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Revision 1.20 by root, Sat Jul 21 18:21:45 2001 UTC vs.
Revision 1.162 by root, Wed Dec 12 19:09:33 2007 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).
27 41
28In this module, coroutines are defined as "callchain + lexical variables 42In this module, coroutines are defined as "callchain + lexical variables +
29+ @_ + $_ + $@ + $^W), that is, a coroutine has it's own callchain, it's 43@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
30own set of lexicals and it's own set of perl's most important global 44its own set of lexicals and its own set of perls most important global
31variables. 45variables (see L<Coro::State> for more configuration).
32 46
33=cut 47=cut
34 48
35package Coro; 49package Coro;
36 50
51use strict;
52no warnings "uninitialized";
53
37use Coro::State; 54use Coro::State;
38 55
39use base Exporter; 56use base qw(Coro::State Exporter);
40 57
41$VERSION = 0.10; 58our $idle; # idle handler
59our $main; # main coroutine
60our $current; # current coroutine
42 61
62our $VERSION = '4.31';
63
43@EXPORT = qw(async yield schedule terminate current); 64our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
44@EXPORT_OK = qw($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));
45 69
46{ 70{
47 my @async; 71 my @async;
72 my $init;
48 73
49 # this way of handling attributes simply is NOT scalable ;() 74 # this way of handling attributes simply is NOT scalable ;()
50 sub import { 75 sub import {
76 no strict 'refs';
77
51 Coro->export_to_level(1, @_); 78 Coro->export_to_level (1, @_);
79
52 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; 80 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
53 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { 81 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
54 my ($package, $ref) = (shift, shift); 82 my ($package, $ref) = (shift, shift);
55 my @attrs; 83 my @attrs;
56 for (@_) { 84 for (@_) {
57 if ($_ eq "Coro") { 85 if ($_ eq "Coro") {
58 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 }
59 } else { 94 } else {
60 push @attrs, $_; 95 push @attrs, $_;
61 } 96 }
62 } 97 }
63 return $old ? $old->($package, $ref, @attrs) : @attrs; 98 return $old ? $old->($package, $ref, @attrs) : @attrs;
64 }; 99 };
65 } 100 }
66 101
67 sub INIT {
68 &async(pop @async) while @async;
69 }
70} 102}
103
104=over 4
71 105
72=item $main 106=item $main
73 107
74This coroutine represents the main program. 108This coroutine represents the main program.
75 109
76=cut 110=cut
77 111
78our $main = new Coro; 112$main = new Coro;
79 113
80=item $current (or as function: current) 114=item $current (or as function: current)
81 115
82The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). 116The current coroutine (the last coroutine switched to). The initial value
117is C<$main> (of course).
83 118
119This variable is B<strictly> I<read-only>. It is provided for performance
120reasons. If performance is not essential you are encouraged to use the
121C<Coro::current> function instead.
122
84=cut 123=cut
124
125$main->{desc} = "[main::]";
85 126
86# maybe some other module used Coro::Specific before... 127# maybe some other module used Coro::Specific before...
87if ($current) {
88 $main->{specific} = $current->{specific}; 128$main->{_specific} = $current->{_specific}
89} 129 if $current;
90 130
91our $current = $main; 131_set_current $main;
92 132
93sub current() { $current } 133sub current() { $current }
94 134
95=item $idle 135=item $idle
96 136
97The coroutine to switch to when no other coroutine is running. The default 137A callback that is called whenever the scheduler finds no ready coroutines
98implementation 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.
99 140
100=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.
101 144
102# should be done using priorities :( 145Please note that if your callback recursively invokes perl (e.g. for event
103our $idle = new Coro sub { 146handlers), then it must be prepared to be called recursively itself.
104 print STDERR "FATAL: deadlock detected\n"; 147
105 exit(51); 148=cut
149
150$idle = sub {
151 require Carp;
152 Carp::croak ("FATAL: deadlock detected");
106}; 153};
107 154
108# we really need priorities... 155sub _cancel {
109my @ready; # the ready queue. hehe, rather broken ;) 156 my ($self) = @_;
157
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);
110 182
111# static methods. not really. 183# static methods. not really.
