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  • Committer: Robert Collins
  • Date: 2008-09-24 07:33:56 UTC
  • mto: This revision was merged to the branch mainline in revision 3734.
  • Revision ID: robertc@robertcollins.net-20080924073356-dfg5qqbd7f74mwmt
Work around ReST FAIL.

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bzrlib/lock.py
1
 
# Copyright (C) 2005-2010 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
 
 
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
 
 
130
82
 
131
83
class _OSLock(object):
132
84
 
167
119
        raise NotImplementedError()
168
120
 
169
121
 
 
122
try:
 
123
    import fcntl
 
124
    have_fcntl = True
 
125
except ImportError:
 
126
    have_fcntl = False
 
127
try:
 
128
    import win32con, win32file, pywintypes, winerror, msvcrt
 
129
    have_pywin32 = True
 
130
except ImportError:
 
131
    have_pywin32 = False
 
132
try:
 
133
    import ctypes, msvcrt
 
134
    have_ctypes = True
 
135
except ImportError:
 
136
    have_ctypes = False
 
137
 
 
138
 
170
139
_lock_classes = []
171
140
 
172
141
 
173
142
if have_fcntl:
 
143
    LOCK_SH = fcntl.LOCK_SH
 
144
    LOCK_NB = fcntl.LOCK_NB
 
145
    lock_EX = fcntl.LOCK_EX
 
146
 
174
147
 
175
148
    class _fcntl_FileLock(_OSLock):
176
149
 
190
163
            if self.filename in _fcntl_WriteLock._open_locks:
191
164
                self._clear_f()
192
165
                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
166
 
201
167
            self._open(self.filename, 'rb+')
202
168
            # 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.
 
169
            # at thisi point unlock() will be called, because self.f is set.
204
170
            # TODO: make this fully threadsafe, if we decide we care.
205
171
            _fcntl_WriteLock._open_locks.add(self.filename)
206
172
            try:
213
179
                    self.unlock()
214
180
                # we should be more precise about whats a locking
215
181
                # error and whats a random-other error
216
 
                raise errors.LockContention(self.filename, e)
 
182
                raise errors.LockContention(e)
217
183
 
218
184
        def unlock(self):
219
185
            _fcntl_WriteLock._open_locks.remove(self.filename)
227
193
        def __init__(self, filename):
228
194
            super(_fcntl_ReadLock, self).__init__()
229
195
            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
196
            _fcntl_ReadLock._open_locks.setdefault(self.filename, 0)
239
197
            _fcntl_ReadLock._open_locks[self.filename] += 1
240
198
            self._open(filename, 'rb')
245
203
            except IOError, e:
246
204
                # we should be more precise about whats a locking
247
205
                # error and whats a random-other error
248
 
                raise errors.LockContention(self.filename, e)
 
206
                raise errors.LockContention(e)
249
207
 
250
208
        def unlock(self):
251
209
            count = _fcntl_ReadLock._open_locks[self.filename]
313
271
                fcntl.lockf(new_f, fcntl.LOCK_EX | fcntl.LOCK_NB)
314
272
            except IOError, e:
315
273
                # TODO: Raise a more specific error based on the type of error
316
 
                raise errors.LockContention(self.filename, e)
 
274
                raise errors.LockContention(e)
317
275
            _fcntl_WriteLock._open_locks.add(self.filename)
318
276
 
319
277
            self.f = new_f
335
293
 
336
294
 
337
295
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
 
296
    LOCK_SH = 0 # the default
 
297
    LOCK_EX = win32con.LOCKFILE_EXCLUSIVE_LOCK
 
298
    LOCK_NB = win32con.LOCKFILE_FAIL_IMMEDIATELY
 
299
 
344
300
 
345
301
    class _w32c_FileLock(_OSLock):
346
302
 
347
 
        def _open(self, filename, access, share, cflags, pymode):
348
 
            self.filename = osutils.realpath(filename)
 
303
        def _lock(self, filename, openmode, lockmode):
 
304
            self._open(filename, openmode)
 
305
 
 
306
            self.hfile = msvcrt.get_osfhandle(self.f.fileno())
 
