Mercurial > hg
annotate mercurial/lock.py @ 32078:bf5e13e38390 stable
pager: use less as a fallback on Unix
This seems reasonable choice per discussion, and the default-default of Git.
See also the inline-comment for why.
https://www.mercurial-scm.org/pipermail/mercurial-devel/2017-April/097042.html
author | Yuya Nishihara <yuya@tcha.org> |
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date | Fri, 28 Apr 2017 20:51:14 +0900 |
parents | 2e48c776a874 |
children | e1938d6051da |
rev | line source |
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1 # lock.py - simple advisory locking scheme for mercurial |
161 | 2 # |
2859 | 3 # Copyright 2005, 2006 Matt Mackall <mpm@selenic.com> |
161 | 4 # |
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5 # This software may be used and distributed according to the terms of the |
10263 | 6 # GNU General Public License version 2 or any later version. |
161 | 7 |
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8 from __future__ import absolute_import |
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9 |
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10 import contextlib |
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11 import errno |
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12 import os |
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13 import socket |
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14 import time |
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15 import warnings |
161 | 16 |
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17 from . import ( |
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18 encoding, |
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19 error, |
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20 pycompat, |
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21 util, |
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22 ) |
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23 |
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24 def _getlockprefix(): |
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25 """Return a string which is used to differentiate pid namespaces |
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26 |
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27 It's useful to detect "dead" processes and remove stale locks with |
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28 confidence. Typically it's just hostname. On modern linux, we include an |
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29 extra Linux-specific pid namespace identifier. |
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30 """ |
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31 result = socket.gethostname() |
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32 if pycompat.ispy3: |
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33 result = result.encode(pycompat.sysstr(encoding.encoding), 'replace') |
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34 if pycompat.sysplatform.startswith('linux'): |
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35 try: |
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36 result += '/%x' % os.stat('/proc/self/ns/pid').st_ino |
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37 except OSError as ex: |
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38 if ex.errno not in (errno.ENOENT, errno.EACCES, errno.ENOTDIR): |
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39 raise |
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40 return result |
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41 |
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42 class lock(object): |
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43 '''An advisory lock held by one process to control access to a set |
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44 of files. Non-cooperating processes or incorrectly written scripts |
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45 can ignore Mercurial's locking scheme and stomp all over the |
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46 repository, so don't do that. |
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47 |
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48 Typically used via localrepository.lock() to lock the repository |
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49 store (.hg/store/) or localrepository.wlock() to lock everything |
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50 else under .hg/.''' |
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51 |
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52 # lock is symlink on platforms that support it, file on others. |
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53 |
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54 # symlink is used because create of directory entry and contents |
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55 # are atomic even over nfs. |
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56 |
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57 # old-style lock: symlink to pid |
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58 # new-style lock: symlink to hostname:pid |
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59 |
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60 _host = None |
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61 |
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62 def __init__(self, vfs, file, timeout=-1, releasefn=None, acquirefn=None, |
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63 desc=None, inheritchecker=None, parentlock=None): |
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64 self.vfs = vfs |
161 | 65 self.f = file |
66 self.held = 0 | |
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67 self.timeout = timeout |
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68 self.releasefn = releasefn |
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69 self.acquirefn = acquirefn |
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70 self.desc = desc |
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71 self._inheritchecker = inheritchecker |
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72 self.parentlock = parentlock |
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73 self._parentheld = False |
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74 self._inherited = False |
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75 self.postrelease = [] |
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76 self.pid = self._getpid() |
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77 self.delay = self.lock() |
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78 if self.acquirefn: |
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79 self.acquirefn() |
161 | 80 |
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81 def __enter__(self): |
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82 return self |
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83 |
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84 def __exit__(self, exc_type, exc_value, exc_tb): |
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85 self.release() |
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86 |
161 | 87 def __del__(self): |
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88 if self.held: |
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89 warnings.warn("use lock.release instead of del lock", |
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90 category=DeprecationWarning, |
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91 stacklevel=2) |
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92 |
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93 # ensure the lock will be removed |
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94 # even if recursive locking did occur |
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95 self.held = 1 |
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96 |
161 | 97 self.release() |
98 | |
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99 def _getpid(self): |
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100 # wrapper around util.getpid() to make testing easier |
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101 return util.getpid() |
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102 |
161 | 103 def lock(self): |
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104 timeout = self.timeout |
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105 while True: |
161 | 106 try: |
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107 self._trylock() |
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108 return self.timeout - timeout |
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109 except error.LockHeld as inst: |
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110 if timeout != 0: |
161 | 111 time.sleep(1) |
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112 if timeout > 0: |
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113 timeout -= 1 |
161 | 114 continue |
7640 | 115 raise error.LockHeld(errno.ETIMEDOUT, inst.filename, self.desc, |
116 inst.locker) | |
515 | 117 |
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118 def _trylock(self): |
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119 if self.held: |
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120 self.held += 1 |
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121 return |
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122 if lock._host is None: |
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123 lock._host = _getlockprefix() |
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124 lockname = '%s:%d' % (lock._host, self.pid) |
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125 retry = 5 |
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126 while not self.held and retry: |
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127 retry -= 1 |
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128 try: |
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129 self.vfs.makelock(lockname, self.f) |
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130 self.held = 1 |
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131 except (OSError, IOError) as why: |
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132 if why.errno == errno.EEXIST: |
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133 locker = self._readlock() |
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134 # special case where a parent process holds the lock -- this |
