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 | |
4dcb9e53 | 8 | our $VERSION = '1.33'; |
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 | ||
f4cc38af JH |
83 | # 'new' is an alias for 'create' |
84 | *new = \&create; | |
68795e93 | 85 | |
fcea4b7c JH |
86 | # 'async' is a function alias for the 'threads->create()' method |
87 | sub async (&;@) | |
88 | { | |
89 | unshift(@_, 'threads'); | |
90 | # Use "goto" trick to avoid pad problems from 5.8.1 (fixed in 5.8.2) | |
91 | goto &create; | |
92 | } | |
93 | ||
94 | # Thread object equality checking | |
95 | use overload ( | |
96 | '==' => \&equal, | |
97 | '!=' => sub { ! equal(@_) }, | |
98 | 'fallback' => 1 | |
99 | ); | |
100 | ||
47ba8780 | 101 | 1; |
0f1612a7 | 102 | |
47ba8780 AB |
103 | __END__ |
104 | ||
105 | =head1 NAME | |
106 | ||
0f1612a7 JH |
107 | threads - Perl interpreter-based threads |
108 | ||
109 | =head1 VERSION | |
110 | ||
4dcb9e53 | 111 | This document describes threads version 1.33 |
47ba8780 AB |
112 | |
113 | =head1 SYNOPSIS | |
114 | ||
514612b7 | 115 | use threads ('yield', 'stack_size' => 64*4096); |
47ba8780 | 116 | |
38875929 | 117 | sub start_thread { |
0f1612a7 | 118 | my @args = @_; |
9d9ff5b1 | 119 | print('Thread started: ', join(' ', @args), "\n"); |
38875929 | 120 | } |
0f1612a7 JH |
121 | my $thread = threads->create('start_thread', 'argument'); |
122 | $thread->join(); | |
123 | ||
124 | threads->create(sub { print("I am a thread\n"); })->join(); | |
47ba8780 | 125 | |
38875929 | 126 | my $thread3 = async { foreach (@files) { ... } }; |
0f1612a7 JH |
127 | $thread3->join(); |
128 | ||
9d9ff5b1 | 129 | # Invoke thread in list context (implicit) so it can return a list |
0f1612a7 | 130 | my ($thr) = threads->create(sub { return (qw/a b c/); }); |
9d9ff5b1 JH |
131 | # or specify list context explicitly |
132 | my $thr = threads->create({'context' => 'list'}, | |
133 | sub { return (qw/a b c/); }); | |
0f1612a7 | 134 | my @results = $thr->join(); |
47ba8780 | 135 | |
38875929 | 136 | $thread->detach(); |
47ba8780 | 137 | |
38875929 | 138 | $thread = threads->self(); |
0f1612a7 | 139 | $thread = threads->object($tid); |
11c51ed3 | 140 | |
0f1612a7 JH |
141 | $tid = threads->tid(); |
142 | $tid = threads->self->tid(); | |
143 | $tid = $thread->tid(); | |
47ba8780 | 144 | |
38875929 | 145 | threads->yield(); |
0f1612a7 JH |
146 | yield(); |
147 | ||
148 | my @threads = threads->list(); | |
fcea4b7c | 149 | my $thread_count = threads->list(); |
f9dff5f5 | 150 | |
0f1612a7 JH |
151 | if ($thr1 == $thr2) { |
152 | ... | |
153 | } | |
678a9b6c | 154 | |
514612b7 JH |
155 | $stack_size = threads->get_stack_size(); |
156 | $old_size = threads->set_stack_size(32*4096); | |
157 | ||
9d9ff5b1 JH |
158 | # Create a thread with a specific context and stack size |
159 | my $thr = threads->create({ 'context' => 'list', | |
160 | 'stack_size' => 32*4096 }, | |
161 | \&foo); | |
162 | my @results = $thr->join(); | |
163 | ||
c0003851 JH |
164 | $thr->kill('SIGUSR1'); |
165 | ||
4dcb9e53 JH |
166 | threads->exit(); |
167 | ||
47ba8780 AB |
168 | =head1 DESCRIPTION |
169 | ||
fc04eb16 JH |
170 | Perl 5.6 introduced something called interpreter threads. Interpreter threads |
171 | are different from I<5005threads> (the thread model of Perl 5.005) by creating | |
172 | a new Perl interpreter per thread, and not sharing any data or state between | |
173 | threads by default. | |
11c51ed3 | 174 | |
fc04eb16 JH |
175 | Prior to Perl 5.8, this has only been available to people embedding Perl, and |
176 | for emulating fork() on Windows. | |
11c51ed3 | 177 | |
fc04eb16 JH |
178 | The I<threads> API is loosely based on the old Thread.pm API. It is very |
179 | important to note that variables are not shared between threads, all variables | |
