Commit | Line | Data |
47ba8780 |
1 | package threads; |
2 | |
32419a4c |
3 | use 5.008; |
fcea4b7c |
4 | |
47ba8780 |
5 | use strict; |
6 | use warnings; |
73e09c8f |
7 | |
18b9e6f5 |
8 | our $VERSION = '1.62'; |
fcea4b7c |
9 | my $XS_VERSION = $VERSION; |
10 | $VERSION = eval $VERSION; |
73e09c8f |
11 | |
73e09c8f |
12 | |
fcea4b7c |
13 | BEGIN { |
14 | # Verify this Perl supports threads |
15 | use Config; |
16 | if (! $Config{useithreads}) { |
17 | die("This Perl not built to support threads\n"); |
73e09c8f |
18 | } |
47ba8780 |
19 | |
fcea4b7c |
20 | # Complain if 'threads' is loaded after 'threads::shared' |
21 | if ($threads::shared::threads_shared) { |
22 | warn <<'_MSG_'; |
23 | Warning, threads::shared has already been loaded. To |
24 | enable shared variables, 'use threads' must be called |
25 | before threads::shared or any module that uses it. |
26 | _MSG_ |
27 | } |
dab065ea |
28 | } |
29 | |
fc04eb16 |
30 | |
45cd5be7 |
31 | # Declare that we have been loaded |
32 | $threads::threads = 1; |
33 | |
0f1612a7 |
34 | # Load the XS code |
35 | require XSLoader; |
fcea4b7c |
36 | XSLoader::load('threads', $XS_VERSION); |
47ba8780 |
37 | |
47ba8780 |
38 | |
0f1612a7 |
39 | ### Export ### |
47ba8780 |
40 | |
0f1612a7 |
41 | sub import |
42 | { |
43 | my $class = shift; # Not used |
44 | |
45 | # Exported subroutines |
46 | my @EXPORT = qw(async); |
47 | |
48 | # Handle args |
49 | while (my $sym = shift) { |
6ebc233e |
50 | if ($sym =~ /^(?:stack|exit)/i) { |
51 | if (defined(my $arg = shift)) { |
52 | if ($sym =~ /^stack/i) { |
53 | threads->set_stack_size($arg); |
54 | } else { |
55 | $threads::thread_exit_only = $arg =~ /^thread/i; |
56 | } |
57 | } else { |
58 | require Carp; |
59 | Carp::croak("threads: Missing argument for option: $sym"); |
60 | } |
69a9b4b8 |
61 | |
3ab14376 |
62 | } elsif ($sym =~ /^str/i) { |
63 | import overload ('""' => \&tid); |
64 | |
18b9e6f5 |
65 | } elsif ($sym =~ /^(?::all|yield)$/) { |
0f1612a7 |
66 | push(@EXPORT, qw(yield)); |
67 | |
68 | } else { |
de42e62a |
69 | require Carp; |
70 | Carp::croak("threads: Unknown import option: $sym"); |
0f1612a7 |
71 | } |
72 | } |
73 | |
74 | # Export subroutine names |
75 | my $caller = caller(); |
76 | foreach my $sym (@EXPORT) { |
77 | no strict 'refs'; |
78 | *{$caller.'::'.$sym} = \&{$sym}; |
79 | } |
514612b7 |
80 | |
81 | # Set stack size via environment variable |
82 | if (exists($ENV{'PERL5_ITHREADS_STACK_SIZE'})) { |
83 | threads->set_stack_size($ENV{'PERL5_ITHREADS_STACK_SIZE'}); |
84 | } |
0f1612a7 |
85 | } |
86 | |
87 | |
88 | ### Methods, etc. ### |
47ba8780 |
89 | |
69a9b4b8 |
90 | # Exit from a thread (only) |
4dcb9e53 |
91 | sub exit |
92 | { |
69a9b4b8 |
93 | my ($class, $status) = @_; |
94 | if (! defined($status)) { |
95 | $status = 0; |
96 | } |
97 | |
98 | # Class method only |
99 | if (ref($class)) { |
100 | require Carp; |
da140a40 |
101 | Carp::croak('Usage: threads->exit(status)'); |
69a9b4b8 |
102 | } |
103 | |
104 | $class->set_thread_exit_only(1); |
105 | CORE::exit($status); |
4dcb9e53 |
106 | } |
107 | |
ead32952 |
108 | # 'Constant' args for threads->list() |
109 | sub threads::all { } |
110 | sub threads::running { 1 } |
111 | sub threads::joinable { 0 } |
112 | |
f4cc38af |
113 | # 'new' is an alias for 'create' |
114 | *new = \&create; |
68795e93 |
115 | |
fcea4b7c |
116 | # 'async' is a function alias for the 'threads->create()' method |
117 | sub async (&;@) |
118 | { |
119 | unshift(@_, 'threads'); |
120 | # Use "goto" trick to avoid pad problems from 5.8.1 (fixed in 5.8.2) |
121 | goto &create; |
122 | } |
123 | |
124 | # Thread object equality checking |
125 | use overload ( |
126 | '==' => \&equal, |
127 | '!=' => sub { ! equal(@_) }, |
128 | 'fallback' => 1 |
129 | ); |
130 | |
47ba8780 |
131 | 1; |
0f1612a7 |
132 | |
47ba8780 |
133 | __END__ |
134 | |
135 | =head1 NAME |
136 | |
0f1612a7 |
137 | threads - Perl interpreter-based threads |
138 | |
139 | =head1 VERSION |
140 | |
18b9e6f5 |
141 | This document describes threads version 1.62 |
47ba8780 |
142 | |
143 | =head1 SYNOPSIS |
144 | |
3ab14376 |
145 | use threads ('yield', |
146 | 'stack_size' => 64*4096, |
147 | 'exit' => 'threads_only', |
148 | 'stringify'); |
47ba8780 |
149 | |
38875929 |
150 | sub start_thread { |
0f1612a7 |
151 | my @args = @_; |
9d9ff5b1 |
152 | print('Thread started: ', join(' ', @args), "\n"); |
38875929 |
153 | } |
fea7688c |
154 | my $thr = threads->create('start_thread', 'argument'); |
155 | $thr->join(); |
0f1612a7 |
156 | |
157 | threads->create(sub { print("I am a thread\n"); })->join(); |
47ba8780 |
158 | |
fea7688c |
159 | my $thr2 = async { foreach (@files) { ... } }; |
160 | $thr2->join(); |
955c272e |
161 | if (my $err = $thr2->error()) { |
162 | warn("Thread error: $err\n"); |
163 | } |
0f1612a7 |
164 | |
9d9ff5b1 |
165 | # Invoke thread in list context (implicit) so it can return a list |
0f1612a7 |
166 | my ($thr) = threads->create(sub { return (qw/a b c/); }); |
9d9ff5b1 |
167 | # or specify list context explicitly |
