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annotate mercurial/lock.py @ 26359:c545d51c901e

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lock.release: do not unlink inherited locks This is part of a series that will allow locks to be inherited by subprocesses in limited circumstances. A subprocess unlinking a lock will lead to potential corruption from other concurrent processes.
author Siddharth Agarwal <sid0@fb.com>
date Thu, 24 Sep 2015 16:03:26 -0700
parents de5a52e5eb9e
children 0fceb34806e1
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
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1 # lock.py - simple advisory locking scheme for mercurial
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2 #
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3 # Copyright 2005, 2006 Matt Mackall <mpm@selenic.com>
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4 #
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5 # This software may be used and distributed according to the terms of the
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6 # GNU General Public License version 2 or any later version.
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7
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8 from __future__ import absolute_import
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9
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10 import errno
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11 import os
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12 import socket
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13 import time
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14 import warnings
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15
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16 from . import (
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17 error,
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18 util,
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19 )
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20
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21 class lock(object):
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22 '''An advisory lock held by one process to control access to a set
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23 of files. Non-cooperating processes or incorrectly written scripts
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24 can ignore Mercurial's locking scheme and stomp all over the
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25 repository, so don't do that.
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26
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27 Typically used via localrepository.lock() to lock the repository
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28 store (.hg/store/) or localrepository.wlock() to lock everything
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29 else under .hg/.'''
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30
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31 # lock is symlink on platforms that support it, file on others.
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32
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33 # symlink is used because create of directory entry and contents
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34 # are atomic even over nfs.
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35
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36 # old-style lock: symlink to pid
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37 # new-style lock: symlink to hostname:pid
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38
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39 _host = None
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40
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41 def __init__(self, vfs, file, timeout=-1, releasefn=None, acquirefn=None,
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42 desc=None, parentlock=None):
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43 self.vfs = vfs
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44 self.f = file
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45 self.held = 0
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46 self.timeout = timeout
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47 self.releasefn = releasefn
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48 self.acquirefn = acquirefn
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49 self.desc = desc
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50 self.parentlock = parentlock
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51 self._parentheld = False
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52 self._inherited = False
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53 self.postrelease = []
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54 self.pid = os.getpid()
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55 self.delay = self.lock()
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56 if self.acquirefn:
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57 self.acquirefn()
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58
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59 def __del__(self):
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60 if self.held:
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61 warnings.warn("use lock.release instead of del lock",
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62 category=DeprecationWarning,
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63 stacklevel=2)
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64
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65 # ensure the lock will be removed
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66 # even if recursive locking did occur
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67 self.held = 1
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68
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69 self.release()
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70
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71 def lock(self):
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72 timeout = self.timeout
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73 while True:
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74 try:
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75 self._trylock()
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76 return self.timeout - timeout
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77 except error.LockHeld as inst:
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78 if timeout != 0:
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79 time.sleep(1)
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80 if timeout > 0:
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81 timeout -= 1
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82 continue
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83 raise error.LockHeld(errno.ETIMEDOUT, inst.filename, self.desc,
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84 inst.locker)
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85
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86 def _trylock(self):
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87 if self.held:
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88 self.held += 1
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89 return
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90 if lock._host is None:
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91 lock._host = socket.gethostname()
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92 lockname = '%s:%s' % (lock._host, self.pid)
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93 retry = 5
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94 while not self.held and retry:
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95 retry -= 1
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96 try:
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97 self.vfs.makelock(lockname, self.f)
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98 self.held = 1
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99 except (OSError, IOError) as why:
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100 if why.errno == errno.EEXIST:
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101 locker = self.testlock()
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102 if locker is not None:
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103 raise error.LockHeld(errno.EAGAIN,
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104 self.vfs.join(self.f), self.desc,
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105 locker)
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106 else:
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107 raise error.LockUnavailable(why.errno, why.strerror,
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108 why.filename, self.desc)
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109
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110 def _readlock(self):
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111 """read lock and return its value
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112
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113 Returns None if no lock exists, pid for old-style locks, and host:pid
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114 for new-style locks.
