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Revision 1.121 by root, Fri Apr 13 12:56:55 2007 UTC

8 8
9 async { 9 async {
10 # some asynchronous thread of execution 10 # some asynchronous thread of execution
11 }; 11 };
12 12
13 # alternatively create an async process like this: 13 # alternatively create an async coroutine like this:
14 14
15 sub some_func : Coro { 15 sub some_func : Coro {
16 # some more async code 16 # some more async code
17 } 17 }
18 18
19 cede; 19 cede;
20 20
21=head1 DESCRIPTION 21=head1 DESCRIPTION
22 22
23This module collection manages coroutines. Coroutines are similar to 23This module collection manages coroutines. Coroutines are similar
24Threads but don't run in parallel. 24to threads but don't run in parallel at the same time even on SMP
25machines. The specific flavor of coroutine use din this module also
26guarentees you that it will not switch between coroutines unless
27necessary, at easily-identified points in your program, so locking and
28parallel access are rarely an issue, making coroutine programming much
29safer than threads programming.
25 30
26This module is still experimental, see the BUGS section below. 31(Perl, however, does not natively support real threads but instead does a
32very slow and memory-intensive emulation of processes using threads. This
33is a performance win on Windows machines, and a loss everywhere else).
27 34
28In this module, coroutines are defined as "callchain + lexical variables 35In this module, coroutines are defined as "callchain + lexical variables +
29+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own 36@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
30callchain, it's own set of lexicals and it's own set of perl's most 37its own set of lexicals and its own set of perls most important global
31important global variables. 38variables.
32 39
33=cut 40=cut
34 41
35package Coro; 42package Coro;
36 43
44use strict;
37no warnings qw(uninitialized); 45no warnings "uninitialized";
38 46
39use Coro::State; 47use Coro::State;
40 48
41use base Exporter; 49use base qw(Coro::State Exporter);
42 50
51our $idle; # idle handler
52our $main; # main coroutine
53our $current; # current coroutine
54
43$VERSION = 0.5; 55our $VERSION = '3.56';
44 56
45@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
46%EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
47 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48); 60);
49@EXPORT_OK = @{$EXPORT_TAGS{prio}}; 61our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
50 62
51{ 63{
52 my @async; 64 my @async;
53 my $init; 65 my $init;
54 66
55 # this way of handling attributes simply is NOT scalable ;() 67 # this way of handling attributes simply is NOT scalable ;()
56 sub import { 68 sub import {
69 no strict 'refs';
70
57 Coro->export_to_level(1, @_); 71 Coro->export_to_level (1, @_);
72
58 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; 73 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
59 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { 74 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
60 my ($package, $ref) = (shift, shift); 75 my ($package, $ref) = (shift, shift);
61 my @attrs; 76 my @attrs;
62 for (@_) { 77 for (@_) {
77 }; 92 };
78 } 93 }
79 94
80} 95}
81 96
97=over 4
98
82=item $main 99=item $main
83 100
84This coroutine represents the main program. 101This coroutine represents the main program.
85 102
86=cut 103=cut
87 104
88our $main = new Coro; 105$main = new Coro;
89 106
90=item $current (or as function: current) 107=item $current (or as function: current)
91 108
92The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). 109The current coroutine (the last coroutine switched to). The initial value
110is C<$main> (of course).
111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essentiel you are encouraged to use the
114C<Coro::current> function instead.
93 115
94=cut 116=cut
95 117
96# maybe some other module used Coro::Specific before... 118# maybe some other module used Coro::Specific before...
97if ($current) {
98 $main->{specific} = $current->{specific}; 119$main->{specific} = $current->{specific}
99} 120 if $current;
100 121
101our $current = $main; 122_set_current $main;
102 123
103sub current() { $current } 124sub current() { $current }
104 125
105=item $idle 126=item $idle
106 127
107The coroutine to switch to when no other coroutine is running. The default 128A callback that is called whenever the scheduler finds no ready coroutines
108implementation prints "FATAL: deadlock detected" and exits. 129to run. The default implementation prints "FATAL: deadlock detected" and
130exits, because the program has no other way to continue.