168 | my $thr = threads->create({'context' => 'list'}, |
169 | sub { return (qw/a b c/); }); |
0f1612a7 |
170 | my @results = $thr->join(); |
47ba8780 |
171 | |
fea7688c |
172 | $thr->detach(); |
47ba8780 |
173 | |
69a9b4b8 |
174 | # Get a thread's object |
fea7688c |
175 | $thr = threads->self(); |
176 | $thr = threads->object($tid); |
11c51ed3 |
177 | |
69a9b4b8 |
178 | # Get a thread's ID |
0f1612a7 |
179 | $tid = threads->tid(); |
fea7688c |
180 | $tid = $thr->tid(); |
3ab14376 |
181 | $tid = "$thr"; |
47ba8780 |
182 | |
69a9b4b8 |
183 | # Give other threads a chance to run |
38875929 |
184 | threads->yield(); |
0f1612a7 |
185 | yield(); |
186 | |
69a9b4b8 |
187 | # Lists of non-detached threads |
0f1612a7 |
188 | my @threads = threads->list(); |
fcea4b7c |
189 | my $thread_count = threads->list(); |
f9dff5f5 |
190 | |
ead32952 |
191 | my @running = threads->list(threads::running); |
192 | my @joinable = threads->list(threads::joinable); |
193 | |
69a9b4b8 |
194 | # Test thread objects |
0f1612a7 |
195 | if ($thr1 == $thr2) { |
196 | ... |
197 | } |
678a9b6c |
198 | |
69a9b4b8 |
199 | # Manage thread stack size |
514612b7 |
200 | $stack_size = threads->get_stack_size(); |
201 | $old_size = threads->set_stack_size(32*4096); |
202 | |
9d9ff5b1 |
203 | # Create a thread with a specific context and stack size |
204 | my $thr = threads->create({ 'context' => 'list', |
69a9b4b8 |
205 | 'stack_size' => 32*4096, |
206 | 'exit' => 'thread_only' }, |
9d9ff5b1 |
207 | \&foo); |
ead32952 |
208 | |
209 | # Get thread's context |
210 | my $wantarray = $thr->wantarray(); |
211 | |
212 | # Check thread's state |
213 | if ($thr->is_running()) { |
214 | sleep(1); |
215 | } |
216 | if ($thr->is_joinable()) { |
217 | $thr->join(); |
218 | } |
9d9ff5b1 |
219 | |
69a9b4b8 |
220 | # Send a signal to a thread |
c0003851 |
221 | $thr->kill('SIGUSR1'); |
222 | |
69a9b4b8 |
223 | # Exit a thread |
4dcb9e53 |
224 | threads->exit(); |
225 | |
47ba8780 |
226 | =head1 DESCRIPTION |
227 | |
fc04eb16 |
228 | Perl 5.6 introduced something called interpreter threads. Interpreter threads |
229 | are different from I<5005threads> (the thread model of Perl 5.005) by creating |
230 | a new Perl interpreter per thread, and not sharing any data or state between |
231 | threads by default. |
11c51ed3 |
232 | |
fc04eb16 |
233 | Prior to Perl 5.8, this has only been available to people embedding Perl, and |
234 | for emulating fork() on Windows. |
11c51ed3 |
235 | |
fc04eb16 |
236 | The I<threads> API is loosely based on the old Thread.pm API. It is very |
237 | important to note that variables are not shared between threads, all variables |
6ebc233e |
238 | are by default thread local. To use shared variables one must also use |
239 | L<threads::shared>: |
240 | |
241 | use threads; |
242 | use threads::shared; |
11c51ed3 |
243 | |
fc04eb16 |
244 | It is also important to note that you must enable threads by doing C<use |
245 | threads> as early as possible in the script itself, and that it is not |
246 | possible to enable threading inside an C<eval "">, C<do>, C<require>, or |
247 | C<use>. In particular, if you are intending to share variables with |
248 | L<threads::shared>, you must C<use threads> before you C<use threads::shared>. |
249 | (C<threads> will emit a warning if you do it the other way around.) |
47ba8780 |
250 | |
251 | =over |
252 | |
0f1612a7 |
253 | =item $thr = threads->create(FUNCTION, ARGS) |
47ba8780 |
254 | |
0f1612a7 |
255 | This will create a new thread that will begin execution with the specified |
256 | entry point function, and give it the I<ARGS> list as parameters. It will |
257 | return the corresponding threads object, or C<undef> if thread creation failed. |
47ba8780 |
258 | |
0f1612a7 |
259 | I<FUNCTION> may either be the name of a function, an anonymous subroutine, or |
260 | a code ref. |
47ba8780 |
261 | |
0f1612a7 |
262 | my $thr = threads->create('func_name', ...); |
263 | # or |
264 | my $thr = threads->create(sub { ... }, ...); |
265 | # or |
266 | my $thr = threads->create(\&func, ...); |
93512b4d |
267 | |
0f1612a7 |
268 | The C<-E<gt>new()> method is an alias for C<-E<gt>create()>. |
269 | |
270 | =item $thr->join() |
271 | |
272 | This will wait for the corresponding thread to complete its execution. When |
273 | the thread finishes, C<-E<gt>join()> will return the return value(s) of the |
274 | entry point function. |
275 | |
9d9ff5b1 |
276 | The context (void, scalar or list) for the return value(s) for C<-E<gt>join()> |
277 | is determined at the time of thread creation. |
0f1612a7 |
278 | |
9d9ff5b1 |
279 | # Create thread in list context (implicit) |
0f1612a7 |
280 | my ($thr1) = threads->create(sub { |
281 | my @results = qw(a b c); |
282 | return (@results); |
9d9ff5b1 |
283 | }); |
284 | # or (explicit) |
285 | my $thr1 = threads->create({'context' => 'list'}, |
286 | sub { |
287 | my @results = qw(a b c); |
288 | return (@results); |
289 | }); |
0f1612a7 |
290 | # Retrieve list results from thread |
