Commit | Line | Data |
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47ba8780 AB |
1 | package threads; |
2 | ||
32419a4c | 3 | use 5.008; |
fcea4b7c | 4 | |
47ba8780 AB |
5 | use strict; |
6 | use warnings; | |
73e09c8f | 7 | |
3ceb02cd | 8 | our $VERSION = '1.36'; |
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 | # 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 AB |
31 | } |
32 | ||
fc04eb16 | 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 $sym = shift) { | |
514612b7 JH |
50 | if ($sym =~ /^stack/) { |
51 | threads->set_stack_size(shift); | |
52 | ||
53 | } elsif ($sym =~ /all/) { | |
0f1612a7 JH |
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 JH |
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 JH |
72 | } |
73 | ||
74 | ||
75 | ### Methods, etc. ### | |
47ba8780 | 76 | |
4dcb9e53 JH |
77 | # Our own exit function/method |
78 | sub exit | |
79 | { | |
80 | CORE::exit(0); | |
81 | } | |
82 | ||
ead32952 JH |
83 | # 'Constant' args for threads->list() |
84 | sub threads::all { } | |
85 | sub threads::running { 1 } | |
86 | sub threads::joinable { 0 } | |
87 | ||
f4cc38af JH |
88 | # 'new' is an alias for 'create' |
89 | *new = \&create; | |
68795e93 | 90 | |
fcea4b7c JH |
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 AB |
108 | __END__ |
109 | ||
110 | =head1 NAME | |
111 | ||
0f1612a7 JH |
112 | threads - Perl interpreter-based threads |
113 | ||
114 | =head1 VERSION | |
115 | ||
3ceb02cd | 116 | This document describes threads version 1.36 |
47ba8780 AB |
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 JH |
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 JH |
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 JH |
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 JH |
146 | $tid = threads->tid(); |
147 | $tid = threads->self->tid(); | |
148 | $tid = $thread->tid(); | |
47ba8780 | 149 | |
38875929 | 150 | threads->yield(); |
0f1612a7 JH |
151 | yield(); |
152 | ||
153 | my @threads = threads->list(); | |
fcea4b7c | 154 | my $thread_count = threads->list(); |
f9dff5f5 | 155 | |
ead32952 JH |
156 | my @running = threads->list(threads::running); |
157 | my @joinable = threads->list(threads::joinable); | |
158 | ||
0f1612a7 JH |
159 | if ($thr1 == $thr2) { |
160 | ... | |
161 | } | |
678a9b6c | 162 | |
514612b7 JH |
163 | $stack_size = threads->get_stack_size(); |
164 | $old_size = threads->set_stack_size(32*4096); | |
165 | ||
9d9ff5b1 JH |
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 JH |
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 JH |
182 | $thr->kill('SIGUSR1'); |
183 | ||
4dcb9e53 JH |
184 | threads->exit(); |
185 | ||
47ba8780 AB |
186 | =head1 DESCRIPTION |
187 | ||
fc04eb16 JH |
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 JH |
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 JH |
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 JH |
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 AB |
207 | |
208 | =over | |
209 | ||
0f1612a7 | 210 | =item $thr = threads->create(FUNCTION, ARGS) |
47ba8780 | 211 | |
0f1612a7 JH |
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 JH |
216 | I<FUNCTION> may either be the name of a function, an anonymous subroutine, or |
217 | a code ref. | |
47ba8780 | 218 | |
0f1612a7 JH |
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 JH |
225 | The C<-E<gt>new()> method is an alias for C<-E<gt>create()>. |
226 | ||
227 | =item $thr->join() | |
228 | ||
229 | This will wait for the corresponding thread to complete its execution. When | |
230 | the thread finishes, C<-E<gt>join()> will return the return value(s) of the | |
231 | entry point function. | |
232 | ||
9d9ff5b1 JH |
233 | The context (void, scalar or list) for the return value(s) for C<-E<gt>join()> |
234 | is determined at the time of thread creation. | |
0f1612a7 | 235 | |
9d9ff5b1 | 236 | # Create thread in list context (implicit) |
0f1612a7 JH |
237 | my ($thr1) = threads->create(sub { |
238 | my @results = qw(a b c); | |
239 | return (@results); | |
9d9ff5b1 JH |
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 JH |
247 | # Retrieve list results from thread |
248 | my @res1 = $thr1->join(); | |
249 | ||
9d9ff5b1 | 250 | # Create thread in scalar context (implicit) |
0f1612a7 JH |
251 | my $thr2 = threads->create(sub { |
252 | my $result = 42; | |
253 | return ($result); | |
9d9ff5b1 | 254 | }); |
0f1612a7 JH |
255 | # Retrieve scalar result from thread |
256 | my $res2 = $thr2->join(); | |
257 | ||
9d9ff5b1 JH |
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 JH |
266 | If the program exits without all threads having either been joined or |
267 | detached, then a warning will be issued. | |
93512b4d | 268 | |
fcea4b7c JH |
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 $thr->detach() |
47ba8780 | 273 | |
fcea4b7c | 274 | Makes the thread unjoinable, and causes any eventual return value to be |
4dcb9e53 JH |
275 | discarded. When the program exits, any detached threads that are still |
276 | running are silently terminated. | |
277 | ||
278 | If the program exits without all threads having either been joined or | |
279 | detached, then a warning will be issued. | |
fcea4b7c JH |
280 | |
281 | Calling C<-E<gt>join()> or C<-E<gt>detach()> on an already detached thread | |
282 | will cause an error to be thrown. | |
0f1612a7 JH |
283 | |
284 | =item threads->detach() | |
285 | ||
286 | Class method that allows a thread to detach itself. | |
287 | ||
4dcb9e53 JH |
288 | =item threads->exit() |
289 | ||
290 | The usual method for terminating a thread is to | |
