Commit | Line | Data |
47ba8780 |
1 | package threads; |
2 | |
32419a4c |
3 | use 5.008; |
fcea4b7c |
4 | |
47ba8780 |
5 | use strict; |
6 | use warnings; |
73e09c8f |
7 | |
8718f9a1 |
8 | our $VERSION = '1.57'; |
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 $sym = shift) { |
69a9b4b8 |
50 | if ($sym =~ /^stack/i) { |
514612b7 |
51 | threads->set_stack_size(shift); |
52 | |
69a9b4b8 |
53 | } elsif ($sym =~ /^exit/i) { |
54 | my $flag = shift; |
55 | $threads::thread_exit_only = $flag =~ /^thread/i; |
56 | |
3ab14376 |
57 | } elsif ($sym =~ /^str/i) { |
58 | import overload ('""' => \&tid); |
59 | |
de42e62a |
60 | } elsif ($sym =~ /(?:all|yield)/) { |
0f1612a7 |
61 | push(@EXPORT, qw(yield)); |
62 | |
63 | } else { |
de42e62a |
64 | require Carp; |
65 | Carp::croak("threads: Unknown import option: $sym"); |
0f1612a7 |
66 | } |
67 | } |
68 | |
69 | # Export subroutine names |
70 | my $caller = caller(); |
71 | foreach my $sym (@EXPORT) { |
72 | no strict 'refs'; |
73 | *{$caller.'::'.$sym} = \&{$sym}; |
74 | } |
514612b7 |
75 | |
76 | # Set stack size via environment variable |
77 | if (exists($ENV{'PERL5_ITHREADS_STACK_SIZE'})) { |
78 | threads->set_stack_size($ENV{'PERL5_ITHREADS_STACK_SIZE'}); |
79 | } |
0f1612a7 |
80 | } |
81 | |
82 | |
83 | ### Methods, etc. ### |
47ba8780 |
84 | |
69a9b4b8 |
85 | # Exit from a thread (only) |
4dcb9e53 |
86 | sub exit |
87 | { |
69a9b4b8 |
88 | my ($class, $status) = @_; |
89 | if (! defined($status)) { |
90 | $status = 0; |
91 | } |
92 | |
93 | # Class method only |
94 | if (ref($class)) { |
95 | require Carp; |
96 | Carp::croak("Usage: threads->exit(status)"); |
97 | } |
98 | |
99 | $class->set_thread_exit_only(1); |
100 | CORE::exit($status); |
4dcb9e53 |
101 | } |
102 | |
ead32952 |
103 | # 'Constant' args for threads->list() |
104 | sub threads::all { } |
105 | sub threads::running { 1 } |
106 | sub threads::joinable { 0 } |
107 | |
f4cc38af |
108 | # 'new' is an alias for 'create' |
109 | *new = \&create; |
68795e93 |
110 | |
fcea4b7c |
111 | # 'async' is a function alias for the 'threads->create()' method |
112 | sub async (&;@) |
113 | { |
114 | unshift(@_, 'threads'); |
115 | # Use "goto" trick to avoid pad problems from 5.8.1 (fixed in 5.8.2) |
116 | goto &create; |
117 | } |
118 | |
119 | # Thread object equality checking |
120 | use overload ( |
121 | '==' => \&equal, |
122 | '!=' => sub { ! equal(@_) }, |
123 | 'fallback' => 1 |
124 | ); |
125 | |
47ba8780 |
126 | 1; |
0f1612a7 |
127 | |
47ba8780 |
128 | __END__ |
129 | |
130 | =head1 NAME |
131 | |
0f1612a7 |
132 | threads - Perl interpreter-based threads |
133 | |
134 | =head1 VERSION |
135 | |
8718f9a1 |
136 | This document describes threads version 1.57 |
47ba8780 |
137 | |
138 | =head1 SYNOPSIS |
139 | |
3ab14376 |
140 | use threads ('yield', |
141 | 'stack_size' => 64*4096, |
142 | 'exit' => 'threads_only', |
143 | 'stringify'); |
47ba8780 |
144 | |
38875929 |
145 | sub start_thread { |
0f1612a7 |
146 | my @args = @_; |
9d9ff5b1 |
147 | print('Thread started: ', join(' ', @args), "\n"); |
38875929 |
148 | } |
fea7688c |
149 | my $thr = threads->create('start_thread', 'argument'); |
150 | $thr->join(); |
0f1612a7 |
151 | |
152 | threads->create(sub { print("I am a thread\n"); })->join(); |
47ba8780 |
153 | |
fea7688c |
154 | my $thr2 = async { foreach (@files) { ... } }; |
155 | $thr2->join(); |
955c272e |
156 | if (my $err = $thr2->error()) { |
157 | warn("Thread error: $err\n"); |
158 | } |
0f1612a7 |
159 | |
9d9ff5b1 |
160 | # Invoke thread in list context (implicit) so it can return a list |
0f1612a7 |
161 | my ($thr) = threads->create(sub { return (qw/a b c/); }); |
9d9ff5b1 |
162 | # or specify list context explicitly |
163 | my $thr = threads->create({'context' => 'list'}, |
164 | sub { return (qw/a b c/); }); |
0f1612a7 |
165 | my @results = $thr->join(); |
47ba8780 |
166 | |
fea7688c |
167 | $thr->detach(); |
47ba8780 |
168 | |
69a9b4b8 |
169 | # Get a thread's object |
fea7688c |
170 | $thr = threads->self(); |
171 | $thr = threads->object($tid); |
11c51ed3 |
172 | |
69a9b4b8 |
173 | # Get a thread's ID |
0f1612a7 |
174 | $tid = threads->tid(); |
fea7688c |
175 | $tid = $thr->tid(); |
3ab14376 |
176 | $tid = "$thr"; |
47ba8780 |
177 | |
69a9b4b8 |
178 | # Give other threads a chance to run |
38875929 |
179 | threads->yield(); |
0f1612a7 |
180 | yield(); |
181 | |
69a9b4b8 |
182 | # Lists of non-detached threads |
0f1612a7 |
183 | my @threads = threads->list(); |
fcea4b7c |
184 | my $thread_count = threads->list(); |
f9dff5f5 |
185 | |
ead32952 |
186 | my @running = threads->list(threads::running); |
187 | my @joinable = threads->list(threads::joinable); |
188 | |
69a9b4b8 |
189 | # Test thread objects |
0f1612a7 |
190 | if ($thr1 == $thr2) { |
191 | ... |
192 | } |
