Mercurial > hg > mercurial-crew-with-dirclash

annotate mercurial/lock.py @ 5340:ad8783fe20f7

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darcs2hg: Now detects and recovers from simple darcs conflicts.
author Terry Smith <terry@t11e.com>
date Tue, 11 Sep 2007 13:13:54 -0400
parents abaee83ce0a6
children 3e25a6eb5c9a
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1 # lock.py - simple 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
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6 # of the GNU General Public License, incorporated herein by reference.
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7
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8 import errno, os, socket, time, util
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9
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10 class LockException(IOError):
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11 def __init__(self, errno, strerror, filename, desc):
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12 IOError.__init__(self, errno, strerror, filename)
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13 self.desc = desc
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14
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15 class LockHeld(LockException):
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16 def __init__(self, errno, filename, desc, locker):
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17 LockException.__init__(self, errno, 'Lock held', filename, desc)
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18 self.locker = locker
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19
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20 class LockUnavailable(LockException):
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21 pass
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22
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23 class lock(object):
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24 # lock is symlink on platforms that support it, file on others.
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25
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26 # symlink is used because create of directory entry and contents
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27 # are atomic even over nfs.
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28
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29 # old-style lock: symlink to pid
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30 # new-style lock: symlink to hostname:pid
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31
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32 def __init__(self, file, timeout=-1, releasefn=None, desc=None):
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33 self.f = file
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34 self.held = 0
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35 self.timeout = timeout
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36 self.releasefn = releasefn
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37 self.id = None
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38 self.host = None
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39 self.pid = None
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40 self.desc = desc
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41 self.lock()
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42
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43 def __del__(self):
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44 self.release()
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45
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46 def lock(self):
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47 timeout = self.timeout
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48 while 1:
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49 try:
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50 self.trylock()
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51 return 1
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52 except LockHeld, inst:
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53 if timeout != 0:
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54 time.sleep(1)
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55 if timeout > 0:
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56 timeout -= 1
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57 continue
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58 raise LockHeld(errno.ETIMEDOUT, inst.filename, self.desc,
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59 inst.locker)
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60
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61 def trylock(self):
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62 if self.id is None:
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63 self.host = socket.gethostname()
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64 self.pid = os.getpid()
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65 self.id = '%s:%s' % (self.host, self.pid)
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66 while not self.held:
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67 try:
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68 util.makelock(self.id, self.f)
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69 self.held = 1
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70 except (OSError, IOError), why:
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71 if why.errno == errno.EEXIST:
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72 locker = self.testlock()
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73 if locker is not None:
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74 raise LockHeld(errno.EAGAIN, self.f, self.desc,
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75 locker)
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76 else:
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77 raise LockUnavailable(why.errno, why.strerror,
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78 why.filename, self.desc)
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79
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80 def testlock(self):
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81 """return id of locker if lock is valid, else None.
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82
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83 If old-style lock, we cannot tell what machine locker is on.
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84 with new-style lock, if locker is on this machine, we can
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85 see if locker is alive. If locker is on this machine but
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86 not alive, we can safely break lock.
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87
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88 The lock file is only deleted when None is returned.
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89
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90 """
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91 locker = util.readlock(self.f)
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92 try:
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93 host, pid = locker.split(":", 1)
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94 except ValueError:
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95 return locker
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96 if host != self.host:
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97 return locker
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98 try:
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99 pid = int(pid)
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100 except:
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101 return locker
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102 if util.testpid(pid):
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103 return locker
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104 # if locker dead, break lock. must do this with another lock
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105 # held, or can race and break valid lock.
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106 try:
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107 l = lock(self.f + '.break')
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108 l.trylock()
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109 os.unlink(self.f)
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110 l.release()
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111 except (LockHeld, LockUnavailable):
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112 return locker
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113
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114 def release(self):
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115 if self.held:
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116 self.held = 0
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117 if self.releasefn:
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118 self.releasefn()
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119 try:
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120 os.unlink(self.f)
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121 except: pass
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122