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1 | 162c1c1f | Guido Trotter | #
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2 | 162c1c1f | Guido Trotter | #
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3 | 162c1c1f | Guido Trotter | |
4 | 162c1c1f | Guido Trotter | # Copyright (C) 2006, 2007 Google Inc.
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5 | 162c1c1f | Guido Trotter | #
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6 | 162c1c1f | Guido Trotter | # This program is free software; you can redistribute it and/or modify
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7 | 162c1c1f | Guido Trotter | # it under the terms of the GNU General Public License as published by
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8 | 162c1c1f | Guido Trotter | # the Free Software Foundation; either version 2 of the License, or
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9 | 162c1c1f | Guido Trotter | # (at your option) any later version.
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10 | 162c1c1f | Guido Trotter | #
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11 | 162c1c1f | Guido Trotter | # This program is distributed in the hope that it will be useful, but
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12 | 162c1c1f | Guido Trotter | # WITHOUT ANY WARRANTY; without even the implied warranty of
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13 | 162c1c1f | Guido Trotter | # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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14 | 162c1c1f | Guido Trotter | # General Public License for more details.
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15 | 162c1c1f | Guido Trotter | #
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16 | 162c1c1f | Guido Trotter | # You should have received a copy of the GNU General Public License
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17 | 162c1c1f | Guido Trotter | # along with this program; if not, write to the Free Software
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18 | 162c1c1f | Guido Trotter | # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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19 | 162c1c1f | Guido Trotter | # 02110-1301, USA.
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20 | 162c1c1f | Guido Trotter | |
21 | 162c1c1f | Guido Trotter | """Module implementing the Ganeti locking code."""
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22 | 162c1c1f | Guido Trotter | |
23 | 162c1c1f | Guido Trotter | # pylint: disable-msg=W0613,W0201
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24 | 162c1c1f | Guido Trotter | |
25 | 162c1c1f | Guido Trotter | import threading |
26 | a95fd5d7 | Guido Trotter | # Wouldn't it be better to define LockingError in the locking module?
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27 | a95fd5d7 | Guido Trotter | # Well, for now that's how the rest of the code does it...
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28 | a95fd5d7 | Guido Trotter | from ganeti import errors |
29 | 162c1c1f | Guido Trotter | |
30 | 162c1c1f | Guido Trotter | |
31 | 162c1c1f | Guido Trotter | class SharedLock: |
32 | 162c1c1f | Guido Trotter | """Implements a shared lock.
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33 | 162c1c1f | Guido Trotter |
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34 | 162c1c1f | Guido Trotter | Multiple threads can acquire the lock in a shared way, calling
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35 | 162c1c1f | Guido Trotter | acquire_shared(). In order to acquire the lock in an exclusive way threads
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36 | 162c1c1f | Guido Trotter | can call acquire_exclusive().
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37 | 162c1c1f | Guido Trotter |
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38 | 162c1c1f | Guido Trotter | The lock prevents starvation but does not guarantee that threads will acquire
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39 | 162c1c1f | Guido Trotter | the shared lock in the order they queued for it, just that they will
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40 | 162c1c1f | Guido Trotter | eventually do so.
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41 | 162c1c1f | Guido Trotter |
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42 | 162c1c1f | Guido Trotter | """
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43 | 162c1c1f | Guido Trotter | def __init__(self): |
44 | d6646186 | Guido Trotter | """Construct a new SharedLock"""
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45 | 162c1c1f | Guido Trotter | # we have two conditions, c_shr and c_exc, sharing the same lock.
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46 | 162c1c1f | Guido Trotter | self.__lock = threading.Lock()
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47 | 162c1c1f | Guido Trotter | self.__turn_shr = threading.Condition(self.__lock) |
48 | 162c1c1f | Guido Trotter | self.__turn_exc = threading.Condition(self.__lock) |
49 | 162c1c1f | Guido Trotter | |
50 | 162c1c1f | Guido Trotter | # current lock holders
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51 | 162c1c1f | Guido Trotter | self.__shr = set() |
52 | 162c1c1f | Guido Trotter | self.__exc = None |
53 | 162c1c1f | Guido Trotter | |
54 | 162c1c1f | Guido Trotter | # lock waiters
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55 | 162c1c1f | Guido Trotter | self.__nwait_exc = 0 |
56 | 162c1c1f | Guido Trotter | self.__nwait_shr = 0 |
57 | 162c1c1f | Guido Trotter | |
58 | a95fd5d7 | Guido Trotter | # is this lock in the deleted state?
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59 | a95fd5d7 | Guido Trotter | self.__deleted = False |
60 | a95fd5d7 | Guido Trotter | |
61 | 162c1c1f | Guido Trotter | def __is_sharer(self): |
62 | 162c1c1f | Guido Trotter | """Is the current thread sharing the lock at this time?"""
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63 | 162c1c1f | Guido Trotter | return threading.currentThread() in self.__shr |
64 | 162c1c1f | Guido Trotter | |
65 | 162c1c1f | Guido Trotter | def __is_exclusive(self): |
66 | 162c1c1f | Guido Trotter | """Is the current thread holding the lock exclusively at this time?"""
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67 | 162c1c1f | Guido Trotter | return threading.currentThread() == self.__exc |
68 | 162c1c1f | Guido Trotter | |
69 | 162c1c1f | Guido Trotter | def __is_owned(self, shared=-1): |
70 | 162c1c1f | Guido Trotter | """Is the current thread somehow owning the lock at this time?
