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Revision 1.42 by root, Tue Nov 6 20:37:20 2001 UTC vs.
Revision 1.107 by root, Fri Jan 5 18:25:51 2007 UTC

8 8
9 async { 9 async {
10 # some asynchronous thread of execution 10 # some asynchronous thread of execution
11 }; 11 };
12 12
13 # alternatively create an async process like this: 13 # alternatively create an async coroutine like this:
14 14
15 sub some_func : Coro { 15 sub some_func : Coro {
16 # some more async code 16 # some more async code
17 } 17 }
18 18
19 cede; 19 cede;
20 20
21=head1 DESCRIPTION 21=head1 DESCRIPTION
22 22
23This module collection manages coroutines. Coroutines are similar to 23This module collection manages coroutines. Coroutines are similar
24threads but don't run in parallel. 24to threads but don't run in parallel at the same time even on SMP
25machines. The specific flavor of coroutine use din this module also
26guarentees you that it will not switch between coroutines unless
27necessary, at easily-identified points in your program, so locking and
28parallel access are rarely an issue, making coroutine programming much
29safer than threads programming.
25 30
31(Perl, however, does not natively support real threads but instead does a
32very slow and memory-intensive emulation of processes using threads. This
33is a performance win on Windows machines, and a loss everywhere else).
34
26In this module, coroutines are defined as "callchain + lexical variables 35In this module, coroutines are defined as "callchain + lexical variables +
27+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own 36@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
28callchain, it's own set of lexicals and it's own set of perl's most 37its own set of lexicals and its own set of perls most important global
29important global variables. 38variables.
30 39
31=cut 40=cut
32 41
33package Coro; 42package Coro;
34 43
44use strict;
35no warnings qw(uninitialized); 45no warnings "uninitialized";
36 46
37use Coro::State; 47use Coro::State;
38 48
39use base Exporter; 49use base qw(Coro::State Exporter);
40 50
41$VERSION = 0.52; 51our $idle; # idle handler
52our $main; # main coroutine
53our $current; # current coroutine
42 54
55our $VERSION = '3.3';
56
43@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
44%EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
45 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
46); 60);
47@EXPORT_OK = @{$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 (@_) {
75 }; 92 };
76 } 93 }
77 94
78} 95}
79 96
97=over 4
98
80=item $main 99=item $main
81 100
82This coroutine represents the main program. 101This coroutine represents the main program.
83 102
84=cut 103=cut
85 104
86our $main = new Coro; 105$main = new Coro;
87 106
88=item $current (or as function: current) 107=item $current (or as function: current)
89 108
90The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). 109The current coroutine (the last coroutine switched to). The initial value
110is C<$main> (of course).
111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essentiel you are encouraged to use the
114C<Coro::current> function instead.
91 115
92=cut 116=cut
93 117
94# maybe some other module used Coro::Specific before... 118# maybe some other module used Coro::Specific before...
95if ($current) {
96 $main->{specific} = $current->{specific}; 119$main->{specific} = $current->{specific}
97} 120 if $current;
98 121
99our $current = $main; 122_set_current $main;
100 123
101sub current() { $current } 124sub current() { $current }
102 125
103=item $idle 126=item $idle
104 127
105The coroutine to switch to when no other coroutine is running. The default 128A callback that is called whenever the scheduler finds no ready coroutines
106implementation 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.
107 131
108=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.
109 135
110# should be done using priorities :( 136Please note that if your callback recursively invokes perl (e.g. for event
111our $idle = new Coro sub { 137handlers), then it must be prepared to be called recursively.
112 print STDERR "FATAL: deadlock detected\n"; 138
113 exit(51); 139=cut
140
141$idle = sub {
142 require Carp;
143 Carp::croak ("FATAL: deadlock detected");
114}; 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}
115 157
116# this coroutine is necessary because a coroutine 158# this coroutine is necessary because a coroutine
117# cannot destroy itself. 159# cannot destroy itself.
