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Revision 1.20 by root, Sat Jul 21 18:21:45 2001 UTC vs.
Revision 1.150 by root, Sat Oct 6 01:11:01 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 yield; 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
26This module is still experimental, see the BUGS section below. 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).
27 34
28In this module, coroutines are defined as "callchain + lexical variables 35In this module, coroutines are defined as "callchain + lexical variables +
29+ @_ + $_ + $@ + $^W), that is, a coroutine has it's own callchain, it's 36@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
30own set of lexicals and it's own set of perl's most important global 37its own set of lexicals and its own set of perls most important global
31variables. 38variables.
32 39
33=cut 40=cut
34 41
35package Coro; 42package Coro;
36 43
44use strict;
45no warnings "uninitialized";
46
37use Coro::State; 47use Coro::State;
38 48
39use base Exporter; 49use base qw(Coro::State Exporter);
40 50
41$VERSION = 0.10; 51our $idle; # idle handler
52our $main; # main coroutine
53our $current; # current coroutine
42 54
55our $VERSION = '4.02';
56
43@EXPORT = qw(async yield schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
44@EXPORT_OK = qw($current); 58our %EXPORT_TAGS = (
59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
60);
61our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
45 62
46{ 63{
47 my @async; 64 my @async;
65 my $init;
48 66
49 # this way of handling attributes simply is NOT scalable ;() 67 # this way of handling attributes simply is NOT scalable ;()
50 sub import { 68 sub import {
69 no strict 'refs';
70
51 Coro->export_to_level(1, @_); 71 Coro->export_to_level (1, @_);
72
52 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; 73 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
53 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { 74 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
54 my ($package, $ref) = (shift, shift); 75 my ($package, $ref) = (shift, shift);
55 my @attrs; 76 my @attrs;
56 for (@_) { 77 for (@_) {
57 if ($_ eq "Coro") { 78 if ($_ eq "Coro") {
58 push @async, $ref; 79 push @async, $ref;
80 unless ($init++) {
81 eval q{
82 sub INIT {
83 &async(pop @async) while @async;
84 }
85 };
86 }
59 } else { 87 } else {
60 push @attrs, $_; 88 push @attrs, $_;
61 } 89 }
62 } 90 }
63 return $old ? $old->($package, $ref, @attrs) : @attrs; 91 return $old ? $old->($package, $ref, @attrs) : @attrs;
64 }; 92 };
65 } 93 }
66 94
67 sub INIT {
68 &async(pop @async) while @async;
69 }
70} 95}
96
97=over 4
71 98
72=item $main 99=item $main
73 100
74This coroutine represents the main program. 101This coroutine represents the main program.
75 102
76=cut 103=cut
77 104
78our $main = new Coro; 105$main = new Coro;
79 106
80=item $current (or as function: current) 107=item $current (or as function: current)
81 108
82The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). 109The current coroutine (the last coroutine switched to). The initial value
110is C<$main> (of course).
83 111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essential you are encouraged to use the
114C<Coro::current> function instead.
115
84=cut 116=cut
117
118$main->{desc} = "[main::]";
85 119
86# maybe some other module used Coro::Specific before... 120# maybe some other module used Coro::Specific before...
87if ($current) {
88 $main->{specific} = $current->{specific}; 121$main->{_specific} = $current->{_specific}
89} 122 if $current;
90 123
91our $current = $main; 124_set_current $main;
92 125
93sub current() { $current } 126sub current() { $current }
94 127
95=item $idle 128=item $idle
96 129
97The coroutine to switch to when no other coroutine is running. The default 130A callback that is called whenever the scheduler finds no ready coroutines
98implementation 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.
99 133
100=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.
101 137
102# should be done using priorities :( 138Please note that if your callback recursively invokes perl (e.g. for event
103our $idle = new Coro sub { 139handlers), then it must be prepared to be called recursively.