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71 | 162c1c1f | Guido Trotter |
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72 | 162c1c1f | Guido Trotter | This is a private version of the function, which presumes you're holding
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73 | 162c1c1f | Guido Trotter | the internal lock.
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74 | 162c1c1f | Guido Trotter |
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75 | 162c1c1f | Guido Trotter | """
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76 | 162c1c1f | Guido Trotter | if shared < 0: |
77 | 162c1c1f | Guido Trotter | return self.__is_sharer() or self.__is_exclusive() |
78 | 162c1c1f | Guido Trotter | elif shared:
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79 | 162c1c1f | Guido Trotter | return self.__is_sharer() |
80 | 162c1c1f | Guido Trotter | else:
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81 | 162c1c1f | Guido Trotter | return self.__is_exclusive() |
82 | 162c1c1f | Guido Trotter | |
83 | 162c1c1f | Guido Trotter | def _is_owned(self, shared=-1): |
84 | 162c1c1f | Guido Trotter | """Is the current thread somehow owning the lock at this time?
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85 | 162c1c1f | Guido Trotter |
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86 | 162c1c1f | Guido Trotter | Args:
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87 | 162c1c1f | Guido Trotter | shared:
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88 | 162c1c1f | Guido Trotter | < 0: check for any type of ownership (default)
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89 | 162c1c1f | Guido Trotter | 0: check for exclusive ownership
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90 | 162c1c1f | Guido Trotter | > 0: check for shared ownership
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91 | 162c1c1f | Guido Trotter |
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92 | 162c1c1f | Guido Trotter | """
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93 | 162c1c1f | Guido Trotter | self.__lock.acquire()
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94 | 162c1c1f | Guido Trotter | try:
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95 | 162c1c1f | Guido Trotter | result = self.__is_owned(shared)
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96 | 162c1c1f | Guido Trotter | finally:
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97 | 162c1c1f | Guido Trotter | self.__lock.release()
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98 | 162c1c1f | Guido Trotter | |
99 | 162c1c1f | Guido Trotter | return result
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100 | 162c1c1f | Guido Trotter | |
101 | a95fd5d7 | Guido Trotter | def __wait(self,c): |
102 | a95fd5d7 | Guido Trotter | """Wait on the given condition, and raise an exception if the current lock
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103 | a95fd5d7 | Guido Trotter | is declared deleted in the meantime.
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104 | a95fd5d7 | Guido Trotter |
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105 | a95fd5d7 | Guido Trotter | Args:
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106 | a95fd5d7 | Guido Trotter | c: condition to wait on
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107 | a95fd5d7 | Guido Trotter |
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108 | a95fd5d7 | Guido Trotter | """
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109 | a95fd5d7 | Guido Trotter | c.wait() |
110 | a95fd5d7 | Guido Trotter | if self.__deleted: |
111 | a95fd5d7 | Guido Trotter | raise errors.LockError('deleted lock') |
112 | a95fd5d7 | Guido Trotter | |
113 | a95fd5d7 | Guido Trotter | def __exclusive_acquire(self): |
114 | a95fd5d7 | Guido Trotter | """Acquire the lock exclusively.
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115 | a95fd5d7 | Guido Trotter |
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116 | a95fd5d7 | Guido Trotter | This is a private function that presumes you are already holding the
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117 | a95fd5d7 | Guido Trotter | internal lock. It's defined separately to avoid code duplication between
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118 | a95fd5d7 | Guido Trotter | acquire() and delete()
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119 | a95fd5d7 | Guido Trotter |
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120 | a95fd5d7 | Guido Trotter | """
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121 | a95fd5d7 | Guido Trotter | self.__nwait_exc += 1 |
122 | a95fd5d7 | Guido Trotter | try:
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123 | a95fd5d7 | Guido Trotter | # This is to save ourselves from a nasty race condition that could
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124 | a95fd5d7 | Guido Trotter | # theoretically make the sharers starve.
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125 | a95fd5d7 | Guido Trotter | if self.__nwait_shr > 0 or self.__nwait_exc > 1: |
126 | a95fd5d7 | Guido Trotter | self.__wait(self.__turn_exc) |
127 | a95fd5d7 | Guido Trotter | |
128 | a95fd5d7 | Guido Trotter | while len(self.__shr) > 0 or self.__exc is not None: |
129 | a95fd5d7 | Guido Trotter | self.__wait(self.__turn_exc) |
130 | a95fd5d7 | Guido Trotter | |
131 | a95fd5d7 | Guido Trotter | self.__exc = threading.currentThread()
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132 | a95fd5d7 | Guido Trotter | finally:
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133 | a95fd5d7 | Guido Trotter | self.__nwait_exc -= 1 |
134 | a95fd5d7 | Guido Trotter | |
135 | a95fd5d7 | Guido Trotter | |
136 | 162c1c1f | Guido Trotter | def acquire(self, blocking=1, shared=0): |
137 | 162c1c1f | Guido Trotter | """Acquire a shared lock.
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138 | 162c1c1f | Guido Trotter |
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139 | 162c1c1f | Guido Trotter | Args:
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140 | 162c1c1f | Guido Trotter | shared: whether to acquire in shared mode. By default an exclusive lock
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141 | 162c1c1f | Guido Trotter | will be acquired.
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142 | 162c1c1f | Guido Trotter | blocking: whether to block while trying to acquire or to operate in try-lock mode.
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143 | 162c1c1f | Guido Trotter | this locking mode is not supported yet.