307
            overlapped = pywintypes.OVERLAPPED()
349
308
            try:
350
 
                self._handle = win32file_CreateFile(filename, access, share,
351
 
                    None, win32file.OPEN_ALWAYS,
352
 
                    win32file.FILE_ATTRIBUTE_NORMAL, None)
 
309
                win32file.LockFileEx(self.hfile, lockmode, 0, 0x7fff0000,
 
310
                                     overlapped)
353
311
            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)
 
312
                self._clear_f()
 
313
                if e.args[0] in (winerror.ERROR_LOCK_VIOLATION,):
 
314
                    raise errors.LockContention(filename)
 
315
                ## import pdb; pdb.set_trace()
358
316
                raise
359
 
            fd = win32file._open_osfhandle(self._handle, cflags)
360
 
            self.f = os.fdopen(fd, pymode)
361
 
            return self.f
 
317
            except Exception, e:
 
318
                self._clear_f()
 
319
                raise errors.LockContention(e)
362
320
 
363
321
        def unlock(self):
364
 
            self._clear_f()
365
 
            self._handle = None
 
322
            overlapped = pywintypes.OVERLAPPED()
 
323
            try:
 
324
                win32file.UnlockFileEx(self.hfile, 0, 0x7fff0000, overlapped)
 
325
                self._clear_f()
 
326
            except Exception, e:
 
327
                raise errors.LockContention(e)
366
328
 
367
329
 
368
330
    class _w32c_ReadLock(_w32c_FileLock):
369
331
        def __init__(self, filename):
370
332
            super(_w32c_ReadLock, self).__init__()
371
 
            self._open(filename, win32file.GENERIC_READ,
372
 
                win32file.FILE_SHARE_READ, os.O_RDONLY, "rb")
 
333
            self._lock(filename, 'rb', LOCK_SH + LOCK_NB)
373
334
 
374
335
        def temporary_write_lock(self):
375
336
            """Try to grab a write lock on the file.
394
355
    class _w32c_WriteLock(_w32c_FileLock):
395
356
        def __init__(self, filename):
396
357
            super(_w32c_WriteLock, self).__init__()
397
 
            self._open(filename,
398
 
                win32file.GENERIC_READ | win32file.GENERIC_WRITE, 0,
399
 
                os.O_RDWR, "rb+")
 
358
            self._lock(filename, 'rb+', LOCK_EX + LOCK_NB)
400
359
 
401
360
        def restore_read_lock(self):
402
361
            """Restore the original ReadLock."""
409
368
    _lock_classes.append(('pywin32', _w32c_WriteLock, _w32c_ReadLock))
410
369
 
411
370
 
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
 
371
if have_ctypes and sys.platform == 'win32':
 
372
    # These constants were copied from the win32con.py module.
 
373
    LOCKFILE_FAIL_IMMEDIATELY = 1
 
374
    LOCKFILE_EXCLUSIVE_LOCK = 2
 
375
    # Constant taken from winerror.py module
 
376
    ERROR_LOCK_VIOLATION = 33
 
377
 
 
378
    LOCK_SH = 0
 
379
    LOCK_EX = LOCKFILE_EXCLUSIVE_LOCK
 
380
    LOCK_NB = LOCKFILE_FAIL_IMMEDIATELY
 
381
    _LockFileEx = ctypes.windll.kernel32.LockFileEx
 
382
    _UnlockFileEx = ctypes.windll.kernel32.UnlockFileEx
 
383
    _GetLastError = ctypes.windll.kernel32.GetLastError
 
384
 
 
385
    ### Define the OVERLAPPED structure.
 