112 184
185=back
186
113=head2 STATIC METHODS 187=head2 STATIC METHODS
114 188
115Static methods are actually functions that operate on the current process only. 189Static methods are actually functions that operate on the current coroutine only.
116 190
117=over 4 191=over 4
118 192
119=item async { ... } [@args...] 193=item async { ... } [@args...]
120 194
121Create a new asynchronous process and return it's process object 195Create a new asynchronous coroutine and return it's coroutine object
122(usually unused). When the sub returns the new process is automatically 196(usually unused). When the sub returns the new coroutine is automatically
123terminated. 197terminated.
198
199See the C<Coro::State::new> constructor for info about the coroutine
200environment in which coroutines run.
201
202Calling C<exit> in a coroutine will do the same as calling exit outside
203the coroutine. Likewise, when the coroutine dies, the program will exit,
204just as it would in the main program.
124 205
125 # create a new coroutine that just prints its arguments 206 # create a new coroutine that just prints its arguments
126 async { 207 async {
127 print "@_\n"; 208 print "@_\n";
128 } 1,2,3,4; 209 } 1,2,3,4;
129 210
130The coderef you submit MUST NOT be a closure that refers to variables
131in an outer scope. This does NOT work. Pass arguments into it instead.
132
133=cut 211=cut
134 212
135sub async(&@) { 213sub async(&@) {
136 my $pid = new Coro @_; 214 my $coro = new Coro @_;
137 $pid->ready; 215 $coro->ready;
138 $pid; 216 $coro
217}
218
219=item async_pool { ... } [@args...]
220
221Similar to C<async>, but uses a coroutine pool, so you should not call
222terminate or join (although you are allowed to), and you get a coroutine
223that might have executed other code already (which can be good or bad :).
224
225Also, the block is executed in an C<eval> context and a warning will be
226issued in case of an exception instead of terminating the program, as
227C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
228will not work in the expected way, unless you call terminate or cancel,
229which somehow defeats the purpose of pooling.
230
231The priority will be reset to C<0> after each job, tracing will be
232disabled, the description will be reset and the default output filehandle
233gets restored, so you can change alkl these. Otherwise the coroutine will
234be re-used "as-is": most notably if you change other per-coroutine global
235stuff such as C<$/> you need to revert that change, which is most simply
236done by using local as in C< local $/ >.
237
238The pool size is limited to 8 idle coroutines (this can be adjusted by
239changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
240required.
241
242If you are concerned about pooled coroutines growing a lot because a
243single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
244{ terminate }> once per second or so to slowly replenish the pool. In
245addition to that, when the stacks used by a handler grows larger than 16kb
246(adjustable with $Coro::POOL_RSS) it will also exit.
247
248=cut
249
250our $POOL_SIZE = 8;
251our $POOL_RSS = 16 * 1024;
252our @async_pool;
253
254sub pool_handler {
255 my $cb;
256
257 while () {
258 eval {
259 while () {
260 _pool_1 $cb;
261 &$cb;
262 _pool_2 $cb;
263 &schedule;
264 }
265 };
266
267 last if $@ eq "\3async_pool terminate\2\n";
268 warn $@ if $@;
269 }
270}
271
272sub async_pool(&@) {
273 # this is also inlined into the unlock_scheduler
274 my $coro = (pop @async_pool) || new Coro \&pool_handler;
275
276 $coro->{_invoke} = [@_];
277 $coro->ready;
278
279 $coro
139} 280}
140 281
141=item schedule 282=item schedule
142 283
143Calls the scheduler. Please note that the current process will not be put 284Calls the scheduler. Please note that the current coroutine will not be put
144into the ready queue, so calling this function usually means you will 285into the ready queue, so calling this function usually means you will
145never be called again. 286never be called again unless something else (e.g. an event handler) calls
287ready.
