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 $VERSION = '1.01';
56 # || 0 to ensure compatibility with previous versions
57 sub equal { ($_[0]->tid == $_[1]->tid) || 0 }
59 # use "goto" trick to avoid pad problems from 5.8.1, should also be faster
60 sub async (&;@) { unshift @_,'threads'; goto &new }
63 return undef unless @_ > 1;
64 foreach (threads->list) {
65 return $_ if $_->tid == $_[1];
70 $threads::threads = 1;
72 bootstrap threads $VERSION;
74 # why document 'new' then use 'create' in the tests!
77 # Preloaded methods go here.
84 threads - Perl extension allowing use of interpreter based threads from perl
91 print "Thread started\n";
94 my $thread = threads->create("start_thread","argument");
95 my $thread2 = $thread->create(sub { print "I am a thread"},"argument");
96 my $thread3 = async { foreach (@files) { ... } };
101 $thread = threads->self();
102 $thread = threads->object( $tid );
106 threads->self->tid();
114 Perl 5.6 introduced something called interpreter threads. Interpreter
115 threads are different from "5005threads" (the thread model of Perl
116 5.005) by creating a new perl interpreter per thread and not sharing
117 any data or state between threads by default.
119 Prior to perl 5.8 this has only been available to people embedding
120 perl and for emulating fork() on windows.
122 The threads API is loosely based on the old Thread.pm API. It is very
123 important to note that variables are not shared between threads, all
124 variables are per default thread local. To use shared variables one
125 must use threads::shared.
127 It is also important to note that you must enable threads by doing
128 C<use threads> as early as possible in the script itself and that it
129 is not possible to enable threading inside an C<eval "">, C<do>,
130 C<require>, or C<use>. In particular, if you are intending to share
131 variables with threads::shared, you must C<use threads> before you
132 C<use threads::shared> and C<threads> will emit a warning if you do
133 it the other way around.
137 =item $thread = threads->create(function, LIST)
139 This will create a new thread with the entry point function and give
140 it LIST as parameters. It will return the corresponding threads
141 object. The new() method is an alias for create().
145 This will wait for the corresponding thread to join. When the thread
146 finishes, join() will return the return values of the entry point
147 function. If the thread has been detached, an error will be thrown.
149 The context (scalar or list) of the thread creation is also the
150 context for join(). This means that if you intend to return an array
151 from a thread, you must use C<my ($thread) = threads->new(...)>, and
152 that if you intend to return a scalar, you must use C<my $thread = ...>.
154 If the program exits without all other threads having been either
155 joined or detached, then a warning will be issued. (A program exits
156 either because one of its threads explicitly calls exit(), or in the
157 case of the main thread, reaches the end of the main program file.)
160 =item $thread->detach
162 Will make the thread unjoinable, and cause any eventual return value
167 This will return the thread object for the current thread.
171 This will return the id of the thread. Thread IDs are integers, with
172 the main thread in a program being 0. Currently Perl assigns a unique
173 tid to every thread ever created in your program, assigning the first
174 thread to be created a tid of 1, and increasing the tid by 1 for each
175 new thread that's created.
177 NB the class method C<< threads->tid() >> is a quick way to get the
178 current thread id if you don't have your thread object handy.
180 =item threads->object( tid )
182 This will return the thread object for the thread associated with the
183 specified tid. Returns undef if there is no thread associated with the tid
184 or no tid is specified or the specified tid is undef.
186 =item threads->yield();
188 This is a suggestion to the OS to let this thread yield CPU time to other
189 threads. What actually happens is highly dependent upon the underlying
190 thread implementation.
192 You may do C<use threads qw(yield)> then use just a bare C<yield> in your
195 =item threads->list();
197 This will return a list of all non joined, non detached threads.
201 C<async> creates a thread to execute the block immediately following
202 it. This block is treated as an anonymous sub, and so must have a
203 semi-colon after the closing brace. Like C<< threads->new >>, C<async>
204 returns a thread object.
212 =item A thread exited while %d other threads were still running
214 A thread (not necessarily the main thread) exited while there were
215 still other threads running. Usually it's a good idea to first collect
216 the return values of the created threads by joining them, and only then
217 exit from the main thread.
223 The current implementation of threads has been an attempt to get
224 a correct threading system working that could be built on,
225 and optimized, in newer versions of perl.
227 Currently the overhead of creating a thread is rather large,
228 also the cost of returning values can be large. These are areas
229 were there most likely will be work done to optimize what data
230 that needs to be cloned.
236 =item Parent-Child threads.
238 On some platforms it might not be possible to destroy "parent"
239 threads while there are still existing child "threads".
241 This will possibly be fixed in later versions of perl.
245 The thread id is a 32 bit integer, it can potentially overflow.
246 This might be fixed in a later version of perl.
248 =item Returning objects
250 When you return an object the entire stash that the object is blessed
251 as well. This will lead to a large memory usage. The ideal situation
252 would be to detect the original stash if it existed.
254 =item Creating threads inside BEGIN blocks
256 Creating threads inside BEGIN blocks (or during the compilation phase
257 in general) does not work. (In Windows, trying to use fork() inside
258 BEGIN blocks is an equally losing proposition, since it has been
259 implemented in very much the same way as threads.)
261 =item PERL_OLD_SIGNALS are not threadsafe, will not be.
263 If your Perl has been built with PERL_OLD_SIGNALS (one has
264 to explicitly add that symbol to ccflags, see C<perl -V>),
265 signal handling is not threadsafe.
267 =item Detached threads on Windows
269 These aren't yet supported (as of perl 5.8.3), as they may lead to
270 memory access violation problems.
274 =head1 AUTHOR and COPYRIGHT
276 Arthur Bergman E<lt>sky at nanisky.comE<gt>
278 threads is released under the same license as Perl.
282 Richard Soderberg E<lt>perl at crystalflame.netE<gt>
283 Helping me out tons, trying to find reasons for races and other weird bugs!
285 Simon Cozens E<lt>simon at brecon.co.ukE<gt>
286 Being there to answer zillions of annoying questions
288 Rocco Caputo E<lt>troc at netrus.netE<gt>
290 Vipul Ved Prakash E<lt>mail at vipul.netE<gt>
291 Helping with debugging.
293 please join perl-ithreads@perl.org for more information
297 L<threads::shared>, L<perlthrtut>,
298 L<http://www.perl.com/pub/a/2002/06/11/threads.html>,
299 L<perlcall>, L<perlembed>, L<perlguts>