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  • Committer: Ian Clatworthy
  • Date: 2007-12-11 02:07:30 UTC
  • mto: (3119.1.1 ianc-integration)
  • mto: This revision was merged to the branch mainline in revision 3120.
  • Revision ID: ian.clatworthy@internode.on.net-20071211020730-sdj4kj794dw0628e
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bzrlib/lock.py
1
 
# Copyright (C) 2005-2010 Canonical Ltd
 
1
# Copyright (C) 2005, 2006, 2007 Canonical Ltd
2
2
#
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
12
12
#
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
 
15
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
16
16
 
17
17
 
18
18
"""Locking using OS file locks or file existence.
35
35
"""
36
36
 
37
37
import errno
38
 
import os
39
38
import sys
40
 
import warnings
41
39
 
42
40
from bzrlib import (
43
 
    debug,
44
41
    errors,
45
42
    osutils,
46
43
    trace,
47
44
    )
48
 
from bzrlib.hooks import HookPoint, Hooks
49
 
 
50
 
 
51
 
class LockHooks(Hooks):
52
 
 
53
 
    def __init__(self):
54
 
        Hooks.__init__(self)
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))
64
 
 
65
 
 
66
 
class Lock(object):
67
 
    """Base class for locks.
68
 
 
69
 
    :cvar hooks: Hook dictionary for operations on locks.
70
 
    """
71
 
 
72
 
    hooks = LockHooks()
73
 
 
74
 
 
75
 
class LockResult(object):
76
 
    """Result of an operation on a lock; passed to a hook"""
77
 
 
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
82
 
 
83
 
    def __eq__(self, other):
84
 
        return self.lock_url == other.lock_url and self.details == other.details
85
 
 
86
 
    def __repr__(self):
87
 
        return '%s(%s, %s)' % (self.__class__.__name__,
88
 
                             self.lock_url, self.details)
89
 
 
90
 
 
91
 
def cant_unlock_not_held(locked_object):
92
 
    """An attempt to unlock failed because the object was not locked.
93
 
 
94
 
    This provides a policy point from which we can generate either a warning 
95
 
    or an exception.
96
 
    """
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
100
 
    # raise LockNotHeld.
101
 
    if 'unlock' in debug.debug_flags:
102
 
        warnings.warn("%r is already unlocked" % (locked_object,),
103
 
            stacklevel=3)
104
 
    else:
105
 
        raise errors.LockNotHeld(locked_object)
106
 
 
107
 
 
108
 
try:
109
 
    import fcntl
110
 
    have_fcntl = True
111
 
except ImportError:
112
 
    have_fcntl = False
113
 
 
114
 
have_pywin32 = False
115
 
have_ctypes_win32 = False
116
 
if sys.platform == 'win32':
117
 
    import msvcrt
118
 
    try:
119
 
        import win32file, pywintypes, winerror
120
 
        have_pywin32 = True
121
 
    except ImportError:
122
 
        pass
123
 
 
124
 
    try:
125
 
        import ctypes
126
 
        have_ctypes_win32 = True
127
 
    except ImportError:
128
 
        pass
129
45
 
130
46
 
131
47
class _OSLock(object):
167
83
        raise NotImplementedError()
168
84
 
169
85
 
 
86
try:
 
87
    import fcntl
 
88
    have_fcntl = True
 
89
except ImportError:
 
90
    have_fcntl = False
 
91
try:
 
92
    import win32con, win32file, pywintypes, winerror, msvcrt
 
93
    have_pywin32 = True
 
94
except ImportError:
 
95
    have_pywin32 = False
 
96
try:
 
97
    import ctypes, msvcrt
 
98
    have_ctypes = True
 
99
except ImportError:
 
100
    have_ctypes = False
 
101
 
 
102
 
170
103
_lock_classes = []
171
104
 
172
105
 
173
106
if have_fcntl:
 
107
    LOCK_SH = fcntl.LOCK_SH
 
108
    LOCK_NB = fcntl.LOCK_NB
 
109
    lock_EX = fcntl.LOCK_EX
 
110
 
174
111
 
175
112
    class _fcntl_FileLock(_OSLock):
176
113
 
190
127
            if self.filename in _fcntl_WriteLock._open_locks:
191
128
                self._clear_f()
192
129
                raise errors.LockContention(self.filename)
193
 
            if self.filename in _fcntl_ReadLock._open_locks:
194
 
                if 'strict_locks' in debug.debug_flags:
195
 
                    self._clear_f()
196
 
                    raise errors.LockContention(self.filename)
197
 
                else:
198
 
                    trace.mutter('Write lock taken w/ an open read lock on: %s'
199
 
                                 % (self.filename,))
200
130
 
201
131
            self._open(self.filename, 'rb+')
202
132
            # 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.
 