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144 | 162c1c1f | Guido Trotter |
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145 | 162c1c1f | Guido Trotter | """
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146 | 162c1c1f | Guido Trotter | if not blocking: |
147 | 162c1c1f | Guido Trotter | # We don't have non-blocking mode for now
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148 | 162c1c1f | Guido Trotter | raise NotImplementedError |
149 | 162c1c1f | Guido Trotter | |
150 | 162c1c1f | Guido Trotter | self.__lock.acquire()
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151 | 162c1c1f | Guido Trotter | try:
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152 | a95fd5d7 | Guido Trotter | if self.__deleted: |
153 | a95fd5d7 | Guido Trotter | raise errors.LockError('deleted lock') |
154 | a95fd5d7 | Guido Trotter | |
155 | 162c1c1f | Guido Trotter | # We cannot acquire the lock if we already have it
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156 | 162c1c1f | Guido Trotter | assert not self.__is_owned(), "double acquire() on a non-recursive lock" |
157 | 162c1c1f | Guido Trotter | |
158 | 162c1c1f | Guido Trotter | if shared:
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159 | 162c1c1f | Guido Trotter | self.__nwait_shr += 1 |
160 | 162c1c1f | Guido Trotter | try:
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161 | 162c1c1f | Guido Trotter | # If there is an exclusive holder waiting we have to wait. We'll
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162 | 162c1c1f | Guido Trotter | # only do this once, though, when we start waiting for the lock. Then
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163 | 162c1c1f | Guido Trotter | # we'll just wait while there are no exclusive holders.
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164 | 162c1c1f | Guido Trotter | if self.__nwait_exc > 0: |
165 | 162c1c1f | Guido Trotter | # TODO: if !blocking...
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166 | a95fd5d7 | Guido Trotter | self.__wait(self.__turn_shr) |
167 | 162c1c1f | Guido Trotter | |
168 | 162c1c1f | Guido Trotter | while self.__exc is not None: |
169 | 162c1c1f | Guido Trotter | # TODO: if !blocking...
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170 | a95fd5d7 | Guido Trotter | self.__wait(self.__turn_shr) |
171 | 162c1c1f | Guido Trotter | |
172 | 162c1c1f | Guido Trotter | self.__shr.add(threading.currentThread())
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173 | 162c1c1f | Guido Trotter | finally:
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174 | 162c1c1f | Guido Trotter | self.__nwait_shr -= 1 |
175 | 162c1c1f | Guido Trotter | |
176 | 162c1c1f | Guido Trotter | else:
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177 | a95fd5d7 | Guido Trotter | # TODO: if !blocking...
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178 | a95fd5d7 | Guido Trotter | # (or modify __exclusive_acquire for non-blocking mode)
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179 | a95fd5d7 | Guido Trotter | self.__exclusive_acquire()
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180 | 162c1c1f | Guido Trotter | |
181 | 162c1c1f | Guido Trotter | finally:
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182 | 162c1c1f | Guido Trotter | self.__lock.release()
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183 | 162c1c1f | Guido Trotter | |
184 | 162c1c1f | Guido Trotter | return True |
185 | 162c1c1f | Guido Trotter | |
186 | 162c1c1f | Guido Trotter | def release(self): |
187 | 162c1c1f | Guido Trotter | """Release a Shared Lock.
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188 | 162c1c1f | Guido Trotter |
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189 | 162c1c1f | Guido Trotter | You must have acquired the lock, either in shared or in exclusive mode,
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190 | 162c1c1f | Guido Trotter | before calling this function.
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191 | 162c1c1f | Guido Trotter |
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192 | 162c1c1f | Guido Trotter | """
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193 | 162c1c1f | Guido Trotter | self.__lock.acquire()
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194 | 162c1c1f | Guido Trotter | try:
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195 | 162c1c1f | Guido Trotter | # Autodetect release type
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196 | 162c1c1f | Guido Trotter | if self.__is_exclusive(): |
197 | 162c1c1f | Guido Trotter | self.__exc = None |
198 | 162c1c1f | Guido Trotter | |
199 | 162c1c1f | Guido Trotter | # An exclusive holder has just had the lock, time to put it in shared
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200 | 162c1c1f | Guido Trotter | # mode if there are shared holders waiting. Otherwise wake up the next
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201 | 162c1c1f | Guido Trotter | # exclusive holder.
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202 | 162c1c1f | Guido Trotter | if self.__nwait_shr > 0: |
203 | 162c1c1f | Guido Trotter | self.__turn_shr.notifyAll()
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204 | 162c1c1f | Guido Trotter | elif self.__nwait_exc > 0: |
205 | 162c1c1f | Guido Trotter | self.__turn_exc.notify()
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206 | 162c1c1f | Guido Trotter | |
207 | 162c1c1f | Guido Trotter | elif self.__is_sharer(): |
208 | 162c1c1f | Guido Trotter | self.__shr.remove(threading.currentThread())
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209 | 162c1c1f | Guido Trotter | |
210 | 162c1c1f | Guido Trotter | # If there are shared holders waiting there *must* be an exclusive holder
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211 | 162c1c1f | Guido Trotter | # waiting as well; otherwise what were they waiting for?
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212 | 162c1c1f | Guido Trotter | assert (self.__nwait_shr == 0 or self.__nwait_exc > 0, |
213 | 162c1c1f | Guido Trotter | "Lock sharers waiting while no exclusive is queueing")
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214 | 162c1c1f | Guido Trotter | |
215 | 162c1c1f | Guido Trotter | # If there are no more shared holders and some exclusive holders are
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216 | 162c1c1f | Guido Trotter | # waiting let's wake one up.
