Commit | Line | Data |
---|---|---|
47ba8780 AB |
1 | package threads; |
2 | ||
32419a4c | 3 | use 5.008; |
fcea4b7c | 4 | |
47ba8780 AB |
5 | use strict; |
6 | use warnings; | |
73e09c8f | 7 | |
894eec8b | 8 | our $VERSION = '1.53'; |
fcea4b7c JH |
9 | my $XS_VERSION = $VERSION; |
10 | $VERSION = eval $VERSION; | |
73e09c8f | 11 | |
73e09c8f | 12 | |
fcea4b7c JH |
13 | BEGIN { |
14 | # Verify this Perl supports threads | |
15 | use Config; | |
16 | if (! $Config{useithreads}) { | |
17 | die("This Perl not built to support threads\n"); | |
73e09c8f | 18 | } |
47ba8780 | 19 | |
fcea4b7c JH |
20 | # Complain if 'threads' is loaded after 'threads::shared' |
21 | if ($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 AB |
28 | } |
29 | ||
fc04eb16 | 30 | |
45cd5be7 SP |
31 | # Declare that we have been loaded |
32 | $threads::threads = 1; | |
33 | ||
0f1612a7 JH |
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 JH |
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 JH |
51 | threads->set_stack_size(shift); |
52 | ||
69a9b4b8 RGS |
53 | } elsif ($sym =~ /^exit/i) { |
54 | my $flag = shift; | |
55 | $threads::thread_exit_only = $flag =~ /^thread/i; | |
56 | ||
3ab14376 JH |
57 | } elsif ($sym =~ /^str/i) { |
58 | import overload ('""' => \&tid); | |
59 | ||
de42e62a | 60 | } elsif ($sym =~ /(?:all|yield)/) { |
0f1612a7 JH |
61 | push(@EXPORT, qw(yield)); |
62 | ||
63 | } else { | |
de42e62a JH |
64 | require Carp; |
65 | Carp::croak("threads: Unknown import option: $sym"); | |
0f1612a7 JH |
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 JH |
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 JH |
80 | } |
81 | ||
82 | ||
83 | ### Methods, etc. ### | |
47ba8780 | 84 | |
69a9b4b8 | 85 | # Exit from a thread (only) |
4dcb9e53 JH |
86 | sub exit |
87 | { | |
69a9b4b8 RGS |
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 JH |
101 | } |
102 | ||
ead32952 JH |
103 | # 'Constant' args for threads->list() |
104 | sub threads::all { } | |
105 | sub threads::running { 1 } | |
106 | sub threads::joinable { 0 } | |
107 | ||
f4cc38af JH |
108 | # 'new' is an alias for 'create' |
109 | *new = \&create; | |
68795e93 | 110 | |
fcea4b7c JH |
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 AB |
128 | __END__ |
129 | ||
130 | =head1 NAME | |
131 | ||
0f1612a7 JH |
132 | threads - Perl interpreter-based threads |
133 | ||
134 | =head1 VERSION | |
135 | ||
894eec8b | 136 | This document describes threads version 1.53 |
47ba8780 AB |
137 | |
138 | =head1 SYNOPSIS | |
139 | ||
3ab14376 JH |
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 JH |
149 | my $thr = threads->create('start_thread', 'argument'); |
150 | $thr->join(); | |
0f1612a7 JH |
151 | |
152 | threads->create(sub { print("I am a thread\n"); })->join(); | |
47ba8780 | 153 | |
fea7688c JH |
154 | my $thr2 = async { foreach (@files) { ... } }; |
155 | $thr2->join(); | |
0f1612a7 | 156 | |
9d9ff5b1 | 157 | # Invoke thread in list context (implicit) so it can return a list |
0f1612a7 | 158 | my ($thr) = threads->create(sub { return (qw/a b c/); }); |
9d9ff5b1 JH |
159 | # or specify list context explicitly |
160 | my $thr = threads->create({'context' => 'list'}, | |
161 | sub { return (qw/a b c/); }); | |
0f1612a7 | 162 | my @results = $thr->join(); |
47ba8780 | 163 | |
fea7688c | 164 | $thr->detach(); |
47ba8780 | 165 | |
69a9b4b8 | 166 | # Get a thread's object |
fea7688c JH |
167 | $thr = threads->self(); |
168 | $thr = threads->object($tid); | |
11c51ed3 | 169 | |
69a9b4b8 | 170 | # Get a thread's ID |
0f1612a7 | 171 | $tid = threads->tid(); |
fea7688c | 172 | $tid = $thr->tid(); |
3ab14376 | 173 | $tid = "$thr"; |
47ba8780 | 174 | |
69a9b4b8 | 175 | # Give other threads a chance to run |
38875929 | 176 | threads->yield(); |
0f1612a7 JH |
177 | yield(); |
178 | ||
69a9b4b8 | 179 | # Lists of non-detached threads |
0f1612a7 | 180 | my @threads = threads->list(); |
fcea4b7c | 181 | my $thread_count = threads->list(); |
f9dff5f5 | 182 | |
ead32952 JH |
183 | my @running = threads->list(threads::running); |
184 | my @joinable = threads->list(threads::joinable); | |
185 | ||
69a9b4b8 | 186 | # Test thread objects |
0f1612a7 JH |
187 | if ($thr1 == $thr2) { |
188 | ... | |
189 | } | |
678a9b6c | 190 | |
69a9b4b8 | 191 | # Manage thread stack size |
514612b7 JH |
192 | $stack_size = threads->get_stack_size(); |
193 | $old_size = threads->set_stack_size(32*4096); | |
194 | ||
9d9ff5b1 JH |
195 | # Create a thread with a specific context and stack size |
196 | my $thr = threads->create({ 'context' => 'list', | |
69a9b4b8 RGS |
197 | 'stack_size' => 32*4096, |
198 | 'exit' => 'thread_only' }, | |
9d9ff5b1 | 199 | \&foo); |
ead32952 JH |
200 | |
201 | # Get thread's context | |
202 | my $wantarray = $thr->wantarray(); | |
