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Revision 1.53 by root, Tue May 27 01:15:26 2003 UTC vs.
Revision 1.131 by root, Thu Sep 20 12:24:42 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
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
51our $idle; # idle handler
52our $main; # main coroutine
53our $current; # current coroutine
54
41$VERSION = 0.7; 55our $VERSION = '3.7';
42 56
43@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
44%EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
45 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
46); 60);
47@EXPORT_OK = @{$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 (@_) {
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 {
166 $current->desc ("[coro manager]");
167
123 while() { 168 while () {
124 # by overwriting the state object with the manager we destroy it 169 (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) { 170 while @destroy;
130 my $coro = pop @destroy; 171
131 $coro->{status} ||= [];
132 $_->ready for @{delete $coro->{join} || []};
133 $coro->{_coro_state} = $manager->{_coro_state};
134 }
135 &schedule; 172 &schedule;
136 } 173 }
137}; 174};
138 175
176$manager->prio (PRIO_MAX);
177
139# static methods. not really. 178# static methods. not really.
140 179
141=back 180=back
142 181
143=head2 STATIC METHODS 182=head2 STATIC METHODS
144 183
145Static methods are actually functions that operate on the current process only. 184Static methods are actually functions that operate on the current coroutine only.
146 185
147=over 4 186=over 4
148 187
149=item async { ... } [@args...] 188=item async { ... } [@args...]
150 189
151Create a new asynchronous process and return it's process object 190Create a new asynchronous coroutine and return it's coroutine object
152(usually unused). When the sub returns the new process is automatically 191(usually unused). When the sub returns the new coroutine is automatically
153terminated. 192terminated.
193
194Calling C<exit> in a coroutine will do the same as calling exit outside
195the coroutine. Likewise, when the coroutine dies, the program will exit,
196just as it would in the main program.
154 197
155 # create a new coroutine that just prints its arguments 198 # create a new coroutine that just prints its arguments
156 async { 199 async {
157 print "@_\n"; 200 print "@_\n";
158 } 1,2,3,4; 201 } 1,2,3,4;
159 202
160The coderef you submit MUST NOT be a closure that refers to variables
161in an outer scope. This does NOT work. Pass arguments into it instead.
162
163=cut 203=cut
164 204
165sub async(&@) { 205sub async(&@) {
166 my $pid = new Coro @_; 206 my $coro = new Coro @_;
167 $manager->ready; # this ensures that the stack is cloned from the manager
168 $pid->ready; 207 $coro->ready;
169 $pid; 208 $coro
209}
210
211=item async_pool { ... } [@args...]
212
213Similar to C<async>, but uses a coroutine pool, so you should not call
214terminate or join (although you are allowed to), and you get a coroutine
215that might have executed other code already (which can be good or bad :).
216
217Also, the block is executed in an C<eval> context and a warning will be
218issued in case of an exception instead of terminating the program, as
219C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
220will not work in the expected way, unless you call terminate or cancel,
221which somehow defeats the purpose of pooling.
222
223The priority will be reset to C<0> after each job, otherwise the coroutine
224will be re-used "as-is".
225
226The pool size is limited to 8 idle coroutines (this can be adjusted by
227changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
228required.
229
230If you are concerned about pooled coroutines growing a lot because a
231single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {
232terminate }> once per second or so to slowly replenish the pool.
233
234=cut
235
236our $POOL_SIZE = 8;
237our $MAX_POOL_RSS = 64 * 1024;
238our @pool;
239
240sub pool_handler {
241 while () {
242 $current->{desc} = "[async_pool]";
243
244 eval {
245 my ($cb, @arg) = @{ delete $current->{_invoke} or return };
246 $cb->(@arg);
247 };
248 warn $@ if $@;
249
250 last if @pool >= $POOL_SIZE || $current->rss >= $MAX_POOL_RSS;
251
252 push @pool, $current;
253 $current->{desc} = "[async_pool idle]";
254 $current->save (Coro::State::SAVE_DEF);
255 $current->prio (0);
256 schedule;
257 }
258}
259
260sub async_pool(&@) {
261 # this is also inlined into the unlock_scheduler
262 my $coro = (pop @pool) || new Coro \&pool_handler;;
263
264 $coro->{_invoke} = [@_];
265 $coro->ready;
266
267 $coro
170} 268}
171 269
172=item schedule 270=item schedule
173 271
174Calls the scheduler. Please note that the current process will not be put 272Calls the scheduler. Please note that the current coroutine will not be put
175into the ready queue, so calling this function usually means you will 273into the ready queue, so calling this function usually means you will
176never be called again. 274never be called again unless something else (e.g. an event handler) calls
275ready.