146 288
147=cut 289The canonical way to wait on external events is this:
148 290
149my $prev; 291 {
292 # remember current coroutine
293 my $current = $Coro::current;
150 294
151sub schedule { 295 # register a hypothetical event handler
152 # should be done using priorities :( 296 on_event_invoke sub {
153 ($prev, $current) = ($current, shift @ready || $idle); 297 # wake up sleeping coroutine
154 Coro::State::transfer($prev, $current);
155}
156
157=item yield
158
159Yield to other processes. This function puts the current process into the
160ready queue and calls C<schedule>.
161
162=cut
163
164sub yield {
165 $current->ready; 298 $current->ready;
166 &schedule; 299 undef $current;
167} 300 };
168 301
302 # call schedule until event occurred.
303 # in case we are woken up for other reasons
304 # (current still defined), loop.
305 Coro::schedule while $current;
306 }
307
308=item cede
309
310"Cede" to other coroutines. This function puts the current coroutine into the
311ready queue and calls C<schedule>, which has the effect of giving up the
312current "timeslice" to other coroutines of the same or higher priority.
313
314=item Coro::cede_notself
315
316Works like cede, but is not exported by default and will cede to any
317coroutine, regardless of priority, once.
318
169=item terminate 319=item terminate [arg...]
170 320
171Terminates the current process. 321Terminates the current coroutine with the given status values (see L<cancel>).
172 322
173Future versions of this function will allow result arguments. 323=item killall
324
325Kills/terminates/cancels all coroutines except the currently running
326one. This is useful after a fork, either in the child or the parent, as
327usually only one of them should inherit the running coroutines.
174 328
175=cut 329=cut
176 330
177sub terminate { 331sub terminate {
178 $current->{_results} = [@_]; 332 $current->cancel (@_);
179 &schedule; 333}
334
335sub killall {
336 for (Coro::State::list) {
337 $_->cancel
338 if $_ != $current && UNIVERSAL::isa $_, "Coro";
339 }
180} 340}
181 341
182=back 342=back
183 343
184# dynamic methods 344# dynamic methods
185 345
186=head2 PROCESS METHODS 346=head2 COROUTINE METHODS
187 347
188These are the methods you can call on process objects. 348These are the methods you can call on coroutine objects.
189 349
190=over 4 350=over 4
191 351
192=item new Coro \&sub [, @args...] 352=item new Coro \&sub [, @args...]
193 353
194Create a new process and return it. When the sub returns the process 354Create a new coroutine and return it. When the sub returns the coroutine
195automatically terminates. To start the process you must first put it into 355automatically terminates as if C<terminate> with the returned values were
356called. To make the coroutine run you must first put it into the ready queue
196the ready queue by calling the ready method. 357by calling the ready method.
197 358
198The coderef you submit MUST NOT be a closure that refers to variables 359See C<async> and C<Coro::State::new> for additional info about the
199in an outer scope. This does NOT work. Pass arguments into it instead. 360coroutine environment.
200 361
201=cut 362=cut
202 363
203sub _newcoro { 364sub _run_coro {
204 terminate &{+shift}; 365 terminate &{+shift};
205} 366}
206 367
207sub new { 368sub new {
208 my $class = shift; 369 my $class = shift;
209 bless {
210 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
211 }, $class;
212}
213 370
214=item $process->ready 371 $class->SUPER::new (\&_run_coro, @_)
372}
215 373
216Put the current process into the ready queue. 374=item $success = $coroutine->ready
217 375
218=cut 376Put the given coroutine into the ready queue (according to it's priority)
377and return true. If the coroutine is already in the ready queue, do nothing
378and return false.
219 379
220sub ready { 380=item $is_ready = $coroutine->is_ready
221 push @ready, $_[0]; 381
382Return wether the coroutine is currently the ready queue or not,
383
384=item $coroutine->cancel (arg...)
385
386Terminates the given coroutine and makes it return the given arguments as
387status (default: the empty list). Never returns if the coroutine is the
388current coroutine.