180 | are by default thread local. To use shared variables one must use | |
181 | L<threads::shared>. | |
11c51ed3 | 182 | |
fc04eb16 JH |
183 | It is also important to note that you must enable threads by doing C<use |
184 | threads> as early as possible in the script itself, and that it is not | |
185 | possible to enable threading inside an C<eval "">, C<do>, C<require>, or | |
186 | C<use>. In particular, if you are intending to share variables with | |
187 | L<threads::shared>, you must C<use threads> before you C<use threads::shared>. | |
188 | (C<threads> will emit a warning if you do it the other way around.) | |
47ba8780 AB |
189 | |
190 | =over | |
191 | ||
0f1612a7 | 192 | =item $thr = threads->create(FUNCTION, ARGS) |
47ba8780 | 193 | |
0f1612a7 JH |
194 | This will create a new thread that will begin execution with the specified |
195 | entry point function, and give it the I<ARGS> list as parameters. It will | |
196 | return the corresponding threads object, or C<undef> if thread creation failed. | |
47ba8780 | 197 | |
0f1612a7 JH |
198 | I<FUNCTION> may either be the name of a function, an anonymous subroutine, or |
199 | a code ref. | |
47ba8780 | 200 | |
0f1612a7 JH |
201 | my $thr = threads->create('func_name', ...); |
202 | # or | |
203 | my $thr = threads->create(sub { ... }, ...); | |
204 | # or | |
205 | my $thr = threads->create(\&func, ...); | |
93512b4d | 206 | |
0f1612a7 JH |
207 | The C<-E<gt>new()> method is an alias for C<-E<gt>create()>. |
208 | ||
209 | =item $thr->join() | |
210 | ||
211 | This will wait for the corresponding thread to complete its execution. When | |
212 | the thread finishes, C<-E<gt>join()> will return the return value(s) of the | |
213 | entry point function. | |
214 | ||
9d9ff5b1 JH |
215 | The context (void, scalar or list) for the return value(s) for C<-E<gt>join()> |
216 | is determined at the time of thread creation. | |
0f1612a7 | 217 | |
9d9ff5b1 | 218 | # Create thread in list context (implicit) |
0f1612a7 JH |
219 | my ($thr1) = threads->create(sub { |
220 | my @results = qw(a b c); | |
221 | return (@results); | |
9d9ff5b1 JH |
222 | }); |
223 | # or (explicit) | |
224 | my $thr1 = threads->create({'context' => 'list'}, | |
225 | sub { | |
226 | my @results = qw(a b c); | |
227 | return (@results); | |
228 | }); | |
0f1612a7 JH |
229 | # Retrieve list results from thread |
230 | my @res1 = $thr1->join(); | |
231 | ||
9d9ff5b1 | 232 | # Create thread in scalar context (implicit) |
0f1612a7 JH |
233 | my $thr2 = threads->create(sub { |
234 | my $result = 42; | |
235 | return ($result); | |
9d9ff5b1 | 236 | }); |
0f1612a7 JH |
237 | # Retrieve scalar result from thread |
238 | my $res2 = $thr2->join(); | |
239 | ||
9d9ff5b1 JH |
240 | # Create a thread in void context (explicit) |
241 | my $thr3 = threads->create({'void' => 1}, | |
242 | sub { print("Hello, world\n"); }); | |
243 | # Join the thread in void context (i.e., no return value) | |
244 | $thr3->join(); | |
245 | ||
246 | See L</"THREAD CONTEXT"> for more details. | |
247 | ||
4dcb9e53 JH |
248 | If the program exits without all threads having either been joined or |
249 | detached, then a warning will be issued. | |
93512b4d | 250 | |
fcea4b7c JH |
251 | Calling C<-E<gt>join()> or C<-E<gt>detach()> on an already joined thread will |
252 | cause an error to be thrown. | |
47ba8780 | 253 | |
fcea4b7c | 254 | =item $thr->detach() |
47ba8780 | 255 | |
fcea4b7c | 256 | Makes the thread unjoinable, and causes any eventual return value to be |
4dcb9e53 JH |
257 | discarded. When the program exits, any detached threads that are still |
258 | running are silently terminated. | |
259 | ||
260 | If the program exits without all threads having either been joined or | |
