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@@ -1,436 +1,441 b'' | |||
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1 | 1 | # lock.py - simple advisory locking scheme for mercurial |
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2 | 2 | # |
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3 | 3 | # Copyright 2005, 2006 Matt Mackall <mpm@selenic.com> |
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4 | 4 | # |
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5 | 5 | # This software may be used and distributed according to the terms of the |
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6 | 6 | # GNU General Public License version 2 or any later version. |
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7 | 7 | |
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8 | 8 | from __future__ import absolute_import |
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9 | 9 | |
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10 | 10 | import contextlib |
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11 | 11 | import errno |
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12 | 12 | import os |
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13 | 13 | import signal |
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14 | 14 | import socket |
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15 | 15 | import time |
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16 | 16 | import warnings |
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17 | 17 | |
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18 | 18 | from .i18n import _ |
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19 | 19 | from .pycompat import getattr |
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20 | 20 | |
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21 | 21 | from . import ( |
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22 | 22 | encoding, |
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23 | 23 | error, |
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24 | 24 | pycompat, |
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25 | 25 | util, |
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26 | 26 | ) |
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27 | 27 | |
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28 | 28 | from .utils import procutil |
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29 | 29 | |
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30 | 30 | |
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31 | 31 | def _getlockprefix(): |
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32 | 32 | """Return a string which is used to differentiate pid namespaces |
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33 | 33 | |
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34 | 34 | It's useful to detect "dead" processes and remove stale locks with |
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35 | 35 | confidence. Typically it's just hostname. On modern linux, we include an |
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36 | 36 | extra Linux-specific pid namespace identifier. |
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37 | 37 | """ |
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38 | 38 | result = encoding.strtolocal(socket.gethostname()) |
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39 | 39 | if pycompat.sysplatform.startswith(b'linux'): |
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40 | 40 | try: |
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41 | 41 | result += b'/%x' % os.stat(b'/proc/self/ns/pid').st_ino |
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42 | 42 | except OSError as ex: |
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43 | 43 | if ex.errno not in (errno.ENOENT, errno.EACCES, errno.ENOTDIR): |
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44 | 44 | raise |
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45 | 45 | return result |
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46 | 46 | |
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47 | 47 | |
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48 | 48 | @contextlib.contextmanager |
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49 | 49 | def _delayedinterrupt(): |
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50 | 50 | """Block signal interrupt while doing something critical |
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51 | 51 | |
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52 | 52 | This makes sure that the code block wrapped by this context manager won't |
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53 | 53 | be interrupted. |
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54 | 54 | |
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55 | 55 | For Windows developers: It appears not possible to guard time.sleep() |
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56 | 56 | from CTRL_C_EVENT, so please don't use time.sleep() to test if this is |
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57 | 57 | working. |
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58 | 58 | """ |
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59 | 59 | assertedsigs = [] |
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60 | 60 | blocked = False |
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61 | 61 | orighandlers = {} |
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62 | 62 | |
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63 | 63 | def raiseinterrupt(num): |
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64 | 64 | if num == getattr(signal, 'SIGINT', None) or num == getattr( |
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65 | 65 | signal, 'CTRL_C_EVENT', None |
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66 | 66 | ): |
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67 | 67 | raise KeyboardInterrupt |
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68 | 68 | else: |
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69 | 69 | raise error.SignalInterrupt |
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70 | 70 | |
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71 | 71 | def catchterm(num, frame): |
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72 | 72 | if blocked: |
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73 | 73 | assertedsigs.append(num) |
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74 | 74 | else: |
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75 | 75 | raiseinterrupt(num) |
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76 | 76 | |
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77 | 77 | try: |
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78 | 78 | # save handlers first so they can be restored even if a setup is |
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79 | 79 | # interrupted between signal.signal() and orighandlers[] =. |
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80 | 80 | for name in [ |
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81 | 81 | b'CTRL_C_EVENT', |
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82 | 82 | b'SIGINT', |
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83 | 83 | b'SIGBREAK', |
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84 | 84 | b'SIGHUP', |
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85 | 85 | b'SIGTERM', |
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86 | 86 | ]: |
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87 | 87 | num = getattr(signal, name, None) |
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88 | 88 | if num and num not in orighandlers: |
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89 | 89 | orighandlers[num] = signal.getsignal(num) |
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90 | 90 | try: |