109 131
110=cut 132This hook is overwritten by modules such as C<Coro::Timer> and
133C<Coro::Event> to wait on an external event that hopefully wake up a
134coroutine so the scheduler can run it.
111 135
112# should be done using priorities :( 136Please note that if your callback recursively invokes perl (e.g. for event
113our $idle = new Coro sub { 137handlers), then it must be prepared to be called recursively.
114 print STDERR "FATAL: deadlock detected\n"; 138
115 exit(51); 139=cut
140
141$idle = sub {
142 require Carp;
143 Carp::croak ("FATAL: deadlock detected");
116}; 144};
145
146sub _cancel {
147 my ($self) = @_;
148
149 # free coroutine data and mark as destructed
150 $self->_destroy
151 or return;
152
153 # call all destruction callbacks
154 $_->(@{$self->{status}})
155 for @{(delete $self->{destroy_cb}) || []};
156}
117 157
118# this coroutine is necessary because a coroutine 158# this coroutine is necessary because a coroutine
119# cannot destroy itself. 159# cannot destroy itself.
120my @destroy; 160my @destroy;
161my $manager;
162
121my $manager = new Coro sub { 163$manager = new Coro sub {
122 while() { 164 while () {
123 delete ((pop @destroy)->{_coro_state}) while @destroy; 165 (shift @destroy)->_cancel
166 while @destroy;
167
124 &schedule; 168 &schedule;
125 } 169 }
126}; 170};
127 171
172$manager->prio (PRIO_MAX);
173
128# static methods. not really. 174# static methods. not really.
129 175
176=back
177
130=head2 STATIC METHODS 178=head2 STATIC METHODS
131 179
132Static methods are actually functions that operate on the current process only. 180Static methods are actually functions that operate on the current coroutine only.
133 181
134=over 4 182=over 4
135 183
136=item async { ... } [@args...] 184=item async { ... } [@args...]
137 185
138Create a new asynchronous process and return it's process object 186Create a new asynchronous coroutine and return it's coroutine object
139(usually unused). When the sub returns the new process is automatically 187(usually unused). When the sub returns the new coroutine is automatically
140terminated. 188terminated.
189
190Calling C<exit> in a coroutine will try to do the same as calling exit
191outside the coroutine, but this is experimental. It is best not to rely on
192exit doing any cleanups or even not crashing.
193
194When the coroutine dies, the program will exit, just as in the main
195program.
141 196
142 # create a new coroutine that just prints its arguments 197 # create a new coroutine that just prints its arguments
143 async { 198 async {
144 print "@_\n"; 199 print "@_\n";
145 } 1,2,3,4; 200 } 1,2,3,4;
146 201
147The coderef you submit MUST NOT be a closure that refers to variables
148in an outer scope. This does NOT work. Pass arguments into it instead.
149
150=cut 202=cut
151 203
152sub async(&@) { 204sub async(&@) {
153 my $pid = new Coro @_; 205 my $coro = new Coro @_;
154 $manager->ready; # this ensures that the stack is cloned from the manager
155 $pid->ready; 206 $coro->ready;
156 $pid; 207 $coro
208}
209
210=item async_pool { ... } [@args...]
211
212Similar to C<async>, but uses a coroutine pool, so you should not call
213terminate or join (although you are allowed to), and you get a coroutine
214that might have executed other code already (which can be good or bad :).
215
216Also, the block is executed in an C<eval> context and a warning will be
217issued in case of an exception instead of terminating the program, as
218C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
219will not work in the expected way, unless you call terminate or cancel,
220which somehow defeats the purpose of pooling.
221
222The priority will be reset to C<0> after each job, otherwise the coroutine
223will be re-used "as-is".
224
225The pool size is limited to 8 idle coroutines (this can be adjusted by
226changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
227required.
228
229If you are concerned about pooled coroutines growing a lot because a
230single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {
231terminate }> once per second or so to slowly replenish the pool.
