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 | |
955c272e | 8 | our $VERSION = '1.54'; |
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 | ||
955c272e | 136 | This document describes threads version 1.54 |
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(); | |
955c272e JH |
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 JH |
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 JH |
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 JH |
180 | yield(); |
181 | ||
69a9b4b8 | 182 | # Lists of non-detached threads |
0f1612a7 | 183 | my @threads = threads->list(); |
fcea4b7c | 184 | my $thread_count = threads->list(); |
f9dff5f5 | 185 | |
ead32952 JH |
186 | my @running = threads->list(threads::running); |
187 | my @joinable = threads->list(threads::joinable); | |
188 | ||
69a9b4b8 | 189 | # Test thread objects |
0f1612a7 JH |
190 | if ($thr1 == $thr2) { |
191 | ... | |
192 | } | |
678a9b6c | 193 | |
69a9b4b8 | 194 | # Manage thread stack size |
514612b7 JH |
195 | $stack_size = threads->get_stack_size(); |
196 | $old_size = threads->set_stack_size(32*4096); | |
197 | ||
9d9ff5b1 JH |
198 | # Create a thread with a specific context and stack size |
199 | my $thr = threads->create({ 'context' => 'list', | |
69a9b4b8 RGS |
200 | 'stack_size' => 32*4096, |
201 | 'exit' => 'thread_only' }, | |
9d9ff5b1 | 202 | \&foo); |
ead32952 JH |
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 JH |
216 | $thr->kill('SIGUSR1'); |
217 | ||
69a9b4b8 | 218 | # Exit a thread |
4dcb9e53 JH |
219 | threads->exit(); |
220 | ||
47ba8780 AB |
221 | =head1 DESCRIPTION |
222 | ||
fc04eb16 JH |
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 JH |
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 JH |
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 JH |
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 AB |
242 | |
243 | =over | |
244 | ||
0f1612a7 | 245 | =item $thr = threads->create(FUNCTION, ARGS) |
47ba8780 | 246 | |
0f1612a7 JH |
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 JH |
251 | I<FUNCTION> may either be the name of a function, an anonymous subroutine, or |
252 | a code ref. | |
47ba8780 | 253 | |
0f1612a7 JH |
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 JH |
260 | The C<-E<gt>new()> method is an alias for C<-E<gt>create()>. |
261 | ||
262 | =item $thr->join() | |
263 | ||
264 | This will wait for the corresponding thread to complete its execution. When | |
265 | the thread finishes, C<-E<gt>join()> will return the return value(s) of the | |
266 | entry point function. | |
267 | ||
9d9ff5b1 JH |
268 | The context (void, scalar or list) for the return value(s) for C<-E<gt>join()> |
269 | is determined at the time of thread creation. | |
0f1612a7 | 270 | |
9d9ff5b1 | 271 | # Create thread in list context (implicit) |
0f1612a7 JH |
272 | my ($thr1) = threads->create(sub { |
273 | my @results = qw(a b c); | |
274 | return (@results); | |
9d9ff5b1 JH |
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 JH |
282 | # Retrieve list results from thread |
283 | my @res1 = $thr1->join(); | |
284 | ||
9d9ff5b1 | 285 | # Create thread in scalar context (implicit) |
0f1612a7 JH |
286 | my $thr2 = threads->create(sub { |
287 | my $result = 42; | |
288 | return ($result); | |
9d9ff5b1 | 289 | }); |
0f1612a7 JH |
290 | # Retrieve scalar result from thread |
291 | my $res2 = $thr2->join(); | |
292 | ||
9d9ff5b1 JH |
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 JH |
301 | If the program exits without all threads having either been joined or |
302 | detached, then a warning will be issued. | |
93512b4d | 303 | |
fcea4b7c JH |
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 JH |
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 JH |
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 JH |
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 JH |
327 | =item $thr->tid() |
328 | ||
329 | Returns the ID of the thread. Thread IDs are unique integers with the main | |
330 | thread in a program being 0, and incrementing by 1 for every thread created. | |
47ba8780 | 331 | |
0f1612a7 | 332 | =item threads->tid() |
