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  • Committer: Robert Collins
  • Date: 2007-10-23 22:14:32 UTC
  • mto: (2592.6.3 repository)
  • mto: This revision was merged to the branch mainline in revision 2967.
  • Revision ID: robertc@robertcollins.net-20071023221432-j8zndh1oiegql3cu
* Commit updates the state of the working tree via a delta rather than
  supplying entirely new basis trees. For commit of a single specified file
  this reduces the wall clock time for commit by roughly a 30%.
  (Robert Collins, Martin Pool)

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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 Hooks
49
 
 
50
 
 
51
 
class LockHooks(Hooks):
52
 
 
53
 
    def __init__(self):
54
 
        Hooks.__init__(self, "bzrlib.lock", "Lock.hooks")
55
 
        self.add_hook('lock_acquired',
56
 
            "Called with a bzrlib.lock.LockResult when a physical lock is "
57
 
            "acquired.", (1, 8))
58
 
        self.add_hook('lock_released',
59
 
            "Called with a bzrlib.lock.LockResult when a physical lock is "
60
 
            "released.", (1, 8))
61
 
        self.add_hook('lock_broken',
62
 
            "Called with a bzrlib.lock.LockResult when a physical lock is "
63
 
            "broken.", (1, 15))
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
 
class LogicalLockResult(object):
92
 
    """The result of a lock_read/lock_write/lock_tree_write call on lockables.
93
 
 
94
 
    :ivar unlock: A callable which will unlock the lock.
95
 
    """
96
 
 
97
 
    def __init__(self, unlock):
98
 
        self.unlock = unlock
99
 
 
100
 
    def __repr__(self):
101
 
        return "LogicalLockResult(%s)" % (self.unlock)
102
 
 
103
 
 
104
 
 
105
 
def cant_unlock_not_held(locked_object):
106
 
    """An attempt to unlock failed because the object was not locked.
107
 
 
108
 
    This provides a policy point from which we can generate either a warning 
109
 
    or an exception.
110
 
    """
111
 
    # This is typically masking some other error and called from a finally
112
 
    # block, so it's useful to have the option not to generate a new error
113
 
    # here.  You can use -Werror to make it fatal.  It should possibly also
114
 
    # raise LockNotHeld.
115
 
    if 'unlock' in debug.debug_flags:
116
 
        warnings.warn("%r is already unlocked" % (locked_object,),
117
 
            stacklevel=3)
118
 
    else:
119
 
        raise errors.LockNotHeld(locked_object)
120
 
 
121
 
 
122
 
try:
123
 
    import fcntl
124
 
    have_fcntl = True
125
 
except ImportError:
126
 
    have_fcntl = False
127
 
 
128
 
have_pywin32 = False
129
 
have_ctypes_win32 = False
130
 
if sys.platform == 'win32':
131
 
    import msvcrt
132
 
    try:
133
 
        import win32file, pywintypes, winerror
134
 
        have_pywin32 = True
135
 
    except ImportError:
136
 
        pass
137
 
 
138
 
    try:
139
 
        import ctypes
140
 
        have_ctypes_win32 = True
141
 
    except ImportError:
142
 
        pass
143
45
 
144
46
 
145
47
class _OSLock(object):
181
83
        raise NotImplementedError()
182
84
 
183
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
 
184
103
_lock_classes = []
185
104
 
186
105
 
187
106
if have_fcntl:
 
107
    LOCK_SH = fcntl.LOCK_SH
 
108
    LOCK_NB = fcntl.LOCK_NB
 
109
    lock_EX = fcntl.LOCK_EX
 
110
 
188
111
 
189
112
    class _fcntl_FileLock(_OSLock):
190
113
 
204
127
            if self.filename in _fcntl_WriteLock._open_locks:
205
128
                self._clear_f()
206
129
                raise errors.LockContention(self.filename)
207
 
            if self.filename in _fcntl_ReadLock._open_locks:
208
 
                if 'strict_locks' in debug.debug_flags:
209
 
                    self._clear_f()
210
 
                    raise errors.LockContention(self.filename)
211
 
                else:
212
 
                    trace.mutter('Write lock taken w/ an open read lock on: %s'
213
 
                                 % (self.filename,))
214
130
 
215
131
            self._open(self.filename, 'rb+')
216
132
            # reserve a slot for this lock - even if the lockf call fails,
217
 
            # 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.
218
134
            # TODO: make this fully threadsafe, if we decide we care.
219
135
            _fcntl_WriteLock._open_locks.add(self.filename)
220
136
            try:
227
143
                    self.unlock()
228
144
                # we should be more precise about whats a locking
229
145
                # error and whats a random-other error
230
 
                raise errors.LockContention(self.filename, e)
 