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217 | 162c1c1f | Guido Trotter | if len(self.__shr) == 0 and self.__nwait_exc > 0: |
218 | 162c1c1f | Guido Trotter | self.__turn_exc.notify()
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219 | 162c1c1f | Guido Trotter | |
220 | 162c1c1f | Guido Trotter | else:
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221 | 162c1c1f | Guido Trotter | assert False, "Cannot release non-owned lock" |
222 | 162c1c1f | Guido Trotter | |
223 | 162c1c1f | Guido Trotter | finally:
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224 | 162c1c1f | Guido Trotter | self.__lock.release()
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225 | 162c1c1f | Guido Trotter | |
226 | a95fd5d7 | Guido Trotter | def delete(self, blocking=1): |
227 | a95fd5d7 | Guido Trotter | """Delete a Shared Lock.
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228 | a95fd5d7 | Guido Trotter |
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229 | a95fd5d7 | Guido Trotter | This operation will declare the lock for removal. First the lock will be
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230 | a95fd5d7 | Guido Trotter | acquired in exclusive mode if you don't already own it, then the lock
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231 | a95fd5d7 | Guido Trotter | will be put in a state where any future and pending acquire() fail.
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232 | a95fd5d7 | Guido Trotter |
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233 | a95fd5d7 | Guido Trotter | Args:
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234 | a95fd5d7 | Guido Trotter | blocking: whether to block while trying to acquire or to operate in
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235 | a95fd5d7 | Guido Trotter | try-lock mode. this locking mode is not supported yet unless
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236 | a95fd5d7 | Guido Trotter | you are already holding exclusively the lock.
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237 | a95fd5d7 | Guido Trotter |
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238 | a95fd5d7 | Guido Trotter | """
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239 | a95fd5d7 | Guido Trotter | self.__lock.acquire()
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240 | a95fd5d7 | Guido Trotter | try:
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241 | a95fd5d7 | Guido Trotter | assert not self.__is_sharer(), "cannot delete() a lock while sharing it" |
242 | a95fd5d7 | Guido Trotter | |
243 | a95fd5d7 | Guido Trotter | if self.__deleted: |
244 | a95fd5d7 | Guido Trotter | raise errors.LockError('deleted lock') |
245 | a95fd5d7 | Guido Trotter | |
246 | a95fd5d7 | Guido Trotter | if not self.__is_exclusive(): |
247 | a95fd5d7 | Guido Trotter | if not blocking: |
248 | a95fd5d7 | Guido Trotter | # We don't have non-blocking mode for now
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249 | a95fd5d7 | Guido Trotter | raise NotImplementedError |
250 | a95fd5d7 | Guido Trotter | self.__exclusive_acquire()
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251 | a95fd5d7 | Guido Trotter | |
252 | a95fd5d7 | Guido Trotter | self.__deleted = True |
253 | a95fd5d7 | Guido Trotter | self.__exc = None |
254 | a95fd5d7 | Guido Trotter | # Wake up everybody, they will fail acquiring the lock and
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255 | a95fd5d7 | Guido Trotter | # raise an exception instead.
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256 | a95fd5d7 | Guido Trotter | self.__turn_exc.notifyAll()
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257 | a95fd5d7 | Guido Trotter | self.__turn_shr.notifyAll()
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258 | a95fd5d7 | Guido Trotter | |
259 | a95fd5d7 | Guido Trotter | finally:
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260 | a95fd5d7 | Guido Trotter | self.__lock.release()
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261 | a95fd5d7 | Guido Trotter | |
262 | aaae9bc0 | Guido Trotter | |
263 | aaae9bc0 | Guido Trotter | class LockSet: |
264 | aaae9bc0 | Guido Trotter | """Implements a set of locks.
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265 | aaae9bc0 | Guido Trotter |
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266 | aaae9bc0 | Guido Trotter | This abstraction implements a set of shared locks for the same resource type,
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267 | aaae9bc0 | Guido Trotter | distinguished by name. The user can lock a subset of the resources and the
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268 | aaae9bc0 | Guido Trotter | LockSet will take care of acquiring the locks always in the same order, thus
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269 | aaae9bc0 | Guido Trotter | preventing deadlock.
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270 | aaae9bc0 | Guido Trotter |
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271 | aaae9bc0 | Guido Trotter | All the locks needed in the same set must be acquired together, though.
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272 | aaae9bc0 | Guido Trotter |
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273 | aaae9bc0 | Guido Trotter | """
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274 | aaae9bc0 | Guido Trotter | def __init__(self, members=None): |
275 | aaae9bc0 | Guido Trotter | """Constructs a new LockSet.
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276 | aaae9bc0 | Guido Trotter |
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277 | aaae9bc0 | Guido Trotter | Args:
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278 | aaae9bc0 | Guido Trotter | members: initial members of the set
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279 | aaae9bc0 | Guido Trotter |
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280 | aaae9bc0 | Guido Trotter | """
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281 | aaae9bc0 | Guido Trotter | # Used internally to guarantee coherency.
