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Revision 1.47 by root, Mon Feb 25 03:21:08 2002 UTC vs.
Revision 1.119 by root, Wed Mar 28 14:24:17 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@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
28callchain, it's own set of lexicals and it's own set of perl's most 37its own set of lexicals and its own set of perls most important global
29important global variables. 38variables.
30 39
31=cut 40=cut
32 41
33package Coro; 42package Coro;
34 43
44use strict;
35no warnings qw(uninitialized); 45no warnings "uninitialized";
36 46
37use Coro::State; 47use Coro::State;
38 48
39use base Exporter; 49use base qw(Coro::State Exporter);
40 50
41$VERSION = 0.533; 51our $idle; # idle handler
52our $main; # main coroutine
53our $current; # current coroutine
42 54
55our $VERSION = '3.55';
56
43@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
44%EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
45 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
46); 60);
47@EXPORT_OK = @{$EXPORT_TAGS{prio}}; 61our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
48 62
49{ 63{
50 my @async; 64 my @async;
51 my $init; 65 my $init;
52 66
53 # this way of handling attributes simply is NOT scalable ;() 67 # this way of handling attributes simply is NOT scalable ;()
54 sub import { 68 sub import {
69 no strict 'refs';
70
55 Coro->export_to_level(1, @_); 71 Coro->export_to_level (1, @_);
72
56 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; 73 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
57 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { 74 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
58 my ($package, $ref) = (shift, shift); 75 my ($package, $ref) = (shift, shift);
59 my @attrs; 76 my @attrs;
60 for (@_) { 77 for (@_) {
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;
121my $manager; 161my $manager;
162
122$manager = new Coro sub { 163$manager = new Coro sub {
123 while() { 164 while () {
124 # by overwriting the state object with the manager we destroy it 165 (shift @destroy)->_cancel
125 # while still being able to schedule this coroutine (in case it has
126 # been readied multiple times. this is harmless since the manager
127 # can be called as many times as neccessary and will always
128 # remove itself from the runqueue
129 while (@destroy) { 166 while @destroy;
130 my $coro = pop @destroy; 167
131 $coro->{status} ||= [];
132 $_->ready for @{delete $coro->{join} || []};
133 $coro->{_coro_state} = $manager->{_coro_state};
134 }
135 &schedule; 168 &schedule;
136 } 169 }
137}; 170};
138 171
172$manager->prio (PRIO_MAX);
173
139# static methods. not really. 174# static methods. not really.
140 175
141=back 176=back
142 177
143=head2 STATIC METHODS 178=head2 STATIC METHODS
144 179
145Static methods are actually functions that operate on the current process only. 180Static methods are actually functions that operate on the current coroutine only.
146 181
147=over 4 182=over 4
148 183
149=item async { ... } [@args...] 184=item async { ... } [@args...]
150 185
151Create a new asynchronous process and return it's process object 186Create a new asynchronous coroutine and return it's coroutine object
152(usually unused). When the sub returns the new process is automatically 187(usually unused). When the sub returns the new coroutine is automatically
153terminated. 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.
154 194
155 # create a new coroutine that just prints its arguments 195 # create a new coroutine that just prints its arguments
156 async { 196 async {
157 print "@_\n"; 197 print "@_\n";
158 } 1,2,3,4; 198 } 1,2,3,4;
159 199
160The coderef you submit MUST NOT be a closure that refers to variables
161in an outer scope. This does NOT work. Pass arguments into it instead.
162
163=cut 200=cut
164 201
165sub async(&@) { 202sub async(&@) {
166 my $pid = new Coro @_; 203 my $coro = new Coro @_;
167 $manager->ready; # this ensures that the stack is cloned from the manager
168 $pid->ready; 204 $coro->ready;
169 $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
216C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
217will not work in the expected way, unless you call terminate or cancel,
218which somehow defeats the purpose of pooling.
219
220The priority will be reset to C<0> after each job, otherwise the coroutine
221will be re-used "as-is".
222
223The pool size is limited to 8 idle coroutines (this can be adjusted by
224changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
225required.
226
227If you are concerned about pooled coroutines growing a lot because a
228single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {
229terminate }> once per second or so to slowly replenish the pool.