389
390=cut
391
392sub cancel {
393 my $self = shift;
394 $self->{_status} = [@_];
395
396 if ($current == $self) {
397 push @destroy, $self;
398 $manager->ready;
399 &schedule while 1;
400 } else {
401 $self->_cancel;
402 }
403}
404
405=item $coroutine->join
406
407Wait until the coroutine terminates and return any values given to the
408C<terminate> or C<cancel> functions. C<join> can be called concurrently
409from multiple coroutines.
410
411=cut
412
413sub join {
414 my $self = shift;
415
416 unless ($self->{_status}) {
417 my $current = $current;
418
419 push @{$self->{_on_destroy}}, sub {
420 $current->ready;
421 undef $current;
422 };
423
424 &schedule while $current;
425 }
426
427 wantarray ? @{$self->{_status}} : $self->{_status}[0];
428}
429
430=item $coroutine->on_destroy (\&cb)
431
432Registers a callback that is called when this coroutine gets destroyed,
433but before it is joined. The callback gets passed the terminate arguments,
434if any.
435
436=cut
437
438sub on_destroy {
439 my ($self, $cb) = @_;
440
441 push @{ $self->{_on_destroy} }, $cb;
442}
443
444=item $oldprio = $coroutine->prio ($newprio)
445
446Sets (or gets, if the argument is missing) the priority of the
447coroutine. Higher priority coroutines get run before lower priority
448coroutines. Priorities are small signed integers (currently -4 .. +3),
449that you can refer to using PRIO_xxx constants (use the import tag :prio
450to get then):
451
452 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
453 3 > 1 > 0 > -1 > -3 > -4
454
455 # set priority to HIGH
456 current->prio(PRIO_HIGH);
457
458The idle coroutine ($Coro::idle) always has a lower priority than any
459existing coroutine.
460
461Changing the priority of the current coroutine will take effect immediately,
462but changing the priority of coroutines in the ready queue (but not
463running) will only take effect after the next schedule (of that
464coroutine). This is a bug that will be fixed in some future version.
465
466=item $newprio = $coroutine->nice ($change)
467
468Similar to C<prio>, but subtract the given value from the priority (i.e.
469higher values mean lower priority, just as in unix).
470
471=item $olddesc = $coroutine->desc ($newdesc)
472
473Sets (or gets in case the argument is missing) the description for this
474coroutine. This is just a free-form string you can associate with a coroutine.
475
476This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
477can modify this member directly if you wish.
478
479=item $coroutine->throw ([$scalar])
480
481If C<$throw> is specified and defined, it will be thrown as an exception
482inside the coroutine at the next convinient point in time (usually after
483it gains control at the next schedule/transfer/cede). Otherwise clears the
484exception object.
485
486The exception object will be thrown "as is" with the specified scalar in
487C<$@>, i.e. if it is a string, no line number or newline will be appended
488(unlike with C<die>).
489
490This can be used as a softer means than C<cancel> to ask a coroutine to
491end itself, although there is no guarentee that the exception will lead to
492termination, and if the exception isn't caught it might well end the whole
493program.
494
495=cut
496
497sub desc {
498 my $old = $_[0]{desc};
499 $_[0]{desc} = $_[1] if @_ > 1;
500 $old;
222} 501}
223 502
224=back 503=back
225 504
505=head2 GLOBAL FUNCTIONS
506
507=over 4
508
509=item Coro::nready
510
511Returns the number of coroutines that are currently in the ready state,
512i.e. that can be switched to. The value C<0> means that the only runnable
513coroutine is the currently running one, so C<cede> would have no effect,
514and C<schedule> would cause a deadlock unless there is an idle handler
515that wakes up some coroutines.
516
517=item my $guard = Coro::guard { ... }
518
519This creates and returns a guard object. Nothing happens until the object
520gets destroyed, in which case the codeblock given as argument will be
521executed. This is useful to free locks or other resources in case of a
522runtime error or when the coroutine gets canceled, as in both cases the
523guard block will be executed. The guard object supports only one method,
524C<< ->cancel >>, which will keep the codeblock from being executed.
