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Revision 1.58 by pcg, Fri Feb 13 23:17:41 2004 UTC vs.
Revision 1.132 by root, Thu Sep 20 22:53:23 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
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@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
28callchain, it's own set of lexicals and it's own set of perl's most 37its own set of lexicals and its own set of perls most important global
29important global variables. 38variables.
30 39
31=cut 40=cut
32 41
33package Coro; 42package Coro;
34 43
35BEGIN { eval { require warnings } && warnings->unimport ("uninitialized") } 44use strict;
45no warnings "uninitialized";
36 46
37use Coro::State; 47use Coro::State;
38 48
39use vars qw($idle $main $current); 49use base qw(Coro::State Exporter);
40 50
41use base Exporter; 51our $idle; # idle handler
52our $main; # main coroutine
53our $current; # current coroutine
42 54
43$VERSION = 0.95; 55our $VERSION = '3.7';
44 56
45@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
46%EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
47 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48); 60);
49@EXPORT_OK = @{$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, $ref) = (shift, shift);
61 my @attrs; 76 my @attrs;
62 for (@_) { 77 for (@_) {
89 104
90$main = new Coro; 105$main = new Coro;
91 106
92=item $current (or as function: current) 107=item $current (or as function: current)
93 108
94The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). 109The current coroutine (the last coroutine switched to). The initial value
110is C<$main> (of course).
95 111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essential you are encouraged to use the
114C<Coro::current> function instead.
115
96=cut 116=cut
117
118$main->{desc} = "[main::]";
97 119
98# maybe some other module used Coro::Specific before... 120# maybe some other module used Coro::Specific before...
99if ($current) {
100 $main->{specific} = $current->{specific}; 121$main->{specific} = $current->{specific}
101} 122 if $current;
102 123
103$current = $main; 124_set_current $main;
104 125
105sub current() { $current } 126sub current() { $current }
106 127
107=item $idle 128=item $idle
108 129
109The coroutine to switch to when no other coroutine is running. The default 130A callback that is called whenever the scheduler finds no ready coroutines
110implementation prints "FATAL: deadlock detected" and exits. 131to run. The default implementation prints "FATAL: deadlock detected" and
132exits, because the program has no other way to continue.
111 133
112=cut 134This hook is overwritten by modules such as C<Coro::Timer> and
135C<Coro::Event> to wait on an external event that hopefully wake up a
136coroutine so the scheduler can run it.
113 137
114# should be done using priorities :( 138Please note that if your callback recursively invokes perl (e.g. for event
115$idle = new Coro sub { 139handlers), then it must be prepared to be called recursively.
116 print STDERR "FATAL: deadlock detected\n"; 140
117 exit(51); 141=cut
142
143$idle = sub {
144 require Carp;
145 Carp::croak ("FATAL: deadlock detected");
118}; 146};
147
148sub _cancel {
149 my ($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}
119 159
120# this coroutine is necessary because a coroutine 160# this coroutine is necessary because a coroutine
121# cannot destroy itself. 161# cannot destroy itself.
122my @destroy; 162my @destroy;
123my $manager; 163my $manager;
164
124$manager = new Coro sub { 165$manager = new Coro sub {
125 while () { 166 while () {
126 # by overwriting the state object with the manager we destroy it 167 (shift @destroy)->_cancel
127 # while still being able to schedule this coroutine (in case it has
128 # been readied multiple times. this is harmless since the manager
129 # can be called as many times as neccessary and will always
130 # remove itself from the runqueue
131 while (@destroy) { 168 while @destroy;
132 my $coro = pop @destroy; 169
133 $coro->{status} ||= [];
134 $_->ready for @{delete $coro->{join} || []};
135 $coro->{_coro_state} = $manager->{_coro_state};
136 }
137 &schedule; 170 &schedule;
138 } 171 }
139}; 172};
173$manager->desc ("[coro manager]");
174$manager->prio (PRIO_MAX);
140 175
141# static methods. not really. 176# static methods. not really.
