_VIOLATION:
444
raise errors.LockContention(filename, e)
446
fd = msvcrt.open_osfhandle(handle, cflags)
447
self.f = os.fdopen(fd, pymode)
454
class _ctypes_ReadLock(_ctypes_FileLock):
455
def __init__(self, filename):
456
super(_ctypes_ReadLock, self).__init__()
457
self._open(filename, GENERIC_READ, FILE_SHARE_READ, os.O_RDONLY,
460
def temporary_write_lock(self):
461
"""Try to grab a write lock on the file.
463
On platforms that support it, this will upgrade to a write lock
464
without unlocking the file.
465
Otherwise, this will release the read lock, and try to acquire a
468
:return: A token which can be used to switch back to a read lock.
470
# I can't find a way to upgrade a read lock to a write lock without
471
# unlocking first. So here, we do just that.
474
wlock = _ctypes_WriteLock(self.filename)
475
except errors.LockError:
476
return False, _ctypes_ReadLock(self.filename)
479
class _ctypes_WriteLock(_ctypes_FileLock):
480
def __init__(self, filename):
481
super(_ctypes_WriteLock, self).__init__()
482
self._open(filename, GENERIC_READ | GENERIC_WRITE, 0, os.O_RDWR,
485
def restore_read_lock(self):
486
"""Restore the original ReadLock."""
487
# For win32 we had to completely let go of the original lock, so we
488
# just unlock and create a new read lock.
490
return _ctypes_ReadLock(self.filename)
493
_lock_classes.append(('ctypes', _ctypes_WriteLock, _ctypes_ReadLock))
496
if len(_lock_classes) == 0:
497
raise NotImplementedError(
498
"We must have one of fcntl, pywin32, or ctypes available"
499
" to support OS locking."
503
# We default to using the first available lock class.
504
_lock_type, WriteLock, ReadLock = _lock_classes[0]
added
removed
bzrlib/lock.py
