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Revision 1.40 by root, Sun Oct 28 17:00:05 2001 UTC vs.
Revision 1.129 by root, Wed Sep 19 22:33:08 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 used in this module also
26guarantees 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@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
30callchain, it's own set of lexicals and it's own set of perl's most 37its own set of lexicals and its own set of perls most important global
31important global variables. 38variables.
32 39
33=cut 40=cut
34 41
35package Coro; 42package Coro;
36 43
44use strict;
37no warnings qw(uninitialized); 45no warnings "uninitialized";
38 46
39use Coro::State; 47use Coro::State;
40 48
41use base Exporter; 49use base qw(Coro::State Exporter);
42 50
43$VERSION = 0.51; 51our $idle; # idle handler
52our $main; # main coroutine
53our $current; # current coroutine
44 54
55our $VERSION = '3.7';
56
45@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
46%EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
47 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48); 60);
49@EXPORT_OK = @{$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<$main> (of course).
111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essential you are encouraged to use the
114C<Coro::current> function instead.
93 115
94=cut 116=cut
95 117
96# maybe some other module used Coro::Specific before... 118# maybe some other module used Coro::Specific before...
97if ($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 {
164 $current->desc ("[coro manager]");
165
123 while() { 166 while () {
124 # by overwriting the state object with the manager we destroy it 167 (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) { 168 while @destroy;
130 my $coro = pop @destroy; 169
131 $coro->{status} ||= [];
132 $_->ready for @{delete $coro->{join} || []};
133 $coro->{_coro_state} = $manager->{_coro_state};
134 }
135 &schedule; 170 &schedule;
136 } 171 }
137}; 172};
138 173
174$manager->prio (PRIO_MAX);
175
139# static methods. not really. 176# static methods. not really.
140 177
178=back
179
141=head2 STATIC METHODS 180=head2 STATIC METHODS
142 181
143Static methods are actually functions that operate on the current process only. 182Static methods are actually functions that operate on the current coroutine only.
144 183
145=over 4 184=over 4
146 185
147=item async { ... } [@args...] 186=item async { ... } [@args...]
148 187
149Create a new asynchronous process and return it's process object 188Create a new asynchronous coroutine and return it's coroutine object
150(usually unused). When the sub returns the new process is automatically 189(usually unused). When the sub returns the new coroutine is automatically
151terminated. 190terminated.
191
192Calling C<exit> in a coroutine will do the same as calling exit outside
193the coroutine. Likewise, when the coroutine dies, the program will exit,
194just as it would in the main program.
152 195
153 # create a new coroutine that just prints its arguments 196 # create a new coroutine that just prints its arguments
154 async { 197 async {
155 print "@_\n"; 198 print "@_\n";
156 } 1,2,3,4; 199 } 1,2,3,4;
157 200
158The coderef you submit MUST NOT be a closure that refers to variables
159in an outer scope. This does NOT work. Pass arguments into it instead.
160
161=cut 201=cut
162 202
163sub async(&@) { 203sub async(&@) {
164 my $pid = new Coro @_; 204 my $coro = new Coro @_;
165 $manager->ready; # this ensures that the stack is cloned from the manager
166 $pid->ready; 205 $coro->ready;
167 $pid; 206 $coro
207}
208
209=item async_pool { ... } [@args...]
210
211Similar to C<async>, but uses a coroutine pool, so you should not call
212terminate or join (although you are allowed to), and you get a coroutine
213that might have executed other code already (which can be good or bad :).
214
215Also, the block is executed in an C<eval> context and a warning will be
216issued in case of an exception instead of terminating the program, as
217C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
218will not work in the expected way, unless you call terminate or cancel,
219which somehow defeats the purpose of pooling.
220
221The priority will be reset to C<0> after each job, otherwise the coroutine
222will be re-used "as-is".
223
224The pool size is limited to 8 idle coroutines (this can be adjusted by
225changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
226required.
227
228If you are concerned about pooled coroutines growing a lot because a
229single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {
230terminate }> once per second or so to slowly replenish the pool.