203 | ||
204 | # Check thread's state | |
205 | if ($thr->is_running()) { | |
206 | sleep(1); | |
207 | } | |
208 | if ($thr->is_joinable()) { | |
209 | $thr->join(); | |
210 | } | |
9d9ff5b1 | 211 | |
69a9b4b8 | 212 | # Send a signal to a thread |
c0003851 JH |
213 | $thr->kill('SIGUSR1'); |
214 | ||
69a9b4b8 | 215 | # Exit a thread |
4dcb9e53 JH |
216 | threads->exit(); |
217 | ||
47ba8780 AB |
218 | =head1 DESCRIPTION |
219 | ||
fc04eb16 JH |
220 | Perl 5.6 introduced something called interpreter threads. Interpreter threads |
221 | are different from I<5005threads> (the thread model of Perl 5.005) by creating | |
222 | a new Perl interpreter per thread, and not sharing any data or state between | |
223 | threads by default. | |
11c51ed3 | 224 | |
fc04eb16 JH |
225 | Prior to Perl 5.8, this has only been available to people embedding Perl, and |
226 | for emulating fork() on Windows. | |
11c51ed3 | 227 | |
fc04eb16 JH |
228 | The I<threads> API is loosely based on the old Thread.pm API. It is very |
229 | important to note that variables are not shared between threads, all variables | |
230 | are by default thread local. To use shared variables one must use | |
231 | L<threads::shared>. | |
11c51ed3 | 232 | |
fc04eb16 JH |
233 | It is also important to note that you must enable threads by doing C<use |
234 | threads> as early as possible in the script itself, and that it is not | |
235 | possible to enable threading inside an C<eval "">, C<do>, C<require>, or | |
236 | C<use>. In particular, if you are intending to share variables with | |
237 | L<threads::shared>, you must C<use threads> before you C<use threads::shared>. | |
238 | (C<threads> will emit a warning if you do it the other way around.) | |
47ba8780 AB |
239 | |
240 | =over | |
241 | ||
0f1612a7 | 242 | =item $thr = threads->create(FUNCTION, ARGS) |
47ba8780 | 243 | |
0f1612a7 JH |
244 | This will create a new thread that will begin execution with the specified |
245 | entry point function, and give it the I<ARGS> list as parameters. It will | |
246 | return the corresponding threads object, or C<undef> if thread creation failed. | |
47ba8780 | 247 | |
0f1612a7 JH |
248 | I<FUNCTION> may either be the name of a function, an anonymous subroutine, or |
249 | a code ref. | |
47ba8780 | 250 | |
0f1612a7 JH |
251 | my $thr = threads->create('func_name', ...); |
252 | # or | |
253 | my $thr = threads->create(sub { ... }, ...); | |
254 | # or | |
255 | my $thr = threads->create(\&func, ...); | |
93512b4d | 256 | |
0f1612a7 JH |
257 | The C<-E<gt>new()> method is an alias for C<-E<gt>create()>. |
258 | ||
259 | =item $thr->join() | |
260 | ||
261 | This will wait for the corresponding thread to complete its execution. When | |
262 | the thread finishes, C<-E<gt>join()> will return the return value(s) of the | |
263 | entry point function. | |
264 | ||
9d9ff5b1 JH |
265 | The context (void, scalar or list) for the return value(s) for C<-E<gt>join()> |
266 | is determined at the time of thread creation. | |
0f1612a7 | 267 | |
9d9ff5b1 | 268 | # Create thread in list context (implicit) |
0f1612a7 JH |
269 | my ($thr1) = threads->create(sub { |
270 | my @results = qw(a b c); | |
271 | return (@results); | |
9d9ff5b1 JH |
272 | }); |
273 | # or (explicit) | |
274 | my $thr1 = threads->create({'context' => 'list'}, | |
275 | sub { | |
276 | my @results = qw(a b c); | |
277 | return (@results); | |
278 | }); | |
0f1612a7 JH |
279 | # Retrieve list results from thread |
280 | my @res1 = $thr1->join(); | |
281 | ||
9d9ff5b1 | 282 | # Create thread in scalar context (implicit) |
0f1612a7 JH |
283 | my $thr2 = threads->create(sub { |
284 | my $result = 42; | |
285 | return ($result); | |
9d9ff5b1 | 286 | }); |
0f1612a7 JH |
287 | # Retrieve scalar result from thread |
288 | my $res2 = $thr2->join(); | |
289 | ||
9d9ff5b1 JH |
290 | # Create a thread in void context (explicit) |
291 | my $thr3 = threads->create({'void' => 1}, | |
292 | sub { print("Hello, world\n"); }); | |
293 | # Join the thread in void context (i.e., no return value) | |
294 | $thr3->join(); | |
295 | ||
296 | See L</"THREAD CONTEXT"> for more details. | |
297 | ||
4dcb9e53 JH |
298 | If the program exits without all threads having either been joined or |
299 | detached, then a warning will be issued. | |
93512b4d | 300 | |
fcea4b7c JH |
301 | Calling C<-E<gt>join()> or C<-E<gt>detach()> on an already joined thread will |
302 | cause an error to be thrown. | |
47ba8780 | 303 | |
fcea4b7c | 304 | =item $thr->detach() |
47ba8780 | 305 | |
fcea4b7c | 306 | Makes the thread unjoinable, and causes any eventual return value to be |
4dcb9e53 JH |
307 | discarded. When the program exits, any detached threads that are still |
308 | running are silently terminated. | |
309 | ||
