Commit | Line | Data |
47ba8780 |
1 | package threads; |
2 | |
32419a4c |
3 | use 5.008; |
fcea4b7c |
4 | |
47ba8780 |
5 | use strict; |
6 | use warnings; |
73e09c8f |
7 | |
894eec8b |
8 | our $VERSION = '1.53'; |
fcea4b7c |
9 | my $XS_VERSION = $VERSION; |
10 | $VERSION = eval $VERSION; |
73e09c8f |
11 | |
73e09c8f |
12 | |
fcea4b7c |
13 | BEGIN { |
14 | # Verify this Perl supports threads |
15 | use Config; |
16 | if (! $Config{useithreads}) { |
17 | die("This Perl not built to support threads\n"); |
73e09c8f |
18 | } |
47ba8780 |
19 | |
fcea4b7c |
20 | # Complain if 'threads' is loaded after 'threads::shared' |
21 | if ($threads::shared::threads_shared) { |
22 | warn <<'_MSG_'; |
23 | Warning, threads::shared has already been loaded. To |
24 | enable shared variables, 'use threads' must be called |
25 | before threads::shared or any module that uses it. |
26 | _MSG_ |
27 | } |
dab065ea |
28 | } |
29 | |
fc04eb16 |
30 | |
45cd5be7 |
31 | # Declare that we have been loaded |
32 | $threads::threads = 1; |
33 | |
0f1612a7 |
34 | # Load the XS code |
35 | require XSLoader; |
fcea4b7c |
36 | XSLoader::load('threads', $XS_VERSION); |
47ba8780 |
37 | |
47ba8780 |
38 | |
0f1612a7 |
39 | ### Export ### |
47ba8780 |
40 | |
0f1612a7 |
41 | sub import |
42 | { |
43 | my $class = shift; # Not used |
44 | |
45 | # Exported subroutines |
46 | my @EXPORT = qw(async); |
47 | |
48 | # Handle args |
49 | while (my $sym = shift) { |
69a9b4b8 |
50 | if ($sym =~ /^stack/i) { |
514612b7 |
51 | threads->set_stack_size(shift); |
52 | |
69a9b4b8 |
53 | } elsif ($sym =~ /^exit/i) { |
54 | my $flag = shift; |
55 | $threads::thread_exit_only = $flag =~ /^thread/i; |
56 | |
3ab14376 |
57 | } elsif ($sym =~ /^str/i) { |
58 | import overload ('""' => \&tid); |
59 | |
de42e62a |
60 | } elsif ($sym =~ /(?:all|yield)/) { |
0f1612a7 |
61 | push(@EXPORT, qw(yield)); |
62 | |
63 | } else { |
de42e62a |
64 | require Carp; |
65 | Carp::croak("threads: Unknown import option: $sym"); |
0f1612a7 |
66 | } |
67 | } |
68 | |
69 | # Export subroutine names |
70 | my $caller = caller(); |
71 | foreach my $sym (@EXPORT) { |
72 | no strict 'refs'; |
73 | *{$caller.'::'.$sym} = \&{$sym}; |
74 | } |
514612b7 |
75 | |
76 | # Set stack size via environment variable |
77 | if (exists($ENV{'PERL5_ITHREADS_STACK_SIZE'})) { |
78 | threads->set_stack_size($ENV{'PERL5_ITHREADS_STACK_SIZE'}); |
79 | } |
0f1612a7 |
80 | } |
81 | |
82 | |
83 | ### Methods, etc. ### |
47ba8780 |
84 | |
69a9b4b8 |
85 | # Exit from a thread (only) |
4dcb9e53 |
86 | sub exit |
87 | { |
69a9b4b8 |
88 | my ($class, $status) = @_; |
89 | if (! defined($status)) { |
90 | $status = 0; |
91 | } |
92 | |
93 | # Class method only |
94 | if (ref($class)) { |
95 | require Carp; |
96 | Carp::croak("Usage: threads->exit(status)"); |
97 | } |
98 | |
99 | $class->set_thread_exit_only(1); |
100 | CORE::exit($status); |
4dcb9e53 |
101 | } |
102 | |
ead32952 |
103 | # 'Constant' args for threads->list() |
104 | sub threads::all { } |
105 | sub threads::running { 1 } |
106 | sub threads::joinable { 0 } |
107 | |
f4cc38af |
108 | # 'new' is an alias for 'create' |
109 | *new = \&create; |
68795e93 |
110 | |
fcea4b7c |
111 | # 'async' is a function alias for the 'threads->create()' method |
112 | sub async (&;@) |
113 | { |
114 | unshift(@_, 'threads'); |
115 | # Use "goto" trick to avoid pad problems from 5.8.1 (fixed in 5.8.2) |
116 | goto &create; |
117 | } |
118 | |
119 | # Thread object equality checking |
120 | use overload ( |
121 | '==' => \&equal, |
122 | '!=' => sub { ! equal(@_) }, |
123 | 'fallback' => 1 |
124 | ); |
125 | |
47ba8780 |
126 | 1; |
0f1612a7 |
127 | |
47ba8780 |
128 | __END__ |
129 | |
130 | =head1 NAME |
131 | |
0f1612a7 |
132 | threads - Perl interpreter-based threads |
133 | |
134 | =head1 VERSION |
135 | |
894eec8b |
136 | This document describes threads version 1.53 |
