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1 | package Thread; |
2 | require Exporter; |
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3 | use XSLoader (); |
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4 | our($VERSION, @ISA, @EXPORT); |
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5 | |
6 | $VERSION = "1.0"; |
7 | |
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8 | @ISA = qw(Exporter); |
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9 | @EXPORT_OK = qw(yield cond_signal cond_broadcast cond_wait async); |
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10 | |
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11 | =head1 NAME |
12 | |
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13 | Thread - manipulate threads in Perl (EXPERIMENTAL, subject to change) |
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14 | |
15 | =head1 SYNOPSIS |
16 | |
17 | use Thread; |
18 | |
19 | my $t = new Thread \&start_sub, @start_args; |
20 | |
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21 | $result = $t->join; |
22 | $result = $t->eval; |
23 | $t->detach; |
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24 | $flags = $t->flags; |
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25 | |
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26 | if ($t->done) { |
27 | $t->join; |
28 | } |
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29 | |
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30 | if($t->equal($another_thread)) { |
31 | # ... |
32 | } |
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33 | |
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34 | my $tid = Thread->self->tid; |
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35 | my $tlist = Thread->list; |
36 | |
37 | lock($scalar); |
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38 | yield(); |
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39 | |
40 | use Thread 'async'; |
41 | |
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42 | =head1 DESCRIPTION |
43 | |
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44 | WARNING: Threading is an experimental feature. Both the interface |
45 | and implementation are subject to change drastically. In fact, this |
46 | documentation describes the flavor of threads that was in version |
47 | 5.005. Perl 5.6.0 and later have the beginnings of support for |
48 | interpreter threads, which (when finished) is expected to be |
49 | significantly different from what is described here. The information |
50 | contained here may therefore soon be obsolete. Use at your own risk! |
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51 | |
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52 | The C<Thread> module provides multithreading support for perl. |
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53 | |
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54 | =head1 FUNCTIONS |
55 | |
56 | =over 8 |
57 | |
58 | =item new \&start_sub |
59 | |
60 | =item new \&start_sub, LIST |
61 | |
62 | C<new> starts a new thread of execution in the referenced subroutine. The |
63 | optional list is passed as parameters to the subroutine. Execution |
64 | continues in both the subroutine and the code after the C<new> call. |
65 | |
66 | C<new Thread> returns a thread object representing the newly created |
67 | thread. |
68 | |
69 | =item lock VARIABLE |
70 | |
71 | C<lock> places a lock on a variable until the lock goes out of scope. If |
72 | the variable is locked by another thread, the C<lock> call will block until |
73 | it's available. C<lock> is recursive, so multiple calls to C<lock> are |
74 | safe--the variable will remain locked until the outermost lock on the |
75 | variable goes out of scope. |
76 | |
77 | Locks on variables only affect C<lock> calls--they do I<not> affect normal |
78 | access to a variable. (Locks on subs are different, and covered in a bit) |
79 | If you really, I<really> want locks to block access, then go ahead and tie |
80 | them to something and manage this yourself. This is done on purpose. While |
81 | managing access to variables is a good thing, perl doesn't force you out of |
82 | its living room... |
83 | |
84 | If a container object, such as a hash or array, is locked, all the elements |
85 | of that container are not locked. For example, if a thread does a C<lock |
86 | @a>, any other thread doing a C<lock($a[12])> won't block. |
87 | |
88 | You may also C<lock> a sub, using C<lock &sub>. Any calls to that sub from |
89 | another thread will block until the lock is released. This behaviour is not |
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90 | equivalent to declaring the sub with the C<locked> attribute. The C<locked> |
91 | attribute serializes access to a subroutine, but allows different threads |
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92 | non-simultaneous access. C<lock &sub>, on the other hand, will not allow |
93 | I<any> other thread access for the duration of the lock. |
94 | |
95 | Finally, C<lock> will traverse up references exactly I<one> level. |
96 | C<lock(\$a)> is equivalent to C<lock($a)>, while C<lock(\\$a)> is not. |
97 | |
98 | =item async BLOCK; |
99 | |
100 | C<async> creates a thread to execute the block immediately following |
101 | it. This block is treated as an anonymous sub, and so must have a |
102 | semi-colon after the closing brace. Like C<new Thread>, C<async> returns a |
103 | thread object. |
104 | |
105 | =item Thread->self |
106 | |
107 | The C<Thread-E<gt>self> function returns a thread object that represents |
108 | the thread making the C<Thread-E<gt>self> call. |
109 | |
