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1 | # lock.py - simple advisory locking scheme for mercurial |
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1 | # lock.py - simple advisory locking scheme for mercurial | |
2 | # |
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2 | # | |
3 | # Copyright 2005, 2006 Matt Mackall <mpm@selenic.com> |
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3 | # Copyright 2005, 2006 Matt Mackall <mpm@selenic.com> | |
4 | # |
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4 | # | |
5 | # This software may be used and distributed according to the terms of the |
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5 | # This software may be used and distributed according to the terms of the | |
6 | # GNU General Public License version 2, incorporated herein by reference. |
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6 | # GNU General Public License version 2, incorporated herein by reference. | |
7 |
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7 | |||
8 | import util, error |
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8 | import util, error | |
9 | import errno, os, socket, time |
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9 | import errno, os, socket, time | |
10 | import warnings |
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10 | import warnings | |
11 |
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11 | |||
12 | class lock(object): |
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12 | class lock(object): | |
13 | '''An advisory lock held by one process to control access to a set |
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13 | '''An advisory lock held by one process to control access to a set | |
14 | of files. Non-cooperating processes or incorrectly written scripts |
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14 | of files. Non-cooperating processes or incorrectly written scripts | |
15 | can ignore Mercurial's locking scheme and stomp all over the |
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15 | can ignore Mercurial's locking scheme and stomp all over the | |
16 | repository, so don't do that. |
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16 | repository, so don't do that. | |
17 |
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17 | |||
18 | Typically used via localrepository.lock() to lock the repository |
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18 | Typically used via localrepository.lock() to lock the repository | |
19 | store (.hg/store/) or localrepository.wlock() to lock everything |
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19 | store (.hg/store/) or localrepository.wlock() to lock everything | |
20 | else under .hg/.''' |
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20 | else under .hg/.''' | |
21 |
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21 | |||
22 | # lock is symlink on platforms that support it, file on others. |
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22 | # lock is symlink on platforms that support it, file on others. | |
23 |
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23 | |||
24 | # symlink is used because create of directory entry and contents |
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24 | # symlink is used because create of directory entry and contents | |
25 | # are atomic even over nfs. |
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25 | # are atomic even over nfs. | |
26 |
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26 | |||
27 | # old-style lock: symlink to pid |
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27 | # old-style lock: symlink to pid | |
28 | # new-style lock: symlink to hostname:pid |
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28 | # new-style lock: symlink to hostname:pid | |
29 |
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29 | |||
30 | _host = None |
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30 | _host = None | |
31 |
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31 | |||
32 | def __init__(self, file, timeout=-1, releasefn=None, desc=None): |
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32 | def __init__(self, file, timeout=-1, releasefn=None, desc=None): | |
33 | self.f = file |
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33 | self.f = file | |
34 | self.held = 0 |
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34 | self.held = 0 | |
35 | self.timeout = timeout |
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35 | self.timeout = timeout | |
36 | self.releasefn = releasefn |
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36 | self.releasefn = releasefn | |
37 | self.desc = desc |
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37 | self.desc = desc | |
38 | self.lock() |
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38 | self.lock() | |
39 |
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39 | |||
40 | def __del__(self): |
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40 | def __del__(self): | |
41 | if self.held: |
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41 | if self.held: | |
42 | warnings.warn("use lock.release instead of del lock", |
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42 | warnings.warn("use lock.release instead of del lock", | |
43 | category=DeprecationWarning, |
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43 | category=DeprecationWarning, | |
44 | stacklevel=2) |
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44 | stacklevel=2) | |
45 |
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45 | |||
46 | # ensure the lock will be removed |
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46 | # ensure the lock will be removed | |
47 | # even if recursive locking did occur |
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47 | # even if recursive locking did occur | |
48 | self.held = 1 |
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48 | self.held = 1 | |
49 |
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49 | |||
50 | self.release() |
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50 | self.release() | |
51 |
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51 | |||
52 | def lock(self): |
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52 | def lock(self): | |
53 | timeout = self.timeout |
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53 | timeout = self.timeout | |
54 | while 1: |
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54 | while 1: | |
55 | try: |
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55 | try: | |
56 | self.trylock() |
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56 | self.trylock() | |
57 | return 1 |
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57 | return 1 | |
58 | except error.LockHeld, inst: |
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58 | except error.LockHeld, inst: | |
59 | if timeout != 0: |
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59 | if timeout != 0: | |
60 | time.sleep(1) |
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60 | time.sleep(1) | |
61 | if timeout > 0: |
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61 | if timeout > 0: | |
62 | timeout -= 1 |
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62 | timeout -= 1 | |
63 | continue |
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63 | continue | |
64 | raise error.LockHeld(errno.ETIMEDOUT, inst.filename, self.desc, |
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64 | raise error.LockHeld(errno.ETIMEDOUT, inst.filename, self.desc, | |
65 | inst.locker) |
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65 | inst.locker) | |
66 |
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66 | |||
67 | def trylock(self): |
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67 | def trylock(self): | |