231
232=cut
233
234our $POOL_SIZE = 8;
235our @pool;
236
237sub pool_handler {
238 while () {
239 $current->{desc} = "[async_pool]";
240
241 eval {
242 my ($cb, @arg) = @{ delete $current->{_invoke} or return };
243 $cb->(@arg);
244 };
245 warn $@ if $@;
246
247 last if @pool >= $POOL_SIZE;
248
249 push @pool, $current;
250 $current->{desc} = "[async_pool idle]";
251 $current->save (Coro::State::SAVE_DEF);
252 $current->prio (0);
253 schedule;
254 }
255}
256
257sub async_pool(&@) {
258 # this is also inlined into the unlock_scheduler
259 my $coro = (pop @pool) || new Coro \&pool_handler;;
260
261 $coro->{_invoke} = [@_];
262 $coro->ready;
263
264 $coro
168} 265}
169 266
170=item schedule 267=item schedule
171 268
172Calls the scheduler. Please note that the current process will not be put 269Calls the scheduler. Please note that the current coroutine will not be put
173into the ready queue, so calling this function usually means you will 270into the ready queue, so calling this function usually means you will
174never be called again. 271never be called again unless something else (e.g. an event handler) calls
272ready.
175 273
176=cut 274The canonical way to wait on external events is this:
275
276 {
277 # remember current coroutine
278 my $current = $Coro::current;
279
280 # register a hypothetical event handler
281 on_event_invoke sub {
282 # wake up sleeping coroutine
283 $current->ready;
284 undef $current;
285 };
286
287 # call schedule until event occurred.
288 # in case we are woken up for other reasons
289 # (current still defined), loop.
290 Coro::schedule while $current;
291 }
177 292
178=item cede 293=item cede
179 294
180"Cede" to other processes. This function puts the current process into the 295"Cede" to other coroutines. This function puts the current coroutine into the
181ready queue and calls C<schedule>, which has the effect of giving up the 296ready queue and calls C<schedule>, which has the effect of giving up the
182current "timeslice" to other coroutines of the same or higher priority. 297current "timeslice" to other coroutines of the same or higher priority.
183 298
184=cut 299Returns true if at least one coroutine switch has happened.
300
301=item Coro::cede_notself
302
303Works like cede, but is not exported by default and will cede to any
304coroutine, regardless of priority, once.
305
306Returns true if at least one coroutine switch has happened.
185 307
186=item terminate [arg...] 308=item terminate [arg...]
187 309
188Terminates the current process. 310Terminates the current coroutine with the given status values (see L<cancel>).
189
190Future versions of this function will allow result arguments.
191 311
192=cut 312=cut
193 313
194sub terminate { 314sub terminate {
195 $current->{status} = [@_];
196 $current->cancel; 315 $current->cancel (@_);
197 &schedule;
198 die; # NORETURN
199} 316}
200 317
201=back 318=back
202 319
203# dynamic methods 320# dynamic methods
204 321
205=head2 PROCESS METHODS 322=head2 COROUTINE METHODS
206 323
207These are the methods you can call on process objects. 324These are the methods you can call on coroutine objects.
208 325
209=over 4 326=over 4
210 327
211=item new Coro \&sub [, @args...] 328=item new Coro \&sub [, @args...]
212 329
213Create a new process and return it. When the sub returns the process 330Create a new coroutine and return it. When the sub returns the coroutine
214automatically terminates as if C<terminate> with the returned values were 331automatically terminates as if C<terminate> with the returned values were
215called. To start the process you must first put it into the ready queue by 332called. To make the coroutine run you must first put it into the ready queue
216calling the ready method. 333by calling the ready method.
217 334
218The coderef you submit MUST NOT be a closure that refers to variables 335See C<async> for additional discussion.
219in an outer scope. This does NOT work. Pass arguments into it instead.
220 336
221=cut 337=cut
222 338
223sub _newcoro { 339sub _run_coro {
224 terminate &{+shift}; 340 terminate &{+shift};
225} 341}
226 342
227sub new { 343sub new {
228 my $class = shift; 344 my $class = shift;
229 bless {
230 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
231 }, $class;
232}
233 345
234=item $process->ready 346 $class->SUPER::new (\&_run_coro, @_)
347}
235 348
236Put the given process into the ready queue. 349=item $success = $coroutine->ready
237 350
238=cut 351Put the given coroutine into the ready queue (according to it's priority)
352and return true. If the coroutine is already in the ready queue, do nothing
353and return false.
239 354
240=item $process->cancel 355=item $is_ready = $coroutine->is_ready
241 356
242Like C<terminate>, but terminates the specified process instead. 357Return wether the coroutine is currently the ready queue or not,
358
359=item $coroutine->cancel (arg...)