142 177
143=back 178=back
144 179
145=head2 STATIC METHODS 180=head2 STATIC METHODS
146 181
147Static methods are actually functions that operate on the current process only. 182Static methods are actually functions that operate on the current coroutine only.
148 183
149=over 4 184=over 4
150 185
151=item async { ... } [@args...] 186=item async { ... } [@args...]
152 187
153Create a new asynchronous process and return it's process object 188Create a new asynchronous coroutine and return it's coroutine object
154(usually unused). When the sub returns the new process is automatically 189(usually unused). When the sub returns the new coroutine is automatically
155terminated. 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.
156 195
157 # create a new coroutine that just prints its arguments 196 # create a new coroutine that just prints its arguments
158 async { 197 async {
159 print "@_\n"; 198 print "@_\n";
160 } 1,2,3,4; 199 } 1,2,3,4;
161 200
162=cut 201=cut
163 202
164sub async(&@) { 203sub async(&@) {
165 my $pid = new Coro @_; 204 my $coro = new Coro @_;
166 $manager->ready; # this ensures that the stack is cloned from the manager
167 $pid->ready; 205 $coro->ready;
168 $pid; 206 $coro
207}
208
209=item async_pool { ... } [@args...]
210
211Similar to C<async>, but uses a coroutine pool, so you should not call
212terminate or join (although you are allowed to), and you get a coroutine
213that might have executed other code already (which can be good or bad :).
214
215Also, the block is executed in an C<eval> context and a warning will be
216issued in case of an exception instead of terminating the program, as
217C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
218will not work in the expected way, unless you call terminate or cancel,
219which somehow defeats the purpose of pooling.
220
221The priority will be reset to C<0> after each job, otherwise the coroutine
222will be re-used "as-is".
223
224The pool size is limited to 8 idle coroutines (this can be adjusted by
225changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
226required.
227
228If you are concerned about pooled coroutines growing a lot because a
229single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {
230terminate }> once per second or so to slowly replenish the pool.
231
232=cut
233
234our $POOL_SIZE = 8;
235our $MAX_POOL_RSS = 64 * 1024;
236our @pool;
237
238sub pool_handler {
239 while () {
240 $current->{desc} = "[async_pool]";
241
242 eval {
243 my ($cb, @arg) = @{ delete $current->{_invoke} or return };
244 $cb->(@arg);
245 };
246 warn $@ if $@;
247
248 last if @pool >= $POOL_SIZE || $current->rss >= $MAX_POOL_RSS;
249
250 push @pool, $current;
251 $current->{desc} = "[async_pool idle]";
252 $current->save (Coro::State::SAVE_DEF);
253 $current->prio (0);
254 schedule;
255 }
256}
257
258sub async_pool(&@) {
259 # this is also inlined into the unlock_scheduler
260 my $coro = (pop @pool) || new Coro \&pool_handler;;
261
262 $coro->{_invoke} = [@_];
263 $coro->ready;
264
265 $coro
169} 266}
170 267
171=item schedule 268=item schedule
172 269
173Calls the scheduler. Please note that the current process will not be put 270Calls the scheduler. Please note that the current coroutine will not be put
174into the ready queue, so calling this function usually means you will 271into the ready queue, so calling this function usually means you will
175never be called again. 272never be called again unless something else (e.g. an event handler) calls
273ready.
176 274
177=cut 275The canonical way to wait on external events is this:
276
277 {
278 # remember current coroutine
279 my $current = $Coro::current;
280
281 # register a hypothetical event handler
282 on_event_invoke sub {
283 # wake up sleeping coroutine
284 $current->ready;
285 undef $current;
286 };
287
288 # call schedule until event occurred.
289 # in case we are woken up for other reasons
290 # (current still defined), loop.
