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Revision 1.42 by root, Tue Nov 6 20:37:20 2001 UTC vs.
Revision 1.142 by root, Tue Oct 2 23:16:24 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@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
28callchain, it's own set of lexicals and it's own set of perl's most 37its own set of lexicals and its own set of perls most important global
29important global variables. 38variables.
30 39
31=cut 40=cut
32 41
33package Coro; 42package Coro;
34 43
44use strict;
35no warnings qw(uninitialized); 45no warnings "uninitialized";
36 46
37use Coro::State; 47use Coro::State;
38 48
39use base Exporter; 49use base qw(Coro::State Exporter);
40 50
41$VERSION = 0.52; 51our $idle; # idle handler
52our $main; # main coroutine
53our $current; # current coroutine
42 54
55our $VERSION = '3.8';
56
43@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
44%EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
45 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
46); 60);
47@EXPORT_OK = @{$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<$main> (of course).
91 111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essential you are encouraged to use the
114C<Coro::current> function instead.
115
92=cut 116=cut
117
118$main->{desc} = "[main::]";
93 119
94# maybe some other module used Coro::Specific before... 120# maybe some other module used Coro::Specific before...
95if ($current) {
96 $main->{specific} = $current->{specific}; 121$main->{_specific} = $current->{_specific}
97} 122 if $current;
98 123
99our $current = $main; 124_set_current $main;
100 125
101sub current() { $current } 126sub current() { $current }
102 127
103=item $idle 128=item $idle
104 129
105The coroutine to switch to when no other coroutine is running. The default 130A callback that is called whenever the scheduler finds no ready coroutines
106implementation 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.
107 133
108=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.
109 137
110# should be done using priorities :( 138Please note that if your callback recursively invokes perl (e.g. for event
111our $idle = new Coro sub { 139handlers), then it must be prepared to be called recursively.
112 print STDERR "FATAL: deadlock detected\n"; 140
113 exit(51); 141=cut
142
143$idle = sub {
144 require Carp;
145 Carp::croak ("FATAL: deadlock detected");
114}; 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->{_on_destroy}) || []};
158}
115 159
116# this coroutine is necessary because a coroutine 160# this coroutine is necessary because a coroutine
117# cannot destroy itself. 161# cannot destroy itself.
118my @destroy; 162my @destroy;
119my $manager; 163my $manager;
164
120$manager = new Coro sub { 165$manager = new Coro sub {
121 while() { 166 while () {
122 # by overwriting the state object with the manager we destroy it 167 (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) { 168 while @destroy;
128 my $coro = pop @destroy; 169
129 $coro->{status} ||= [];
130 $_->ready for @{delete $coro->{join} || []};
131 $coro->{_coro_state} = $manager->{_coro_state};
132 }
133 &schedule; 170 &schedule;
134 } 171 }
135}; 172};
173$manager->desc ("[coro manager]");
174$manager->prio (PRIO_MAX);
136 175
137# static methods. not really. 176# static methods. not really.
138 177
178=back
179
139=head2 STATIC METHODS 180=head2 STATIC METHODS
140 181
141Static methods are actually functions that operate on the current process only. 182Static methods are actually functions that operate on the current coroutine only.
142 183
143=over 4 184=over 4
144 185
145=item async { ... } [@args...] 186=item async { ... } [@args...]
146 187
147Create a new asynchronous process and return it's process object 188Create a new asynchronous coroutine and return it's coroutine object
148(usually unused). When the sub returns the new process is automatically 189(usually unused). When the sub returns the new coroutine is automatically
149terminated. 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.
150 195
151 # create a new coroutine that just prints its arguments 196 # create a new coroutine that just prints its arguments
152 async { 197 async {
153 print "@_\n"; 198 print "@_\n";
154 } 1,2,3,4; 199 } 1,2,3,4;
155 200
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 201=cut
160 202
161sub async(&@) { 203sub async(&@) {
162 my $pid = new Coro @_; 204 my $coro = new Coro @_;
163 $manager->ready; # this ensures that the stack is cloned from the manager
164 $pid->ready; 205 $coro->ready;
165 $pid; 206 $coro
207}
208
209=item async_pool { ... } [@args...]
210
211Similar to C<async>, but uses a coroutine pool, so you should not call
212terminate or join (although you are allowed to), and you get a coroutine
213that might have executed other code already (which can be good or bad :).