230
231=cut
232
233our $POOL_SIZE = 8;
234our @pool;
235
236sub pool_handler {
237 while () {
238 eval {
239 my ($cb, @arg) = @{ delete $current->{_invoke} or return };
240 $cb->(@arg);
241 };
242 warn $@ if $@;
243
244 last if @pool >= $POOL_SIZE;
245 push @pool, $current;
246
247 $current->save (Coro::State::SAVE_DEF);
248 $current->prio (0);
249 schedule;
250 }
251}
252
253sub async_pool(&@) {
254 # this is also inlined into the unlock_scheduler
255 my $coro = (pop @pool or new Coro \&pool_handler);
256
257 $coro->{_invoke} = [@_];
258 $coro->ready;
259
260 $coro
170} 261}
171 262
172=item schedule 263=item schedule
173 264
174Calls the scheduler. Please note that the current process will not be put 265Calls the scheduler. Please note that the current coroutine will not be put
175into the ready queue, so calling this function usually means you will 266into the ready queue, so calling this function usually means you will
176never be called again. 267never be called again unless something else (e.g. an event handler) calls
268ready.
177 269
178=cut 270The canonical way to wait on external events is this:
271
272 {
273 # remember current coroutine
274 my $current = $Coro::current;
275
276 # register a hypothetical event handler
277 on_event_invoke sub {
278 # wake up sleeping coroutine
279 $current->ready;
280 undef $current;
281 };
282
283 # call schedule until event occured.
284 # in case we are woken up for other reasons
285 # (current still defined), loop.
286 Coro::schedule while $current;
287 }
179 288
180=item cede 289=item cede
181 290
182"Cede" to other processes. This function puts the current process into the 291"Cede" to other coroutines. This function puts the current coroutine into the
183ready queue and calls C<schedule>, which has the effect of giving up the 292ready queue and calls C<schedule>, which has the effect of giving up the
184current "timeslice" to other coroutines of the same or higher priority. 293current "timeslice" to other coroutines of the same or higher priority.
185 294
186=cut 295Returns true if at least one coroutine switch has happened.
296
297=item Coro::cede_notself
298
299Works like cede, but is not exported by default and will cede to any
300coroutine, regardless of priority, once.
301
302Returns true if at least one coroutine switch has happened.
187 303
188=item terminate [arg...] 304=item terminate [arg...]
189 305
190Terminates the current process. 306Terminates the current coroutine with the given status values (see L<cancel>).
191
192Future versions of this function will allow result arguments.
193 307
194=cut 308=cut
195 309
196sub terminate { 310sub terminate {
197 $current->{status} = [@_];
198 $current->cancel; 311 $current->cancel (@_);
199 &schedule;
200 die; # NORETURN
201} 312}
202 313
203=back 314=back
204 315
205# dynamic methods 316# dynamic methods
206 317
207=head2 PROCESS METHODS 318=head2 COROUTINE METHODS
208 319
209These are the methods you can call on process objects. 320These are the methods you can call on coroutine objects.
210 321
211=over 4 322=over 4
212 323
213=item new Coro \&sub [, @args...] 324=item new Coro \&sub [, @args...]
214 325
215Create a new process and return it. When the sub returns the process 326Create a new coroutine and return it. When the sub returns the coroutine
216automatically terminates as if C<terminate> with the returned values were 327automatically terminates as if C<terminate> with the returned values were
217called. To make the process run you must first put it into the ready queue 328called. To make the coroutine run you must first put it into the ready queue
218by calling the ready method. 329by calling the ready method.
219 330
220=cut 331Calling C<exit> in a coroutine will not work correctly, so do not do that.
221 332
333=cut
334
222sub _newcoro { 335sub _run_coro {
223 terminate &{+shift}; 336 terminate &{+shift};
224} 337}
225 338
226sub new { 339sub new {
227 my $class = shift; 340 my $class = shift;
228 bless {
229 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
230 }, $class;
231}
232 341
233=item $process->ready 342 $class->SUPER::new (\&_run_coro, @_)
343}
234 344
235Put the given process into the ready queue. 345=item $success = $coroutine->ready
236 346
237=cut 347Put the given coroutine into the ready queue (according to it's priority)
348and return true. If the coroutine is already in the ready queue, do nothing
349and return false.
238 350
239=item $process->cancel 351=item $is_ready = $coroutine->is_ready
240 352
241Like C<terminate>, but terminates the specified process instead. 353Return wether the coroutine is currently the ready queue or not,
354
355=item $coroutine->cancel (arg...)
356
357Terminates the given coroutine and makes it return the given arguments as
358status (default: the empty list). Never returns if the coroutine is the
359current coroutine.