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91 | 91 | for num in orighandlers: |
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92 | 92 | signal.signal(num, catchterm) |
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93 | 93 | except ValueError: |
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94 | 94 | pass # in a thread? no luck |
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95 | 95 | |
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96 | 96 | blocked = True |
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97 | 97 | yield |
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98 | 98 | finally: |
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99 | 99 | # no simple way to reliably restore all signal handlers because |
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100 | 100 | # any loops, recursive function calls, except blocks, etc. can be |
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101 | 101 | # interrupted. so instead, make catchterm() raise interrupt. |
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102 | 102 | blocked = False |
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103 | 103 | try: |
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104 | 104 | for num, handler in orighandlers.items(): |
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105 | 105 | signal.signal(num, handler) |
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106 | 106 | except ValueError: |
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107 | 107 | pass # in a thread? |
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108 | 108 | |
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109 | 109 | # re-raise interrupt exception if any, which may be shadowed by a new |
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110 | 110 | # interrupt occurred while re-raising the first one |
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111 | 111 | if assertedsigs: |
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112 | 112 | raiseinterrupt(assertedsigs[0]) |
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113 | 113 | |
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114 | 114 | |
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115 | 115 | def trylock(ui, vfs, lockname, timeout, warntimeout, *args, **kwargs): |
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116 | 116 | """return an acquired lock or raise an a LockHeld exception |
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117 | 117 | |
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118 | 118 | This function is responsible to issue warnings and or debug messages about |
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119 | 119 | the held lock while trying to acquires it.""" |
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120 | 120 | |
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121 | 121 | def printwarning(printer, locker): |
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122 | 122 | """issue the usual "waiting on lock" message through any channel""" |
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123 | 123 | # show more details for new-style locks |
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124 | 124 | if b':' in locker: |
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125 | 125 | host, pid = locker.split(b":", 1) |
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126 | 126 | msg = _( |
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127 | 127 | b"waiting for lock on %s held by process %r on host %r\n" |
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128 | 128 | ) % ( |
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129 | 129 | pycompat.bytestr(l.desc), |
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130 | 130 | pycompat.bytestr(pid), |
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131 | 131 | pycompat.bytestr(host), |
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132 | 132 | ) |
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133 | 133 | else: |
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134 | 134 | msg = _(b"waiting for lock on %s held by %r\n") % ( |
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135 | 135 | l.desc, |
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136 | 136 | pycompat.bytestr(locker), |
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137 | 137 | ) |
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138 | 138 | printer(msg) |
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139 | 139 | |
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140 | 140 | l = lock(vfs, lockname, 0, *args, dolock=False, **kwargs) |
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141 | 141 | |
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142 | 142 | debugidx = 0 if (warntimeout and timeout) else -1 |
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143 | 143 | warningidx = 0 |
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144 | 144 | if not timeout: |
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145 | 145 | warningidx = -1 |
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146 | 146 | elif warntimeout: |
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147 | 147 | warningidx = warntimeout |
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148 | 148 | |
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149 | 149 | delay = 0 |
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150 | 150 | while True: |
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151 | 151 | try: |
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152 | 152 | l._trylock() |
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153 | 153 | break |
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154 | 154 | except error.LockHeld as inst: |
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155 | 155 | if delay == debugidx: |
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156 | 156 | printwarning(ui.debug, inst.locker) |
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157 | 157 | if delay == warningidx: |
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158 | 158 | printwarning(ui.warn, inst.locker) |
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159 | 159 | if timeout <= delay: |
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160 | 160 | raise error.LockHeld( |
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161 | 161 | errno.ETIMEDOUT, inst.filename, l.desc, inst.locker |
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162 | 162 | ) |
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163 | 163 | time.sleep(1) |
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164 | 164 | delay += 1 |
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165 | 165 | |
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166 | 166 | l.delay = delay |
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167 | 167 | if l.delay: |
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168 | 168 | if 0 <= warningidx <= l.delay: |
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169 | 169 | ui.warn(_(b"got lock after %d seconds\n") % l.delay) |
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170 | 170 | else: |
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171 | 171 | ui.debug(b"got lock after %d seconds\n" % l.delay) |
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172 | 172 | if l.acquirefn: |
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173 | 173 | l.acquirefn() |
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174 | 174 | return l |
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175 | 175 | |
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176 | 176 | |
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177 | 177 | class lock(object): |
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178 | 178 | '''An advisory lock held by one process to control access to a set |
