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Revision 1.22 by root, Mon Jul 23 02:14:19 2001 UTC vs.
Revision 1.145 by root, Wed Oct 3 16:03:17 2007 UTC

8 8
9 async { 9 async {
10 # some asynchronous thread of execution 10 # some asynchronous thread of execution
11 }; 11 };
12 12
13 # alternatively create an async process like this: 13 # alternatively create an async coroutine like this:
14 14
15 sub some_func : Coro { 15 sub some_func : Coro {
16 # some more async code 16 # some more async code
17 } 17 }
18 18
19 cede; 19 cede;
20 20
21=head1 DESCRIPTION 21=head1 DESCRIPTION
22 22
23This module collection manages coroutines. Coroutines are similar to 23This module collection manages coroutines. Coroutines are similar
24Threads but don't run in parallel. 24to threads but don't run in parallel at the same time even on SMP
25machines. The specific flavor of coroutine used in this module also
26guarantees you that it will not switch between coroutines unless
27necessary, at easily-identified points in your program, so locking and
28parallel access are rarely an issue, making coroutine programming much
29safer than threads programming.
25 30
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@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
30own set of lexicals and it's own set of perl's most important global 37its own set of lexicals and its own set of perls most important global
31variables. 38variables.
32 39
33WARNING: When using this module, make sure that, at program end, no
34coroutines are still running OR just call exit before falling off the
35end. The reason for this is that some coroutine of yours might have called
36into a C function, and falling off the end of main:: results in returning
37to that C function instead if to the main C interpreter.
38
39WARNING: Unless you really know what you are doing, do NOT do context
40switches inside callbacks from the XS level. The reason for this is
41similar to the reason above: A callback calls a perl function, this
42perl function does a context switch, some other callback is called, the
43original function returns from it - to what? To the wrong XS function,
44with totally different return values. Unfortunately, this includes
45callbacks done by perl itself (tie'd variables!).
46
47The only workaround for this is to do coroutines on C level.
48
49=cut 40=cut
50 41
51package Coro; 42package Coro;
52 43
44use strict;
45no warnings "uninitialized";
46
53use Coro::State; 47use Coro::State;
54 48
55use base Exporter; 49use base qw(Coro::State Exporter);
56 50
57$VERSION = 0.10; 51our $idle; # idle handler
52our $main; # main coroutine
53our $current; # current coroutine
58 54
55our $VERSION = '4.0';
56
59@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
60@EXPORT_OK = qw($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));
61 62
62{ 63{
63 my @async; 64 my @async;
65 my $init;
64 66
65 # this way of handling attributes simply is NOT scalable ;() 67 # this way of handling attributes simply is NOT scalable ;()
66 sub import { 68 sub import {
69 no strict 'refs';
70
67 Coro->export_to_level(1, @_); 71 Coro->export_to_level (1, @_);
72
68 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; 73 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
69 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { 74 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
70 my ($package, $ref) = (shift, shift); 75 my ($package, $ref) = (shift, shift);
71 my @attrs; 76 my @attrs;
72 for (@_) { 77 for (@_) {
73 if ($_ eq "Coro") { 78 if ($_ eq "Coro") {
74 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 }
75 } else { 87 } else {
76 push @attrs, $_; 88 push @attrs, $_;
77 } 89 }
78 } 90 }
79 return $old ? $old->($package, $ref, @attrs) : @attrs; 91 return $old ? $old->($package, $ref, @attrs) : @attrs;
80 }; 92 };
81 } 93 }
82 94
83 sub INIT {
84 &async(pop @async) while @async;
85 }
86} 95}
96
97=over 4
87 98
88=item $main 99=item $main
89 100
90This coroutine represents the main program. 101This coroutine represents the main program.
91 102
92=cut 103=cut
93 104
94our $main = new Coro; 105$main = new Coro;
95 106
96=item $current (or as function: current) 107=item $current (or as function: current)
97 108
98The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). 109The current coroutine (the last coroutine switched to). The initial value
110is C<$main> (of course).
99 111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essential you are encouraged to use the
114C<Coro::current> function instead.
115
100=cut 116=cut
117
118$main->{desc} = "[main::]";
101 119
102# maybe some other module used Coro::Specific before... 120# maybe some other module used Coro::Specific before...
103if ($current) {
104 $main->{specific} = $current->{specific}; 121$main->{_specific} = $current->{_specific}
105} 122 if $current;
106 123
107our $current = $main; 124_set_current $main;
108 125
109sub current() { $current } 126sub current() { $current }
110 127
111=item $idle 128=item $idle
112 129
113The coroutine to switch to when no other coroutine is running. The default 130A callback that is called whenever the scheduler finds no ready coroutines
114implementation 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.
115 133
116=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.