291 | my @res1 = $thr1->join(); |
292 | |
9d9ff5b1 |
293 | # Create thread in scalar context (implicit) |
0f1612a7 |
294 | my $thr2 = threads->create(sub { |
295 | my $result = 42; |
296 | return ($result); |
9d9ff5b1 |
297 | }); |
0f1612a7 |
298 | # Retrieve scalar result from thread |
299 | my $res2 = $thr2->join(); |
300 | |
9d9ff5b1 |
301 | # Create a thread in void context (explicit) |
302 | my $thr3 = threads->create({'void' => 1}, |
303 | sub { print("Hello, world\n"); }); |
304 | # Join the thread in void context (i.e., no return value) |
305 | $thr3->join(); |
306 | |
307 | See L</"THREAD CONTEXT"> for more details. |
308 | |
4dcb9e53 |
309 | If the program exits without all threads having either been joined or |
310 | detached, then a warning will be issued. |
93512b4d |
311 | |
fcea4b7c |
312 | Calling C<-E<gt>join()> or C<-E<gt>detach()> on an already joined thread will |
313 | cause an error to be thrown. |
47ba8780 |
314 | |
fcea4b7c |
315 | =item $thr->detach() |
47ba8780 |
316 | |
fcea4b7c |
317 | Makes the thread unjoinable, and causes any eventual return value to be |
4dcb9e53 |
318 | discarded. When the program exits, any detached threads that are still |
319 | running are silently terminated. |
320 | |
321 | If the program exits without all threads having either been joined or |
322 | detached, then a warning will be issued. |
fcea4b7c |
323 | |
324 | Calling C<-E<gt>join()> or C<-E<gt>detach()> on an already detached thread |
325 | will cause an error to be thrown. |
0f1612a7 |
326 | |
327 | =item threads->detach() |
328 | |
329 | Class method that allows a thread to detach itself. |
330 | |
fcea4b7c |
331 | =item threads->self() |
47ba8780 |
332 | |
fcea4b7c |
333 | Class method that allows a thread to obtain its own I<threads> object. |
47ba8780 |
334 | |
0f1612a7 |
335 | =item $thr->tid() |
336 | |
337 | Returns the ID of the thread. Thread IDs are unique integers with the main |
338 | thread in a program being 0, and incrementing by 1 for every thread created. |
47ba8780 |
339 | |
0f1612a7 |
340 | =item threads->tid() |
38875929 |
341 | |
0f1612a7 |
342 | Class method that allows a thread to obtain its own ID. |
47ba8780 |
343 | |
3ab14376 |
344 | =item "$thr" |
345 | |
346 | If you add the C<stringify> import option to your C<use threads> declaration, |
347 | then using a threads object in a string or a string context (e.g., as a hash |
348 | key) will cause its ID to be used as the value: |
349 | |
5c6ff896 |
350 | use threads qw(stringify); |
3ab14376 |
351 | |
5c6ff896 |
352 | my $thr = threads->create(...); |
353 | print("Thread $thr started...\n"); # Prints out: Thread 1 started... |
3ab14376 |
354 | |
0f1612a7 |
355 | =item threads->object($tid) |
8c9849ff |
356 | |
0f1612a7 |
357 | This will return the I<threads> object for the I<active> thread associated |
358 | with the specified thread ID. Returns C<undef> if there is no thread |
359 | associated with the TID, if the thread is joined or detached, if no TID is |
360 | specified or if the specified TID is undef. |
8c9849ff |
361 | |
fcea4b7c |
362 | =item threads->yield() |
f9dff5f5 |
363 | |
38875929 |
364 | This is a suggestion to the OS to let this thread yield CPU time to other |
365 | threads. What actually happens is highly dependent upon the underlying |
366 | thread implementation. |
f9dff5f5 |
367 | |
fcea4b7c |
368 | You may do C<use threads qw(yield)>, and then just use C<yield()> in your |
70f2e746 |
369 | code. |
370 | |
f4cc38af |
371 | =item threads->list() |
678a9b6c |
372 | |
ead32952 |
373 | =item threads->list(threads::all) |
374 | |
375 | =item threads->list(threads::running) |
376 | |
377 | =item threads->list(threads::joinable) |
378 | |
379 | With no arguments (or using C<threads::all>) and in a list context, returns a |
380 | list of all non-joined, non-detached I<threads> objects. In a scalar context, |
381 | returns a count of the same. |
382 | |
383 | With a I<true> argument (using C<threads::running>), returns a list of all |
8718f9a1 |
384 | non-joined, non-detached I<threads> objects that are still running. |
ead32952 |
385 | |
386 | With a I<false> argument (using C<threads::joinable>), returns a list of all |
387 | non-joined, non-detached I<threads> objects that have finished running (i.e., |
388 | for which C<-E<gt>join()> will not I<block>). |
678a9b6c |
389 | |
0f1612a7 |
390 | =item $thr1->equal($thr2) |
391 | |
392 | Tests if two threads objects are the same thread or not. This is overloaded |
fcea4b7c |
393 | to the more natural forms: |
0f1612a7 |
394 | |
395 | if ($thr1 == $thr2) { |
396 | print("Threads are the same\n"); |
397 | } |
fcea4b7c |
398 | # or |
399 | if ($thr1 != $thr2) { |
400 | print("Threads differ\n"); |
401 | } |
0f1612a7 |
402 | |
403 | (Thread comparison is based on thread IDs.) |
404 | |
386c44e5 |
405 | =item async BLOCK; |
406 | |
407 | C<async> creates a thread to execute the block immediately following |
fcea4b7c |
408 | it. This block is treated as an anonymous subroutine, and so must have a |