214
215Also, the block is executed in an C<eval> context and a warning will be
216issued in case of an exception instead of terminating the program, as
217C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
218will not work in the expected way, unless you call terminate or cancel,
219which somehow defeats the purpose of pooling.
220
221The priority will be reset to C<0> after each job, otherwise the coroutine
222will be re-used "as-is".
223
224The pool size is limited to 8 idle coroutines (this can be adjusted by
225changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
226required.
227
228If you are concerned about pooled coroutines growing a lot because a
229single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
230{ terminate }> once per second or so to slowly replenish the pool. In
231addition to that, when the stacks used by a handler grows larger than 16kb
232(adjustable with $Coro::POOL_RSS) it will also exit.
233
234=cut
235
236our $POOL_SIZE = 8;
237our $POOL_RSS = 16 * 1024;
238our @async_pool;
239
240sub pool_handler {
241 my $cb;
242
243 while () {
244 eval {
245 while () {
246 _pool_1 $cb;
247 &$cb;
248 _pool_2 $cb;
249 &schedule;
250 }
251 };
252
253 last if $@ eq "\3terminate\2\n";
254 warn $@ if $@;
255 }
256}
257
258sub async_pool(&@) {
259 # this is also inlined into the unlock_scheduler
260 my $coro = (pop @async_pool) || new Coro \&pool_handler;
261
262 $coro->{_invoke} = [@_];
263 $coro->ready;
264
265 $coro
166} 266}
167 267
168=item schedule 268=item schedule
169 269
170Calls 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
171into the ready queue, so calling this function usually means you will 271into the ready queue, so calling this function usually means you will
172never be called again. 272never be called again unless something else (e.g. an event handler) calls
273ready.
173 274
174=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 }
175 293
176=item cede 294=item cede
177 295
178"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
179ready 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
180current "timeslice" to other coroutines of the same or higher priority. 298current "timeslice" to other coroutines of the same or higher priority.
181 299
182=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.
183 308
184=item terminate [arg...] 309=item terminate [arg...]
185 310
186Terminates the current process. 311Terminates the current coroutine with the given status values (see L<cancel>).
187 312
188Future versions of this function will allow result arguments. 313=item killall
314
315Kills/terminates/cancels all coroutines except the currently running
316one. This is useful after a fork, either in the child or the parent, as
317usually only one of them should inherit the running coroutines.
189 318
190=cut 319=cut
191 320
192sub terminate { 321sub terminate {
193 $current->{status} = [@_];
194 $current->cancel; 322 $current->cancel (@_);
195 &schedule; 323}
196 die; # NORETURN 324
325sub killall {
326 for (Coro::State::list) {
327 $_->cancel
328 if $_ != $current && UNIVERSAL::isa $_, "Coro";
329 }
197} 330}
198 331
199=back 332=back
200 333
201# dynamic methods 334# dynamic methods
202 335
203=head2 PROCESS METHODS 336=head2 COROUTINE METHODS
204 337
205These are the methods you can call on process objects. 338These are the methods you can call on coroutine objects.
206 339
207=over 4 340=over 4
208 341
209=item new Coro \&sub [, @args...] 342=item new Coro \&sub [, @args...]
210 343
211Create a new process and return it. When the sub returns the process 344Create a new coroutine and return it. When the sub returns the coroutine
212automatically terminates as if C<terminate> with the returned values were 345automatically 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 346called. To make the coroutine run you must first put it into the ready queue
214by calling the ready method. 347by calling the ready method.
215 348
216=cut 349See C<async> for additional discussion.
217 350
351=cut
352
218sub _newcoro { 353sub _run_coro {
219 terminate &{+shift}; 354 terminate &{+shift};
220} 355}
221 356
222sub new { 357sub new {
223 my $class = shift; 358 my $class = shift;
224 bless {
225 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
226 }, $class;
227}
228 359
229=item $process->ready 360 $class->SUPER::new (\&_run_coro, @_)
361}
230 362
231Put the given process into the ready queue. 363=item $success = $coroutine->ready
232 364
233=cut 365Put the given coroutine into the ready queue (according to it's priority)
366and return true. If the coroutine is already in the ready queue, do nothing
367and return false.
234 368
235=item $process->cancel 369=item $is_ready = $coroutine->is_ready
236 370
237Like C<terminate>, but terminates the specified process instead. 371Return wether the coroutine is currently the ready queue or not,
372
373=item $coroutine->cancel (arg...)