117 137
118# should be done using priorities :( 138Please note that if your callback recursively invokes perl (e.g. for event
119our $idle = new Coro sub { 139handlers), then it must be prepared to be called recursively.
120 print STDERR "FATAL: deadlock detected\n"; 140
121 exit(51); 141=cut
142
143$idle = sub {
144 require Carp;
145 Carp::croak ("FATAL: deadlock detected");
122}; 146};
123 147
124# we really need priorities... 148sub _cancel {
125my @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);
126 175
127# static methods. not really. 176# static methods. not really.
128 177
178=back
179
129=head2 STATIC METHODS 180=head2 STATIC METHODS
130 181
131Static methods are actually functions that operate on the current process only. 182Static methods are actually functions that operate on the current coroutine only.
132 183
133=over 4 184=over 4
134 185
135=item async { ... } [@args...] 186=item async { ... } [@args...]
136 187
137Create a new asynchronous process and return it's process object 188Create a new asynchronous coroutine and return it's coroutine object
138(usually unused). When the sub returns the new process is automatically 189(usually unused). When the sub returns the new coroutine is automatically
139terminated. 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.
140 198
141 # create a new coroutine that just prints its arguments 199 # create a new coroutine that just prints its arguments
142 async { 200 async {
143 print "@_\n"; 201 print "@_\n";
144 } 1,2,3,4; 202 } 1,2,3,4;
145 203
146The coderef you submit MUST NOT be a closure that refers to variables
147in an outer scope. This does NOT work. Pass arguments into it instead.
148
149=cut 204=cut
150 205
151sub async(&@) { 206sub async(&@) {
152 my $pid = new Coro @_; 207 my $coro = new Coro @_;
153 $pid->ready; 208 $coro->ready;
154 $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, otherwise the coroutine
225will be re-used "as-is".
226
227The pool size is limited to 8 idle coroutines (this can be adjusted by
228changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
229required.
230
231If you are concerned about pooled coroutines growing a lot because a
232single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
233{ terminate }> once per second or so to slowly replenish the pool. In
234addition to that, when the stacks used by a handler grows larger than 16kb
235(adjustable with $Coro::POOL_RSS) it will also exit.
236
237=cut
238
239our $POOL_SIZE = 8;
240our $POOL_RSS = 16 * 1024;
241our @async_pool;
242
243sub pool_handler {
244 my $cb;
245
246 while () {
247 eval {
248 while () {
249 _pool_1 $cb;
250 &$cb;
251 _pool_2 $cb;
252 &schedule;
253 }
254 };
255
256 last if $@ eq "\3terminate\2\n";
257 warn $@ if $@;
258 }
259}
260
261sub async_pool(&@) {
262 # this is also inlined into the unlock_scheduler
263 my $coro = (pop @async_pool) || new Coro \&pool_handler;
264
265 $coro->{_invoke} = [@_];
266 $coro->ready;
267
268 $coro
155} 269}
156 270
157=item schedule 271=item schedule
158 272
159Calls the scheduler. Please note that the current process will not be put 273Calls the scheduler. Please note that the current coroutine will not be put
160into the ready queue, so calling this function usually means you will 274into the ready queue, so calling this function usually means you will
161never be called again. 275never be called again unless something else (e.g. an event handler) calls
276ready.
162 277
163=cut 278The canonical way to wait on external events is this:
164 279
165my $prev; 280 {
281 # remember current coroutine
282 my $current = $Coro::current;
166 283
167sub schedule { 284 # register a hypothetical event handler
168 # should be done using priorities :( 285 on_event_invoke sub {
169 ($prev, $current) = ($current, shift @ready || $idle); 286 # wake up sleeping coroutine
170 Coro::State::transfer($prev, $current); 287 $current->ready;
171} 288 undef $current;
289 };
290
291 # call schedule until event occurred.
292 # in case we are woken up for other reasons
293 # (current still defined), loop.
294 Coro::schedule while $current;
295 }
172 296
173=item cede 297=item cede
174 298
175"Cede" to other processes. This function puts the current process into the 299"Cede" to other coroutines. This function puts the current coroutine into the
176ready queue and calls C<schedule>, which has the effect of giving up the 300ready queue and calls C<schedule>, which has the effect of giving up the
177current "timeslice" to other coroutines of the same or higher priority. 301current "timeslice" to other coroutines of the same or higher priority.
178 302
179=cut 303Returns true if at least one coroutine switch has happened.
180 304
181sub cede { 305=item Coro::cede_notself
182 $current->ready;
183 &schedule;
184}
185 306
307Works like cede, but is not exported by default and will cede to any
308coroutine, regardless of priority, once.
309
310Returns true if at least one coroutine switch has happened.
311
186=item terminate 312=item terminate [arg...]
187 313
188Terminates the current process. 314Terminates the current coroutine with the given status values (see L<cancel>).