310 | If the program exits without all threads having either been joined or | |
311 | detached, then a warning will be issued. | |
fcea4b7c JH |
312 | |
313 | Calling C<-E<gt>join()> or C<-E<gt>detach()> on an already detached thread | |
314 | will cause an error to be thrown. | |
0f1612a7 JH |
315 | |
316 | =item threads->detach() | |
317 | ||
318 | Class method that allows a thread to detach itself. | |
319 | ||
fcea4b7c | 320 | =item threads->self() |
47ba8780 | 321 | |
fcea4b7c | 322 | Class method that allows a thread to obtain its own I<threads> object. |
47ba8780 | 323 | |
0f1612a7 JH |
324 | =item $thr->tid() |
325 | ||
326 | Returns the ID of the thread. Thread IDs are unique integers with the main | |
327 | thread in a program being 0, and incrementing by 1 for every thread created. | |
47ba8780 | 328 | |
0f1612a7 | 329 | =item threads->tid() |
38875929 | 330 | |
0f1612a7 | 331 | Class method that allows a thread to obtain its own ID. |
47ba8780 | 332 | |
3ab14376 JH |
333 | =item "$thr" |
334 | ||
335 | If you add the C<stringify> import option to your C<use threads> declaration, | |
336 | then using a threads object in a string or a string context (e.g., as a hash | |
337 | key) will cause its ID to be used as the value: | |
338 | ||
5c6ff896 | 339 | use threads qw(stringify); |
3ab14376 | 340 | |
5c6ff896 JH |
341 | my $thr = threads->create(...); |
342 | print("Thread $thr started...\n"); # Prints out: Thread 1 started... | |
3ab14376 | 343 | |
0f1612a7 | 344 | =item threads->object($tid) |
8c9849ff | 345 | |
0f1612a7 JH |
346 | This will return the I<threads> object for the I<active> thread associated |
347 | with the specified thread ID. Returns C<undef> if there is no thread | |
348 | associated with the TID, if the thread is joined or detached, if no TID is | |
349 | specified or if the specified TID is undef. | |
8c9849ff | 350 | |
fcea4b7c | 351 | =item threads->yield() |
f9dff5f5 | 352 | |
38875929 DM |
353 | This is a suggestion to the OS to let this thread yield CPU time to other |
354 | threads. What actually happens is highly dependent upon the underlying | |
355 | thread implementation. | |
f9dff5f5 | 356 | |
fcea4b7c | 357 | You may do C<use threads qw(yield)>, and then just use C<yield()> in your |
70f2e746 DM |
358 | code. |
359 | ||
f4cc38af | 360 | =item threads->list() |
678a9b6c | 361 | |
ead32952 JH |
362 | =item threads->list(threads::all) |
363 | ||
364 | =item threads->list(threads::running) | |
365 | ||
366 | =item threads->list(threads::joinable) | |
367 | ||
368 | With no arguments (or using C<threads::all>) and in a list context, returns a | |
369 | list of all non-joined, non-detached I<threads> objects. In a scalar context, | |
370 | returns a count of the same. | |
371 | ||
372 | With a I<true> argument (using C<threads::running>), returns a list of all | |
373 | non-detached I<threads> objects that are still running. | |
374 | ||
375 | With a I<false> argument (using C<threads::joinable>), returns a list of all | |
376 | non-joined, non-detached I<threads> objects that have finished running (i.e., | |
377 | for which C<-E<gt>join()> will not I<block>). | |
678a9b6c | 378 | |
0f1612a7 JH |
379 | =item $thr1->equal($thr2) |
380 | ||
381 | Tests if two threads objects are the same thread or not. This is overloaded | |
fcea4b7c | 382 | to the more natural forms: |
0f1612a7 JH |
383 | |
384 | if ($thr1 == $thr2) { | |
385 | print("Threads are the same\n"); | |
386 | } | |
fcea4b7c JH |
387 | # or |
388 | if ($thr1 != $thr2) { | |
389 | print("Threads differ\n"); | |
390 | } | |
0f1612a7 JH |
391 | |
392 | (Thread comparison is based on thread IDs.) | |
393 | ||
386c44e5 AB |
394 | =item async BLOCK; |
395 | ||
396 | C<async> creates a thread to execute the block immediately following | |
fcea4b7c JH |
397 | it. This block is treated as an anonymous subroutine, and so must have a |
398 | semi-colon after the closing brace. Like C<threads->create()>, C<async> | |
399 | returns a I<threads> object. | |
386c44e5 | 400 | |
f4cc38af JH |
401 | =item $thr->_handle() |
402 | ||
403 | This I<private> method returns the memory location of the internal thread | |
fcea4b7c JH |
404 | structure associated with a threads object. For Win32, this is a pointer to |
405 | the C<HANDLE> value returned by C<CreateThread> (i.e., C<HANDLE *>); for other | |
406 | platforms, it is a pointer to the C<pthread_t> structure used in the | |
404aaa48 | 407 | C<pthread_create> call (i.e., C<pthread_t *>). |
f4cc38af JH |
408 | |
409 | This method is of no use for general Perl threads programming. Its intent is | |
410 | to provide other (XS-based) thread modules with the capability to access, and | |
411 | possibly manipulate, the underlying thread structure associated with a Perl | |