291 Coro::schedule while $current;
292 }
178 293
179=item cede 294=item cede
180 295
181"Cede" to other processes. This function puts the current process into the 296"Cede" to other coroutines. This function puts the current coroutine into the
182ready queue and calls C<schedule>, which has the effect of giving up the 297ready queue and calls C<schedule>, which has the effect of giving up the
183current "timeslice" to other coroutines of the same or higher priority. 298current "timeslice" to other coroutines of the same or higher priority.
184 299
185=cut 300Returns true if at least one coroutine switch has happened.
301
302=item Coro::cede_notself
303
304Works like cede, but is not exported by default and will cede to any
305coroutine, regardless of priority, once.
306
307Returns true if at least one coroutine switch has happened.
186 308
187=item terminate [arg...] 309=item terminate [arg...]
188 310
189Terminates the current process. 311Terminates the current coroutine with the given status values (see L<cancel>).
190
191Future versions of this function will allow result arguments.
192 312
193=cut 313=cut
194 314
195sub terminate { 315sub terminate {
196 $current->{status} = [@_];
197 $current->cancel; 316 $current->cancel (@_);
198 &schedule;
199 die; # NORETURN
200} 317}
201 318
202=back 319=back
203 320
204# dynamic methods 321# dynamic methods
205 322
206=head2 PROCESS METHODS 323=head2 COROUTINE METHODS
207 324
208These are the methods you can call on process objects. 325These are the methods you can call on coroutine objects.
209 326
210=over 4 327=over 4
211 328
212=item new Coro \&sub [, @args...] 329=item new Coro \&sub [, @args...]
213 330
214Create a new process and return it. When the sub returns the process 331Create a new coroutine and return it. When the sub returns the coroutine
215automatically terminates as if C<terminate> with the returned values were 332automatically terminates as if C<terminate> with the returned values were
216called. To make the process run you must first put it into the ready queue 333called. To make the coroutine run you must first put it into the ready queue
217by calling the ready method. 334by calling the ready method.
218 335
219=cut 336See C<async> for additional discussion.
220 337
338=cut
339
221sub _newcoro { 340sub _run_coro {
222 terminate &{+shift}; 341 terminate &{+shift};
223} 342}
224 343
225sub new { 344sub new {
226 my $class = shift; 345 my $class = shift;
227 bless {
228 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
229 }, $class;
230}
231 346
232=item $process->ready 347 $class->SUPER::new (\&_run_coro, @_)
348}
233 349
234Put the given process into the ready queue. 350=item $success = $coroutine->ready
235 351
236=cut 352Put the given coroutine into the ready queue (according to it's priority)
353and return true. If the coroutine is already in the ready queue, do nothing
354and return false.
237 355
238=item $process->cancel 356=item $is_ready = $coroutine->is_ready
239 357
240Like C<terminate>, but terminates the specified process instead. 358Return wether the coroutine is currently the ready queue or not,
359
360=item $coroutine->cancel (arg...)
361
362Terminates the given coroutine and makes it return the given arguments as
363status (default: the empty list). Never returns if the coroutine is the
364current coroutine.
241 365
242=cut 366=cut
243 367
244sub cancel { 368sub cancel {
369 my $self = shift;
370 $self->{status} = [@_];
371
372 if ($current == $self) {
245 push @destroy, $_[0]; 373 push @destroy, $self;
246 $manager->ready; 374 $manager->ready;
247 &schedule if $current == $_[0]; 375 &schedule while 1;
376 } else {
377 $self->_cancel;
378 }
248} 379}
249 380
250=item $process->join 381=item $coroutine->join
251 382
252Wait until the coroutine terminates and return any values given to the 383Wait until the coroutine terminates and return any values given to the
253C<terminate> function. C<join> can be called multiple times from multiple 384C<terminate> or C<cancel> functions. C<join> can be called multiple times
254processes. 385from multiple coroutine.