47ba8780 |
137 | |
138 | =head1 SYNOPSIS |
139 | |
3ab14376 |
140 | use threads ('yield', |
141 | 'stack_size' => 64*4096, |
142 | 'exit' => 'threads_only', |
143 | 'stringify'); |
47ba8780 |
144 | |
38875929 |
145 | sub start_thread { |
0f1612a7 |
146 | my @args = @_; |
9d9ff5b1 |
147 | print('Thread started: ', join(' ', @args), "\n"); |
38875929 |
148 | } |
fea7688c |
149 | my $thr = threads->create('start_thread', 'argument'); |
150 | $thr->join(); |
0f1612a7 |
151 | |
152 | threads->create(sub { print("I am a thread\n"); })->join(); |
47ba8780 |
153 | |
fea7688c |
154 | my $thr2 = async { foreach (@files) { ... } }; |
155 | $thr2->join(); |
0f1612a7 |
156 | |
9d9ff5b1 |
157 | # Invoke thread in list context (implicit) so it can return a list |
0f1612a7 |
158 | my ($thr) = threads->create(sub { return (qw/a b c/); }); |
9d9ff5b1 |
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 |
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 |
177 | yield(); |
178 | |
69a9b4b8 |
179 | # Lists of non-detached threads |
0f1612a7 |
180 | my @threads = threads->list(); |
fcea4b7c |
181 | my $thread_count = threads->list(); |
f9dff5f5 |
182 | |
ead32952 |
183 | my @running = threads->list(threads::running); |
184 | my @joinable = threads->list(threads::joinable); |
185 | |
69a9b4b8 |
186 | # Test thread objects |
0f1612a7 |
187 | if ($thr1 == $thr2) { |
188 | ... |
189 | } |
678a9b6c |
190 | |
69a9b4b8 |
191 | # Manage thread stack size |
514612b7 |
192 | $stack_size = threads->get_stack_size(); |
193 | $old_size = threads->set_stack_size(32*4096); |
194 | |
9d9ff5b1 |
195 | # Create a thread with a specific context and stack size |
196 | my $thr = threads->create({ 'context' => 'list', |
69a9b4b8 |
197 | 'stack_size' => 32*4096, |
198 | 'exit' => 'thread_only' }, |
9d9ff5b1 |
199 | \&foo); |
ead32952 |
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 |
213 | $thr->kill('SIGUSR1'); |
214 | |
69a9b4b8 |
215 | # Exit a thread |
4dcb9e53 |
216 | threads->exit(); |
217 | |
47ba8780 |
218 | =head1 DESCRIPTION |
219 | |
fc04eb16 |
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 |
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 |
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 |
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 |
239 | |
240 | =over |
241 | |
0f1612a7 |
242 | =item $thr = threads->create(FUNCTION, ARGS) |
47ba8780 |
243 | |
0f1612a7 |
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 |
248 | I<FUNCTION> may either be the name of a function, an anonymous subroutine, or |
249 | a code ref. |
47ba8780 |
250 | |
0f1612a7 |
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 |
257 | The C<-E<gt>new()> method is an alias for C<-E<gt>create()>. |
258 | |
259 | =item $thr->join() |
260 | |
261 | This will wait for the corresponding thread to complete its execution. When |
262 | the thread finishes, C<-E<gt>join()> will return the return value(s) of the |
263 | entry point function. |
264 | |
9d9ff5b1 |
265 | The context (void, scalar or list) for the return value(s) for C<-E<gt>join()> |
266 | is determined at the time of thread creation. |
0f1612a7 |
267 | |
9d9ff5b1 |
268 | # Create thread in list context (implicit) |
0f1612a7 |
269 | my ($thr1) = threads->create(sub { |
270 | my @results = qw(a b c); |
271 | return (@results); |
9d9ff5b1 |
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 |
279 | # Retrieve list results from thread |
280 | my @res1 = $thr1->join(); |
281 | |
9d9ff5b1 |
282 | # Create thread in scalar context (implicit) |
0f1612a7 |
283 | my $thr2 = threads->create(sub { |
284 | my $result = 42; |
285 | return ($result); |
9d9ff5b1 |
286 | }); |
0f1612a7 |
287 | # Retrieve scalar result from thread |
288 | my $res2 = $thr2->join(); |
289 | |
9d9ff5b1 |
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 |
