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Viewing changes to bzrlib/lock.py

  • Committer: John Arbash Meinel
  • Date: 2008-10-04 14:10:13 UTC
  • mto: This revision was merged to the branch mainline in revision 3805.
  • Revision ID: john@arbash-meinel.com-20081004141013-yskxjlwtuy2k18ue
Playing around with expanding requests for btree index nodes into neighboring nodes.

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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,
51
48
class LockHooks(Hooks):
52
49
 
53
50
    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))
 
51
        Hooks.__init__(self)
 
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
 
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
82
 
122
83
try:
123
84
    import fcntl
130
91
if sys.platform == 'win32':
131
92
    import msvcrt
132
93
    try:
133
 
        import win32file, pywintypes, winerror
 
94
        import win32con, win32file, pywintypes, winerror
134
95
        have_pywin32 = True
135
96
    except ImportError:
136
97
        pass
171
132
            self.f.close()
172
133
            self.f = None
173
134
 
 
135
    def __del__(self):
 
136
        if self.f:
 
137
            from warnings import warn
 
138
            warn("lock on %r not released" % self.f)
 
139
            self.unlock()
 
140
 
174
141
    def unlock(self):
175
142
        raise NotImplementedError()
176
143
 
179
146
 
180
147
 
181
148
if have_fcntl:
 
149
    LOCK_SH = fcntl.LOCK_SH
 
150
    LOCK_NB = fcntl.LOCK_NB
 
151
    lock_EX = fcntl.LOCK_EX
 
152
 
182
153
 
183
154
    class _fcntl_FileLock(_OSLock):
184
155
 
198
169
            if self.filename in _fcntl_WriteLock._open_locks:
199
170
                self._clear_f()
200
171
                raise errors.LockContention(self.filename)
201
 
            if self.filename in _fcntl_ReadLock._open_locks:
202
 
                if 'strict_locks' in debug.debug_flags:
203
 
                    self._clear_f()
204
 
                    raise errors.LockContention(self.filename)
205
 
                else:
206
 
                    trace.mutter('Write lock taken w/ an open read lock on: %s'
207
 
                                 % (self.filename,))
208
172
 
209
173
            self._open(self.filename, 'rb+')
210
174
            # reserve a slot for this lock - even if the lockf call fails,
211
 
            # at this point unlock() will be called, because self.f is set.
 
175
            # at thisi point unlock() will be called, because self.f is set.
212
176
            # TODO: make this fully threadsafe, if we decide we care.
213
177
            _fcntl_WriteLock._open_locks.add(self.filename)
214
178
            try:
221
185
                    self.unlock()
222
186
                # we should be more precise about whats a locking
223
187
                # error and whats a random-other error
224
 
                raise errors.LockContention(self.filename, e)
 
188
                raise errors.LockContention(e)
225
189
 
226
190
        def unlock(self):
227
191
            _fcntl_WriteLock._open_locks.remove(self.filename)
235
199
        def __init__(self, filename):
236
200
            super(_fcntl_ReadLock, self).__init__()
237
201
            self.filename = osutils.realpath(filename)
238
 
            if self.filename in _fcntl_WriteLock._open_locks:
239
 
                if 'strict_locks' in debug.debug_flags:
240
 
                    # We raise before calling _open so we don't need to
241
 
                    # _clear_f
242
 
                    raise errors.LockContention(self.filename)
243
 
                else:
244
 
                    trace.mutter('Read lock taken w/ an open write lock on: %s'
245
 
                                 % (self.filename,))
246
202
            _fcntl_ReadLock._open_locks.setdefault(self.filename, 0)
247
203
            _fcntl_ReadLock._open_locks[self.filename] += 1
248
204
            self._open(filename, 'rb')
253
209
            except IOError, e:
254
210
                # we should be more precise about whats a locking
255
211
                # error and whats a random-other error
256
 
                raise errors.LockContention(self.filename, e)
 