38875929 | 333 | |
0f1612a7 | 334 | Class method that allows a thread to obtain its own ID. |
47ba8780 | 335 | |
3ab14376 JH |
336 | =item "$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 JH |
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 JH |
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 DM |
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 DM |
361 | code. |
362 | ||
f4cc38af | 363 | =item threads->list() |
678a9b6c | 364 | |
ead32952 JH |
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 | |
376 | non-detached I<threads> objects that are still running. | |
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 JH |
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 JH |
386 | |
387 | if ($thr1 == $thr2) { | |
388 | print("Threads are the same\n"); | |
389 | } | |
fcea4b7c JH |
390 | # or |
391 | if ($thr1 != $thr2) { | |
392 | print("Threads differ\n"); | |
393 | } | |
0f1612a7 JH |
394 | |
395 | (Thread comparison is based on thread IDs.) | |
396 | ||
386c44e5 AB |
397 | =item async BLOCK; |
398 | ||
399 | C<async> creates a thread to execute the block immediately following | |
fcea4b7c JH |
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 JH |
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 JH |
410 | =item $thr->_handle() |
411 | ||
412 | This I<private> method returns the memory location of the internal thread | |
fcea4b7c JH |
413 | structure associated with a threads object. For Win32, this is a pointer to |
414 | the C<HANDLE> value returned by C<CreateThread> (i.e., C<HANDLE *>); for other | |
415 | platforms, it is a pointer to the C<pthread_t> structure used in the | |
404aaa48 | 416 | C<pthread_create> call (i.e., C<pthread_t *>). |
f4cc38af JH |
417 | |
418 | This method is of no use for general Perl threads programming. Its intent is | |
419 | to provide other (XS-based) thread modules with the capability to access, and | |
420 | possibly manipulate, the underlying thread structure associated with a Perl | |
421 | thread. | |
422 | ||
423 | =item threads->_handle() | |
424 | ||
425 | Class method that allows a thread to obtain its own I<handle>. | |
426 | ||
47ba8780 AB |
427 | =back |
428 | ||
69a9b4b8 RGS |
429 | =head1 EXITING A THREAD |
430 | ||
431 | The usual method for terminating a thread is to | |
432 | L<return()|perlfunc/"return EXPR"> from the entry point function with the | |
433 | appropriate return value(s). | |
434 | ||
435 | =over | |
436 | ||
437 | =item threads->exit() | |
438 | ||
439 | If needed, a thread can be exited at any time by calling | |
440 | C<threads-E<gt>exit()>. This will cause the thread to return C<undef> in a | |
441 | scalar context, or the empty list in a list context. | |
442 | ||
443 | When called from the I<main> thread, this behaves the same as C<exit(0)>. | |
444 | ||
445 | =item threads->exit(status) | |
446 | ||
447 | When called from a thread, this behaves like C<threads-E<gt>exit()> (i.e., the | |
448 | exit status code is ignored). | |
449 | ||
450 | When called from the I<main> thread, this behaves the same as C<exit(status)>. | |
451 | ||
452 | =item die() | |
453 | ||
454 | Calling C<die()> in a thread indicates an abnormal exit for the thread. Any | |
455 | C<$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 RGS |
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 JH |
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 JH |
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 JH |
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 JH |
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 JH |
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 JH |
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 JH |
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 JH |
678 | =head1 THREAD SIGNALLING |
679 | ||
9d9ff5b1 | 680 | When safe signals is in effect (the default behavior - see L</"Unsafe signals"> |
1152d448 JH |
681 | for more details), then signals may be sent and acted upon by individual |
682 | threads. | |
c0003851 JH |
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 JH |
704 | sub thr_func |
705 | { | |