118my @destroy; 160my @destroy;
119my $manager; 161my $manager;
162
120$manager = new Coro sub { 163$manager = new Coro sub {
121 while() { 164 while () {
122 # by overwriting the state object with the manager we destroy it 165 (shift @destroy)->_cancel
123 # while still being able to schedule this coroutine (in case it has
124 # been readied multiple times. this is harmless since the manager
125 # can be called as many times as neccessary and will always
126 # remove itself from the runqueue
127 while (@destroy) { 166 while @destroy;
128 my $coro = pop @destroy; 167
129 $coro->{status} ||= [];
130 $_->ready for @{delete $coro->{join} || []};
131 $coro->{_coro_state} = $manager->{_coro_state};
132 }
133 &schedule; 168 &schedule;
134 } 169 }
135}; 170};
136 171
172$manager->prio (PRIO_MAX);
173
137# static methods. not really. 174# static methods. not really.
138 175
176=back
177
139=head2 STATIC METHODS 178=head2 STATIC METHODS
140 179
141Static methods are actually functions that operate on the current process only. 180Static methods are actually functions that operate on the current coroutine only.
142 181
143=over 4 182=over 4
144 183
145=item async { ... } [@args...] 184=item async { ... } [@args...]
146 185
147Create a new asynchronous process and return it's process object 186Create a new asynchronous coroutine and return it's coroutine object
148(usually unused). When the sub returns the new process is automatically 187(usually unused). When the sub returns the new coroutine is automatically
149terminated. 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.
150 194
151 # create a new coroutine that just prints its arguments 195 # create a new coroutine that just prints its arguments
152 async { 196 async {
153 print "@_\n"; 197 print "@_\n";
154 } 1,2,3,4; 198 } 1,2,3,4;
155 199
156The coderef you submit MUST NOT be a closure that refers to variables
157in an outer scope. This does NOT work. Pass arguments into it instead.
158
159=cut 200=cut
160 201
161sub async(&@) { 202sub async(&@) {
162 my $pid = new Coro @_; 203 my $coro = new Coro @_;
163 $manager->ready; # this ensures that the stack is cloned from the manager
164 $pid->ready; 204 $coro->ready;
165 $pid; 205 $coro
206}
207
208=item async_pool { ... } [@args...]
209
210Similar to C<async>, but uses a coroutine pool, so you should not call
211terminate or join (although you are allowed to), and you get a coroutine
212that might have executed other code already (which can be good or bad :).
213
214Also, the block is executed in an C<eval> context and a warning will be
215issued in case of an exception instead of terminating the program, as C<async> does.
216
217The priority will be reset to C<0> after each job, otherwise the coroutine
218will be re-used "as-is".
219
220The pool size is limited to 8 idle coroutines (this can be adjusted by
221changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
222required.
223
224If you are concerned about pooled coroutines growing a lot because a
225single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {
226terminate }> once per second or so to slowly replenish the pool.
227
228=cut
229
230our $POOL_SIZE = 8;
231our @pool;
232
233sub pool_handler {
234 while () {
235 my ($cb, @arg) = @{ delete $current->{_invoke} };
236
237 eval {
238 $cb->(@arg);
239 };
240 warn $@ if $@;
241
242 last if @pool >= $POOL_SIZE;
243 push @pool, $current;
244
245 $current->prio (0);
246 schedule;
247 }
248}
249
250sub async_pool(&@) {
251 # this is also inlined into the unlock_scheduler
252 my $coro = (pop @pool or new Coro \&pool_handler);
253
254 $coro->{_invoke} = [@_];
255 $coro->ready;
256
257 $coro
166} 258}
167 259
168=item schedule 260=item schedule
169 261
170Calls the scheduler. Please note that the current process will not be put 262Calls the scheduler. Please note that the current coroutine will not be put
171into the ready queue, so calling this function usually means you will 263into the ready queue, so calling this function usually means you will
172never be called again. 264never be called again unless something else (e.g. an event handler) calls
265ready.
173 266
174=cut 267The canonical way to wait on external events is this:
268
269 {
270 # remember current coroutine
271 my $current = $Coro::current;
272
273 # register a hypothetical event handler
274 on_event_invoke sub {
275 # wake up sleeping coroutine
276 $current->ready;
277 undef $current;
278 };
279
280 # call schedule until event occured.