412 | thread. | |
413 | ||
414 | =item threads->_handle() | |
415 | ||
416 | Class method that allows a thread to obtain its own I<handle>. | |
417 | ||
47ba8780 AB |
418 | =back |
419 | ||
69a9b4b8 RGS |
420 | =head1 EXITING A THREAD |
421 | ||
422 | The usual method for terminating a thread is to | |
423 | L<return()|perlfunc/"return EXPR"> from the entry point function with the | |
424 | appropriate return value(s). | |
425 | ||
426 | =over | |
427 | ||
428 | =item threads->exit() | |
429 | ||
430 | If needed, a thread can be exited at any time by calling | |
431 | C<threads-E<gt>exit()>. This will cause the thread to return C<undef> in a | |
432 | scalar context, or the empty list in a list context. | |
433 | ||
434 | When called from the I<main> thread, this behaves the same as C<exit(0)>. | |
435 | ||
436 | =item threads->exit(status) | |
437 | ||
438 | When called from a thread, this behaves like C<threads-E<gt>exit()> (i.e., the | |
439 | exit status code is ignored). | |
440 | ||
441 | When called from the I<main> thread, this behaves the same as C<exit(status)>. | |
442 | ||
443 | =item die() | |
444 | ||
445 | Calling C<die()> in a thread indicates an abnormal exit for the thread. Any | |
446 | C<$SIG{__DIE__}> handler in the thread will be called first, and then the | |
447 | thread will exit with a warning message that will contain any arguments passed | |
448 | in the C<die()> call. | |
449 | ||
450 | =item exit(status) | |
451 | ||
452 | Calling L<exit()|perlfunc/"exit EXPR"> inside a thread causes the whole | |
453 | application to terminate. Because of this, the use of C<exit()> inside | |
454 | threaded code, or in modules that might be used in threaded applications, is | |
455 | strongly discouraged. | |
456 | ||
457 | If C<exit()> really is needed, then consider using the following: | |
458 | ||
60bd5ef6 | 459 | threads->exit() if threads->can('exit'); # Thread friendly |
69a9b4b8 RGS |
460 | exit(status); |
461 | ||
462 | =item use threads 'exit' => 'thread_only' | |
463 | ||
464 | This globally overrides the default behavior of calling C<exit()> inside a | |
465 | thread, and effectively causes such calls to behave the same as | |
466 | C<threads-E<gt>exit()>. In other words, with this setting, calling C<exit()> | |
467 | causes only the thread to terminate. | |
468 | ||
469 | Because of its global effect, this setting should not be used inside modules | |
470 | or the like. | |
471 | ||
472 | The I<main> thread is unaffected by this setting. | |
473 | ||
474 | =item threads->create({'exit' => 'thread_only'}, ...) | |
475 | ||
476 | This overrides the default behavior of C<exit()> inside the newly created | |
477 | thread only. | |
478 | ||
479 | =item $thr->set_thread_exit_only(boolean) | |
480 | ||
481 | This can be used to change the I<exit thread only> behavior for a thread after | |
482 | it has been created. With a I<true> argument, C<exit()> will cause the only | |
483 | the thread to exit. With a I<false> argument, C<exit()> will terminate the | |
484 | application. | |
485 | ||
486 | The I<main> thread is unaffected by this call. | |
487 | ||
488 | =item threads->set_thread_exit_only(boolean) | |
489 | ||
490 | Class method for use inside a thread to changes its own behavior for | |
491 | C<exit()>. | |
492 | ||
493 | The I<main> thread is unaffected by this call. | |
494 | ||
495 | =back | |
496 | ||
ead32952 JH |
497 | =head1 THREAD STATE |
498 | ||
499 | The following boolean methods are useful in determining the I<state> of a | |
500 | thread. | |
501 | ||
502 | =over | |
503 | ||
504 | =item $thr->is_running() | |
505 | ||
506 | Returns true if a thread is still running (i.e., if its entry point function | |
507 | has not yet finished/exited). | |
508 | ||
509 | =item $thr->is_joinable() | |
510 | ||
511 | Returns true if the thread has finished running, is not detached and has not | |
512 | yet been joined. In other works, the thread is ready to be joined and will | |
513 | not I<block>. | |
514 | ||
515 | =item $thr->is_detached() | |
516 | ||
517 | Returns true if the thread has been detached. | |
518 | ||
519 | =item threads->is_detached() | |
520 | ||
521 | Class method that allows a thread to determine whether or not it is detached. | |
522 | ||
523 | =back | |
524 | ||
9d9ff5b1 JH |
525 | =head1 THREAD CONTEXT |
526 | ||
527 | As with subroutines, the type of value returned from a thread's entry point | |
528 | function may be determined by the thread's I<context>: list, scalar or void. | |
529 | The thread's context is determined at thread creation. This is necessary so | |
530 | that the context is available to the entry point function via | |
206f4df7 | 531 | L<wantarray()|perlfunc/"wantarray">. The thread may then specify a value of |
9d9ff5b1 JH |
