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Revision 1.19 by root, Sat Jul 21 03:44:06 2001 UTC vs.
Revision 1.178 by root, Thu Apr 17 22:33:10 2008 UTC

6 6
7 use Coro; 7 use Coro;
8 8
9 async { 9 async {
10 # some asynchronous thread of execution 10 # some asynchronous thread of execution
11 print "2\n";
12 cede; # yield back to main
13 print "4\n";
11 }; 14 };
15 print "1\n";
16 cede; # yield to coroutine
17 print "3\n";
18 cede; # and again
12 19
13 # alternatively create an async process like this: 20 # use locking
21 my $lock = new Coro::Semaphore;
22 my $locked;
14 23
15 sub some_func : Coro { 24 $lock->down;
16 # some more async code 25 $locked = 1;
17 } 26 $lock->up;
18
19 yield;
20 27
21=head1 DESCRIPTION 28=head1 DESCRIPTION
22 29
23This module collection manages coroutines. Coroutines are similar to 30This module collection manages coroutines. Coroutines are similar
24Threads but don't run in parallel. 31to threads but don't run in parallel at the same time even on SMP
32machines. The specific flavor of coroutine used in this module also
33guarantees you that it will not switch between coroutines unless
34necessary, at easily-identified points in your program, so locking and
35parallel access are rarely an issue, making coroutine programming much
36safer than threads programming.
25 37
26This module is still experimental, see the BUGS section below. 38(Perl, however, does not natively support real threads but instead does a
39very slow and memory-intensive emulation of processes using threads. This
40is a performance win on Windows machines, and a loss everywhere else).
41
42In this module, coroutines are defined as "callchain + lexical variables +
43@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
44its own set of lexicals and its own set of perls most important global
45variables (see L<Coro::State> for more configuration).
27 46
28=cut 47=cut
29 48
30package Coro; 49package Coro;
31 50
51use strict;
52no warnings "uninitialized";
53
32use Coro::State; 54use Coro::State;
33 55
34use base Exporter; 56use base qw(Coro::State Exporter);
35 57
36$VERSION = 0.09; 58our $idle; # idle handler
59our $main; # main coroutine
60our $current; # current coroutine
37 61
62our $VERSION = '4.51';
63
38@EXPORT = qw(async yield schedule terminate current); 64our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
39@EXPORT_OK = qw($current); 65our %EXPORT_TAGS = (
66 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
67);
68our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
40 69
41{ 70{
42 use subs 'async';
43
44 my @async; 71 my @async;
72 my $init;
45 73
46 # this way of handling attributes simply is NOT scalable ;() 74 # this way of handling attributes simply is NOT scalable ;()
47 sub import { 75 sub import {
76 no strict 'refs';
77
48 Coro->export_to_level(1, @_); 78 Coro->export_to_level (1, @_);
79
49 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; 80 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
50 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { 81 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
51 my ($package, $ref) = (shift, shift); 82 my ($package, $ref) = (shift, shift);
52 my @attrs; 83 my @attrs;
53 for (@_) { 84 for (@_) {
54 if ($_ eq "Coro") { 85 if ($_ eq "Coro") {
55 push @async, $ref; 86 push @async, $ref;
87 unless ($init++) {
88 eval q{
89 sub INIT {
90 &async(pop @async) while @async;
91 }
92 };
93 }
56 } else { 94 } else {
57 push @attrs, $_; 95 push @attrs, $_;
58 } 96 }
59 } 97 }
60 return $old ? $old->($package, $ref, @attrs) : @attrs; 98 return $old ? $old->($package, $ref, @attrs) : @attrs;
61 }; 99 };
62 } 100 }
63 101
64 sub INIT {
65 async pop @async while @async;
66 }
67} 102}
103
104=over 4
68 105
69=item $main 106=item $main
70 107
71This coroutine represents the main program. 108This coroutine represents the main program.
72 109
73=cut 110=cut
74 111
75our $main = new Coro; 112$main = new Coro;
76 113
77=item $current (or as function: current) 114=item $current (or as function: current)
78 115
79The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). 116The current coroutine (the last coroutine switched to). The initial value
117is C<$main> (of course).
80 118
119This variable is B<strictly> I<read-only>. It is provided for performance
120reasons. If performance is not essential you are encouraged to use the
121C<Coro::current> function instead.
122
81=cut 123=cut
124
125$main->{desc} = "[main::]";
82 126
83# maybe some other module used Coro::Specific before... 127# maybe some other module used Coro::Specific before...