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179 | 179 | of files. Non-cooperating processes or incorrectly written scripts |
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180 | 180 | can ignore Mercurial's locking scheme and stomp all over the |
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181 | 181 | repository, so don't do that. |
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182 | 182 | |
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183 | 183 | Typically used via localrepository.lock() to lock the repository |
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184 | 184 | store (.hg/store/) or localrepository.wlock() to lock everything |
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185 | 185 | else under .hg/.''' |
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186 | 186 | |
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187 | 187 | # lock is symlink on platforms that support it, file on others. |
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188 | 188 | |
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189 | 189 | # symlink is used because create of directory entry and contents |
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190 | 190 | # are atomic even over nfs. |
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191 | 191 | |
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192 | 192 | # old-style lock: symlink to pid |
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193 | 193 | # new-style lock: symlink to hostname:pid |
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194 | 194 | |
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195 | 195 | _host = None |
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196 | 196 | |
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197 | 197 | def __init__( |
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198 | 198 | self, |
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199 | 199 | vfs, |
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200 | 200 | fname, |
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201 | 201 | timeout=-1, |
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202 | 202 | releasefn=None, |
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203 | 203 | acquirefn=None, |
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204 | 204 | desc=None, |
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205 | 205 | inheritchecker=None, |
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206 | 206 | parentlock=None, |
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207 | 207 | signalsafe=True, |
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208 | 208 | dolock=True, |
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209 | 209 | ): |
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210 | 210 | self.vfs = vfs |
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211 | 211 | self.f = fname |
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212 | 212 | self.held = 0 |
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213 | 213 | self.timeout = timeout |
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214 | 214 | self.releasefn = releasefn |
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215 | 215 | self.acquirefn = acquirefn |
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216 | 216 | self.desc = desc |
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217 | 217 | self._inheritchecker = inheritchecker |
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218 | 218 | self.parentlock = parentlock |
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219 | 219 | self._parentheld = False |
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220 | 220 | self._inherited = False |
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221 | 221 | if signalsafe: |
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222 | 222 | self._maybedelayedinterrupt = _delayedinterrupt |
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223 | 223 | else: |
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224 | 224 | self._maybedelayedinterrupt = util.nullcontextmanager |
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225 | 225 | self.postrelease = [] |
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226 | 226 | self.pid = self._getpid() |
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227 | 227 | if dolock: |
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228 | 228 | self.delay = self.lock() |
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229 | 229 | if self.acquirefn: |
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230 | 230 | self.acquirefn() |
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231 | 231 | |
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232 | 232 | def __enter__(self): |
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233 | 233 | return self |
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234 | 234 | |
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235 | 235 | def __exit__(self, exc_type, exc_value, exc_tb): |
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236 | 236 | self.release() |
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237 | 237 | |
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238 | 238 | def __del__(self): |
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239 | 239 | if self.held: |
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240 | 240 | warnings.warn( |
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241 | 241 | "use lock.release instead of del lock", |
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242 | 242 | category=DeprecationWarning, |
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243 | 243 | stacklevel=2, |
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244 | 244 | ) |
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245 | 245 | |
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246 | 246 | # ensure the lock will be removed |
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247 | 247 | # even if recursive locking did occur |
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248 | 248 | self.held = 1 |
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249 | 249 | |
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250 | 250 | self.release() |
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251 | 251 | |
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252 | 252 | def _getpid(self): |
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253 | 253 | # wrapper around procutil.getpid() to make testing easier |
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254 | 254 | return procutil.getpid() |
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255 | 255 | |
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256 | 256 | def lock(self): |
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257 | 257 | timeout = self.timeout |
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258 | 258 | while True: |
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259 | 259 | try: |
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260 | 260 | self._trylock() |
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261 | 261 | return self.timeout - timeout |
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262 | 262 | except error.LockHeld as inst: |
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263 | 263 | if timeout != 0: |
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264 | 264 | time.sleep(1) |
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265 | 265 | if timeout > 0: |
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266 | 266 | timeout -= 1 |
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267 | 267 | continue |
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268 | 268 | raise error.LockHeld( |
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269 | 269 | errno.ETIMEDOUT, inst.filename, self.desc, inst.locker |