255 386
256=cut 387=cut
257 388
258sub join { 389sub join {
259 my $self = shift; 390 my $self = shift;
391
260 unless ($self->{status}) { 392 unless ($self->{status}) {
261 push @{$self->{join}}, $current; 393 my $current = $current;
262 &schedule; 394
395 push @{$self->{destroy_cb}}, sub {
396 $current->ready;
397 undef $current;
398 };
399
400 &schedule while $current;
263 } 401 }
402
264 wantarray ? @{$self->{status}} : $self->{status}[0]; 403 wantarray ? @{$self->{status}} : $self->{status}[0];
265} 404}
266 405
406=item $coroutine->on_destroy (\&cb)
407
408Registers a callback that is called when this coroutine gets destroyed,
409but before it is joined. The callback gets passed the terminate arguments,
410if any.
411
412=cut
413
414sub on_destroy {
415 my ($self, $cb) = @_;
416
417 push @{ $self->{destroy_cb} }, $cb;
418}
419
267=item $oldprio = $process->prio($newprio) 420=item $oldprio = $coroutine->prio ($newprio)
268 421
269Sets (or gets, if the argument is missing) the priority of the 422Sets (or gets, if the argument is missing) the priority of the
270process. Higher priority processes get run before lower priority 423coroutine. Higher priority coroutines get run before lower priority
271processes. Priorities are small signed integers (currently -4 .. +3), 424coroutines. Priorities are small signed integers (currently -4 .. +3),
272that you can refer to using PRIO_xxx constants (use the import tag :prio 425that you can refer to using PRIO_xxx constants (use the import tag :prio
273to get then): 426to get then):
274 427
275 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 428 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
276 3 > 1 > 0 > -1 > -3 > -4 429 3 > 1 > 0 > -1 > -3 > -4
279 current->prio(PRIO_HIGH); 432 current->prio(PRIO_HIGH);
280 433
281The idle coroutine ($Coro::idle) always has a lower priority than any 434The idle coroutine ($Coro::idle) always has a lower priority than any
282existing coroutine. 435existing coroutine.
283 436
284Changing the priority of the current process will take effect immediately, 437Changing the priority of the current coroutine will take effect immediately,
285but changing the priority of processes in the ready queue (but not 438but changing the priority of coroutines in the ready queue (but not
286running) will only take effect after the next schedule (of that 439running) will only take effect after the next schedule (of that
287process). This is a bug that will be fixed in some future version. 440coroutine). This is a bug that will be fixed in some future version.
288 441
289=cut
290
291sub prio {
292 my $old = $_[0]{prio};
293 $_[0]{prio} = $_[1] if @_ > 1;
294 $old;
295}
296
297=item $newprio = $process->nice($change) 442=item $newprio = $coroutine->nice ($change)
298 443
299Similar to C<prio>, but subtract the given value from the priority (i.e. 444Similar to C<prio>, but subtract the given value from the priority (i.e.
300higher values mean lower priority, just as in unix). 445higher values mean lower priority, just as in unix).
301 446
302=cut
303
304sub nice {
305 $_[0]{prio} -= $_[1];
306}
307
308=item $olddesc = $process->desc($newdesc) 447=item $olddesc = $coroutine->desc ($newdesc)
309 448
310Sets (or gets in case the argument is missing) the description for this 449Sets (or gets in case the argument is missing) the description for this
311process. This is just a free-form string you can associate with a process. 450coroutine. This is just a free-form string you can associate with a coroutine.
312 451
313=cut 452=cut
314 453
315sub desc { 454sub desc {
316 my $old = $_[0]{desc}; 455 my $old = $_[0]{desc};
318 $old; 457 $old;
319} 458}
320 459
321=back 460=back
322 461
462=head2 GLOBAL FUNCTIONS
463
464=over 4
465
466=item Coro::nready
467
468Returns the number of coroutines that are currently in the ready state,
469i.e. that can be switched to. The value C<0> means that the only runnable
470coroutine is the currently running one, so C<cede> would have no effect,
471and C<schedule> would cause a deadlock unless there is an idle handler
472that wakes up some coroutines.