189 315
190Future versions of this function will allow result arguments. 316=item killall
317
318Kills/terminates/cancels all coroutines except the currently running
319one. This is useful after a fork, either in the child or the parent, as
320usually only one of them should inherit the running coroutines.
191 321
192=cut 322=cut
193 323
194sub terminate { 324sub terminate {
195 my $self = $current; 325 $current->cancel (@_);
196 $self->{_results} = [@_]; 326}
197 $current = shift @ready || $idle; 327
198 Coro::State::transfer(delete $self->{_coro_state}, $current); 328sub killall {
199 # cannot return 329 for (Coro::State::list) {
200 die; 330 $_->cancel
331 if $_ != $current && UNIVERSAL::isa $_, "Coro";
332 }
201} 333}
202 334
203=back 335=back
204 336
205# dynamic methods 337# dynamic methods
206 338
207=head2 PROCESS METHODS 339=head2 COROUTINE METHODS
208 340
209These are the methods you can call on process objects. 341These are the methods you can call on coroutine objects.
210 342
211=over 4 343=over 4
212 344
213=item new Coro \&sub [, @args...] 345=item new Coro \&sub [, @args...]
214 346
215Create a new process and return it. When the sub returns the process 347Create a new coroutine and return it. When the sub returns the coroutine
216automatically terminates. To start the process you must first put it into 348automatically terminates as if C<terminate> with the returned values were
349called. To make the coroutine run you must first put it into the ready queue
217the ready queue by calling the ready method. 350by calling the ready method.
218 351
219The coderef you submit MUST NOT be a closure that refers to variables 352See C<async> and C<Coro::State::new> for additional info about the
220in an outer scope. This does NOT work. Pass arguments into it instead. 353coroutine environment.
221 354
222=cut 355=cut
223 356
224sub _newcoro { 357sub _run_coro {
225 terminate &{+shift}; 358 terminate &{+shift};
226} 359}
227 360
228sub new { 361sub new {
229 my $class = shift; 362 my $class = shift;
230 bless {
231 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
232 }, $class;
233}
234 363
235=item $process->ready 364 $class->SUPER::new (\&_run_coro, @_)
365}
236 366
237Put the current process into the ready queue. 367=item $success = $coroutine->ready
238 368
239=cut 369Put the given coroutine into the ready queue (according to it's priority)
370and return true. If the coroutine is already in the ready queue, do nothing
371and return false.
240 372
241sub ready { 373=item $is_ready = $coroutine->is_ready
242 push @ready, $_[0]; 374
375Return wether the coroutine is currently the ready queue or not,
376
377=item $coroutine->cancel (arg...)
378
379Terminates the given coroutine and makes it return the given arguments as
380status (default: the empty list). Never returns if the coroutine is the
381current coroutine.
382
383=cut
384
385sub cancel {
386 my $self = shift;
387 $self->{_status} = [@_];
388
389 if ($current == $self) {
390 push @destroy, $self;
391 $manager->ready;
392 &schedule while 1;
393 } else {
394 $self->_cancel;
395 }
396}
397
398=item $coroutine->join
399
400Wait until the coroutine terminates and return any values given to the
401C<terminate> or C<cancel> functions. C<join> can be called concurrently
402from multiple coroutines.
403
404=cut
405
406sub join {
407 my $self = shift;
408
409 unless ($self->{_status}) {
410 my $current = $current;
411
412 push @{$self->{_on_destroy}}, sub {
413 $current->ready;
414 undef $current;
415 };
416
417 &schedule while $current;
418 }
419
420 wantarray ? @{$self->{_status}} : $self->{_status}[0];
421}
422
423=item $coroutine->on_destroy (\&cb)
424
425Registers a callback that is called when this coroutine gets destroyed,
426but before it is joined. The callback gets passed the terminate arguments,
427if any.
428
429=cut
430
431sub on_destroy {
432 my ($self, $cb) = @_;
433
434 push @{ $self->{_on_destroy} }, $cb;
435}
436
437=item $oldprio = $coroutine->prio ($newprio)
438
439Sets (or gets, if the argument is missing) the priority of the
440coroutine. Higher priority coroutines get run before lower priority
441coroutines. Priorities are small signed integers (currently -4 .. +3),
442that you can refer to using PRIO_xxx constants (use the import tag :prio
443to get then):
444
445 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
446 3 > 1 > 0 > -1 > -3 > -4
447
448 # set priority to HIGH
449 current->prio(PRIO_HIGH);
450
451The idle coroutine ($Coro::idle) always has a lower priority than any
452existing coroutine.
453
454Changing the priority of the current coroutine will take effect immediately,
455but changing the priority of coroutines in the ready queue (but not
456running) will only take effect after the next schedule (of that
457coroutine). This is a bug that will be fixed in some future version.
458
459=item $newprio = $coroutine->nice ($change)
460
461Similar to C<prio>, but subtract the given value from the priority (i.e.