84if ($current) {
85 $main->{specific} = $current->{specific}; 128$main->{_specific} = $current->{_specific}
86} 129 if $current;
87 130
88our $current = $main; 131_set_current $main;
89 132
90sub current() { $current } 133sub current() { $current }
91 134
92=item $idle 135=item $idle
93 136
94The coroutine to switch to when no other coroutine is running. The default 137A callback that is called whenever the scheduler finds no ready coroutines
95implementation prints "FATAL: deadlock detected" and exits. 138to run. The default implementation prints "FATAL: deadlock detected" and
139exits, because the program has no other way to continue.
96 140
97=cut 141This hook is overwritten by modules such as C<Coro::Timer> and
142C<Coro::Event> to wait on an external event that hopefully wake up a
143coroutine so the scheduler can run it.
98 144
99# should be done using priorities :( 145Please note that if your callback recursively invokes perl (e.g. for event
100our $idle = new Coro sub { 146handlers), then it must be prepared to be called recursively itself.
101 print STDERR "FATAL: deadlock detected\n"; 147
102 exit(51); 148=cut
149
150$idle = sub {
151 require Carp;
152 Carp::croak ("FATAL: deadlock detected");
103}; 153};
104 154
105# we really need priorities... 155sub _cancel {
106my @ready; # the ready queue. hehe, rather broken ;) 156 my ($self) = @_;
107 157
108# static methods. not really. 158 # free coroutine data and mark as destructed
159 $self->_destroy
160 or return;
161
162 # call all destruction callbacks
163 $_->(@{$self->{_status}})
164 for @{(delete $self->{_on_destroy}) || []};
165}
166
167# this coroutine is necessary because a coroutine
168# cannot destroy itself.
169my @destroy;
170my $manager;
171
172$manager = new Coro sub {
173 while () {
174 (shift @destroy)->_cancel
175 while @destroy;
176
177 &schedule;
178 }
179};
180$manager->desc ("[coro manager]");
181$manager->prio (PRIO_MAX);
182
183=back
109 184
110=head2 STATIC METHODS 185=head2 STATIC METHODS
111 186
112Static methods are actually functions that operate on the current process only. 187Static methods are actually functions that operate on the current coroutine only.
113 188
114=over 4 189=over 4
115 190
116=item async { ... } [@args...] 191=item async { ... } [@args...]
117 192
118Create a new asynchronous process and return it's process object 193Create a new asynchronous coroutine and return it's coroutine object
119(usually unused). When the sub returns the new process is automatically 194(usually unused). When the sub returns the new coroutine is automatically
120terminated. 195terminated.
196
197See the C<Coro::State::new> constructor for info about the coroutine
198environment in which coroutines run.
199
200Calling C<exit> in a coroutine will do the same as calling exit outside
201the coroutine. Likewise, when the coroutine dies, the program will exit,
202just as it would in the main program.
121 203
122 # create a new coroutine that just prints its arguments 204 # create a new coroutine that just prints its arguments
123 async { 205 async {
124 print "@_\n"; 206 print "@_\n";
125 } 1,2,3,4; 207 } 1,2,3,4;
126 208
127The coderef you submit MUST NOT be a closure that refers to variables
128in an outer scope. This does NOT work. Pass arguments into it instead.
129
130=cut 209=cut
131 210
132sub async(&@) { 211sub async(&@) {
133 my $pid = new Coro @_; 212 my $coro = new Coro @_;
134 $pid->ready; 213 $coro->ready;
135 $pid; 214 $coro
215}
216
217=item async_pool { ... } [@args...]
218
219Similar to C<async>, but uses a coroutine pool, so you should not call
220terminate or join (although you are allowed to), and you get a coroutine
221that might have executed other code already (which can be good or bad :).
222
223Also, the block is executed in an C<eval> context and a warning will be
224issued in case of an exception instead of terminating the program, as
225C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
226will not work in the expected way, unless you call terminate or cancel,
227which somehow defeats the purpose of pooling.
228
229The priority will be reset to C<0> after each job, tracing will be
230disabled, the description will be reset and the default output filehandle
231gets restored, so you can change alkl these. Otherwise the coroutine will
232be re-used "as-is": most notably if you change other per-coroutine global
233stuff such as C<$/> you need to revert that change, which is most simply
234done by using local as in C< local $/ >.
235
236The pool size is limited to 8 idle coroutines (this can be adjusted by
237changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
238required.