232
233=cut
234
235our $POOL_SIZE = 8;
236our @pool;
237
238sub pool_handler {
239 while () {
240 eval {
241 my ($cb, @arg) = @{ delete $current->{_invoke} or return };
242 $cb->(@arg);
243 };
244 warn $@ if $@;
245
246 last if @pool >= $POOL_SIZE;
247 push @pool, $current;
248
249 $current->save (Coro::State::SAVE_DEF);
250 $current->prio (0);
251 schedule;
252 }
253}
254
255sub async_pool(&@) {
256 # this is also inlined into the unlock_scheduler
257 my $coro = (pop @pool or new Coro \&pool_handler);
258
259 $coro->{_invoke} = [@_];
260 $coro->ready;
261
262 $coro
157} 263}
158 264
159=item schedule 265=item schedule
160 266
161Calls the scheduler. Please note that the current process will not be put 267Calls the scheduler. Please note that the current coroutine will not be put
162into the ready queue, so calling this function usually means you will 268into the ready queue, so calling this function usually means you will
163never be called again. 269never be called again unless something else (e.g. an event handler) calls
270ready.
164 271
165=cut 272The canonical way to wait on external events is this:
273
274 {
275 # remember current coroutine
276 my $current = $Coro::current;
277
278 # register a hypothetical event handler
279 on_event_invoke sub {
280 # wake up sleeping coroutine
281 $current->ready;
282 undef $current;
283 };
284
285 # call schedule until event occured.
286 # in case we are woken up for other reasons
287 # (current still defined), loop.
288 Coro::schedule while $current;
289 }
166 290
167=item cede 291=item cede
168 292
169"Cede" to other processes. This function puts the current process into the 293"Cede" to other coroutines. This function puts the current coroutine into the
170ready queue and calls C<schedule>, which has the effect of giving up the 294ready queue and calls C<schedule>, which has the effect of giving up the
171current "timeslice" to other coroutines of the same or higher priority. 295current "timeslice" to other coroutines of the same or higher priority.
172 296
173=cut 297Returns true if at least one coroutine switch has happened.
174 298
299=item Coro::cede_notself
300
301Works like cede, but is not exported by default and will cede to any
302coroutine, regardless of priority, once.
303
304Returns true if at least one coroutine switch has happened.
305
175=item terminate 306=item terminate [arg...]
176 307
177Terminates the current process. 308Terminates the current coroutine with the given status values (see L<cancel>).
178
179Future versions of this function will allow result arguments.
180 309
181=cut 310=cut
182 311
183sub terminate { 312sub terminate {
184 $current->cancel; 313 $current->cancel (@_);
185 &schedule;
186 die; # NORETURN
187} 314}
188 315
189=back 316=back
190 317
191# dynamic methods 318# dynamic methods
192 319
193=head2 PROCESS METHODS 320=head2 COROUTINE METHODS
194 321
195These are the methods you can call on process objects. 322These are the methods you can call on coroutine objects.
196 323
197=over 4 324=over 4
198 325
199=item new Coro \&sub [, @args...] 326=item new Coro \&sub [, @args...]
200 327
201Create a new process and return it. When the sub returns the process 328Create a new coroutine and return it. When the sub returns the coroutine
202automatically terminates. To start the process you must first put it into 329automatically terminates as if C<terminate> with the returned values were
330called. To make the coroutine run you must first put it into the ready queue
203the ready queue by calling the ready method. 331by calling the ready method.
204 332
205The coderef you submit MUST NOT be a closure that refers to variables 333See C<async> for additional discussion.
206in an outer scope. This does NOT work. Pass arguments into it instead.
207 334
208=cut 335=cut
209 336
210sub _newcoro { 337sub _run_coro {
211 terminate &{+shift}; 338 terminate &{+shift};
212} 339}
213 340
214sub new { 341sub new {
215 my $class = shift; 342 my $class = shift;
216 bless {
217 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
218 }, $class;
219}
220 343
221=item $process->ready 344 $class->SUPER::new (\&_run_coro, @_)
345}
222 346
223Put the current process into the ready queue. 347=item $success = $coroutine->ready
224 348
225=cut 349Put the given coroutine into the ready queue (according to it's priority)
350and return true. If the coroutine is already in the ready queue, do nothing
351and return false.
226 352
227=item $process->cancel 353=item $is_ready = $coroutine->is_ready
228 354
229Like C<terminate>, but terminates the specified process instead. 355Return wether the coroutine is currently the ready queue or not,
356
357=item $coroutine->cancel (arg...)
