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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 | $t->detach; |
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24 | |
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25 | if($t->equal($another_thread)) { |
26 | # ... |
27 | } |
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28 | |
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29 | my $tid = Thread->self->tid; |
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30 | my $tlist = Thread->list; |
31 | |
32 | lock($scalar); |
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33 | yield(); |
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34 | |
35 | use Thread 'async'; |
36 | |
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37 | =head1 DESCRIPTION |
38 | |
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39 | The C<Thread> module provides multithreading support for perl. |
40 | |
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41 | WARNING: Threading is an experimental feature. Both the interface |
42 | and implementation are subject to change drastically. |
43 | |
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44 | In fact, this documentation describes the flavor of threads that was in |
45 | version 5.005. Perl v5.6 has the beginnings of support for interpreter |
46 | threads, which (when finished) is expected to be significantly different |
47 | from what is described here. The information contained here may therefore |
48 | soon be obsolete. Use at your own risk! |
49 | |
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50 | =head1 FUNCTIONS |
51 | |
52 | =over 8 |
53 | |
54 | =item new \&start_sub |
55 | |
56 | =item new \&start_sub, LIST |
57 | |
58 | C<new> starts a new thread of execution in the referenced subroutine. The |
59 | optional list is passed as parameters to the subroutine. Execution |
60 | continues in both the subroutine and the code after the C<new> call. |
61 | |
62 | C<new Thread> returns a thread object representing the newly created |
63 | thread. |
64 | |
65 | =item lock VARIABLE |
66 | |
67 | C<lock> places a lock on a variable until the lock goes out of scope. If |
68 | the variable is locked by another thread, the C<lock> call will block until |
69 | it's available. C<lock> is recursive, so multiple calls to C<lock> are |
70 | safe--the variable will remain locked until the outermost lock on the |
71 | variable goes out of scope. |
72 | |
73 | Locks on variables only affect C<lock> calls--they do I<not> affect normal |
74 | access to a variable. (Locks on subs are different, and covered in a bit) |
75 | If you really, I<really> want locks to block access, then go ahead and tie |
76 | them to something and manage this yourself. This is done on purpose. While |
77 | managing access to variables is a good thing, perl doesn't force you out of |
78 | its living room... |
79 | |
80 | If a container object, such as a hash or array, is locked, all the elements |
81 | of that container are not locked. For example, if a thread does a C<lock |
82 | @a>, any other thread doing a C<lock($a[12])> won't block. |
83 | |
84 | You may also C<lock> a sub, using C<lock &sub>. Any calls to that sub from |
85 | another thread will block until the lock is released. This behaviour is not |
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86 | equivalent to declaring the sub with the C<locked> attribute. The C<locked> |
87 | attribute serializes access to a subroutine, but allows different threads |
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88 | non-simultaneous access. C<lock &sub>, on the other hand, will not allow |
89 | I<any> other thread access for the duration of the lock. |
90 | |
91 | Finally, C<lock> will traverse up references exactly I<one> level. |
92 | C<lock(\$a)> is equivalent to C<lock($a)>, while C<lock(\\$a)> is not. |
93 | |
94 | =item async BLOCK; |
95 | |
96 | C<async> creates a thread to execute the block immediately following |
97 | it. This block is treated as an anonymous sub, and so must have a |
98 | semi-colon after the closing brace. Like C<new Thread>, C<async> returns a |
99 | thread object. |
100 | |
101 | =item Thread->self |
102 | |
103 | The C<Thread-E<gt>self> function returns a thread object that represents |
104 | the thread making the C<Thread-E<gt>self> call. |
105 | |
106 | =item Thread->list |
107 | |
108 | C<Thread-E<gt>list> returns a list of thread objects for all running and |
109 | finished but un-C<join>ed threads. |
110 | |
111 | =item cond_wait VARIABLE |
112 | |
113 | The C<cond_wait> function takes a B<locked> variable as a parameter, |
114 | unlocks the variable, and blocks until another thread does a C<cond_signal> |