374
375Terminates the given coroutine and makes it return the given arguments as
376status (default: the empty list). Never returns if the coroutine is the
377current coroutine.
238 378
239=cut 379=cut
240 380
241sub cancel { 381sub cancel {
382 my $self = shift;
383 $self->{_status} = [@_];
384
385 if ($current == $self) {
242 push @destroy, $_[0]; 386 push @destroy, $self;
243 $manager->ready; 387 $manager->ready;
244 &schedule if $current == $_[0]; 388 &schedule while 1;
389 } else {
390 $self->_cancel;
391 }
245} 392}
246 393
247=item $process->join 394=item $coroutine->join
248 395
249Wait until the coroutine terminates and return any values given to the 396Wait until the coroutine terminates and return any values given to the
250C<terminate> function. C<join> can be called multiple times from multiple 397C<terminate> or C<cancel> functions. C<join> can be called multiple times
251processes. 398from multiple coroutine.
252 399
253=cut 400=cut
254 401
255sub join { 402sub join {
256 my $self = shift; 403 my $self = shift;
404
257 unless ($self->{status}) { 405 unless ($self->{_status}) {
258 push @{$self->{join}}, $current; 406 my $current = $current;
259 &schedule; 407
408 push @{$self->{_on_destroy}}, sub {
409 $current->ready;
410 undef $current;
411 };
412
413 &schedule while $current;
260 } 414 }
415
261 wantarray ? @{$self->{status}} : $self->{status}[0]; 416 wantarray ? @{$self->{_status}} : $self->{_status}[0];
262} 417}
263 418
419=item $coroutine->on_destroy (\&cb)
420
421Registers a callback that is called when this coroutine gets destroyed,
422but before it is joined. The callback gets passed the terminate arguments,
423if any.
424
425=cut
426
427sub on_destroy {
428 my ($self, $cb) = @_;
429
430 push @{ $self->{_on_destroy} }, $cb;
431}
432
264=item $oldprio = $process->prio($newprio) 433=item $oldprio = $coroutine->prio ($newprio)
265 434
266Sets (or gets, if the argument is missing) the priority of the 435Sets (or gets, if the argument is missing) the priority of the
267process. Higher priority processes get run before lower priority 436coroutine. Higher priority coroutines get run before lower priority
268processes. Priorities are smalled signed integer (currently -4 .. +3), 437coroutines. Priorities are small signed integers (currently -4 .. +3),
269that you can refer to using PRIO_xxx constants (use the import tag :prio 438that you can refer to using PRIO_xxx constants (use the import tag :prio
270to get then): 439to get then):
271 440
272 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 441 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
273 3 > 1 > 0 > -1 > -3 > -4 442 3 > 1 > 0 > -1 > -3 > -4
276 current->prio(PRIO_HIGH); 445 current->prio(PRIO_HIGH);
277 446
278The idle coroutine ($Coro::idle) always has a lower priority than any 447The idle coroutine ($Coro::idle) always has a lower priority than any
279existing coroutine. 448existing coroutine.
280 449
281Changing the priority of the current process will take effect immediately, 450Changing the priority of the current coroutine will take effect immediately,
282but changing the priority of processes in the ready queue (but not 451but changing the priority of coroutines in the ready queue (but not
283running) will only take effect after the next schedule (of that 452running) will only take effect after the next schedule (of that
284process). This is a bug that will be fixed in some future version. 453coroutine). This is a bug that will be fixed in some future version.
285 454
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) 455=item $newprio = $coroutine->nice ($change)
295 456
296Similar to C<prio>, but subtract the given value from the priority (i.e. 457Similar to C<prio>, but subtract the given value from the priority (i.e.
297higher values mean lower priority, just as in unix). 458higher values mean lower priority, just as in unix).
298 459
299=cut
300
301sub nice {
302 $_[0]{prio} -= $_[1];
303}
304
305=item $olddesc = $process->desc($newdesc) 460=item $olddesc = $coroutine->desc ($newdesc)
306 461
307Sets (or gets in case the argument is missing) the description for this 462Sets (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. 463coroutine. This is just a free-form string you can associate with a coroutine.
464
465This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
466can modify this member directly if you wish.