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282 | aaae9bc0 | Guido Trotter | self.__lock = SharedLock()
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283 | aaae9bc0 | Guido Trotter | |
284 | aaae9bc0 | Guido Trotter | # The lockdict indexes the relationship name -> lock
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285 | aaae9bc0 | Guido Trotter | # The order-of-locking is implied by the alphabetical order of names
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286 | aaae9bc0 | Guido Trotter | self.__lockdict = {}
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287 | aaae9bc0 | Guido Trotter | |
288 | aaae9bc0 | Guido Trotter | if members is not None: |
289 | aaae9bc0 | Guido Trotter | for name in members: |
290 | aaae9bc0 | Guido Trotter | self.__lockdict[name] = SharedLock()
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291 | aaae9bc0 | Guido Trotter | |
292 | aaae9bc0 | Guido Trotter | # The owner dict contains the set of locks each thread owns. For
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293 | aaae9bc0 | Guido Trotter | # performance each thread can access its own key without a global lock on
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294 | aaae9bc0 | Guido Trotter | # this structure. It is paramount though that *no* other type of access is
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295 | aaae9bc0 | Guido Trotter | # done to this structure (eg. no looping over its keys). *_owner helper
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296 | aaae9bc0 | Guido Trotter | # function are defined to guarantee access is correct, but in general never
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297 | aaae9bc0 | Guido Trotter | # do anything different than __owners[threading.currentThread()], or there
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298 | aaae9bc0 | Guido Trotter | # will be trouble.
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299 | aaae9bc0 | Guido Trotter | self.__owners = {}
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300 | aaae9bc0 | Guido Trotter | |
301 | aaae9bc0 | Guido Trotter | def _is_owned(self): |
302 | aaae9bc0 | Guido Trotter | """Is the current thread a current level owner?"""
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303 | aaae9bc0 | Guido Trotter | return threading.currentThread() in self.__owners |
304 | aaae9bc0 | Guido Trotter | |
305 | aaae9bc0 | Guido Trotter | def _add_owned(self, name): |
306 | aaae9bc0 | Guido Trotter | """Note the current thread owns the given lock"""
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307 | aaae9bc0 | Guido Trotter | if self._is_owned(): |
308 | aaae9bc0 | Guido Trotter | self.__owners[threading.currentThread()].add(name)
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309 | aaae9bc0 | Guido Trotter | else:
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310 | aaae9bc0 | Guido Trotter | self.__owners[threading.currentThread()] = set([name]) |
311 | aaae9bc0 | Guido Trotter | |
312 | aaae9bc0 | Guido Trotter | def _del_owned(self, name): |
313 | aaae9bc0 | Guido Trotter | """Note the current thread owns the given lock"""
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314 | aaae9bc0 | Guido Trotter | self.__owners[threading.currentThread()].remove(name)
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315 | aaae9bc0 | Guido Trotter | |
316 | aaae9bc0 | Guido Trotter | if not self.__owners[threading.currentThread()]: |
317 | aaae9bc0 | Guido Trotter | del self.__owners[threading.currentThread()] |
318 | aaae9bc0 | Guido Trotter | |
319 | aaae9bc0 | Guido Trotter | def _list_owned(self): |
320 | aaae9bc0 | Guido Trotter | """Get the set of resource names owned by the current thread"""
|
321 | aaae9bc0 | Guido Trotter | if self._is_owned(): |
322 | aaae9bc0 | Guido Trotter | return self.__owners[threading.currentThread()].copy() |
323 | aaae9bc0 | Guido Trotter | else:
|
324 | aaae9bc0 | Guido Trotter | return set() |
325 | aaae9bc0 | Guido Trotter | |
326 | aaae9bc0 | Guido Trotter | def __names(self): |
327 | aaae9bc0 | Guido Trotter | """Return the current set of names.
|
328 | aaae9bc0 | Guido Trotter |
|
329 | aaae9bc0 | Guido Trotter | Only call this function while holding __lock and don't iterate on the
|
330 | aaae9bc0 | Guido Trotter | result after releasing the lock.
|
331 | aaae9bc0 | Guido Trotter |
|
332 | aaae9bc0 | Guido Trotter | """
|
333 | aaae9bc0 | Guido Trotter | return set(self.__lockdict.keys()) |
334 | aaae9bc0 | Guido Trotter | |
335 | aaae9bc0 | Guido Trotter | def _names(self): |
336 | aaae9bc0 | Guido Trotter | """Return a copy of the current set of elements.
|
337 | aaae9bc0 | Guido Trotter |
|
338 | aaae9bc0 | Guido Trotter | Used only for debugging purposes.
|
339 | aaae9bc0 | Guido Trotter | """
|
340 | aaae9bc0 | Guido Trotter | self.__lock.acquire(shared=1) |
341 | aaae9bc0 | Guido Trotter | try:
|
342 | aaae9bc0 | Guido Trotter | result = self.__names()
|
343 | aaae9bc0 | Guido Trotter | finally:
|
344 | aaae9bc0 | Guido Trotter | self.__lock.release()
|
345 | aaae9bc0 | Guido Trotter | return result
|
346 | aaae9bc0 | Guido Trotter | |
347 | aaae9bc0 | Guido Trotter | def acquire(self, names, blocking=1, shared=0): |
348 | aaae9bc0 | Guido Trotter | """Acquire a set of resource locks.
|
349 | aaae9bc0 | Guido Trotter |
|
350 | aaae9bc0 | Guido Trotter | Args:
|
351 | aaae9bc0 | Guido Trotter | names: the names of the locks which shall be acquired.
|
352 | aaae9bc0 | Guido Trotter | (special lock names, or instance/node names)
|
353 | aaae9bc0 | Guido Trotter | shared: whether to acquire in shared mode. By default an exclusive lock
|
354 | aaae9bc0 | Guido Trotter | will be acquired.
|
355 | aaae9bc0 | Guido Trotter | blocking: whether to block while trying to acquire or to operate in try-lock mode.
|
356 | aaae9bc0 | Guido Trotter | this locking mode is not supported yet.