360
361Terminates the given coroutine and makes it return the given arguments as
362status (default: the empty list). Never returns if the coroutine is the
363current coroutine.
243 364
244=cut 365=cut
245 366
246sub cancel { 367sub cancel {
368 my $self = shift;
369 $self->{status} = [@_];
370
371 if ($current == $self) {
247 push @destroy, $_[0]; 372 push @destroy, $self;
248 $manager->ready; 373 $manager->ready;
249 &schedule if $current == $_[0]; 374 &schedule while 1;
375 } else {
376 $self->_cancel;
377 }
250} 378}
251 379
252=item $process->join 380=item $coroutine->join
253 381
254Wait until the coroutine terminates and return any values given to the 382Wait until the coroutine terminates and return any values given to the
255C<terminate> function. C<join> can be called multiple times from multiple 383C<terminate> or C<cancel> functions. C<join> can be called multiple times
256processes. 384from multiple coroutine.
257 385
258=cut 386=cut
259 387
260sub join { 388sub join {
261 my $self = shift; 389 my $self = shift;
390
262 unless ($self->{status}) { 391 unless ($self->{status}) {
263 push @{$self->{join}}, $current; 392 my $current = $current;
264 &schedule; 393
394 push @{$self->{destroy_cb}}, sub {
395 $current->ready;
396 undef $current;
397 };
398
399 &schedule while $current;
265 } 400 }
401
266 wantarray ? @{$self->{status}} : $self->{status}[0]; 402 wantarray ? @{$self->{status}} : $self->{status}[0];
267} 403}
268 404
405=item $coroutine->on_destroy (\&cb)
406
407Registers a callback that is called when this coroutine gets destroyed,
408but before it is joined. The callback gets passed the terminate arguments,
409if any.
410
411=cut
412
413sub on_destroy {
414 my ($self, $cb) = @_;
415
416 push @{ $self->{destroy_cb} }, $cb;
417}
418
269=item $oldprio = $process->prio($newprio) 419=item $oldprio = $coroutine->prio ($newprio)
270 420
271Sets the priority of the process. Higher priority processes get run before 421Sets (or gets, if the argument is missing) the priority of the
272lower priority processes. Priorities are smalled signed integer (currently 422coroutine. Higher priority coroutines get run before lower priority
423coroutines. Priorities are small signed integers (currently -4 .. +3),
273-4 .. +3), that you can refer to using PRIO_xxx constants (use the import 424that you can refer to using PRIO_xxx constants (use the import tag :prio
274tag :prio to get then): 425to get then):
275 426
276 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 427 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
277 3 > 1 > 0 > -1 > -3 > -4 428 3 > 1 > 0 > -1 > -3 > -4
278 429
279 # set priority to HIGH 430 # set priority to HIGH
280 current->prio(PRIO_HIGH); 431 current->prio(PRIO_HIGH);
281 432
282The idle coroutine ($Coro::idle) always has a lower priority than any 433The idle coroutine ($Coro::idle) always has a lower priority than any
283existing coroutine. 434existing coroutine.
284 435
285Changing the priority of the current process will take effect immediately, 436Changing the priority of the current coroutine will take effect immediately,
286but changing the priority of processes in the ready queue (but not 437but changing the priority of coroutines in the ready queue (but not
287running) will only take effect after the next schedule (of that 438running) will only take effect after the next schedule (of that
288process). This is a bug that will be fixed in some future version. 439coroutine). This is a bug that will be fixed in some future version.
289 440
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) 441=item $newprio = $coroutine->nice ($change)
299 442
300Similar to C<prio>, but subtract the given value from the priority (i.e. 443Similar to C<prio>, but subtract the given value from the priority (i.e.
301higher values mean lower priority, just as in unix). 444higher values mean lower priority, just as in unix).
302 445
303=cut 446=item $olddesc = $coroutine->desc ($newdesc)
304 447
305sub nice { 448Sets (or gets in case the argument is missing) the description for this
306 $_[0]{prio} -= $_[1]; 449coroutine. This is just a free-form string you can associate with a coroutine.