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115 """
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116 try:
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117 return self.vfs.readlock(self.f)
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118 except (OSError, IOError) as why:
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119 if why.errno == errno.ENOENT:
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120 return None
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121 raise
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122
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123 def _testlock(self, locker):
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124 if locker is None:
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125 return None
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126 try:
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127 host, pid = locker.split(":", 1)
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128 except ValueError:
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129 return locker
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130 if host != lock._host:
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131 return locker
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132 try:
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133 pid = int(pid)
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134 except ValueError:
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135 return locker
d314a89fa4f1 change lock format to let us detect and break stale locks.
Vadim Gelfer <vadim.gelfer@gmail.com>
parents: 1836
diff changeset
136 if util.testpid(pid):
d314a89fa4f1 change lock format to let us detect and break stale locks.
Vadim Gelfer <vadim.gelfer@gmail.com>
parents: 1836
diff changeset
137 return locker
d314a89fa4f1 change lock format to let us detect and break stale locks.
Vadim Gelfer <vadim.gelfer@gmail.com>
parents: 1836
diff changeset
138 # if locker dead, break lock. must do this with another lock
d314a89fa4f1 change lock format to let us detect and break stale locks.
Vadim Gelfer <vadim.gelfer@gmail.com>
parents: 1836
diff changeset
139 # held, or can race and break valid lock.
d314a89fa4f1 change lock format to let us detect and break stale locks.
Vadim Gelfer <vadim.gelfer@gmail.com>
parents: 1836
diff changeset
140 try:
20091
abfe6a8e619b lock: take both vfs and lock file path relative to vfs to access via vfs
FUJIWARA Katsunori <foozy@lares.dti.ne.jp>
parents: 19927
diff changeset
141 l = lock(self.vfs, self.f + '.break', timeout=0)
abfe6a8e619b lock: take both vfs and lock file path relative to vfs to access via vfs
FUJIWARA Katsunori <foozy@lares.dti.ne.jp>
parents: 19927
diff changeset
142 self.vfs.unlink(self.f)
1877
d314a89fa4f1 change lock format to let us detect and break stale locks.
Vadim Gelfer <vadim.gelfer@gmail.com>
parents: 1836
diff changeset
143 l.release()
7640
7197812e8d44 error: move lock errors
Matt Mackall <mpm@selenic.com>
parents: 4959
diff changeset
144 except error.LockError:
1877
d314a89fa4f1 change lock format to let us detect and break stale locks.
Vadim Gelfer <vadim.gelfer@gmail.com>
parents: 1836
diff changeset
145 return locker
161
0b4c5cb953d9 Simply repository locking
mpm@selenic.com
parents:
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146
26291
1d33842c5b3e lock: factor out lock testing into a separate function
Siddharth Agarwal <sid0@fb.com>
parents: 26290
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147 def testlock(self):
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Siddharth Agarwal <sid0@fb.com>
parents: 26290
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148 """return id of locker if lock is valid, else None.
1d33842c5b3e lock: factor out lock testing into a separate function
Siddharth Agarwal <sid0@fb.com>
parents: 26290
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149
1d33842c5b3e lock: factor out lock testing into a separate function
Siddharth Agarwal <sid0@fb.com>
parents: 26290
diff changeset
150 If old-style lock, we cannot tell what machine locker is on.
1d33842c5b3e lock: factor out lock testing into a separate function
Siddharth Agarwal <sid0@fb.com>
parents: 26290
diff changeset
151 with new-style lock, if locker is on this machine, we can
1d33842c5b3e lock: factor out lock testing into a separate function
Siddharth Agarwal <sid0@fb.com>
parents: 26290
diff changeset
152 see if locker is alive. If locker is on this machine but
1d33842c5b3e lock: factor out lock testing into a separate function
Siddharth Agarwal <sid0@fb.com>
parents: 26290
diff changeset
153 not alive, we can safely break lock.