5cbb7319 |
409 | semicolon after the closing brace. Like C<threads-E<gt>create()>, C<async> |
fcea4b7c |
410 | returns a I<threads> object. |
386c44e5 |
411 | |
955c272e |
412 | =item $thr->error() |
413 | |
414 | Threads are executed in an C<eval> context. This method will return C<undef> |
415 | if the thread terminates I<normally>. Otherwise, it returns the value of |
416 | C<$@> associated with the thread's execution status in its C<eval> context. |
417 | |
f4cc38af |
418 | =item $thr->_handle() |
419 | |
420 | This I<private> method returns the memory location of the internal thread |
fcea4b7c |
421 | structure associated with a threads object. For Win32, this is a pointer to |
422 | the C<HANDLE> value returned by C<CreateThread> (i.e., C<HANDLE *>); for other |
423 | platforms, it is a pointer to the C<pthread_t> structure used in the |
404aaa48 |
424 | C<pthread_create> call (i.e., C<pthread_t *>). |
f4cc38af |
425 | |
426 | This method is of no use for general Perl threads programming. Its intent is |
427 | to provide other (XS-based) thread modules with the capability to access, and |
428 | possibly manipulate, the underlying thread structure associated with a Perl |
429 | thread. |
430 | |
431 | =item threads->_handle() |
432 | |
433 | Class method that allows a thread to obtain its own I<handle>. |
434 | |
47ba8780 |
435 | =back |
436 | |
69a9b4b8 |
437 | =head1 EXITING A THREAD |
438 | |
439 | The usual method for terminating a thread is to |
440 | L<return()|perlfunc/"return EXPR"> from the entry point function with the |
441 | appropriate return value(s). |
442 | |
443 | =over |
444 | |
445 | =item threads->exit() |
446 | |
447 | If needed, a thread can be exited at any time by calling |
448 | C<threads-E<gt>exit()>. This will cause the thread to return C<undef> in a |
449 | scalar context, or the empty list in a list context. |
450 | |
451 | When called from the I<main> thread, this behaves the same as C<exit(0)>. |
452 | |
453 | =item threads->exit(status) |
454 | |
455 | When called from a thread, this behaves like C<threads-E<gt>exit()> (i.e., the |
456 | exit status code is ignored). |
457 | |
458 | When called from the I<main> thread, this behaves the same as C<exit(status)>. |
459 | |
460 | =item die() |
461 | |
462 | Calling C<die()> in a thread indicates an abnormal exit for the thread. Any |
463 | C<$SIG{__DIE__}> handler in the thread will be called first, and then the |
464 | thread will exit with a warning message that will contain any arguments passed |
465 | in the C<die()> call. |
466 | |
467 | =item exit(status) |
468 | |
469 | Calling L<exit()|perlfunc/"exit EXPR"> inside a thread causes the whole |
470 | application to terminate. Because of this, the use of C<exit()> inside |
471 | threaded code, or in modules that might be used in threaded applications, is |
472 | strongly discouraged. |
473 | |
474 | If C<exit()> really is needed, then consider using the following: |
475 | |
60bd5ef6 |
476 | threads->exit() if threads->can('exit'); # Thread friendly |
69a9b4b8 |
477 | exit(status); |
478 | |
5cbb7319 |
479 | =item use threads 'exit' => 'threads_only' |
69a9b4b8 |
480 | |
481 | This globally overrides the default behavior of calling C<exit()> inside a |
482 | thread, and effectively causes such calls to behave the same as |
483 | C<threads-E<gt>exit()>. In other words, with this setting, calling C<exit()> |
484 | causes only the thread to terminate. |
485 | |
486 | Because of its global effect, this setting should not be used inside modules |
487 | or the like. |
488 | |
489 | The I<main> thread is unaffected by this setting. |
490 | |
491 | =item threads->create({'exit' => 'thread_only'}, ...) |
492 | |
493 | This overrides the default behavior of C<exit()> inside the newly created |
494 | thread only. |
495 | |
496 | =item $thr->set_thread_exit_only(boolean) |
497 | |
498 | This can be used to change the I<exit thread only> behavior for a thread after |
5cbb7319 |
499 | it has been created. With a I<true> argument, C<exit()> will cause only the |
500 | thread to exit. With a I<false> argument, C<exit()> will terminate the |
69a9b4b8 |
501 | application. |
502 | |
503 | The I<main> thread is unaffected by this call. |
504 | |
505 | =item threads->set_thread_exit_only(boolean) |
506 | |
5cbb7319 |
507 | Class method for use inside a thread to change its own behavior for C<exit()>. |
69a9b4b8 |
508 | |
509 | The I<main> thread is unaffected by this call. |
510 | |
511 | =back |
512 | |
ead32952 |
513 | =head1 THREAD STATE |
514 | |
515 | The following boolean methods are useful in determining the I<state> of a |
516 | thread. |
517 | |
518 | =over |
519 | |
520 | =item $thr->is_running() |
521 | |
522 | Returns true if a thread is still running (i.e., if its entry point function |
5cbb7319 |
523 | has not yet finished or exited). |
ead32952 |
524 | |
525 | =item $thr->is_joinable() |
526 | |
527 | Returns true if the thread has finished running, is not detached and has not |
5cbb7319 |