473
474=item my $guard = Coro::guard { ... }
475
476This creates and returns a guard object. Nothing happens until the object
477gets destroyed, in which case the codeblock given as argument will be
478executed. This is useful to free locks or other resources in case of a
479runtime error or when the coroutine gets canceled, as in both cases the
480guard block will be executed. The guard object supports only one method,
481C<< ->cancel >>, which will keep the codeblock from being executed.
482
483Example: set some flag and clear it again when the coroutine gets canceled
484or the function returns:
485
486 sub do_something {
487 my $guard = Coro::guard { $busy = 0 };
488 $busy = 1;
489
490 # do something that requires $busy to be true
491 }
492
493=cut
494
495sub guard(&) {
496 bless \(my $cb = $_[0]), "Coro::guard"
497}
498
499sub Coro::guard::cancel {
500 ${$_[0]} = sub { };
501}
502
503sub Coro::guard::DESTROY {
504 ${$_[0]}->();
505}
506
507
508=item unblock_sub { ... }
509
510This utility function takes a BLOCK or code reference and "unblocks" it,
511returning the new coderef. This means that the new coderef will return
512immediately without blocking, returning nothing, while the original code
513ref will be called (with parameters) from within its own coroutine.
514
515The reason this function exists is that many event libraries (such as the
516venerable L<Event|Event> module) are not coroutine-safe (a weaker form
517of thread-safety). This means you must not block within event callbacks,
518otherwise you might suffer from crashes or worse.
519
520This function allows your callbacks to block by executing them in another
521coroutine where it is safe to block. One example where blocking is handy
522is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
523disk.
524
525In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
526creating event callbacks that want to block.
527
528=cut
529
530our @unblock_queue;
531
532# we create a special coro because we want to cede,
533# to reduce pressure on the coro pool (because most callbacks
534# return immediately and can be reused) and because we cannot cede
535# inside an event callback.
536our $unblock_scheduler = new Coro sub {
537 while () {
538 while (my $cb = pop @unblock_queue) {
539 # this is an inlined copy of async_pool
540 my $coro = (pop @pool or new Coro \&pool_handler);
541
542 $coro->{_invoke} = $cb;
543 $coro->ready;
544 cede; # for short-lived callbacks, this reduces pressure on the coro pool
545 }
546 schedule; # sleep well
547 }
548};
549$unblock_scheduler->desc ("[unblock_sub scheduler]");
550
551sub unblock_sub(&) {
552 my $cb = shift;
553
554 sub {
555 unshift @unblock_queue, [$cb, @_];
556 $unblock_scheduler->ready;
557 }
558}
559
560=back
561
323=cut 562=cut
324 563
3251; 5641;
326 565
327=head1 BUGS/LIMITATIONS 566=head1 BUGS/LIMITATIONS
328 567
329 - you must make very sure that no coro is still active on global 568 - you must make very sure that no coro is still active on global
330 destruction. very bad things might happen otherwise (usually segfaults). 569 destruction. very bad things might happen otherwise (usually segfaults).
331 570
332 - this module is not thread-safe. You should only ever use this module 571 - this module is not thread-safe. You should only ever use this module
333 from the same thread (this requirement might be losened in the future 572 from the same thread (this requirement might be loosened in the future
334 to allow per-thread schedulers, but Coro::State does not yet allow 573 to allow per-thread schedulers, but Coro::State does not yet allow
335 this). 574 this).
336 575
337=head1 SEE ALSO 576=head1 SEE ALSO
338 577
339L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 578Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
340L<Coro::Signal>, L<Coro::State>, L<Coro::Timer>, L<Coro::Event>, 579
341L<Coro::L<Coro::RWLock>, Handle>, L<Coro::Socket>. 580Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
581
582Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
583
584Embedding: L<Coro:MakeMaker>
342 585
343=head1 AUTHOR 586=head1 AUTHOR
344 587
345 Marc Lehmann <pcg@goof.com> 588 Marc Lehmann <schmorp@schmorp.de>
346 http://www.goof.com/pcg/marc/ 589 http://home.schmorp.de/
347 590
348=cut 591=cut
349 592

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