1d33842c5b3e lock: factor out lock testing into a separate function
Siddharth Agarwal <sid0@fb.com>
parents: 26290
diff changeset
154
1d33842c5b3e lock: factor out lock testing into a separate function
Siddharth Agarwal <sid0@fb.com>
parents: 26290
diff changeset
155 The lock file is only deleted when None is returned.
1d33842c5b3e lock: factor out lock testing into a separate function
Siddharth Agarwal <sid0@fb.com>
parents: 26290
diff changeset
156
1d33842c5b3e lock: factor out lock testing into a separate function
Siddharth Agarwal <sid0@fb.com>
parents: 26290
diff changeset
157 """
1d33842c5b3e lock: factor out lock testing into a separate function
Siddharth Agarwal <sid0@fb.com>
parents: 26290
diff changeset
158 locker = self._readlock()
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Siddharth Agarwal <sid0@fb.com>
parents: 26290
diff changeset
159 return self._testlock(locker)
1d33842c5b3e lock: factor out lock testing into a separate function
Siddharth Agarwal <sid0@fb.com>
parents: 26290
diff changeset
160
26357
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
161 def prepinherit(self):
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
162 """prepare for the lock to be inherited by a Mercurial subprocess
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
163
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
164 Returns a string that will be recognized by the lock in the
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
165 subprocess. Communicating this string to the subprocess needs to be done
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
166 separately -- typically by an environment variable.
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
167 """
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
168 if not self.held:
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
169 raise error.LockInheritanceContractViolation(
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
170 'prepinherit can only be called while lock is held')
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
171 if self._inherited:
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
172 raise error.LockInheritanceContractViolation(
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
173 'prepinherit cannot be called while lock is already inherited')
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
174 if self.releasefn:
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
175 self.releasefn()
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
176 if self._parentheld:
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
177 lockname = self.parentlock
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
178 else:
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
179 lockname = '%s:%s' % (lock._host, self.pid)
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
180 self._inherited = True
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
181 return lockname
6979a1369185 lock: add a method to prepare the lock for inheritance
Siddharth Agarwal <sid0@fb.com>
parents: 26356
diff changeset
182
26358
de5a52e5eb9e lock: add a method to reacquire the lock after subprocesses exit
Siddharth Agarwal <sid0@fb.com>
parents: 26357
diff changeset
183 def reacquire(self):
de5a52e5eb9e lock: add a method to reacquire the lock after subprocesses exit
Siddharth Agarwal <sid0@fb.com>
parents: 26357
diff changeset
184 if not self._inherited:
de5a52e5eb9e lock: add a method to reacquire the lock after subprocesses exit
Siddharth Agarwal <sid0@fb.com>
parents: 26357
diff changeset
185 raise error.LockInheritanceContractViolation(
de5a52e5eb9e lock: add a method to reacquire the lock after subprocesses exit
Siddharth Agarwal <sid0@fb.com>
parents: 26357
diff changeset
186 'reacquire can only be called after prepinherit')
de5a52e5eb9e lock: add a method to reacquire the lock after subprocesses exit
Siddharth Agarwal <sid0@fb.com>
parents: 26357
diff changeset
187 if self.acquirefn:
de5a52e5eb9e lock: add a method to reacquire the lock after subprocesses exit
Siddharth Agarwal <sid0@fb.com>
parents: 26357
diff changeset
188 self.acquirefn()
de5a52e5eb9e lock: add a method to reacquire the lock after subprocesses exit
Siddharth Agarwal <sid0@fb.com>
parents: 26357
diff changeset
189 self._inherited = False
de5a52e5eb9e lock: add a method to reacquire the lock after subprocesses exit
Siddharth Agarwal <sid0@fb.com>
parents: 26357
diff changeset
190
161
0b4c5cb953d9 Simply repository locking
mpm@selenic.com
parents:
diff changeset
191 def release(self):
15583
926a06f7a353 lock: add mechanism to register post release callback
Pierre-Yves David <pierre-yves.david@ens-lyon.org>
parents: 14494
diff changeset
192 """release the lock and execute callback function if any
926a06f7a353 lock: add mechanism to register post release callback
Pierre-Yves David <pierre-yves.david@ens-lyon.org>
parents: 14494
diff changeset
193
17537
31f32a96e1e3 Merge spelling fixes
Bryan O'Sullivan <bryano@fb.com>
parents: 17427 17510
diff changeset
194 If the lock has been acquired multiple times, the actual release is
17510
7c44b703657b spelling: release
timeless@mozdev.org
parents: 15589
diff changeset
195 delayed to the last release call."""