532 | the appropriate type to be returned from C<-E<gt>join()>. |
533 | ||
534 | =head2 Explicit context | |
535 | ||
536 | Because thread creation and thread joining may occur in different contexts, it | |
537 | may be desirable to state the context explicitly to the thread's entry point | |
538 | function. This may be done by calling C<-E<gt>create()> with a parameter hash | |
539 | as the first argument: | |
540 | ||
541 | my $thr = threads->create({'context' => 'list'}, \&foo); | |
542 | ... | |
543 | my @results = $thr->join(); | |
544 | ||
545 | In the above, the threads object is returned to the parent thread in scalar | |
546 | context, and the thread's entry point function C<foo> will be called in list | |
547 | context such that the parent thread can receive a list from the C<-E<gt>join()> | |
548 | call. Similarly, if you need the threads object, but your thread will not be | |
549 | returning a value (i.e., I<void> context), you would do the following: | |
550 | ||
551 | my $thr = threads->create({'context' => 'void'}, \&foo); | |
552 | ... | |
553 | $thr->join(); | |
554 | ||
555 | The context type may also be used as the I<key> in the parameter hash followed | |
556 | by a I<true> value: | |
557 | ||
558 | threads->create({'scalar' => 1}, \&foo); | |
559 | ... | |
560 | my ($thr) = threads->list(); | |
561 | my $result = $thr->join(); | |
562 | ||
563 | =head2 Implicit context | |
564 | ||
565 | If not explicitly stated, the thread's context is implied from the context | |
566 | of the C<-E<gt>create()> call: | |
567 | ||
568 | # Create thread in list context | |
569 | my ($thr) = threads->create(...); | |
570 | ||
571 | # Create thread in scalar context | |
572 | my $thr = threads->create(...); | |
573 | ||
574 | # Create thread in void context | |
575 | threads->create(...); | |
576 | ||
ead32952 JH |
577 | =head2 $thr->wantarray() |
578 | ||
579 | This returns the thread's context in the same manner as | |
580 | L<wantarray()|perlfunc/"wantarray">. | |
581 | ||
582 | =head2 threads->wantarray() | |
583 | ||
584 | Class method to return the current thread's context. This is the same as | |
585 | running L<wantarray()|perlfunc/"wantarray"> in the current thread. | |
586 | ||
514612b7 JH |
587 | =head1 THREAD STACK SIZE |
588 | ||
589 | The default per-thread stack size for different platforms varies | |
590 | significantly, and is almost always far more than is needed for most | |
591 | applications. On Win32, Perl's makefile explicitly sets the default stack to | |
592 | 16 MB; on most other platforms, the system default is used, which again may be | |
593 | much larger than is needed. | |
594 | ||
595 | By tuning the stack size to more accurately reflect your application's needs, | |
596 | you may significantly reduce your application's memory usage, and increase the | |
597 | number of simultaneously running threads. | |
598 | ||
599 | N.B., on Windows, Address space allocation granularity is 64 KB, therefore, | |
600 | setting the stack smaller than that on Win32 Perl will not save any more | |
601 | memory. | |
602 | ||
603 | =over | |
604 | ||
605 | =item threads->get_stack_size(); | |
606 | ||
607 | Returns the current default per-thread stack size. The default is zero, which | |
608 | means the system default stack size is currently in use. | |
609 | ||
610 | =item $size = $thr->get_stack_size(); | |
611 | ||
612 | Returns the stack size for a particular thread. A return value of zero | |
613 | indicates the system default stack size was used for the thread. | |
614 | ||
615 | =item $old_size = threads->set_stack_size($new_size); | |
616 | ||
617 | Sets a new default per-thread stack size, and returns the previous setting. | |
618 | ||
619 | Some platforms have a minimum thread stack size. Trying to set the stack size | |
620 | below this value will result in a warning, and the minimum stack size will be | |
621 | used. | |
622 | ||
623 | Some Linux platforms have a maximum stack size. Setting too large of a stack | |
624 | size will cause thread creation to fail. | |
625 | ||
626 | If needed, C<$new_size> will be rounded up to the next multiple of the memory | |
627 | page size (usually 4096 or 8192). | |
628 | ||
629 | Threads created after the stack size is set will then either call | |
630 | C<pthread_attr_setstacksize()> I<(for pthreads platforms)>, or supply the | |
631 | stack size to C<CreateThread()> I<(for Win32 Perl)>. | |
632 | ||
633 | (Obviously, this call does not affect any currently extant threads.) | |
634 | ||
635 | =item use threads ('stack_size' => VALUE); | |
636 | ||
637 | This sets the default per-thread stack size at the start of the application. | |
638 | ||
639 | =item $ENV{'PERL5_ITHREADS_STACK_SIZE'} | |
640 | ||