678a9b6c |
193 | |
69a9b4b8 |
194 | # Manage thread stack size |
514612b7 |
195 | $stack_size = threads->get_stack_size(); |
196 | $old_size = threads->set_stack_size(32*4096); |
197 | |
9d9ff5b1 |
198 | # Create a thread with a specific context and stack size |
199 | my $thr = threads->create({ 'context' => 'list', |
69a9b4b8 |
200 | 'stack_size' => 32*4096, |
201 | 'exit' => 'thread_only' }, |
9d9ff5b1 |
202 | \&foo); |
ead32952 |
203 | |
204 | # Get thread's context |
205 | my $wantarray = $thr->wantarray(); |
206 | |
207 | # Check thread's state |
208 | if ($thr->is_running()) { |
209 | sleep(1); |
210 | } |
211 | if ($thr->is_joinable()) { |
212 | $thr->join(); |
213 | } |
9d9ff5b1 |
214 | |
69a9b4b8 |
215 | # Send a signal to a thread |
c0003851 |
216 | $thr->kill('SIGUSR1'); |
217 | |
69a9b4b8 |
218 | # Exit a thread |
4dcb9e53 |
219 | threads->exit(); |
220 | |
47ba8780 |
221 | =head1 DESCRIPTION |
222 | |
fc04eb16 |
223 | Perl 5.6 introduced something called interpreter threads. Interpreter threads |
224 | are different from I<5005threads> (the thread model of Perl 5.005) by creating |
225 | a new Perl interpreter per thread, and not sharing any data or state between |
226 | threads by default. |
11c51ed3 |
227 | |
fc04eb16 |
228 | Prior to Perl 5.8, this has only been available to people embedding Perl, and |
229 | for emulating fork() on Windows. |
11c51ed3 |
230 | |
fc04eb16 |
231 | The I<threads> API is loosely based on the old Thread.pm API. It is very |
232 | important to note that variables are not shared between threads, all variables |
233 | are by default thread local. To use shared variables one must use |
234 | L<threads::shared>. |
11c51ed3 |
235 | |
fc04eb16 |
236 | It is also important to note that you must enable threads by doing C<use |
237 | threads> as early as possible in the script itself, and that it is not |
238 | possible to enable threading inside an C<eval "">, C<do>, C<require>, or |
239 | C<use>. In particular, if you are intending to share variables with |
240 | L<threads::shared>, you must C<use threads> before you C<use threads::shared>. |
241 | (C<threads> will emit a warning if you do it the other way around.) |
47ba8780 |
242 | |
243 | =over |
244 | |
0f1612a7 |
245 | =item $thr = threads->create(FUNCTION, ARGS) |
47ba8780 |
246 | |
0f1612a7 |
247 | This will create a new thread that will begin execution with the specified |
248 | entry point function, and give it the I<ARGS> list as parameters. It will |
249 | return the corresponding threads object, or C<undef> if thread creation failed. |
47ba8780 |
250 | |
0f1612a7 |
251 | I<FUNCTION> may either be the name of a function, an anonymous subroutine, or |
252 | a code ref. |
47ba8780 |
253 | |
0f1612a7 |
254 | my $thr = threads->create('func_name', ...); |
255 | # or |
256 | my $thr = threads->create(sub { ... }, ...); |
257 | # or |
258 | my $thr = threads->create(\&func, ...); |
93512b4d |
259 | |
0f1612a7 |
260 | The C<-E<gt>new()> method is an alias for C<-E<gt>create()>. |
261 | |
262 | =item $thr->join() |
263 | |
264 | This will wait for the corresponding thread to complete its execution. When |
265 | the thread finishes, C<-E<gt>join()> will return the return value(s) of the |
266 | entry point function. |
267 | |
9d9ff5b1 |
268 | The context (void, scalar or list) for the return value(s) for C<-E<gt>join()> |
269 | is determined at the time of thread creation. |
0f1612a7 |
270 | |
9d9ff5b1 |
271 | # Create thread in list context (implicit) |
0f1612a7 |
272 | my ($thr1) = threads->create(sub { |
273 | my @results = qw(a b c); |
274 | return (@results); |
9d9ff5b1 |
275 | }); |
276 | # or (explicit) |
277 | my $thr1 = threads->create({'context' => 'list'}, |
278 | sub { |
279 | my @results = qw(a b c); |
280 | return (@results); |
281 | }); |
0f1612a7 |
282 | # Retrieve list results from thread |
283 | my @res1 = $thr1->join(); |
284 | |
9d9ff5b1 |
285 | # Create thread in scalar context (implicit) |
0f1612a7 |
286 | my $thr2 = threads->create(sub { |
287 | my $result = 42; |
288 | return ($result); |
9d9ff5b1 |
289 | }); |
0f1612a7 |
290 | # Retrieve scalar result from thread |
291 | my $res2 = $thr2->join(); |
292 | |
9d9ff5b1 |
293 | # Create a thread in void context (explicit) |
294 | my $thr3 = threads->create({'void' => 1}, |
295 | sub { print("Hello, world\n"); }); |
296 | # Join the thread in void context (i.e., no return value) |
297 | $thr3->join(); |
298 | |
299 | See L</"THREAD CONTEXT"> for more details. |
300 | |
4dcb9e53 |
301 | If the program exits without all threads having either been joined or |
302 | detached, then a warning will be issued. |
93512b4d |
303 | |
fcea4b7c |
304 | Calling C<-E<gt>join()> or C<-E<gt>detach()> on an already joined thread will |