291 | L<return()|perlfunc/"return EXPR"> from the entry point function with the | |
292 | appropriate return value(s). | |
293 | ||
294 | If needed, a thread can be exited at any time by calling | |
295 | C<threads-E<gt>exit()>. This will cause the thread to return C<undef> in a | |
296 | scalar context, or the empty list in a list context. | |
297 | ||
298 | Calling C<die()> in a thread indicates an abnormal exit for the thread. Any | |
299 | C<$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 JH |
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 JH |
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 DM |
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 DM |
336 | code. |
337 | ||
f4cc38af | 338 | =item threads->list() |
678a9b6c | 339 | |
ead32952 JH |
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 JH |
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 JH |
361 | |
362 | if ($thr1 == $thr2) { | |
363 | print("Threads are the same\n"); | |
364 | } | |
fcea4b7c JH |
365 | # or |
366 | if ($thr1 != $thr2) { | |
367 | print("Threads differ\n"); | |
368 | } | |
0f1612a7 JH |
369 | |
370 | (Thread comparison is based on thread IDs.) | |
371 | ||
386c44e5 AB |
372 | =item async BLOCK; |
373 | ||
374 | C<async> creates a thread to execute the block immediately following | |
fcea4b7c JH |
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 JH |
379 | =item $thr->_handle() |
380 | ||
381 | This I<private> method returns the memory location of the internal thread | |
fcea4b7c JH |
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 JH |
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 AB |
396 | =back |
397 | ||
ead32952 JH |
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 JH |
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 JH |
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 JH |
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 JH |
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 JH |
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 JH |
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 JH |
570 | =head1 THREAD SIGNALLING |
571 | ||
9d9ff5b1 | 572 | When safe signals is in effect (the default behavior - see L</"Unsafe signals"> |
1152d448 JH |
573 | for more details), then signals may be sent and acted upon by individual |
574 | threads. | |
c0003851 JH |
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 JH |
596 | sub thr_func |
597 | { | |
598 | # Thread 'cancellation' signal handler | |
c608f8c0 | 599 | $SIG{'KILL'} = sub { threads->exit(); }; |
c0003851 JH |
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 JH |
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 JH |
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 | $sema->up(); | |
645 | ||
404aaa48 JH |
646 | CAVEAT: The thread signalling capability provided by this module does not |
647 | actually send signals via the OS. It I<emulates> signals at the Perl-level | |
648 | such that signal handlers are called in the appropriate thread. For example, | |
649 | sending C<$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 JH |
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 JH |
663 | =head1 WARNINGS |
664 | ||
665 | =over 4 | |
666 | ||
4dcb9e53 | 667 | =item Perl exited with active threads: |
e4f9f4fe | 668 | |
4dcb9e53 JH |
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 JH |
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 JH |
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 JH |
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 JH |
698 | If needed, thread warnings can be suppressed by using: |
699 | ||
700 | no warnings 'threads'; | |
701 | ||
702 | in the appropriate scope. | |
703 | ||
0f1612a7 JH |
704 | =head1 ERRORS |
705 | ||
706 | =over 4 | |
707 | ||
fcea4b7c | 708 | =item This Perl not built to support threads |
678a9b6c | 709 | |
0f1612a7 JH |
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 JH |
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 JH |
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 JH |
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 EM |
737 | =head1 BUGS |
738 | ||
47ba8780 AB |
739 | =over |
740 | ||
fcea4b7c | 741 | =item Parent-child threads |
678a9b6c | 742 | |
fcea4b7c JH |
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 JH |
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 JH |
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 JH |
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 JH |
776 | =item Returning closures from threads |
777 | ||
f2e0bb91 JH |
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 JH |
780 | (apparently harmless) warnings of leaked scalar, or all the way up to crashing |
781 | of the Perl interpreter. | |
0f1612a7 JH |
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 AB |
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 JH |
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 JH |
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 JH |
814 | Perl threads mailing list: |
815 | L<http://lists.cpan.org/showlist.cgi?name=iThreads> | |
47ba8780 | 816 | |
514612b7 JH |
817 | Stack size discussion: |
818 | L<http://www.perlmonks.org/?node_id=532956> | |
819 | ||
0f1612a7 | 820 | =head1 AUTHOR |
47ba8780 | 821 | |
0f1612a7 JH |
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 JH |
838 | Vipul Ved Prakash E<lt>mail AT vipul DOT netE<gt> - |
839 | Helping with debugging | |
47ba8780 | 840 | |
514612b7 JH |
841 | Dean Arnold E<lt>darnold AT presicient DOT comE<gt> - |
842 | Stack size API | |
843 | ||
47ba8780 | 844 | =cut |