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270 | 270 | ) |
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271 | 271 | |
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272 | 272 | def _trylock(self): |
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273 | 273 | if self.held: |
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274 | 274 | self.held += 1 |
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275 | 275 | return |
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276 | 276 | if lock._host is None: |
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277 | 277 | lock._host = _getlockprefix() |
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278 | 278 | lockname = b'%s:%d' % (lock._host, self.pid) |
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279 | 279 | retry = 5 |
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280 | 280 | while not self.held and retry: |
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281 | 281 | retry -= 1 |
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282 | 282 | try: |
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283 | 283 | with self._maybedelayedinterrupt(): |
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284 | 284 | self.vfs.makelock(lockname, self.f) |
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285 | 285 | self.held = 1 |
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286 | 286 | except (OSError, IOError) as why: |
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287 | 287 | if why.errno == errno.EEXIST: |
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288 | 288 | locker = self._readlock() |
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289 | 289 | if locker is None: |
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290 | 290 | continue |
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291 | 291 | |
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292 | 292 | # special case where a parent process holds the lock -- this |
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293 | 293 | # is different from the pid being different because we do |
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294 | 294 | # want the unlock and postrelease functions to be called, |
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295 | 295 | # but the lockfile to not be removed. |
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296 | 296 | if locker == self.parentlock: |
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297 | 297 | self._parentheld = True |
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298 | 298 | self.held = 1 |
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299 | 299 | return |
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300 | 300 | locker = self._testlock(locker) |
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301 | 301 | if locker is not None: |
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302 | 302 | raise error.LockHeld( |
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303 | 303 | errno.EAGAIN, |
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304 | 304 | self.vfs.join(self.f), |
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305 | 305 | self.desc, |
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306 | 306 | locker, |
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307 | 307 | ) |
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308 | 308 | else: |
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309 | 309 | raise error.LockUnavailable( |
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310 | 310 | why.errno, why.strerror, why.filename, self.desc |
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311 | 311 | ) |
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312 | 312 | |
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313 | 313 | if not self.held: |
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314 | 314 | # use empty locker to mean "busy for frequent lock/unlock |
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315 | 315 | # by many processes" |
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316 | 316 | raise error.LockHeld( |
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317 | 317 | errno.EAGAIN, self.vfs.join(self.f), self.desc, b"" |
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318 | 318 | ) |
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319 | 319 | |
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320 | 320 | def _readlock(self): |
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321 | 321 | """read lock and return its value |
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322 | 322 | |
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323 | 323 | Returns None if no lock exists, pid for old-style locks, and host:pid |
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324 | 324 | for new-style locks. |
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325 | 325 | """ |
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326 | 326 | try: |
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327 | 327 | return self.vfs.readlock(self.f) |
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328 | 328 | except (OSError, IOError) as why: |
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329 | 329 | if why.errno == errno.ENOENT: |
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330 | 330 | return None |
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331 | 331 | raise |
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332 | 332 | |
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333 |
def _ |
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333 | def _lockshouldbebroken(self, locker): | |
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334 | 334 | if locker is None: |
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335 |
return |
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|
335 | return False | |
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336 | 336 | try: |
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337 | 337 | host, pid = locker.split(b":", 1) |
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338 | 338 | except ValueError: |
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339 |
return |
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339 | return False | |
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340 | 340 | if host != lock._host: |
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341 |
return |
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|
341 | return False | |
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342 | 342 | try: |
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343 | 343 | pid = int(pid) |
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344 | 344 | except ValueError: |
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345 |
return |
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|
345 | return False | |
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346 | 346 | if procutil.testpid(pid): |
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347 | return False | |
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348 | return True | |
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349 | ||
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350 | def _testlock(self, locker): | |
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351 | if not self._lockshouldbebroken(locker): | |
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347 | 352 | return locker |
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353 | ||
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348 | 354 | # if locker dead, break lock. must do this with another lock |
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349 | 355 | # held, or can race and break valid lock. |
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350 | 356 | try: |
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351 |