706 | # Thread 'cancellation' signal handler | |
c608f8c0 | 707 | $SIG{'KILL'} = sub { threads->exit(); }; |
c0003851 JH |
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 JH |
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 JH |
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 | $sema->up(); | |
753 | ||
404aaa48 JH |
754 | CAVEAT: The thread signalling capability provided by this module does not |
755 | actually send signals via the OS. It I<emulates> signals at the Perl-level | |
756 | such that signal handlers are called in the appropriate thread. For example, | |
757 | sending C<$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 JH |
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 RGS |
771 | Sending a signal to a terminated thread is ignored. |
772 | ||
e4f9f4fe JH |
773 | =head1 WARNINGS |
774 | ||
775 | =over 4 | |
776 | ||
4dcb9e53 | 777 | =item Perl exited with active threads: |
e4f9f4fe | 778 | |
4dcb9e53 JH |
779 | If the program exits without all threads having either been joined or |
780 | detached, then this warning will be issued. | |
781 | ||
69a9b4b8 RGS |
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 JH |
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 JH |
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 JH |
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 JH |
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 JH |
809 | If needed, thread warnings can be suppressed by using: |
810 | ||
811 | no warnings 'threads'; | |
812 | ||
813 | in the appropriate scope. | |
814 | ||
0f1612a7 JH |
815 | =head1 ERRORS |
816 | ||
817 | =over 4 | |
818 | ||
fcea4b7c | 819 | =item This Perl not built to support threads |
678a9b6c | 820 | |
0f1612a7 JH |
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 JH |
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 JH |
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 JH |
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 | |
5c6ff896 JH |
848 | =head1 LIMITATIONS |
849 | ||
850 | =over | |
851 | ||
852 | =item Using non-threadsafe modules | |
853 | ||
854 | Unfortunately, you may encounter Perl modules are not I<threadsafe>. For | |
855 | example, they may crash the Perl interpreter during execution, or may dump | |
856 | core on termination. Depending on the module and the requirements of your | |
857 | application, it may be possible to work around such difficulties. | |
858 | ||
859 | If the module will only be used inside a thread, you can try loading the | |
860 | module from inside the thread entry point function using C<require> (and | |
861 | C<import> if needed): | |
862 | ||
863 | sub thr_func | |
864 | { | |
865 | require Unsafe::Module | |
866 | # import Unsafe::Module ...; | |
867 | ||
868 | .... | |
869 | } | |
870 | ||
955c272e JH |
871 | If the module is needed inside the I<main> thread, try modifying your |
872 | application so that the module is loaded (again using C<require> and | |
873 | C<import>) after any threads are started, and in such a way that no other | |
874 | threads are started afterwards. | |
5c6ff896 JH |
875 | |
876 | If the above does not work, or is not adequate for your application, then file | |
877 | a bug report on L<http://rt.cpan.org/Public/> against the problematic module. | |
878 | ||
879 | =back | |
880 | ||
ab80e3f2 EM |
881 | =head1 BUGS |
882 | ||
5c6ff896 JH |
883 | Before you consider posting a bug report, please consult, and possibly post a |
884 | message to the discussion forum to see if what you've encountered is a known | |
885 | problem. | |
886 | ||
47ba8780 AB |
887 | =over |
888 | ||
fcea4b7c | 889 | =item Parent-child threads |
678a9b6c | 890 | |
fcea4b7c JH |
891 | On some platforms, it might not be possible to destroy I<parent> threads while |
892 | there are still existing I<child> threads. | |
678a9b6c | 893 | |
404aaa48 | 894 | =item Creating threads inside special blocks |
88f8c1df | 895 | |
f2e0bb91 JH |
896 | Creating threads inside C<BEGIN>, C<CHECK> or C<INIT> blocks should not be |
897 | relied upon. Depending on the Perl version and the application code, results | |
