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  • Committer: Mark Hammond
  • Date: 2009-01-12 01:55:34 UTC
  • mto: (3995.8.2 prepare-1.12)
  • mto: This revision was merged to the branch mainline in revision 4007.
  • Revision ID: mhammond@skippinet.com.au-20090112015534-yfxg50p7mpds9j4v
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bzrlib/lock.py
1
 
# Copyright (C) 2005, 2006, 2007, 2008, 2009 Canonical Ltd
 
1
# Copyright (C) 2005, 2006, 2007, 2008 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
 
45
from bzrlib.hooks import Hooks
49
46
 
50
47
 
51
48
class LockHooks(Hooks):
52
49
 
53
50
    def __init__(self):
54
51
        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))
 
52
 
 
53
        # added in 1.8; called with a LockResult when a physical lock is
 
54
        # acquired
 
55
        self['lock_acquired'] = []
 
56
 
 
57
        # added in 1.8; called with a LockResult when a physical lock is
 
58
        # acquired
 
59
        self['lock_released'] = []
64
60
 
65
61
 
66
62
class Lock(object):
83
79
    def __eq__(self, other):
84
80
        return self.lock_url == other.lock_url and self.details == other.details
85
81
 
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
82
 
108
83
try:
109
84
    import fcntl
116
91
if sys.platform == 'win32':
117
92
    import msvcrt
118
93
    try:
119
 
        import win32file, pywintypes, winerror
 
94
        import win32con, win32file, pywintypes, winerror
120
95
        have_pywin32 = True
121
96
    except ImportError:
122
97
        pass
171
146
 
172
147
 
173
148
if have_fcntl:
 
149
    LOCK_SH = fcntl.LOCK_SH
 
150
    LOCK_NB = fcntl.LOCK_NB
 
151
    lock_EX = fcntl.LOCK_EX
 
152
 
174
153
 
175
154
    class _fcntl_FileLock(_OSLock):
176
155
 
190
169
            if self.filename in _fcntl_WriteLock._open_locks:
191
170
                self._clear_f()
192
171
                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
172
 
201
173
            self._open(self.filename, 'rb+')
202
174
            # reserve a slot for this lock - even if the lockf call fails,
213
185
                    self.unlock()
214
186
                # we should be more precise about whats a locking
215
187
                # error and whats a random-other error
216
 
                raise errors.LockContention(self.filename, e)
 
188
                raise errors.LockContention(e)
217
189
 
218
190
        def unlock(self):
219
191
            _fcntl_WriteLock._open_locks.remove(self.filename)
227
199
        def __init__(self, filename):
228
200
            super(_fcntl_ReadLock, self).__init__()
229
201
            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
202
            _fcntl_ReadLock._open_locks.setdefault(self.filename, 0)
239
203
            _fcntl_ReadLock._open_locks[self.filename] += 1
240
204
            self._open(filename, 'rb')
245
209
            except IOError, e:
246
210
                # we should be more precise about whats a locking
247
211
                # error and whats a random-other error
248
 
                raise errors.LockContention(self.filename, e)
 
212
                raise errors.LockContention(e)
249
213
 
250
214
        def unlock(self):
251
215
            count = _fcntl_ReadLock._open_locks[self.filename]
313
277
                fcntl.lockf(new_f, fcntl.LOCK_EX | fcntl.LOCK_NB)
314
278
            except IOError, e:
315
279
                # TODO: Raise a more specific error based on the type of error
316
 
                raise errors.LockContention(self.filename, e)
 
280
                raise errors.LockContention(e)
317
281
            _fcntl_WriteLock._open_locks.add(self.filename)
318
282
 
319
283
            self.f = new_f
335
299
 
336
300
 
337
301
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
 
302
    LOCK_SH = 0 # the default
 
303
    LOCK_EX = win32con.LOCKFILE_EXCLUSIVE_LOCK
 
304
    LOCK_NB = win32con.LOCKFILE_FAIL_IMMEDIATELY
 
305
 
344
306
 
345
307
    class _w32c_FileLock(_OSLock):
346
308
 
347
 
        def _open(self, filename, access, share, cflags, pymode):
348
 
            self.filename = osutils.realpath(filename)
 