|
357 | aaae9bc0 | Guido Trotter |
|
358 | aaae9bc0 | Guido Trotter | Returns:
|
359 | aaae9bc0 | Guido Trotter | True: when all the locks are successfully acquired
|
360 | aaae9bc0 | Guido Trotter |
|
361 | aaae9bc0 | Guido Trotter | Raises:
|
362 | aaae9bc0 | Guido Trotter | errors.LockError: when any lock we try to acquire has been deleted
|
363 | aaae9bc0 | Guido Trotter | before we succeed. In this case none of the locks requested will be
|
364 | aaae9bc0 | Guido Trotter | acquired.
|
365 | aaae9bc0 | Guido Trotter |
|
366 | aaae9bc0 | Guido Trotter | """
|
367 | aaae9bc0 | Guido Trotter | if not blocking: |
368 | aaae9bc0 | Guido Trotter | # We don't have non-blocking mode for now
|
369 | aaae9bc0 | Guido Trotter | raise NotImplementedError |
370 | aaae9bc0 | Guido Trotter | |
371 | aaae9bc0 | Guido Trotter | # Check we don't already own locks at this level
|
372 | aaae9bc0 | Guido Trotter | assert not self._is_owned(), "Cannot acquire locks in the same set twice" |
373 | aaae9bc0 | Guido Trotter | |
374 | aaae9bc0 | Guido Trotter | # Support passing in a single resource to acquire rather than many
|
375 | aaae9bc0 | Guido Trotter | if isinstance(names, basestring): |
376 | aaae9bc0 | Guido Trotter | names = [names] |
377 | aaae9bc0 | Guido Trotter | else:
|
378 | aaae9bc0 | Guido Trotter | names.sort() |
379 | aaae9bc0 | Guido Trotter | |
380 | e6c200d6 | Guido Trotter | acquire_list = [] |
381 | e6c200d6 | Guido Trotter | # First we look the locks up on __lockdict. We have no way of being sure
|
382 | e6c200d6 | Guido Trotter | # they will still be there after, but this makes it a lot faster should
|
383 | e6c200d6 | Guido Trotter | # just one of them be the already wrong
|
384 | aaae9bc0 | Guido Trotter | try:
|
385 | aaae9bc0 | Guido Trotter | for lname in names: |
386 | aaae9bc0 | Guido Trotter | lock = self.__lockdict[lname] # raises KeyError if the lock is not there |
387 | e6c200d6 | Guido Trotter | acquire_list.append((lname, lock)) |
388 | e6c200d6 | Guido Trotter | except (KeyError): |
389 | e6c200d6 | Guido Trotter | raise errors.LockError('non-existing lock in set (%s)' % lname) |
390 | e6c200d6 | Guido Trotter | |
391 | e6c200d6 | Guido Trotter | # Now acquire_list contains a sorted list of resources and locks we want.
|
392 | e6c200d6 | Guido Trotter | # In order to get them we loop on this (private) list and acquire() them.
|
393 | e6c200d6 | Guido Trotter | # We gave no real guarantee they will still exist till this is done but
|
394 | e6c200d6 | Guido Trotter | # .acquire() itself is safe and will alert us if the lock gets deleted.
|
395 | e6c200d6 | Guido Trotter | try:
|
396 | e6c200d6 | Guido Trotter | for (lname, lock) in acquire_list: |
397 | aaae9bc0 | Guido Trotter | lock.acquire(shared=shared) # raises LockError if the lock is deleted
|
398 | aaae9bc0 | Guido Trotter | try:
|
399 | aaae9bc0 | Guido Trotter | # now the lock cannot be deleted, we have it!
|
400 | aaae9bc0 | Guido Trotter | self._add_owned(lname)
|
401 | aaae9bc0 | Guido Trotter | except:
|
402 | aaae9bc0 | Guido Trotter | # We shouldn't have problems adding the lock to the owners list, but
|
403 | aaae9bc0 | Guido Trotter | # if we did we'll try to release this lock and re-raise exception.
|
404 | aaae9bc0 | Guido Trotter | # Of course something is going to be really wrong, after this.
|
405 | aaae9bc0 | Guido Trotter | lock.release() |
406 | aaae9bc0 | Guido Trotter | raise
|
407 | aaae9bc0 | Guido Trotter | |
408 | e6c200d6 | Guido Trotter | except (errors.LockError):
|
409 | aaae9bc0 | Guido Trotter | name_fail = lname |
410 | aaae9bc0 | Guido Trotter | for lname in self._list_owned(): |
411 | aaae9bc0 | Guido Trotter | self.__lockdict[lname].release()
|
412 | aaae9bc0 | Guido Trotter | self._del_owned(lname)
|
413 | aaae9bc0 | Guido Trotter | raise errors.LockError('non-existing lock in set (%s)' % name_fail) |
414 | aaae9bc0 | Guido Trotter | |
415 | aaae9bc0 | Guido Trotter | return True |
416 | aaae9bc0 | Guido Trotter | |
417 | aaae9bc0 | Guido Trotter | def release(self, names=None): |
418 | aaae9bc0 | Guido Trotter | """Release a set of resource locks, at the same level.
|
419 | aaae9bc0 | Guido Trotter |
|
420 | aaae9bc0 | Guido Trotter | You must have acquired the locks, either in shared or in exclusive mode,
|
421 | aaae9bc0 | Guido Trotter | before releasing them.