133
            # at thisi point unlock() will be called, because self.f is set.
204
134
            # TODO: make this fully threadsafe, if we decide we care.
205
135
            _fcntl_WriteLock._open_locks.add(self.filename)
206
136
            try:
213
143
                    self.unlock()
214
144
                # we should be more precise about whats a locking
215
145
                # error and whats a random-other error
216
 
                raise errors.LockContention(self.filename, e)
 
146
                raise errors.LockContention(e)
217
147
 
218
148
        def unlock(self):
219
149
            _fcntl_WriteLock._open_locks.remove(self.filename)
227
157
        def __init__(self, filename):
228
158
            super(_fcntl_ReadLock, self).__init__()
229
159
            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
233
 
                    # _clear_f
234
 
                    raise errors.LockContention(self.filename)
235
 
                else:
236
 
                    trace.mutter('Read lock taken w/ an open write lock on: %s'
237
 
                                 % (self.filename,))
238
160
            _fcntl_ReadLock._open_locks.setdefault(self.filename, 0)
239
161
            _fcntl_ReadLock._open_locks[self.filename] += 1
240
162
            self._open(filename, 'rb')
245
167
            except IOError, e:
246
168
                # we should be more precise about whats a locking
247
169
                # error and whats a random-other error
248
 
                raise errors.LockContention(self.filename, e)
 
170
                raise errors.LockContention(e)
249
171
 
250
172
        def unlock(self):
251
173
            count = _fcntl_ReadLock._open_locks[self.filename]
265
187
 
266
188
            :return: A token which can be used to switch back to a read lock.
267
189
            """
268
 
            if self.filename in _fcntl_WriteLock._open_locks:
269
 
                raise AssertionError('file already locked: %r'
270
 
                    % (self.filename,))
 
190
            assert self.filename not in _fcntl_WriteLock._open_locks
271
191
            try:
272
192
                wlock = _fcntl_TemporaryWriteLock(self)
273
193
            except errors.LockError:
293
213
                # write lock.
294
214
                raise errors.LockContention(self.filename)
295
215
 
296
 
            if self.filename in _fcntl_WriteLock._open_locks:
297
 
                raise AssertionError('file already locked: %r'
298
 
                    % (self.filename,))
 
216
            assert self.filename not in _fcntl_WriteLock._open_locks
299
217
 
300
218
            # See if we can open the file for writing. Another process might
301
219
            # have a read lock. We don't use self._open() because we don't want
313
231
                fcntl.lockf(new_f, fcntl.LOCK_EX | fcntl.LOCK_NB)
314
232
            except IOError, e:
315
233
                # TODO: Raise a more specific error based on the type of error
316
 
                raise errors.LockContention(self.filename, e)
 
234
                raise errors.LockContention(e)
317
235
            _fcntl_WriteLock._open_locks.add(self.filename)
318
236
 
319
237
            self.f = new_f
335
253
 
336
254
 
337
255
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
341
 
    else:
342
 
        # for Windows 98
343
 
        win32file_CreateFile = win32file.CreateFile
 
256
    LOCK_SH = 0 # the default
 
257
    LOCK_EX = win32con.LOCKFILE_EXCLUSIVE_LOCK
 
258
    LOCK_NB = win32con.LOCKFILE_FAIL_IMMEDIATELY
 
259
 
344
260
 
345
261
    class _w32c_FileLock(_OSLock):
346
262
 
347
 
        def _open(self, filename, access, share, cflags, pymode):
348
 
            self.filename = osutils.realpath(filename)
 
263
        def _lock(self, filename, openmode, lockmode):
 
264
            self._open(filename, openmode)
 
265
 
 
266
            self.hfile = msvcrt.get_osfhandle(self.f.fileno())
 
267
            overlapped = pywintypes.OVERLAPPED()
349
268
            try:
350
 
                self._handle = win32file_CreateFile(filename, access, share,
351
 
                    None, win32file.OPEN_ALWAYS,
352
 
                    win32file.FILE_ATTRIBUTE_NORMAL, None)
 
269
                win32file.LockFileEx(self.hfile, lockmode, 0, 0x7fff0000,
 
270
                                     overlapped)
353
271
            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)
 
272
                self._clear_f()
 
273
                if e.args[0] in (winerror.ERROR_LOCK_VIOLATION,):
 
274
                    raise errors.LockContention(filename)
 
275
                ## import pdb; pdb.set_trace()
358
276
                raise
359
 
            fd = win32file._open_osfhandle(self._handle, cflags)
360
 
            self.f = os.fdopen(fd, pymode)
361
 
            return self.f
 
277
            except Exception, e:
 
278
                self._clear_f()
 