525
526Example: set some flag and clear it again when the coroutine gets canceled
527or the function returns:
528
529 sub do_something {
530 my $guard = Coro::guard { $busy = 0 };
531 $busy = 1;
532
533 # do something that requires $busy to be true
534 }
535
536=cut
537
538sub guard(&) {
539 bless \(my $cb = $_[0]), "Coro::guard"
540}
541
542sub Coro::guard::cancel {
543 ${$_[0]} = sub { };
544}
545
546sub Coro::guard::DESTROY {
547 ${$_[0]}->();
548}
549
550
551=item unblock_sub { ... }
552
553This utility function takes a BLOCK or code reference and "unblocks" it,
554returning the new coderef. This means that the new coderef will return
555immediately without blocking, returning nothing, while the original code
556ref will be called (with parameters) from within its own coroutine.
557
558The reason this function exists is that many event libraries (such as the
559venerable L<Event|Event> module) are not coroutine-safe (a weaker form
560of thread-safety). This means you must not block within event callbacks,
561otherwise you might suffer from crashes or worse.
562
563This function allows your callbacks to block by executing them in another
564coroutine where it is safe to block. One example where blocking is handy
565is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
566disk.
567
568In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
569creating event callbacks that want to block.
570
571=cut
572
573our @unblock_queue;
574
575# we create a special coro because we want to cede,
576# to reduce pressure on the coro pool (because most callbacks
577# return immediately and can be reused) and because we cannot cede
578# inside an event callback.
579our $unblock_scheduler = new Coro sub {
580 while () {
581 while (my $cb = pop @unblock_queue) {
582 # this is an inlined copy of async_pool
583 my $coro = (pop @async_pool) || new Coro \&pool_handler;
584
585 $coro->{_invoke} = $cb;
586 $coro->ready;
587 cede; # for short-lived callbacks, this reduces pressure on the coro pool
588 }
589 schedule; # sleep well
590 }
591};
592$unblock_scheduler->desc ("[unblock_sub scheduler]");
593
594sub unblock_sub(&) {
595 my $cb = shift;
596
597 sub {
598 unshift @unblock_queue, [$cb, @_];
599 $unblock_scheduler->ready;
600 }
601}
602
603=back
604
226=cut 605=cut
227 606
2281; 6071;
229 608
230=head1 BUGS/LIMITATIONS 609=head1 BUGS/LIMITATIONS
231 610
232 - could be faster, especially when the core would introduce special 611 - you must make very sure that no coro is still active on global
233 support for coroutines (like it does for threads). 612 destruction. very bad things might happen otherwise (usually segfaults).
234 - there is still a memleak on coroutine termination that I could not 613
235 identify. Could be as small as a single SV.
236 - this module is not well-tested.
237 - if variables or arguments "disappear" (become undef) or become
238 corrupted please contact the author so he cen iron out the
239 remaining bugs.
240 - this module is not thread-safe. You must only ever use this module from 614 - this module is not thread-safe. You should only ever use this module
241 the same thread (this requirement might be loosened in the future to 615 from the same thread (this requirement might be loosened in the future
242 allow per-thread schedulers, but Coro::State does not yet allow this). 616 to allow per-thread schedulers, but Coro::State does not yet allow
617 this).
243 618
244=head1 SEE ALSO 619=head1 SEE ALSO
245 620
246L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 621Lower level Configuration, Coroutine Environment: L<Coro::State>.
247L<Coro::Signal>, L<Coro::State>, L<Coro::Event>. 622
623Debugging: L<Coro::Debug>.
624
625Support/Utility: L<Coro::Specific>, L<Coro::Util>.
626
627Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
628
629Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>.
630
631Compatibility: L<Coro::LWP>, L<Coro::Storable>, L<Coro::Select>.
632
633Embedding: L<Coro::MakeMaker>.
248 634
249=head1 AUTHOR 635=head1 AUTHOR
250 636
251 Marc Lehmann <pcg@goof.com> 637 Marc Lehmann <schmorp@schmorp.de>
252 http://www.goof.com/pcg/marc/ 638 http://home.schmorp.de/
253 639
254=cut 640=cut
255 641

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