261 | detached, then a warning will be issued. | |
fcea4b7c JH |
262 | |
263 | Calling C<-E<gt>join()> or C<-E<gt>detach()> on an already detached thread | |
264 | will cause an error to be thrown. | |
0f1612a7 JH |
265 | |
266 | =item threads->detach() | |
267 | ||
268 | Class method that allows a thread to detach itself. | |
269 | ||
4dcb9e53 JH |
270 | =item threads->exit() |
271 | ||
272 | The usual method for terminating a thread is to | |
273 | L<return()|perlfunc/"return EXPR"> from the entry point function with the | |
274 | appropriate return value(s). | |
275 | ||
276 | If needed, a thread can be exited at any time by calling | |
277 | C<threads-E<gt>exit()>. This will cause the thread to return C<undef> in a | |
278 | scalar context, or the empty list in a list context. | |
279 | ||
280 | Calling C<die()> in a thread indicates an abnormal exit for the thread. Any | |
281 | C<$SIG{__DIE__}> handler in the thread will be called first, and then the | |
282 | thread will exit with a warning message that will contain any arguments passed | |
283 | in the C<die()> call. | |
284 | ||
285 | Calling C<exit()> in a thread is discouraged, but is equivalent to calling | |
286 | C<threads-E<gt>exit()>. | |
287 | ||
288 | If the desired affect is to truly terminate the application from a thread, | |
289 | then use L<POSIX::_exit()|POSIX/"_exit">, if available. | |
290 | ||
fcea4b7c | 291 | =item threads->self() |
47ba8780 | 292 | |
fcea4b7c | 293 | Class method that allows a thread to obtain its own I<threads> object. |
47ba8780 | 294 | |
0f1612a7 JH |
295 | =item $thr->tid() |
296 | ||
297 | Returns the ID of the thread. Thread IDs are unique integers with the main | |
298 | thread in a program being 0, and incrementing by 1 for every thread created. | |
47ba8780 | 299 | |
0f1612a7 | 300 | =item threads->tid() |
38875929 | 301 | |
0f1612a7 | 302 | Class method that allows a thread to obtain its own ID. |
47ba8780 | 303 | |
0f1612a7 | 304 | =item threads->object($tid) |
8c9849ff | 305 | |
0f1612a7 JH |
306 | This will return the I<threads> object for the I<active> thread associated |
307 | with the specified thread ID. Returns C<undef> if there is no thread | |
308 | associated with the TID, if the thread is joined or detached, if no TID is | |
309 | specified or if the specified TID is undef. | |
8c9849ff | 310 | |
fcea4b7c | 311 | =item threads->yield() |
f9dff5f5 | 312 | |
38875929 DM |
313 | This is a suggestion to the OS to let this thread yield CPU time to other |
314 | threads. What actually happens is highly dependent upon the underlying | |
315 | thread implementation. | |
f9dff5f5 | 316 | |
fcea4b7c | 317 | You may do C<use threads qw(yield)>, and then just use C<yield()> in your |
70f2e746 DM |
318 | code. |
319 | ||
f4cc38af | 320 | =item threads->list() |
678a9b6c | 321 | |
f4cc38af JH |
322 | In a list context, returns a list of all non-joined, non-detached I<threads> |
323 | objects. In a scalar context, returns a count of the same. | |
678a9b6c | 324 | |
0f1612a7 JH |
325 | =item $thr1->equal($thr2) |
326 | ||
327 | Tests if two threads objects are the same thread or not. This is overloaded | |
fcea4b7c | 328 | to the more natural forms: |
0f1612a7 JH |
329 | |
330 | if ($thr1 == $thr2) { | |
331 | print("Threads are the same\n"); | |
332 | } | |
fcea4b7c JH |
333 | # or |
334 | if ($thr1 != $thr2) { | |
335 | print("Threads differ\n"); | |
336 | } | |
0f1612a7 JH |
337 | |
338 | (Thread comparison is based on thread IDs.) | |
339 | ||
386c44e5 AB |
340 | =item async BLOCK; |
341 | ||
342 | C<async> creates a thread to execute the block immediately following | |
fcea4b7c JH |
343 | it. This block is treated as an anonymous subroutine, and so must have a |
