Mercurial > public > mercurial-scm > hg-stable

annotate mercurial/lock.py @ 8110:b616f328af9f

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switch dircleanup in mercurial.hg.clone from gc based to explicit
author Ronny Pfannschmidt <Ronny.Pfannschmidt@gmx.de>
date Wed, 22 Apr 2009 02:01:22 +0200
parents a26d33749bd8
children 87a1605979e4
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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, error
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9
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10 class lock(object):
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11 # lock is symlink on platforms that support it, file on others.
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12
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13 # symlink is used because create of directory entry and contents
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14 # are atomic even over nfs.
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15
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16 # old-style lock: symlink to pid
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17 # new-style lock: symlink to hostname:pid
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18
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19 _host = None
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20
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21 def __init__(self, file, timeout=-1, releasefn=None, desc=None):
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22 self.f = file
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23 self.held = 0
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24 self.timeout = timeout
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25 self.releasefn = releasefn
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26 self.desc = desc
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27 self.lock()
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28
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29 def __del__(self):
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30 if self.held:
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31 # ensure the lock will be removed
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32 # even if recursive locking did occur
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33 self.held = 1
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34
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35 self.release()
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36
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37 def lock(self):
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38 timeout = self.timeout
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39 while 1:
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40 try:
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41 self.trylock()
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42 return 1
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43 except error.LockHeld, inst:
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44 if timeout != 0:
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45 time.sleep(1)
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46 if timeout > 0:
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47 timeout -= 1
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48 continue
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49 raise error.LockHeld(errno.ETIMEDOUT, inst.filename, self.desc,
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50 inst.locker)
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51
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52 def trylock(self):
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53 if self.held:
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54 self.held += 1
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55 return
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56 if lock._host is None:
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57 lock._host = socket.gethostname()
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58 lockname = '%s:%s' % (lock._host, os.getpid())
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59 while not self.held:
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60 try:
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61 util.makelock(lockname, self.f)
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62 self.held = 1
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63 except (OSError, IOError), why:
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64 if why.errno == errno.EEXIST:
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65 locker = self.testlock()
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66 if locker is not None:
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67 raise error.LockHeld(errno.EAGAIN, self.f, self.desc,
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68 locker)
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69 else:
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70 raise error.LockUnavailable(why.errno, why.strerror,
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71 why.filename, self.desc)
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72
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73 def testlock(self):
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74 """return id of locker if lock is valid, else None.
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75
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76 If old-style lock, we cannot tell what machine locker is on.
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77 with new-style lock, if locker is on this machine, we can
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78 see if locker is alive. If locker is on this machine but
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79 not alive, we can safely break lock.
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80
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81 The lock file is only deleted when None is returned.
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82
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83 """
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84 locker = util.readlock(self.f)
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85 try:
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86 host, pid = locker.split(":", 1)
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87 except ValueError:
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88 return locker
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89 if host != lock._host:
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90 return locker
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91 try:
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92 pid = int(pid)
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93 except:
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94 return locker
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95 if util.testpid(pid):
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96 return locker
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97 # if locker dead, break lock. must do this with another lock
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98 # held, or can race and break valid lock.
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99 try:
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100 l = lock(self.f + '.break')
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101 l.trylock()
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102 os.unlink(self.f)
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103 l.release()
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104 except error.LockError:
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105 return locker
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106
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107 def release(self):
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108 if self.held > 1:
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109 self.held -= 1
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110 elif self.held is 1:
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111 self.held = 0
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112 if self.releasefn:
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113 self.releasefn()
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114 try:
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115 os.unlink(self.f)
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116 except: pass
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117
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118 def release(*locks):
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119 for lock in locks:
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120 if lock is not None:
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121 lock.release()
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122