|
422 | aaae9bc0 | Guido Trotter |
|
423 | aaae9bc0 | Guido Trotter | Args:
|
424 | aaae9bc0 | Guido Trotter | names: the names of the locks which shall be released.
|
425 | aaae9bc0 | Guido Trotter | (defaults to all the locks acquired at that level).
|
426 | aaae9bc0 | Guido Trotter |
|
427 | aaae9bc0 | Guido Trotter | """
|
428 | aaae9bc0 | Guido Trotter | |
429 | aaae9bc0 | Guido Trotter | assert self._is_owned(), "release() on lock set while not owner" |
430 | aaae9bc0 | Guido Trotter | |
431 | aaae9bc0 | Guido Trotter | # Support passing in a single resource to release rather than many
|
432 | aaae9bc0 | Guido Trotter | if isinstance(names, basestring): |
433 | aaae9bc0 | Guido Trotter | names = [names] |
434 | aaae9bc0 | Guido Trotter | |
435 | aaae9bc0 | Guido Trotter | if names is None: |
436 | aaae9bc0 | Guido Trotter | names = self._list_owned()
|
437 | aaae9bc0 | Guido Trotter | else:
|
438 | aaae9bc0 | Guido Trotter | names = set(names)
|
439 | aaae9bc0 | Guido Trotter | assert self._list_owned().issuperset(names), ( |
440 | aaae9bc0 | Guido Trotter | "release() on unheld resources %s" %
|
441 | aaae9bc0 | Guido Trotter | names.difference(self._list_owned()))
|
442 | aaae9bc0 | Guido Trotter | |
443 | aaae9bc0 | Guido Trotter | for lockname in names: |
444 | aaae9bc0 | Guido Trotter | # If we are sure the lock doesn't leave __lockdict without being
|
445 | aaae9bc0 | Guido Trotter | # exclusively held we can do this...
|
446 | aaae9bc0 | Guido Trotter | self.__lockdict[lockname].release()
|
447 | aaae9bc0 | Guido Trotter | self._del_owned(lockname)
|
448 | aaae9bc0 | Guido Trotter | |
449 | aaae9bc0 | Guido Trotter | def add(self, names, acquired=0, shared=0): |
450 | aaae9bc0 | Guido Trotter | """Add a new set of elements to the set
|
451 | aaae9bc0 | Guido Trotter |
|
452 | aaae9bc0 | Guido Trotter | Args:
|
453 | aaae9bc0 | Guido Trotter | names: names of the new elements to add
|
454 | aaae9bc0 | Guido Trotter | acquired: pre-acquire the new resource?
|
455 | aaae9bc0 | Guido Trotter | shared: is the pre-acquisition shared?
|
456 | aaae9bc0 | Guido Trotter |
|
457 | aaae9bc0 | Guido Trotter | """
|
458 | aaae9bc0 | Guido Trotter | # Support passing in a single resource to add rather than many
|
459 | aaae9bc0 | Guido Trotter | if isinstance(names, basestring): |
460 | aaae9bc0 | Guido Trotter | names = [names] |
461 | aaae9bc0 | Guido Trotter | |
462 | aaae9bc0 | Guido Trotter | # Acquire the internal lock in an exclusive way, so there cannot be a
|
463 | aaae9bc0 | Guido Trotter | # conflicting add()
|
464 | aaae9bc0 | Guido Trotter | self.__lock.acquire()
|
465 | aaae9bc0 | Guido Trotter | try:
|
466 | aaae9bc0 | Guido Trotter | invalid_names = self.__names().intersection(names)
|
467 | aaae9bc0 | Guido Trotter | if invalid_names:
|
468 | aaae9bc0 | Guido Trotter | # This must be an explicit raise, not an assert, because assert is
|
469 | aaae9bc0 | Guido Trotter | # turned off when using optimization, and this can happen because of
|
470 | aaae9bc0 | Guido Trotter | # concurrency even if the user doesn't want it.
|
471 | aaae9bc0 | Guido Trotter | raise errors.LockError("duplicate add() (%s)" % invalid_names) |
472 | aaae9bc0 | Guido Trotter | |
473 | aaae9bc0 | Guido Trotter | for lockname in names: |
474 | aaae9bc0 | Guido Trotter | lock = SharedLock() |
475 | aaae9bc0 | Guido Trotter | |
476 | aaae9bc0 | Guido Trotter | if acquired:
|
477 | aaae9bc0 | Guido Trotter | lock.acquire(shared=shared) |
478 | aaae9bc0 | Guido Trotter | # now the lock cannot be deleted, we have it!
|
479 | aaae9bc0 | Guido Trotter | try:
|
480 | aaae9bc0 | Guido Trotter | self._add_owned(lockname)
|
481 | aaae9bc0 | Guido Trotter | except:
|
482 | aaae9bc0 | Guido Trotter | # We shouldn't have problems adding the lock to the owners list,
|
483 | aaae9bc0 | Guido Trotter | # but if we did we'll try to release this lock and re-raise
|
484 | aaae9bc0 | Guido Trotter | # exception. Of course something is going to be really wrong,
|
485 | aaae9bc0 | Guido Trotter | # after this. On the other hand the lock hasn't been added to the
|
486 | aaae9bc0 | Guido Trotter | # __lockdict yet so no other threads should be pending on it. This
|
487 | aaae9bc0 | Guido Trotter | # release is just a safety measure.