344 | semi-colon after the closing brace. Like C<threads->create()>, C<async> | |
345 | returns a I<threads> object. | |
386c44e5 | 346 | |
f4cc38af JH |
347 | =item $thr->_handle() |
348 | ||
349 | This I<private> method returns the memory location of the internal thread | |
fcea4b7c JH |
350 | structure associated with a threads object. For Win32, this is a pointer to |
351 | the C<HANDLE> value returned by C<CreateThread> (i.e., C<HANDLE *>); for other | |
352 | platforms, it is a pointer to the C<pthread_t> structure used in the | |
404aaa48 | 353 | C<pthread_create> call (i.e., C<pthread_t *>). |
f4cc38af JH |
354 | |
355 | This method is of no use for general Perl threads programming. Its intent is | |
356 | to provide other (XS-based) thread modules with the capability to access, and | |
357 | possibly manipulate, the underlying thread structure associated with a Perl | |
358 | thread. | |
359 | ||
360 | =item threads->_handle() | |
361 | ||
362 | Class method that allows a thread to obtain its own I<handle>. | |
363 | ||
47ba8780 AB |
364 | =back |
365 | ||
9d9ff5b1 JH |
366 | =head1 THREAD CONTEXT |
367 | ||
368 | As with subroutines, the type of value returned from a thread's entry point | |
369 | function may be determined by the thread's I<context>: list, scalar or void. | |
370 | The thread's context is determined at thread creation. This is necessary so | |
371 | that the context is available to the entry point function via | |
206f4df7 | 372 | L<wantarray()|perlfunc/"wantarray">. The thread may then specify a value of |
9d9ff5b1 JH |
373 | the appropriate type to be returned from C<-E<gt>join()>. |
374 | ||
375 | =head2 Explicit context | |
376 | ||
377 | Because thread creation and thread joining may occur in different contexts, it | |
378 | may be desirable to state the context explicitly to the thread's entry point | |
379 | function. This may be done by calling C<-E<gt>create()> with a parameter hash | |
380 | as the first argument: | |
381 | ||
382 | my $thr = threads->create({'context' => 'list'}, \&foo); | |
383 | ... | |
384 | my @results = $thr->join(); | |
385 | ||
386 | In the above, the threads object is returned to the parent thread in scalar | |
387 | context, and the thread's entry point function C<foo> will be called in list | |
388 | context such that the parent thread can receive a list from the C<-E<gt>join()> | |
389 | call. Similarly, if you need the threads object, but your thread will not be | |
390 | returning a value (i.e., I<void> context), you would do the following: | |
391 | ||
392 | my $thr = threads->create({'context' => 'void'}, \&foo); | |
393 | ... | |
394 | $thr->join(); | |
395 | ||
396 | The context type may also be used as the I<key> in the parameter hash followed | |
397 | by a I<true> value: | |
398 | ||
399 | threads->create({'scalar' => 1}, \&foo); | |
400 | ... | |
401 | my ($thr) = threads->list(); | |
402 | my $result = $thr->join(); | |
403 | ||
404 | =head2 Implicit context | |
405 | ||
406 | If not explicitly stated, the thread's context is implied from the context | |
407 | of the C<-E<gt>create()> call: | |
408 | ||
409 | # Create thread in list context | |
410 | my ($thr) = threads->create(...); | |
411 | ||
412 | # Create thread in scalar context | |
413 | my $thr = threads->create(...); | |
414 | ||
415 | # Create thread in void context | |
416 | threads->create(...); | |
417 | ||
514612b7 JH |
418 | =head1 THREAD STACK SIZE |
419 | ||
420 | The default per-thread stack size for different platforms varies | |
421 | significantly, and is almost always far more than is needed for most | |
422 | applications. On Win32, Perl's makefile explicitly sets the default stack to | |
423 | 16 MB; on most other platforms, the system default is used, which again may be | |