358
359Terminates the given coroutine and makes it return the given arguments as
360status (default: the empty list). Never returns if the coroutine is the
361current coroutine.
230 362
231=cut 363=cut
232 364
233sub cancel { 365sub cancel {
366 my $self = shift;
367 $self->{status} = [@_];
368
369 if ($current == $self) {
234 push @destroy, $_[0]; 370 push @destroy, $self;
235 $manager->ready; 371 $manager->ready;
236 &schedule if $current == $_[0]; 372 &schedule while 1;
373 } else {
374 $self->_cancel;
375 }
237} 376}
238 377
378=item $coroutine->join
379
380Wait until the coroutine terminates and return any values given to the
381C<terminate> or C<cancel> functions. C<join> can be called multiple times
382from multiple coroutine.
383
384=cut
385
386sub join {
387 my $self = shift;
388
389 unless ($self->{status}) {
390 my $current = $current;
391
392 push @{$self->{destroy_cb}}, sub {
393 $current->ready;
394 undef $current;
395 };
396
397 &schedule while $current;
398 }
399
400 wantarray ? @{$self->{status}} : $self->{status}[0];
401}
402
403=item $coroutine->on_destroy (\&cb)
404
405Registers a callback that is called when this coroutine gets destroyed,
406but before it is joined. The callback gets passed the terminate arguments,
407if any.
408
409=cut
410
411sub on_destroy {
412 my ($self, $cb) = @_;
413
414 push @{ $self->{destroy_cb} }, $cb;
415}
416
239=item $oldprio = $process->prio($newprio) 417=item $oldprio = $coroutine->prio ($newprio)
240 418
241Sets the priority of the process. Higher priority processes get run before 419Sets (or gets, if the argument is missing) the priority of the
242lower priority processes. Priorities are smalled signed integer (currently 420coroutine. Higher priority coroutines get run before lower priority
421coroutines. Priorities are small signed integers (currently -4 .. +3),
243-4 .. +3), that you can refer to using PRIO_xxx constants (use the import 422that you can refer to using PRIO_xxx constants (use the import tag :prio
244tag :prio to get then): 423to get then):
245 424
246 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 425 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
247 3 > 1 > 0 > -1 > -3 > -4 426 3 > 1 > 0 > -1 > -3 > -4
248 427
249 # set priority to HIGH 428 # set priority to HIGH
250 current->prio(PRIO_HIGH); 429 current->prio(PRIO_HIGH);
251 430
252The idle coroutine ($Coro::idle) always has a lower priority than any 431The idle coroutine ($Coro::idle) always has a lower priority than any
253existing coroutine. 432existing coroutine.
254 433
255Changing the priority of the current process will take effect immediately, 434Changing the priority of the current coroutine will take effect immediately,
256but changing the priority of processes in the ready queue (but not 435but changing the priority of coroutines in the ready queue (but not
257running) will only take effect after the next schedule (of that 436running) will only take effect after the next schedule (of that
258process). This is a bug that will be fixed in some future version. 437coroutine). This is a bug that will be fixed in some future version.
259 438
260=cut
261
262sub prio {
263 my $old = $_[0]{prio};
264 $_[0]{prio} = $_[1] if @_ > 1;
265 $old;
266}
267
268=item $newprio = $process->nice($change) 439=item $newprio = $coroutine->nice ($change)
269 440
270Similar to C<prio>, but subtract the given value from the priority (i.e. 441Similar to C<prio>, but subtract the given value from the priority (i.e.
271higher values mean lower priority, just as in unix). 442higher values mean lower priority, just as in unix).
272 443
273=cut 444=item $olddesc = $coroutine->desc ($newdesc)
274 445
275sub nice { 446Sets (or gets in case the argument is missing) the description for this
276 $_[0]{prio} -= $_[1]; 447coroutine. This is just a free-form string you can associate with a coroutine.
448
449=cut
450
451sub desc {
452 my $old = $_[0]{desc};
453 $_[0]{desc} = $_[1] if @_ > 1;
454 $old;
277} 455}
278 456
279=back 457=back
280 458
459=head2 GLOBAL FUNCTIONS
460
461=over 4
462
463=item Coro::nready
464
465Returns the number of coroutines that are currently in the ready state,
466i.e. that can be swicthed to. The value C<0> means that the only runnable
467coroutine is the currently running one, so C<cede> would have no effect,
468and C<schedule> would cause a deadlock unless there is an idle handler
469that wakes up some coroutines.