|
488 | aaae9bc0 | Guido Trotter | lock.release() |
489 | aaae9bc0 | Guido Trotter | raise
|
490 | aaae9bc0 | Guido Trotter | |
491 | aaae9bc0 | Guido Trotter | self.__lockdict[lockname] = lock
|
492 | aaae9bc0 | Guido Trotter | |
493 | aaae9bc0 | Guido Trotter | finally:
|
494 | aaae9bc0 | Guido Trotter | self.__lock.release()
|
495 | aaae9bc0 | Guido Trotter | |
496 | aaae9bc0 | Guido Trotter | return True |
497 | aaae9bc0 | Guido Trotter | |
498 | aaae9bc0 | Guido Trotter | def remove(self, names, blocking=1): |
499 | aaae9bc0 | Guido Trotter | """Remove elements from the lock set.
|
500 | aaae9bc0 | Guido Trotter |
|
501 | aaae9bc0 | Guido Trotter | You can either not hold anything in the lockset or already hold a superset
|
502 | aaae9bc0 | Guido Trotter | of the elements you want to delete, exclusively.
|
503 | aaae9bc0 | Guido Trotter |
|
504 | aaae9bc0 | Guido Trotter | Args:
|
505 | aaae9bc0 | Guido Trotter | names: names of the resource to remove.
|
506 | aaae9bc0 | Guido Trotter | blocking: whether to block while trying to acquire or to operate in
|
507 | aaae9bc0 | Guido Trotter | try-lock mode. this locking mode is not supported yet unless
|
508 | aaae9bc0 | Guido Trotter | you are already holding exclusively the locks.
|
509 | aaae9bc0 | Guido Trotter |
|
510 | aaae9bc0 | Guido Trotter | Returns:
|
511 | aaae9bc0 | Guido Trotter | A list of lock which we failed to delete. The list is always empty if we
|
512 | aaae9bc0 | Guido Trotter | were holding all the locks exclusively.
|
513 | aaae9bc0 | Guido Trotter |
|
514 | aaae9bc0 | Guido Trotter | """
|
515 | aaae9bc0 | Guido Trotter | if not blocking and not self._is_owned(): |
516 | aaae9bc0 | Guido Trotter | # We don't have non-blocking mode for now
|
517 | aaae9bc0 | Guido Trotter | raise NotImplementedError |
518 | aaae9bc0 | Guido Trotter | |
519 | aaae9bc0 | Guido Trotter | # Support passing in a single resource to remove rather than many
|
520 | aaae9bc0 | Guido Trotter | if isinstance(names, basestring): |
521 | aaae9bc0 | Guido Trotter | names = [names] |
522 | aaae9bc0 | Guido Trotter | |
523 | aaae9bc0 | Guido Trotter | # If we own any subset of this lock it must be a superset of what we want
|
524 | aaae9bc0 | Guido Trotter | # to delete. The ownership must also be exclusive, but that will be checked
|
525 | aaae9bc0 | Guido Trotter | # by the lock itself.
|
526 | aaae9bc0 | Guido Trotter | assert not self._is_owned() or self._list_owned().issuperset(names), ( |
527 | aaae9bc0 | Guido Trotter | "remove() on acquired lockset while not owning all elements")
|
528 | aaae9bc0 | Guido Trotter | |
529 | aaae9bc0 | Guido Trotter | delete_failed=[] |
530 | aaae9bc0 | Guido Trotter | |
531 | aaae9bc0 | Guido Trotter | for lname in names: |
532 | aaae9bc0 | Guido Trotter | # Calling delete() acquires the lock exclusively if we don't already own
|
533 | aaae9bc0 | Guido Trotter | # it, and causes all pending and subsequent lock acquires to fail. It's
|
534 | aaae9bc0 | Guido Trotter | # fine to call it out of order because delete() also implies release(),
|
535 | aaae9bc0 | Guido Trotter | # and the assertion above guarantees that if we either already hold
|
536 | aaae9bc0 | Guido Trotter | # everything we want to delete, or we hold none.
|
537 | aaae9bc0 | Guido Trotter | try:
|
538 | aaae9bc0 | Guido Trotter | self.__lockdict[lname].delete()
|
539 | aaae9bc0 | Guido Trotter | except (KeyError, errors.LockError): |
540 | aaae9bc0 | Guido Trotter | delete_failed.append(lname) |
541 | aaae9bc0 | Guido Trotter | # This cannot happen if we were already holding it, verify:
|
542 | aaae9bc0 | Guido Trotter | assert not self._is_owned(), "remove failed while holding lockset" |
543 | aaae9bc0 | Guido Trotter | else:
|
544 | aaae9bc0 | Guido Trotter | # If no LockError was raised we are the ones who deleted the lock.
|
545 | aaae9bc0 | Guido Trotter | # This means we can safely remove it from lockdict, as any further or
|
546 | aaae9bc0 | Guido Trotter | # pending delete() or acquire() will fail (and nobody can have the lock
|
547 | aaae9bc0 | Guido Trotter | # since before our call to delete()).
|
548 | aaae9bc0 | Guido Trotter | #
|
549 | aaae9bc0 | Guido Trotter | # This is done in an else clause because if the exception was thrown
|
550 | aaae9bc0 | Guido Trotter | # it's the job of the one who actually deleted it.
|
551 | aaae9bc0 | Guido Trotter | del self.__lockdict[lname] |
552 | aaae9bc0 | Guido Trotter | # And let's remove it from our private list if we owned it.
|
553 | aaae9bc0 | Guido Trotter | if self._is_owned(): |
554 | aaae9bc0 | Guido Trotter | self._del_owned(lname)
|
555 | aaae9bc0 | Guido Trotter | |
556 | aaae9bc0 | Guido Trotter | return delete_failed
|