424 | much larger than is needed. | |
425 | ||
426 | By tuning the stack size to more accurately reflect your application's needs, | |
427 | you may significantly reduce your application's memory usage, and increase the | |
428 | number of simultaneously running threads. | |
429 | ||
430 | N.B., on Windows, Address space allocation granularity is 64 KB, therefore, | |
431 | setting the stack smaller than that on Win32 Perl will not save any more | |
432 | memory. | |
433 | ||
434 | =over | |
435 | ||
436 | =item threads->get_stack_size(); | |
437 | ||
438 | Returns the current default per-thread stack size. The default is zero, which | |
439 | means the system default stack size is currently in use. | |
440 | ||
441 | =item $size = $thr->get_stack_size(); | |
442 | ||
443 | Returns the stack size for a particular thread. A return value of zero | |
444 | indicates the system default stack size was used for the thread. | |
445 | ||
446 | =item $old_size = threads->set_stack_size($new_size); | |
447 | ||
448 | Sets a new default per-thread stack size, and returns the previous setting. | |
449 | ||
450 | Some platforms have a minimum thread stack size. Trying to set the stack size | |
451 | below this value will result in a warning, and the minimum stack size will be | |
452 | used. | |
453 | ||
454 | Some Linux platforms have a maximum stack size. Setting too large of a stack | |
455 | size will cause thread creation to fail. | |
456 | ||
457 | If needed, C<$new_size> will be rounded up to the next multiple of the memory | |
458 | page size (usually 4096 or 8192). | |
459 | ||
460 | Threads created after the stack size is set will then either call | |
461 | C<pthread_attr_setstacksize()> I<(for pthreads platforms)>, or supply the | |
462 | stack size to C<CreateThread()> I<(for Win32 Perl)>. | |
463 | ||
464 | (Obviously, this call does not affect any currently extant threads.) | |
465 | ||
466 | =item use threads ('stack_size' => VALUE); | |
467 | ||
468 | This sets the default per-thread stack size at the start of the application. | |
469 | ||
470 | =item $ENV{'PERL5_ITHREADS_STACK_SIZE'} | |
471 | ||
472 | The default per-thread stack size may be set at the start of the application | |
473 | through the use of the environment variable C<PERL5_ITHREADS_STACK_SIZE>: | |
474 | ||
475 | PERL5_ITHREADS_STACK_SIZE=1048576 | |
476 | export PERL5_ITHREADS_STACK_SIZE | |
477 | perl -e'use threads; print(threads->get_stack_size(), "\n")' | |
478 | ||
479 | This value overrides any C<stack_size> parameter given to C<use threads>. Its | |
480 | primary purpose is to permit setting the per-thread stack size for legacy | |
481 | threaded applications. | |
482 | ||
483 | =item threads->create({'stack_size' => VALUE}, FUNCTION, ARGS) | |
484 | ||
9d9ff5b1 JH |
485 | The stack size an individual threads may also be specified. This may be done |
486 | by calling C<-E<gt>create()> with a parameter hash as the first argument: | |
487 | ||
488 | my $thr = threads->create({'stack_size' => 32*4096}, \&foo, @args); | |
514612b7 JH |
489 | |
490 | =item $thr2 = $thr1->create(FUNCTION, ARGS) | |
491 | ||
492 | This creates a new thread (C<$thr2>) that inherits the stack size from an | |
493 | existing thread (C<$thr1>). This is shorthand for the following: | |
494 | ||
495 | my $stack_size = $thr1->get_stack_size(); | |
496 | my $thr2 = threads->create({'stack_size' => $stack_size}, FUNCTION, ARGS); | |
497 | ||
498 | =back | |
499 | ||
c0003851 JH |
500 | =head1 THREAD SIGNALLING |
501 | ||
9d9ff5b1 | 502 | When safe signals is in effect (the default behavior - see L</"Unsafe signals"> |
1152d448 JH |
503 | for more details), then signals may be sent and acted upon by individual |
504 | threads. | |
c0003851 JH |
505 | |
506 | =over 4 | |
