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1 | package threads::shared; |
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2 | |
3 | use 5.007_003; |
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4 | use strict; |
5 | use warnings; |
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6 | |
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7 | require Exporter; |
8 | our @ISA = qw(Exporter); |
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9 | our @EXPORT = qw(share cond_wait cond_broadcast cond_signal); |
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10 | our $VERSION = '0.90'; |
11 | |
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12 | if ($threads::threads) { |
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13 | *cond_wait = \&cond_wait_enabled; |
14 | *cond_signal = \&cond_signal_enabled; |
15 | *cond_broadcast = \&cond_broadcast_enabled; |
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16 | require XSLoader; |
17 | XSLoader::load('threads::shared',$VERSION); |
18 | } |
19 | else { |
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20 | *share = \&share_disabled; |
21 | *cond_wait = \&cond_wait_disabled; |
22 | *cond_signal = \&cond_signal_disabled; |
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23 | *cond_broadcast = \&cond_broadcast_disabled; |
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24 | } |
25 | |
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26 | |
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27 | sub cond_wait_disabled (\[$@%]) { undef } |
28 | sub cond_signal_disabled (\[$@%]) { undef } |
29 | sub cond_broadcast_disabled (\[$@%]) { undef } |
30 | sub share_disabled (\[$@%]) { return $_[0] } |
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31 | |
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32 | $threads::shared::threads_shared = 1; |
33 | |
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34 | |
35 | sub threads::shared::tie::SPLICE |
36 | { |
37 | die "Splice not implemented for shared arrays"; |
38 | } |
39 | |
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40 | __END__ |
41 | |
42 | =head1 NAME |
43 | |
44 | threads::shared - Perl extension for sharing data structures between threads |
45 | |
46 | =head1 SYNOPSIS |
47 | |
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48 | use threads; |
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49 | use threads::shared; |
50 | |
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51 | my $var : shared; |
52 | |
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53 | my($scalar, @array, %hash); |
54 | share($scalar); |
55 | share(@array); |
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56 | share(%hash); |
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57 | my $bar = &share([]); |
58 | $hash{bar} = &share({}); |
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59 | |
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60 | { lock(%hash); ... } |
61 | |
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62 | cond_wait($scalar); |
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63 | cond_broadcast(@array); |
64 | cond_signal(%hash); |
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65 | |
66 | =head1 DESCRIPTION |
67 | |
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68 | By default, variables are private to each thread, and each newly created |
69 | thread gets a private copy of each existing variable. This module allows |
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70 | you to share variables across different threads (and pseudoforks on Win32). |
71 | It is used together with the threads module. |
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72 | |
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73 | =head1 EXPORT |
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74 | |
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75 | C<share>, C<cond_wait>, C<cond_signal>, C<cond_broadcast> |
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76 | |
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77 | Note that if this module is imported when C<threads> has not yet been |
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78 | loaded, then these functions all become no-ops. This makes it possible |
79 | to write modules that will work in both threaded and non-threaded |
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80 | environments. |
81 | |
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82 | =head1 FUNCTIONS |
83 | |
84 | =over 4 |
85 | |
86 | =item share VARIABLE |
87 | |
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88 | C<share> takes a value and marks it as shared. You can share a scalar, |
89 | array, hash, scalar ref, array ref or hash ref. C<share> will return |
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90 | the shared rvalue but always as a reference. |
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91 | |
92 | C<share> will traverse up references exactly I<one> level. |
93 | C<share(\$a)> is equivalent to C<share($a)>, while C<share(\\$a)> is not. |
94 | |
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95 | A variable can also be marked as shared at compile time by using the |
96 | C<shared> attribute: C<my $var : shared>. |
97 | |
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98 | If you want to share a newly created reference unfortunately you |
99 | need to use C<&share([])> and C<&share({})> syntax due to problems |
100 | with Perl's prototyping. |
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101 | |
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102 | =item lock VARIABLE |
103 | |
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104 | C<lock> places a lock on a variable until the lock goes out of scope. |
105 | If the variable is locked by another thread, the C<lock> call will |
106 | block until it's available. C<lock> is recursive, so multiple calls |
107 | to C<lock> are safe -- the variable will remain locked until the |
108 | outermost lock on the variable goes out of scope. |
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109 | |
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110 | If a container object, such as a hash or array, is locked, all the |
111 | elements of that container are not locked. For example, if a thread |
112 | does a C<lock @a>, any other thread doing a C<lock($a[12])> won't block. |