528 | yet been joined. In other words, the thread is ready to be joined, and a call |
529 | to C<$thr-E<gt>join()> will not I<block>. |
ead32952 |
530 | |
531 | =item $thr->is_detached() |
532 | |
533 | Returns true if the thread has been detached. |
534 | |
535 | =item threads->is_detached() |
536 | |
537 | Class method that allows a thread to determine whether or not it is detached. |
538 | |
539 | =back |
540 | |
9d9ff5b1 |
541 | =head1 THREAD CONTEXT |
542 | |
543 | As with subroutines, the type of value returned from a thread's entry point |
544 | function may be determined by the thread's I<context>: list, scalar or void. |
545 | The thread's context is determined at thread creation. This is necessary so |
546 | that the context is available to the entry point function via |
206f4df7 |
547 | L<wantarray()|perlfunc/"wantarray">. The thread may then specify a value of |
9d9ff5b1 |
548 | the appropriate type to be returned from C<-E<gt>join()>. |
549 | |
550 | =head2 Explicit context |
551 | |
552 | Because thread creation and thread joining may occur in different contexts, it |
553 | may be desirable to state the context explicitly to the thread's entry point |
5cbb7319 |
554 | function. This may be done by calling C<-E<gt>create()> with a hash reference |
9d9ff5b1 |
555 | as the first argument: |
556 | |
557 | my $thr = threads->create({'context' => 'list'}, \&foo); |
558 | ... |
559 | my @results = $thr->join(); |
560 | |
561 | In the above, the threads object is returned to the parent thread in scalar |
562 | context, and the thread's entry point function C<foo> will be called in list |
da140a40 |
563 | (array) context such that the parent thread can receive a list (array) from |
564 | the C<-E<gt>join()> call. (C<'array'> is synonymous with C<'list'>.) |
565 | |
566 | Similarly, if you need the threads object, but your thread will not be |
9d9ff5b1 |
567 | returning a value (i.e., I<void> context), you would do the following: |
568 | |
569 | my $thr = threads->create({'context' => 'void'}, \&foo); |
570 | ... |
571 | $thr->join(); |
572 | |
5cbb7319 |
573 | The context type may also be used as the I<key> in the hash reference followed |
9d9ff5b1 |
574 | by a I<true> value: |
575 | |
576 | threads->create({'scalar' => 1}, \&foo); |
577 | ... |
578 | my ($thr) = threads->list(); |
579 | my $result = $thr->join(); |
580 | |
581 | =head2 Implicit context |
582 | |
583 | If not explicitly stated, the thread's context is implied from the context |
584 | of the C<-E<gt>create()> call: |
585 | |
586 | # Create thread in list context |
587 | my ($thr) = threads->create(...); |
588 | |
589 | # Create thread in scalar context |
590 | my $thr = threads->create(...); |
591 | |
592 | # Create thread in void context |
593 | threads->create(...); |
594 | |
ead32952 |
595 | =head2 $thr->wantarray() |
596 | |
597 | This returns the thread's context in the same manner as |
598 | L<wantarray()|perlfunc/"wantarray">. |
599 | |
600 | =head2 threads->wantarray() |
601 | |
5cbb7319 |
602 | Class method to return the current thread's context. This returns the same |
603 | value as running L<wantarray()|perlfunc/"wantarray"> inside the current |
604 | thread's entry point function. |
ead32952 |
605 | |
514612b7 |
606 | =head1 THREAD STACK SIZE |
607 | |
608 | The default per-thread stack size for different platforms varies |
609 | significantly, and is almost always far more than is needed for most |
610 | applications. On Win32, Perl's makefile explicitly sets the default stack to |
611 | 16 MB; on most other platforms, the system default is used, which again may be |
612 | much larger than is needed. |
613 | |
614 | By tuning the stack size to more accurately reflect your application's needs, |
615 | you may significantly reduce your application's memory usage, and increase the |
616 | number of simultaneously running threads. |
617 | |
5cbb7319 |
618 | Note that on Windows, address space allocation granularity is 64 KB, |
619 | therefore, setting the stack smaller than that on Win32 Perl will not save any |
620 | more memory. |
514612b7 |
621 | |
622 | =over |
623 | |
624 | =item threads->get_stack_size(); |
625 | |
626 | Returns the current default per-thread stack size. The default is zero, which |
627 | means the system default stack size is currently in use. |
628 | |
629 | =item $size = $thr->get_stack_size(); |
630 | |
631 | Returns the stack size for a particular thread. A return value of zero |
632 | indicates the system default stack size was used for the thread. |
633 | |
634 | =item $old_size = threads->set_stack_size($new_size); |
635 | |
636 | Sets a new default per-thread stack size, and returns the previous setting. |
637 | |
638 | Some platforms have a minimum thread stack size. Trying to set the stack size |
639 | below this value will result in a warning, and the minimum stack size will be |
640 | used. |
641 | |
642 | Some Linux platforms have a maximum stack size. Setting too large of a stack |
643 | size will cause thread creation to fail. |