507 | ||
508 | =item $thr->kill('SIG...'); | |
509 | ||
510 | Sends the specified signal to the thread. Signal names and (positive) signal | |
511 | numbers are the same as those supported by | |
512 | L<kill()|perlfunc/"kill SIGNAL, LIST">. For example, 'SIGTERM', 'TERM' and | |
513 | (depending on the OS) 15 are all valid arguments to C<-E<gt>kill()>. | |
514 | ||
515 | Returns the thread object to allow for method chaining: | |
516 | ||
517 | $thr->kill('SIG...')->join(); | |
518 | ||
519 | =back | |
520 | ||
521 | Signal handlers need to be set up in the threads for the signals they are | |
522 | expected to act upon. Here's an example for I<cancelling> a thread: | |
523 | ||
524 | use threads; | |
525 | ||
526 | # Suppress warning message when thread is 'killed' | |
527 | no warnings 'threads'; | |
528 | ||
529 | sub thr_func | |
530 | { | |
531 | # Thread 'cancellation' signal handler | |
532 | $SIG{'KILL'} = sub { die("Thread killed\n"); }; | |
533 | ||
534 | ... | |
535 | } | |
536 | ||
537 | # Create a thread | |
538 | my $thr = threads->create('thr_func'); | |
539 | ||
540 | ... | |
541 | ||
542 | # Signal the thread to terminate, and then detach | |
543 | # it so that it will get cleaned up automatically | |
544 | $thr->kill('KILL')->detach(); | |
545 | ||
404aaa48 JH |
546 | Here's another simplistic example that illustrates the use of thread |
547 | signalling in conjunction with a semaphore to provide rudimentary I<suspend> | |
548 | and I<resume> capabilities: | |
c0003851 JH |
549 | |
550 | use threads; | |
551 | use Thread::Semaphore; | |
552 | ||
553 | sub thr_func | |
554 | { | |
555 | my $sema = shift; | |
556 | ||
557 | # Thread 'suspend/resume' signal handler | |
558 | $SIG{'STOP'} = sub { | |
559 | $sema->down(); # Thread suspended | |
560 | $sema->up(); # Thread resumes | |
561 | }; | |
562 | ||
563 | ... | |
564 | } | |
565 | ||
566 | # Create a semaphore and send it to a thread | |
567 | my $sema = Thread::Semaphore->new(); | |
568 | my $thr = threads->create('thr_func', $sema); | |
569 | ||
570 | # Suspend the thread | |
571 | $sema->down(); | |
572 | $thr->kill('STOP'); | |
573 | ||
574 | ... | |
575 | ||
576 | # Allow the thread to continue | |
577 | $sema->up(); | |
578 | ||
404aaa48 JH |
579 | CAVEAT: The thread signalling capability provided by this module does not |
580 | actually send signals via the OS. It I<emulates> signals at the Perl-level | |
581 | such that signal handlers are called in the appropriate thread. For example, | |
582 | sending C<$thr-E<gt>kill('STOP')> does not actually suspend a thread (or the | |
583 | whole process), but does cause a C<$SIG{'STOP'}> handler to be called in that | |
584 | thread (as illustrated above). | |
585 | ||
586 | As such, signals that would normally not be appropriate to use in the | |
587 | C<kill()> command (e.g., C<kill('KILL', $$)>) are okay to use with the | |
588 | C<-E<gt>kill()> method (again, as illustrated above). | |
589 | ||
590 | Correspondingly, sending a signal to a thread does not disrupt the operation | |
591 | the thread is currently working on: The signal will be acted upon after the | |
c0003851 JH |
592 | current operation has completed. For instance, if the thread is I<stuck> on |
593 | an I/O call, sending it a signal will not cause the I/O call to be interrupted | |
594 | such that the signal is acted up immediately. | |
595 | ||
e4f9f4fe JH |
596 | =head1 WARNINGS |
597 | ||
598 | =over 4 | |
599 | ||
4dcb9e53 | 600 | =item Perl exited with active threads: |
e4f9f4fe | 601 | |
4dcb9e53 JH |
602 | If the program exits without all threads having either been joined or |
603 | detached, then this warning will be issued. | |
604 | ||
605 | NOTE: This warning cannot be suppressed using C<no warnings 'threads';> as | |