104 print STDERR "FATAL: deadlock detected\n"; 140
105 exit(51); 141=cut
142
143$idle = sub {
144 require Carp;
145 Carp::croak ("FATAL: deadlock detected");
106}; 146};
107 147
108# we really need priorities... 148sub _cancel {
109my @ready; # the ready queue. hehe, rather broken ;) 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}
159
160# this coroutine is necessary because a coroutine
161# cannot destroy itself.
162my @destroy;
163my $manager;
164
165$manager = new Coro sub {
166 while () {
167 (shift @destroy)->_cancel
168 while @destroy;
169
170 &schedule;
171 }
172};
173$manager->desc ("[coro manager]");
174$manager->prio (PRIO_MAX);
110 175
111# static methods. not really. 176# static methods. not really.
112 177
178=back
179
113=head2 STATIC METHODS 180=head2 STATIC METHODS
114 181
115Static methods are actually functions that operate on the current process only. 182Static methods are actually functions that operate on the current coroutine only.
116 183
117=over 4 184=over 4
118 185
119=item async { ... } [@args...] 186=item async { ... } [@args...]
120 187
121Create a new asynchronous process and return it's process object 188Create a new asynchronous coroutine and return it's coroutine object
122(usually unused). When the sub returns the new process is automatically 189(usually unused). When the sub returns the new coroutine is automatically
123terminated. 190terminated.
191
192See the C<Coro::State::new> constructor for info about the coroutine
193environment.
194
195Calling C<exit> in a coroutine will do the same as calling exit outside
196the coroutine. Likewise, when the coroutine dies, the program will exit,
197just as it would in the main program.
124 198
125 # create a new coroutine that just prints its arguments 199 # create a new coroutine that just prints its arguments
126 async { 200 async {
127 print "@_\n"; 201 print "@_\n";
128 } 1,2,3,4; 202 } 1,2,3,4;
129 203
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 204=cut
134 205
135sub async(&@) { 206sub async(&@) {
136 my $pid = new Coro @_; 207 my $coro = new Coro @_;
137 $pid->ready; 208 $coro->ready;
138 $pid; 209 $coro
210}
211
212=item async_pool { ... } [@args...]
213
214Similar to C<async>, but uses a coroutine pool, so you should not call
215terminate or join (although you are allowed to), and you get a coroutine
216that might have executed other code already (which can be good or bad :).
217
218Also, the block is executed in an C<eval> context and a warning will be
219issued in case of an exception instead of terminating the program, as
220C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
221will not work in the expected way, unless you call terminate or cancel,
222which somehow defeats the purpose of pooling.
223
224The priority will be reset to C<0> after each job, tracing will be
225disabled, the description will be reset and the default output filehandle
226gets restored, so you can change alkl these. Otherwise the coroutine will
227be re-used "as-is": most notably if you change other per-coroutine global
228stuff such as C<$/> you need to revert that change, which is most simply
229done by using local as in C< local $/ >.
230
231The pool size is limited to 8 idle coroutines (this can be adjusted by
232changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
233required.
234
235If you are concerned about pooled coroutines growing a lot because a
236single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
237{ terminate }> once per second or so to slowly replenish the pool. In
238addition to that, when the stacks used by a handler grows larger than 16kb
239(adjustable with $Coro::POOL_RSS) it will also exit.
240
241=cut
242
243our $POOL_SIZE = 8;
244our $POOL_RSS = 16 * 1024;
245our @async_pool;
246
247sub pool_handler {
248 my $cb;
249
250 while () {
251 eval {
252 while () {
253 _pool_1 $cb;
254 &$cb;
255 _pool_2 $cb;
256 &schedule;
257 }
258 };
259
260 last if $@ eq "\3terminate\2\n";
261 warn $@ if $@;
262 }
263}
264
265sub async_pool(&@) {
266 # this is also inlined into the unlock_scheduler
267 my $coro = (pop @async_pool) || new Coro \&pool_handler;
268
269 $coro->{_invoke} = [@_];
270 $coro->ready;
271
272 $coro
139} 273}
140 274
141=item schedule 275=item schedule
142 276
143Calls the scheduler. Please note that the current process will not be put 277Calls the scheduler. Please note that the current coroutine will not be put
144into the ready queue, so calling this function usually means you will 278into the ready queue, so calling this function usually means you will
145never be called again. 279never be called again unless something else (e.g. an event handler) calls
280ready.