146
                raise errors.LockContention(e)
231
147
 
232
148
        def unlock(self):
233
149
            _fcntl_WriteLock._open_locks.remove(self.filename)
241
157
        def __init__(self, filename):
242
158
            super(_fcntl_ReadLock, self).__init__()
243
159
            self.filename = osutils.realpath(filename)
244
 
            if self.filename in _fcntl_WriteLock._open_locks:
245
 
                if 'strict_locks' in debug.debug_flags:
246
 
                    # We raise before calling _open so we don't need to
247
 
                    # _clear_f
248
 
                    raise errors.LockContention(self.filename)
249
 
                else:
250
 
                    trace.mutter('Read lock taken w/ an open write lock on: %s'
251
 
                                 % (self.filename,))
252
160
            _fcntl_ReadLock._open_locks.setdefault(self.filename, 0)
253
161
            _fcntl_ReadLock._open_locks[self.filename] += 1
254
162
            self._open(filename, 'rb')
259
167
            except IOError, e:
260
168
                # we should be more precise about whats a locking
261
169
                # error and whats a random-other error
262
 
                raise errors.LockContention(self.filename, e)
 
170
                raise errors.LockContention(e)
263
171
 
264
172
        def unlock(self):
265
173
            count = _fcntl_ReadLock._open_locks[self.filename]
279
187
 
280
188
            :return: A token which can be used to switch back to a read lock.
281
189
            """
282
 
            if self.filename in _fcntl_WriteLock._open_locks:
283
 
                raise AssertionError('file already locked: %r'
284
 
                    % (self.filename,))
 
190
            assert self.filename not in _fcntl_WriteLock._open_locks
285
191
            try:
286
192
                wlock = _fcntl_TemporaryWriteLock(self)
287
193
            except errors.LockError:
307
213
                # write lock.
308
214
                raise errors.LockContention(self.filename)
309
215
 
310
 
            if self.filename in _fcntl_WriteLock._open_locks:
311
 
                raise AssertionError('file already locked: %r'
312
 
                    % (self.filename,))
 
216
            assert self.filename not in _fcntl_WriteLock._open_locks
313
217
 
314
218
            # See if we can open the file for writing. Another process might
315
219
            # have a read lock. We don't use self._open() because we don't want
327
231
                fcntl.lockf(new_f, fcntl.LOCK_EX | fcntl.LOCK_NB)
328
232
            except IOError, e:
329
233
                # TODO: Raise a more specific error based on the type of error
330
 
                raise errors.LockContention(self.filename, e)
 
234
                raise errors.LockContention(e)
331
235
            _fcntl_WriteLock._open_locks.add(self.filename)
332
236
 
333
237
            self.f = new_f
349
253
 
350
254
 
351
255
if have_pywin32 and sys.platform == 'win32':
352
 
    if os.path.supports_unicode_filenames:
353
 
        # for Windows NT/2K/XP/etc
354
 
        win32file_CreateFile = win32file.CreateFileW
355
 
    else:
356
 
        # for Windows 98
357
 
        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
 
358
260
 
359
261
    class _w32c_FileLock(_OSLock):
360
262
 
361
 
        def _open(self, filename, access, share, cflags, pymode):
362
 
            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()
363
268
            try:
364
 
                self._handle = win32file_CreateFile(filename, access, share,
365
 
                    None, win32file.OPEN_ALWAYS,
366
 
                    win32file.FILE_ATTRIBUTE_NORMAL, None)
 
269
                win32file.LockFileEx(self.hfile, lockmode, 0, 0x7fff0000,
 
270
                                     overlapped)
367
271
            except pywintypes.error, e:
368
 
                if e.args[0] == winerror.ERROR_ACCESS_DENIED:
369
 
                    raise errors.LockFailed(filename, e)
370
 
                if e.args[0] == winerror.ERROR_SHARING_VIOLATION:
371
 
                    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()
372
276
                raise
373
 
            fd = win32file._open_osfhandle(self._handle, cflags)
374
 
            self.f = os.fdopen(fd, pymode)
375
 
            return self.f
 
277
            except Exception, e:
 
278
                self._clear_f()
 
279
                raise errors.LockContention(e)
376
280
 
377
281
        def unlock(self):
378
 
            self._clear_f()
379
 
            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)
380
288
 
381
289
 
382
290
    class _w32c_ReadLock(_w32c_FileLock):
383
291
        def __init__(self, filename):
384
292
            super(_w32c_ReadLock, self).__init__()
385
 
            self._open(filename, win32file.GENERIC_READ,
386
 
                win32file.FILE_SHARE_READ, os.O_RDONLY, "rb")
 
293
            self._lock(filename, 'rb', LOCK_SH + LOCK_NB)
387
294
 
388
295
        def temporary_write_lock(self):
389
296
            """Try to grab a write lock on the file.
408
315
    class _w32c_WriteLock(_w32c_FileLock):
409
316
        def __init__(self, filename):
410
317
            super(_w32c_WriteLock, self).__init__()
411
 
            self._open(filename,
412
 
                win32file.GENERIC_READ | win32file.GENERIC_WRITE, 0,
413
 
                os.O_RDWR, "rb+")
 
318
            self._lock(filename, 'rb+', LOCK_EX + LOCK_NB)
414
319
 
415
320
        def restore_read_lock(self):
416
321
            """Restore the original ReadLock."""
423
328
    _lock_classes.append(('pywin32', _w32c_WriteLock, _w32c_ReadLock))
424
329
 