606 | suggested below. | |
e4f9f4fe | 607 | |
c0003851 JH |
608 | =item Thread creation failed: pthread_create returned # |
609 | ||
610 | See the appropriate I<man> page for C<pthread_create> to determine the actual | |
611 | cause for the failure. | |
612 | ||
613 | =item Thread # terminated abnormally: ... | |
614 | ||
615 | A thread terminated in some manner other than just returning from its entry | |
4dcb9e53 | 616 | point function. For example, the thread may have terminated using C<die>. |
c0003851 | 617 | |
514612b7 JH |
618 | =item Using minimum thread stack size of # |
619 | ||
620 | Some platforms have a minimum thread stack size. Trying to set the stack size | |
621 | below this value will result in the above warning, and the stack size will be | |
622 | set to the minimum. | |
623 | ||
c0003851 JH |
624 | =item Thread creation failed: pthread_attr_setstacksize(I<SIZE>) returned 22 |
625 | ||
626 | The specified I<SIZE> exceeds the system's maximum stack size. Use a smaller | |
627 | value for the stack size. | |
628 | ||
e4f9f4fe | 629 | =back |
47ba8780 | 630 | |
c0003851 JH |
631 | If needed, thread warnings can be suppressed by using: |
632 | ||
633 | no warnings 'threads'; | |
634 | ||
635 | in the appropriate scope. | |
636 | ||
0f1612a7 JH |
637 | =head1 ERRORS |
638 | ||
639 | =over 4 | |
640 | ||
fcea4b7c | 641 | =item This Perl not built to support threads |
678a9b6c | 642 | |
0f1612a7 JH |
643 | The particular copy of Perl that you're trying to use was not built using the |
644 | C<useithreads> configuration option. | |
678a9b6c | 645 | |
0f1612a7 JH |
646 | Having threads support requires all of Perl and all of the XS modules in the |
647 | Perl installation to be rebuilt; it is not just a question of adding the | |
648 | L<threads> module (i.e., threaded and non-threaded Perls are binary | |
649 | incompatible.) | |
650 | ||
514612b7 JH |
651 | =item Cannot change stack size of an existing thread |
652 | ||
653 | The stack size of currently extant threads cannot be changed, therefore, the | |
654 | following results in the above error: | |
655 | ||
656 | $thr->set_stack_size($size); | |
657 | ||
4dcb9e53 | 658 | =item Cannot signal threads without safe signals |
514612b7 | 659 | |
1152d448 | 660 | Safe signals must be in effect to use the C<-E<gt>kill()> signalling method. |
9d9ff5b1 | 661 | See L</"Unsafe signals"> for more details. |
c0003851 JH |
662 | |
663 | =item Unrecognized signal name: ... | |
664 | ||
665 | The particular copy of Perl that you're trying to use does not support the | |
666 | specified signal being used in a C<-E<gt>kill()> call. | |
514612b7 | 667 | |
0f1612a7 | 668 | =back |
47ba8780 | 669 | |
ab80e3f2 EM |
670 | =head1 BUGS |
671 | ||
47ba8780 AB |
672 | =over |
673 | ||
fcea4b7c | 674 | =item Parent-child threads |
678a9b6c | 675 | |
fcea4b7c JH |
676 | On some platforms, it might not be possible to destroy I<parent> threads while |
677 | there are still existing I<child> threads. | |
678a9b6c | 678 | |
404aaa48 | 679 | =item Creating threads inside special blocks |
88f8c1df | 680 | |
f2e0bb91 JH |
681 | Creating threads inside C<BEGIN>, C<CHECK> or C<INIT> blocks should not be |
682 | relied upon. Depending on the Perl version and the application code, results | |
58a3a76c | 683 | may range from success, to (apparently harmless) warnings of leaked scalar, or |
f2e0bb91 | 684 | all the way up to crashing of the Perl interpreter. |
88f8c1df | 685 | |
1152d448 | 686 | =item Unsafe signals |
47ba8780 | 687 | |
1152d448 JH |
688 | Since Perl 5.8.0, signals have been made safer in Perl by postponing their |
689 | handling until the interpreter is in a I<safe> state. See | |
404aaa48 | 690 | L<perl58delta/"Safe Signals"> and L<perlipc/"Deferred Signals (Safe Signals)"> |
