Mercurial > hg > mercurial-crew-with-dirclash
annotate mercurial/lock.py @ 1952:f4df34b6987f
tests: fix portability issue for echo -n
author | TK Soh <teekaysoh@yahoo.com> |
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date | Tue, 14 Mar 2006 21:42:32 -0800 |
parents | d314a89fa4f1 |
children | ff5c9a92f556 |
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161 | 1 # lock.py - simple locking scheme for mercurial |
2 # | |
3 # Copyright 2005 Matt Mackall <mpm@selenic.com> | |
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(Exception): |
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12 pass |
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13 class LockHeld(LockException): |
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14 pass |
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15 class LockUnavailable(LockException): |
161 | 16 pass |
17 | |
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18 class lock(object): |
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19 # lock is symlink on platforms that support it, file on others. |
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20 |
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21 # symlink is used because create of directory entry and contents |
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22 # are atomic even over nfs. |
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23 |
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24 # old-style lock: symlink to pid |
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25 # new-style lock: symlink to hostname:pid |
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26 |
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27 def __init__(self, file, timeout=-1, releasefn=None): |
161 | 28 self.f = file |
29 self.held = 0 | |
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30 self.timeout = timeout |
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31 self.releasefn = releasefn |
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32 self.id = None |
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33 self.host = None |
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34 self.pid = None |
161 | 35 self.lock() |
36 | |
37 def __del__(self): | |
38 self.release() | |
39 | |
40 def lock(self): | |
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41 timeout = self.timeout |
161 | 42 while 1: |
43 try: | |
44 self.trylock() | |
45 return 1 | |
46 except LockHeld, inst: | |
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47 if timeout != 0: |
161 | 48 time.sleep(1) |
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49 if timeout > 0: |
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50 timeout -= 1 |
161 | 51 continue |
52 raise inst | |
515 | 53 |
161 | 54 def trylock(self): |
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55 if self.id is None: |
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56 self.host = socket.gethostname() |
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57 self.pid = os.getpid() |
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58 self.id = '%s:%s' % (self.host, self.pid) |
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59 while not self.held: |
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60 try: |
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61 util.makelock(self.id, 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: |
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67 raise LockHeld(locker) |
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68 else: |
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69 raise LockUnavailable(why) |
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70 |
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71 def testlock(self): |
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72 '''return id of locker if lock is valid, else None.''' |
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73 # if old-style lock, we cannot tell what machine locker is on. |
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74 # with new-style lock, if locker is on this machine, we can |
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75 # see if locker is alive. if locker is on this machine but |
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76 # not alive, we can safely break lock. |
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77 locker = util.readlock(self.f) |
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78 c = locker.find(':') |
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79 if c == -1: |
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80 return locker |
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81 host = locker[:c] |
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82 if host != self.host: |
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83 return locker |
161 | 84 try: |
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85 pid = int(locker[c+1:]) |
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86 except: |
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87 return locker |
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88 if util.testpid(pid): |
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89 return locker |
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90 # if locker dead, break lock. must do this with another lock |
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91 # held, or can race and break valid lock. |
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92 try: |
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93 l = lock(self.f + '.break') |
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94 l.trylock() |
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95 os.unlink(self.f) |
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96 l.release() |
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97 except (LockHeld, LockUnavailable): |
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98 return locker |
161 | 99 |
100 def release(self): | |
101 if self.held: | |
102 self.held = 0 | |
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103 if self.releasefn: |
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104 self.releasefn() |
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105 try: |
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106 os.unlink(self.f) |
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107 except: pass |
161 | 108 |