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1 | package Thread; |
2 | |
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3 | use strict; |
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4 | use warnings; |
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5 | |
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6 | our $VERSION = '3.01'; |
7 | $VERSION = eval $VERSION; |
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8 | |
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9 | BEGIN { |
10 | use Config; |
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11 | if (! $Config{useithreads}) { |
12 | die("This Perl not built to support threads\n"); |
13 | } |
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14 | } |
15 | |
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16 | use threads 'yield'; |
17 | use threads::shared; |
18 | |
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19 | require Exporter; |
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20 | our @ISA = qw(Exporter threads); |
21 | our @EXPORT = qw(cond_wait cond_broadcast cond_signal); |
22 | our @EXPORT_OK = qw(async yield); |
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23 | |
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24 | sub async (&) { return Thread->new(shift); } |
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25 | |
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26 | sub done { return ! shift->is_running(); } |
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27 | |
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28 | sub eval { die("'eval' not implemented with 'ithreads'\n"); }; |
29 | sub flags { die("'flags' not implemented with 'ithreads'\n"); }; |
30 | |
31 | 1; |
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32 | |
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33 | __END__ |
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34 | |
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35 | =head1 NAME |
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36 | |
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37 | Thread - Manipulate threads in Perl (for old code only) |
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38 | |
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39 | =head1 DEPRECATED |
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40 | |
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41 | The C<Thread> module served as the frontend to the old-style thread model, |
42 | called I<5005threads>, that was introduced in release 5.005. That model was |
43 | deprecated, and has been removed in version 5.10. |
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44 | |
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45 | For old code and interim backwards compatibility, the C<Thread> module has |
46 | been reworked to function as a frontend for the new interpreter threads |
47 | (I<ithreads>) model. However, some previous functionality is not available. |
48 | Further, the data sharing models between the two thread models are completely |
49 | different, and anything to do with data sharing has to be thought differently. |
50 | With I<ithreads>, you must explicitly C<share()> variables between the |
51 | threads. |
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52 | |
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53 | You are strongly encouraged to migrate any existing threaded code to the new |
54 | model (i.e., use the C<threads> and C<threads::shared> modules) as soon as |
55 | possible. |
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56 | |
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57 | =head1 HISTORY |
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58 | |
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59 | In Perl 5.005, the thread model was that all data is implicitly shared, and |
60 | shared access to data has to be explicitly synchronized. This model is called |
61 | I<5005threads>. |
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62 | |
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63 | In Perl 5.6, a new model was introduced in which all is was thread local and |
64 | shared access to data has to be explicitly declared. This model is called |
65 | I<ithreads>, for "interpreter threads". |
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66 | |
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67 | In Perl 5.6, the I<ithreads> model was not available as a public API; only as |
68 | an internal API that was available for extension writers, and to implement |
69 | fork() emulation on Win32 platforms. |
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70 | |
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71 | In Perl 5.8, the I<ithreads> model became available through the C<threads> |
72 | module, and the I<5005threads> model was deprecated. |
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73 | |
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74 | In Perl 5.10, the I<5005threads> model was removed from the Perl interpreter. |
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75 | |
76 | =head1 SYNOPSIS |
77 | |
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78 | use Thread qw(:DEFAULT async yield); |
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79 | |
80 | my $t = Thread->new(\&start_sub, @start_args); |
81 | |
82 | $result = $t->join; |
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83 | $t->detach; |
84 | |
85 | if ($t->done) { |
86 | $t->join; |
87 | } |
88 | |
89 | if($t->equal($another_thread)) { |
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90 | # ... |
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91 | } |
92 | |
93 | yield(); |
94 | |
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95 | my $tid = Thread->self->tid; |
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96 | |
97 | lock($scalar); |
98 | lock(@array); |
99 | lock(%hash); |
100 | |
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101 | my @list = Thread->list; |
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102 | |
103 | =head1 DESCRIPTION |
104 | |
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105 | The C<Thread> module provides multithreading support for Perl. |
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106 | |
107 | =head1 FUNCTIONS |
108 | |
109 | =over 8 |
110 | |
111 | =item $thread = Thread->new(\&start_sub) |
112 | |
113 | =item $thread = Thread->new(\&start_sub, LIST) |
114 | |
115 | C<new> starts a new thread of execution in the referenced subroutine. The |
116 | optional list is passed as parameters to the subroutine. Execution |
117 | continues in both the subroutine and the code after the C<new> call. |
118 | |
119 | C<Thread->new> returns a thread object representing the newly created |
120 | thread. |
121 | |
122 | =item lock VARIABLE |
123 | |
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124 | C<lock> places a lock on a variable until the lock goes out of scope. |
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125 | |
126 | If the variable is locked by another thread, the C<lock> call will |
127 | block until it's available. C<lock> is recursive, so multiple calls |
128 | to C<lock> are safe--the variable will remain locked until the |
129 | outermost lock on the variable goes out of scope. |
130 | |
131 | Locks on variables only affect C<lock> calls--they do I<not> affect normal |
132 | access to a variable. (Locks on subs are different, and covered in a bit.) |