644 | |
645 | If needed, C<$new_size> will be rounded up to the next multiple of the memory |
646 | page size (usually 4096 or 8192). |
647 | |
648 | Threads created after the stack size is set will then either call |
649 | C<pthread_attr_setstacksize()> I<(for pthreads platforms)>, or supply the |
650 | stack size to C<CreateThread()> I<(for Win32 Perl)>. |
651 | |
652 | (Obviously, this call does not affect any currently extant threads.) |
653 | |
654 | =item use threads ('stack_size' => VALUE); |
655 | |
656 | This sets the default per-thread stack size at the start of the application. |
657 | |
658 | =item $ENV{'PERL5_ITHREADS_STACK_SIZE'} |
659 | |
660 | The default per-thread stack size may be set at the start of the application |
661 | through the use of the environment variable C<PERL5_ITHREADS_STACK_SIZE>: |
662 | |
663 | PERL5_ITHREADS_STACK_SIZE=1048576 |
664 | export PERL5_ITHREADS_STACK_SIZE |
665 | perl -e'use threads; print(threads->get_stack_size(), "\n")' |
666 | |
667 | This value overrides any C<stack_size> parameter given to C<use threads>. Its |
668 | primary purpose is to permit setting the per-thread stack size for legacy |
669 | threaded applications. |
670 | |
671 | =item threads->create({'stack_size' => VALUE}, FUNCTION, ARGS) |
672 | |
5cbb7319 |
673 | To specify a particular stack size for any individual thread, call |
674 | C<-E<gt>create()> with a hash reference as the first argument: |
9d9ff5b1 |
675 | |
676 | my $thr = threads->create({'stack_size' => 32*4096}, \&foo, @args); |
514612b7 |
677 | |
678 | =item $thr2 = $thr1->create(FUNCTION, ARGS) |
679 | |
680 | This creates a new thread (C<$thr2>) that inherits the stack size from an |
681 | existing thread (C<$thr1>). This is shorthand for the following: |
682 | |
683 | my $stack_size = $thr1->get_stack_size(); |
684 | my $thr2 = threads->create({'stack_size' => $stack_size}, FUNCTION, ARGS); |
685 | |
686 | =back |
687 | |
c0003851 |
688 | =head1 THREAD SIGNALLING |
689 | |
9d9ff5b1 |
690 | When safe signals is in effect (the default behavior - see L</"Unsafe signals"> |
1152d448 |
691 | for more details), then signals may be sent and acted upon by individual |
692 | threads. |
c0003851 |
693 | |
694 | =over 4 |
695 | |
696 | =item $thr->kill('SIG...'); |
697 | |
698 | Sends the specified signal to the thread. Signal names and (positive) signal |
699 | numbers are the same as those supported by |
700 | L<kill()|perlfunc/"kill SIGNAL, LIST">. For example, 'SIGTERM', 'TERM' and |
701 | (depending on the OS) 15 are all valid arguments to C<-E<gt>kill()>. |
702 | |
703 | Returns the thread object to allow for method chaining: |
704 | |
705 | $thr->kill('SIG...')->join(); |
706 | |
707 | =back |
708 | |
709 | Signal handlers need to be set up in the threads for the signals they are |
710 | expected to act upon. Here's an example for I<cancelling> a thread: |
711 | |
712 | use threads; |
713 | |
c0003851 |
714 | sub thr_func |
715 | { |
716 | # Thread 'cancellation' signal handler |
c608f8c0 |
717 | $SIG{'KILL'} = sub { threads->exit(); }; |
c0003851 |
718 | |
719 | ... |
720 | } |
721 | |
722 | # Create a thread |
723 | my $thr = threads->create('thr_func'); |
724 | |
725 | ... |
726 | |
727 | # Signal the thread to terminate, and then detach |
728 | # it so that it will get cleaned up automatically |
729 | $thr->kill('KILL')->detach(); |
730 | |
404aaa48 |
731 | Here's another simplistic example that illustrates the use of thread |
732 | signalling in conjunction with a semaphore to provide rudimentary I<suspend> |
733 | and I<resume> capabilities: |
c0003851 |
734 | |
735 | use threads; |
736 | use Thread::Semaphore; |
737 | |
738 | sub thr_func |
739 | { |
740 | my $sema = shift; |
741 | |
742 | # Thread 'suspend/resume' signal handler |
743 | $SIG{'STOP'} = sub { |
744 | $sema->down(); # Thread suspended |
745 | $sema->up(); # Thread resumes |
746 | }; |
747 | |
748 | ... |
749 | } |
750 | |
5cbb7319 |
751 | # Create a semaphore and pass it to a thread |
c0003851 |
752 | my $sema = Thread::Semaphore->new(); |
753 | my $thr = threads->create('thr_func', $sema); |
754 | |
755 | # Suspend the thread |
756 | $sema->down(); |
757 | $thr->kill('STOP'); |
758 | |
759 | ... |
760 | |
761 | # Allow the thread to continue |
762 | $sema->up(); |
763 | |
404aaa48 |
764 | CAVEAT: The thread signalling capability provided by this module does not |
765 | actually send signals via the OS. It I<emulates> signals at the Perl-level |
766 | such that signal handlers are called in the appropriate thread. For example, |
767 | sending C<$thr-E<gt>kill('STOP')> does not actually suspend a thread (or the |
768 | whole process), but does cause a C<$SIG{'STOP'}> handler to be called in that |
769 | thread (as illustrated above). |
770 | |
771 | As such, signals that would normally not be appropriate to use in the |
772 | C<kill()> command (e.g., C<kill('KILL', $$)>) are okay to use with the |
773 | C<-E<gt>kill()> method (again, as illustrated above). |
774 | |