146 281
147=cut 282The canonical way to wait on external events is this:
148 283
149my $prev; 284 {
285 # remember current coroutine
286 my $current = $Coro::current;
150 287
151sub schedule { 288 # register a hypothetical event handler
152 # should be done using priorities :( 289 on_event_invoke sub {
153 ($prev, $current) = ($current, shift @ready || $idle); 290 # wake up sleeping coroutine
154 Coro::State::transfer($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; 291 $current->ready;
166 &schedule; 292 undef $current;
167} 293 };
168 294
295 # call schedule until event occurred.
296 # in case we are woken up for other reasons
297 # (current still defined), loop.
298 Coro::schedule while $current;
299 }
300
301=item cede
302
303"Cede" to other coroutines. This function puts the current coroutine into the
304ready queue and calls C<schedule>, which has the effect of giving up the
305current "timeslice" to other coroutines of the same or higher priority.
306
307Returns true if at least one coroutine switch has happened.
308
309=item Coro::cede_notself
310
311Works like cede, but is not exported by default and will cede to any
312coroutine, regardless of priority, once.
313
314Returns true if at least one coroutine switch has happened.
315
169=item terminate 316=item terminate [arg...]
170 317
171Terminates the current process. 318Terminates the current coroutine with the given status values (see L<cancel>).
172 319
173Future versions of this function will allow result arguments. 320=item killall
321
322Kills/terminates/cancels all coroutines except the currently running
323one. This is useful after a fork, either in the child or the parent, as
324usually only one of them should inherit the running coroutines.
174 325
175=cut 326=cut
176 327
177sub terminate { 328sub terminate {
178 $current->{_results} = [@_]; 329 $current->cancel (@_);
179 &schedule; 330}
331
332sub killall {
333 for (Coro::State::list) {
334 $_->cancel
335 if $_ != $current && UNIVERSAL::isa $_, "Coro";
336 }
180} 337}
181 338
182=back 339=back
183 340
184# dynamic methods 341# dynamic methods
185 342
186=head2 PROCESS METHODS 343=head2 COROUTINE METHODS
187 344
188These are the methods you can call on process objects. 345These are the methods you can call on coroutine objects.
189 346
190=over 4 347=over 4
191 348
192=item new Coro \&sub [, @args...] 349=item new Coro \&sub [, @args...]
193 350
194Create a new process and return it. When the sub returns the process 351Create a new coroutine and return it. When the sub returns the coroutine
195automatically terminates. To start the process you must first put it into 352automatically terminates as if C<terminate> with the returned values were
353called. To make the coroutine run you must first put it into the ready queue
196the ready queue by calling the ready method. 354by calling the ready method.
197 355
198The coderef you submit MUST NOT be a closure that refers to variables 356See 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. 357coroutine environment.
200 358
201=cut 359=cut
202 360
203sub _newcoro { 361sub _run_coro {
204 terminate &{+shift}; 362 terminate &{+shift};
205} 363}
206 364
207sub new { 365sub new {
208 my $class = shift; 366 my $class = shift;
209 bless {
210 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
211 }, $class;
212}
213 367
214=item $process->ready 368 $class->SUPER::new (\&_run_coro, @_)
369}
215 370
216Put the current process into the ready queue. 371=item $success = $coroutine->ready
217 372
218=cut 373Put the given coroutine into the ready queue (according to it's priority)
374and return true. If the coroutine is already in the ready queue, do nothing
375and return false.
