Commit | Line | Data |
47ba8780 |
1 | package threads; |
2 | |
32419a4c |
3 | use 5.008; |
fcea4b7c |
4 | |
47ba8780 |
5 | use strict; |
6 | use warnings; |
73e09c8f |
7 | |
3ceb02cd |
8 | our $VERSION = '1.36'; |
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 | # Declare that we have been loaded |
21 | $threads::threads = 1; |
22 | |
23 | # Complain if 'threads' is loaded after 'threads::shared' |
24 | if ($threads::shared::threads_shared) { |
25 | warn <<'_MSG_'; |
26 | Warning, threads::shared has already been loaded. To |
27 | enable shared variables, 'use threads' must be called |
28 | before threads::shared or any module that uses it. |
29 | _MSG_ |
30 | } |
dab065ea |
31 | } |
32 | |
fc04eb16 |
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 $sym = shift) { |
514612b7 |
50 | if ($sym =~ /^stack/) { |
51 | threads->set_stack_size(shift); |
52 | |
53 | } elsif ($sym =~ /all/) { |
0f1612a7 |
54 | push(@EXPORT, qw(yield)); |
55 | |
56 | } else { |
57 | push(@EXPORT, $sym); |
58 | } |
59 | } |
60 | |
61 | # Export subroutine names |
62 | my $caller = caller(); |
63 | foreach my $sym (@EXPORT) { |
64 | no strict 'refs'; |
65 | *{$caller.'::'.$sym} = \&{$sym}; |
66 | } |
514612b7 |
67 | |
68 | # Set stack size via environment variable |
69 | if (exists($ENV{'PERL5_ITHREADS_STACK_SIZE'})) { |
70 | threads->set_stack_size($ENV{'PERL5_ITHREADS_STACK_SIZE'}); |
71 | } |
0f1612a7 |
72 | } |
73 | |
74 | |
75 | ### Methods, etc. ### |
47ba8780 |
76 | |
4dcb9e53 |
77 | # Our own exit function/method |
78 | sub exit |
79 | { |
80 | CORE::exit(0); |
81 | } |
82 | |
ead32952 |
83 | # 'Constant' args for threads->list() |
84 | sub threads::all { } |
85 | sub threads::running { 1 } |
86 | sub threads::joinable { 0 } |
87 | |
f4cc38af |
88 | # 'new' is an alias for 'create' |
89 | *new = \&create; |
68795e93 |
90 | |
fcea4b7c |
91 | # 'async' is a function alias for the 'threads->create()' method |
92 | sub async (&;@) |
93 | { |
94 | unshift(@_, 'threads'); |
95 | # Use "goto" trick to avoid pad problems from 5.8.1 (fixed in 5.8.2) |
96 | goto &create; |
97 | } |
98 | |
99 | # Thread object equality checking |
100 | use overload ( |
101 | '==' => \&equal, |
102 | '!=' => sub { ! equal(@_) }, |
103 | 'fallback' => 1 |
104 | ); |
105 | |
47ba8780 |
106 | 1; |
0f1612a7 |
107 | |
47ba8780 |
108 | __END__ |
109 | |
110 | =head1 NAME |
111 | |
0f1612a7 |
112 | threads - Perl interpreter-based threads |
113 | |
114 | =head1 VERSION |
115 | |
3ceb02cd |
116 | This document describes threads version 1.36 |
47ba8780 |
117 | |
118 | =head1 SYNOPSIS |
119 | |
514612b7 |
120 | use threads ('yield', 'stack_size' => 64*4096); |
47ba8780 |
121 | |
38875929 |
122 | sub start_thread { |
0f1612a7 |
123 | my @args = @_; |
9d9ff5b1 |
124 | print('Thread started: ', join(' ', @args), "\n"); |
38875929 |
125 | } |
0f1612a7 |
126 | my $thread = threads->create('start_thread', 'argument'); |
127 | $thread->join(); |
128 | |
129 | threads->create(sub { print("I am a thread\n"); })->join(); |
47ba8780 |
130 | |
38875929 |
131 | my $thread3 = async { foreach (@files) { ... } }; |
0f1612a7 |
132 | $thread3->join(); |
133 | |
9d9ff5b1 |
134 | # Invoke thread in list context (implicit) so it can return a list |
0f1612a7 |
135 | my ($thr) = threads->create(sub { return (qw/a b c/); }); |
9d9ff5b1 |
136 | # or specify list context explicitly |
137 | my $thr = threads->create({'context' => 'list'}, |
138 | sub { return (qw/a b c/); }); |
0f1612a7 |
139 | my @results = $thr->join(); |
47ba8780 |
140 | |
38875929 |
141 | $thread->detach(); |
47ba8780 |
142 | |
38875929 |
143 | $thread = threads->self(); |
0f1612a7 |
144 | $thread = threads->object($tid); |
11c51ed3 |
145 | |
0f1612a7 |
146 | $tid = threads->tid(); |
147 | $tid = threads->self->tid(); |
148 | $tid = $thread->tid(); |
47ba8780 |
149 | |
38875929 |
150 | threads->yield(); |
0f1612a7 |
151 | yield(); |
152 | |
153 | my @threads = threads->list(); |
fcea4b7c |
154 | my $thread_count = threads->list(); |
f9dff5f5 |
155 | |
ead32952 |
156 | my @running = threads->list(threads::running); |
