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Revision 1.133 by root, Fri Sep 21 01:23:58 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 = 0.5; 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<$main> (of course).
93 111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essential you are encouraged to use the
114C<Coro::current> function instead.
115
94=cut 116=cut
117
118$main->{desc} = "[main::]";
95 119
96# maybe some other module used Coro::Specific before... 120# maybe some other module used Coro::Specific before...
97if ($current) {
98 $main->{specific} = $current->{specific}; 121$main->{specific} = $current->{specific}
99} 122 if $current;
100 123
101our $current = $main; 124_set_current $main;
102 125
103sub current() { $current } 126sub current() { $current }
104 127
105=item $idle 128=item $idle
106 129
107The coroutine to switch to when no other coroutine is running. The default 130A callback that is called whenever the scheduler finds no ready coroutines
108implementation prints "FATAL: deadlock detected" and exits. 131to run. The default implementation prints "FATAL: deadlock detected" and
132exits, because the program has no other way to continue.
109 133
110=cut 134This hook is overwritten by modules such as C<Coro::Timer> and
135C<Coro::Event> to wait on an external event that hopefully wake up a
136coroutine so the scheduler can run it.
111 137
112# should be done using priorities :( 138Please note that if your callback recursively invokes perl (e.g. for event
113our $idle = new Coro sub { 139handlers), then it must be prepared to be called recursively.
114 print STDERR "FATAL: deadlock detected\n"; 140
115 exit(51); 141=cut
142
143$idle = sub {
144 require Carp;
145 Carp::croak ("FATAL: deadlock detected");
116}; 146};
147
148sub _cancel {
149 my ($self) = @_;
150
151 # free coroutine data and mark as destructed
152 $self->_destroy
153 or return;
154
155 # call all destruction callbacks
156 $_->(@{$self->{status}})
157 for @{(delete $self->{destroy_cb}) || []};
158}
117 159
118# this coroutine is necessary because a coroutine 160# this coroutine is necessary because a coroutine
119# cannot destroy itself. 161# cannot destroy itself.
120my @destroy; 162my @destroy;
163my $manager;
164
121my $manager = new Coro sub { 165$manager = new Coro sub {
122 while() { 166 while () {
123 delete ((pop @destroy)->{_coro_state}) while @destroy; 167 (shift @destroy)->_cancel
168 while @destroy;
169
124 &schedule; 170 &schedule;
125 } 171 }
126}; 172};
173$manager->desc ("[coro manager]");
174$manager->prio (PRIO_MAX);
127 175
128# static methods. not really. 176# static methods. not really.
129 177
178=back
179
130=head2 STATIC METHODS 180=head2 STATIC METHODS
131 181
132Static methods are actually functions that operate on the current process only. 182Static methods are actually functions that operate on the current coroutine only.
133 183
134=over 4 184=over 4
135 185
136=item async { ... } [@args...] 186=item async { ... } [@args...]
137 187
138Create a new asynchronous process and return it's process object 188Create a new asynchronous coroutine and return it's coroutine object
139(usually unused). When the sub returns the new process is automatically 189(usually unused). When the sub returns the new coroutine is automatically
140terminated. 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.
141 195
142 # create a new coroutine that just prints its arguments 196 # create a new coroutine that just prints its arguments
143 async { 197 async {
144 print "@_\n"; 198 print "@_\n";
145 } 1,2,3,4; 199 } 1,2,3,4;
146 200
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 201=cut
151 202
152sub async(&@) { 203sub async(&@) {
153 my $pid = new Coro @_; 204 my $coro = new Coro @_;
154 $manager->ready; # this ensures that the stack is cloned from the manager
155 $pid->ready; 205 $coro->ready;
156 $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
230{ terminate }> once per second or so to slowly replenish the pool. In
231addition to that, when the stacks used by a handler grows larger than 16kb
232(adjustable with $Coro::MAX_POOL_RSS) it will also exit.
