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Revision 1.40 by root, Sun Oct 28 17:00:05 2001 UTC vs.
Revision 1.115 by root, Wed Feb 28 11:43:03 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
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
51our $idle; # idle handler
52our $main; # main coroutine
53our $current; # current coroutine
54
43$VERSION = 0.51; 55our $VERSION = '3.501';
44 56
45@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
46%EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
47 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48); 60);
49@EXPORT_OK = @{$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<$main> (of course).
111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essentiel you are encouraged to use the
114C<Coro::current> function instead.
93 115
94=cut 116=cut
95 117
96# maybe some other module used Coro::Specific before... 118# maybe some other module used Coro::Specific before...
97if ($current) {
98 $main->{specific} = $current->{specific}; 119$main->{specific} = $current->{specific}
99} 120 if $current;
100 121
101our $current = $main; 122_set_current $main;
102 123
103sub current() { $current } 124sub current() { $current }
104 125
105=item $idle 126=item $idle
106 127
107The coroutine to switch to when no other coroutine is running. The default 128A callback that is called whenever the scheduler finds no ready coroutines
108implementation prints "FATAL: deadlock detected" and exits. 129to run. The default implementation prints "FATAL: deadlock detected" and
130exits, because the program has no other way to continue.
109 131
110=cut 132This hook is overwritten by modules such as C<Coro::Timer> and
133C<Coro::Event> to wait on an external event that hopefully wake up a
134coroutine so the scheduler can run it.
111 135
112# should be done using priorities :( 136Please note that if your callback recursively invokes perl (e.g. for event
113our $idle = new Coro sub { 137handlers), then it must be prepared to be called recursively.
114 print STDERR "FATAL: deadlock detected\n"; 138
115 exit(51); 139=cut
140
141$idle = sub {
142 require Carp;
143 Carp::croak ("FATAL: deadlock detected");
116}; 144};
145
146sub _cancel {
147 my ($self) = @_;
148
149 # free coroutine data and mark as destructed
150 $self->_destroy
151 or return;
152
153 # call all destruction callbacks
154 $_->(@{$self->{status}})
155 for @{(delete $self->{destroy_cb}) || []};
156}
117 157
118# this coroutine is necessary because a coroutine 158# this coroutine is necessary because a coroutine
119# cannot destroy itself. 159# cannot destroy itself.
120my @destroy; 160my @destroy;
121my $manager; 161my $manager;
162
122$manager = new Coro sub { 163$manager = new Coro sub {
123 while() { 164 while () {
124 # by overwriting the state object with the manager we destroy it 165 (shift @destroy)->_cancel
125 # while still being able to schedule this coroutine (in case it has
126 # been readied multiple times. this is harmless since the manager
127 # can be called as many times as neccessary and will always
128 # remove itself from the runqueue
129 while (@destroy) { 166 while @destroy;
130 my $coro = pop @destroy; 167
131 $coro->{status} ||= [];
132 $_->ready for @{delete $coro->{join} || []};
133 $coro->{_coro_state} = $manager->{_coro_state};
134 }
135 &schedule; 168 &schedule;
136 } 169 }
137}; 170};
138 171
172$manager->prio (PRIO_MAX);
173
139# static methods. not really. 174# static methods. not really.
140 175
176=back
177
141=head2 STATIC METHODS 178=head2 STATIC METHODS
142 179
143Static methods are actually functions that operate on the current process only. 180Static methods are actually functions that operate on the current coroutine only.
144 181
145=over 4 182=over 4
146 183
147=item async { ... } [@args...] 184=item async { ... } [@args...]
148 185
149Create a new asynchronous process and return it's process object 186Create a new asynchronous coroutine and return it's coroutine object
150(usually unused). When the sub returns the new process is automatically 187(usually unused). When the sub returns the new coroutine is automatically
151terminated. 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.
152 194
153 # create a new coroutine that just prints its arguments 195 # create a new coroutine that just prints its arguments
154 async { 196 async {
155 print "@_\n"; 197 print "@_\n";
156 } 1,2,3,4; 198 } 1,2,3,4;
157 199
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 200=cut
162 201
163sub async(&@) { 202sub async(&@) {
164 my $pid = new Coro @_; 203 my $coro = new Coro @_;
165 $manager->ready; # this ensures that the stack is cloned from the manager
166 $pid->ready; 204 $coro->ready;
167 $pid; 205 $coro
206}
207
208=item async_pool { ... } [@args...]