8108
a26d33749bd8 made repo locks recursive and deprecate refcounting based lock releasing
Ronny Pfannschmidt <Ronny.Pfannschmidt@gmx.de>
parents: 7640
diff changeset
196 if self.held > 1:
a26d33749bd8 made repo locks recursive and deprecate refcounting based lock releasing
Ronny Pfannschmidt <Ronny.Pfannschmidt@gmx.de>
parents: 7640
diff changeset
197 self.held -= 1
9680
8cea86d73887 lock: use '==' instead of 'is' for integer equality ('is' may not work)
Benoit Boissinot <benoit.boissinot@ens-lyon.org>
parents: 9309
diff changeset
198 elif self.held == 1:
161
0b4c5cb953d9 Simply repository locking
mpm@selenic.com
parents:
diff changeset
199 self.held = 0
18907
af9fa8d4c939 lock: if we fork, ensure that only the parent releases
Bryan O'Sullivan <bryano@fb.com>
parents: 17683
diff changeset
200 if os.getpid() != self.pid:
af9fa8d4c939 lock: if we fork, ensure that only the parent releases
Bryan O'Sullivan <bryano@fb.com>
parents: 17683
diff changeset
201 # we forked, and are not the parent
af9fa8d4c939 lock: if we fork, ensure that only the parent releases
Bryan O'Sullivan <bryano@fb.com>
parents: 17683
diff changeset
202 return
503
c6a2e41c8c60 Fix troubles with clone and exception handling
mpm@selenic.com
parents: 429
diff changeset
203 try:
23032
f484be02bd35 lock: while releasing, unlink lockfile even if the release function throws
Siddharth Agarwal <sid0@fb.com>
parents: 20380
diff changeset
204 if self.releasefn:
f484be02bd35 lock: while releasing, unlink lockfile even if the release function throws
Siddharth Agarwal <sid0@fb.com>
parents: 20380
diff changeset
205 self.releasefn()
f484be02bd35 lock: while releasing, unlink lockfile even if the release function throws
Siddharth Agarwal <sid0@fb.com>
parents: 20380
diff changeset
206 finally:
26359
c545d51c901e lock.release: do not unlink inherited locks
Siddharth Agarwal <sid0@fb.com>
parents: 26358
diff changeset
207 if not self._parentheld:
c545d51c901e lock.release: do not unlink inherited locks
Siddharth Agarwal <sid0@fb.com>
parents: 26358
diff changeset
208 try:
c545d51c901e lock.release: do not unlink inherited locks
Siddharth Agarwal <sid0@fb.com>
parents: 26358
diff changeset
209 self.vfs.unlink(self.f)
c545d51c901e lock.release: do not unlink inherited locks
Siddharth Agarwal <sid0@fb.com>
parents: 26358
diff changeset
210 except OSError:
c545d51c901e lock.release: do not unlink inherited locks
Siddharth Agarwal <sid0@fb.com>
parents: 26358
diff changeset
211 pass
15589
cc24e4ed3e0c lock: change name of release chain
Matt Mackall <mpm@selenic.com>
parents: 15583
diff changeset
212 for callback in self.postrelease:
15583
926a06f7a353 lock: add mechanism to register post release callback
Pierre-Yves David <pierre-yves.david@ens-lyon.org>
parents: 14494
diff changeset
213 callback()
161
0b4c5cb953d9 Simply repository locking
mpm@selenic.com
parents:
diff changeset
214
8108
a26d33749bd8 made repo locks recursive and deprecate refcounting based lock releasing
Ronny Pfannschmidt <Ronny.Pfannschmidt@gmx.de>
parents: 7640
diff changeset
215 def release(*locks):
a26d33749bd8 made repo locks recursive and deprecate refcounting based lock releasing
Ronny Pfannschmidt <Ronny.Pfannschmidt@gmx.de>
parents: 7640
diff changeset
216 for lock in locks:
a26d33749bd8 made repo locks recursive and deprecate refcounting based lock releasing
Ronny Pfannschmidt <Ronny.Pfannschmidt@gmx.de>
parents: 7640
diff changeset
217 if lock is not None:
a26d33749bd8 made repo locks recursive and deprecate refcounting based lock releasing
Ronny Pfannschmidt <Ronny.Pfannschmidt@gmx.de>
parents: 7640
diff changeset
218 lock.release()