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Revision 1.61 by pcg, Fri May 14 13:25:08 2004 UTC vs.
Revision 1.107 by root, Fri Jan 5 18:25:51 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
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).
34
26In this module, coroutines are defined as "callchain + lexical variables 35In this module, coroutines are defined as "callchain + lexical variables +
27+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own 36@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
28callchain, it's own set of lexicals and it's own set of perl's most 37its own set of lexicals and its own set of perls most important global
29important global variables. 38variables.
30 39
31=cut 40=cut
32 41
33package Coro; 42package Coro;
34 43
35BEGIN { eval { require warnings } && warnings->unimport ("uninitialized") } 44use strict;
45no warnings "uninitialized";
36 46
37use Coro::State; 47use Coro::State;
38 48
39use vars qw($idle $main $current); 49use base qw(Coro::State Exporter);
40 50
41use base Exporter; 51our $idle; # idle handler
52our $main; # main coroutine
53our $current; # current coroutine
42 54
43$VERSION = 0.97; 55our $VERSION = '3.3';
44 56
45@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
46%EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
47 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48); 60);
49@EXPORT_OK = @{$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, $ref) = (shift, shift);
61 my @attrs; 76 my @attrs;
62 for (@_) { 77 for (@_) {
89 104
90$main = new Coro; 105$main = new Coro;
91 106
92=item $current (or as function: current) 107=item $current (or as function: current)
93 108
94The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). 109The current coroutine (the last coroutine switched to). The initial value
110is C<$main> (of course).
111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essentiel you are encouraged to use the
114C<Coro::current> function instead.
95 115
96=cut 116=cut
97 117
98# maybe some other module used Coro::Specific before... 118# maybe some other module used Coro::Specific before...
99if ($current) {
100 $main->{specific} = $current->{specific}; 119$main->{specific} = $current->{specific}
101} 120 if $current;
102 121
103$current = $main; 122_set_current $main;
104 123
105sub current() { $current } 124sub current() { $current }
106 125
107=item $idle 126=item $idle
108 127
109The coroutine to switch to when no other coroutine is running. The default 128A callback that is called whenever the scheduler finds no ready coroutines
110implementation prints "FATAL: deadlock detected" and exits. 129to run. The default implementation prints "FATAL: deadlock detected" and
130exits, because the program has no other way to continue.
111 131
112=cut 132This hook is overwritten by modules such as C<Coro::Timer> and
133C<Coro::Event> to wait on an external event that hopefully wake up a
134coroutine so the scheduler can run it.
113 135
114# should be done using priorities :( 136Please note that if your callback recursively invokes perl (e.g. for event
115$idle = new Coro sub { 137handlers), then it must be prepared to be called recursively.
116 print STDERR "FATAL: deadlock detected\n"; 138
117 exit(51); 139=cut
140
141$idle = sub {
142 require Carp;
143 Carp::croak ("FATAL: deadlock detected");
118}; 144};
145
146sub _cancel {
147 my ($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}
119 157
120# this coroutine is necessary because a coroutine 158# this coroutine is necessary because a coroutine
121# cannot destroy itself. 159# cannot destroy itself.
122my @destroy; 160my @destroy;
123my $manager; 161my $manager;
162
124$manager = new Coro sub { 163$manager = new Coro sub {
125 while () { 164 while () {
126 # by overwriting the state object with the manager we destroy it 165 (shift @destroy)->_cancel
127 # while still being able to schedule this coroutine (in case it has
128 # been readied multiple times. this is harmless since the manager
129 # can be called as many times as neccessary and will always
130 # remove itself from the runqueue
131 while (@destroy) { 166 while @destroy;
132 my $coro = pop @destroy;
133 $coro->{status} ||= [];
134 $_->ready for @{delete $coro->{join} || []};
135 167
136 # the next line destroys the _coro_state, but keeps the
137 # process itself intact (we basically make it a zombie
138 # process that always runs the manager thread, so it's possible
139 # to transfer() to this process).