209
210Similar to C<async>, but uses a coroutine pool, so you should not call
211terminate or join (although you are allowed to), and you get a coroutine
212that might have executed other code already (which can be good or bad :).
213
214Also, the block is executed in an C<eval> context and a warning will be
215issued in case of an exception instead of terminating the program, as
216C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
217will not work in the expected way, unless you call terminate or cancel,
218which somehow defeats the purpose of pooling.
219
220The priority will be reset to C<0> after each job, otherwise the coroutine
221will be re-used "as-is".
222
223The pool size is limited to 8 idle coroutines (this can be adjusted by
224changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
225required.
226
227If you are concerned about pooled coroutines growing a lot because a
228single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {
229terminate }> once per second or so to slowly replenish the pool.
230
231=cut
232
233our $POOL_SIZE = 8;
234our @pool;
235
236sub pool_handler {
237 while () {
238 eval {
239 my ($cb, @arg) = @{ delete $current->{_invoke} or return };
240 $cb->(@arg);
241 };
242 warn $@ if $@;
243
244 last if @pool >= $POOL_SIZE;
245 push @pool, $current;
246
247 $current->prio (0);
248 schedule;
249 }
250}
251
252sub async_pool(&@) {
253 # this is also inlined into the unlock_scheduler
254 my $coro = (pop @pool or new Coro \&pool_handler);
255
256 $coro->{_invoke} = [@_];
257 $coro->ready;
258
259 $coro
168} 260}
169 261
170=item schedule 262=item schedule
171 263
172Calls the scheduler. Please note that the current process will not be put 264Calls the scheduler. Please note that the current coroutine will not be put
173into the ready queue, so calling this function usually means you will 265into the ready queue, so calling this function usually means you will
174never be called again. 266never be called again unless something else (e.g. an event handler) calls
267ready.
175 268
176=cut 269The canonical way to wait on external events is this:
270
271 {
272 # remember current coroutine
273 my $current = $Coro::current;
274
275 # register a hypothetical event handler
276 on_event_invoke sub {
277 # wake up sleeping coroutine
278 $current->ready;
279 undef $current;
280 };
281
282 # call schedule until event occured.
283 # in case we are woken up for other reasons
284 # (current still defined), loop.
285 Coro::schedule while $current;
286 }
177 287
178=item cede 288=item cede
179 289
180"Cede" to other processes. This function puts the current process into the 290"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 291ready queue and calls C<schedule>, which has the effect of giving up the
182current "timeslice" to other coroutines of the same or higher priority. 292current "timeslice" to other coroutines of the same or higher priority.
183 293
184=cut 294Returns true if at least one coroutine switch has happened.
295
296=item Coro::cede_notself
297
298Works like cede, but is not exported by default and will cede to any
299coroutine, regardless of priority, once.
300
301Returns true if at least one coroutine switch has happened.
185 302
186=item terminate [arg...] 303=item terminate [arg...]
187 304
188Terminates the current process. 305Terminates the current coroutine with the given status values (see L<cancel>).
189
190Future versions of this function will allow result arguments.
191 306
192=cut 307=cut
193 308
194sub terminate { 309sub terminate {
195 $current->{status} = [@_];
196 $current->cancel; 310 $current->cancel (@_);
197 &schedule;
198 die; # NORETURN
199} 311}
200 312
201=back 313=back
202 314
203# dynamic methods 315# dynamic methods
204 316
205=head2 PROCESS METHODS 317=head2 COROUTINE METHODS
206 318
207These are the methods you can call on process objects. 319These are the methods you can call on coroutine objects.
208 320
209=over 4 321=over 4
210 322
211=item new Coro \&sub [, @args...] 323=item new Coro \&sub [, @args...]
212 324
213Create a new process and return it. When the sub returns the process 325Create a new coroutine and return it. When the sub returns the coroutine
214automatically terminates as if C<terminate> with the returned values were 326automatically 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 327called. To make the coroutine run you must first put it into the ready queue
216calling the ready method. 328by calling the ready method.
217 329
218The coderef you submit MUST NOT be a closure that refers to variables 330Calling C<exit> in a coroutine will not work correctly, so do not do that.
219in an outer scope. This does NOT work. Pass arguments into it instead.
220 331
221=cut 332=cut
222 333
223sub _newcoro { 334sub _run_coro {
224 terminate &{+shift}; 335 terminate &{+shift};
225} 336}
226 337
227sub new { 338sub new {
228 my $class = shift; 339 my $class = shift;
229 bless {
230 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
231 }, $class;
232}
233 340
234=item $process->ready 341 $class->SUPER::new (\&_run_coro, @_)
342}
235 343
236Put the given process into the ready queue. 344=item $success = $coroutine->ready
237 345
238=cut 346Put the given coroutine into the ready queue (according to it's priority)
347and return true. If the coroutine is already in the ready queue, do nothing
348and return false.