305 | cause an error to be thrown. |
47ba8780 |
306 | |
fcea4b7c |
307 | =item $thr->detach() |
47ba8780 |
308 | |
fcea4b7c |
309 | Makes the thread unjoinable, and causes any eventual return value to be |
4dcb9e53 |
310 | discarded. When the program exits, any detached threads that are still |
311 | running are silently terminated. |
312 | |
313 | If the program exits without all threads having either been joined or |
314 | detached, then a warning will be issued. |
fcea4b7c |
315 | |
316 | Calling C<-E<gt>join()> or C<-E<gt>detach()> on an already detached thread |
317 | will cause an error to be thrown. |
0f1612a7 |
318 | |
319 | =item threads->detach() |
320 | |
321 | Class method that allows a thread to detach itself. |
322 | |
fcea4b7c |
323 | =item threads->self() |
47ba8780 |
324 | |
fcea4b7c |
325 | Class method that allows a thread to obtain its own I<threads> object. |
47ba8780 |
326 | |
0f1612a7 |
327 | =item $thr->tid() |
328 | |
329 | Returns the ID of the thread. Thread IDs are unique integers with the main |
330 | thread in a program being 0, and incrementing by 1 for every thread created. |
47ba8780 |
331 | |
0f1612a7 |
332 | =item threads->tid() |
38875929 |
333 | |
0f1612a7 |
334 | Class method that allows a thread to obtain its own ID. |
47ba8780 |
335 | |
3ab14376 |
336 | =item "$thr" |
337 | |
338 | If you add the C<stringify> import option to your C<use threads> declaration, |
339 | then using a threads object in a string or a string context (e.g., as a hash |
340 | key) will cause its ID to be used as the value: |
341 | |
5c6ff896 |
342 | use threads qw(stringify); |
3ab14376 |
343 | |
5c6ff896 |
344 | my $thr = threads->create(...); |
345 | print("Thread $thr started...\n"); # Prints out: Thread 1 started... |
3ab14376 |
346 | |
0f1612a7 |
347 | =item threads->object($tid) |
8c9849ff |
348 | |
0f1612a7 |
349 | This will return the I<threads> object for the I<active> thread associated |
350 | with the specified thread ID. Returns C<undef> if there is no thread |
351 | associated with the TID, if the thread is joined or detached, if no TID is |
352 | specified or if the specified TID is undef. |
8c9849ff |
353 | |
fcea4b7c |
354 | =item threads->yield() |
f9dff5f5 |
355 | |
38875929 |
356 | This is a suggestion to the OS to let this thread yield CPU time to other |
357 | threads. What actually happens is highly dependent upon the underlying |
358 | thread implementation. |
f9dff5f5 |
359 | |
fcea4b7c |
360 | You may do C<use threads qw(yield)>, and then just use C<yield()> in your |
70f2e746 |
361 | code. |
362 | |
f4cc38af |
363 | =item threads->list() |
678a9b6c |
364 | |
ead32952 |
365 | =item threads->list(threads::all) |
366 | |
367 | =item threads->list(threads::running) |
368 | |
369 | =item threads->list(threads::joinable) |
370 | |
371 | With no arguments (or using C<threads::all>) and in a list context, returns a |
372 | list of all non-joined, non-detached I<threads> objects. In a scalar context, |
373 | returns a count of the same. |
374 | |
375 | With a I<true> argument (using C<threads::running>), returns a list of all |
8718f9a1 |
376 | non-joined, non-detached I<threads> objects that are still running. |
ead32952 |
377 | |
378 | With a I<false> argument (using C<threads::joinable>), returns a list of all |
379 | non-joined, non-detached I<threads> objects that have finished running (i.e., |
380 | for which C<-E<gt>join()> will not I<block>). |
678a9b6c |
381 | |
0f1612a7 |
382 | =item $thr1->equal($thr2) |
383 | |
384 | Tests if two threads objects are the same thread or not. This is overloaded |
fcea4b7c |
385 | to the more natural forms: |
0f1612a7 |
386 | |
387 | if ($thr1 == $thr2) { |
388 | print("Threads are the same\n"); |
389 | } |
fcea4b7c |
390 | # or |
391 | if ($thr1 != $thr2) { |
392 | print("Threads differ\n"); |
393 | } |
0f1612a7 |
394 | |
395 | (Thread comparison is based on thread IDs.) |
396 | |
386c44e5 |
397 | =item async BLOCK; |
398 | |
399 | C<async> creates a thread to execute the block immediately following |
fcea4b7c |
400 | it. This block is treated as an anonymous subroutine, and so must have a |
401 | semi-colon after the closing brace. Like C<threads->create()>, C<async> |
402 | returns a I<threads> object. |
386c44e5 |
403 | |
955c272e |
404 | =item $thr->error() |
405 | |
406 | Threads are executed in an C<eval> context. This method will return C<undef> |
407 | if the thread terminates I<normally>. Otherwise, it returns the value of |
408 | C<$@> associated with the thread's execution status in its C<eval> context. |
409 | |
f4cc38af |
410 | =item $thr->_handle() |
411 | |
412 | This I<private> method returns the memory location of the internal thread |
fcea4b7c |
413 | structure associated with a threads object. For Win32, this is a pointer to |