239
240If you are concerned about pooled coroutines growing a lot because a
241single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
242{ terminate }> once per second or so to slowly replenish the pool. In
243addition to that, when the stacks used by a handler grows larger than 16kb
244(adjustable with $Coro::POOL_RSS) it will also exit.
245
246=cut
247
248our $POOL_SIZE = 8;
249our $POOL_RSS = 16 * 1024;
250our @async_pool;
251
252sub pool_handler {
253 my $cb;
254
255 while () {
256 eval {
257 while () {
258 _pool_1 $cb;
259 &$cb;
260 _pool_2 $cb;
261 &schedule;
262 }
263 };
264
265 last if $@ eq "\3async_pool terminate\2\n";
266 warn $@ if $@;
267 }
268}
269
270sub async_pool(&@) {
271 # this is also inlined into the unlock_scheduler
272 my $coro = (pop @async_pool) || new Coro \&pool_handler;
273
274 $coro->{_invoke} = [@_];
275 $coro->ready;
276
277 $coro
136} 278}
137 279
138=item schedule 280=item schedule
139 281
140Calls the scheduler. Please note that the current process will not be put 282Calls the scheduler. Please note that the current coroutine will not be put
141into the ready queue, so calling this function usually means you will 283into the ready queue, so calling this function usually means you will
142never be called again. 284never be called again unless something else (e.g. an event handler) calls
285ready.
143 286
144=cut 287The canonical way to wait on external events is this:
145 288
146my $prev; 289 {
290 # remember current coroutine
291 my $current = $Coro::current;
147 292
148sub schedule { 293 # register a hypothetical event handler
149 # should be done using priorities :( 294 on_event_invoke sub {
150 ($prev, $current) = ($current, shift @ready || $idle); 295 # wake up sleeping coroutine
151 Coro::State::transfer($prev, $current);
152}
153
154=item yield
155
156Yield to other processes. This function puts the current process into the
157ready queue and calls C<schedule>.
158
159=cut
160
161sub yield {
162 $current->ready; 296 $current->ready;
163 &schedule; 297 undef $current;
164} 298 };
165 299
300 # call schedule until event occurred.
301 # in case we are woken up for other reasons
302 # (current still defined), loop.
303 Coro::schedule while $current;
304 }
305
306=item cede
307
308"Cede" to other coroutines. This function puts the current coroutine into the
309ready queue and calls C<schedule>, which has the effect of giving up the
310current "timeslice" to other coroutines of the same or higher priority.
311
312=item Coro::cede_notself
313
314Works like cede, but is not exported by default and will cede to any
315coroutine, regardless of priority, once.
316
166=item terminate 317=item terminate [arg...]
167 318
168Terminates the current process. 319Terminates the current coroutine with the given status values (see L<cancel>).
169 320
170Future versions of this function will allow result arguments. 321=item killall
322
323Kills/terminates/cancels all coroutines except the currently running
324one. This is useful after a fork, either in the child or the parent, as
325usually only one of them should inherit the running coroutines.
171 326
172=cut 327=cut
173 328
174sub terminate { 329sub terminate {
175 $current->{_results} = [@_]; 330 $current->cancel (@_);
176 &schedule; 331}
332
333sub killall {
334 for (Coro::State::list) {
335 $_->cancel
336 if $_ != $current && UNIVERSAL::isa $_, "Coro";
337 }
177} 338}
178 339
179=back 340=back
180 341
181# dynamic methods
182
183=head2 PROCESS METHODS 342=head2 COROUTINE METHODS
184 343
185These are the methods you can call on process objects. 344These are the methods you can call on coroutine objects.
186 345
187=over 4 346=over 4
188 347
189=item new Coro \&sub [, @args...] 348=item new Coro \&sub [, @args...]
190 349
191Create a new process and return it. When the sub returns the process 350Create a new coroutine and return it. When the sub returns the coroutine
192automatically terminates. To start the process you must first put it into 351automatically terminates as if C<terminate> with the returned values were
352called. To make the coroutine run you must first put it into the ready queue
193the ready queue by calling the ready method. 353by calling the ready method.
194 354
195The coderef you submit MUST NOT be a closure that refers to variables 355See C<async> and C<Coro::State::new> for additional info about the
196in an outer scope. This does NOT work. Pass arguments into it instead. 356coroutine environment.