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113 | |
114 | C<lock> will traverse up references exactly I<one> level. |
115 | C<lock(\$a)> is equivalent to C<lock($a)>, while C<lock(\\$a)> is not. |
116 | |
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117 | Note that you cannot explicitly unlock a variable; you can only wait |
118 | for the lock to go out of scope. If you need more fine-grained |
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119 | control, see L<Thread::Semaphore>. |
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120 | |
121 | =item cond_wait VARIABLE |
122 | |
123 | The C<cond_wait> function takes a B<locked> variable as a parameter, |
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124 | unlocks the variable, and blocks until another thread does a |
125 | C<cond_signal> or C<cond_broadcast> for that same locked variable. |
126 | The variable that C<cond_wait> blocked on is relocked after the |
127 | C<cond_wait> is satisfied. If there are multiple threads |
128 | C<cond_wait>ing on the same variable, all but one will reblock waiting |
129 | to reacquire the lock on the variable. (So if you're only using |
130 | C<cond_wait> for synchronisation, give up the lock as soon as |
131 | possible). The two actions of unlocking the variable and entering the |
132 | blocked wait state are atomic, The two actions of exiting from the |
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133 | blocked wait state and relocking the variable are not. |
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134 | |
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135 | It is important to note that the variable can be notified even if |
136 | no thread C<cond_signal> or C<cond_broadcast> on the variable. |
137 | It is therefore important to check the value of the variable and |
138 | go back to waiting if the requirement is not fulfilled. |
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139 | |
140 | =item cond_signal VARIABLE |
141 | |
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142 | The C<cond_signal> function takes a B<locked> variable as a parameter |
143 | and unblocks one thread that's C<cond_wait>ing on that variable. If |
144 | more than one thread is blocked in a C<cond_wait> on that variable, |
145 | only one (and which one is indeterminate) will be unblocked. |
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146 | |
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147 | If there are no threads blocked in a C<cond_wait> on the variable, |
148 | the signal is discarded. By always locking before signaling, you can |
149 | (with care), avoid signaling before another thread has entered cond_wait(). |
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150 | |
151 | C<cond_signal> will normally generate a warning if you attempt to use it |
152 | on an unlocked variable. On the rare occasions where doing this may be |
153 | sensible, you can skip the warning with |
154 | |
155 | { no warnings 'threads'; cond_signal($foo) } |
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156 | |
157 | =item cond_broadcast VARIABLE |
158 | |
159 | The C<cond_broadcast> function works similarly to C<cond_signal>. |
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160 | C<cond_broadcast>, though, will unblock B<all> the threads that are |
161 | blocked in a C<cond_wait> on the locked variable, rather than only one. |
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162 | |
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163 | =back |
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164 | |
165 | =head1 NOTES |
166 | |
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167 | threads::shared is designed to disable itself silently if threads are |
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168 | not available. If you want access to threads, you must C<use threads> |
169 | before you C<use threads::shared>. threads will emit a warning if you |
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170 | use it after threads::shared. |
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171 | |
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172 | =head1 BUGS |
173 | |
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174 | C<bless> is not supported on shared references. In the current version, |
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175 | C<bless> will only bless the thread local reference and the blessing |
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176 | will not propagate to the other threads. This is expected to be |
177 | implemented in a future version of Perl. |
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178 | |
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179 | Does not support splice on arrays! |
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180 | |
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181 | Taking references to the elements of shared arrays and hashes does not |
182 | autovivify the elements, and neither does slicing a shared array/hash |
183 | over non-existent indices/keys autovivify the elements. |
184 | |
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185 | share() allows you to C<share $hashref->{key}> without giving any error |
186 | message. But the C<$hashref->{key}> is B<not> shared, causing the error |
187 | "locking can only be used on shared values" to occur when you attempt to |
188 | C<lock $hasref->{key}>. |
189 | |
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190 | =head1 AUTHOR |
191 | |
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192 | Arthur Bergman E<lt>arthur at contiller.seE<gt> |
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193 | |
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194 | threads::shared is released under the same license as Perl |
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195 | |
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196 | Documentation borrowed from the old Thread.pm |
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197 | |
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198 | =head1 SEE ALSO |
199 | |
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200 | L<threads>, L<perlthrtut>, L<http://www.perl.com/pub/a/2002/06/11/threads.html> |
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201 | |
202 | =cut |