414 | the C<HANDLE> value returned by C<CreateThread> (i.e., C<HANDLE *>); for other |
415 | platforms, it is a pointer to the C<pthread_t> structure used in the |
404aaa48 |
416 | C<pthread_create> call (i.e., C<pthread_t *>). |
f4cc38af |
417 | |
418 | This method is of no use for general Perl threads programming. Its intent is |
419 | to provide other (XS-based) thread modules with the capability to access, and |
420 | possibly manipulate, the underlying thread structure associated with a Perl |
421 | thread. |
422 | |
423 | =item threads->_handle() |
424 | |
425 | Class method that allows a thread to obtain its own I<handle>. |
426 | |
47ba8780 |
427 | =back |
428 | |
69a9b4b8 |
429 | =head1 EXITING A THREAD |
430 | |
431 | The usual method for terminating a thread is to |
432 | L<return()|perlfunc/"return EXPR"> from the entry point function with the |
433 | appropriate return value(s). |
434 | |
435 | =over |
436 | |
437 | =item threads->exit() |
438 | |
439 | If needed, a thread can be exited at any time by calling |
440 | C<threads-E<gt>exit()>. This will cause the thread to return C<undef> in a |
441 | scalar context, or the empty list in a list context. |
442 | |
443 | When called from the I<main> thread, this behaves the same as C<exit(0)>. |
444 | |
445 | =item threads->exit(status) |
446 | |
447 | When called from a thread, this behaves like C<threads-E<gt>exit()> (i.e., the |
448 | exit status code is ignored). |
449 | |
450 | When called from the I<main> thread, this behaves the same as C<exit(status)>. |
451 | |
452 | =item die() |
453 | |
454 | Calling C<die()> in a thread indicates an abnormal exit for the thread. Any |
455 | C<$SIG{__DIE__}> handler in the thread will be called first, and then the |
456 | thread will exit with a warning message that will contain any arguments passed |
457 | in the C<die()> call. |
458 | |
459 | =item exit(status) |
460 | |
461 | Calling L<exit()|perlfunc/"exit EXPR"> inside a thread causes the whole |
462 | application to terminate. Because of this, the use of C<exit()> inside |
463 | threaded code, or in modules that might be used in threaded applications, is |
464 | strongly discouraged. |
465 | |
466 | If C<exit()> really is needed, then consider using the following: |
467 | |
60bd5ef6 |
468 | threads->exit() if threads->can('exit'); # Thread friendly |
69a9b4b8 |
469 | exit(status); |
470 | |
471 | =item use threads 'exit' => 'thread_only' |
472 | |
473 | This globally overrides the default behavior of calling C<exit()> inside a |
474 | thread, and effectively causes such calls to behave the same as |
475 | C<threads-E<gt>exit()>. In other words, with this setting, calling C<exit()> |
476 | causes only the thread to terminate. |
477 | |
478 | Because of its global effect, this setting should not be used inside modules |
479 | or the like. |
480 | |
481 | The I<main> thread is unaffected by this setting. |
482 | |
483 | =item threads->create({'exit' => 'thread_only'}, ...) |
484 | |
485 | This overrides the default behavior of C<exit()> inside the newly created |
486 | thread only. |
487 | |
488 | =item $thr->set_thread_exit_only(boolean) |
489 | |
490 | This can be used to change the I<exit thread only> behavior for a thread after |
491 | it has been created. With a I<true> argument, C<exit()> will cause the only |
492 | the thread to exit. With a I<false> argument, C<exit()> will terminate the |
493 | application. |
494 | |
495 | The I<main> thread is unaffected by this call. |
496 | |
497 | =item threads->set_thread_exit_only(boolean) |
498 | |
499 | Class method for use inside a thread to changes its own behavior for |
500 | C<exit()>. |
501 | |
502 | The I<main> thread is unaffected by this call. |
503 | |
504 | =back |
505 | |
ead32952 |
506 | =head1 THREAD STATE |
507 | |
508 | The following boolean methods are useful in determining the I<state> of a |
509 | thread. |
510 | |
511 | =over |
512 | |
513 | =item $thr->is_running() |
514 | |
515 | Returns true if a thread is still running (i.e., if its entry point function |
516 | has not yet finished/exited). |
517 | |
518 | =item $thr->is_joinable() |
519 | |
520 | Returns true if the thread has finished running, is not detached and has not |
521 | yet been joined. In other works, the thread is ready to be joined and will |
522 | not I<block>. |
523 | |
524 | =item $thr->is_detached() |
525 | |
526 | Returns true if the thread has been detached. |
527 | |
528 | =item threads->is_detached() |
529 | |
530 | Class method that allows a thread to determine whether or not it is detached. |
531 | |
532 | =back |
533 | |
9d9ff5b1 |
534 | =head1 THREAD CONTEXT |
535 | |
536 | As with subroutines, the type of value returned from a thread's entry point |