233
234=cut
235
236our $POOL_SIZE = 8;
237our $MAX_POOL_RSS = 16 * 1024;
238our @pool;
239
240sub pool_handler {
241 while () {
242 $current->{desc} = "[async_pool]";
243
244 eval {
245 my ($cb, @arg) = @{ delete $current->{_invoke} or return };
246 $cb->(@arg);
247 };
248 warn $@ if $@;
249
250 last if @pool >= $POOL_SIZE || $current->rss >= $MAX_POOL_RSS;
251
252 push @pool, $current;
253 $current->{desc} = "[async_pool idle]";
254 $current->save (Coro::State::SAVE_DEF);
255 $current->prio (0);
256 schedule;
257 }
258}
259
260sub async_pool(&@) {
261 # this is also inlined into the unlock_scheduler
262 my $coro = (pop @pool) || new Coro \&pool_handler;;
263
264 $coro->{_invoke} = [@_];
265 $coro->ready;
266
267 $coro
157} 268}
158 269
159=item schedule 270=item schedule
160 271
161Calls the scheduler. Please note that the current process will not be put 272Calls the scheduler. Please note that the current coroutine will not be put
162into the ready queue, so calling this function usually means you will 273into the ready queue, so calling this function usually means you will
163never be called again. 274never be called again unless something else (e.g. an event handler) calls
275ready.
164 276
165=cut 277The canonical way to wait on external events is this:
278
279 {
280 # remember current coroutine
281 my $current = $Coro::current;
282
283 # register a hypothetical event handler
284 on_event_invoke sub {
285 # wake up sleeping coroutine
286 $current->ready;
287 undef $current;
288 };
289
290 # call schedule until event occurred.
291 # in case we are woken up for other reasons
292 # (current still defined), loop.
293 Coro::schedule while $current;
294 }
166 295
167=item cede 296=item cede
168 297
169"Cede" to other processes. This function puts the current process into the 298"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 299ready queue and calls C<schedule>, which has the effect of giving up the
171current "timeslice" to other coroutines of the same or higher priority. 300current "timeslice" to other coroutines of the same or higher priority.
172 301
173=cut 302Returns true if at least one coroutine switch has happened.
174 303
304=item Coro::cede_notself
305
306Works like cede, but is not exported by default and will cede to any
307coroutine, regardless of priority, once.
308
309Returns true if at least one coroutine switch has happened.
310
175=item terminate 311=item terminate [arg...]
176 312
177Terminates the current process. 313Terminates the current coroutine with the given status values (see L<cancel>).
178
179Future versions of this function will allow result arguments.
180 314
181=cut 315=cut
182 316
183sub terminate { 317sub terminate {
184 $current->cancel; 318 $current->cancel (@_);
185 &schedule;
186 die; # NORETURN
187} 319}
188 320
189=back 321=back
190 322
191# dynamic methods 323# dynamic methods
192 324
193=head2 PROCESS METHODS 325=head2 COROUTINE METHODS
194 326
195These are the methods you can call on process objects. 327These are the methods you can call on coroutine objects.
196 328
197=over 4 329=over 4
198 330
199=item new Coro \&sub [, @args...] 331=item new Coro \&sub [, @args...]
200 332
201Create a new process and return it. When the sub returns the process 333Create a new coroutine and return it. When the sub returns the coroutine
202automatically terminates. To start the process you must first put it into 334automatically terminates as if C<terminate> with the returned values were
335called. To make the coroutine run you must first put it into the ready queue
203the ready queue by calling the ready method. 336by calling the ready method.
204 337
205The coderef you submit MUST NOT be a closure that refers to variables 338See C<async> for additional discussion.
206in an outer scope. This does NOT work. Pass arguments into it instead.
207 339
208=cut 340=cut
209 341
210sub _newcoro { 342sub _run_coro {
211 terminate &{+shift}; 343 terminate &{+shift};
212} 344}
213 345
214sub new { 346sub new {
215 my $class = shift; 347 my $class = shift;
216 bless {
217 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
218 }, $class;
219}
220 348
221=item $process->ready 349 $class->SUPER::new (\&_run_coro, @_)
350}
222 351
223Put the current process into the ready queue. 352=item $success = $coroutine->ready
224 353
225=cut 354Put the given coroutine into the ready queue (according to it's priority)
355and return true. If the coroutine is already in the ready queue, do nothing
356and return false.