140 $coro->{_coro_state} = $manager->{_coro_state};
141 }
142 &schedule; 168 &schedule;
143 } 169 }
144}; 170};
145 171
172$manager->prio (PRIO_MAX);
173
146# static methods. not really. 174# static methods. not really.
147 175
148=back 176=back
149 177
150=head2 STATIC METHODS 178=head2 STATIC METHODS
151 179
152Static methods are actually functions that operate on the current process only. 180Static methods are actually functions that operate on the current coroutine only.
153 181
154=over 4 182=over 4
155 183
156=item async { ... } [@args...] 184=item async { ... } [@args...]
157 185
158Create a new asynchronous process and return it's process object 186Create a new asynchronous coroutine and return it's coroutine object
159(usually unused). When the sub returns the new process is automatically 187(usually unused). When the sub returns the new coroutine is automatically
160terminated. 188terminated.
189
190Calling C<exit> in a coroutine will not work correctly, so do not do that.
191
192When the coroutine dies, the program will exit, just as in the main
193program.
161 194
162 # create a new coroutine that just prints its arguments 195 # create a new coroutine that just prints its arguments
163 async { 196 async {
164 print "@_\n"; 197 print "@_\n";
165 } 1,2,3,4; 198 } 1,2,3,4;
166 199
167=cut 200=cut
168 201
169sub async(&@) { 202sub async(&@) {
170 my $pid = new Coro @_; 203 my $coro = new Coro @_;
171 $manager->ready; # this ensures that the stack is cloned from the manager
172 $pid->ready; 204 $coro->ready;
173 $pid; 205 $coro
206}
207
208=item async_pool { ... } [@args...]
209
210Similar to C<async>, but uses a coroutine pool, so you should not call
211terminate or join (although you are allowed to), and you get a coroutine
212that might have executed other code already (which can be good or bad :).
213
214Also, the block is executed in an C<eval> context and a warning will be
215issued in case of an exception instead of terminating the program, as C<async> does.
216
217The priority will be reset to C<0> after each job, otherwise the coroutine
218will be re-used "as-is".
219
220The pool size is limited to 8 idle coroutines (this can be adjusted by
221changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
222required.
223
224If you are concerned about pooled coroutines growing a lot because a
225single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {
226terminate }> once per second or so to slowly replenish the pool.
227
228=cut
229
230our $POOL_SIZE = 8;
231our @pool;
232
233sub pool_handler {
234 while () {
235 my ($cb, @arg) = @{ delete $current->{_invoke} };
236
237 eval {
238 $cb->(@arg);
239 };
240 warn $@ if $@;
241
242 last if @pool >= $POOL_SIZE;
243 push @pool, $current;
244
245 $current->prio (0);
246 schedule;
247 }
248}
249
250sub async_pool(&@) {
251 # this is also inlined into the unlock_scheduler
252 my $coro = (pop @pool or new Coro \&pool_handler);
253
254 $coro->{_invoke} = [@_];
255 $coro->ready;
256
257 $coro
174} 258}
175 259
176=item schedule 260=item schedule
177 261
178Calls the scheduler. Please note that the current process will not be put 262Calls the scheduler. Please note that the current coroutine will not be put
179into the ready queue, so calling this function usually means you will 263into the ready queue, so calling this function usually means you will
180never be called again. 264never be called again unless something else (e.g. an event handler) calls
265ready.
181 266
182=cut 267The canonical way to wait on external events is this:
268
269 {
270 # remember current coroutine
271 my $current = $Coro::current;
272
273 # register a hypothetical event handler
274 on_event_invoke sub {
275 # wake up sleeping coroutine
276 $current->ready;
277 undef $current;
278 };
279
280 # call schedule until event occured.
281 # in case we are woken up for other reasons
282 # (current still defined), loop.