425
330
 
426
 
if have_ctypes_win32:
427
 
    from ctypes.wintypes import DWORD, LPCSTR, LPCWSTR
428
 
    LPSECURITY_ATTRIBUTES = ctypes.c_void_p # used as NULL no need to declare
429
 
    HANDLE = ctypes.c_int # rather than unsigned as in ctypes.wintypes
430
 
    if os.path.supports_unicode_filenames:
431
 
        _function_name = "CreateFileW"
432
 
        LPTSTR = LPCWSTR
433
 
    else:
434
 
        _function_name = "CreateFileA"
435
 
        class LPTSTR(LPCSTR):
436
 
            def __new__(cls, obj):
437
 
                return LPCSTR.__new__(cls, obj.encode("mbcs"))
438
 
 
439
 
    # CreateFile <http://msdn.microsoft.com/en-us/library/aa363858.aspx>
440
 
    _CreateFile = ctypes.WINFUNCTYPE(
441
 
            HANDLE,                # return value
442
 
            LPTSTR,                # lpFileName
443
 
            DWORD,                 # dwDesiredAccess
444
 
            DWORD,                 # dwShareMode
445
 
            LPSECURITY_ATTRIBUTES, # lpSecurityAttributes
446
 
            DWORD,                 # dwCreationDisposition
447
 
            DWORD,                 # dwFlagsAndAttributes
448
 
            HANDLE                 # hTemplateFile
449
 
        )((_function_name, ctypes.windll.kernel32))
450
 
 
451
 
    INVALID_HANDLE_VALUE = -1
452
 
 
453
 
    GENERIC_READ = 0x80000000
454
 
    GENERIC_WRITE = 0x40000000
455
 
    FILE_SHARE_READ = 1
456
 
    OPEN_ALWAYS = 4
457
 
    FILE_ATTRIBUTE_NORMAL = 128
458
 
 
459
 
    ERROR_ACCESS_DENIED = 5
460
 
    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
                   ]
461
376
 
462
377
    class _ctypes_FileLock(_OSLock):
463
378
 
464
 
        def _open(self, filename, access, share, cflags, pymode):
465
 
            self.filename = osutils.realpath(filename)
466
 
            handle = _CreateFile(filename, access, share, None, OPEN_ALWAYS,
467
 
                FILE_ATTRIBUTE_NORMAL, 0)
468
 
            if handle in (INVALID_HANDLE_VALUE, 0):
469
 
                e = ctypes.WinError()
470
 
                if e.args[0] == ERROR_ACCESS_DENIED:
471
 
                    raise errors.LockFailed(filename, e)
472
 
                if e.args[0] == ERROR_SHARING_VIOLATION:
473
 
                    raise errors.LockContention(filename, e)
474
 
                raise e
475
 
            fd = msvcrt.open_osfhandle(handle, cflags)
476
 
            self.f = os.fdopen(fd, pymode)
477
 
            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,))
478
398
 
479
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
                                  )
480
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,))
481
413
 
482
414
 
483
415
    class _ctypes_ReadLock(_ctypes_FileLock):
484
416
        def __init__(self, filename):
485
417
            super(_ctypes_ReadLock, self).__init__()
486
 
            self._open(filename, GENERIC_READ, FILE_SHARE_READ, os.O_RDONLY,
487
 
                "rb")
 
418
            self._lock(filename, 'rb', LOCK_SH + LOCK_NB)
488
419
 
489
420
        def temporary_write_lock(self):
490
421
            """Try to grab a write lock on the file.
508
439
    class _ctypes_WriteLock(_ctypes_FileLock):
509
440
        def __init__(self, filename):
510
441
            super(_ctypes_WriteLock, self).__init__()
511
 
            self._open(filename, GENERIC_READ | GENERIC_WRITE, 0, os.O_RDWR,
512
 
                "rb+")
 
442
            self._lock(filename, 'rb+', LOCK_EX + LOCK_NB)
513
443
 
514
444
        def restore_read_lock(self):
515
445
            """Restore the original ReadLock."""
532
462
# We default to using the first available lock class.
533
463
_lock_type, WriteLock, ReadLock = _lock_classes[0]
534
464
 
535
 
 
536
 
class _RelockDebugMixin(object):
537
 
    """Mixin support for -Drelock flag.
538
 
 
539
 
    Add this as a base class then call self._note_lock with 'r' or 'w' when
540
 
    acquiring a read- or write-lock.  If this object was previously locked (and
541
 
    locked the same way), and -Drelock is set, then this will trace.note a
542
 
    message about it.
543
 
    """
544
 
    
545
 
    _prev_lock = None
546
 
 
547
 
    def _note_lock(self, lock_type):
548
 
        if 'relock' in debug.debug_flags and self._prev_lock == lock_type:
549
 
            if lock_type == 'r':
550
 
                type_name = 'read'
551
 
            else:
552
 
                type_name = 'write'
553
 
            trace.note('%r was %s locked again', self, type_name)
554
 
        self._prev_lock = lock_type
555