641 | The default per-thread stack size may be set at the start of the application | |
642 | through the use of the environment variable C<PERL5_ITHREADS_STACK_SIZE>: | |
643 | ||
644 | PERL5_ITHREADS_STACK_SIZE=1048576 | |
645 | export PERL5_ITHREADS_STACK_SIZE | |
646 | perl -e'use threads; print(threads->get_stack_size(), "\n")' | |
647 | ||
648 | This value overrides any C<stack_size> parameter given to C<use threads>. Its | |
649 | primary purpose is to permit setting the per-thread stack size for legacy | |
650 | threaded applications. | |
651 | ||
652 | =item threads->create({'stack_size' => VALUE}, FUNCTION, ARGS) | |
653 | ||
9d9ff5b1 JH |
654 | The stack size an individual threads may also be specified. This may be done |
655 | by calling C<-E<gt>create()> with a parameter hash as the first argument: | |
656 | ||
657 | my $thr = threads->create({'stack_size' => 32*4096}, \&foo, @args); | |
514612b7 JH |
658 | |
659 | =item $thr2 = $thr1->create(FUNCTION, ARGS) | |
660 | ||
661 | This creates a new thread (C<$thr2>) that inherits the stack size from an | |
662 | existing thread (C<$thr1>). This is shorthand for the following: | |
663 | ||
664 | my $stack_size = $thr1->get_stack_size(); | |
665 | my $thr2 = threads->create({'stack_size' => $stack_size}, FUNCTION, ARGS); | |
666 | ||
667 | =back | |
668 | ||
c0003851 JH |
669 | =head1 THREAD SIGNALLING |
670 | ||
9d9ff5b1 | 671 | When safe signals is in effect (the default behavior - see L</"Unsafe signals"> |
1152d448 JH |
672 | for more details), then signals may be sent and acted upon by individual |
673 | threads. | |
c0003851 JH |
674 | |
675 | =over 4 | |
676 | ||
677 | =item $thr->kill('SIG...'); | |
678 | ||
679 | Sends the specified signal to the thread. Signal names and (positive) signal | |
680 | numbers are the same as those supported by | |
681 | L<kill()|perlfunc/"kill SIGNAL, LIST">. For example, 'SIGTERM', 'TERM' and | |
682 | (depending on the OS) 15 are all valid arguments to C<-E<gt>kill()>. | |
683 | ||
684 | Returns the thread object to allow for method chaining: | |
685 | ||
686 | $thr->kill('SIG...')->join(); | |
687 | ||
688 | =back | |
689 | ||
690 | Signal handlers need to be set up in the threads for the signals they are | |
691 | expected to act upon. Here's an example for I<cancelling> a thread: | |
692 | ||
693 | use threads; | |
694 | ||
c0003851 JH |
695 | sub thr_func |
696 | { | |
697 | # Thread 'cancellation' signal handler | |
c608f8c0 | 698 | $SIG{'KILL'} = sub { threads->exit(); }; |
c0003851 JH |
699 | |
700 | ... | |
701 | } | |
702 | ||
703 | # Create a thread | |
704 | my $thr = threads->create('thr_func'); | |
705 | ||
706 | ... | |
707 | ||
708 | # Signal the thread to terminate, and then detach | |
709 | # it so that it will get cleaned up automatically | |
710 | $thr->kill('KILL')->detach(); | |
711 | ||
404aaa48 JH |
712 | Here's another simplistic example that illustrates the use of thread |
713 | signalling in conjunction with a semaphore to provide rudimentary I<suspend> | |
714 | and I<resume> capabilities: | |
c0003851 JH |
715 | |
716 | use threads; | |
717 | use Thread::Semaphore; | |
718 | ||
719 | sub thr_func | |
720 | { | |
721 | my $sema = shift; | |
722 | ||
723 | # Thread 'suspend/resume' signal handler | |
724 | $SIG{'STOP'} = sub { | |
725 | $sema->down(); # Thread suspended | |
726 | $sema->up(); # Thread resumes | |
727 | }; | |
728 | ||
729 | ... | |
730 | } | |
731 | ||
732 | # Create a semaphore and send it to a thread | |
733 | my $sema = Thread::Semaphore->new(); | |
734 | my $thr = threads->create('thr_func', $sema); | |
735 | ||
736 | # Suspend the thread | |
737 | $sema->down(); | |
738 | $thr->kill('STOP'); | |
739 | ||
740 | ... | |
741 | ||
742 | # Allow the thread to continue | |
743 | $sema->up(); | |
744 | ||
404aaa48 JH |
745 | CAVEAT: The thread signalling capability provided by this module does not |
746 | actually send signals via the OS. It I<emulates> signals at the Perl-level | |
747 | such that signal handlers are called in the appropriate thread. For example, | |
748 | sending C<$thr-E<gt>kill('STOP')> does not actually suspend a thread (or the | |
749 | whole process), but does cause a C<$SIG{'STOP'}> handler to be called in that | |
750 | thread (as illustrated above). | |
751 | ||
752 | As such, signals that would normally not be appropriate to use in the | |
753 | C<kill()> command (e.g., C<kill('KILL', $$)>) are okay to use with the | |
754 | C<-E<gt>kill()> method (again, as illustrated above). | |
755 | ||
756 | Correspondingly, sending a signal to a thread does not disrupt the operation | |
757 | the thread is currently working on: The signal will be acted upon after the | |
c0003851 JH |
758 | current operation has completed. For instance, if the thread is I<stuck> on |