242 360
243=cut 361=cut
244 362
245sub cancel { 363sub cancel {
364 my $self = shift;
365 $self->{status} = [@_];
366
367 if ($current == $self) {
246 push @destroy, $_[0]; 368 push @destroy, $self;
247 $manager->ready; 369 $manager->ready;
248 &schedule if $current == $_[0]; 370 &schedule while 1;
371 } else {
372 $self->_cancel;
373 }
249} 374}
250 375
251=item $process->join 376=item $coroutine->join
252 377
253Wait until the coroutine terminates and return any values given to the 378Wait until the coroutine terminates and return any values given to the
254C<terminate> function. C<join> can be called multiple times from multiple 379C<terminate> or C<cancel> functions. C<join> can be called multiple times
255processes. 380from multiple coroutine.
256 381
257=cut 382=cut
258 383
259sub join { 384sub join {
260 my $self = shift; 385 my $self = shift;
386
261 unless ($self->{status}) { 387 unless ($self->{status}) {
262 push @{$self->{join}}, $current; 388 my $current = $current;
263 &schedule; 389
390 push @{$self->{destroy_cb}}, sub {
391 $current->ready;
392 undef $current;
393 };
394
395 &schedule while $current;
264 } 396 }
397
265 wantarray ? @{$self->{status}} : $self->{status}[0]; 398 wantarray ? @{$self->{status}} : $self->{status}[0];
266} 399}
267 400
401=item $coroutine->on_destroy (\&cb)
402
403Registers a callback that is called when this coroutine gets destroyed,
404but before it is joined. The callback gets passed the terminate arguments,
405if any.
406
407=cut
408
409sub on_destroy {
410 my ($self, $cb) = @_;
411
412 push @{ $self->{destroy_cb} }, $cb;
413}
414
268=item $oldprio = $process->prio($newprio) 415=item $oldprio = $coroutine->prio ($newprio)
269 416
270Sets (or gets, if the argument is missing) the priority of the 417Sets (or gets, if the argument is missing) the priority of the
271process. Higher priority processes get run before lower priority 418coroutine. Higher priority coroutines get run before lower priority
272processes. Priorities are smalled signed integer (currently -4 .. +3), 419coroutines. Priorities are small signed integers (currently -4 .. +3),
273that you can refer to using PRIO_xxx constants (use the import tag :prio 420that you can refer to using PRIO_xxx constants (use the import tag :prio
274to get then): 421to get then):
275 422
276 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 423 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
277 3 > 1 > 0 > -1 > -3 > -4 424 3 > 1 > 0 > -1 > -3 > -4
280 current->prio(PRIO_HIGH); 427 current->prio(PRIO_HIGH);
281 428
282The idle coroutine ($Coro::idle) always has a lower priority than any 429The idle coroutine ($Coro::idle) always has a lower priority than any
283existing coroutine. 430existing coroutine.
284 431
285Changing the priority of the current process will take effect immediately, 432Changing the priority of the current coroutine will take effect immediately,
286but changing the priority of processes in the ready queue (but not 433but changing the priority of coroutines in the ready queue (but not
287running) will only take effect after the next schedule (of that 434running) will only take effect after the next schedule (of that
288process). This is a bug that will be fixed in some future version. 435coroutine). This is a bug that will be fixed in some future version.
289 436
290=cut
291
292sub prio {
293 my $old = $_[0]{prio};
294 $_[0]{prio} = $_[1] if @_ > 1;
295 $old;
296}
297
298=item $newprio = $process->nice($change) 437=item $newprio = $coroutine->nice ($change)
299 438
300Similar to C<prio>, but subtract the given value from the priority (i.e. 439Similar to C<prio>, but subtract the given value from the priority (i.e.
301higher values mean lower priority, just as in unix). 440higher values mean lower priority, just as in unix).
302 441
303=cut
304
305sub nice {
306 $_[0]{prio} -= $_[1];
307}
308
309=item $olddesc = $process->desc($newdesc) 442=item $olddesc = $coroutine->desc ($newdesc)
310 443
311Sets (or gets in case the argument is missing) the description for this 444Sets (or gets in case the argument is missing) the description for this
312process. This is just a free-form string you can associate with a process. 445coroutine. This is just a free-form string you can associate with a coroutine.