157 | my @joinable = threads->list(threads::joinable); |
158 | |
0f1612a7 |
159 | if ($thr1 == $thr2) { |
160 | ... |
161 | } |
678a9b6c |
162 | |
514612b7 |
163 | $stack_size = threads->get_stack_size(); |
164 | $old_size = threads->set_stack_size(32*4096); |
165 | |
9d9ff5b1 |
166 | # Create a thread with a specific context and stack size |
167 | my $thr = threads->create({ 'context' => 'list', |
168 | 'stack_size' => 32*4096 }, |
169 | \&foo); |
ead32952 |
170 | |
171 | # Get thread's context |
172 | my $wantarray = $thr->wantarray(); |
173 | |
174 | # Check thread's state |
175 | if ($thr->is_running()) { |
176 | sleep(1); |
177 | } |
178 | if ($thr->is_joinable()) { |
179 | $thr->join(); |
180 | } |
9d9ff5b1 |
181 | |
c0003851 |
182 | $thr->kill('SIGUSR1'); |
183 | |
4dcb9e53 |
184 | threads->exit(); |
185 | |
47ba8780 |
186 | =head1 DESCRIPTION |
187 | |
fc04eb16 |
188 | Perl 5.6 introduced something called interpreter threads. Interpreter threads |
189 | are different from I<5005threads> (the thread model of Perl 5.005) by creating |
190 | a new Perl interpreter per thread, and not sharing any data or state between |
191 | threads by default. |
11c51ed3 |
192 | |
fc04eb16 |
193 | Prior to Perl 5.8, this has only been available to people embedding Perl, and |
194 | for emulating fork() on Windows. |
11c51ed3 |
195 | |
fc04eb16 |
196 | The I<threads> API is loosely based on the old Thread.pm API. It is very |
197 | important to note that variables are not shared between threads, all variables |
198 | are by default thread local. To use shared variables one must use |
199 | L<threads::shared>. |
11c51ed3 |
200 | |
fc04eb16 |
201 | It is also important to note that you must enable threads by doing C<use |
202 | threads> as early as possible in the script itself, and that it is not |
203 | possible to enable threading inside an C<eval "">, C<do>, C<require>, or |
204 | C<use>. In particular, if you are intending to share variables with |
205 | L<threads::shared>, you must C<use threads> before you C<use threads::shared>. |
206 | (C<threads> will emit a warning if you do it the other way around.) |
47ba8780 |
207 | |
208 | =over |
209 | |
0f1612a7 |
210 | =item $thr = threads->create(FUNCTION, ARGS) |
47ba8780 |
211 | |
0f1612a7 |
212 | This will create a new thread that will begin execution with the specified |
213 | entry point function, and give it the I<ARGS> list as parameters. It will |
214 | return the corresponding threads object, or C<undef> if thread creation failed. |
47ba8780 |
215 | |
0f1612a7 |
216 | I<FUNCTION> may either be the name of a function, an anonymous subroutine, or |
217 | a code ref. |
47ba8780 |
218 | |
0f1612a7 |
219 | my $thr = threads->create('func_name', ...); |
220 | # or |
221 | my $thr = threads->create(sub { ... }, ...); |
222 | # or |
223 | my $thr = threads->create(\&func, ...); |
93512b4d |
224 | |
0f1612a7 |
225 | The C<-E<gt>new()> method is an alias for C<-E<gt>create()>. |
226 | |
227 | =item $thr->join() |
228 | |
229 | This will wait for the corresponding thread to complete its execution. When |
230 | the thread finishes, C<-E<gt>join()> will return the return value(s) of the |
231 | entry point function. |
232 | |
9d9ff5b1 |
233 | The context (void, scalar or list) for the return value(s) for C<-E<gt>join()> |
234 | is determined at the time of thread creation. |
0f1612a7 |
235 | |
9d9ff5b1 |
236 | # Create thread in list context (implicit) |
0f1612a7 |
237 | my ($thr1) = threads->create(sub { |
238 | my @results = qw(a b c); |
239 | return (@results); |
9d9ff5b1 |
240 | }); |
241 | # or (explicit) |
242 | my $thr1 = threads->create({'context' => 'list'}, |
243 | sub { |
244 | my @results = qw(a b c); |
245 | return (@results); |
246 | }); |
0f1612a7 |
247 | # Retrieve list results from thread |
248 | my @res1 = $thr1->join(); |
249 | |
9d9ff5b1 |
250 | # Create thread in scalar context (implicit) |
0f1612a7 |
251 | my $thr2 = threads->create(sub { |
252 | my $result = 42; |
253 | return ($result); |
9d9ff5b1 |
254 | }); |
0f1612a7 |
255 | # Retrieve scalar result from thread |