386
    #   http://msdn2.microsoft.com/en-us/library/ms684342.aspx
 
387
    # typedef struct _OVERLAPPED {
 
388
    #   ULONG_PTR Internal;
 
389
    #   ULONG_PTR InternalHigh;
 
390
    #   union {
 
391
    #     struct {
 
392
    #       DWORD Offset;
 
393
    #       DWORD OffsetHigh;
 
394
    #     };
 
395
    #     PVOID Pointer;
 
396
    #   };
 
397
    #   HANDLE hEvent;
 
398
    # } OVERLAPPED,
 
399
 
 
400
    class _inner_struct(ctypes.Structure):
 
401
        _fields_ = [('Offset', ctypes.c_uint), # DWORD
 
402
                    ('OffsetHigh', ctypes.c_uint), # DWORD
 
403
                   ]
 
404
 
 
405
    class _inner_union(ctypes.Union):
 
406
        _fields_  = [('anon_struct', _inner_struct), # struct
 
407
                     ('Pointer', ctypes.c_void_p), # PVOID
 
408
                    ]
 
409
 
 
410
    class OVERLAPPED(ctypes.Structure):
 
411
        _fields_ = [('Internal', ctypes.c_void_p), # ULONG_PTR
 
412
                    ('InternalHigh', ctypes.c_void_p), # ULONG_PTR
 
413
                    ('_inner_union', _inner_union),
 
414
                    ('hEvent', ctypes.c_void_p), # HANDLE
 
415
                   ]
447
416
 
448
417
    class _ctypes_FileLock(_OSLock):
449
418
 
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
 
419
        def _lock(self, filename, openmode, lockmode):
 
420
            self._open(filename, openmode)
 
421
 
 
422
            self.hfile = msvcrt.get_osfhandle(self.f.fileno())
 
423
            overlapped = OVERLAPPED()
 
424
            result = _LockFileEx(self.hfile, # HANDLE hFile
 
425
                                 lockmode,   # DWORD dwFlags
 
426
                                 0,          # DWORD dwReserved
 
427
                                 0x7fffffff, # DWORD nNumberOfBytesToLockLow
 
428
                                 0x00000000, # DWORD nNumberOfBytesToLockHigh
 
429
                                 ctypes.byref(overlapped), # lpOverlapped
 
430
                                )
 
431
            if result == 0:
 
432
                self._clear_f()
 
433
                last_err = _GetLastError()
 
434
                if last_err in (ERROR_LOCK_VIOLATION,):
 
435
                    raise errors.LockContention(filename)
 
436
                raise errors.LockContention('Unknown locking error: %s'
 
437
                                            % (last_err,))
464
438
 
465
439
        def unlock(self):
 
440
            overlapped = OVERLAPPED()
 
441
            result = _UnlockFileEx(self.hfile, # HANDLE hFile
 
442
                                   0,          # DWORD dwReserved
 
443
                                   0x7fffffff, # DWORD nNumberOfBytesToLockLow
 
444
                                   0x00000000, # DWORD nNumberOfBytesToLockHigh
 
445
                                   ctypes.byref(overlapped), # lpOverlapped
 
446
                                  )
466
447
            self._clear_f()
 
448
            if result == 0:
 
449
                self._clear_f()
 
450
                last_err = _GetLastError()
 
451
                raise errors.LockContention('Unknown unlocking error: %s'
 
452
                                            % (last_err,))
467
453
 
468
454
 
469
455
    class _ctypes_ReadLock(_ctypes_FileLock):
470
456
        def __init__(self, filename):
471
457
            super(_ctypes_ReadLock, self).__init__()
472
 
            self._open(filename, GENERIC_READ, FILE_SHARE_READ, os.O_RDONLY,
473
 
                "rb")
 
458
            self._lock(filename, 'rb', LOCK_SH + LOCK_NB)
474
459
 
475
460
        def temporary_write_lock(self):
476
461
            """Try to grab a write lock on the file.
494
479
    class _ctypes_WriteLock(_ctypes_FileLock):
495
480
        def __init__(self, filename):
496
481
            super(_ctypes_WriteLock, self).__init__()
497
 
            self._open(filename, GENERIC_READ | GENERIC_WRITE, 0, os.O_RDWR,
498
 
                "rb+")
 
482
            self._lock(filename, 'rb+', LOCK_EX + LOCK_NB)
499
483
 
500
484
        def restore_read_lock(self):
501
485
            """Restore the original ReadLock."""
518
502
# We default to using the first available lock class.
519
503
_lock_type, WriteLock, ReadLock = _lock_classes[0]
520
504
 
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