226 357
227=item $process->cancel 358=item $is_ready = $coroutine->is_ready
228 359
229Like C<terminate>, but terminates the specified process instead. 360Return wether the coroutine is currently the ready queue or not,
361
362=item $coroutine->cancel (arg...)
363
364Terminates the given coroutine and makes it return the given arguments as
365status (default: the empty list). Never returns if the coroutine is the
366current coroutine.
230 367
231=cut 368=cut
232 369
233sub cancel { 370sub cancel {
371 my $self = shift;
372 $self->{status} = [@_];
373
374 if ($current == $self) {
234 push @destroy, $_[0]; 375 push @destroy, $self;
235 $manager->ready; 376 $manager->ready;
236 &schedule if $current == $_[0]; 377 &schedule while 1;
378 } else {
379 $self->_cancel;
380 }
237} 381}
238 382
383=item $coroutine->join
384
385Wait until the coroutine terminates and return any values given to the
386C<terminate> or C<cancel> functions. C<join> can be called multiple times
387from multiple coroutine.
388
389=cut
390
391sub join {
392 my $self = shift;
393
394 unless ($self->{status}) {
395 my $current = $current;
396
397 push @{$self->{destroy_cb}}, sub {
398 $current->ready;
399 undef $current;
400 };
401
402 &schedule while $current;
403 }
404
405 wantarray ? @{$self->{status}} : $self->{status}[0];
406}
407
408=item $coroutine->on_destroy (\&cb)
409
410Registers a callback that is called when this coroutine gets destroyed,
411but before it is joined. The callback gets passed the terminate arguments,
412if any.
413
414=cut
415
416sub on_destroy {
417 my ($self, $cb) = @_;
418
419 push @{ $self->{destroy_cb} }, $cb;
420}
421
239=item $oldprio = $process->prio($newprio) 422=item $oldprio = $coroutine->prio ($newprio)
240 423
241Sets the priority of the process. Higher priority processes get run before 424Sets (or gets, if the argument is missing) the priority of the
242lower priority processes. Priorities are smalled signed integer (currently 425coroutine. Higher priority coroutines get run before lower priority
426coroutines. Priorities are small signed integers (currently -4 .. +3),
243-4 .. +3), that you can refer to using PRIO_xxx constants (use the import 427that you can refer to using PRIO_xxx constants (use the import tag :prio
244tag :prio to get then): 428to get then):
245 429
246 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 430 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
247 3 > 1 > 0 > -1 > -3 > -4 431 3 > 1 > 0 > -1 > -3 > -4
248 432
249 # set priority to HIGH 433 # set priority to HIGH
250 current->prio(PRIO_HIGH); 434 current->prio(PRIO_HIGH);
251 435
252The idle coroutine ($Coro::idle) always has a lower priority than any 436The idle coroutine ($Coro::idle) always has a lower priority than any
253existing coroutine. 437existing coroutine.
254 438
255Changing the priority of the current process will take effect immediately, 439Changing the priority of the current coroutine will take effect immediately,
256but changing the priority of processes in the ready queue (but not 440but changing the priority of coroutines in the ready queue (but not
257running) will only take effect after the next schedule (of that 441running) will only take effect after the next schedule (of that
258process). This is a bug that will be fixed in some future version. 442coroutine). This is a bug that will be fixed in some future version.
259 443
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) 444=item $newprio = $coroutine->nice ($change)
269 445
270Similar to C<prio>, but subtract the given value from the priority (i.e. 446Similar to C<prio>, but subtract the given value from the priority (i.e.
271higher values mean lower priority, just as in unix). 447higher values mean lower priority, just as in unix).
272 448
273=cut 449=item $olddesc = $coroutine->desc ($newdesc)
274 450
275sub nice { 451Sets (or gets in case the argument is missing) the description for this
276 $_[0]{prio} -= $_[1]; 452coroutine. This is just a free-form string you can associate with a coroutine.
453
454=cut
455
456sub desc {
457 my $old = $_[0]{desc};
458 $_[0]{desc} = $_[1] if @_ > 1;
459 $old;
277} 460}
278 461
279=back 462=back
280 463
464=head2 GLOBAL FUNCTIONS
465
466=over 4
467
468=item Coro::nready
469
470Returns the number of coroutines that are currently in the ready state,
471i.e. that can be switched to. The value C<0> means that the only runnable
472coroutine is the currently running one, so C<cede> would have no effect,
473and C<schedule> would cause a deadlock unless there is an idle handler
474that wakes up some coroutines.