309 467
310=cut 468=cut
311 469
312sub desc { 470sub desc {
313 my $old = $_[0]{desc}; 471 my $old = $_[0]{desc};
315 $old; 473 $old;
316} 474}
317 475
318=back 476=back
319 477
478=head2 GLOBAL FUNCTIONS
479
480=over 4
481
482=item Coro::nready
483
484Returns the number of coroutines that are currently in the ready state,
485i.e. that can be switched to. The value C<0> means that the only runnable
486coroutine is the currently running one, so C<cede> would have no effect,
487and C<schedule> would cause a deadlock unless there is an idle handler
488that wakes up some coroutines.
489
490=item my $guard = Coro::guard { ... }
491
492This creates and returns a guard object. Nothing happens until the object
493gets destroyed, in which case the codeblock given as argument will be
494executed. This is useful to free locks or other resources in case of a
495runtime error or when the coroutine gets canceled, as in both cases the
496guard block will be executed. The guard object supports only one method,
497C<< ->cancel >>, which will keep the codeblock from being executed.
498
499Example: set some flag and clear it again when the coroutine gets canceled
500or the function returns:
501
502 sub do_something {
503 my $guard = Coro::guard { $busy = 0 };
504 $busy = 1;
505
506 # do something that requires $busy to be true
507 }
508
509=cut
510
511sub guard(&) {
512 bless \(my $cb = $_[0]), "Coro::guard"
513}
514
515sub Coro::guard::cancel {
516 ${$_[0]} = sub { };
517}
518
519sub Coro::guard::DESTROY {
520 ${$_[0]}->();
521}
522
523
524=item unblock_sub { ... }
525
526This utility function takes a BLOCK or code reference and "unblocks" it,
527returning the new coderef. This means that the new coderef will return
528immediately without blocking, returning nothing, while the original code
529ref will be called (with parameters) from within its own coroutine.
530
531The reason this function exists is that many event libraries (such as the
532venerable L<Event|Event> module) are not coroutine-safe (a weaker form
533of thread-safety). This means you must not block within event callbacks,
534otherwise you might suffer from crashes or worse.
535
536This function allows your callbacks to block by executing them in another
537coroutine where it is safe to block. One example where blocking is handy
538is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
539disk.
540
541In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
542creating event callbacks that want to block.
543
544=cut
545
546our @unblock_queue;
547
548# we create a special coro because we want to cede,
549# to reduce pressure on the coro pool (because most callbacks
550# return immediately and can be reused) and because we cannot cede
551# inside an event callback.
552our $unblock_scheduler = new Coro sub {
553 while () {
554 while (my $cb = pop @unblock_queue) {
555 # this is an inlined copy of async_pool
556 my $coro = (pop @async_pool) || new Coro \&pool_handler;
557
558 $coro->{_invoke} = $cb;
559 $coro->ready;
560 cede; # for short-lived callbacks, this reduces pressure on the coro pool
561 }
562 schedule; # sleep well
563 }
564};
565$unblock_scheduler->desc ("[unblock_sub scheduler]");
566
567sub unblock_sub(&) {
568 my $cb = shift;
569
570 sub {
571 unshift @unblock_queue, [$cb, @_];
572 $unblock_scheduler->ready;
573 }
574}
575
576=back
577
320=cut 578=cut
321 579
3221; 5801;
323 581
324=head1 BUGS/LIMITATIONS 582=head1 BUGS/LIMITATIONS
325 583
326 - you must make very sure that no coro is still active on global destruction. 584 - you must make very sure that no coro is still active on global
327 very bad things might happen otherwise (usually segfaults). 585 destruction. very bad things might happen otherwise (usually segfaults).
586
328 - this module is not thread-safe. You should only ever use this module from 587 - 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 588 from the same thread (this requirement might be loosened in the future
330 allow per-thread schedulers, but Coro::State does not yet allow this). 589 to allow per-thread schedulers, but Coro::State does not yet allow
590 this).
331 591
332=head1 SEE ALSO 592=head1 SEE ALSO
333 593
334L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 594Support/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>, 595
336L<Coro::Handle>, L<Coro::Socket>. 596Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
597
598Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
599
600Embedding: L<Coro:MakeMaker>
337 601
338=head1 AUTHOR 602=head1 AUTHOR
339 603
340 Marc Lehmann <pcg@goof.com> 604 Marc Lehmann <schmorp@schmorp.de>
341 http://www.goof.com/pcg/marc/ 605 http://home.schmorp.de/
342 606
343=cut 607=cut
344 608

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