298 | If the program exits without all threads having either been joined or |
299 | detached, then a warning will be issued. |
93512b4d |
300 | |
fcea4b7c |
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 |
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 |
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 |
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 |
324 | =item $thr->tid() |
325 | |
326 | Returns the ID of the thread. Thread IDs are unique integers with the main |
327 | thread in a program being 0, and incrementing by 1 for every thread created. |
47ba8780 |
328 | |
0f1612a7 |
329 | =item threads->tid() |
38875929 |
330 | |
0f1612a7 |
331 | Class method that allows a thread to obtain its own ID. |
47ba8780 |
332 | |
3ab14376 |
333 | =item "$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 |
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 |
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 |
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 |
358 | code. |
359 | |
f4cc38af |
360 | =item threads->list() |
678a9b6c |
361 | |
ead32952 |
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 |
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 |
383 | |
384 | if ($thr1 == $thr2) { |
385 | print("Threads are the same\n"); |
386 | } |
fcea4b7c |
387 | # or |
388 | if ($thr1 != $thr2) { |
389 | print("Threads differ\n"); |
390 | } |
0f1612a7 |
391 | |
392 | (Thread comparison is based on thread IDs.) |
393 | |
386c44e5 |
394 | =item async BLOCK; |
395 | |
396 | C<async> creates a thread to execute the block immediately following |
fcea4b7c |
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 |
401 | =item $thr->_handle() |
402 | |
403 | This I<private> method returns the memory location of the internal thread |
fcea4b7c |
404 | structure associated with a threads object. For Win32, this is a pointer to |
405 | the C<HANDLE> value returned by C<CreateThread> (i.e., C<HANDLE *>); for other |
406 | platforms, it is a pointer to the C<pthread_t> structure used in the |
404aaa48 |
407 | C<pthread_create> call (i.e., C<pthread_t *>). |
f4cc38af |
408 | |
409 | This method is of no use for general Perl threads programming. Its intent is |
410 | to provide other (XS-based) thread modules with the capability to access, and |
411 | possibly manipulate, the underlying thread structure associated with a Perl |
412 | thread. |
413 | |
414 | =item threads->_handle() |
415 | |
416 | Class method that allows a thread to obtain its own I<handle>. |
417 | |
47ba8780 |
418 | =back |
419 | |
69a9b4b8 |
420 | =head1 EXITING A THREAD |
421 | |
422 | The usual method for terminating a thread is to |
423 | L<return()|perlfunc/"return EXPR"> from the entry point function with the |
424 | appropriate return value(s). |
425 | |
426 | =over |
427 | |
428 | =item threads->exit() |
429 | |
430 | If needed, a thread can be exited at any time by calling |
431 | C<threads-E<gt>exit()>. This will cause the thread to return C<undef> in a |
432 | scalar context, or the empty list in a list context. |
433 | |
434 | When called from the I<main> thread, this behaves the same as C<exit(0)>. |
435 | |
436 | =item threads->exit(status) |
437 | |
438 | When called from a thread, this behaves like C<threads-E<gt>exit()> (i.e., the |
439 | exit status code is ignored). |
440 | |
441 | When called from the I<main> thread, this behaves the same as C<exit(status)>. |
442 | |
443 | =item die() |
444 | |
445 | Calling C<die()> in a thread indicates an abnormal exit for the thread. Any |
446 | C<$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 |
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 |
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 |
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 |
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 |
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 |