283 Coro::schedule while $current;
284 }
183 285
184=item cede 286=item cede
185 287
186"Cede" to other processes. This function puts the current process into the 288"Cede" to other coroutines. This function puts the current coroutine into the
187ready queue and calls C<schedule>, which has the effect of giving up the 289ready queue and calls C<schedule>, which has the effect of giving up the
188current "timeslice" to other coroutines of the same or higher priority. 290current "timeslice" to other coroutines of the same or higher priority.
189 291
190=cut 292Returns true if at least one coroutine switch has happened.
293
294=item Coro::cede_notself
295
296Works like cede, but is not exported by default and will cede to any
297coroutine, regardless of priority, once.
298
299Returns true if at least one coroutine switch has happened.
191 300
192=item terminate [arg...] 301=item terminate [arg...]
193 302
194Terminates the current process with the given status values (see L<cancel>). 303Terminates the current coroutine with the given status values (see L<cancel>).
195 304
196=cut 305=cut
197 306
198sub terminate { 307sub terminate {
199 $current->cancel (@_); 308 $current->cancel (@_);
201 310
202=back 311=back
203 312
204# dynamic methods 313# dynamic methods
205 314
206=head2 PROCESS METHODS 315=head2 COROUTINE METHODS
207 316
208These are the methods you can call on process objects. 317These are the methods you can call on coroutine objects.
209 318
210=over 4 319=over 4
211 320
212=item new Coro \&sub [, @args...] 321=item new Coro \&sub [, @args...]
213 322
214Create a new process and return it. When the sub returns the process 323Create a new coroutine and return it. When the sub returns the coroutine
215automatically terminates as if C<terminate> with the returned values were 324automatically terminates as if C<terminate> with the returned values were
216called. To make the process run you must first put it into the ready queue 325called. To make the coroutine run you must first put it into the ready queue
217by calling the ready method. 326by calling the ready method.
218 327
219=cut 328Calling C<exit> in a coroutine will not work correctly, so do not do that.
220 329
330=cut
331
221sub _newcoro { 332sub _run_coro {
222 terminate &{+shift}; 333 terminate &{+shift};
223} 334}
224 335
225sub new { 336sub new {
226 my $class = shift; 337 my $class = shift;
227 bless {
228 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
229 }, $class;
230}
231 338
232=item $process->ready 339 $class->SUPER::new (\&_run_coro, @_)
340}
233 341
234Put the given process into the ready queue. 342=item $success = $coroutine->ready
235 343
236=cut 344Put the given coroutine into the ready queue (according to it's priority)
345and return true. If the coroutine is already in the ready queue, do nothing
346and return false.
237 347
348=item $is_ready = $coroutine->is_ready
349
350Return wether the coroutine is currently the ready queue or not,
351
238=item $process->cancel (arg...) 352=item $coroutine->cancel (arg...)
239 353
240Temrinates the given process and makes it return the given arguments as 354Terminates the given coroutine and makes it return the given arguments as
241status (default: the empty list). 355status (default: the empty list). Never returns if the coroutine is the
356current coroutine.
242 357
243=cut 358=cut
244 359
245sub cancel { 360sub cancel {
246 my $self = shift; 361 my $self = shift;
247 $self->{status} = [@_]; 362 $self->{status} = [@_];
363
364 if ($current == $self) {
248 push @destroy, $self; 365 push @destroy, $self;
249 $manager->ready; 366 $manager->ready;
250 &schedule if $current == $self; 367 &schedule while 1;
368 } else {
369 $self->_cancel;
370 }
251} 371}
252 372
253=item $process->join 373=item $coroutine->join
254 374
255Wait until the coroutine terminates and return any values given to the 375Wait until the coroutine terminates and return any values given to the
256C<terminate> or C<cancel> functions. C<join> can be called multiple times 376C<terminate> or C<cancel> functions. C<join> can be called multiple times
257from multiple processes. 377from multiple coroutine.