256 | my $res2 = $thr2->join(); |
257 | |
9d9ff5b1 |
258 | # Create a thread in void context (explicit) |
259 | my $thr3 = threads->create({'void' => 1}, |
260 | sub { print("Hello, world\n"); }); |
261 | # Join the thread in void context (i.e., no return value) |
262 | $thr3->join(); |
263 | |
264 | See L</"THREAD CONTEXT"> for more details. |
265 | |
4dcb9e53 |
266 | If the program exits without all threads having either been joined or |
267 | detached, then a warning will be issued. |
93512b4d |
268 | |
fcea4b7c |
269 | Calling C<-E<gt>join()> or C<-E<gt>detach()> on an already joined thread will |
270 | cause an error to be thrown. |
47ba8780 |
271 | |
fcea4b7c |
272 | =item $thr->detach() |
47ba8780 |
273 | |
fcea4b7c |
274 | Makes the thread unjoinable, and causes any eventual return value to be |
4dcb9e53 |
275 | discarded. When the program exits, any detached threads that are still |
276 | running are silently terminated. |
277 | |
278 | If the program exits without all threads having either been joined or |
279 | detached, then a warning will be issued. |
fcea4b7c |
280 | |
281 | Calling C<-E<gt>join()> or C<-E<gt>detach()> on an already detached thread |
282 | will cause an error to be thrown. |
0f1612a7 |
283 | |
284 | =item threads->detach() |
285 | |
286 | Class method that allows a thread to detach itself. |
287 | |
4dcb9e53 |
288 | =item threads->exit() |
289 | |
290 | The usual method for terminating a thread is to |
291 | L<return()|perlfunc/"return EXPR"> from the entry point function with the |
292 | appropriate return value(s). |
293 | |
294 | If needed, a thread can be exited at any time by calling |
295 | C<threads-E<gt>exit()>. This will cause the thread to return C<undef> in a |
296 | scalar context, or the empty list in a list context. |
297 | |
298 | Calling C<die()> in a thread indicates an abnormal exit for the thread. Any |
299 | C<$SIG{__DIE__}> handler in the thread will be called first, and then the |
300 | thread will exit with a warning message that will contain any arguments passed |
301 | in the C<die()> call. |
302 | |
303 | Calling C<exit()> in a thread is discouraged, but is equivalent to calling |
304 | C<threads-E<gt>exit()>. |
305 | |
306 | If the desired affect is to truly terminate the application from a thread, |
307 | then use L<POSIX::_exit()|POSIX/"_exit">, if available. |
308 | |
fcea4b7c |
309 | =item threads->self() |
47ba8780 |
310 | |
fcea4b7c |
311 | Class method that allows a thread to obtain its own I<threads> object. |
47ba8780 |
312 | |
0f1612a7 |
313 | =item $thr->tid() |
314 | |
315 | Returns the ID of the thread. Thread IDs are unique integers with the main |
316 | thread in a program being 0, and incrementing by 1 for every thread created. |
47ba8780 |
317 | |
0f1612a7 |
318 | =item threads->tid() |
38875929 |
319 | |
0f1612a7 |
320 | Class method that allows a thread to obtain its own ID. |
47ba8780 |
321 | |
0f1612a7 |
322 | =item threads->object($tid) |
8c9849ff |
323 | |
0f1612a7 |
324 | This will return the I<threads> object for the I<active> thread associated |
325 | with the specified thread ID. Returns C<undef> if there is no thread |
326 | associated with the TID, if the thread is joined or detached, if no TID is |
327 | specified or if the specified TID is undef. |
8c9849ff |
328 | |
fcea4b7c |
329 | =item threads->yield() |
f9dff5f5 |
330 | |
38875929 |
331 | This is a suggestion to the OS to let this thread yield CPU time to other |
332 | threads. What actually happens is highly dependent upon the underlying |
333 | thread implementation. |
f9dff5f5 |
334 | |
fcea4b7c |
335 | You may do C<use threads qw(yield)>, and then just use C<yield()> in your |
70f2e746 |
336 | code. |
337 | |
f4cc38af |
338 | =item threads->list() |
678a9b6c |
339 | |
ead32952 |
340 | =item threads->list(threads::all) |
341 | |
342 | =item threads->list(threads::running) |
343 | |
344 | =item threads->list(threads::joinable) |
345 | |
346 | With no arguments (or using C<threads::all>) and in a list context, returns a |
347 | list of all non-joined, non-detached I<threads> objects. In a scalar context, |