313 446
314=cut 447=cut
315 448
316sub desc { 449sub desc {
317 my $old = $_[0]{desc}; 450 my $old = $_[0]{desc};
319 $old; 452 $old;
320} 453}
321 454
322=back 455=back
323 456
457=head2 GLOBAL FUNCTIONS
458
459=over 4
460
461=item Coro::nready
462
463Returns the number of coroutines that are currently in the ready state,
464i.e. that can be swicthed to. The value C<0> means that the only runnable
465coroutine is the currently running one, so C<cede> would have no effect,
466and C<schedule> would cause a deadlock unless there is an idle handler
467that wakes up some coroutines.
468
469=item my $guard = Coro::guard { ... }
470
471This creates and returns a guard object. Nothing happens until the object
472gets destroyed, in which case the codeblock given as argument will be
473executed. This is useful to free locks or other resources in case of a
474runtime error or when the coroutine gets canceled, as in both cases the
475guard block will be executed. The guard object supports only one method,
476C<< ->cancel >>, which will keep the codeblock from being executed.
477
478Example: set some flag and clear it again when the coroutine gets canceled
479or the function returns:
480
481 sub do_something {
482 my $guard = Coro::guard { $busy = 0 };
483 $busy = 1;
484
485 # do something that requires $busy to be true
486 }
487
488=cut
489
490sub guard(&) {
491 bless \(my $cb = $_[0]), "Coro::guard"
492}
493
494sub Coro::guard::cancel {
495 ${$_[0]} = sub { };
496}
497
498sub Coro::guard::DESTROY {
499 ${$_[0]}->();
500}
501
502
503=item unblock_sub { ... }
504
505This utility function takes a BLOCK or code reference and "unblocks" it,
506returning the new coderef. This means that the new coderef will return
507immediately without blocking, returning nothing, while the original code
508ref will be called (with parameters) from within its own coroutine.
509
510The reason this fucntion exists is that many event libraries (such as the
511venerable L<Event|Event> module) are not coroutine-safe (a weaker form
512of thread-safety). This means you must not block within event callbacks,
513otherwise you might suffer from crashes or worse.
514
515This function allows your callbacks to block by executing them in another
516coroutine where it is safe to block. One example where blocking is handy
517is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
518disk.
519
520In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
521creating event callbacks that want to block.
522
523=cut
524
525our @unblock_queue;
526
527# we create a special coro because we want to cede,
528# to reduce pressure on the coro pool (because most callbacks
529# return immediately and can be reused) and because we cannot cede
530# inside an event callback.
531our $unblock_scheduler = async {
532 while () {
533 while (my $cb = pop @unblock_queue) {
534 # this is an inlined copy of async_pool
535 my $coro = (pop @pool or new Coro \&pool_handler);
536
537 $coro->{_invoke} = $cb;
538 $coro->ready;
539 cede; # for short-lived callbacks, this reduces pressure on the coro pool
540 }
541 schedule; # sleep well
542 }
543};
544
545sub unblock_sub(&) {
546 my $cb = shift;
547
548 sub {
549 unshift @unblock_queue, [$cb, @_];
550 $unblock_scheduler->ready;
551 }
552}
553
554=back
555
324=cut 556=cut
325 557
3261; 5581;
327 559
328=head1 BUGS/LIMITATIONS 560=head1 BUGS/LIMITATIONS
329 561
330 - you must make very sure that no coro is still active on global destruction. 562 - you must make very sure that no coro is still active on global
331 very bad things might happen otherwise (usually segfaults). 563 destruction. very bad things might happen otherwise (usually segfaults).
564
332 - this module is not thread-safe. You should only ever use this module from 565 - this module is not thread-safe. You should only ever use this module
333 the same thread (this requirement might be loosened in the future to 566 from the same thread (this requirement might be losened in the future
334 allow per-thread schedulers, but Coro::State does not yet allow this). 567 to allow per-thread schedulers, but Coro::State does not yet allow
568 this).
335 569
336=head1 SEE ALSO 570=head1 SEE ALSO
337 571
338L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 572Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
339L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>, 573
340L<Coro::Handle>, L<Coro::Socket>. 574Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
575
576Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
577
578Embedding: L<Coro:MakeMaker>
341 579
342=head1 AUTHOR 580=head1 AUTHOR
343 581
344 Marc Lehmann <pcg@goof.com> 582 Marc Lehmann <schmorp@schmorp.de>
345 http://www.goof.com/pcg/marc/ 583 http://home.schmorp.de/
346 584
347=cut 585=cut
348 586

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