537 | function may be determined by the thread's I<context>: list, scalar or void. |
538 | The thread's context is determined at thread creation. This is necessary so |
539 | that the context is available to the entry point function via |
206f4df7 |
540 | L<wantarray()|perlfunc/"wantarray">. The thread may then specify a value of |
9d9ff5b1 |
541 | the appropriate type to be returned from C<-E<gt>join()>. |
542 | |
543 | =head2 Explicit context |
544 | |
545 | Because thread creation and thread joining may occur in different contexts, it |
546 | may be desirable to state the context explicitly to the thread's entry point |
547 | function. This may be done by calling C<-E<gt>create()> with a parameter hash |
548 | as the first argument: |
549 | |
550 | my $thr = threads->create({'context' => 'list'}, \&foo); |
551 | ... |
552 | my @results = $thr->join(); |
553 | |
554 | In the above, the threads object is returned to the parent thread in scalar |
555 | context, and the thread's entry point function C<foo> will be called in list |
556 | context such that the parent thread can receive a list from the C<-E<gt>join()> |
557 | call. Similarly, if you need the threads object, but your thread will not be |
558 | returning a value (i.e., I<void> context), you would do the following: |
559 | |
560 | my $thr = threads->create({'context' => 'void'}, \&foo); |
561 | ... |
562 | $thr->join(); |
563 | |
564 | The context type may also be used as the I<key> in the parameter hash followed |
565 | by a I<true> value: |
566 | |
567 | threads->create({'scalar' => 1}, \&foo); |
568 | ... |
569 | my ($thr) = threads->list(); |
570 | my $result = $thr->join(); |
571 | |
572 | =head2 Implicit context |
573 | |
574 | If not explicitly stated, the thread's context is implied from the context |
575 | of the C<-E<gt>create()> call: |
576 | |
577 | # Create thread in list context |
578 | my ($thr) = threads->create(...); |
579 | |
580 | # Create thread in scalar context |
581 | my $thr = threads->create(...); |
582 | |
583 | # Create thread in void context |
584 | threads->create(...); |
585 | |
ead32952 |
586 | =head2 $thr->wantarray() |
587 | |
588 | This returns the thread's context in the same manner as |
589 | L<wantarray()|perlfunc/"wantarray">. |
590 | |
591 | =head2 threads->wantarray() |
592 | |
593 | Class method to return the current thread's context. This is the same as |
594 | running L<wantarray()|perlfunc/"wantarray"> in the current thread. |
595 | |
514612b7 |
596 | =head1 THREAD STACK SIZE |
597 | |
598 | The default per-thread stack size for different platforms varies |
599 | significantly, and is almost always far more than is needed for most |
600 | applications. On Win32, Perl's makefile explicitly sets the default stack to |
601 | 16 MB; on most other platforms, the system default is used, which again may be |
602 | much larger than is needed. |
603 | |
604 | By tuning the stack size to more accurately reflect your application's needs, |
605 | you may significantly reduce your application's memory usage, and increase the |
606 | number of simultaneously running threads. |
607 | |
608 | N.B., on Windows, Address space allocation granularity is 64 KB, therefore, |
609 | setting the stack smaller than that on Win32 Perl will not save any more |
610 | memory. |
611 | |
612 | =over |
613 | |
614 | =item threads->get_stack_size(); |
615 | |
616 | Returns the current default per-thread stack size. The default is zero, which |
617 | means the system default stack size is currently in use. |
618 | |
619 | =item $size = $thr->get_stack_size(); |
620 | |
621 | Returns the stack size for a particular thread. A return value of zero |
622 | indicates the system default stack size was used for the thread. |
623 | |
624 | =item $old_size = threads->set_stack_size($new_size); |
625 | |
626 | Sets a new default per-thread stack size, and returns the previous setting. |
627 | |
628 | Some platforms have a minimum thread stack size. Trying to set the stack size |
629 | below this value will result in a warning, and the minimum stack size will be |
630 | used. |
631 | |
632 | Some Linux platforms have a maximum stack size. Setting too large of a stack |
633 | size will cause thread creation to fail. |
634 | |
635 | If needed, C<$new_size> will be rounded up to the next multiple of the memory |
636 | page size (usually 4096 or 8192). |
637 | |
638 | Threads created after the stack size is set will then either call |
639 | C<pthread_attr_setstacksize()> I<(for pthreads platforms)>, or supply the |
640 | stack size to C<CreateThread()> I<(for Win32 Perl)>. |
641 | |
642 | (Obviously, this call does not affect any currently extant threads.) |
643 | |
644 | =item use threads ('stack_size' => VALUE); |
645 | |