239 349
240=item $process->cancel 350=item $is_ready = $coroutine->is_ready
241 351
242Like C<terminate>, but terminates the specified process instead. 352Return wether the coroutine is currently the ready queue or not,
353
354=item $coroutine->cancel (arg...)
355
356Terminates the given coroutine and makes it return the given arguments as
357status (default: the empty list). Never returns if the coroutine is the
358current coroutine.
243 359
244=cut 360=cut
245 361
246sub cancel { 362sub cancel {
363 my $self = shift;
364 $self->{status} = [@_];
365
366 if ($current == $self) {
247 push @destroy, $_[0]; 367 push @destroy, $self;
248 $manager->ready; 368 $manager->ready;
249 &schedule if $current == $_[0]; 369 &schedule while 1;
370 } else {
371 $self->_cancel;
372 }
250} 373}
251 374
252=item $process->join 375=item $coroutine->join
253 376
254Wait until the coroutine terminates and return any values given to the 377Wait until the coroutine terminates and return any values given to the
255C<terminate> function. C<join> can be called multiple times from multiple 378C<terminate> or C<cancel> functions. C<join> can be called multiple times
256processes. 379from multiple coroutine.
257 380
258=cut 381=cut
259 382
260sub join { 383sub join {
261 my $self = shift; 384 my $self = shift;
385
262 unless ($self->{status}) { 386 unless ($self->{status}) {
263 push @{$self->{join}}, $current; 387 my $current = $current;
264 &schedule; 388
389 push @{$self->{destroy_cb}}, sub {
390 $current->ready;
391 undef $current;
392 };
393
394 &schedule while $current;
265 } 395 }
396
266 wantarray ? @{$self->{status}} : $self->{status}[0]; 397 wantarray ? @{$self->{status}} : $self->{status}[0];
267} 398}
268 399
400=item $coroutine->on_destroy (\&cb)
401
402Registers a callback that is called when this coroutine gets destroyed,
403but before it is joined. The callback gets passed the terminate arguments,
404if any.
405
406=cut
407
408sub on_destroy {
409 my ($self, $cb) = @_;
410
411 push @{ $self->{destroy_cb} }, $cb;
412}
413
269=item $oldprio = $process->prio($newprio) 414=item $oldprio = $coroutine->prio ($newprio)
270 415
271Sets the priority of the process. Higher priority processes get run before 416Sets (or gets, if the argument is missing) the priority of the
272lower priority processes. Priorities are smalled signed integer (currently 417coroutine. Higher priority coroutines get run before lower priority
418coroutines. Priorities are small signed integers (currently -4 .. +3),
273-4 .. +3), that you can refer to using PRIO_xxx constants (use the import 419that you can refer to using PRIO_xxx constants (use the import tag :prio
274tag :prio to get then): 420to get then):
275 421
276 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 422 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
277 3 > 1 > 0 > -1 > -3 > -4 423 3 > 1 > 0 > -1 > -3 > -4
278 424
279 # set priority to HIGH 425 # set priority to HIGH
280 current->prio(PRIO_HIGH); 426 current->prio(PRIO_HIGH);
281 427
282The idle coroutine ($Coro::idle) always has a lower priority than any 428The idle coroutine ($Coro::idle) always has a lower priority than any
283existing coroutine. 429existing coroutine.
284 430
285Changing the priority of the current process will take effect immediately, 431Changing the priority of the current coroutine will take effect immediately,
286but changing the priority of processes in the ready queue (but not 432but changing the priority of coroutines in the ready queue (but not
287running) will only take effect after the next schedule (of that 433running) will only take effect after the next schedule (of that
288process). This is a bug that will be fixed in some future version. 434coroutine). This is a bug that will be fixed in some future version.
289 435
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) 436=item $newprio = $coroutine->nice ($change)
299 437
300Similar to C<prio>, but subtract the given value from the priority (i.e. 438Similar to C<prio>, but subtract the given value from the priority (i.e.
301higher values mean lower priority, just as in unix). 439higher values mean lower priority, just as in unix).
302 440
303=cut 441=item $olddesc = $coroutine->desc ($newdesc)
304 442
305sub nice { 443Sets (or gets in case the argument is missing) the description for this
306 $_[0]{prio} -= $_[1]; 444coroutine. This is just a free-form string you can associate with a coroutine.
