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Revision 1.39 by root, Tue Oct 9 00:39:08 2001 UTC vs.
Revision 1.134 by root, Sat Sep 22 14:42:56 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<$main> (of course).
93 111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essential you are encouraged to use the
114C<Coro::current> function instead.
115
94=cut 116=cut
117
118$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;
121my $manager; 163my $manager;
164
122$manager = new Coro sub { 165$manager = new Coro sub {
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 168 while @destroy;
126 # been readied multiple times. this is harmless since the manager 169
127 # can be called as many times as neccessary and will always
128 # remove itself from the runqueue
129 (pop @destroy)->{_coro_state} = $manager->{_coro_state} while @destroy;
130 &schedule; 170 &schedule;
131 } 171 }
132}; 172};
173$manager->desc ("[coro manager]");
174$manager->prio (PRIO_MAX);
133 175
134# static methods. not really. 176# static methods. not really.
135 177
178=back
179
136=head2 STATIC METHODS 180=head2 STATIC METHODS
137 181
138Static methods are actually functions that operate on the current process only. 182Static methods are actually functions that operate on the current coroutine only.
139 183
140=over 4 184=over 4
141 185
142=item async { ... } [@args...] 186=item async { ... } [@args...]
143 187
144Create a new asynchronous process and return it's process object 188Create a new asynchronous coroutine and return it's coroutine object
145(usually unused). When the sub returns the new process is automatically 189(usually unused). When the sub returns the new coroutine is automatically
146terminated. 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.
147 195
148 # create a new coroutine that just prints its arguments 196 # create a new coroutine that just prints its arguments
149 async { 197 async {
150 print "@_\n"; 198 print "@_\n";
151 } 1,2,3,4; 199 } 1,2,3,4;
152 200
153The coderef you submit MUST NOT be a closure that refers to variables
154in an outer scope. This does NOT work. Pass arguments into it instead.
155
156=cut 201=cut
157 202
158sub async(&@) { 203sub async(&@) {
159 my $pid = new Coro @_; 204 my $coro = new Coro @_;
160 $manager->ready; # this ensures that the stack is cloned from the manager
161 $pid->ready; 205 $coro->ready;
162 $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::POOL_RSS) it will also exit.
233
234=cut
235
236our $POOL_SIZE = 8;
237our $POOL_RSS = 16 * 1024;
238our @async_pool;
239
240sub pool_handler {
241 my $cb;
242
243 while () {
244 eval {
245 while () {
246 $cb = &_pool_1
247 or return;
248
249 &$cb;
250
251 return if &_pool_2;
252
253 undef $cb;
254 schedule;
255 }
256 };
257
258 warn $@ if $@;
259 }
260}
261
262sub async_pool(&@) {
263 # this is also inlined into the unlock_scheduler
264 my $coro = (pop @async_pool) || new Coro \&pool_handler;;
265
266 $coro->{_invoke} = [@_];
267 $coro->ready;
268
269 $coro
163} 270}
164 271
165=item schedule 272=item schedule
166 273
167Calls the scheduler. Please note that the current process will not be put 274Calls the scheduler. Please note that the current coroutine will not be put
168into the ready queue, so calling this function usually means you will 275into the ready queue, so calling this function usually means you will
169never be called again. 276never be called again unless something else (e.g. an event handler) calls
277ready.
170 278
171=cut 279The canonical way to wait on external events is this:
280
281 {
282 # remember current coroutine
283 my $current = $Coro::current;
284
285 # register a hypothetical event handler
286 on_event_invoke sub {
287 # wake up sleeping coroutine
288 $current->ready;
289 undef $current;
290 };
291
292 # call schedule until event occurred.
293 # in case we are woken up for other reasons
294 # (current still defined), loop.
295 Coro::schedule while $current;
296 }
172 297
173=item cede 298=item cede
174 299
175"Cede" to other processes. This function puts the current process into the 300"Cede" to other coroutines. This function puts the current coroutine into the
176ready queue and calls C<schedule>, which has the effect of giving up the 301ready queue and calls C<schedule>, which has the effect of giving up the
177current "timeslice" to other coroutines of the same or higher priority. 302current "timeslice" to other coroutines of the same or higher priority.
178 303
179=cut 304Returns true if at least one coroutine switch has happened.
180 305
306=item Coro::cede_notself
307
308Works like cede, but is not exported by default and will cede to any
309coroutine, regardless of priority, once.
310
311Returns true if at least one coroutine switch has happened.
312
181=item terminate 313=item terminate [arg...]
182 314
183Terminates the current process. 315Terminates the current coroutine with the given status values (see L<cancel>).
184
185Future versions of this function will allow result arguments.
186 316
187=cut 317=cut
188 318
189sub terminate { 319sub terminate {
190 $current->cancel; 320 $current->cancel (@_);
191 &schedule;
192 die; # NORETURN
193} 321}
194 322
195=back 323=back
196 324
197# dynamic methods 325# dynamic methods
198 326
199=head2 PROCESS METHODS 327=head2 COROUTINE METHODS
200 328
201These are the methods you can call on process objects. 329These are the methods you can call on coroutine objects.