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135 # is different from the pid being different because we do |
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136 # want the unlock and postrelease functions to be called, |
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137 # but the lockfile to not be removed. |
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138 if locker == self.parentlock: |
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139 self._parentheld = True |
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140 self.held = 1 |
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141 return |
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142 locker = self._testlock(locker) |
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143 if locker is not None: |
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144 raise error.LockHeld(errno.EAGAIN, |
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145 self.vfs.join(self.f), self.desc, |
7640 | 146 locker) |
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147 else: |
7640 | 148 raise error.LockUnavailable(why.errno, why.strerror, |
149 why.filename, self.desc) | |
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150 |
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151 def _readlock(self): |
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152 """read lock and return its value |
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153 |
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154 Returns None if no lock exists, pid for old-style locks, and host:pid |
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155 for new-style locks. |
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156 """ |
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157 try: |
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158 return self.vfs.readlock(self.f) |
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159 except (OSError, IOError) as why: |
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160 if why.errno == errno.ENOENT: |
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161 return None |
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162 raise |
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163 |
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164 def _testlock(self, locker): |
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165 if locker is None: |
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166 return None |
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167 try: |
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168 host, pid = locker.split(":", 1) |
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169 except ValueError: |
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170 return locker |
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171 if host != lock._host: |
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172 return locker |
161 | 173 try: |
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174 pid = int(pid) |
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175 except ValueError: |
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176 return locker |
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177 if util.testpid(pid): |
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178 return locker |
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179 # if locker dead, break lock. must do this with another lock |
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180 # held, or can race and break valid lock. |
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181 try: |
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182 l = lock(self.vfs, self.f + '.break', timeout=0) |
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183 self.vfs.unlink(self.f) |
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184 l.release() |
7640 | 185 except error.LockError: |
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186 return locker |
161 | 187 |
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188 def testlock(self): |
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189 """return id of locker if lock is valid, else None. |
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190 |
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191 If old-style lock, we cannot tell what machine locker is on. |
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192 with new-style lock, if locker is on this machine, we can |
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193 see if locker is alive. If locker is on this machine but |
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194 not alive, we can safely break lock. |
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195 |
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196 The lock file is only deleted when None is returned. |
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197 |
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198 """ |
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199 locker = self._readlock() |
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200 return self._testlock(locker) |
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201 |
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202 @contextlib.contextmanager |
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203 def inherit(self): |
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204 """context for the lock to be inherited by a Mercurial subprocess. |
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205 |
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206 Yields a string that will be recognized by the lock in the subprocess. |
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207 Communicating this string to the subprocess needs to be done separately |
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208 -- typically by an environment variable. |
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209 """ |
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210 if not self.held: |
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211 raise error.LockInheritanceContractViolation( |
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212 'inherit can only be called while lock is held') |
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213 if self._inherited: |
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214 raise error.LockInheritanceContractViolation( |
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215 'inherit cannot be called while lock is already inherited') |
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216 if self._inheritchecker is not None: |
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217 self._inheritchecker() |
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218 if self.releasefn: |
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219 self.releasefn() |
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220 if self._parentheld: |
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221 lockname = self.parentlock |
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222 else: |
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223 lockname = '%s:%s' % (lock._host, self.pid) |
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224 self._inherited = True |
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225 try: |
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226 yield lockname |
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227 finally: |
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228 if self.acquirefn: |
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229 self.acquirefn() |
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230 self._inherited = False |
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231 |
161 | 232 def release(self): |
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233 """release the lock and execute callback function if any |
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234 |
17537 | 235 If the lock has been acquired multiple times, the actual release is |
17510 | 236 delayed to the last release call.""" |
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237 if self.held > 1: |
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238 self.held -= 1 |
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239 elif self.held == 1: |
161 | 240 self.held = 0 |
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241 if self._getpid() != self.pid: |
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242 # we forked, and are not the parent |
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243 return |
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Fix troubles with clone and exception handling
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244 try: |
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245 if self.releasefn: |
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246 self.releasefn() |
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247 finally: |
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248 if not self._parentheld: |
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249 try: |
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250 self.vfs.unlink(self.f) |
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251 except OSError: |
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252 pass |
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253 # The postrelease functions typically assume the lock is not held |
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254 # at all. |
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255 if not self._parentheld: |
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256 for callback in self.postrelease: |
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257 callback() |
28959
518c3e392f75
lock: clear postrelease hooks list after usage
Gregory Szorc <gregory.szorc@gmail.com>
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258 # Prevent double usage and help clear cycles. |
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259 self.postrelease = None |
161 | 260 |
8108
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made repo locks recursive and deprecate refcounting based lock releasing
Ronny Pfannschmidt <Ronny.Pfannschmidt@gmx.de>
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261 def release(*locks): |
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262 for lock in locks: |
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263 if lock is not None: |
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264 lock.release() |