58a3a76c | 898 | may range from success, to (apparently harmless) warnings of leaked scalar, or |
f2e0bb91 | 899 | all the way up to crashing of the Perl interpreter. |
88f8c1df | 900 | |
1152d448 | 901 | =item Unsafe signals |
47ba8780 | 902 | |
1152d448 JH |
903 | Since Perl 5.8.0, signals have been made safer in Perl by postponing their |
904 | handling until the interpreter is in a I<safe> state. See | |
404aaa48 | 905 | L<perl58delta/"Safe Signals"> and L<perlipc/"Deferred Signals (Safe Signals)"> |
1152d448 JH |
906 | for more details. |
907 | ||
908 | Safe signals is the default behavior, and the old, immediate, unsafe | |
909 | signalling behavior is only in effect in the following situations: | |
910 | ||
911 | =over 4 | |
912 | ||
913 | =item * Perl was been built with C<PERL_OLD_SIGNALS> (see C<perl -V>). | |
914 | ||
915 | =item * The environment variable C<PERL_SIGNALS> is set to C<unsafe> (see L<perlrun/"PERL_SIGNALS">). | |
916 | ||
917 | =item * The module L<Perl::Unsafe::Signals> is used. | |
918 | ||
919 | =back | |
920 | ||
921 | If unsafe signals is in effect, then signal handling is not thread-safe, and | |
922 | the C<-E<gt>kill()> signalling method cannot be used. | |
88f8c1df | 923 | |
0f1612a7 JH |
924 | =item Returning closures from threads |
925 | ||
f2e0bb91 JH |
926 | Returning closures from threads should not be relied upon. Depending of the |
927 | Perl version and the application code, results may range from success, to | |
58a3a76c JH |
928 | (apparently harmless) warnings of leaked scalar, or all the way up to crashing |
929 | of the Perl interpreter. | |
0f1612a7 | 930 | |
955c272e JH |
931 | =item Returning objects from threads |
932 | ||
933 | Returning objects from threads does not work. | |
934 | ||
0f1612a7 JH |
935 | =item Perl Bugs and the CPAN Version of L<threads> |
936 | ||
937 | Support for threads extents beyond the code in this module (i.e., | |
938 | F<threads.pm> and F<threads.xs>), and into the Perl iterpreter itself. Older | |
939 | versions of Perl contain bugs that may manifest themselves despite using the | |
940 | latest version of L<threads> from CPAN. There is no workaround for this other | |
941 | than upgrading to the lastest version of Perl. | |
942 | ||
47ba8780 AB |
943 | =back |
944 | ||
0f1612a7 | 945 | =head1 REQUIREMENTS |
47ba8780 | 946 | |
0f1612a7 | 947 | Perl 5.8.0 or later |
47ba8780 | 948 | |
0f1612a7 | 949 | =head1 SEE ALSO |
47ba8780 | 950 | |
0f1612a7 JH |
951 | L<threads> Discussion Forum on CPAN: |
952 | L<http://www.cpanforum.com/dist/threads> | |
47ba8780 | 953 | |
0f1612a7 | 954 | Annotated POD for L<threads>: |
955c272e | 955 | L<http://annocpan.org/~JDHEDDEN/threads-1.54/threads.pm> |
47ba8780 | 956 | |
0f1612a7 | 957 | L<threads::shared>, L<perlthrtut> |
47ba8780 | 958 | |
0f1612a7 JH |
959 | L<http://www.perl.com/pub/a/2002/06/11/threads.html> and |
960 | L<http://www.perl.com/pub/a/2002/09/04/threads.html> | |
47ba8780 | 961 | |
0f1612a7 JH |
962 | Perl threads mailing list: |
963 | L<http://lists.cpan.org/showlist.cgi?name=iThreads> | |
47ba8780 | 964 | |
514612b7 JH |
965 | Stack size discussion: |
966 | L<http://www.perlmonks.org/?node_id=532956> | |
967 | ||
0f1612a7 | 968 | =head1 AUTHOR |
47ba8780 | 969 | |
0f1612a7 JH |
970 | Artur Bergman E<lt>sky AT crucially DOT netE<gt> |
971 | ||
972 | threads is released under the same license as Perl. | |
973 | ||
974 | CPAN version produced by Jerry D. Hedden <jdhedden AT cpan DOT org> | |
975 | ||
976 | =head1 ACKNOWLEDGEMENTS | |
977 | ||
978 | Richard Soderberg E<lt>perl AT crystalflame DOT netE<gt> - | |
979 | Helping me out tons, trying to find reasons for races and other weird bugs! | |
980 | ||
981 | Simon Cozens E<lt>simon AT brecon DOT co DOT ukE<gt> - | |
982 | Being there to answer zillions of annoying questions | |
983 | ||
984 | Rocco Caputo E<lt>troc AT netrus DOT netE<gt> | |
47ba8780 | 985 | |
0f1612a7 JH |
986 | Vipul Ved Prakash E<lt>mail AT vipul DOT netE<gt> - |
987 | Helping with debugging | |
47ba8780 | 988 | |
514612b7 JH |
989 | Dean Arnold E<lt>darnold AT presicient DOT comE<gt> - |
990 | Stack size API | |
991 | ||
47ba8780 | 992 | =cut |