177 276
178=cut 277The canonical way to wait on external events is this:
278
279 {
280 # remember current coroutine
281 my $current = $Coro::current;
282
283 # register a hypothetical event handler
284 on_event_invoke sub {
285 # wake up sleeping coroutine
286 $current->ready;
287 undef $current;
288 };
289
290 # call schedule until event occurred.
291 # in case we are woken up for other reasons
292 # (current still defined), loop.
293 Coro::schedule while $current;
294 }
179 295
180=item cede 296=item cede
181 297
182"Cede" to other processes. This function puts the current process into the 298"Cede" to other coroutines. This function puts the current coroutine into the
183ready queue and calls C<schedule>, which has the effect of giving up the 299ready queue and calls C<schedule>, which has the effect of giving up the
184current "timeslice" to other coroutines of the same or higher priority. 300current "timeslice" to other coroutines of the same or higher priority.
185 301
186=cut 302Returns true if at least one coroutine switch has happened.
303
304=item Coro::cede_notself
305
306Works like cede, but is not exported by default and will cede to any
307coroutine, regardless of priority, once.
308
309Returns true if at least one coroutine switch has happened.
187 310
188=item terminate [arg...] 311=item terminate [arg...]
189 312
190Terminates the current process. 313Terminates the current coroutine with the given status values (see L<cancel>).
191
192Future versions of this function will allow result arguments.
193 314
194=cut 315=cut
195 316
196sub terminate { 317sub terminate {
197 $current->{status} = [@_];
198 $current->cancel; 318 $current->cancel (@_);
199 &schedule;
200 die; # NORETURN
201} 319}
202 320
203=back 321=back
204 322
205# dynamic methods 323# dynamic methods
206 324
207=head2 PROCESS METHODS 325=head2 COROUTINE METHODS
208 326
209These are the methods you can call on process objects. 327These are the methods you can call on coroutine objects.
210 328
211=over 4 329=over 4
212 330
213=item new Coro \&sub [, @args...] 331=item new Coro \&sub [, @args...]
214 332
215Create a new process and return it. When the sub returns the process 333Create a new coroutine and return it. When the sub returns the coroutine
216automatically terminates as if C<terminate> with the returned values were 334automatically terminates as if C<terminate> with the returned values were
217called. To make the process run you must first put it into the ready queue 335called. To make the coroutine run you must first put it into the ready queue
218by calling the ready method. 336by calling the ready method.
219 337
220=cut 338See C<async> for additional discussion.
221 339
340=cut
341
222sub _newcoro { 342sub _run_coro {
223 terminate &{+shift}; 343 terminate &{+shift};
224} 344}
225 345
226sub new { 346sub new {
227 my $class = shift; 347 my $class = shift;
228 bless {
229 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
230 }, $class;
231}
232 348
233=item $process->ready 349 $class->SUPER::new (\&_run_coro, @_)
350}
234 351
235Put the given process into the ready queue. 352=item $success = $coroutine->ready
236 353
237=cut 354Put the given coroutine into the ready queue (according to it's priority)
355and return true. If the coroutine is already in the ready queue, do nothing
356and return false.
238 357
239=item $process->cancel 358=item $is_ready = $coroutine->is_ready
240 359
241Like C<terminate>, but terminates the specified process instead. 360Return wether the coroutine is currently the ready queue or not,
361
362=item $coroutine->cancel (arg...)
363
364Terminates the given coroutine and makes it return the given arguments as
365status (default: the empty list). Never returns if the coroutine is the
366current coroutine.
