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Revision 1.17 by root, Thu Jul 19 02:45:09 2001 UTC vs.
Revision 1.175 by root, Sun Apr 6 19:23:50 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 = 0.08; 58our $idle; # idle handler
59our $main; # main coroutine
60our $current; # current coroutine
37 61
38@EXPORT = qw(async yield schedule terminate); 62our $VERSION = '4.49';
39@EXPORT_OK = qw($current); 63
64our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
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 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;
132
133sub current() { $current }
89 134
90=item $idle 135=item $idle
91 136
92The coroutine to switch to when no other coroutine is running. The default 137A callback that is called whenever the scheduler finds no ready coroutines
93implementation 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.
94 140
95=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.
96 144
97# should be done using priorities :( 145Please note that if your callback recursively invokes perl (e.g. for event
98our $idle = new Coro sub { 146handlers), then it must be prepared to be called recursively itself.
99 print STDERR "FATAL: deadlock detected\n"; 147
100 exit(51); 148=cut
149
150$idle = sub {
151 require Carp;
152 Carp::croak ("FATAL: deadlock detected");
101}; 153};
102 154
103# we really need priorities... 155sub _cancel {
104my @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);
105 182
106# static methods. not really. 183# static methods. not really.
107 184
185=back
186
108=head2 STATIC METHODS 187=head2 STATIC METHODS
109 188
110Static methods are actually functions that operate on the current process only. 189Static methods are actually functions that operate on the current coroutine only.
111 190
112=over 4 191=over 4
113 192
114=item async { ... } [@args...] 193=item async { ... } [@args...]
115 194
116Create a new asynchronous process and return it's process object 195Create a new asynchronous coroutine and return it's coroutine object
117(usually unused). When the sub returns the new process is automatically 196(usually unused). When the sub returns the new coroutine is automatically
118terminated. 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.
119 205
120 # create a new coroutine that just prints its arguments 206 # create a new coroutine that just prints its arguments
121 async { 207 async {
122 print "@_\n"; 208 print "@_\n";
123 } 1,2,3,4; 209 } 1,2,3,4;
124 210
125The coderef you submit MUST NOT be a closure that refers to variables
126in an outer scope. This does NOT work. Pass arguments into it instead.
127
128=cut 211=cut
129 212
130sub async(&@) { 213sub async(&@) {
131 my $pid = new Coro @_; 214 my $coro = new Coro @_;
132 $pid->ready; 215 $coro->ready;
133 $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
134} 280}
135 281
136=item schedule 282=item schedule
137 283
138Calls 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
139into the ready queue, so calling this function usually means you will 285into the ready queue, so calling this function usually means you will
140never be called again. 286never be called again unless something else (e.g. an event handler) calls
287ready.
141 288
142=cut 289The canonical way to wait on external events is this:
143 290
144my $prev; 291 {
292 # remember current coroutine
293 my $current = $Coro::current;
145 294
146sub schedule { 295 # register a hypothetical event handler
147 # should be done using priorities :( 296 on_event_invoke sub {
148 ($prev, $current) = ($current, shift @ready || $idle); 297 # wake up sleeping coroutine
149 Coro::State::transfer($prev, $current);
150}
151
152=item yield
153
154Yield to other processes. This function puts the current process into the
155ready queue and calls C<schedule>.
156
157=cut
158
159sub yield {
160 $current->ready; 298 $current->ready;
161 &schedule; 299 undef $current;
162} 300 };
163 301
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
164=item terminate 319=item terminate [arg...]
165 320
166Terminates the current process. 321Terminates the current coroutine with the given status values (see L<cancel>).
167 322
168Future 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.
169 328
170=cut 329=cut
171 330
172sub terminate { 331sub terminate {
173 $current->{_results} = [@_]; 332 $current->cancel (@_);
174 &schedule; 333}
334
335sub killall {
336 for (Coro::State::list) {
337 $_->cancel
338 if $_ != $current && UNIVERSAL::isa $_, "Coro";
339 }
175} 340}
176 341
177=back 342=back
178 343
179# dynamic methods 344# dynamic methods
180 345
181=head2 PROCESS METHODS 346=head2 COROUTINE METHODS
182 347
183These are the methods you can call on process objects. 348These are the methods you can call on coroutine objects.
184 349
185=over 4 350=over 4
186 351
187=item new Coro \&sub [, @args...] 352=item new Coro \&sub [, @args...]
188 353
189Create 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
190automatically 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
191the ready queue by calling the ready method. 357by calling the ready method.
192 358
193The 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
194in an outer scope. This does NOT work. Pass arguments into it instead. 360coroutine environment.
195 361
196=cut 362=cut
197 363
198sub _newcoro { 364sub _run_coro {
199 terminate &{+shift}; 365 terminate &{+shift};
200} 366}
201 367
202sub new { 368sub new {
203 my $class = shift; 369 my $class = shift;
204 bless {
205 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
206 }, $class;
207}
208 370
209=item $process->ready 371 $class->SUPER::new (\&_run_coro, @_)
372}
210 373
211Put the current process into the ready queue. 374=item $success = $coroutine->ready
212 375
213=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.
214 379
215sub ready { 380=item $is_ready = $coroutine->is_ready
216 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;
217} 501}
218 502
219=back 503=back
220 504
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
221=cut 605=cut
222 606
2231; 6071;
224 608
225=head1 BUGS/LIMITATIONS 609=head1 BUGS/LIMITATIONS
226 610
227 - could be faster, especially when the core would introduce special 611 - you must make very sure that no coro is still active on global
228 support for coroutines (like it does for threads). 612 destruction. very bad things might happen otherwise (usually segfaults).
229 - there is still a memleak on coroutine termination that I could not 613
230 identify. Could be as small as a single SV.
231 - this module is not well-tested.
232 - if variables or arguments "disappear" (become undef) or become
233 corrupted please contact the author so he cen iron out the
234 remaining bugs.
235 - 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
236 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
237 allow per-thread schedulers, but Coro::Satte does not yet allow this). 616 to allow per-thread schedulers, but Coro::State does not yet allow
617 this).
238 618
239=head1 SEE ALSO 619=head1 SEE ALSO
240 620
241L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 621Lower level Configuration, Coroutine Environment: L<Coro::State>.
242L<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>.
243 634
244=head1 AUTHOR 635=head1 AUTHOR
245 636
246 Marc Lehmann <pcg@goof.com> 637 Marc Lehmann <schmorp@schmorp.de>
247 http://www.goof.com/pcg/marc/ 638 http://home.schmorp.de/
248 639
249=cut 640=cut
250 641

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