212
                raise errors.LockContention(e)
257
213
 
258
214
        def unlock(self):
259
215
            count = _fcntl_ReadLock._open_locks[self.filename]
321
277
                fcntl.lockf(new_f, fcntl.LOCK_EX | fcntl.LOCK_NB)
322
278
            except IOError, e:
323
279
                # TODO: Raise a more specific error based on the type of error
324
 
                raise errors.LockContention(self.filename, e)
 
280
                raise errors.LockContention(e)
325
281
            _fcntl_WriteLock._open_locks.add(self.filename)
326
282
 
327
283
            self.f = new_f
343
299
 
344
300
 
345
301
if have_pywin32 and sys.platform == 'win32':
346
 
    if os.path.supports_unicode_filenames:
347
 
        # for Windows NT/2K/XP/etc
348
 
        win32file_CreateFile = win32file.CreateFileW
349
 
    else:
350
 
        # for Windows 98
351
 
        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
 
352
306
 
353
307
    class _w32c_FileLock(_OSLock):
354
308
 
355
 
        def _open(self, filename, access, share, cflags, pymode):
356
 
            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()
357
314
            try:
358
 
                self._handle = win32file_CreateFile(filename, access, share,
359
 
                    None, win32file.OPEN_ALWAYS,
360
 
                    win32file.FILE_ATTRIBUTE_NORMAL, None)
 
315
                win32file.LockFileEx(self.hfile, lockmode, 0, 0x7fff0000,
 
316
                                     overlapped)
361
317
            except pywintypes.error, e:
362
 
                if e.args[0] == winerror.ERROR_ACCESS_DENIED:
363
 
                    raise errors.LockFailed(filename, e)
364
 
                if e.args[0] == winerror.ERROR_SHARING_VIOLATION:
365
 
                    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()
366
322
                raise
367
 
            fd = win32file._open_osfhandle(self._handle, cflags)
368
 
            self.f = os.fdopen(fd, pymode)
369
 
            return self.f
 
323
            except Exception, e:
 
324
                self._clear_f()
 
325
                raise errors.LockContention(e)
370
326
 
371
327
        def unlock(self):
372
 
            self._clear_f()
373
 
            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)
374
334
 
375
335
 
376
336
    class _w32c_ReadLock(_w32c_FileLock):
377
337
        def __init__(self, filename):
378
338
            super(_w32c_ReadLock, self).__init__()
379
 
            self._open(filename, win32file.GENERIC_READ,
380
 
                win32file.FILE_SHARE_READ, os.O_RDONLY, "rb")
 
339
            self._lock(filename, 'rb', LOCK_SH + LOCK_NB)
381
340
 
382
341
        def temporary_write_lock(self):
383
342
            """Try to grab a write lock on the file.
402
361
    class _w32c_WriteLock(_w32c_FileLock):
403
362
        def __init__(self, filename):
404
363
            super(_w32c_WriteLock, self).__init__()
405
 
            self._open(filename,
406
 
                win32file.GENERIC_READ | win32file.GENERIC_WRITE, 0,
407
 
                os.O_RDWR, "rb+")
 
364
            self._lock(filename, 'rb+', LOCK_EX + LOCK_NB)
408
365
 
409
366
        def restore_read_lock(self):
410
367
            """Restore the original ReadLock."""
418
375
 