115 | or C<cond_broadcast> for that same locked variable. The variable that |
116 | C<cond_wait> blocked on is relocked after the C<cond_wait> is satisfied. |
117 | If there are multiple threads C<cond_wait>ing on the same variable, all but |
118 | one will reblock waiting to reaquire the lock on the variable. (So if |
119 | you're only using C<cond_wait> for synchronization, give up the lock as |
120 | soon as possible) |
121 | |
122 | =item cond_signal VARIABLE |
123 | |
124 | The C<cond_signal> function takes a locked variable as a parameter and |
125 | unblocks one thread that's C<cond_wait>ing on that variable. If more than |
126 | one thread is blocked in a C<cond_wait> on that variable, only one (and |
127 | which one is indeterminate) will be unblocked. |
128 | |
129 | If there are no threads blocked in a C<cond_wait> on the variable, the |
130 | signal is discarded. |
131 | |
132 | =item cond_broadcast VARIABLE |
133 | |
134 | The C<cond_broadcast> function works similarly to C<cond_wait>. |
135 | C<cond_broadcast>, though, will unblock B<all> the threads that are blocked |
136 | in a C<cond_wait> on the locked variable, rather than only one. |
137 | |
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138 | =item yield |
139 | |
140 | The C<yield> function allows another thread to take control of the |
141 | CPU. The exact results are implementation-dependent. |
142 | |
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143 | =back |
144 | |
145 | =head1 METHODS |
146 | |
147 | =over 8 |
148 | |
149 | =item join |
150 | |
151 | C<join> waits for a thread to end and returns any values the thread exited |
152 | with. C<join> will block until the thread has ended, though it won't block |
153 | if the thread has already terminated. |
154 | |
155 | If the thread being C<join>ed C<die>d, the error it died with will be |
156 | returned at this time. If you don't want the thread performing the C<join> |
157 | to die as well, you should either wrap the C<join> in an C<eval> or use the |
158 | C<eval> thread method instead of C<join>. |
159 | |
160 | =item eval |
161 | |
162 | The C<eval> method wraps an C<eval> around a C<join>, and so waits for a |
163 | thread to exit, passing along any values the thread might have returned. |
164 | Errors, of course, get placed into C<$@>. |
165 | |
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166 | =item detach |
167 | |
168 | C<detach> tells a thread that it is never going to be joined i.e. |
169 | that all traces of its existence can be removed once it stops running. |
170 | Errors in detached threads will not be visible anywhere - if you want |
171 | to catch them, you should use $SIG{__DIE__} or something like that. |
172 | |
173 | =item equal |
174 | |
175 | C<equal> tests whether two thread objects represent the same thread and |
176 | returns true if they do. |
177 | |
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178 | =item tid |
179 | |
180 | The C<tid> method returns the tid of a thread. The tid is a monotonically |
181 | increasing integer assigned when a thread is created. The main thread of a |
182 | program will have a tid of zero, while subsequent threads will have tids |
183 | assigned starting with one. |
184 | |
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185 | =back |
186 | |
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187 | =head1 LIMITATIONS |
188 | |
189 | The sequence number used to assign tids is a simple integer, and no |
190 | checking is done to make sure the tid isn't currently in use. If a program |
191 | creates more than 2^32 - 1 threads in a single run, threads may be assigned |
192 | duplicate tids. This limitation may be lifted in a future version of Perl. |
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193 | |
194 | =head1 SEE ALSO |
195 | |
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196 | L<attributes>, L<Thread::Queue>, L<Thread::Semaphore>, L<Thread::Specific>. |
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197 | |
198 | =cut |
199 | |
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200 | # |
201 | # Methods |
202 | # |
203 | |
204 | # |
205 | # Exported functions |
206 | # |
207 | sub async (&) { |
208 | return new Thread $_[0]; |
209 | } |
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210 | |
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211 | sub eval { |
212 | return eval { shift->join; }; |
213 | } |
214 | |
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215 | XSLoader::load 'Thread'; |
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216 | |
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217 | 1; |