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352 | self.vfs.unlink(self.f) | |
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353 | l.release() | |
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357 | with lock(self.vfs, self.f + b'.break', timeout=0): | |
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358 | self.vfs.unlink(self.f) | |
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354 | 359 | except error.LockError: |
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355 | 360 | return locker |
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356 | 361 | |
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357 | 362 | def testlock(self): |
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358 | 363 | """return id of locker if lock is valid, else None. |
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359 | 364 | |
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360 | 365 | If old-style lock, we cannot tell what machine locker is on. |
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361 | 366 | with new-style lock, if locker is on this machine, we can |
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362 | 367 | see if locker is alive. If locker is on this machine but |
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363 | 368 | not alive, we can safely break lock. |
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364 | 369 | |
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365 | 370 | The lock file is only deleted when None is returned. |
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366 | 371 | |
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367 | 372 | """ |
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368 | 373 | locker = self._readlock() |
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369 | 374 | return self._testlock(locker) |
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370 | 375 | |
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371 | 376 | @contextlib.contextmanager |
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372 | 377 | def inherit(self): |
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373 | 378 | """context for the lock to be inherited by a Mercurial subprocess. |
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374 | 379 | |
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375 | 380 | Yields a string that will be recognized by the lock in the subprocess. |
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376 | 381 | Communicating this string to the subprocess needs to be done separately |
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377 | 382 | -- typically by an environment variable. |
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378 | 383 | """ |
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379 | 384 | if not self.held: |
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380 | 385 | raise error.LockInheritanceContractViolation( |
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381 | 386 | b'inherit can only be called while lock is held' |
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382 | 387 | ) |
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383 | 388 | if self._inherited: |
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384 | 389 | raise error.LockInheritanceContractViolation( |
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385 | 390 | b'inherit cannot be called while lock is already inherited' |
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386 | 391 | ) |
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387 | 392 | if self._inheritchecker is not None: |
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388 | 393 | self._inheritchecker() |
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389 | 394 | if self.releasefn: |
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390 | 395 | self.releasefn() |
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391 | 396 | if self._parentheld: |
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392 | 397 | lockname = self.parentlock |
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393 | 398 | else: |
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394 | 399 | lockname = b'%s:%d' % (lock._host, self.pid) |
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395 | 400 | self._inherited = True |
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396 | 401 | try: |
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397 | 402 | yield lockname |
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398 | 403 | finally: |
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399 | 404 | if self.acquirefn: |
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400 | 405 | self.acquirefn() |
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401 | 406 | self._inherited = False |
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402 | 407 | |
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403 | 408 | def release(self): |
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404 | 409 | """release the lock and execute callback function if any |
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405 | 410 | |
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406 | 411 | If the lock has been acquired multiple times, the actual release is |
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407 | 412 | delayed to the last release call.""" |
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408 | 413 | if self.held > 1: |
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409 | 414 | self.held -= 1 |
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410 | 415 | elif self.held == 1: |
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411 | 416 | self.held = 0 |
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412 | 417 | if self._getpid() != self.pid: |
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413 | 418 | # we forked, and are not the parent |
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414 | 419 | return |
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415 | 420 | try: |
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416 | 421 | if self.releasefn: |
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417 | 422 | self.releasefn() |
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418 | 423 | finally: |
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419 | 424 | if not self._parentheld: |
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420 | 425 | try: |
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421 | 426 | self.vfs.unlink(self.f) |
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422 | 427 | except OSError: |
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423 | 428 | pass |
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424 | 429 | # The postrelease functions typically assume the lock is not held |
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425 | 430 | # at all. |
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426 | 431 | if not self._parentheld: |
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427 | 432 | for callback in self.postrelease: |
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428 | 433 | callback() |
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429 | 434 | # Prevent double usage and help clear cycles. |
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430 | 435 | self.postrelease = None |
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431 | 436 | |
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432 | 437 | |
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433 | 438 | def release(*locks): |
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434 | 439 | for lock in locks: |
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435 | 440 | if lock is not None: |
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436 | 441 | lock.release() |
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