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 |
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 |
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 |
669 | =head1 THREAD SIGNALLING |
670 | |
9d9ff5b1 |
671 | When safe signals is in effect (the default behavior - see L</"Unsafe signals"> |
1152d448 |
672 | for more details), then signals may be sent and acted upon by individual |
673 | threads. |
c0003851 |
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 |
695 | sub thr_func |
696 | { |
697 | # Thread 'cancellation' signal handler |
c608f8c0 |
698 | $SIG{'KILL'} = sub { threads->exit(); }; |
c0003851 |
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 |
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 |
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 | $sema->up(); |
744 | |
404aaa48 |
745 | CAVEAT: The thread signalling capability provided by this module does not |
746 | actually send signals via the OS. It I<emulates> signals at the Perl-level |
747 | such that signal handlers are called in the appropriate thread. For example, |
748 | sending C<$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 |
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 |
762 | Sending a signal to a terminated thread is ignored. |
763 | |
e4f9f4fe |
764 | =head1 WARNINGS |
765 | |
766 | =over 4 |
767 | |
4dcb9e53 |
768 | =item Perl exited with active threads: |
e4f9f4fe |
769 | |
4dcb9e53 |
770 | If the program exits without all threads having either been joined or |
771 | detached, then this warning will be issued. |
772 | |
69a9b4b8 |
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 |
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 |
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 |
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 |
799 | If needed, thread warnings can be suppressed by using: |
800 | |
801 | no warnings 'threads'; |
802 | |
803 | in the appropriate scope. |
804 | |
0f1612a7 |
805 | =head1 ERRORS |
806 | |
807 | =over 4 |
808 | |
fcea4b7c |
809 | =item This Perl not built to support threads |
678a9b6c |
810 | |
0f1612a7 |
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 |
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 |
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 |
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 |
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 |
871 | =head1 BUGS |
872 | |
5c6ff896 |
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 |
877 | =over |
878 | |
fcea4b7c |
879 | =item Parent-child threads |
678a9b6c |
880 | |
fcea4b7c |
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 |
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 |
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 |
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 |
914 | =item Returning closures from threads |
915 | |
f2e0bb91 |
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 |
918 | (apparently harmless) warnings of leaked scalar, or all the way up to crashing |
919 | of the Perl interpreter. |
0f1612a7 |
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 |
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 |
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 |
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 |
948 | Perl threads mailing list: |
949 | L<http://lists.cpan.org/showlist.cgi?name=iThreads> |
47ba8780 |
950 | |
514612b7 |
951 | Stack size discussion: |
952 | L<http://www.perlmonks.org/?node_id=532956> |
953 | |
0f1612a7 |
954 | =head1 AUTHOR |
47ba8780 |
955 | |
0f1612a7 |
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 |
972 | Vipul Ved Prakash E<lt>mail AT vipul DOT netE<gt> - |
973 | Helping with debugging |
47ba8780 |
974 | |
514612b7 |
975 | Dean Arnold E<lt>darnold AT presicient DOT comE<gt> - |
976 | Stack size API |
977 | |
47ba8780 |
978 | =cut |