419
376
 
420
377
if have_ctypes_win32:
421
 
    from ctypes.wintypes import DWORD, LPCSTR, LPCWSTR
422
 
    LPSECURITY_ATTRIBUTES = ctypes.c_void_p # used as NULL no need to declare
423
 
    HANDLE = ctypes.c_int # rather than unsigned as in ctypes.wintypes
424
 
    if os.path.supports_unicode_filenames:
425
 
        _function_name = "CreateFileW"
426
 
        LPTSTR = LPCWSTR
427
 
    else:
428
 
        _function_name = "CreateFileA"
429
 
        class LPTSTR(LPCSTR):
430
 
            def __new__(cls, obj):
431
 
                return LPCSTR.__new__(cls, obj.encode("mbcs"))
432
 
 
433
 
    # CreateFile <http://msdn.microsoft.com/en-us/library/aa363858.aspx>
434
 
    _CreateFile = ctypes.WINFUNCTYPE(
435
 
            HANDLE,                # return value
436
 
            LPTSTR,                # lpFileName
437
 
            DWORD,                 # dwDesiredAccess
438
 
            DWORD,                 # dwShareMode
439
 
            LPSECURITY_ATTRIBUTES, # lpSecurityAttributes
440
 
            DWORD,                 # dwCreationDisposition
441
 
            DWORD,                 # dwFlagsAndAttributes
442
 
            HANDLE                 # hTemplateFile
443
 
        )((_function_name, ctypes.windll.kernel32))
444
 
 
445
 
    INVALID_HANDLE_VALUE = -1
446
 
 
447
 
    GENERIC_READ = 0x80000000
448
 
    GENERIC_WRITE = 0x40000000
449
 
    FILE_SHARE_READ = 1
450
 
    OPEN_ALWAYS = 4
451
 
    FILE_ATTRIBUTE_NORMAL = 128
452
 
 
453
 
    ERROR_ACCESS_DENIED = 5
454
 
    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
                   ]
455
422
 
456
423
    class _ctypes_FileLock(_OSLock):
457
424
 
458
 
        def _open(self, filename, access, share, cflags, pymode):
459
 
            self.filename = osutils.realpath(filename)
460
 
            handle = _CreateFile(filename, access, share, None, OPEN_ALWAYS,
461
 
                FILE_ATTRIBUTE_NORMAL, 0)
462
 
            if handle in (INVALID_HANDLE_VALUE, 0):
463
 
                e = ctypes.WinError()
464
 
                if e.args[0] == ERROR_ACCESS_DENIED:
465
 
                    raise errors.LockFailed(filename, e)
466
 
                if e.args[0] == ERROR_SHARING_VIOLATION:
467
 
                    raise errors.LockContention(filename, e)
468
 
                raise e
469
 
            fd = msvcrt.open_osfhandle(handle, cflags)
470
 
            self.f = os.fdopen(fd, pymode)
471
 
            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,))
472
444
 
473
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
                                  )
474
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,))
475
459
 
476
460
 
477
461
    class _ctypes_ReadLock(_ctypes_FileLock):
478
462
        def __init__(self, filename):
479
463
            super(_ctypes_ReadLock, self).__init__()
480
 
            self._open(filename, GENERIC_READ, FILE_SHARE_READ, os.O_RDONLY,
481
 
                "rb")
 
464
            self._lock(filename, 'rb', LOCK_SH + LOCK_NB)
482
465
 
483
466
        def temporary_write_lock(self):
484
467
            """Try to grab a write lock on the file.
502
485
    class _ctypes_WriteLock(_ctypes_FileLock):
503
486
        def __init__(self, filename):
504
487
            super(_ctypes_WriteLock, self).__init__()
505
 
            self._open(filename, GENERIC_READ | GENERIC_WRITE, 0, os.O_RDWR,
506
 
                "rb+")
 
488
            self._lock(filename, 'rb+', LOCK_EX + LOCK_NB)
507
489
 
508
490
        def restore_read_lock(self):
509
491
            """Restore the original ReadLock."""
526
508
# We default to using the first available lock class.
527
509
_lock_type, WriteLock, ReadLock = _lock_classes[0]
528
510
 
529
 
 
530
 
class _RelockDebugMixin(object):
531
 
    """Mixin support for -Drelock flag.
532
 
 
533
 
    Add this as a base class then call self._note_lock with 'r' or 'w' when
534
 
    acquiring a read- or write-lock.  If this object was previously locked (and
535
 
    locked the same way), and -Drelock is set, then this will trace.note a
536
 
    message about it.
537
 
    """
538
 
    
539
 
    _prev_lock = None
540
 
 
541
 
    def _note_lock(self, lock_type):
542
 
        if 'relock' in debug.debug_flags and self._prev_lock == lock_type:
543
 
            if lock_type == 'r':
544
 
                type_name = 'read'
545
 
            else:
546
 
                type_name = 'write'
547
 
            trace.note('%r was %s locked again', self, type_name)
548
 
        self._prev_lock = lock_type
549