348 | returns a count of the same. |
349 | |
350 | With a I<true> argument (using C<threads::running>), returns a list of all |
351 | non-detached I<threads> objects that are still running. |
352 | |
353 | With a I<false> argument (using C<threads::joinable>), returns a list of all |
354 | non-joined, non-detached I<threads> objects that have finished running (i.e., |
355 | for which C<-E<gt>join()> will not I<block>). |
678a9b6c |
356 | |
0f1612a7 |
357 | =item $thr1->equal($thr2) |
358 | |
359 | Tests if two threads objects are the same thread or not. This is overloaded |
fcea4b7c |
360 | to the more natural forms: |
0f1612a7 |
361 | |
362 | if ($thr1 == $thr2) { |
363 | print("Threads are the same\n"); |
364 | } |
fcea4b7c |
365 | # or |
366 | if ($thr1 != $thr2) { |
367 | print("Threads differ\n"); |
368 | } |
0f1612a7 |
369 | |
370 | (Thread comparison is based on thread IDs.) |
371 | |
386c44e5 |
372 | =item async BLOCK; |
373 | |
374 | C<async> creates a thread to execute the block immediately following |
fcea4b7c |
375 | it. This block is treated as an anonymous subroutine, and so must have a |
376 | semi-colon after the closing brace. Like C<threads->create()>, C<async> |
377 | returns a I<threads> object. |
386c44e5 |
378 | |
f4cc38af |
379 | =item $thr->_handle() |
380 | |
381 | This I<private> method returns the memory location of the internal thread |
fcea4b7c |
382 | structure associated with a threads object. For Win32, this is a pointer to |
383 | the C<HANDLE> value returned by C<CreateThread> (i.e., C<HANDLE *>); for other |
384 | platforms, it is a pointer to the C<pthread_t> structure used in the |
404aaa48 |
385 | C<pthread_create> call (i.e., C<pthread_t *>). |
f4cc38af |
386 | |
387 | This method is of no use for general Perl threads programming. Its intent is |
388 | to provide other (XS-based) thread modules with the capability to access, and |
389 | possibly manipulate, the underlying thread structure associated with a Perl |
390 | thread. |
391 | |
392 | =item threads->_handle() |
393 | |
394 | Class method that allows a thread to obtain its own I<handle>. |
395 | |
47ba8780 |
396 | =back |
397 | |
ead32952 |
398 | =head1 THREAD STATE |
399 | |
400 | The following boolean methods are useful in determining the I<state> of a |
401 | thread. |
402 | |
403 | =over |
404 | |
405 | =item $thr->is_running() |
406 | |
407 | Returns true if a thread is still running (i.e., if its entry point function |
408 | has not yet finished/exited). |
409 | |
410 | =item $thr->is_joinable() |
411 | |
412 | Returns true if the thread has finished running, is not detached and has not |
413 | yet been joined. In other works, the thread is ready to be joined and will |
414 | not I<block>. |
415 | |
416 | =item $thr->is_detached() |
417 | |
418 | Returns true if the thread has been detached. |
419 | |
420 | =item threads->is_detached() |
421 | |
422 | Class method that allows a thread to determine whether or not it is detached. |
423 | |
424 | =back |
425 | |
9d9ff5b1 |
426 | =head1 THREAD CONTEXT |
427 | |
428 | As with subroutines, the type of value returned from a thread's entry point |
429 | function may be determined by the thread's I<context>: list, scalar or void. |
430 | The thread's context is determined at thread creation. This is necessary so |
431 | that the context is available to the entry point function via |
206f4df7 |
432 | L<wantarray()|perlfunc/"wantarray">. The thread may then specify a value of |
9d9ff5b1 |
433 | the appropriate type to be returned from C<-E<gt>join()>. |
434 | |
435 | =head2 Explicit context |
436 | |
437 | Because thread creation and thread joining may occur in different contexts, it |
438 | may be desirable to state the context explicitly to the thread's entry point |
439 | function. This may be done by calling C<-E<gt>create()> with a parameter hash |
440 | as the first argument: |
441 | |
442 | my $thr = threads->create({'context' => 'list'}, \&foo); |
443 | ... |
444 | my @results = $thr->join(); |
445 | |
446 | In the above, the threads object is returned to the parent thread in scalar |