281 # in case we are woken up for other reasons
282 # (current still defined), loop.
283 Coro::schedule while $current;
284 }
175 285
176=item cede 286=item cede
177 287
178"Cede" to other processes. This function puts the current process into the 288"Cede" to other coroutines. This function puts the current coroutine into the
179ready queue and calls C<schedule>, which has the effect of giving up the 289ready queue and calls C<schedule>, which has the effect of giving up the
180current "timeslice" to other coroutines of the same or higher priority. 290current "timeslice" to other coroutines of the same or higher priority.
181 291
182=cut 292Returns true if at least one coroutine switch has happened.
293
294=item Coro::cede_notself
295
296Works like cede, but is not exported by default and will cede to any
297coroutine, regardless of priority, once.
298
299Returns true if at least one coroutine switch has happened.
183 300
184=item terminate [arg...] 301=item terminate [arg...]
185 302
186Terminates the current process. 303Terminates the current coroutine with the given status values (see L<cancel>).
187
188Future versions of this function will allow result arguments.
189 304
190=cut 305=cut
191 306
192sub terminate { 307sub terminate {
193 $current->{status} = [@_];
194 $current->cancel; 308 $current->cancel (@_);
195 &schedule;
196 die; # NORETURN
197} 309}
198 310
199=back 311=back
200 312
201# dynamic methods 313# dynamic methods
202 314
203=head2 PROCESS METHODS 315=head2 COROUTINE METHODS
204 316
205These are the methods you can call on process objects. 317These are the methods you can call on coroutine objects.
206 318
207=over 4 319=over 4
208 320
209=item new Coro \&sub [, @args...] 321=item new Coro \&sub [, @args...]
210 322
211Create a new process and return it. When the sub returns the process 323Create a new coroutine and return it. When the sub returns the coroutine
212automatically terminates as if C<terminate> with the returned values were 324automatically terminates as if C<terminate> with the returned values were
213called. To make the process run you must first put it into the ready queue 325called. To make the coroutine run you must first put it into the ready queue
214by calling the ready method. 326by calling the ready method.
215 327
216=cut 328Calling C<exit> in a coroutine will not work correctly, so do not do that.
217 329
330=cut
331
218sub _newcoro { 332sub _run_coro {
219 terminate &{+shift}; 333 terminate &{+shift};
220} 334}
221 335
222sub new { 336sub new {
223 my $class = shift; 337 my $class = shift;
224 bless {
225 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
226 }, $class;
227}
228 338
229=item $process->ready 339 $class->SUPER::new (\&_run_coro, @_)
340}
230 341
231Put the given process into the ready queue. 342=item $success = $coroutine->ready
232 343
233=cut 344Put the given coroutine into the ready queue (according to it's priority)
345and return true. If the coroutine is already in the ready queue, do nothing
346and return false.
234 347
235=item $process->cancel 348=item $is_ready = $coroutine->is_ready
236 349
237Like C<terminate>, but terminates the specified process instead. 350Return wether the coroutine is currently the ready queue or not,
351
352=item $coroutine->cancel (arg...)
353
354Terminates the given coroutine and makes it return the given arguments as
355status (default: the empty list). Never returns if the coroutine is the
356current coroutine.
238 357
239=cut 358=cut
240 359
241sub cancel { 360sub cancel {
361 my $self = shift;
362 $self->{status} = [@_];
363
364 if ($current == $self) {
242 push @destroy, $_[0]; 365 push @destroy, $self;
243 $manager->ready; 366 $manager->ready;
244 &schedule if $current == $_[0]; 367 &schedule while 1;
368 } else {
369 $self->_cancel;
370 }
245} 371}
246 372
247=item $process->join 373=item $coroutine->join
248 374
249Wait until the coroutine terminates and return any values given to the 375Wait until the coroutine terminates and return any values given to the
250C<terminate> function. C<join> can be called multiple times from multiple 376C<terminate> or C<cancel> functions. C<join> can be called multiple times
251processes. 377from multiple coroutine.