759 | an I/O call, sending it a signal will not cause the I/O call to be interrupted | |
760 | such that the signal is acted up immediately. | |
761 | ||
69a9b4b8 RGS |
762 | Sending a signal to a terminated thread is ignored. |
763 | ||
e4f9f4fe JH |
764 | =head1 WARNINGS |
765 | ||
766 | =over 4 | |
767 | ||
4dcb9e53 | 768 | =item Perl exited with active threads: |
e4f9f4fe | 769 | |
4dcb9e53 JH |
770 | If the program exits without all threads having either been joined or |
771 | detached, then this warning will be issued. | |
772 | ||
69a9b4b8 RGS |
773 | NOTE: If the I<main> thread exits, then this warning cannot be suppressed |
774 | using C<no warnings 'threads';> as suggested below. | |
e4f9f4fe | 775 | |
c0003851 JH |
776 | =item Thread creation failed: pthread_create returned # |
777 | ||
778 | See the appropriate I<man> page for C<pthread_create> to determine the actual | |
779 | cause for the failure. | |
780 | ||
781 | =item Thread # terminated abnormally: ... | |
782 | ||
783 | A thread terminated in some manner other than just returning from its entry | |
4dcb9e53 | 784 | point function. For example, the thread may have terminated using C<die>. |
c0003851 | 785 | |
514612b7 JH |
786 | =item Using minimum thread stack size of # |
787 | ||
788 | Some platforms have a minimum thread stack size. Trying to set the stack size | |
789 | below this value will result in the above warning, and the stack size will be | |
790 | set to the minimum. | |
791 | ||
c0003851 JH |
792 | =item Thread creation failed: pthread_attr_setstacksize(I<SIZE>) returned 22 |
793 | ||
794 | The specified I<SIZE> exceeds the system's maximum stack size. Use a smaller | |
795 | value for the stack size. | |
796 | ||
e4f9f4fe | 797 | =back |
47ba8780 | 798 | |
c0003851 JH |
799 | If needed, thread warnings can be suppressed by using: |
800 | ||
801 | no warnings 'threads'; | |
802 | ||
803 | in the appropriate scope. | |
804 | ||
0f1612a7 JH |
805 | =head1 ERRORS |
806 | ||
807 | =over 4 | |
808 | ||
fcea4b7c | 809 | =item This Perl not built to support threads |
678a9b6c | 810 | |
0f1612a7 JH |
811 | The particular copy of Perl that you're trying to use was not built using the |
812 | C<useithreads> configuration option. | |
678a9b6c | 813 | |
0f1612a7 JH |
814 | Having threads support requires all of Perl and all of the XS modules in the |
815 | Perl installation to be rebuilt; it is not just a question of adding the | |
816 | L<threads> module (i.e., threaded and non-threaded Perls are binary | |
817 | incompatible.) | |
818 | ||
514612b7 JH |
819 | =item Cannot change stack size of an existing thread |
820 | ||
821 | The stack size of currently extant threads cannot be changed, therefore, the | |
822 | following results in the above error: | |
823 | ||
824 | $thr->set_stack_size($size); | |
825 | ||
4dcb9e53 | 826 | =item Cannot signal threads without safe signals |
514612b7 | 827 | |
1152d448 | 828 | Safe signals must be in effect to use the C<-E<gt>kill()> signalling method. |
9d9ff5b1 | 829 | See L</"Unsafe signals"> for more details. |
c0003851 JH |
830 | |
831 | =item Unrecognized signal name: ... | |
832 | ||
833 | The particular copy of Perl that you're trying to use does not support the | |
834 | specified signal being used in a C<-E<gt>kill()> call. | |
514612b7 | 835 | |
0f1612a7 | 836 | =back |
47ba8780 | 837 | |
5c6ff896 JH |
838 | =head1 LIMITATIONS |
839 | ||
840 | =over | |
841 | ||
842 | =item Using non-threadsafe modules | |
843 | ||
844 | Unfortunately, you may encounter Perl modules are not I<threadsafe>. For | |
845 | example, they may crash the Perl interpreter during execution, or may dump | |
846 | core on termination. Depending on the module and the requirements of your | |
847 | application, it may be possible to work around such difficulties. | |
848 | ||
849 | If the module will only be used inside a thread, you can try loading the | |
850 | module from inside the thread entry point function using C<require> (and | |
851 | C<import> if needed): | |
852 | ||
853 | sub thr_func | |
854 | { | |
855 | require Unsafe::Module | |
856 | # import Unsafe::Module ...; | |
857 | ||
858 | .... | |
859 | } | |
860 | ||
861 | If the module will only be used inside the I<main> thread, try modifying your | |
862 | application so that the module is loaded (again using C<require> and C<import>) | |
863 | after any threads are started, and in such a way that no other threads are | |
864 | started afterwards. | |
865 | ||
866 | If the above does not work, or is not adequate for your application, then file | |
867 | a bug report on L<http://rt.cpan.org/Public/> against the problematic module. | |
868 | ||
869 | =back | |
870 | ||
ab80e3f2 EM |
871 | =head1 BUGS |
872 | ||
5c6ff896 JH |