450
451=cut
452
453sub desc {
454 my $old = $_[0]{desc};
455 $_[0]{desc} = $_[1] if @_ > 1;
456 $old;
307} 457}
308 458
309=back 459=back
310 460
461=head2 GLOBAL FUNCTIONS
462
463=over 4
464
465=item Coro::nready
466
467Returns the number of coroutines that are currently in the ready state,
468i.e. that can be switched to. The value C<0> means that the only runnable
469coroutine is the currently running one, so C<cede> would have no effect,
470and C<schedule> would cause a deadlock unless there is an idle handler
471that wakes up some coroutines.
472
473=item my $guard = Coro::guard { ... }
474
475This creates and returns a guard object. Nothing happens until the object
476gets destroyed, in which case the codeblock given as argument will be
477executed. This is useful to free locks or other resources in case of a
478runtime error or when the coroutine gets canceled, as in both cases the
479guard block will be executed. The guard object supports only one method,
480C<< ->cancel >>, which will keep the codeblock from being executed.
481
482Example: set some flag and clear it again when the coroutine gets canceled
483or the function returns:
484
485 sub do_something {
486 my $guard = Coro::guard { $busy = 0 };
487 $busy = 1;
488
489 # do something that requires $busy to be true
490 }
491
492=cut
493
494sub guard(&) {
495 bless \(my $cb = $_[0]), "Coro::guard"
496}
497
498sub Coro::guard::cancel {
499 ${$_[0]} = sub { };
500}
501
502sub Coro::guard::DESTROY {
503 ${$_[0]}->();
504}
505
506
507=item unblock_sub { ... }
508
509This utility function takes a BLOCK or code reference and "unblocks" it,
510returning the new coderef. This means that the new coderef will return
511immediately without blocking, returning nothing, while the original code
512ref will be called (with parameters) from within its own coroutine.
513
514The reason this function exists is that many event libraries (such as the
515venerable L<Event|Event> module) are not coroutine-safe (a weaker form
516of thread-safety). This means you must not block within event callbacks,
517otherwise you might suffer from crashes or worse.
518
519This function allows your callbacks to block by executing them in another
520coroutine where it is safe to block. One example where blocking is handy
521is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
522disk.
523
524In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
525creating event callbacks that want to block.
526
527=cut
528
529our @unblock_queue;
530
531# we create a special coro because we want to cede,
532# to reduce pressure on the coro pool (because most callbacks
533# return immediately and can be reused) and because we cannot cede
534# inside an event callback.
535our $unblock_scheduler = async {
536 $current->desc ("[unblock_sub scheduler]");
537 while () {
538 while (my $cb = pop @unblock_queue) {
539 # this is an inlined copy of async_pool
540 my $coro = (pop @pool or new Coro \&pool_handler);
541
542 $coro->{_invoke} = $cb;
543 $coro->ready;
544 cede; # for short-lived callbacks, this reduces pressure on the coro pool
545 }
546 schedule; # sleep well
547 }
548};
549
550sub unblock_sub(&) {
551 my $cb = shift;
552
553 sub {
554 unshift @unblock_queue, [$cb, @_];
555 $unblock_scheduler->ready;
556 }
557}
558
559=back
560
311=cut 561=cut
312 562
3131; 5631;
314 564
315=head1 BUGS/LIMITATIONS 565=head1 BUGS/LIMITATIONS
316 566
317 - you must make very sure that no coro is still active on global destruction. 567 - you must make very sure that no coro is still active on global
318 very bad things might happen otherwise (usually segfaults). 568 destruction. very bad things might happen otherwise (usually segfaults).
569
319 - this module is not thread-safe. You must only ever use this module from 570 - this module is not thread-safe. You should only ever use this module
320 the same thread (this requirement might be loosened in the future to 571 from the same thread (this requirement might be loosened in the future
321 allow per-thread schedulers, but Coro::State does not yet allow this). 572 to allow per-thread schedulers, but Coro::State does not yet allow
573 this).
322 574
323=head1 SEE ALSO 575=head1 SEE ALSO
324 576
325L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 577Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
326L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>, 578
327L<Coro::Handle>, L<Coro::Socket>. 579Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
580
581Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
582
583Embedding: L<Coro:MakeMaker>
328 584
329=head1 AUTHOR 585=head1 AUTHOR
330 586
331 Marc Lehmann <pcg@goof.com> 587 Marc Lehmann <schmorp@schmorp.de>
332 http://www.goof.com/pcg/marc/ 588 http://home.schmorp.de/
333 589
334=cut 590=cut
335 591

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