252 378
253=cut 379=cut
254 380
255sub join { 381sub join {
256 my $self = shift; 382 my $self = shift;
383
257 unless ($self->{status}) { 384 unless ($self->{status}) {
258 push @{$self->{join}}, $current; 385 my $current = $current;
259 &schedule; 386
387 push @{$self->{destroy_cb}}, sub {
388 $current->ready;
389 undef $current;
390 };
391
392 &schedule while $current;
260 } 393 }
394
261 wantarray ? @{$self->{status}} : $self->{status}[0]; 395 wantarray ? @{$self->{status}} : $self->{status}[0];
262} 396}
263 397
398=item $coroutine->on_destroy (\&cb)
399
400Registers a callback that is called when this coroutine gets destroyed,
401but before it is joined. The callback gets passed the terminate arguments,
402if any.
403
404=cut
405
406sub on_destroy {
407 my ($self, $cb) = @_;
408
409 push @{ $self->{destroy_cb} }, $cb;
410}
411
264=item $oldprio = $process->prio($newprio) 412=item $oldprio = $coroutine->prio ($newprio)
265 413
266Sets (or gets, if the argument is missing) the priority of the 414Sets (or gets, if the argument is missing) the priority of the
267process. Higher priority processes get run before lower priority 415coroutine. Higher priority coroutines get run before lower priority
268processes. Priorities are smalled signed integer (currently -4 .. +3), 416coroutines. Priorities are small signed integers (currently -4 .. +3),
269that you can refer to using PRIO_xxx constants (use the import tag :prio 417that you can refer to using PRIO_xxx constants (use the import tag :prio
270to get then): 418to get then):
271 419
272 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 420 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
273 3 > 1 > 0 > -1 > -3 > -4 421 3 > 1 > 0 > -1 > -3 > -4
276 current->prio(PRIO_HIGH); 424 current->prio(PRIO_HIGH);
277 425
278The idle coroutine ($Coro::idle) always has a lower priority than any 426The idle coroutine ($Coro::idle) always has a lower priority than any
279existing coroutine. 427existing coroutine.
280 428
281Changing the priority of the current process will take effect immediately, 429Changing the priority of the current coroutine will take effect immediately,
282but changing the priority of processes in the ready queue (but not 430but changing the priority of coroutines in the ready queue (but not
283running) will only take effect after the next schedule (of that 431running) will only take effect after the next schedule (of that
284process). This is a bug that will be fixed in some future version. 432coroutine). This is a bug that will be fixed in some future version.
285 433
286=cut
287
288sub prio {
289 my $old = $_[0]{prio};
290 $_[0]{prio} = $_[1] if @_ > 1;
291 $old;
292}
293
294=item $newprio = $process->nice($change) 434=item $newprio = $coroutine->nice ($change)
295 435
296Similar to C<prio>, but subtract the given value from the priority (i.e. 436Similar to C<prio>, but subtract the given value from the priority (i.e.
297higher values mean lower priority, just as in unix). 437higher values mean lower priority, just as in unix).
298 438
299=cut
300
301sub nice {
302 $_[0]{prio} -= $_[1];
303}
304
305=item $olddesc = $process->desc($newdesc) 439=item $olddesc = $coroutine->desc ($newdesc)
306 440
307Sets (or gets in case the argument is missing) the description for this 441Sets (or gets in case the argument is missing) the description for this
308process. This is just a free-form string you can associate with a process. 442coroutine. This is just a free-form string you can associate with a coroutine.
309 443
310=cut 444=cut
311 445
312sub desc { 446sub desc {
313 my $old = $_[0]{desc}; 447 my $old = $_[0]{desc};
315 $old; 449 $old;
316} 450}
317 451
318=back 452=back
319 453
454=head2 GLOBAL FUNCTIONS
455
456=over 4
457
458=item Coro::nready
459
460Returns the number of coroutines that are currently in the ready state,
461i.e. that can be swicthed to. The value C<0> means that the only runnable
462coroutine is the currently running one, so C<cede> would have no effect,
463and C<schedule> would cause a deadlock unless there is an idle handler
464that wakes up some coroutines.