258 378
259=cut 379=cut
260 380
261sub join { 381sub join {
262 my $self = shift; 382 my $self = shift;
383
263 unless ($self->{status}) { 384 unless ($self->{status}) {
264 push @{$self->{join}}, $current; 385 my $current = $current;
265 &schedule; 386
387 push @{$self->{destroy_cb}}, sub {
388 $current->ready;
389 undef $current;
390 };
391
392 &schedule while $current;
266 } 393 }
394
267 wantarray ? @{$self->{status}} : $self->{status}[0]; 395 wantarray ? @{$self->{status}} : $self->{status}[0];
268} 396}
269 397
398=item $coroutine->on_destroy (\&cb)
399
400Registers a callback that is called when this coroutine gets destroyed,
401but before it is joined. The callback gets passed the terminate arguments,
402if any.
403
404=cut
405
406sub on_destroy {
407 my ($self, $cb) = @_;
408
409 push @{ $self->{destroy_cb} }, $cb;
410}
411
270=item $oldprio = $process->prio($newprio) 412=item $oldprio = $coroutine->prio ($newprio)
271 413
272Sets (or gets, if the argument is missing) the priority of the 414Sets (or gets, if the argument is missing) the priority of the
273process. Higher priority processes get run before lower priority 415coroutine. Higher priority coroutines get run before lower priority
274processes. Priorities are small signed integers (currently -4 .. +3), 416coroutines. Priorities are small signed integers (currently -4 .. +3),
275that you can refer to using PRIO_xxx constants (use the import tag :prio 417that you can refer to using PRIO_xxx constants (use the import tag :prio
276to get then): 418to get then):
277 419
278 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 420 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
279 3 > 1 > 0 > -1 > -3 > -4 421 3 > 1 > 0 > -1 > -3 > -4
282 current->prio(PRIO_HIGH); 424 current->prio(PRIO_HIGH);
283 425
284The idle coroutine ($Coro::idle) always has a lower priority than any 426The idle coroutine ($Coro::idle) always has a lower priority than any
285existing coroutine. 427existing coroutine.
286 428
287Changing the priority of the current process will take effect immediately, 429Changing the priority of the current coroutine will take effect immediately,
288but changing the priority of processes in the ready queue (but not 430but changing the priority of coroutines in the ready queue (but not
289running) will only take effect after the next schedule (of that 431running) will only take effect after the next schedule (of that
290process). This is a bug that will be fixed in some future version. 432coroutine). This is a bug that will be fixed in some future version.
291 433
292=cut
293
294sub prio {
295 my $old = $_[0]{prio};
296 $_[0]{prio} = $_[1] if @_ > 1;
297 $old;
298}
299
300=item $newprio = $process->nice($change) 434=item $newprio = $coroutine->nice ($change)
301 435
302Similar to C<prio>, but subtract the given value from the priority (i.e. 436Similar to C<prio>, but subtract the given value from the priority (i.e.
303higher values mean lower priority, just as in unix). 437higher values mean lower priority, just as in unix).
304 438
305=cut
306
307sub nice {
308 $_[0]{prio} -= $_[1];
309}
310
311=item $olddesc = $process->desc($newdesc) 439=item $olddesc = $coroutine->desc ($newdesc)
312 440
313Sets (or gets in case the argument is missing) the description for this 441Sets (or gets in case the argument is missing) the description for this
314process. This is just a free-form string you can associate with a process. 442coroutine. This is just a free-form string you can associate with a coroutine.
315 443
316=cut 444=cut
317 445
318sub desc { 446sub desc {
319 my $old = $_[0]{desc}; 447 my $old = $_[0]{desc};
321 $old; 449 $old;
322} 450}
323 451
324=back 452=back
325 453
454=head2 GLOBAL FUNCTIONS
455
456=over 4
457
458=item Coro::nready
459
460Returns the number of coroutines that are currently in the ready state,
461i.e. that can be swicthed to. The value C<0> means that the only runnable
462coroutine is the currently running one, so C<cede> would have no effect,
463and C<schedule> would cause a deadlock unless there is an idle handler
464that wakes up some coroutines.