447 | context, and the thread's entry point function C<foo> will be called in list |
448 | context such that the parent thread can receive a list from the C<-E<gt>join()> |
449 | call. Similarly, if you need the threads object, but your thread will not be |
450 | returning a value (i.e., I<void> context), you would do the following: |
451 | |
452 | my $thr = threads->create({'context' => 'void'}, \&foo); |
453 | ... |
454 | $thr->join(); |
455 | |
456 | The context type may also be used as the I<key> in the parameter hash followed |
457 | by a I<true> value: |
458 | |
459 | threads->create({'scalar' => 1}, \&foo); |
460 | ... |
461 | my ($thr) = threads->list(); |
462 | my $result = $thr->join(); |
463 | |
464 | =head2 Implicit context |
465 | |
466 | If not explicitly stated, the thread's context is implied from the context |
467 | of the C<-E<gt>create()> call: |
468 | |
469 | # Create thread in list context |
470 | my ($thr) = threads->create(...); |
471 | |
472 | # Create thread in scalar context |
473 | my $thr = threads->create(...); |
474 | |
475 | # Create thread in void context |
476 | threads->create(...); |
477 | |
ead32952 |
478 | =head2 $thr->wantarray() |
479 | |
480 | This returns the thread's context in the same manner as |
481 | L<wantarray()|perlfunc/"wantarray">. |
482 | |
483 | =head2 threads->wantarray() |
484 | |
485 | Class method to return the current thread's context. This is the same as |
486 | running L<wantarray()|perlfunc/"wantarray"> in the current thread. |
487 | |
514612b7 |
488 | =head1 THREAD STACK SIZE |
489 | |
490 | The default per-thread stack size for different platforms varies |
491 | significantly, and is almost always far more than is needed for most |
492 | applications. On Win32, Perl's makefile explicitly sets the default stack to |
493 | 16 MB; on most other platforms, the system default is used, which again may be |
494 | much larger than is needed. |
495 | |
496 | By tuning the stack size to more accurately reflect your application's needs, |
497 | you may significantly reduce your application's memory usage, and increase the |
498 | number of simultaneously running threads. |
499 | |
500 | N.B., on Windows, Address space allocation granularity is 64 KB, therefore, |
501 | setting the stack smaller than that on Win32 Perl will not save any more |
502 | memory. |
503 | |
504 | =over |
505 | |
506 | =item threads->get_stack_size(); |
507 | |
508 | Returns the current default per-thread stack size. The default is zero, which |
509 | means the system default stack size is currently in use. |
510 | |
511 | =item $size = $thr->get_stack_size(); |
512 | |
513 | Returns the stack size for a particular thread. A return value of zero |
514 | indicates the system default stack size was used for the thread. |
515 | |
516 | =item $old_size = threads->set_stack_size($new_size); |
517 | |
518 | Sets a new default per-thread stack size, and returns the previous setting. |
519 | |
520 | Some platforms have a minimum thread stack size. Trying to set the stack size |
521 | below this value will result in a warning, and the minimum stack size will be |
522 | used. |
523 | |
524 | Some Linux platforms have a maximum stack size. Setting too large of a stack |
525 | size will cause thread creation to fail. |
526 | |
527 | If needed, C<$new_size> will be rounded up to the next multiple of the memory |
528 | page size (usually 4096 or 8192). |
529 | |
530 | Threads created after the stack size is set will then either call |
531 | C<pthread_attr_setstacksize()> I<(for pthreads platforms)>, or supply the |
532 | stack size to C<CreateThread()> I<(for Win32 Perl)>. |
533 | |
534 | (Obviously, this call does not affect any currently extant threads.) |
535 | |
536 | =item use threads ('stack_size' => VALUE); |
537 | |
538 | This sets the default per-thread stack size at the start of the application. |
539 | |
540 | =item $ENV{'PERL5_ITHREADS_STACK_SIZE'} |
541 | |
542 | The default per-thread stack size may be set at the start of the application |