133 | If you really, I<really> want locks to block access, then go ahead and tie |
134 | them to something and manage this yourself. This is done on purpose. |
135 | While managing access to variables is a good thing, Perl doesn't force |
136 | you out of its living room... |
137 | |
138 | If a container object, such as a hash or array, is locked, all the |
139 | elements of that container are not locked. For example, if a thread |
140 | does a C<lock @a>, any other thread doing a C<lock($a[12])> won't |
141 | block. |
142 | |
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143 | Finally, C<lock> will traverse up references exactly I<one> level. |
144 | C<lock(\$a)> is equivalent to C<lock($a)>, while C<lock(\\$a)> is not. |
145 | |
146 | =item async BLOCK; |
147 | |
148 | C<async> creates a thread to execute the block immediately following |
149 | it. This block is treated as an anonymous sub, and so must have a |
150 | semi-colon after the closing brace. Like C<Thread->new>, C<async> |
151 | returns a thread object. |
152 | |
153 | =item Thread->self |
154 | |
155 | The C<Thread-E<gt>self> function returns a thread object that represents |
156 | the thread making the C<Thread-E<gt>self> call. |
157 | |
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158 | =item Thread->list |
159 | |
160 | Returns a list of all non-joined, non-detached Thread objects. |
161 | |
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162 | =item cond_wait VARIABLE |
163 | |
164 | The C<cond_wait> function takes a B<locked> variable as |
165 | a parameter, unlocks the variable, and blocks until another thread |
166 | does a C<cond_signal> or C<cond_broadcast> for that same locked |
167 | variable. The variable that C<cond_wait> blocked on is relocked |
168 | after the C<cond_wait> is satisfied. If there are multiple threads |
169 | C<cond_wait>ing on the same variable, all but one will reblock waiting |
170 | to reaquire the lock on the variable. (So if you're only using |
171 | C<cond_wait> for synchronization, give up the lock as soon as |
172 | possible.) |
173 | |
174 | =item cond_signal VARIABLE |
175 | |
176 | The C<cond_signal> function takes a locked variable as a parameter and |
177 | unblocks one thread that's C<cond_wait>ing on that variable. If more than |
178 | one thread is blocked in a C<cond_wait> on that variable, only one (and |
179 | which one is indeterminate) will be unblocked. |
180 | |
181 | If there are no threads blocked in a C<cond_wait> on the variable, |
182 | the signal is discarded. |
183 | |
184 | =item cond_broadcast VARIABLE |
185 | |
186 | The C<cond_broadcast> function works similarly to C<cond_signal>. |
187 | C<cond_broadcast>, though, will unblock B<all> the threads that are |
188 | blocked in a C<cond_wait> on the locked variable, rather than only |
189 | one. |
190 | |
191 | =item yield |
192 | |
193 | The C<yield> function allows another thread to take control of the |
194 | CPU. The exact results are implementation-dependent. |
195 | |
196 | =back |
197 | |
198 | =head1 METHODS |
199 | |
200 | =over 8 |
201 | |
202 | =item join |
203 | |
204 | C<join> waits for a thread to end and returns any values the thread |
205 | exited with. C<join> will block until the thread has ended, though |
206 | it won't block if the thread has already terminated. |
207 | |
208 | If the thread being C<join>ed C<die>d, the error it died with will |
209 | be returned at this time. If you don't want the thread performing |
210 | the C<join> to die as well, you should either wrap the C<join> in |
211 | an C<eval> or use the C<eval> thread method instead of C<join>. |
212 | |
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213 | =item detach |
214 | |
215 | C<detach> tells a thread that it is never going to be joined i.e. |
216 | that all traces of its existence can be removed once it stops running. |
217 | Errors in detached threads will not be visible anywhere - if you want |
218 | to catch them, you should use $SIG{__DIE__} or something like that. |
219 | |
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220 | =item equal |
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221 | |
222 | C<equal> tests whether two thread objects represent the same thread and |
223 | returns true if they do. |
224 | |
225 | =item tid |
226 | |
227 | The C<tid> method returns the tid of a thread. The tid is |
228 | a monotonically increasing integer assigned when a thread is |
229 | created. The main thread of a program will have a tid of zero, |
230 | while subsequent threads will have tids assigned starting with one. |
231 | |
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232 | =item done |
233 | |
234 | The C<done> method returns true if the thread you're checking has |
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235 | finished, and false otherwise. |
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236 | |
237 | =back |
238 | |
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239 | =head1 DEFUNCT |
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240 | |
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241 | The following were implemented with I<5005threads>, but are no longer |
242 | available with I<ithreads>. |
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243 | |
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244 | =over 8 |
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245 | |
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246 | =item lock(\&sub) |
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247 | |
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248 | With 5005threads, you could also C<lock> a sub such that any calls to that sub |
249 | from another thread would block until the lock was released. |
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250 | |
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251 | Also, subroutines could be declared with the C<:locked> attribute which would |
252 | serialize access to the subroutine, but allowed different threads |
253 | non-simultaneous access. |
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254 | |
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255 | =item eval |
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256 | |
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257 | The C<eval> method wrapped an C<eval> around a C<join>, and so waited for a |
258 | thread to exit, passing along any values the thread might have returned and |
259 | placing any errors into C<$@>. |
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260 | |
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261 | =item flags |
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262 | |
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263 | The C<flags> method returned the flags for the thread - an integer value |
264 | corresponding to the internal flags for the thread. |
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265 | |
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266 | =back |
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267 | |
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268 | =head1 SEE ALSO |
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269 | |
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270 | L<threads>, L<threads::shared>, L<Thread::Queue>, L<Thread::Semaphore> |
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271 | |
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272 | =cut |