775 | Correspondingly, sending a signal to a thread does not disrupt the operation |
776 | the thread is currently working on: The signal will be acted upon after the |
c0003851 |
777 | current operation has completed. For instance, if the thread is I<stuck> on |
778 | an I/O call, sending it a signal will not cause the I/O call to be interrupted |
779 | such that the signal is acted up immediately. |
780 | |
69a9b4b8 |
781 | Sending a signal to a terminated thread is ignored. |
782 | |
e4f9f4fe |
783 | =head1 WARNINGS |
784 | |
785 | =over 4 |
786 | |
4dcb9e53 |
787 | =item Perl exited with active threads: |
e4f9f4fe |
788 | |
4dcb9e53 |
789 | If the program exits without all threads having either been joined or |
790 | detached, then this warning will be issued. |
791 | |
69a9b4b8 |
792 | NOTE: If the I<main> thread exits, then this warning cannot be suppressed |
793 | using C<no warnings 'threads';> as suggested below. |
e4f9f4fe |
794 | |
c0003851 |
795 | =item Thread creation failed: pthread_create returned # |
796 | |
797 | See the appropriate I<man> page for C<pthread_create> to determine the actual |
798 | cause for the failure. |
799 | |
800 | =item Thread # terminated abnormally: ... |
801 | |
802 | A thread terminated in some manner other than just returning from its entry |
955c272e |
803 | point function, or by using C<threads-E<gt>exit()>. For example, the thread |
5cbb7319 |
804 | may have terminated because of an error, or by using C<die>. |
c0003851 |
805 | |
514612b7 |
806 | =item Using minimum thread stack size of # |
807 | |
808 | Some platforms have a minimum thread stack size. Trying to set the stack size |
809 | below this value will result in the above warning, and the stack size will be |
810 | set to the minimum. |
811 | |
c0003851 |
812 | =item Thread creation failed: pthread_attr_setstacksize(I<SIZE>) returned 22 |
813 | |
814 | The specified I<SIZE> exceeds the system's maximum stack size. Use a smaller |
815 | value for the stack size. |
816 | |
e4f9f4fe |
817 | =back |
47ba8780 |
818 | |
c0003851 |
819 | If needed, thread warnings can be suppressed by using: |
820 | |
821 | no warnings 'threads'; |
822 | |
823 | in the appropriate scope. |
824 | |
0f1612a7 |
825 | =head1 ERRORS |
826 | |
827 | =over 4 |
828 | |
fcea4b7c |
829 | =item This Perl not built to support threads |
678a9b6c |
830 | |
0f1612a7 |
831 | The particular copy of Perl that you're trying to use was not built using the |
832 | C<useithreads> configuration option. |
678a9b6c |
833 | |
0f1612a7 |
834 | Having threads support requires all of Perl and all of the XS modules in the |
835 | Perl installation to be rebuilt; it is not just a question of adding the |
836 | L<threads> module (i.e., threaded and non-threaded Perls are binary |
837 | incompatible.) |
838 | |
514612b7 |
839 | =item Cannot change stack size of an existing thread |
840 | |
841 | The stack size of currently extant threads cannot be changed, therefore, the |
842 | following results in the above error: |
843 | |
844 | $thr->set_stack_size($size); |
845 | |
4dcb9e53 |
846 | =item Cannot signal threads without safe signals |
514612b7 |
847 | |
1152d448 |
848 | Safe signals must be in effect to use the C<-E<gt>kill()> signalling method. |
9d9ff5b1 |
849 | See L</"Unsafe signals"> for more details. |
c0003851 |
850 | |
851 | =item Unrecognized signal name: ... |
852 | |
853 | The particular copy of Perl that you're trying to use does not support the |
854 | specified signal being used in a C<-E<gt>kill()> call. |
514612b7 |
855 | |
0f1612a7 |
856 | =back |
47ba8780 |
857 | |
b9c1db01 |
858 | =head1 BUGS AND LIMITATIONS |
859 | |
860 | Before you consider posting a bug report, please consult, and possibly post a |
861 | message to the discussion forum to see if what you've encountered is a known |
862 | problem. |
5c6ff896 |
863 | |
864 | =over |
865 | |
866 | =item Using non-threadsafe modules |
867 | |
5cbb7319 |
868 | Unfortunately, you may encounter Perl modules that are not I<threadsafe>. For |
5c6ff896 |
869 | example, they may crash the Perl interpreter during execution, or may dump |
870 | core on termination. Depending on the module and the requirements of your |
871 | application, it may be possible to work around such difficulties. |
872 | |
873 | If the module will only be used inside a thread, you can try loading the |
874 | module from inside the thread entry point function using C<require> (and |
875 | C<import> if needed): |
876 | |
877 | sub thr_func |
878 | { |
879 | require Unsafe::Module |
880 | # import Unsafe::Module ...; |
881 | |
882 | .... |
883 | } |
884 | |
955c272e |
885 | If the module is needed inside the I<main> thread, try modifying your |
886 | application so that the module is loaded (again using C<require> and |
887 | C<import>) after any threads are started, and in such a way that no other |
888 | threads are started afterwards. |
5c6ff896 |
889 | |
890 | If the above does not work, or is not adequate for your application, then file |