242 367
243=cut 368=cut
244 369
245sub cancel { 370sub cancel {
371 my $self = shift;
372 $self->{status} = [@_];
373
374 if ($current == $self) {
246 push @destroy, $_[0]; 375 push @destroy, $self;
247 $manager->ready; 376 $manager->ready;
248 &schedule if $current == $_[0]; 377 &schedule while 1;
378 } else {
379 $self->_cancel;
380 }
249} 381}
250 382
251=item $process->join 383=item $coroutine->join
252 384
253Wait until the coroutine terminates and return any values given to the 385Wait until the coroutine terminates and return any values given to the
254C<terminate> function. C<join> can be called multiple times from multiple 386C<terminate> or C<cancel> functions. C<join> can be called multiple times
255processes. 387from multiple coroutine.
256 388
257=cut 389=cut
258 390
259sub join { 391sub join {
260 my $self = shift; 392 my $self = shift;
393
261 unless ($self->{status}) { 394 unless ($self->{status}) {
262 push @{$self->{join}}, $current; 395 my $current = $current;
263 &schedule; 396
397 push @{$self->{destroy_cb}}, sub {
398 $current->ready;
399 undef $current;
400 };
401
402 &schedule while $current;
264 } 403 }
404
265 wantarray ? @{$self->{status}} : $self->{status}[0]; 405 wantarray ? @{$self->{status}} : $self->{status}[0];
266} 406}
267 407
408=item $coroutine->on_destroy (\&cb)
409
410Registers a callback that is called when this coroutine gets destroyed,
411but before it is joined. The callback gets passed the terminate arguments,
412if any.
413
414=cut
415
416sub on_destroy {
417 my ($self, $cb) = @_;
418
419 push @{ $self->{destroy_cb} }, $cb;
420}
421
268=item $oldprio = $process->prio($newprio) 422=item $oldprio = $coroutine->prio ($newprio)
269 423
270Sets (or gets, if the argument is missing) the priority of the 424Sets (or gets, if the argument is missing) the priority of the
271process. Higher priority processes get run before lower priority 425coroutine. Higher priority coroutines get run before lower priority
272processes. Priorities are small signed integers (currently -4 .. +3), 426coroutines. Priorities are small signed integers (currently -4 .. +3),
273that you can refer to using PRIO_xxx constants (use the import tag :prio 427that you can refer to using PRIO_xxx constants (use the import tag :prio
274to get then): 428to get then):
275 429
276 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 430 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
277 3 > 1 > 0 > -1 > -3 > -4 431 3 > 1 > 0 > -1 > -3 > -4
280 current->prio(PRIO_HIGH); 434 current->prio(PRIO_HIGH);
281 435
282The idle coroutine ($Coro::idle) always has a lower priority than any 436The idle coroutine ($Coro::idle) always has a lower priority than any
283existing coroutine. 437existing coroutine.
284 438
285Changing the priority of the current process will take effect immediately, 439Changing the priority of the current coroutine will take effect immediately,
286but changing the priority of processes in the ready queue (but not 440but changing the priority of coroutines in the ready queue (but not
287running) will only take effect after the next schedule (of that 441running) will only take effect after the next schedule (of that
288process). This is a bug that will be fixed in some future version. 442coroutine). This is a bug that will be fixed in some future version.
289 443
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) 444=item $newprio = $coroutine->nice ($change)
299 445
300Similar to C<prio>, but subtract the given value from the priority (i.e. 446Similar to C<prio>, but subtract the given value from the priority (i.e.
301higher values mean lower priority, just as in unix). 447higher values mean lower priority, just as in unix).
302 448
303=cut
304
305sub nice {
306 $_[0]{prio} -= $_[1];
307}
308
309=item $olddesc = $process->desc($newdesc) 449=item $olddesc = $coroutine->desc ($newdesc)
310 450
311Sets (or gets in case the argument is missing) the description for this 451Sets (or gets in case the argument is missing) the description for this
312process. This is just a free-form string you can associate with a process. 452coroutine. This is just a free-form string you can associate with a coroutine.
313 453
314=cut 454=cut
315 455
316sub desc { 456sub desc {
317 my $old = $_[0]{desc}; 457 my $old = $_[0]{desc};
319 $old; 459 $old;
320} 460}
321 461
322=back 462=back
323 463
464=head2 GLOBAL FUNCTIONS
465
466=over 4
467
468=item Coro::nready
469
470Returns the number of coroutines that are currently in the ready state,
471i.e. that can be switched to. The value C<0> means that the only runnable
472coroutine is the currently running one, so C<cede> would have no effect,
473and C<schedule> would cause a deadlock unless there is an idle handler
474that wakes up some coroutines.