309
        def _lock(self, filename, openmode, lockmode):
 
310
            self._open(filename, openmode)
 
311
 
 
312
            self.hfile = msvcrt.get_osfhandle(self.f.fileno())
 
313
            overlapped = pywintypes.OVERLAPPED()
349
314
            try:
350
 
                self._handle = win32file_CreateFile(filename, access, share,
351
 
                    None, win32file.OPEN_ALWAYS,
352
 
                    win32file.FILE_ATTRIBUTE_NORMAL, None)
 
315
                win32file.LockFileEx(self.hfile, lockmode, 0, 0x7fff0000,
 
316
                                     overlapped)
353
317
            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)
 
318
                self._clear_f()
 
319
                if e.args[0] in (winerror.ERROR_LOCK_VIOLATION,):
 
320
                    raise errors.LockContention(filename)
 
321
                ## import pdb; pdb.set_trace()
358
322
                raise
359
 
            fd = win32file._open_osfhandle(self._handle, cflags)
360
 
            self.f = os.fdopen(fd, pymode)
361
 
            return self.f
 
323
            except Exception, e:
 
324
                self._clear_f()
 
325
                raise errors.LockContention(e)
362
326
 
363
327
        def unlock(self):
364
 
            self._clear_f()
365
 
            self._handle = None
 
328
            overlapped = pywintypes.OVERLAPPED()
 
329
            try:
 
330
                win32file.UnlockFileEx(self.hfile, 0, 0x7fff0000, overlapped)
 
331
                self._clear_f()
 
332
            except Exception, e:
 
333
                raise errors.LockContention(e)
366
334
 
367
335
 
368
336
    class _w32c_ReadLock(_w32c_FileLock):
369
337
        def __init__(self, filename):
370
338
            super(_w32c_ReadLock, self).__init__()
371
 
            self._open(filename, win32file.GENERIC_READ,
372
 
                win32file.FILE_SHARE_READ, os.O_RDONLY, "rb")
 
339
            self._lock(filename, 'rb', LOCK_SH + LOCK_NB)
373
340
 
374
341
        def temporary_write_lock(self):
375
342
            """Try to grab a write lock on the file.
394
361
    class _w32c_WriteLock(_w32c_FileLock):
395
362
        def __init__(self, filename):
396
363
            super(_w32c_WriteLock, self).__init__()
397
 
            self._open(filename,
398
 
                win32file.GENERIC_READ | win32file.GENERIC_WRITE, 0,
399
 
                os.O_RDWR, "rb+")
 
364
            self._lock(filename, 'rb+', LOCK_EX + LOCK_NB)
400
365
 
401
366
        def restore_read_lock(self):
402
367
            """Restore the original ReadLock."""
410
375
 
411
376
 
412
377
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
 
378
    # These constants were copied from the win32con.py module.
 
379
    LOCKFILE_FAIL_IMMEDIATELY = 1
 
380
    LOCKFILE_EXCLUSIVE_LOCK = 2
 
381
    # Constant taken from winerror.py module
 
382
    ERROR_LOCK_VIOLATION = 33
 
383
 
 
384
    LOCK_SH = 0
 
385
    LOCK_EX = LOCKFILE_EXCLUSIVE_LOCK
 
386
    LOCK_NB = LOCKFILE_FAIL_IMMEDIATELY
 
387
    _LockFileEx = ctypes.windll.kernel32.LockFileEx
 
388
    _UnlockFileEx = ctypes.windll.kernel32.UnlockFileEx
 
389
    _GetLastError = ctypes.windll.kernel32.GetLastError
 
390
 
 
391
    ### Define the OVERLAPPED structure.
 