279
                raise errors.LockContention(e)
362
280
 
363
281
        def unlock(self):
364
 
            self._clear_f()
365
 
            self._handle = None
 
282
            overlapped = pywintypes.OVERLAPPED()
 
283
            try:
 
284
                win32file.UnlockFileEx(self.hfile, 0, 0x7fff0000, overlapped)
 
285
                self._clear_f()
 
286
            except Exception, e:
 
287
                raise errors.LockContention(e)
366
288
 
367
289
 
368
290
    class _w32c_ReadLock(_w32c_FileLock):
369
291
        def __init__(self, filename):
370
292
            super(_w32c_ReadLock, self).__init__()
371
 
            self._open(filename, win32file.GENERIC_READ,
372
 
                win32file.FILE_SHARE_READ, os.O_RDONLY, "rb")
 
293
            self._lock(filename, 'rb', LOCK_SH + LOCK_NB)
373
294
 
374
295
        def temporary_write_lock(self):
375
296
            """Try to grab a write lock on the file.
394
315
    class _w32c_WriteLock(_w32c_FileLock):
395
316
        def __init__(self, filename):
396
317
            super(_w32c_WriteLock, self).__init__()
397
 
            self._open(filename,
398
 
                win32file.GENERIC_READ | win32file.GENERIC_WRITE, 0,
399
 
                os.O_RDWR, "rb+")
 
318
            self._lock(filename, 'rb+', LOCK_EX + LOCK_NB)
400
319
 
401
320
        def restore_read_lock(self):
402
321
            """Restore the original ReadLock."""
409
328
    _lock_classes.append(('pywin32', _w32c_WriteLock, _w32c_ReadLock))
410
329
 
411
330
 
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"
418
 
        LPTSTR = LPCWSTR
419
 
    else:
420
 
        _function_name = "CreateFileA"
421
 
        class LPTSTR(LPCSTR):
422
 
            def __new__(cls, obj):
423
 
                return LPCSTR.__new__(cls, obj.encode("mbcs"))
424
 
 
425
 
    # CreateFile <http://msdn.microsoft.com/en-us/library/aa363858.aspx>
426
 
    _CreateFile = ctypes.WINFUNCTYPE(
427
 
            HANDLE,                # return value
428
 
            LPTSTR,                # lpFileName
429
 
            DWORD,                 # dwDesiredAccess
430
 
            DWORD,                 # dwShareMode
431
 
            LPSECURITY_ATTRIBUTES, # lpSecurityAttributes
432
 
            DWORD,                 # dwCreationDisposition
433
 
            DWORD,                 # dwFlagsAndAttributes
434
 
            HANDLE                 # hTemplateFile
435
 
        )((_function_name, ctypes.windll.kernel32))
436
 
 
437
 
    INVALID_HANDLE_VALUE = -1
438
 
 
439
 
    GENERIC_READ = 0x80000000
440
 
    GENERIC_WRITE = 0x40000000
441
 
    FILE_SHARE_READ = 1
442
 
    OPEN_ALWAYS = 4
443
 
    FILE_ATTRIBUTE_NORMAL = 128
444
 
 
445
 
    ERROR_ACCESS_DENIED = 5
446
 
    ERROR_SHARING_VIOLATION = 32
 
331
if have_ctypes and sys.platform == 'win32':
 
332
    # These constants were copied from the win32con.py module.
 
333
    LOCKFILE_FAIL_IMMEDIATELY = 1
 
334
    LOCKFILE_EXCLUSIVE_LOCK = 2
 
335
    # Constant taken from winerror.py module
 
336
    ERROR_LOCK_VIOLATION = 33
 
337
 
 
338
    LOCK_SH = 0
 
339
    LOCK_EX = LOCKFILE_EXCLUSIVE_LOCK
 
340
    LOCK_NB = LOCKFILE_FAIL_IMMEDIATELY
 
341
    _LockFileEx = ctypes.windll.kernel32.LockFileEx
 
342
    _UnlockFileEx = ctypes.windll.kernel32.UnlockFileEx
 
343
    _GetLastError = ctypes.windll.kernel32.GetLastError
 
344
 
 
345
    ### Define the OVERLAPPED structure.
 