197 357
198=cut 358=cut
199 359
200sub _newcoro { 360sub _run_coro {
201 terminate &{+shift}; 361 terminate &{+shift};
202} 362}
203 363
204sub new { 364sub new {
205 my $class = shift; 365 my $class = shift;
206 bless {
207 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
208 }, $class;
209}
210 366
211=item $process->ready 367 $class->SUPER::new (\&_run_coro, @_)
368}
212 369
213Put the current process into the ready queue. 370=item $success = $coroutine->ready
214 371
215=cut 372Put the given coroutine into the ready queue (according to it's priority)
373and return true. If the coroutine is already in the ready queue, do nothing
374and return false.
216 375
217sub ready { 376=item $is_ready = $coroutine->is_ready
218 push @ready, $_[0]; 377
378Return wether the coroutine is currently the ready queue or not,
379
380=item $coroutine->cancel (arg...)
381
382Terminates the given coroutine and makes it return the given arguments as
383status (default: the empty list). Never returns if the coroutine is the
384current coroutine.
385
386=cut
387
388sub cancel {
389 my $self = shift;
390 $self->{_status} = [@_];
391
392 if ($current == $self) {
393 push @destroy, $self;
394 $manager->ready;
395 &schedule while 1;
396 } else {
397 $self->_cancel;
398 }
399}
400
401=item $coroutine->join
402
403Wait until the coroutine terminates and return any values given to the
404C<terminate> or C<cancel> functions. C<join> can be called concurrently
405from multiple coroutines.
406
407=cut
408
409sub join {
410 my $self = shift;
411
412 unless ($self->{_status}) {
413 my $current = $current;
414
415 push @{$self->{_on_destroy}}, sub {
416 $current->ready;
417 undef $current;
418 };
419
420 &schedule while $current;
421 }
422
423 wantarray ? @{$self->{_status}} : $self->{_status}[0];
424}
425
426=item $coroutine->on_destroy (\&cb)
427
428Registers a callback that is called when this coroutine gets destroyed,
429but before it is joined. The callback gets passed the terminate arguments,
430if any.
431
432=cut
433
434sub on_destroy {
435 my ($self, $cb) = @_;
436
437 push @{ $self->{_on_destroy} }, $cb;
438}
439
440=item $oldprio = $coroutine->prio ($newprio)
441
442Sets (or gets, if the argument is missing) the priority of the
443coroutine. Higher priority coroutines get run before lower priority
444coroutines. Priorities are small signed integers (currently -4 .. +3),
445that you can refer to using PRIO_xxx constants (use the import tag :prio
446to get then):
447
448 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
449 3 > 1 > 0 > -1 > -3 > -4
450
451 # set priority to HIGH
452 current->prio(PRIO_HIGH);
453
454The idle coroutine ($Coro::idle) always has a lower priority than any
455existing coroutine.
456
457Changing the priority of the current coroutine will take effect immediately,
458but changing the priority of coroutines in the ready queue (but not
459running) will only take effect after the next schedule (of that
460coroutine). This is a bug that will be fixed in some future version.
461
462=item $newprio = $coroutine->nice ($change)
463
464Similar to C<prio>, but subtract the given value from the priority (i.e.
465higher values mean lower priority, just as in unix).
466
467=item $olddesc = $coroutine->desc ($newdesc)
468
469Sets (or gets in case the argument is missing) the description for this
470coroutine. This is just a free-form string you can associate with a coroutine.
471
472This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
473can modify this member directly if you wish.
474
475=item $coroutine->throw ([$scalar])
476
477If C<$throw> is specified and defined, it will be thrown as an exception
478inside the coroutine at the next convinient point in time (usually after
479it gains control at the next schedule/transfer/cede). Otherwise clears the
480exception object.
481
482The exception object will be thrown "as is" with the specified scalar in
483C<$@>, i.e. if it is a string, no line number or newline will be appended
484(unlike with C<die>).
485
486This can be used as a softer means than C<cancel> to ask a coroutine to
487end itself, although there is no guarentee that the exception will lead to
488termination, and if the exception isn't caught it might well end the whole
489program.
490
491=cut
492
493sub desc {
494 my $old = $_[0]{desc};
495 $_[0]{desc} = $_[1] if @_ > 1;
496 $old;
219} 497}
220 498
221=back 499=back
222 500
501=head2 GLOBAL FUNCTIONS
502
503=over 4
504
505=item Coro::nready
506
507Returns the number of coroutines that are currently in the ready state,
508i.e. that can be switched to. The value C<0> means that the only runnable
509coroutine is the currently running one, so C<cede> would have no effect,
510and C<schedule> would cause a deadlock unless there is an idle handler
511that wakes up some coroutines.
