Mercurial > hg
annotate mercurial/lock.py @ 6409:47f4a47161b4
merge with crew
author | Benoit Boissinot <benoit.boissinot@ens-lyon.org> |
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date | Sun, 30 Mar 2008 20:31:35 +0200 |
parents | 8933b8ea871a |
children | 7197812e8d44 |
rev | line source |
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161 | 1 # lock.py - simple locking scheme for mercurial |
2 # | |
2859 | 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 import errno, os, socket, time, util |
161 | 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): |
161 | 21 pass |
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 _host = None |
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33 |
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34 def __init__(self, file, timeout=-1, releasefn=None, desc=None): |
161 | 35 self.f = file |
36 self.held = 0 | |
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37 self.timeout = timeout |
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38 self.releasefn = releasefn |
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39 self.desc = desc |
161 | 40 self.lock() |
41 | |
42 def __del__(self): | |
43 self.release() | |
44 | |
45 def lock(self): | |
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46 timeout = self.timeout |
161 | 47 while 1: |
48 try: | |
49 self.trylock() | |
50 return 1 | |
51 except LockHeld, inst: | |
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52 if timeout != 0: |
161 | 53 time.sleep(1) |
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54 if timeout > 0: |
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55 timeout -= 1 |
161 | 56 continue |
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57 raise LockHeld(errno.ETIMEDOUT, inst.filename, self.desc, |
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58 inst.locker) |
515 | 59 |
161 | 60 def trylock(self): |
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61 if lock._host is None: |
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62 lock._host = socket.gethostname() |
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63 lockname = '%s:%s' % (lock._host, os.getpid()) |
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64 while not self.held: |
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65 try: |
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66 util.makelock(lockname, self.f) |
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67 self.held = 1 |
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68 except (OSError, IOError), why: |
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69 if why.errno == errno.EEXIST: |
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70 locker = self.testlock() |
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71 if locker is not None: |
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72 raise LockHeld(errno.EAGAIN, self.f, self.desc, |
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73 locker) |
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74 else: |
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75 raise LockUnavailable(why.errno, why.strerror, |
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76 why.filename, self.desc) |
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77 |
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78 def testlock(self): |
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79 """return id of locker if lock is valid, else None. |
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80 |
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81 If old-style lock, we cannot tell what machine locker is on. |
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82 with new-style lock, if locker is on this machine, we can |
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83 see if locker is alive. If locker is on this machine but |
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84 not alive, we can safely break lock. |
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85 |
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86 The lock file is only deleted when None is returned. |
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87 |
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88 """ |
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89 locker = util.readlock(self.f) |
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90 try: |
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91 host, pid = locker.split(":", 1) |
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92 except ValueError: |
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93 return locker |
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94 if host != lock._host: |
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95 return locker |
161 | 96 try: |
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97 pid = int(pid) |
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98 except: |
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99 return locker |
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100 if util.testpid(pid): |
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101 return locker |
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102 # if locker dead, break lock. must do this with another lock |
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103 # held, or can race and break valid lock. |
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104 try: |
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105 l = lock(self.f + '.break') |
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106 l.trylock() |
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107 os.unlink(self.f) |
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108 l.release() |
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109 except (LockHeld, LockUnavailable): |
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110 return locker |
161 | 111 |
112 def release(self): | |
113 if self.held: | |
114 self.held = 0 | |
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115 if self.releasefn: |
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116 self.releasefn() |
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117 try: |
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118 os.unlink(self.f) |
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119 except: pass |
161 | 120 |