346
    #   http://msdn2.microsoft.com/en-us/library/ms684342.aspx
 
347
    # typedef struct _OVERLAPPED {
 
348
    #   ULONG_PTR Internal;
 
349
    #   ULONG_PTR InternalHigh;
 
350
    #   union {
 
351
    #     struct {
 
352
    #       DWORD Offset;
 
353
    #       DWORD OffsetHigh;
 
354
    #     };
 
355
    #     PVOID Pointer;
 
356
    #   };
 
357
    #   HANDLE hEvent;
 
358
    # } OVERLAPPED,
 
359
 
 
360
    class _inner_struct(ctypes.Structure):
 
361
        _fields_ = [('Offset', ctypes.c_uint), # DWORD
 
362
                    ('OffsetHigh', ctypes.c_uint), # DWORD
 
363
                   ]
 
364
 
 
365
    class _inner_union(ctypes.Union):
 
366
        _fields_  = [('anon_struct', _inner_struct), # struct
 
367
                     ('Pointer', ctypes.c_void_p), # PVOID
 
368
                    ]
 
369
 
 
370
    class OVERLAPPED(ctypes.Structure):
 
371
        _fields_ = [('Internal', ctypes.c_void_p), # ULONG_PTR
 
372
                    ('InternalHigh', ctypes.c_void_p), # ULONG_PTR
 
373
                    ('_inner_union', _inner_union),
 
374
                    ('hEvent', ctypes.c_void_p), # HANDLE
 
375
                   ]
447
376
 
448
377
    class _ctypes_FileLock(_OSLock):
449
378
 
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)
460
 
                raise e
461
 
            fd = msvcrt.open_osfhandle(handle, cflags)
462
 
            self.f = os.fdopen(fd, pymode)
463
 
            return self.f
 
379
        def _lock(self, filename, openmode, lockmode):
 
380
            self._open(filename, openmode)
 
381
 
 
382
            self.hfile = msvcrt.get_osfhandle(self.f.fileno())
 
383
            overlapped = OVERLAPPED()
 
384
            result = _LockFileEx(self.hfile, # HANDLE hFile
 
385
                                 lockmode,   # DWORD dwFlags
 
386
                                 0,          # DWORD dwReserved
 
387
                                 0x7fffffff, # DWORD nNumberOfBytesToLockLow
 
388
                                 0x00000000, # DWORD nNumberOfBytesToLockHigh
 
389
                                 ctypes.byref(overlapped), # lpOverlapped
 
390
                                )
 
391
            if result == 0:
 
392
                self._clear_f()
 
393
                last_err = _GetLastError()
 
394
                if last_err in (ERROR_LOCK_VIOLATION,):
 
395
                    raise errors.LockContention(filename)
 
396
                raise errors.LockContention('Unknown locking error: %s'
 
397
                                            % (last_err,))
464
398
 
465
399
        def unlock(self):
 
400
            overlapped = OVERLAPPED()
 
401
            result = _UnlockFileEx(self.hfile, # HANDLE hFile
 
402
                                   0,          # DWORD dwReserved
 
403
                                   0x7fffffff, # DWORD nNumberOfBytesToLockLow
 
404
                                   0x00000000, # DWORD nNumberOfBytesToLockHigh
 
405
                                   ctypes.byref(overlapped), # lpOverlapped
 
406
                                  )
466
407
            self._clear_f()
 
408
            if result == 0:
 
409
                self._clear_f()
 
410
                last_err = _GetLastError()
 
411
                raise errors.LockContention('Unknown unlocking error: %s'
 
412
                                            % (last_err,))
467
413
 
468
414
 
469
415
    class _ctypes_ReadLock(_ctypes_FileLock):
470
416
        def __init__(self, filename):
471
417
            super(_ctypes_ReadLock, self).__init__()
472
 
            self._open(filename, GENERIC_READ, FILE_SHARE_READ, os.O_RDONLY,
473
 
                "rb")
 
418
            self._lock(filename, 'rb', LOCK_SH + LOCK_NB)
474
419
 
475
420
        def temporary_write_lock(self):
476
421
            """Try to grab a write lock on the file.
494
439
    class _ctypes_WriteLock(_ctypes_FileLock):
495
440
        def __init__(self, filename):
496
441
            super(_ctypes_WriteLock, self).__init__()
497
 
            self._open(filename, GENERIC_READ | GENERIC_WRITE, 0, os.O_RDWR,
498
 
                "rb+")
 
442
            self._lock(filename, 'rb+', LOCK_EX + LOCK_NB)
499
443
 
500
444
        def restore_read_lock(self):
501
445
            """Restore the original ReadLock."""
518
462
# We default to using the first available lock class.
519
463
_lock_type, WriteLock, ReadLock = _lock_classes[0]
520
464
 
521
 
 
522
 
class _RelockDebugMixin(object):
523
 
    """Mixin support for -Drelock flag.
524
 
 
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
528
 
    message about it.
529
 
    """
530
 
    
531
 
    _prev_lock = None
532
 
 
533
 
    def _note_lock(self, lock_type):
534
 
        if 'relock' in debug.debug_flags and self._prev_lock == lock_type:
535
 
            if lock_type == 'r':
536
 
                type_name = 'read'
537
 
            else:
538
 
                type_name = 'write'
539
 
            trace.note('%r was %s locked again', self, type_name)
540
 
        self._prev_lock = lock_type
541