470
471=item my $guard = Coro::guard { ... }
472
473This creates and returns a guard object. Nothing happens until the object
474gets destroyed, in which case the codeblock given as argument will be
475executed. This is useful to free locks or other resources in case of a
476runtime error or when the coroutine gets canceled, as in both cases the
477guard block will be executed. The guard object supports only one method,
478C<< ->cancel >>, which will keep the codeblock from being executed.
479
480Example: set some flag and clear it again when the coroutine gets canceled
481or the function returns:
482
483 sub do_something {
484 my $guard = Coro::guard { $busy = 0 };
485 $busy = 1;
486
487 # do something that requires $busy to be true
488 }
489
490=cut
491
492sub guard(&) {
493 bless \(my $cb = $_[0]), "Coro::guard"
494}
495
496sub Coro::guard::cancel {
497 ${$_[0]} = sub { };
498}
499
500sub Coro::guard::DESTROY {
501 ${$_[0]}->();
502}
503
504
505=item unblock_sub { ... }
506
507This utility function takes a BLOCK or code reference and "unblocks" it,
508returning the new coderef. This means that the new coderef will return
509immediately without blocking, returning nothing, while the original code
510ref will be called (with parameters) from within its own coroutine.
511
512The reason this fucntion exists is that many event libraries (such as the
513venerable L<Event|Event> module) are not coroutine-safe (a weaker form
514of thread-safety). This means you must not block within event callbacks,
515otherwise you might suffer from crashes or worse.
516
517This function allows your callbacks to block by executing them in another
518coroutine where it is safe to block. One example where blocking is handy
519is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
520disk.
521
522In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
523creating event callbacks that want to block.
524
525=cut
526
527our @unblock_queue;
528
529# we create a special coro because we want to cede,
530# to reduce pressure on the coro pool (because most callbacks
531# return immediately and can be reused) and because we cannot cede
532# inside an event callback.
533our $unblock_scheduler = async {
534 while () {
535 while (my $cb = pop @unblock_queue) {
536 # this is an inlined copy of async_pool
537 my $coro = (pop @pool or new Coro \&pool_handler);
538
539 $coro->{_invoke} = $cb;
540 $coro->ready;
541 cede; # for short-lived callbacks, this reduces pressure on the coro pool
542 }
543 schedule; # sleep well
544 }
545};
546
547sub unblock_sub(&) {
548 my $cb = shift;
549
550 sub {
551 unshift @unblock_queue, [$cb, @_];
552 $unblock_scheduler->ready;
553 }
554}
555
556=back
557
281=cut 558=cut
282 559
2831; 5601;
284 561
285=head1 BUGS/LIMITATIONS 562=head1 BUGS/LIMITATIONS
286 563
287 - you must make very sure that no coro is still active on global destruction. 564 - you must make very sure that no coro is still active on global
288 very bad things might happen otherwise (usually segfaults). 565 destruction. very bad things might happen otherwise (usually segfaults).
566
289 - this module is not thread-safe. You must only ever use this module from 567 - this module is not thread-safe. You should only ever use this module
290 the same thread (this requirement might be loosened in the future to 568 from the same thread (this requirement might be losened in the future
291 allow per-thread schedulers, but Coro::State does not yet allow this). 569 to allow per-thread schedulers, but Coro::State does not yet allow
570 this).
292 571
293=head1 SEE ALSO 572=head1 SEE ALSO
294 573
295L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 574Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
296L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>, 575
297L<Coro::Handle>, L<Coro::Socket>. 576Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
577
578Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
579
580Embedding: L<Coro:MakeMaker>
298 581
299=head1 AUTHOR 582=head1 AUTHOR
300 583
301 Marc Lehmann <pcg@goof.com> 584 Marc Lehmann <schmorp@schmorp.de>
302 http://www.goof.com/pcg/marc/ 585 http://home.schmorp.de/
303 586
304=cut 587=cut
305 588

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