68 | if self.held: |
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68 | if self.held: | |
69 | self.held += 1 |
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69 | self.held += 1 | |
70 | return |
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70 | return | |
71 | if lock._host is None: |
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71 | if lock._host is None: | |
72 | lock._host = socket.gethostname() |
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72 | lock._host = socket.gethostname() | |
73 | lockname = '%s:%s' % (lock._host, os.getpid()) |
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73 | lockname = '%s:%s' % (lock._host, os.getpid()) | |
74 | while not self.held: |
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74 | while not self.held: | |
75 | try: |
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75 | try: | |
76 | util.makelock(lockname, self.f) |
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76 | util.makelock(lockname, self.f) | |
77 | self.held = 1 |
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77 | self.held = 1 | |
78 | except (OSError, IOError), why: |
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78 | except (OSError, IOError), why: | |
79 | if why.errno == errno.EEXIST: |
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79 | if why.errno == errno.EEXIST: | |
80 | locker = self.testlock() |
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80 | locker = self.testlock() | |
81 | if locker is not None: |
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81 | if locker is not None: | |
82 | raise error.LockHeld(errno.EAGAIN, self.f, self.desc, |
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82 | raise error.LockHeld(errno.EAGAIN, self.f, self.desc, | |
83 | locker) |
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83 | locker) | |
84 | else: |
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84 | else: | |
85 | raise error.LockUnavailable(why.errno, why.strerror, |
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85 | raise error.LockUnavailable(why.errno, why.strerror, | |
86 | why.filename, self.desc) |
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86 | why.filename, self.desc) | |
87 |
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87 | |||
88 | def testlock(self): |
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88 | def testlock(self): | |
89 | """return id of locker if lock is valid, else None. |
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89 | """return id of locker if lock is valid, else None. | |
90 |
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90 | |||
91 | If old-style lock, we cannot tell what machine locker is on. |
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91 | If old-style lock, we cannot tell what machine locker is on. | |
92 | with new-style lock, if locker is on this machine, we can |
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92 | with new-style lock, if locker is on this machine, we can | |
93 | see if locker is alive. If locker is on this machine but |
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93 | see if locker is alive. If locker is on this machine but | |
94 | not alive, we can safely break lock. |
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94 | not alive, we can safely break lock. | |
95 |
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95 | |||
96 | The lock file is only deleted when None is returned. |
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96 | The lock file is only deleted when None is returned. | |
97 |
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97 | |||
98 | """ |
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98 | """ | |
99 | locker = util.readlock(self.f) |
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99 | locker = util.readlock(self.f) | |
100 | try: |
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100 | try: | |
101 | host, pid = locker.split(":", 1) |
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101 | host, pid = locker.split(":", 1) | |
102 | except ValueError: |
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102 | except ValueError: | |
103 | return locker |
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103 | return locker | |
104 | if host != lock._host: |
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104 | if host != lock._host: | |
105 | return locker |
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105 | return locker | |
106 | try: |
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106 | try: | |
107 | pid = int(pid) |
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107 | pid = int(pid) | |
108 | except: |
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108 | except: | |
109 | return locker |
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109 | return locker | |
110 | if util.testpid(pid): |
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110 | if util.testpid(pid): | |
111 | return locker |
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111 | return locker | |
112 | # if locker dead, break lock. must do this with another lock |
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112 | # if locker dead, break lock. must do this with another lock | |
113 | # held, or can race and break valid lock. |
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113 | # held, or can race and break valid lock. | |
114 | try: |
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114 | try: | |
115 | l = lock(self.f + '.break') |
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115 | l = lock(self.f + '.break') | |
116 | l.trylock() |
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116 | l.trylock() | |
117 | os.unlink(self.f) |
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117 | os.unlink(self.f) | |
118 | l.release() |
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118 | l.release() | |
119 | except error.LockError: |
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119 | except error.LockError: | |
120 | return locker |
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120 | return locker | |
121 |
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121 | |||
122 | def release(self): |
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122 | def release(self): | |
123 | if self.held > 1: |
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123 | if self.held > 1: | |
124 | self.held -= 1 |
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124 | self.held -= 1 | |
125 |
elif self.held |
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125 | elif self.held == 1: | |
126 | self.held = 0 |
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126 | self.held = 0 | |
127 | if self.releasefn: |
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127 | if self.releasefn: | |
128 | self.releasefn() |
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128 | self.releasefn() | |
129 | try: |
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129 | try: | |
130 | os.unlink(self.f) |
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130 | os.unlink(self.f) | |
131 | except: pass |
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131 | except: pass | |
132 |
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132 | |||
133 | def release(*locks): |
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133 | def release(*locks): | |
134 | for lock in locks: |
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134 | for lock in locks: | |
135 | if lock is not None: |
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135 | if lock is not None: | |
136 | lock.release() |
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136 | lock.release() | |
137 |
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137 |
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