219 376
220sub ready { 377=item $is_ready = $coroutine->is_ready
221 push @ready, $_[0]; 378
379Return wether the coroutine is currently the ready queue or not,
380
381=item $coroutine->cancel (arg...)
382
383Terminates the given coroutine and makes it return the given arguments as
384status (default: the empty list). Never returns if the coroutine is the
385current coroutine.
386
387=cut
388
389sub cancel {
390 my $self = shift;
391 $self->{_status} = [@_];
392
393 if ($current == $self) {
394 push @destroy, $self;
395 $manager->ready;
396 &schedule while 1;
397 } else {
398 $self->_cancel;
399 }
400}
401
402=item $coroutine->join
403
404Wait until the coroutine terminates and return any values given to the
405C<terminate> or C<cancel> functions. C<join> can be called concurrently
406from multiple coroutines.
407
408=cut
409
410sub join {
411 my $self = shift;
412
413 unless ($self->{_status}) {
414 my $current = $current;
415
416 push @{$self->{_on_destroy}}, sub {
417 $current->ready;
418 undef $current;
419 };
420
421 &schedule while $current;
422 }
423
424 wantarray ? @{$self->{_status}} : $self->{_status}[0];
425}
426
427=item $coroutine->on_destroy (\&cb)
428
429Registers a callback that is called when this coroutine gets destroyed,
430but before it is joined. The callback gets passed the terminate arguments,
431if any.
432
433=cut
434
435sub on_destroy {
436 my ($self, $cb) = @_;
437
438 push @{ $self->{_on_destroy} }, $cb;
439}
440
441=item $oldprio = $coroutine->prio ($newprio)
442
443Sets (or gets, if the argument is missing) the priority of the
444coroutine. Higher priority coroutines get run before lower priority
445coroutines. Priorities are small signed integers (currently -4 .. +3),
446that you can refer to using PRIO_xxx constants (use the import tag :prio
447to get then):
448
449 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
450 3 > 1 > 0 > -1 > -3 > -4
451
452 # set priority to HIGH
453 current->prio(PRIO_HIGH);
454
455The idle coroutine ($Coro::idle) always has a lower priority than any
456existing coroutine.
457
458Changing the priority of the current coroutine will take effect immediately,
459but changing the priority of coroutines in the ready queue (but not
460running) will only take effect after the next schedule (of that
461coroutine). This is a bug that will be fixed in some future version.
462
463=item $newprio = $coroutine->nice ($change)
464
465Similar to C<prio>, but subtract the given value from the priority (i.e.
466higher values mean lower priority, just as in unix).
467
468=item $olddesc = $coroutine->desc ($newdesc)
469
470Sets (or gets in case the argument is missing) the description for this
471coroutine. This is just a free-form string you can associate with a coroutine.
472
473This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
474can modify this member directly if you wish.
475
476=item $coroutine->throw ([$scalar])
477
478If C<$throw> is specified and defined, it will be thrown as an exception
479inside the coroutine at the next convinient point in time (usually after
480it gains control at the next schedule/transfer/cede). Otherwise clears the
481exception object.
482
483The exception object will be thrown "as is" with the specified scalar in
484C<$@>, i.e. if it is a string, no line number or newline will be appended
485(unlike with C<die>).
486
487This can be used as a softer means than C<cancel> to ask a coroutine to
488end itself, although there is no guarentee that the exception will lead to
489termination, and if the exception isn't caught it might well end the whole
490program.
491
492=cut
493
494sub desc {
495 my $old = $_[0]{desc};
496 $_[0]{desc} = $_[1] if @_ > 1;
497 $old;
222} 498}
223 499
224=back 500=back
225 501
502=head2 GLOBAL FUNCTIONS
503
504=over 4
505
506=item Coro::nready
507
508Returns the number of coroutines that are currently in the ready state,
509i.e. that can be switched to. The value C<0> means that the only runnable
510coroutine is the currently running one, so C<cede> would have no effect,
511and C<schedule> would cause a deadlock unless there is an idle handler
512that wakes up some coroutines.