465
466=item my $guard = Coro::guard { ... }
467
468This creates and returns a guard object. Nothing happens until the objetc
469gets destroyed, in which case the codeblock given as argument will be
470executed. This is useful to free locks or other resources in case of a
471runtime error or when the coroutine gets canceled, as in both cases the
472guard block will be executed. The guard object supports only one method,
473C<< ->cancel >>, which will keep the codeblock from being executed.
474
475Example: set some flag and clear it again when the coroutine gets canceled
476or the function returns:
477
478 sub do_something {
479 my $guard = Coro::guard { $busy = 0 };
480 $busy = 1;
481
482 # do something that requires $busy to be true
483 }
484
485=cut
486
487sub guard(&) {
488 bless \(my $cb = $_[0]), "Coro::guard"
489}
490
491sub Coro::guard::cancel {
492 ${$_[0]} = sub { };
493}
494
495sub Coro::guard::DESTROY {
496 ${$_[0]}->();
497}
498
499
500=item unblock_sub { ... }
501
502This utility function takes a BLOCK or code reference and "unblocks" it,
503returning the new coderef. This means that the new coderef will return
504immediately without blocking, returning nothing, while the original code
505ref will be called (with parameters) from within its own coroutine.
506
507The reason this fucntion exists is that many event libraries (such as the
508venerable L<Event|Event> module) are not coroutine-safe (a weaker form
509of thread-safety). This means you must not block within event callbacks,
510otherwise you might suffer from crashes or worse.
511
512This function allows your callbacks to block by executing them in another
513coroutine where it is safe to block. One example where blocking is handy
514is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
515disk.
516
517In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
518creating event callbacks that want to block.
519
520=cut
521
522our @unblock_queue;
523
524# we create a special coro because we want to cede,
525# to reduce pressure on the coro pool (because most callbacks
526# return immediately and can be reused) and because we cannot cede
527# inside an event callback.
528our $unblock_scheduler = async {
529 while () {
530 while (my $cb = pop @unblock_queue) {
531 # this is an inlined copy of async_pool
532 my $coro = (pop @pool or new Coro \&pool_handler);
533
534 $coro->{_invoke} = $cb;
535 $coro->ready;
536 cede; # for short-lived callbacks, this reduces pressure on the coro pool
537 }
538 schedule; # sleep well
539 }
540};
541
542sub unblock_sub(&) {
543 my $cb = shift;
544
545 sub {
546 unshift @unblock_queue, [$cb, @_];
547 $unblock_scheduler->ready;
548 }
549}
550
551=back
552
326=cut 553=cut
327 554
3281; 5551;
329 556
330=head1 BUGS/LIMITATIONS 557=head1 BUGS/LIMITATIONS
337 to allow per-thread schedulers, but Coro::State does not yet allow 564 to allow per-thread schedulers, but Coro::State does not yet allow
338 this). 565 this).
339 566
340=head1 SEE ALSO 567=head1 SEE ALSO
341 568
342L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 569Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
343L<Coro::Signal>, L<Coro::State>, L<Coro::Timer>, L<Coro::Event>, 570
344L<Coro::L<Coro::RWLock>, Handle>, L<Coro::Socket>. 571Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
572
573Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
574
575Embedding: L<Coro:MakeMaker>
345 576
346=head1 AUTHOR 577=head1 AUTHOR
347 578
348 Marc Lehmann <pcg@goof.com> 579 Marc Lehmann <schmorp@schmorp.de>
349 http://www.goof.com/pcg/marc/ 580 http://home.schmorp.de/
350 581
351=cut 582=cut
352 583

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