392
    #   http://msdn2.microsoft.com/en-us/library/ms684342.aspx
 
393
    # typedef struct _OVERLAPPED {
 
394
    #   ULONG_PTR Internal;
 
395
    #   ULONG_PTR InternalHigh;
 
396
    #   union {
 
397
    #     struct {
 
398
    #       DWORD Offset;
 
399
    #       DWORD OffsetHigh;
 
400
    #     };
 
401
    #     PVOID Pointer;
 
402
    #   };
 
403
    #   HANDLE hEvent;
 
404
    # } OVERLAPPED,
 
405
 
 
406
    class _inner_struct(ctypes.Structure):
 
407
        _fields_ = [('Offset', ctypes.c_uint), # DWORD
 
408
                    ('OffsetHigh', ctypes.c_uint), # DWORD
 
409
                   ]
 
410
 
 
411
    class _inner_union(ctypes.Union):
 
412
        _fields_  = [('anon_struct', _inner_struct), # struct
 
413
                     ('Pointer', ctypes.c_void_p), # PVOID
 
414
                    ]
 
415
 
 
416
    class OVERLAPPED(ctypes.Structure):
 
417
        _fields_ = [('Internal', ctypes.c_void_p), # ULONG_PTR
 
418
                    ('InternalHigh', ctypes.c_void_p), # ULONG_PTR
 
419
                    ('_inner_union', _inner_union),
 
420
                    ('hEvent', ctypes.c_void_p), # HANDLE
 
421
                   ]
447
422
 
448
423
    class _ctypes_FileLock(_OSLock):
449
424
 
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
 
425
        def _lock(self, filename, openmode, lockmode):
 
426
            self._open(filename, openmode)
 
427
 
 
428
            self.hfile = msvcrt.get_osfhandle(self.f.fileno())
 
429
            overlapped = OVERLAPPED()
 
430
            result = _LockFileEx(self.hfile, # HANDLE hFile
 
431
                                 lockmode,   # DWORD dwFlags
 
432
                                 0,          # DWORD dwReserved
 
433
                                 0x7fffffff, # DWORD nNumberOfBytesToLockLow
 
434
                                 0x00000000, # DWORD nNumberOfBytesToLockHigh
 
435
                                 ctypes.byref(overlapped), # lpOverlapped
 
436
                                )
 
437
            if result == 0:
 
438
                self._clear_f()
 
439
                last_err = _GetLastError()
 
440
                if last_err in (ERROR_LOCK_VIOLATION,):
 
441
                    raise errors.LockContention(filename)
 
442
                raise errors.LockContention('Unknown locking error: %s'
 
443
                                            % (last_err,))
464
444
 
465
445
        def unlock(self):
 
446
            overlapped = OVERLAPPED()
 
447
            result = _UnlockFileEx(self.hfile, # HANDLE hFile
 
448
                                   0,          # DWORD dwReserved
 
449
                                   0x7fffffff, # DWORD nNumberOfBytesToLockLow
 
450
                                   0x00000000, # DWORD nNumberOfBytesToLockHigh
 
451
                                   ctypes.byref(overlapped), # lpOverlapped
 
452
                                  )
466
453
            self._clear_f()
 
454
            if result == 0:
 
455
                self._clear_f()
 
456
                last_err = _GetLastError()
 
457
                raise errors.LockContention('Unknown unlocking error: %s'
 
458
                                            % (last_err,))
467
459
 
468
460
 
469
461
    class _ctypes_ReadLock(_ctypes_FileLock):
470
462
        def __init__(self, filename):
471
463
            super(_ctypes_ReadLock, self).__init__()
472
 
            self._open(filename, GENERIC_READ, FILE_SHARE_READ, os.O_RDONLY,
473
 
                "rb")
 
464
            self._lock(filename, 'rb', LOCK_SH + LOCK_NB)
474
465
 
475
466
        def temporary_write_lock(self):
476
467
            """Try to grab a write lock on the file.
494
485
    class _ctypes_WriteLock(_ctypes_FileLock):
495
486
        def __init__(self, filename):
496
487
            super(_ctypes_WriteLock, self).__init__()
497
 
            self._open(filename, GENERIC_READ | GENERIC_WRITE, 0, os.O_RDWR,
498
 
                "rb+")
 
488
            self._lock(filename, 'rb+', LOCK_EX + LOCK_NB)
499
489
 
500
490
        def restore_read_lock(self):
501
491
            """Restore the original ReadLock."""
518
508
# We default to using the first available lock class.
519
509
_lock_type, WriteLock, ReadLock = _lock_classes[0]
520
510
 
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