873 | Before you consider posting a bug report, please consult, and possibly post a |
874 | message to the discussion forum to see if what you've encountered is a known | |
875 | problem. | |
876 | ||
47ba8780 AB |
877 | =over |
878 | ||
fcea4b7c | 879 | =item Parent-child threads |
678a9b6c | 880 | |
fcea4b7c JH |
881 | On some platforms, it might not be possible to destroy I<parent> threads while |
882 | there are still existing I<child> threads. | |
678a9b6c | 883 | |
404aaa48 | 884 | =item Creating threads inside special blocks |
88f8c1df | 885 | |
f2e0bb91 JH |
886 | Creating threads inside C<BEGIN>, C<CHECK> or C<INIT> blocks should not be |
887 | relied upon. Depending on the Perl version and the application code, results | |
58a3a76c | 888 | may range from success, to (apparently harmless) warnings of leaked scalar, or |
f2e0bb91 | 889 | all the way up to crashing of the Perl interpreter. |
88f8c1df | 890 | |
1152d448 | 891 | =item Unsafe signals |
47ba8780 | 892 | |
1152d448 JH |
893 | Since Perl 5.8.0, signals have been made safer in Perl by postponing their |
894 | handling until the interpreter is in a I<safe> state. See | |
404aaa48 | 895 | L<perl58delta/"Safe Signals"> and L<perlipc/"Deferred Signals (Safe Signals)"> |
1152d448 JH |
896 | for more details. |
897 | ||
898 | Safe signals is the default behavior, and the old, immediate, unsafe | |
899 | signalling behavior is only in effect in the following situations: | |
900 | ||
901 | =over 4 | |
902 | ||
903 | =item * Perl was been built with C<PERL_OLD_SIGNALS> (see C<perl -V>). | |
904 | ||
905 | =item * The environment variable C<PERL_SIGNALS> is set to C<unsafe> (see L<perlrun/"PERL_SIGNALS">). | |
906 | ||
907 | =item * The module L<Perl::Unsafe::Signals> is used. | |
908 | ||
909 | =back | |
910 | ||
911 | If unsafe signals is in effect, then signal handling is not thread-safe, and | |
912 | the C<-E<gt>kill()> signalling method cannot be used. | |
88f8c1df | 913 | |
0f1612a7 JH |
914 | =item Returning closures from threads |
915 | ||
f2e0bb91 JH |
916 | Returning closures from threads should not be relied upon. Depending of the |
917 | Perl version and the application code, results may range from success, to | |
58a3a76c JH |
918 | (apparently harmless) warnings of leaked scalar, or all the way up to crashing |
919 | of the Perl interpreter. | |
0f1612a7 JH |
920 | |
921 | =item Perl Bugs and the CPAN Version of L<threads> | |
922 | ||
923 | Support for threads extents beyond the code in this module (i.e., | |
924 | F<threads.pm> and F<threads.xs>), and into the Perl iterpreter itself. Older | |
925 | versions of Perl contain bugs that may manifest themselves despite using the | |
926 | latest version of L<threads> from CPAN. There is no workaround for this other | |
927 | than upgrading to the lastest version of Perl. | |
928 | ||
47ba8780 AB |
929 | =back |
930 | ||
0f1612a7 | 931 | =head1 REQUIREMENTS |
47ba8780 | 932 | |
0f1612a7 | 933 | Perl 5.8.0 or later |
47ba8780 | 934 | |
0f1612a7 | 935 | =head1 SEE ALSO |
47ba8780 | 936 | |
0f1612a7 JH |
937 | L<threads> Discussion Forum on CPAN: |
938 | L<http://www.cpanforum.com/dist/threads> | |
47ba8780 | 939 | |
0f1612a7 | 940 | Annotated POD for L<threads>: |
894eec8b | 941 | L<http://annocpan.org/~JDHEDDEN/threads-1.53/threads.pm> |
47ba8780 | 942 | |
0f1612a7 | 943 | L<threads::shared>, L<perlthrtut> |
47ba8780 | 944 | |
0f1612a7 JH |
945 | L<http://www.perl.com/pub/a/2002/06/11/threads.html> and |
946 | L<http://www.perl.com/pub/a/2002/09/04/threads.html> | |
47ba8780 | 947 | |
0f1612a7 JH |
948 | Perl threads mailing list: |
949 | L<http://lists.cpan.org/showlist.cgi?name=iThreads> | |
47ba8780 | 950 | |
514612b7 JH |
951 | Stack size discussion: |
952 | L<http://www.perlmonks.org/?node_id=532956> | |
953 | ||
0f1612a7 | 954 | =head1 AUTHOR |
47ba8780 | 955 | |
0f1612a7 JH |
956 | Artur Bergman E<lt>sky AT crucially DOT netE<gt> |
957 | ||
958 | threads is released under the same license as Perl. | |
959 | ||
960 | CPAN version produced by Jerry D. Hedden <jdhedden AT cpan DOT org> | |
961 | ||
962 | =head1 ACKNOWLEDGEMENTS | |
963 | ||
964 | Richard Soderberg E<lt>perl AT crystalflame DOT netE<gt> - | |
965 | Helping me out tons, trying to find reasons for races and other weird bugs! | |
966 | ||
967 | Simon Cozens E<lt>simon AT brecon DOT co DOT ukE<gt> - | |
968 | Being there to answer zillions of annoying questions | |
969 | ||
970 | Rocco Caputo E<lt>troc AT netrus DOT netE<gt> | |
47ba8780 | 971 | |
0f1612a7 JH |
972 | Vipul Ved Prakash E<lt>mail AT vipul DOT netE<gt> - |
973 | Helping with debugging | |
47ba8780 | 974 | |
514612b7 JH |
975 | Dean Arnold E<lt>darnold AT presicient DOT comE<gt> - |
976 | Stack size API | |
977 | ||
47ba8780 | 978 | =cut |