646 | This sets the default per-thread stack size at the start of the application. |
647 | |
648 | =item $ENV{'PERL5_ITHREADS_STACK_SIZE'} |
649 | |
650 | The default per-thread stack size may be set at the start of the application |
651 | through the use of the environment variable C<PERL5_ITHREADS_STACK_SIZE>: |
652 | |
653 | PERL5_ITHREADS_STACK_SIZE=1048576 |
654 | export PERL5_ITHREADS_STACK_SIZE |
655 | perl -e'use threads; print(threads->get_stack_size(), "\n")' |
656 | |
657 | This value overrides any C<stack_size> parameter given to C<use threads>. Its |
658 | primary purpose is to permit setting the per-thread stack size for legacy |
659 | threaded applications. |
660 | |
661 | =item threads->create({'stack_size' => VALUE}, FUNCTION, ARGS) |
662 | |
9d9ff5b1 |
663 | The stack size an individual threads may also be specified. This may be done |
664 | by calling C<-E<gt>create()> with a parameter hash as the first argument: |
665 | |
666 | my $thr = threads->create({'stack_size' => 32*4096}, \&foo, @args); |
514612b7 |
667 | |
668 | =item $thr2 = $thr1->create(FUNCTION, ARGS) |
669 | |
670 | This creates a new thread (C<$thr2>) that inherits the stack size from an |
671 | existing thread (C<$thr1>). This is shorthand for the following: |
672 | |
673 | my $stack_size = $thr1->get_stack_size(); |
674 | my $thr2 = threads->create({'stack_size' => $stack_size}, FUNCTION, ARGS); |
675 | |
676 | =back |
677 | |
c0003851 |
678 | =head1 THREAD SIGNALLING |
679 | |
9d9ff5b1 |
680 | When safe signals is in effect (the default behavior - see L</"Unsafe signals"> |
1152d448 |
681 | for more details), then signals may be sent and acted upon by individual |
682 | threads. |
c0003851 |
683 | |
684 | =over 4 |
685 | |
686 | =item $thr->kill('SIG...'); |
687 | |
688 | Sends the specified signal to the thread. Signal names and (positive) signal |
689 | numbers are the same as those supported by |
690 | L<kill()|perlfunc/"kill SIGNAL, LIST">. For example, 'SIGTERM', 'TERM' and |
691 | (depending on the OS) 15 are all valid arguments to C<-E<gt>kill()>. |
692 | |
693 | Returns the thread object to allow for method chaining: |
694 | |
695 | $thr->kill('SIG...')->join(); |
696 | |
697 | =back |
698 | |
699 | Signal handlers need to be set up in the threads for the signals they are |
700 | expected to act upon. Here's an example for I<cancelling> a thread: |
701 | |
702 | use threads; |
703 | |
c0003851 |
704 | sub thr_func |
705 | { |
706 | # Thread 'cancellation' signal handler |
c608f8c0 |
707 | $SIG{'KILL'} = sub { threads->exit(); }; |
c0003851 |
708 | |
709 | ... |
710 | } |
711 | |
712 | # Create a thread |
713 | my $thr = threads->create('thr_func'); |
714 | |
715 | ... |
716 | |
717 | # Signal the thread to terminate, and then detach |
718 | # it so that it will get cleaned up automatically |
719 | $thr->kill('KILL')->detach(); |
720 | |
404aaa48 |
721 | Here's another simplistic example that illustrates the use of thread |
722 | signalling in conjunction with a semaphore to provide rudimentary I<suspend> |
723 | and I<resume> capabilities: |
c0003851 |
724 | |
725 | use threads; |
726 | use Thread::Semaphore; |
727 | |
728 | sub thr_func |
729 | { |
730 | my $sema = shift; |
731 | |
732 | # Thread 'suspend/resume' signal handler |
733 | $SIG{'STOP'} = sub { |
734 | $sema->down(); # Thread suspended |
735 | $sema->up(); # Thread resumes |
736 | }; |
737 | |
738 | ... |
739 | } |
740 | |
741 | # Create a semaphore and send it to a thread |
742 | my $sema = Thread::Semaphore->new(); |
743 | my $thr = threads->create('thr_func', $sema); |
744 | |
745 | # Suspend the thread |
746 | $sema->down(); |
747 | $thr->kill('STOP'); |
748 | |
749 | ... |
750 | |
751 | # Allow the thread to continue |
752 | $sema->up(); |
753 | |
404aaa48 |
754 | CAVEAT: The thread signalling capability provided by this module does not |
755 | actually send signals via the OS. It I<emulates> signals at the Perl-level |
756 | such that signal handlers are called in the appropriate thread. For example, |
757 | sending C<$thr-E<gt>kill('STOP')> does not actually suspend a thread (or the |
758 | whole process), but does cause a C<$SIG{'STOP'}> handler to be called in that |
759 | thread (as illustrated above). |
760 | |
761 | As such, signals that would normally not be appropriate to use in the |
762 | C<kill()> command (e.g., C<kill('KILL', $$)>) are okay to use with the |
763 | C<-E<gt>kill()> method (again, as illustrated above). |
764 | |
765 | Correspondingly, sending a signal to a thread does not disrupt the operation |
766 | the thread is currently working on: The signal will be acted upon after the |
c0003851 |
767 | current operation has completed. For instance, if the thread is I<stuck> on |
768 | an I/O call, sending it a signal will not cause the I/O call to be interrupted |