1152d448 JH |
691 | for more details. |
692 | ||
693 | Safe signals is the default behavior, and the old, immediate, unsafe | |
694 | signalling behavior is only in effect in the following situations: | |
695 | ||
696 | =over 4 | |
697 | ||
698 | =item * Perl was been built with C<PERL_OLD_SIGNALS> (see C<perl -V>). | |
699 | ||
700 | =item * The environment variable C<PERL_SIGNALS> is set to C<unsafe> (see L<perlrun/"PERL_SIGNALS">). | |
701 | ||
702 | =item * The module L<Perl::Unsafe::Signals> is used. | |
703 | ||
704 | =back | |
705 | ||
706 | If unsafe signals is in effect, then signal handling is not thread-safe, and | |
707 | the C<-E<gt>kill()> signalling method cannot be used. | |
88f8c1df | 708 | |
0f1612a7 JH |
709 | =item Returning closures from threads |
710 | ||
f2e0bb91 JH |
711 | Returning closures from threads should not be relied upon. Depending of the |
712 | Perl version and the application code, results may range from success, to | |
58a3a76c JH |
713 | (apparently harmless) warnings of leaked scalar, or all the way up to crashing |
714 | of the Perl interpreter. | |
0f1612a7 JH |
715 | |
716 | =item Perl Bugs and the CPAN Version of L<threads> | |
717 | ||
718 | Support for threads extents beyond the code in this module (i.e., | |
719 | F<threads.pm> and F<threads.xs>), and into the Perl iterpreter itself. Older | |
720 | versions of Perl contain bugs that may manifest themselves despite using the | |
721 | latest version of L<threads> from CPAN. There is no workaround for this other | |
722 | than upgrading to the lastest version of Perl. | |
723 | ||
724 | (Before you consider posting a bug report, please consult, and possibly post a | |
725 | message to the discussion forum to see if what you've encountered is a known | |
726 | problem.) | |
727 | ||
47ba8780 AB |
728 | =back |
729 | ||
0f1612a7 | 730 | =head1 REQUIREMENTS |
47ba8780 | 731 | |
0f1612a7 | 732 | Perl 5.8.0 or later |
47ba8780 | 733 | |
0f1612a7 | 734 | =head1 SEE ALSO |
47ba8780 | 735 | |
0f1612a7 JH |
736 | L<threads> Discussion Forum on CPAN: |
737 | L<http://www.cpanforum.com/dist/threads> | |
47ba8780 | 738 | |
0f1612a7 | 739 | Annotated POD for L<threads>: |
4dcb9e53 | 740 | L<http://annocpan.org/~JDHEDDEN/threads-1.33/threads.pm> |
47ba8780 | 741 | |
0f1612a7 | 742 | L<threads::shared>, L<perlthrtut> |
47ba8780 | 743 | |
0f1612a7 JH |
744 | L<http://www.perl.com/pub/a/2002/06/11/threads.html> and |
745 | L<http://www.perl.com/pub/a/2002/09/04/threads.html> | |
47ba8780 | 746 | |
0f1612a7 JH |
747 | Perl threads mailing list: |
748 | L<http://lists.cpan.org/showlist.cgi?name=iThreads> | |
47ba8780 | 749 | |
514612b7 JH |
750 | Stack size discussion: |
751 | L<http://www.perlmonks.org/?node_id=532956> | |
752 | ||
0f1612a7 | 753 | =head1 AUTHOR |
47ba8780 | 754 | |
0f1612a7 JH |
755 | Artur Bergman E<lt>sky AT crucially DOT netE<gt> |
756 | ||
757 | threads is released under the same license as Perl. | |
758 | ||
759 | CPAN version produced by Jerry D. Hedden <jdhedden AT cpan DOT org> | |
760 | ||
761 | =head1 ACKNOWLEDGEMENTS | |
762 | ||
763 | Richard Soderberg E<lt>perl AT crystalflame DOT netE<gt> - | |
764 | Helping me out tons, trying to find reasons for races and other weird bugs! | |
765 | ||
766 | Simon Cozens E<lt>simon AT brecon DOT co DOT ukE<gt> - | |
767 | Being there to answer zillions of annoying questions | |
768 | ||
769 | Rocco Caputo E<lt>troc AT netrus DOT netE<gt> | |
47ba8780 | 770 | |
0f1612a7 JH |
771 | Vipul Ved Prakash E<lt>mail AT vipul DOT netE<gt> - |
772 | Helping with debugging | |
47ba8780 | 773 | |
514612b7 JH |
774 | Dean Arnold E<lt>darnold AT presicient DOT comE<gt> - |
775 | Stack size API | |
776 | ||
47ba8780 | 777 | =cut |