465
466=item my $guard = Coro::guard { ... }
467
468This creates and returns a guard object. Nothing happens until the objetc
469gets destroyed, in which case the codeblock given as argument will be
470executed. This is useful to free locks or other resources in case of a
471runtime error or when the coroutine gets canceled, as in both cases the
472guard block will be executed. The guard object supports only one method,
473C<< ->cancel >>, which will keep the codeblock from being executed.
474
475Example: set some flag and clear it again when the coroutine gets canceled
476or the function returns:
477
478 sub do_something {
479 my $guard = Coro::guard { $busy = 0 };
480 $busy = 1;
481
482 # do something that requires $busy to be true
483 }
484
485=cut
486
487sub guard(&) {
488 bless \(my $cb = $_[0]), "Coro::guard"
489}
490
491sub Coro::guard::cancel {
492 ${$_[0]} = sub { };
493}
494
495sub Coro::guard::DESTROY {
496 ${$_[0]}->();
497}
498
499
500=item unblock_sub { ... }
501
502This utility function takes a BLOCK or code reference and "unblocks" it,
503returning the new coderef. This means that the new coderef will return
504immediately without blocking, returning nothing, while the original code
505ref will be called (with parameters) from within its own coroutine.
506
507The reason this fucntion exists is that many event libraries (such as the
508venerable L<Event|Event> module) are not coroutine-safe (a weaker form
509of thread-safety). This means you must not block within event callbacks,
510otherwise you might suffer from crashes or worse.
511
512This function allows your callbacks to block by executing them in another
513coroutine where it is safe to block. One example where blocking is handy
514is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
515disk.
516
517In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
518creating event callbacks that want to block.
519
520=cut
521
522our @unblock_queue;
523
524# we create a special coro because we want to cede,
525# to reduce pressure on the coro pool (because most callbacks
526# return immediately and can be reused) and because we cannot cede
527# inside an event callback.
528our $unblock_scheduler = async {
529 while () {
530 while (my $cb = pop @unblock_queue) {
531 # this is an inlined copy of async_pool
532 my $coro = (pop @pool or new Coro \&pool_handler);
533
534 $coro->{_invoke} = $cb;
535 $coro->ready;
536 cede; # for short-lived callbacks, this reduces pressure on the coro pool
537 }
538 schedule; # sleep well
539 }
540};
541
542sub unblock_sub(&) {
543 my $cb = shift;
544
545 sub {
546 unshift @unblock_queue, [$cb, @_];
547 $unblock_scheduler->ready;
548 }
549}
550
551=back
552
320=cut 553=cut
321 554
3221; 5551;
323 556
324=head1 BUGS/LIMITATIONS 557=head1 BUGS/LIMITATIONS
325 558
326 - you must make very sure that no coro is still active on global destruction. 559 - you must make very sure that no coro is still active on global
327 very bad things might happen otherwise (usually segfaults). 560 destruction. very bad things might happen otherwise (usually segfaults).
561
328 - this module is not thread-safe. You should only ever use this module from 562 - this module is not thread-safe. You should only ever use this module
329 the same thread (this requirement might be loosened in the future to 563 from the same thread (this requirement might be losened in the future
330 allow per-thread schedulers, but Coro::State does not yet allow this). 564 to allow per-thread schedulers, but Coro::State does not yet allow
565 this).
331 566
332=head1 SEE ALSO 567=head1 SEE ALSO
333 568
334L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 569Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
335L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>, 570
336L<Coro::Handle>, L<Coro::Socket>. 571Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
572
573Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
574
575Embedding: L<Coro:MakeMaker>
337 576
338=head1 AUTHOR 577=head1 AUTHOR
339 578
340 Marc Lehmann <pcg@goof.com> 579 Marc Lehmann <schmorp@schmorp.de>
341 http://www.goof.com/pcg/marc/ 580 http://home.schmorp.de/
342 581
343=cut 582=cut
344 583

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