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Viewing changes to bzrlib/lock.py

  • Committer: John Arbash Meinel
  • Date: 2009-07-08 15:43:51 UTC
  • mto: This revision was merged to the branch mainline in revision 4521.
  • Revision ID: john@arbash-meinel.com-20090708154351-u0t41fwjqm28pbnu
Add comments in the finally sections as to why we want them.

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bzrlib/lock.py
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# Copyright (C) 2005-2010 Canonical Ltd
 
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# Copyright (C) 2005, 2006, 2007, 2008, 2009 Canonical Ltd
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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import errno
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import os
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import sys
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import warnings
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from bzrlib import (
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    debug,
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    errors,
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    osutils,
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    trace,
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    )
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from bzrlib.hooks import Hooks
 
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from bzrlib.hooks import HookPoint, Hooks
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class LockHooks(Hooks):
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    def __init__(self):
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        Hooks.__init__(self, "bzrlib.lock", "Lock.hooks")
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        self.add_hook('lock_acquired',
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            "Called with a bzrlib.lock.LockResult when a physical lock is "
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            "acquired.", (1, 8))
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        self.add_hook('lock_released',
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            "Called with a bzrlib.lock.LockResult when a physical lock is "
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            "released.", (1, 8))
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        self.add_hook('lock_broken',
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            "Called with a bzrlib.lock.LockResult when a physical lock is "
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            "broken.", (1, 15))
 
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        Hooks.__init__(self)
 
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        self.create_hook(HookPoint('lock_acquired',
 
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            "Called with a bzrlib.lock.LockResult when a physical lock is "
 
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            "acquired.", (1, 8), None))
 
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        self.create_hook(HookPoint('lock_released',
 
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            "Called with a bzrlib.lock.LockResult when a physical lock is "
 
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            "released.", (1, 8), None))
 
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        self.create_hook(HookPoint('lock_broken',
 
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            "Called with a bzrlib.lock.LockResult when a physical lock is "
 
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            "broken.", (1, 15), None))
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class Lock(object):
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        return self.lock_url == other.lock_url and self.details == other.details
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    def __repr__(self):
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        return '%s(%s, %s)' % (self.__class__.__name__,
 
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        return '%s(%s%s)' % (self.__class__.__name__,
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                             self.lock_url, self.details)
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class LogicalLockResult(object):
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    """The result of a lock_read/lock_write/lock_tree_write call on lockables.
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    :ivar unlock: A callable which will unlock the lock.
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    """
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    def __init__(self, unlock):
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        self.unlock = unlock
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    def __repr__(self):
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        return "LogicalLockResult(%s)" % (self.unlock)
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def cant_unlock_not_held(locked_object):
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    """An attempt to unlock failed because the object was not locked.
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    This provides a policy point from which we can generate either a warning 
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    or an exception.
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    """
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    # This is typically masking some other error and called from a finally
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    # block, so it's useful to have the option not to generate a new error
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    # here.  You can use -Werror to make it fatal.  It should possibly also
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    # raise LockNotHeld.
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    if 'unlock' in debug.debug_flags:
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        warnings.warn("%r is already unlocked" % (locked_object,),
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            stacklevel=3)
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    else:
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        raise errors.LockNotHeld(locked_object)
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try:
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    import fcntl
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    have_fcntl = True
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            self.f.close()
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            self.f = None
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    def __del__(self):
 
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        if self.f:
 
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            from warnings import warn
 
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            warn("lock on %r not released" % self.f)
 
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            self.unlock()
 
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    def unlock(self):
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        raise NotImplementedError()
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            if self.filename in _fcntl_WriteLock._open_locks:
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                self._clear_f()
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                raise errors.LockContention(self.filename)
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            if self.filename in _fcntl_ReadLock._open_locks:
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                if 'strict_locks' in debug.debug_flags:
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                    self._clear_f()
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                    raise errors.LockContention(self.filename)
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                else:
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                    trace.mutter('Write lock taken w/ an open read lock on: %s'
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                                 % (self.filename,))
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            self._open(self.filename, 'rb+')
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            # reserve a slot for this lock - even if the lockf call fails,
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            # at this point unlock() will be called, because self.f is set.
 
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            # at thisi point unlock() will be called, because self.f is set.
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            # TODO: make this fully threadsafe, if we decide we care.
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            _fcntl_WriteLock._open_locks.add(self.filename)
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            try:
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        def __init__(self, filename):
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            super(_fcntl_ReadLock, self).__init__()
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            self.filename = osutils.realpath(filename)
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            if self.filename in _fcntl_WriteLock._open_locks:
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                if 'strict_locks' in debug.debug_flags:
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                    # We raise before calling _open so we don't need to
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                    # _clear_f
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                    raise errors.LockContention(self.filename)
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                else:
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                    trace.mutter('Read lock taken w/ an open write lock on: %s'
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                                 % (self.filename,))
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            _fcntl_ReadLock._open_locks.setdefault(self.filename, 0)
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            _fcntl_ReadLock._open_locks[self.filename] += 1
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            self._open(filename, 'rb')
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            DWORD,                 # dwFlagsAndAttributes
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            HANDLE                 # hTemplateFile
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        )((_function_name, ctypes.windll.kernel32))
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    INVALID_HANDLE_VALUE = -1
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    GENERIC_READ = 0x80000000
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    GENERIC_WRITE = 0x40000000
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    FILE_SHARE_READ = 1
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    OPEN_ALWAYS = 4
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    FILE_ATTRIBUTE_NORMAL = 128
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    ERROR_ACCESS_DENIED = 5
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    ERROR_SHARING_VIOLATION = 32
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# We default to using the first available lock class.
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_lock_type, WriteLock, ReadLock = _lock_classes[0]
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class _RelockDebugMixin(object):
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    """Mixin support for -Drelock flag.
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    Add this as a base class then call self._note_lock with 'r' or 'w' when
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    acquiring a read- or write-lock.  If this object was previously locked (and
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    locked the same way), and -Drelock is set, then this will trace.note a
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    message about it.
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    """
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    _prev_lock = None
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    def _note_lock(self, lock_type):
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        if 'relock' in debug.debug_flags and self._prev_lock == lock_type:
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            if lock_type == 'r':
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                type_name = 'read'
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            else:
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                type_name = 'write'
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            trace.note('%r was %s locked again', self, type_name)
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        self._prev_lock = lock_type
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