543 | through the use of the environment variable C<PERL5_ITHREADS_STACK_SIZE>: |
544 | |
545 | PERL5_ITHREADS_STACK_SIZE=1048576 |
546 | export PERL5_ITHREADS_STACK_SIZE |
547 | perl -e'use threads; print(threads->get_stack_size(), "\n")' |
548 | |
549 | This value overrides any C<stack_size> parameter given to C<use threads>. Its |
550 | primary purpose is to permit setting the per-thread stack size for legacy |
551 | threaded applications. |
552 | |
553 | =item threads->create({'stack_size' => VALUE}, FUNCTION, ARGS) |
554 | |
9d9ff5b1 |
555 | The stack size an individual threads may also be specified. This may be done |
556 | by calling C<-E<gt>create()> with a parameter hash as the first argument: |
557 | |
558 | my $thr = threads->create({'stack_size' => 32*4096}, \&foo, @args); |
514612b7 |
559 | |
560 | =item $thr2 = $thr1->create(FUNCTION, ARGS) |
561 | |
562 | This creates a new thread (C<$thr2>) that inherits the stack size from an |
563 | existing thread (C<$thr1>). This is shorthand for the following: |
564 | |
565 | my $stack_size = $thr1->get_stack_size(); |
566 | my $thr2 = threads->create({'stack_size' => $stack_size}, FUNCTION, ARGS); |
567 | |
568 | =back |
569 | |
c0003851 |
570 | =head1 THREAD SIGNALLING |
571 | |
9d9ff5b1 |
572 | When safe signals is in effect (the default behavior - see L</"Unsafe signals"> |
1152d448 |
573 | for more details), then signals may be sent and acted upon by individual |
574 | threads. |
c0003851 |
575 | |
576 | =over 4 |
577 | |
578 | =item $thr->kill('SIG...'); |
579 | |
580 | Sends the specified signal to the thread. Signal names and (positive) signal |
581 | numbers are the same as those supported by |
582 | L<kill()|perlfunc/"kill SIGNAL, LIST">. For example, 'SIGTERM', 'TERM' and |
583 | (depending on the OS) 15 are all valid arguments to C<-E<gt>kill()>. |
584 | |
585 | Returns the thread object to allow for method chaining: |
586 | |
587 | $thr->kill('SIG...')->join(); |
588 | |
589 | =back |
590 | |
591 | Signal handlers need to be set up in the threads for the signals they are |
592 | expected to act upon. Here's an example for I<cancelling> a thread: |
593 | |
594 | use threads; |
595 | |
c0003851 |
596 | sub thr_func |
597 | { |
598 | # Thread 'cancellation' signal handler |
c608f8c0 |
599 | $SIG{'KILL'} = sub { threads->exit(); }; |
c0003851 |
600 | |
601 | ... |
602 | } |
603 | |
604 | # Create a thread |
605 | my $thr = threads->create('thr_func'); |
606 | |
607 | ... |
608 | |
609 | # Signal the thread to terminate, and then detach |
610 | # it so that it will get cleaned up automatically |
611 | $thr->kill('KILL')->detach(); |
612 | |
404aaa48 |
613 | Here's another simplistic example that illustrates the use of thread |
614 | signalling in conjunction with a semaphore to provide rudimentary I<suspend> |
615 | and I<resume> capabilities: |
c0003851 |
616 | |
617 | use threads; |
618 | use Thread::Semaphore; |
619 | |
620 | sub thr_func |
621 | { |
622 | my $sema = shift; |
623 | |
624 | # Thread 'suspend/resume' signal handler |
625 | $SIG{'STOP'} = sub { |
626 | $sema->down(); # Thread suspended |
627 | $sema->up(); # Thread resumes |
628 | }; |
629 | |
630 | ... |
631 | } |
632 | |
633 | # Create a semaphore and send it to a thread |
634 | my $sema = Thread::Semaphore->new(); |
635 | my $thr = threads->create('thr_func', $sema); |
636 | |
637 | # Suspend the thread |
638 | $sema->down(); |
639 | $thr->kill('STOP'); |
640 | |
641 | ... |
642 | |
643 | # Allow the thread to continue |
644 | $sema->up(); |
645 | |
404aaa48 |
646 | CAVEAT: The thread signalling capability provided by this module does not |
647 | actually send signals via the OS. It I<emulates> signals at the Perl-level |
648 | such that signal handlers are called in the appropriate thread. For example, |
649 | sending C<$thr-E<gt>kill('STOP')> does not actually suspend a thread (or the |
650 | whole process), but does cause a C<$SIG{'STOP'}> handler to be called in that |
651 | thread (as illustrated above). |
652 | |
653 | As such, signals that would normally not be appropriate to use in the |