475
476=item my $guard = Coro::guard { ... }
477
478This creates and returns a guard object. Nothing happens until the object
479gets destroyed, in which case the codeblock given as argument will be
480executed. This is useful to free locks or other resources in case of a
481runtime error or when the coroutine gets canceled, as in both cases the
482guard block will be executed. The guard object supports only one method,
483C<< ->cancel >>, which will keep the codeblock from being executed.
484
485Example: set some flag and clear it again when the coroutine gets canceled
486or the function returns:
487
488 sub do_something {
489 my $guard = Coro::guard { $busy = 0 };
490 $busy = 1;
491
492 # do something that requires $busy to be true
493 }
494
495=cut
496
497sub guard(&) {
498 bless \(my $cb = $_[0]), "Coro::guard"
499}
500
501sub Coro::guard::cancel {
502 ${$_[0]} = sub { };
503}
504
505sub Coro::guard::DESTROY {
506 ${$_[0]}->();
507}
508
509
510=item unblock_sub { ... }
511
512This utility function takes a BLOCK or code reference and "unblocks" it,
513returning the new coderef. This means that the new coderef will return
514immediately without blocking, returning nothing, while the original code
515ref will be called (with parameters) from within its own coroutine.
516
517The reason this function exists is that many event libraries (such as the
518venerable L<Event|Event> module) are not coroutine-safe (a weaker form
519of thread-safety). This means you must not block within event callbacks,
520otherwise you might suffer from crashes or worse.
521
522This function allows your callbacks to block by executing them in another
523coroutine where it is safe to block. One example where blocking is handy
524is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
525disk.
526
527In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
528creating event callbacks that want to block.
529
530=cut
531
532our @unblock_queue;
533
534# we create a special coro because we want to cede,
535# to reduce pressure on the coro pool (because most callbacks
536# return immediately and can be reused) and because we cannot cede
537# inside an event callback.
538our $unblock_scheduler = async {
539 $current->desc ("[unblock_sub scheduler]");
540 while () {
541 while (my $cb = pop @unblock_queue) {
542 # this is an inlined copy of async_pool
543 my $coro = (pop @pool or new Coro \&pool_handler);
544
545 $coro->{_invoke} = $cb;
546 $coro->ready;
547 cede; # for short-lived callbacks, this reduces pressure on the coro pool
548 }
549 schedule; # sleep well
550 }
551};
552
553sub unblock_sub(&) {
554 my $cb = shift;
555
556 sub {
557 unshift @unblock_queue, [$cb, @_];
558 $unblock_scheduler->ready;
559 }
560}
561
562=back
563
324=cut 564=cut
325 565
3261; 5661;
327 567
328=head1 BUGS/LIMITATIONS 568=head1 BUGS/LIMITATIONS
329 569
330 - you must make very sure that no coro is still active on global 570 - you must make very sure that no coro is still active on global
331 destruction. very bad things might happen otherwise (usually segfaults). 571 destruction. very bad things might happen otherwise (usually segfaults).
332 572
333 - this module is not thread-safe. You should only ever use this module 573 - this module is not thread-safe. You should only ever use this module
334 from the same thread (this requirement might be losened in the future 574 from the same thread (this requirement might be loosened in the future
335 to allow per-thread schedulers, but Coro::State does not yet allow 575 to allow per-thread schedulers, but Coro::State does not yet allow
336 this). 576 this).
337 577
338=head1 SEE ALSO 578=head1 SEE ALSO
339 579
340L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 580Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
341L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>, 581
342L<Coro::Handle>, L<Coro::Socket>. 582Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
583
584Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
585
586Embedding: L<Coro:MakeMaker>
343 587
344=head1 AUTHOR 588=head1 AUTHOR
345 589
346 Marc Lehmann <pcg@goof.com> 590 Marc Lehmann <schmorp@schmorp.de>
347 http://www.goof.com/pcg/marc/ 591 http://home.schmorp.de/
348 592
349=cut 593=cut
350 594

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