202 330
203=over 4 331=over 4
204 332
205=item new Coro \&sub [, @args...] 333=item new Coro \&sub [, @args...]
206 334
207Create a new process and return it. When the sub returns the process 335Create a new coroutine and return it. When the sub returns the coroutine
208automatically terminates. To start the process you must first put it into 336automatically terminates as if C<terminate> with the returned values were
337called. To make the coroutine run you must first put it into the ready queue
209the ready queue by calling the ready method. 338by calling the ready method.
210 339
211The coderef you submit MUST NOT be a closure that refers to variables 340See C<async> for additional discussion.
212in an outer scope. This does NOT work. Pass arguments into it instead.
213 341
214=cut 342=cut
215 343
216sub _newcoro { 344sub _run_coro {
217 terminate &{+shift}; 345 terminate &{+shift};
218} 346}
219 347
220sub new { 348sub new {
221 my $class = shift; 349 my $class = shift;
222 bless {
223 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
224 }, $class;
225}
226 350
227=item $process->ready 351 $class->SUPER::new (\&_run_coro, @_)
352}
228 353
229Put the given process into the ready queue. 354=item $success = $coroutine->ready
230 355
231=cut 356Put the given coroutine into the ready queue (according to it's priority)
357and return true. If the coroutine is already in the ready queue, do nothing
358and return false.
232 359
233=item $process->cancel 360=item $is_ready = $coroutine->is_ready
234 361
235Like C<terminate>, but terminates the specified process instead. 362Return wether the coroutine is currently the ready queue or not,
363
364=item $coroutine->cancel (arg...)
365
366Terminates the given coroutine and makes it return the given arguments as
367status (default: the empty list). Never returns if the coroutine is the
368current coroutine.
236 369
237=cut 370=cut
238 371
239sub cancel { 372sub cancel {
373 my $self = shift;
374 $self->{status} = [@_];
375
376 if ($current == $self) {
240 push @destroy, $_[0]; 377 push @destroy, $self;
241 $manager->ready; 378 $manager->ready;
242 &schedule if $current == $_[0]; 379 &schedule while 1;
380 } else {
381 $self->_cancel;
382 }
243} 383}
244 384
385=item $coroutine->join
386
387Wait until the coroutine terminates and return any values given to the
388C<terminate> or C<cancel> functions. C<join> can be called multiple times
389from multiple coroutine.
390
391=cut
392
393sub join {
394 my $self = shift;
395
396 unless ($self->{status}) {
397 my $current = $current;
398
399 push @{$self->{destroy_cb}}, sub {
400 $current->ready;
401 undef $current;
402 };
403
404 &schedule while $current;
405 }
406
407 wantarray ? @{$self->{status}} : $self->{status}[0];
408}
409
410=item $coroutine->on_destroy (\&cb)
411
412Registers a callback that is called when this coroutine gets destroyed,
413but before it is joined. The callback gets passed the terminate arguments,
414if any.
415
416=cut
417
418sub on_destroy {
419 my ($self, $cb) = @_;
420
421 push @{ $self->{destroy_cb} }, $cb;
422}
423
245=item $oldprio = $process->prio($newprio) 424=item $oldprio = $coroutine->prio ($newprio)
246 425
247Sets the priority of the process. Higher priority processes get run before 426Sets (or gets, if the argument is missing) the priority of the
248lower priority processes. Priorities are smalled signed integer (currently 427coroutine. Higher priority coroutines get run before lower priority
428coroutines. Priorities are small signed integers (currently -4 .. +3),
249-4 .. +3), that you can refer to using PRIO_xxx constants (use the import 429that you can refer to using PRIO_xxx constants (use the import tag :prio
250tag :prio to get then): 430to get then):
251 431
252 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 432 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
253 3 > 1 > 0 > -1 > -3 > -4 433 3 > 1 > 0 > -1 > -3 > -4
254 434
255 # set priority to HIGH 435 # set priority to HIGH
256 current->prio(PRIO_HIGH); 436 current->prio(PRIO_HIGH);
257 437
258The idle coroutine ($Coro::idle) always has a lower priority than any 438The idle coroutine ($Coro::idle) always has a lower priority than any
259existing coroutine. 439existing coroutine.
260 440
261Changing the priority of the current process will take effect immediately, 441Changing the priority of the current coroutine will take effect immediately,
262but changing the priority of processes in the ready queue (but not 442but changing the priority of coroutines in the ready queue (but not
263running) will only take effect after the next schedule (of that 443running) will only take effect after the next schedule (of that
264process). This is a bug that will be fixed in some future version. 444coroutine). This is a bug that will be fixed in some future version.
265 445
266=cut
267
268sub prio {
269 my $old = $_[0]{prio};
270 $_[0]{prio} = $_[1] if @_ > 1;
271 $old;
272}
273
274=item $newprio = $process->nice($change) 446=item $newprio = $coroutine->nice ($change)
275 447
276Similar to C<prio>, but subtract the given value from the priority (i.e. 448Similar to C<prio>, but subtract the given value from the priority (i.e.