654 | C<kill()> command (e.g., C<kill('KILL', $$)>) are okay to use with the |
655 | C<-E<gt>kill()> method (again, as illustrated above). |
656 | |
657 | Correspondingly, sending a signal to a thread does not disrupt the operation |
658 | the thread is currently working on: The signal will be acted upon after the |
c0003851 |
659 | current operation has completed. For instance, if the thread is I<stuck> on |
660 | an I/O call, sending it a signal will not cause the I/O call to be interrupted |
661 | such that the signal is acted up immediately. |
662 | |
e4f9f4fe |
663 | =head1 WARNINGS |
664 | |
665 | =over 4 |
666 | |
4dcb9e53 |
667 | =item Perl exited with active threads: |
e4f9f4fe |
668 | |
4dcb9e53 |
669 | If the program exits without all threads having either been joined or |
670 | detached, then this warning will be issued. |
671 | |
672 | NOTE: This warning cannot be suppressed using C<no warnings 'threads';> as |
673 | suggested below. |
e4f9f4fe |
674 | |
c0003851 |
675 | =item Thread creation failed: pthread_create returned # |
676 | |
677 | See the appropriate I<man> page for C<pthread_create> to determine the actual |
678 | cause for the failure. |
679 | |
680 | =item Thread # terminated abnormally: ... |
681 | |
682 | A thread terminated in some manner other than just returning from its entry |
4dcb9e53 |
683 | point function. For example, the thread may have terminated using C<die>. |
c0003851 |
684 | |
514612b7 |
685 | =item Using minimum thread stack size of # |
686 | |
687 | Some platforms have a minimum thread stack size. Trying to set the stack size |
688 | below this value will result in the above warning, and the stack size will be |
689 | set to the minimum. |
690 | |
c0003851 |
691 | =item Thread creation failed: pthread_attr_setstacksize(I<SIZE>) returned 22 |
692 | |
693 | The specified I<SIZE> exceeds the system's maximum stack size. Use a smaller |
694 | value for the stack size. |
695 | |
e4f9f4fe |
696 | =back |
47ba8780 |
697 | |
c0003851 |
698 | If needed, thread warnings can be suppressed by using: |
699 | |
700 | no warnings 'threads'; |
701 | |
702 | in the appropriate scope. |
703 | |
0f1612a7 |
704 | =head1 ERRORS |
705 | |
706 | =over 4 |
707 | |
fcea4b7c |
708 | =item This Perl not built to support threads |
678a9b6c |
709 | |
0f1612a7 |
710 | The particular copy of Perl that you're trying to use was not built using the |
711 | C<useithreads> configuration option. |
678a9b6c |
712 | |
0f1612a7 |
713 | Having threads support requires all of Perl and all of the XS modules in the |
714 | Perl installation to be rebuilt; it is not just a question of adding the |
715 | L<threads> module (i.e., threaded and non-threaded Perls are binary |
716 | incompatible.) |
717 | |
514612b7 |
718 | =item Cannot change stack size of an existing thread |
719 | |
720 | The stack size of currently extant threads cannot be changed, therefore, the |
721 | following results in the above error: |
722 | |
723 | $thr->set_stack_size($size); |
724 | |
4dcb9e53 |
725 | =item Cannot signal threads without safe signals |
514612b7 |
726 | |
1152d448 |
727 | Safe signals must be in effect to use the C<-E<gt>kill()> signalling method. |
9d9ff5b1 |
728 | See L</"Unsafe signals"> for more details. |
c0003851 |
729 | |
730 | =item Unrecognized signal name: ... |
731 | |
732 | The particular copy of Perl that you're trying to use does not support the |
733 | specified signal being used in a C<-E<gt>kill()> call. |
514612b7 |
734 | |
0f1612a7 |
735 | =back |
47ba8780 |
736 | |
ab80e3f2 |
737 | =head1 BUGS |
738 | |
47ba8780 |
739 | =over |
740 | |
fcea4b7c |
741 | =item Parent-child threads |
678a9b6c |
742 | |
fcea4b7c |
743 | On some platforms, it might not be possible to destroy I<parent> threads while |
744 | there are still existing I<child> threads. |
678a9b6c |
745 | |
404aaa48 |
746 | =item Creating threads inside special blocks |
88f8c1df |
747 | |
f2e0bb91 |
748 | Creating threads inside C<BEGIN>, C<CHECK> or C<INIT> blocks should not be |
749 | relied upon. Depending on the Perl version and the application code, results |
58a3a76c |
