9 unless ($Config{useithreads}) {
10 my @caller = caller(2);
12 $caller[1] line $caller[2]:
14 This Perl hasn't been configured and built properly for the threads
15 module to work. (The 'useithreads' configuration option hasn't been used.)
17 Having threads support requires all of Perl and all of the XS modules in
18 the Perl installation to be rebuilt, it is not just a question of adding
19 the threads module. (In other words, threaded and non-threaded Perls
20 are binary incompatible.)
22 If you want to the use the threads module, please contact the people
25 Cannot continue, aborting.
35 warn "Warning, threads::shared has already been loaded. ".
36 "To enable shared variables for these modules 'use threads' ".
37 "must be called before any of those modules are loaded\n"
38 if($threads::shared::threads_shared);
44 our @ISA = qw(Exporter DynaLoader);
46 our %EXPORT_TAGS = ( all => [qw(yield)]);
48 our @EXPORT_OK = ( @{ $EXPORT_TAGS{'all'} } );
53 our $VERSION = '1.03';
56 # || 0 to ensure compatibility with previous versions
57 sub equal { ($_[0]->tid == $_[1]->tid) || 0 }
59 # use "goto" trick to avoid pad problems from 5.8.1 (fixed in 5.8.2)
60 # should also be faster
61 sub async (&;@) { unshift @_,'threads'; goto &new }
64 return undef unless @_ > 1;
65 foreach (threads->list) {
66 return $_ if $_->tid == $_[1];
71 $threads::threads = 1;
73 bootstrap threads $VERSION;
75 # why document 'new' then use 'create' in the tests!
78 # Preloaded methods go here.
85 threads - Perl extension allowing use of interpreter based threads from perl
92 print "Thread started\n";
95 my $thread = threads->create("start_thread","argument");
96 my $thread2 = $thread->create(sub { print "I am a thread"},"argument");
97 my $thread3 = async { foreach (@files) { ... } };
102 $thread = threads->self();
103 $thread = threads->object( $tid );
107 threads->self->tid();
115 Perl 5.6 introduced something called interpreter threads. Interpreter
116 threads are different from "5005threads" (the thread model of Perl
117 5.005) by creating a new perl interpreter per thread and not sharing
118 any data or state between threads by default.
120 Prior to perl 5.8 this has only been available to people embedding
121 perl and for emulating fork() on windows.
123 The threads API is loosely based on the old Thread.pm API. It is very
124 important to note that variables are not shared between threads, all
125 variables are per default thread local. To use shared variables one
126 must use threads::shared.
128 It is also important to note that you must enable threads by doing
129 C<use threads> as early as possible in the script itself and that it
130 is not possible to enable threading inside an C<eval "">, C<do>,
131 C<require>, or C<use>. In particular, if you are intending to share
132 variables with threads::shared, you must C<use threads> before you
133 C<use threads::shared> and C<threads> will emit a warning if you do
134 it the other way around.
138 =item $thread = threads->create(function, LIST)
140 This will create a new thread with the entry point function and give
141 it LIST as parameters. It will return the corresponding threads
142 object. The new() method is an alias for create().
146 This will wait for the corresponding thread to join. When the thread
147 finishes, join() will return the return values of the entry point
148 function. If the thread has been detached, an error will be thrown.
150 The context (scalar or list) of the thread creation is also the
151 context for join(). This means that if you intend to return an array
152 from a thread, you must use C<my ($thread) = threads->new(...)>, and
153 that if you intend to return a scalar, you must use C<my $thread = ...>.
155 If the program exits without all other threads having been either
156 joined or detached, then a warning will be issued. (A program exits
157 either because one of its threads explicitly calls exit(), or in the
158 case of the main thread, reaches the end of the main program file.)
161 =item $thread->detach
163 Will make the thread unjoinable, and cause any eventual return value
168 This will return the thread object for the current thread.
172 This will return the id of the thread. Thread IDs are integers, with
173 the main thread in a program being 0. Currently Perl assigns a unique
174 tid to every thread ever created in your program, assigning the first
175 thread to be created a tid of 1, and increasing the tid by 1 for each
176 new thread that's created.
178 NB the class method C<< threads->tid() >> is a quick way to get the
179 current thread id if you don't have your thread object handy.
181 =item threads->object( tid )
183 This will return the thread object for the thread associated with the
184 specified tid. Returns undef if there is no thread associated with the tid
185 or no tid is specified or the specified tid is undef.
187 =item threads->yield();
189 This is a suggestion to the OS to let this thread yield CPU time to other
190 threads. What actually happens is highly dependent upon the underlying
191 thread implementation.
193 You may do C<use threads qw(yield)> then use just a bare C<yield> in your
196 =item threads->list();
198 This will return a list of all non joined, non detached threads.
202 C<async> creates a thread to execute the block immediately following
203 it. This block is treated as an anonymous sub, and so must have a
204 semi-colon after the closing brace. Like C<< threads->new >>, C<async>
205 returns a thread object.
213 =item A thread exited while %d other threads were still running
215 A thread (not necessarily the main thread) exited while there were
216 still other threads running. Usually it's a good idea to first collect
217 the return values of the created threads by joining them, and only then
218 exit from the main thread.
224 The current implementation of threads has been an attempt to get
225 a correct threading system working that could be built on,
226 and optimized, in newer versions of perl.
228 Currently the overhead of creating a thread is rather large,
229 also the cost of returning values can be large. These are areas
230 were there most likely will be work done to optimize what data
231 that needs to be cloned.
237 =item Parent-Child threads.
239 On some platforms it might not be possible to destroy "parent"
240 threads while there are still existing child "threads".
242 This will possibly be fixed in later versions of perl.
246 The thread id is a 32 bit integer, it can potentially overflow.
247 This might be fixed in a later version of perl.
249 =item Returning objects
251 When you return an object the entire stash that the object is blessed
252 as well. This will lead to a large memory usage. The ideal situation
253 would be to detect the original stash if it existed.
255 =item Creating threads inside BEGIN blocks
257 Creating threads inside BEGIN blocks (or during the compilation phase
258 in general) does not work. (In Windows, trying to use fork() inside
259 BEGIN blocks is an equally losing proposition, since it has been
260 implemented in very much the same way as threads.)
262 =item PERL_OLD_SIGNALS are not threadsafe, will not be.
264 If your Perl has been built with PERL_OLD_SIGNALS (one has
265 to explicitly add that symbol to ccflags, see C<perl -V>),
266 signal handling is not threadsafe.
270 =head1 AUTHOR and COPYRIGHT
272 Arthur Bergman E<lt>sky at nanisky.comE<gt>
274 threads is released under the same license as Perl.
278 Richard Soderberg E<lt>perl at crystalflame.netE<gt>
279 Helping me out tons, trying to find reasons for races and other weird bugs!
281 Simon Cozens E<lt>simon at brecon.co.ukE<gt>
282 Being there to answer zillions of annoying questions
284 Rocco Caputo E<lt>troc at netrus.netE<gt>
286 Vipul Ved Prakash E<lt>mail at vipul.netE<gt>
287 Helping with debugging.
289 please join perl-ithreads@perl.org for more information
293 L<threads::shared>, L<perlthrtut>,
294 L<http://www.perl.com/pub/a/2002/06/11/threads.html>,
295 L<perlcall>, L<perlembed>, L<perlguts>