Mercurial > hg > mercurial-crew-with-dirclash
annotate mercurial/lock.py @ 3216:5b7ed414affb
Add hg.LookupError
author | Brendan Cully <brendan@kublai.com> |
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date | Sun, 01 Oct 2006 11:58:55 -0700 |
parents | 345bac2bc4ec |
children | 4308f4cdc07b |
rev | line source |
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161 | 1 # lock.py - simple locking scheme for mercurial |
2 # | |
2858 | 3 # Copyright 2005, 2006 Matt Mackall <mpm@selenic.com> |
161 | 4 # |
5 # This software may be used and distributed according to the terms | |
6 # of the GNU General Public License, incorporated herein by reference. | |
7 | |
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8 from demandload import * |
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9 demandload(globals(), 'errno os socket time util') |
161 | 10 |
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11 class LockException(IOError): |
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12 def __init__(self, errno, strerror, filename, desc): |
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13 IOError.__init__(self, errno, strerror, filename) |
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14 self.desc = desc |
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15 |
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16 class LockHeld(LockException): |
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17 def __init__(self, errno, filename, desc, locker): |
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18 LockException.__init__(self, errno, 'Lock held', filename, desc) |
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19 self.locker = locker |
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20 |
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21 class LockUnavailable(LockException): |
161 | 22 pass |
23 | |
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24 class lock(object): |
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25 # lock is symlink on platforms that support it, file on others. |
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26 |
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27 # symlink is used because create of directory entry and contents |
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28 # are atomic even over nfs. |
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29 |
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30 # old-style lock: symlink to pid |
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31 # new-style lock: symlink to hostname:pid |
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32 |
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33 def __init__(self, file, timeout=-1, releasefn=None, desc=None): |
161 | 34 self.f = file |
35 self.held = 0 | |
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36 self.timeout = timeout |
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37 self.releasefn = releasefn |
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38 self.id = None |
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39 self.host = None |
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40 self.pid = None |
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41 self.desc = desc |
161 | 42 self.lock() |
43 | |
44 def __del__(self): | |
45 self.release() | |
46 | |
47 def lock(self): | |
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48 timeout = self.timeout |
161 | 49 while 1: |
50 try: | |
51 self.trylock() | |
52 return 1 | |
53 except LockHeld, inst: | |
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54 if timeout != 0: |
161 | 55 time.sleep(1) |
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56 if timeout > 0: |
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57 timeout -= 1 |
161 | 58 continue |
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59 raise LockHeld(errno.ETIMEDOUT, inst.filename, self.desc, |
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60 inst.locker) |
515 | 61 |
161 | 62 def trylock(self): |
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63 if self.id is None: |
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64 self.host = socket.gethostname() |
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65 self.pid = os.getpid() |
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66 self.id = '%s:%s' % (self.host, self.pid) |
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67 while not self.held: |
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68 try: |
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69 util.makelock(self.id, self.f) |
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70 self.held = 1 |
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71 except (OSError, IOError), why: |
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72 if why.errno == errno.EEXIST: |
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73 locker = self.testlock() |
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74 if locker: |
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75 raise LockHeld(errno.EAGAIN, self.f, self.desc, |
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76 locker) |
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77 else: |
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78 raise LockUnavailable(why.errno, why.strerror, |
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79 why.filename, self.desc) |
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80 |
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81 def testlock(self): |
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82 '''return id of locker if lock is valid, else None.''' |
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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 locker = util.readlock(self.f) |
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88 try: |
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89 host, pid = locker.split(":", 1) |
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90 except ValueError: |
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91 return locker |
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92 if host != self.host: |
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93 return locker |
161 | 94 try: |
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95 pid = int(pid) |
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96 except: |
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97 return locker |
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98 if util.testpid(pid): |
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99 return locker |
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100 # if locker dead, break lock. must do this with another lock |
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101 # held, or can race and break valid lock. |
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102 try: |
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103 l = lock(self.f + '.break') |
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104 l.trylock() |
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105 os.unlink(self.f) |
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106 l.release() |
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107 except (LockHeld, LockUnavailable): |
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108 return locker |
161 | 109 |
110 def release(self): | |
111 if self.held: | |
112 self.held = 0 | |
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113 if self.releasefn: |
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114 self.releasefn() |
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115 try: |
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116 os.unlink(self.f) |
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117 except: pass |
161 | 118 |