891 | a bug report on L<http://rt.cpan.org/Public/> against the problematic module. |
892 | |
fcea4b7c |
893 | =item Parent-child threads |
678a9b6c |
894 | |
fcea4b7c |
895 | On some platforms, it might not be possible to destroy I<parent> threads while |
896 | there are still existing I<child> threads. |
678a9b6c |
897 | |
404aaa48 |
898 | =item Creating threads inside special blocks |
88f8c1df |
899 | |
f2e0bb91 |
900 | Creating threads inside C<BEGIN>, C<CHECK> or C<INIT> blocks should not be |
901 | relied upon. Depending on the Perl version and the application code, results |
58a3a76c |
902 | may range from success, to (apparently harmless) warnings of leaked scalar, or |
f2e0bb91 |
903 | all the way up to crashing of the Perl interpreter. |
88f8c1df |
904 | |
1152d448 |
905 | =item Unsafe signals |
47ba8780 |
906 | |
1152d448 |
907 | Since Perl 5.8.0, signals have been made safer in Perl by postponing their |
908 | handling until the interpreter is in a I<safe> state. See |
404aaa48 |
909 | L<perl58delta/"Safe Signals"> and L<perlipc/"Deferred Signals (Safe Signals)"> |
1152d448 |
910 | for more details. |
911 | |
912 | Safe signals is the default behavior, and the old, immediate, unsafe |
913 | signalling behavior is only in effect in the following situations: |
914 | |
915 | =over 4 |
916 | |
5cbb7319 |
917 | =item * Perl has been built with C<PERL_OLD_SIGNALS> (see C<perl -V>). |
1152d448 |
918 | |
919 | =item * The environment variable C<PERL_SIGNALS> is set to C<unsafe> (see L<perlrun/"PERL_SIGNALS">). |
920 | |
921 | =item * The module L<Perl::Unsafe::Signals> is used. |
922 | |
923 | =back |
924 | |
925 | If unsafe signals is in effect, then signal handling is not thread-safe, and |
926 | the C<-E<gt>kill()> signalling method cannot be used. |
88f8c1df |
927 | |
0f1612a7 |
928 | =item Returning closures from threads |
929 | |
f2e0bb91 |
930 | Returning closures from threads should not be relied upon. Depending of the |
931 | Perl version and the application code, results may range from success, to |
58a3a76c |
932 | (apparently harmless) warnings of leaked scalar, or all the way up to crashing |
933 | of the Perl interpreter. |
0f1612a7 |
934 | |
955c272e |
935 | =item Returning objects from threads |
936 | |
b9c1db01 |
937 | Returning objects from threads does not work. Depending on the classes |
938 | involved, you may be able to work around this by returning a serialized |
939 | version of the object (e.g., using L<Data::Dumper> or L<Storable>), and then |
940 | reconstituting it in the joining thread. |
955c272e |
941 | |
0f1612a7 |
942 | =item Perl Bugs and the CPAN Version of L<threads> |
943 | |
5cbb7319 |
944 | Support for threads extends beyond the code in this module (i.e., |
0f1612a7 |
945 | F<threads.pm> and F<threads.xs>), and into the Perl iterpreter itself. Older |
946 | versions of Perl contain bugs that may manifest themselves despite using the |
947 | latest version of L<threads> from CPAN. There is no workaround for this other |
948 | than upgrading to the lastest version of Perl. |
949 | |
47ba8780 |
950 | =back |
951 | |
0f1612a7 |
952 | =head1 REQUIREMENTS |
47ba8780 |
953 | |
0f1612a7 |
954 | Perl 5.8.0 or later |
47ba8780 |
955 | |
0f1612a7 |
956 | =head1 SEE ALSO |
47ba8780 |
957 | |
0f1612a7 |
958 | L<threads> Discussion Forum on CPAN: |
959 | L<http://www.cpanforum.com/dist/threads> |
47ba8780 |
960 | |
0f1612a7 |
961 | Annotated POD for L<threads>: |
18b9e6f5 |
962 | L<http://annocpan.org/~JDHEDDEN/threads-1.62/threads.pm> |
963 | |
964 | Source repository: |
965 | L<http://code.google.com/p/threads-shared/> |
47ba8780 |
966 | |
0f1612a7 |
967 | L<threads::shared>, L<perlthrtut> |
47ba8780 |
968 | |
0f1612a7 |
969 | L<http://www.perl.com/pub/a/2002/06/11/threads.html> and |
970 | L<http://www.perl.com/pub/a/2002/09/04/threads.html> |
47ba8780 |
971 | |
0f1612a7 |
972 | Perl threads mailing list: |
973 | L<http://lists.cpan.org/showlist.cgi?name=iThreads> |
47ba8780 |
974 | |
514612b7 |
975 | Stack size discussion: |
976 | L<http://www.perlmonks.org/?node_id=532956> |
977 | |
0f1612a7 |
978 | =head1 AUTHOR |
47ba8780 |
979 | |
0f1612a7 |
980 | Artur Bergman E<lt>sky AT crucially DOT netE<gt> |
981 | |
982 | threads is released under the same license as Perl. |
983 | |
984 | CPAN version produced by Jerry D. Hedden <jdhedden AT cpan DOT org> |
985 | |
986 | =head1 ACKNOWLEDGEMENTS |
987 | |
988 | Richard Soderberg E<lt>perl AT crystalflame DOT netE<gt> - |
989 | Helping me out tons, trying to find reasons for races and other weird bugs! |
990 | |
991 | Simon Cozens E<lt>simon AT brecon DOT co DOT ukE<gt> - |
992 | Being there to answer zillions of annoying questions |
993 | |
994 | Rocco Caputo E<lt>troc AT netrus DOT netE<gt> |
47ba8780 |
995 | |
0f1612a7 |
996 | Vipul Ved Prakash E<lt>mail AT vipul DOT netE<gt> - |
997 | Helping with debugging |
47ba8780 |
998 | |
514612b7 |
999 | Dean Arnold E<lt>darnold AT presicient DOT comE<gt> - |
1000 | Stack size API |
1001 | |
47ba8780 |
1002 | =cut |