750 | may range from success, to (apparently harmless) warnings of leaked scalar, or |
f2e0bb91 |
751 | all the way up to crashing of the Perl interpreter. |
88f8c1df |
752 | |
1152d448 |
753 | =item Unsafe signals |
47ba8780 |
754 | |
1152d448 |
755 | Since Perl 5.8.0, signals have been made safer in Perl by postponing their |
756 | handling until the interpreter is in a I<safe> state. See |
404aaa48 |
757 | L<perl58delta/"Safe Signals"> and L<perlipc/"Deferred Signals (Safe Signals)"> |
1152d448 |
758 | for more details. |
759 | |
760 | Safe signals is the default behavior, and the old, immediate, unsafe |
761 | signalling behavior is only in effect in the following situations: |
762 | |
763 | =over 4 |
764 | |
765 | =item * Perl was been built with C<PERL_OLD_SIGNALS> (see C<perl -V>). |
766 | |
767 | =item * The environment variable C<PERL_SIGNALS> is set to C<unsafe> (see L<perlrun/"PERL_SIGNALS">). |
768 | |
769 | =item * The module L<Perl::Unsafe::Signals> is used. |
770 | |
771 | =back |
772 | |
773 | If unsafe signals is in effect, then signal handling is not thread-safe, and |
774 | the C<-E<gt>kill()> signalling method cannot be used. |
88f8c1df |
775 | |
0f1612a7 |
776 | =item Returning closures from threads |
777 | |
f2e0bb91 |
778 | Returning closures from threads should not be relied upon. Depending of the |
779 | Perl version and the application code, results may range from success, to |
58a3a76c |
780 | (apparently harmless) warnings of leaked scalar, or all the way up to crashing |
781 | of the Perl interpreter. |
0f1612a7 |
782 | |
783 | =item Perl Bugs and the CPAN Version of L<threads> |
784 | |
785 | Support for threads extents beyond the code in this module (i.e., |
786 | F<threads.pm> and F<threads.xs>), and into the Perl iterpreter itself. Older |
787 | versions of Perl contain bugs that may manifest themselves despite using the |
788 | latest version of L<threads> from CPAN. There is no workaround for this other |
789 | than upgrading to the lastest version of Perl. |
790 | |
791 | (Before you consider posting a bug report, please consult, and possibly post a |
792 | message to the discussion forum to see if what you've encountered is a known |
793 | problem.) |
794 | |
47ba8780 |
795 | =back |
796 | |
0f1612a7 |
797 | =head1 REQUIREMENTS |
47ba8780 |
798 | |
0f1612a7 |
799 | Perl 5.8.0 or later |
47ba8780 |
800 | |
0f1612a7 |
801 | =head1 SEE ALSO |
47ba8780 |
802 | |
0f1612a7 |
803 | L<threads> Discussion Forum on CPAN: |
804 | L<http://www.cpanforum.com/dist/threads> |
47ba8780 |
805 | |
0f1612a7 |
806 | Annotated POD for L<threads>: |
3ceb02cd |
807 | L<http://annocpan.org/~JDHEDDEN/threads-1.36/threads.pm> |
47ba8780 |
808 | |
0f1612a7 |
809 | L<threads::shared>, L<perlthrtut> |
47ba8780 |
810 | |
0f1612a7 |
811 | L<http://www.perl.com/pub/a/2002/06/11/threads.html> and |
812 | L<http://www.perl.com/pub/a/2002/09/04/threads.html> |
47ba8780 |
813 | |
0f1612a7 |
814 | Perl threads mailing list: |
815 | L<http://lists.cpan.org/showlist.cgi?name=iThreads> |
47ba8780 |
816 | |
514612b7 |
817 | Stack size discussion: |
818 | L<http://www.perlmonks.org/?node_id=532956> |
819 | |
0f1612a7 |
820 | =head1 AUTHOR |
47ba8780 |
821 | |
0f1612a7 |
822 | Artur Bergman E<lt>sky AT crucially DOT netE<gt> |
823 | |
824 | threads is released under the same license as Perl. |
825 | |
826 | CPAN version produced by Jerry D. Hedden <jdhedden AT cpan DOT org> |
827 | |
828 | =head1 ACKNOWLEDGEMENTS |
829 | |
830 | Richard Soderberg E<lt>perl AT crystalflame DOT netE<gt> - |
831 | Helping me out tons, trying to find reasons for races and other weird bugs! |
832 | |
833 | Simon Cozens E<lt>simon AT brecon DOT co DOT ukE<gt> - |
834 | Being there to answer zillions of annoying questions |
835 | |
836 | Rocco Caputo E<lt>troc AT netrus DOT netE<gt> |
47ba8780 |
837 | |
0f1612a7 |
838 | Vipul Ved Prakash E<lt>mail AT vipul DOT netE<gt> - |
839 | Helping with debugging |
47ba8780 |
840 | |
514612b7 |
841 | Dean Arnold E<lt>darnold AT presicient DOT comE<gt> - |
842 | Stack size API |
843 | |
47ba8780 |
844 | =cut |