475
476=item my $guard = Coro::guard { ... }
477
478This creates and returns a guard object. Nothing happens until the object
479gets destroyed, in which case the codeblock given as argument will be
480executed. This is useful to free locks or other resources in case of a
481runtime error or when the coroutine gets canceled, as in both cases the
482guard block will be executed. The guard object supports only one method,
483C<< ->cancel >>, which will keep the codeblock from being executed.
484
485Example: set some flag and clear it again when the coroutine gets canceled
486or the function returns:
487
488 sub do_something {
489 my $guard = Coro::guard { $busy = 0 };
490 $busy = 1;
491
492 # do something that requires $busy to be true
493 }
494
495=cut
496
497sub guard(&) {
498 bless \(my $cb = $_[0]), "Coro::guard"
499}
500
501sub Coro::guard::cancel {
502 ${$_[0]} = sub { };
503}
504
505sub Coro::guard::DESTROY {
506 ${$_[0]}->();
507}
508
509
510=item unblock_sub { ... }
511
512This utility function takes a BLOCK or code reference and "unblocks" it,
513returning the new coderef. This means that the new coderef will return
514immediately without blocking, returning nothing, while the original code
515ref will be called (with parameters) from within its own coroutine.
516
517The reason this function exists is that many event libraries (such as the
518venerable L<Event|Event> module) are not coroutine-safe (a weaker form
519of thread-safety). This means you must not block within event callbacks,
520otherwise you might suffer from crashes or worse.
521
522This function allows your callbacks to block by executing them in another
523coroutine where it is safe to block. One example where blocking is handy
524is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
525disk.
526
527In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
528creating event callbacks that want to block.
529
530=cut
531
532our @unblock_queue;
533
534# we create a special coro because we want to cede,
535# to reduce pressure on the coro pool (because most callbacks
536# return immediately and can be reused) and because we cannot cede
537# inside an event callback.
538our $unblock_scheduler = new Coro sub {
539 while () {
540 while (my $cb = pop @unblock_queue) {
541 # this is an inlined copy of async_pool
542 my $coro = (pop @pool or new Coro \&pool_handler);
543
544 $coro->{_invoke} = $cb;
545 $coro->ready;
546 cede; # for short-lived callbacks, this reduces pressure on the coro pool
547 }
548 schedule; # sleep well
549 }
550};
551$unblock_scheduler->desc ("[unblock_sub scheduler]");
552
553sub unblock_sub(&) {
554 my $cb = shift;
555
556 sub {
557 unshift @unblock_queue, [$cb, @_];
558 $unblock_scheduler->ready;
559 }
560}
561
562=back
563
281=cut 564=cut
282 565
2831; 5661;
284 567
285=head1 BUGS/LIMITATIONS 568=head1 BUGS/LIMITATIONS
286 569
287 - you must make very sure that no coro is still active on global destruction. 570 - you must make very sure that no coro is still active on global
288 very bad things might happen otherwise (usually segfaults). 571 destruction. very bad things might happen otherwise (usually segfaults).
572
289 - this module is not thread-safe. You must only ever use this module from 573 - 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 574 from the same thread (this requirement might be loosened in the future
291 allow per-thread schedulers, but Coro::State does not yet allow this). 575 to allow per-thread schedulers, but Coro::State does not yet allow
576 this).
292 577
293=head1 SEE ALSO 578=head1 SEE ALSO
294 579
295L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 580Support/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>, 581
297L<Coro::Handle>, L<Coro::Socket>. 582Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
583
584Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
585
586Embedding: L<Coro:MakeMaker>
298 587
299=head1 AUTHOR 588=head1 AUTHOR
300 589
301 Marc Lehmann <pcg@goof.com> 590 Marc Lehmann <schmorp@schmorp.de>
302 http://www.goof.com/pcg/marc/ 591 http://home.schmorp.de/
303 592
304=cut 593=cut
305 594

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