110 | =item Thread->list |
111 | |
112 | C<Thread-E<gt>list> returns a list of thread objects for all running and |
113 | finished but un-C<join>ed threads. |
114 | |
115 | =item cond_wait VARIABLE |
116 | |
117 | The C<cond_wait> function takes a B<locked> variable as a parameter, |
118 | unlocks the variable, and blocks until another thread does a C<cond_signal> |
119 | or C<cond_broadcast> for that same locked variable. The variable that |
120 | C<cond_wait> blocked on is relocked after the C<cond_wait> is satisfied. |
121 | If there are multiple threads C<cond_wait>ing on the same variable, all but |
122 | one will reblock waiting to reaquire the lock on the variable. (So if |
123 | you're only using C<cond_wait> for synchronization, give up the lock as |
124 | soon as possible) |
125 | |
126 | =item cond_signal VARIABLE |
127 | |
128 | The C<cond_signal> function takes a locked variable as a parameter and |
129 | unblocks one thread that's C<cond_wait>ing on that variable. If more than |
130 | one thread is blocked in a C<cond_wait> on that variable, only one (and |
131 | which one is indeterminate) will be unblocked. |
132 | |
133 | If there are no threads blocked in a C<cond_wait> on the variable, the |
134 | signal is discarded. |
135 | |
136 | =item cond_broadcast VARIABLE |
137 | |
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138 | The C<cond_broadcast> function works similarly to C<cond_signal>. |
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139 | C<cond_broadcast>, though, will unblock B<all> the threads that are blocked |
140 | in a C<cond_wait> on the locked variable, rather than only one. |
141 | |
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142 | =item yield |
143 | |
144 | The C<yield> function allows another thread to take control of the |
145 | CPU. The exact results are implementation-dependent. |
146 | |
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147 | =back |
148 | |
149 | =head1 METHODS |
150 | |
151 | =over 8 |
152 | |
153 | =item join |
154 | |
155 | C<join> waits for a thread to end and returns any values the thread exited |
156 | with. C<join> will block until the thread has ended, though it won't block |
157 | if the thread has already terminated. |
158 | |
159 | If the thread being C<join>ed C<die>d, the error it died with will be |
160 | returned at this time. If you don't want the thread performing the C<join> |
161 | to die as well, you should either wrap the C<join> in an C<eval> or use the |
162 | C<eval> thread method instead of C<join>. |
163 | |
164 | =item eval |
165 | |
166 | The C<eval> method wraps an C<eval> around a C<join>, and so waits for a |
167 | thread to exit, passing along any values the thread might have returned. |
168 | Errors, of course, get placed into C<$@>. |
169 | |
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170 | =item detach |
171 | |
172 | C<detach> tells a thread that it is never going to be joined i.e. |
173 | that all traces of its existence can be removed once it stops running. |
174 | Errors in detached threads will not be visible anywhere - if you want |
175 | to catch them, you should use $SIG{__DIE__} or something like that. |
176 | |
177 | =item equal |
178 | |
179 | C<equal> tests whether two thread objects represent the same thread and |
180 | returns true if they do. |
181 | |
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182 | =item tid |
183 | |
184 | The C<tid> method returns the tid of a thread. The tid is a monotonically |
185 | increasing integer assigned when a thread is created. The main thread of a |
186 | program will have a tid of zero, while subsequent threads will have tids |
187 | assigned starting with one. |
188 | |
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189 | =item flags |
190 | |
191 | The C<flags> method returns the flags for the thread. This is the |
192 | integer value corresponding to the internal flags for the thread, and |
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193 | the value may not be all that meaningful to you. |
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194 | |
195 | =item done |
196 | |
197 | The C<done> method returns true if the thread you're checking has |
198 | finished, and false otherwise. |
199 | |
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200 | =back |
201 | |
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202 | =head1 LIMITATIONS |
203 | |
204 | The sequence number used to assign tids is a simple integer, and no |
205 | checking is done to make sure the tid isn't currently in use. If a program |
206 | creates more than 2^32 - 1 threads in a single run, threads may be assigned |
207 | duplicate tids. This limitation may be lifted in a future version of Perl. |
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208 | |
209 | =head1 SEE ALSO |
210 | |
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211 | L<attributes>, L<Thread::Queue>, L<Thread::Semaphore>, L<Thread::Specific>. |
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212 | |
213 | =cut |
214 | |
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215 | # |
216 | # Methods |
217 | # |
218 | |
219 | # |
220 | # Exported functions |
221 | # |
222 | sub async (&) { |
223 | return new Thread $_[0]; |
224 | } |
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225 | |
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226 | sub eval { |
227 | return eval { shift->join; }; |
228 | } |
229 | |
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230 | XSLoader::load 'Thread'; |
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231 | |
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232 | 1; |