277higher values mean lower priority, just as in unix). 449higher values mean lower priority, just as in unix).
278 450
279=cut 451=item $olddesc = $coroutine->desc ($newdesc)
280 452
281sub nice { 453Sets (or gets in case the argument is missing) the description for this
282 $_[0]{prio} -= $_[1]; 454coroutine. This is just a free-form string you can associate with a coroutine.
455
456=cut
457
458sub desc {
459 my $old = $_[0]{desc};
460 $_[0]{desc} = $_[1] if @_ > 1;
461 $old;
283} 462}
284 463
285=back 464=back
286 465
466=head2 GLOBAL FUNCTIONS
467
468=over 4
469
470=item Coro::nready
471
472Returns the number of coroutines that are currently in the ready state,
473i.e. that can be switched to. The value C<0> means that the only runnable
474coroutine is the currently running one, so C<cede> would have no effect,
475and C<schedule> would cause a deadlock unless there is an idle handler
476that wakes up some coroutines.
477
478=item my $guard = Coro::guard { ... }
479
480This creates and returns a guard object. Nothing happens until the object
481gets destroyed, in which case the codeblock given as argument will be
482executed. This is useful to free locks or other resources in case of a
483runtime error or when the coroutine gets canceled, as in both cases the
484guard block will be executed. The guard object supports only one method,
485C<< ->cancel >>, which will keep the codeblock from being executed.
486
487Example: set some flag and clear it again when the coroutine gets canceled
488or the function returns:
489
490 sub do_something {
491 my $guard = Coro::guard { $busy = 0 };
492 $busy = 1;
493
494 # do something that requires $busy to be true
495 }
496
497=cut
498
499sub guard(&) {
500 bless \(my $cb = $_[0]), "Coro::guard"
501}
502
503sub Coro::guard::cancel {
504 ${$_[0]} = sub { };
505}
506
507sub Coro::guard::DESTROY {
508 ${$_[0]}->();
509}
510
511
512=item unblock_sub { ... }
513
514This utility function takes a BLOCK or code reference and "unblocks" it,
515returning the new coderef. This means that the new coderef will return
516immediately without blocking, returning nothing, while the original code
517ref will be called (with parameters) from within its own coroutine.
518
519The reason this function exists is that many event libraries (such as the
520venerable L<Event|Event> module) are not coroutine-safe (a weaker form
521of thread-safety). This means you must not block within event callbacks,
522otherwise you might suffer from crashes or worse.
523
524This function allows your callbacks to block by executing them in another
525coroutine where it is safe to block. One example where blocking is handy
526is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
527disk.
528
529In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
530creating event callbacks that want to block.
531
532=cut
533
534our @unblock_queue;
535
536# we create a special coro because we want to cede,
537# to reduce pressure on the coro pool (because most callbacks
538# return immediately and can be reused) and because we cannot cede
539# inside an event callback.
540our $unblock_scheduler = new Coro sub {
541 while () {
542 while (my $cb = pop @unblock_queue) {
543 # this is an inlined copy of async_pool
544 my $coro = (pop @async_pool) || new Coro \&pool_handler;
545
546 $coro->{_invoke} = $cb;
547 $coro->ready;
548 cede; # for short-lived callbacks, this reduces pressure on the coro pool
549 }
550 schedule; # sleep well
551 }
552};
553$unblock_scheduler->desc ("[unblock_sub scheduler]");
554
555sub unblock_sub(&) {
556 my $cb = shift;
557
558 sub {
559 unshift @unblock_queue, [$cb, @_];
560 $unblock_scheduler->ready;
561 }
562}
563
564=back
565
287=cut 566=cut
288 567
2891; 5681;
290 569
291=head1 BUGS/LIMITATIONS 570=head1 BUGS/LIMITATIONS
292 571
293 - you must make very sure that no coro is still active on global destruction. 572 - you must make very sure that no coro is still active on global
294 very bad things might happen otherwise (usually segfaults). 573 destruction. very bad things might happen otherwise (usually segfaults).
574
295 - this module is not thread-safe. You must only ever use this module from 575 - this module is not thread-safe. You should only ever use this module
296 the same thread (this requirement might be loosened in the future to 576 from the same thread (this requirement might be loosened in the future
297 allow per-thread schedulers, but Coro::State does not yet allow this). 577 to allow per-thread schedulers, but Coro::State does not yet allow
578 this).
298 579
299=head1 SEE ALSO 580=head1 SEE ALSO
300 581
301L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 582Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
302L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>, 583
303L<Coro::Handle>, L<Coro::Socket>. 584Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
585
586Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
587
588Embedding: L<Coro:MakeMaker>
304 589
305=head1 AUTHOR 590=head1 AUTHOR
306 591
307 Marc Lehmann <pcg@goof.com> 592 Marc Lehmann <schmorp@schmorp.de>
308 http://www.goof.com/pcg/marc/ 593 http://home.schmorp.de/
309 594
310=cut 595=cut
311 596

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