512
513=item my $guard = Coro::guard { ... }
514
515This creates and returns a guard object. Nothing happens until the object
516gets destroyed, in which case the codeblock given as argument will be
517executed. This is useful to free locks or other resources in case of a
518runtime error or when the coroutine gets canceled, as in both cases the
519guard block will be executed. The guard object supports only one method,
520C<< ->cancel >>, which will keep the codeblock from being executed.
521
522Example: set some flag and clear it again when the coroutine gets canceled
523or the function returns:
524
525 sub do_something {
526 my $guard = Coro::guard { $busy = 0 };
527 $busy = 1;
528
529 # do something that requires $busy to be true
530 }
531
532=cut
533
534sub guard(&) {
535 bless \(my $cb = $_[0]), "Coro::guard"
536}
537
538sub Coro::guard::cancel {
539 ${$_[0]} = sub { };
540}
541
542sub Coro::guard::DESTROY {
543 ${$_[0]}->();
544}
545
546
547=item unblock_sub { ... }
548
549This utility function takes a BLOCK or code reference and "unblocks" it,
550returning the new coderef. This means that the new coderef will return
551immediately without blocking, returning nothing, while the original code
552ref will be called (with parameters) from within its own coroutine.
553
554The reason this function exists is that many event libraries (such as the
555venerable L<Event|Event> module) are not coroutine-safe (a weaker form
556of thread-safety). This means you must not block within event callbacks,
557otherwise you might suffer from crashes or worse.
558
559This function allows your callbacks to block by executing them in another
560coroutine where it is safe to block. One example where blocking is handy
561is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
562disk.
563
564In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
565creating event callbacks that want to block.
566
567=cut
568
569our @unblock_queue;
570
571# we create a special coro because we want to cede,
572# to reduce pressure on the coro pool (because most callbacks
573# return immediately and can be reused) and because we cannot cede
574# inside an event callback.
575our $unblock_scheduler = new Coro sub {
576 while () {
577 while (my $cb = pop @unblock_queue) {
578 # this is an inlined copy of async_pool
579 my $coro = (pop @async_pool) || new Coro \&pool_handler;
580
581 $coro->{_invoke} = $cb;
582 $coro->ready;
583 cede; # for short-lived callbacks, this reduces pressure on the coro pool
584 }
585 schedule; # sleep well
586 }
587};
588$unblock_scheduler->desc ("[unblock_sub scheduler]");
589
590sub unblock_sub(&) {
591 my $cb = shift;
592
593 sub {
594 unshift @unblock_queue, [$cb, @_];
595 $unblock_scheduler->ready;
596 }
597}
598
599=back
600
223=cut 601=cut
224 602
2251; 6031;
226 604
227=head1 BUGS/LIMITATIONS 605=head1 BUGS/LIMITATIONS
228 606
229 - could be faster, especially when the core would introduce special 607 - you must make very sure that no coro is still active on global
230 support for coroutines (like it does for threads). 608 destruction. very bad things might happen otherwise (usually segfaults).
231 - there is still a memleak on coroutine termination that I could not 609
232 identify. Could be as small as a single SV.
233 - this module is not well-tested.
234 - if variables or arguments "disappear" (become undef) or become
235 corrupted please contact the author so he cen iron out the
236 remaining bugs.
237 - this module is not thread-safe. You must only ever use this module from 610 - this module is not thread-safe. You should only ever use this module
238 the same thread (this requirement might be loosened in the future to 611 from the same thread (this requirement might be loosened in the future
239 allow per-thread schedulers, but Coro::Satte does not yet allow this). 612 to allow per-thread schedulers, but Coro::State does not yet allow
613 this).
240 614
241=head1 SEE ALSO 615=head1 SEE ALSO
242 616
243L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 617Lower level Configuration, Coroutine Environment: L<Coro::State>.
244L<Coro::Signal>, L<Coro::State>, L<Coro::Event>. 618
619Debugging: L<Coro::Debug>.
620
621Support/Utility: L<Coro::Specific>, L<Coro::Util>.
622
623Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
624
625Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>.
626
627Compatibility: L<Coro::LWP>, L<Coro::Storable>, L<Coro::Select>.
628
629Embedding: L<Coro::MakeMaker>.
245 630
246=head1 AUTHOR 631=head1 AUTHOR
247 632
248 Marc Lehmann <pcg@goof.com> 633 Marc Lehmann <schmorp@schmorp.de>
249 http://www.goof.com/pcg/marc/ 634 http://home.schmorp.de/
250 635
251=cut 636=cut
252 637

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