445
446=cut
447
448sub desc {
449 my $old = $_[0]{desc};
450 $_[0]{desc} = $_[1] if @_ > 1;
451 $old;
307} 452}
308 453
309=back 454=back
310 455
456=head2 GLOBAL FUNCTIONS
457
458=over 4
459
460=item Coro::nready
461
462Returns the number of coroutines that are currently in the ready state,
463i.e. that can be swicthed to. The value C<0> means that the only runnable
464coroutine is the currently running one, so C<cede> would have no effect,
465and C<schedule> would cause a deadlock unless there is an idle handler
466that wakes up some coroutines.
467
468=item my $guard = Coro::guard { ... }
469
470This creates and returns a guard object. Nothing happens until the objetc
471gets destroyed, in which case the codeblock given as argument will be
472executed. This is useful to free locks or other resources in case of a
473runtime error or when the coroutine gets canceled, as in both cases the
474guard block will be executed. The guard object supports only one method,
475C<< ->cancel >>, which will keep the codeblock from being executed.
476
477Example: set some flag and clear it again when the coroutine gets canceled
478or the function returns:
479
480 sub do_something {
481 my $guard = Coro::guard { $busy = 0 };
482 $busy = 1;
483
484 # do something that requires $busy to be true
485 }
486
487=cut
488
489sub guard(&) {
490 bless \(my $cb = $_[0]), "Coro::guard"
491}
492
493sub Coro::guard::cancel {
494 ${$_[0]} = sub { };
495}
496
497sub Coro::guard::DESTROY {
498 ${$_[0]}->();
499}
500
501
502=item unblock_sub { ... }
503
504This utility function takes a BLOCK or code reference and "unblocks" it,
505returning the new coderef. This means that the new coderef will return
506immediately without blocking, returning nothing, while the original code
507ref will be called (with parameters) from within its own coroutine.
508
509The reason this fucntion exists is that many event libraries (such as the
510venerable L<Event|Event> module) are not coroutine-safe (a weaker form
511of thread-safety). This means you must not block within event callbacks,
512otherwise you might suffer from crashes or worse.
513
514This function allows your callbacks to block by executing them in another
515coroutine where it is safe to block. One example where blocking is handy
516is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
517disk.
518
519In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
520creating event callbacks that want to block.
521
522=cut
523
524our @unblock_queue;
525
526# we create a special coro because we want to cede,
527# to reduce pressure on the coro pool (because most callbacks
528# return immediately and can be reused) and because we cannot cede
529# inside an event callback.
530our $unblock_scheduler = async {
531 while () {
532 while (my $cb = pop @unblock_queue) {
533 # this is an inlined copy of async_pool
534 my $coro = (pop @pool or new Coro \&pool_handler);
535
536 $coro->{_invoke} = $cb;
537 $coro->ready;
538 cede; # for short-lived callbacks, this reduces pressure on the coro pool
539 }
540 schedule; # sleep well
541 }
542};
543
544sub unblock_sub(&) {
545 my $cb = shift;
546
547 sub {
548 unshift @unblock_queue, [$cb, @_];
549 $unblock_scheduler->ready;
550 }
551}
552
553=back
554
311=cut 555=cut
312 556
3131; 5571;
314 558
315=head1 BUGS/LIMITATIONS 559=head1 BUGS/LIMITATIONS
316 560
317 - you must make very sure that no coro is still active on global destruction. 561 - you must make very sure that no coro is still active on global
318 very bad things might happen otherwise (usually segfaults). 562 destruction. very bad things might happen otherwise (usually segfaults).
563
319 - this module is not thread-safe. You must only ever use this module from 564 - 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 565 from the same thread (this requirement might be losened in the future
321 allow per-thread schedulers, but Coro::State does not yet allow this). 566 to allow per-thread schedulers, but Coro::State does not yet allow
567 this).
322 568
323=head1 SEE ALSO 569=head1 SEE ALSO
324 570
325L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 571Support/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>, 572
327L<Coro::Handle>, L<Coro::Socket>. 573Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
574
575Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
576
577Embedding: L<Coro:MakeMaker>
328 578
329=head1 AUTHOR 579=head1 AUTHOR
330 580
331 Marc Lehmann <pcg@goof.com> 581 Marc Lehmann <schmorp@schmorp.de>
332 http://www.goof.com/pcg/marc/ 582 http://home.schmorp.de/
333 583
334=cut 584=cut
335 585

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