769 | such that the signal is acted up immediately. |
770 | |
69a9b4b8 |
771 | Sending a signal to a terminated thread is ignored. |
772 | |
e4f9f4fe |
773 | =head1 WARNINGS |
774 | |
775 | =over 4 |
776 | |
4dcb9e53 |
777 | =item Perl exited with active threads: |
e4f9f4fe |
778 | |
4dcb9e53 |
779 | If the program exits without all threads having either been joined or |
780 | detached, then this warning will be issued. |
781 | |
69a9b4b8 |
782 | NOTE: If the I<main> thread exits, then this warning cannot be suppressed |
783 | using C<no warnings 'threads';> as suggested below. |
e4f9f4fe |
784 | |
c0003851 |
785 | =item Thread creation failed: pthread_create returned # |
786 | |
787 | See the appropriate I<man> page for C<pthread_create> to determine the actual |
788 | cause for the failure. |
789 | |
790 | =item Thread # terminated abnormally: ... |
791 | |
792 | A thread terminated in some manner other than just returning from its entry |
955c272e |
793 | point function, or by using C<threads-E<gt>exit()>. For example, the thread |
794 | may have terminated because of a error, or by using C<die>. |
c0003851 |
795 | |
514612b7 |
796 | =item Using minimum thread stack size of # |
797 | |
798 | Some platforms have a minimum thread stack size. Trying to set the stack size |
799 | below this value will result in the above warning, and the stack size will be |
800 | set to the minimum. |
801 | |
c0003851 |
802 | =item Thread creation failed: pthread_attr_setstacksize(I<SIZE>) returned 22 |
803 | |
804 | The specified I<SIZE> exceeds the system's maximum stack size. Use a smaller |
805 | value for the stack size. |
806 | |
e4f9f4fe |
807 | =back |
47ba8780 |
808 | |
c0003851 |
809 | If needed, thread warnings can be suppressed by using: |
810 | |
811 | no warnings 'threads'; |
812 | |
813 | in the appropriate scope. |
814 | |
0f1612a7 |
815 | =head1 ERRORS |
816 | |
817 | =over 4 |
818 | |
fcea4b7c |
819 | =item This Perl not built to support threads |
678a9b6c |
820 | |
0f1612a7 |
821 | The particular copy of Perl that you're trying to use was not built using the |
822 | C<useithreads> configuration option. |
678a9b6c |
823 | |
0f1612a7 |
824 | Having threads support requires all of Perl and all of the XS modules in the |
825 | Perl installation to be rebuilt; it is not just a question of adding the |
826 | L<threads> module (i.e., threaded and non-threaded Perls are binary |
827 | incompatible.) |
828 | |
514612b7 |
829 | =item Cannot change stack size of an existing thread |
830 | |
831 | The stack size of currently extant threads cannot be changed, therefore, the |
832 | following results in the above error: |
833 | |
834 | $thr->set_stack_size($size); |
835 | |
4dcb9e53 |
836 | =item Cannot signal threads without safe signals |
514612b7 |
837 | |
1152d448 |
838 | Safe signals must be in effect to use the C<-E<gt>kill()> signalling method. |
9d9ff5b1 |
839 | See L</"Unsafe signals"> for more details. |
c0003851 |
840 | |
841 | =item Unrecognized signal name: ... |
842 | |
843 | The particular copy of Perl that you're trying to use does not support the |
844 | specified signal being used in a C<-E<gt>kill()> call. |
514612b7 |
845 | |
0f1612a7 |
846 | =back |
47ba8780 |
847 | |
b9c1db01 |
848 | =head1 BUGS AND LIMITATIONS |
849 | |
850 | Before you consider posting a bug report, please consult, and possibly post a |
851 | message to the discussion forum to see if what you've encountered is a known |
852 | problem. |
5c6ff896 |
853 | |
854 | =over |
855 | |
856 | =item Using non-threadsafe modules |
857 | |
858 | Unfortunately, you may encounter Perl modules are not I<threadsafe>. For |
859 | example, they may crash the Perl interpreter during execution, or may dump |
860 | core on termination. Depending on the module and the requirements of your |
861 | application, it may be possible to work around such difficulties. |
862 | |
863 | If the module will only be used inside a thread, you can try loading the |
864 | module from inside the thread entry point function using C<require> (and |
865 | C<import> if needed): |
866 | |
867 | sub thr_func |
868 | { |
869 | require Unsafe::Module |
870 | # import Unsafe::Module ...; |
871 | |
872 | .... |
873 | } |
874 | |
955c272e |
875 | If the module is needed inside the I<main> thread, try modifying your |
876 | application so that the module is loaded (again using C<require> and |
877 | C<import>) after any threads are started, and in such a way that no other |
878 | threads are started afterwards. |
5c6ff896 |
879 | |
880 | If the above does not work, or is not adequate for your application, then file |
881 | a bug report on L<http://rt.cpan.org/Public/> against the problematic module. |
882 | |
fcea4b7c |