513
514=item my $guard = Coro::guard { ... }
515
516This creates and returns a guard object. Nothing happens until the object
517gets destroyed, in which case the codeblock given as argument will be
518executed. This is useful to free locks or other resources in case of a
519runtime error or when the coroutine gets canceled, as in both cases the
520guard block will be executed. The guard object supports only one method,
521C<< ->cancel >>, which will keep the codeblock from being executed.
522
523Example: set some flag and clear it again when the coroutine gets canceled
524or the function returns:
525
526 sub do_something {
527 my $guard = Coro::guard { $busy = 0 };
528 $busy = 1;
529
530 # do something that requires $busy to be true
531 }
532
533=cut
534
535sub guard(&) {
536 bless \(my $cb = $_[0]), "Coro::guard"
537}
538
539sub Coro::guard::cancel {
540 ${$_[0]} = sub { };
541}
542
543sub Coro::guard::DESTROY {
544 ${$_[0]}->();
545}
546
547
548=item unblock_sub { ... }
549
550This utility function takes a BLOCK or code reference and "unblocks" it,
551returning the new coderef. This means that the new coderef will return
552immediately without blocking, returning nothing, while the original code
553ref will be called (with parameters) from within its own coroutine.
554
555The reason this function exists is that many event libraries (such as the
556venerable L<Event|Event> module) are not coroutine-safe (a weaker form
557of thread-safety). This means you must not block within event callbacks,
558otherwise you might suffer from crashes or worse.
559
560This function allows your callbacks to block by executing them in another
561coroutine where it is safe to block. One example where blocking is handy
562is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
563disk.
564
565In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
566creating event callbacks that want to block.
567
568=cut
569
570our @unblock_queue;
571
572# we create a special coro because we want to cede,
573# to reduce pressure on the coro pool (because most callbacks
574# return immediately and can be reused) and because we cannot cede
575# inside an event callback.
576our $unblock_scheduler = new Coro sub {
577 while () {
578 while (my $cb = pop @unblock_queue) {
579 # this is an inlined copy of async_pool
580 my $coro = (pop @async_pool) || new Coro \&pool_handler;
581
582 $coro->{_invoke} = $cb;
583 $coro->ready;
584 cede; # for short-lived callbacks, this reduces pressure on the coro pool
585 }
586 schedule; # sleep well
587 }
588};
589$unblock_scheduler->desc ("[unblock_sub scheduler]");
590
591sub unblock_sub(&) {
592 my $cb = shift;
593
594 sub {
595 unshift @unblock_queue, [$cb, @_];
596 $unblock_scheduler->ready;
597 }
598}
599
600=back
601
226=cut 602=cut
227 603
2281; 6041;
229 605
230=head1 BUGS/LIMITATIONS 606=head1 BUGS/LIMITATIONS
231 607
232 - could be faster, especially when the core would introduce special 608 - you must make very sure that no coro is still active on global
233 support for coroutines (like it does for threads). 609 destruction. very bad things might happen otherwise (usually segfaults).
234 - there is still a memleak on coroutine termination that I could not 610
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 611 - 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 612 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). 613 to allow per-thread schedulers, but Coro::State does not yet allow
614 this).
243 615
244=head1 SEE ALSO 616=head1 SEE ALSO
245 617
246L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 618Support/Utility: L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
247L<Coro::Signal>, L<Coro::State>, L<Coro::Event>. 619
620Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
621
622Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
623
624Embedding: L<Coro:MakeMaker>
248 625
249=head1 AUTHOR 626=head1 AUTHOR
250 627
251 Marc Lehmann <pcg@goof.com> 628 Marc Lehmann <schmorp@schmorp.de>
252 http://www.goof.com/pcg/marc/ 629 http://home.schmorp.de/
253 630
254=cut 631=cut
255 632

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