883 | =item Parent-child threads |
678a9b6c |
884 | |
fcea4b7c |
885 | On some platforms, it might not be possible to destroy I<parent> threads while |
886 | there are still existing I<child> threads. |
678a9b6c |
887 | |
404aaa48 |
888 | =item Creating threads inside special blocks |
88f8c1df |
889 | |
f2e0bb91 |
890 | Creating threads inside C<BEGIN>, C<CHECK> or C<INIT> blocks should not be |
891 | relied upon. Depending on the Perl version and the application code, results |
58a3a76c |
892 | may range from success, to (apparently harmless) warnings of leaked scalar, or |
f2e0bb91 |
893 | all the way up to crashing of the Perl interpreter. |
88f8c1df |
894 | |
1152d448 |
895 | =item Unsafe signals |
47ba8780 |
896 | |
1152d448 |
897 | Since Perl 5.8.0, signals have been made safer in Perl by postponing their |
898 | handling until the interpreter is in a I<safe> state. See |
404aaa48 |
899 | L<perl58delta/"Safe Signals"> and L<perlipc/"Deferred Signals (Safe Signals)"> |
1152d448 |
900 | for more details. |
901 | |
902 | Safe signals is the default behavior, and the old, immediate, unsafe |
903 | signalling behavior is only in effect in the following situations: |
904 | |
905 | =over 4 |
906 | |
907 | =item * Perl was been built with C<PERL_OLD_SIGNALS> (see C<perl -V>). |
908 | |
909 | =item * The environment variable C<PERL_SIGNALS> is set to C<unsafe> (see L<perlrun/"PERL_SIGNALS">). |
910 | |
911 | =item * The module L<Perl::Unsafe::Signals> is used. |
912 | |
913 | =back |
914 | |
915 | If unsafe signals is in effect, then signal handling is not thread-safe, and |
916 | the C<-E<gt>kill()> signalling method cannot be used. |
88f8c1df |
917 | |
0f1612a7 |
918 | =item Returning closures from threads |
919 | |
f2e0bb91 |
920 | Returning closures from threads should not be relied upon. Depending of the |
921 | Perl version and the application code, results may range from success, to |
58a3a76c |
922 | (apparently harmless) warnings of leaked scalar, or all the way up to crashing |
923 | of the Perl interpreter. |
0f1612a7 |
924 | |
955c272e |
925 | =item Returning objects from threads |
926 | |
b9c1db01 |
927 | Returning objects from threads does not work. Depending on the classes |
928 | involved, you may be able to work around this by returning a serialized |
929 | version of the object (e.g., using L<Data::Dumper> or L<Storable>), and then |
930 | reconstituting it in the joining thread. |
955c272e |
931 | |
0f1612a7 |
932 | =item Perl Bugs and the CPAN Version of L<threads> |
933 | |
934 | Support for threads extents beyond the code in this module (i.e., |
935 | F<threads.pm> and F<threads.xs>), and into the Perl iterpreter itself. Older |
936 | versions of Perl contain bugs that may manifest themselves despite using the |
937 | latest version of L<threads> from CPAN. There is no workaround for this other |
938 | than upgrading to the lastest version of Perl. |
939 | |
47ba8780 |
940 | =back |
941 | |
0f1612a7 |
942 | =head1 REQUIREMENTS |
47ba8780 |
943 | |
0f1612a7 |
944 | Perl 5.8.0 or later |
47ba8780 |
945 | |
0f1612a7 |
946 | =head1 SEE ALSO |
47ba8780 |
947 | |
0f1612a7 |
948 | L<threads> Discussion Forum on CPAN: |
949 | L<http://www.cpanforum.com/dist/threads> |
47ba8780 |
950 | |
0f1612a7 |
951 | Annotated POD for L<threads>: |
8718f9a1 |
952 | L<http://annocpan.org/~JDHEDDEN/threads-1.57/threads.pm> |
47ba8780 |
953 | |
0f1612a7 |
954 | L<threads::shared>, L<perlthrtut> |
47ba8780 |
955 | |
0f1612a7 |
956 | L<http://www.perl.com/pub/a/2002/06/11/threads.html> and |
957 | L<http://www.perl.com/pub/a/2002/09/04/threads.html> |
47ba8780 |
958 | |
0f1612a7 |
959 | Perl threads mailing list: |
960 | L<http://lists.cpan.org/showlist.cgi?name=iThreads> |
47ba8780 |
961 | |
514612b7 |
962 | Stack size discussion: |
963 | L<http://www.perlmonks.org/?node_id=532956> |
964 | |
0f1612a7 |
965 | =head1 AUTHOR |
47ba8780 |
966 | |
0f1612a7 |
967 | Artur Bergman E<lt>sky AT crucially DOT netE<gt> |
968 | |
969 | threads is released under the same license as Perl. |
970 | |
971 | CPAN version produced by Jerry D. Hedden <jdhedden AT cpan DOT org> |
972 | |
973 | =head1 ACKNOWLEDGEMENTS |
974 | |
975 | Richard Soderberg E<lt>perl AT crystalflame DOT netE<gt> - |
976 | Helping me out tons, trying to find reasons for races and other weird bugs! |
977 | |
978 | Simon Cozens E<lt>simon AT brecon DOT co DOT ukE<gt> - |
979 | Being there to answer zillions of annoying questions |
980 | |
981 | Rocco Caputo E<lt>troc AT netrus DOT netE<gt> |
47ba8780 |
982 | |
0f1612a7 |
983 | Vipul Ved Prakash E<lt>mail AT vipul DOT netE<gt> - |
984 | Helping with debugging |
47ba8780 |
985 | |
514612b7 |
986 | Dean Arnold E<lt>darnold AT presicient DOT comE<gt> - |
987 | Stack size API |
988 | |
47ba8780 |
989 | =cut |