462higher values mean lower priority, just as in unix).
463
464=item $olddesc = $coroutine->desc ($newdesc)
465
466Sets (or gets in case the argument is missing) the description for this
467coroutine. This is just a free-form string you can associate with a coroutine.
468
469This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
470can modify this member directly if you wish.
471
472=cut
473
474sub desc {
475 my $old = $_[0]{desc};
476 $_[0]{desc} = $_[1] if @_ > 1;
477 $old;
243} 478}
244 479
245=back 480=back
246 481
482=head2 GLOBAL FUNCTIONS
483
484=over 4
485
486=item Coro::nready
487
488Returns the number of coroutines that are currently in the ready state,
489i.e. that can be switched to. The value C<0> means that the only runnable
490coroutine is the currently running one, so C<cede> would have no effect,
491and C<schedule> would cause a deadlock unless there is an idle handler
492that wakes up some coroutines.
493
494=item my $guard = Coro::guard { ... }
495
496This creates and returns a guard object. Nothing happens until the object
497gets destroyed, in which case the codeblock given as argument will be
498executed. This is useful to free locks or other resources in case of a
499runtime error or when the coroutine gets canceled, as in both cases the
500guard block will be executed. The guard object supports only one method,
501C<< ->cancel >>, which will keep the codeblock from being executed.
502
503Example: set some flag and clear it again when the coroutine gets canceled
504or the function returns:
505
506 sub do_something {
507 my $guard = Coro::guard { $busy = 0 };
508 $busy = 1;
509
510 # do something that requires $busy to be true
511 }
512
513=cut
514
515sub guard(&) {
516 bless \(my $cb = $_[0]), "Coro::guard"
517}
518
519sub Coro::guard::cancel {
520 ${$_[0]} = sub { };
521}
522
523sub Coro::guard::DESTROY {
524 ${$_[0]}->();
525}
526
527
528=item unblock_sub { ... }
529
530This utility function takes a BLOCK or code reference and "unblocks" it,
531returning the new coderef. This means that the new coderef will return
532immediately without blocking, returning nothing, while the original code
533ref will be called (with parameters) from within its own coroutine.
534
535The reason this function exists is that many event libraries (such as the
536venerable L<Event|Event> module) are not coroutine-safe (a weaker form
537of thread-safety). This means you must not block within event callbacks,
538otherwise you might suffer from crashes or worse.
539
540This function allows your callbacks to block by executing them in another
541coroutine where it is safe to block. One example where blocking is handy
542is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
543disk.
544
545In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
546creating event callbacks that want to block.
547
548=cut
549
550our @unblock_queue;
551
552# we create a special coro because we want to cede,
553# to reduce pressure on the coro pool (because most callbacks
554# return immediately and can be reused) and because we cannot cede
555# inside an event callback.
556our $unblock_scheduler = new Coro sub {
557 while () {
558 while (my $cb = pop @unblock_queue) {
559 # this is an inlined copy of async_pool
560 my $coro = (pop @async_pool) || new Coro \&pool_handler;
561
562 $coro->{_invoke} = $cb;
563 $coro->ready;
564 cede; # for short-lived callbacks, this reduces pressure on the coro pool
565 }
566 schedule; # sleep well
567 }
568};
569$unblock_scheduler->desc ("[unblock_sub scheduler]");
570
571sub unblock_sub(&) {
572 my $cb = shift;
573
574 sub {
575 unshift @unblock_queue, [$cb, @_];
576 $unblock_scheduler->ready;
577 }
578}
579
580=back
581
247=cut 582=cut
248 583
2491; 5841;
250 585
251=head1 BUGS/LIMITATIONS 586=head1 BUGS/LIMITATIONS
252 587
253 - could be faster, especially when the core would introduce special 588 - you must make very sure that no coro is still active on global
254 support for coroutines (like it does for threads). 589 destruction. very bad things might happen otherwise (usually segfaults).
255 - there is still a memleak on coroutine termination that I could not 590
256 identify. Could be as small as a single SV.
257 - this module is not well-tested.
258 - if variables or arguments "disappear" (become undef) or become
259 corrupted please contact the author so he cen iron out the
260 remaining bugs.
261 - this module is not thread-safe. You must only ever use this module from 591 - this module is not thread-safe. You should only ever use this module
262 the same thread (this requirement might be loosened in the future to 592 from the same thread (this requirement might be loosened in the future
263 allow per-thread schedulers, but Coro::State does not yet allow this). 593 to allow per-thread schedulers, but Coro::State does not yet allow
594 this).
264 595
265=head1 SEE ALSO 596=head1 SEE ALSO
266 597
267L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 598Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
268L<Coro::Signal>, L<Coro::State>, L<Coro::Event>. 599
600Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
601
602Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
603
604Embedding: L<Coro:MakeMaker>
269 605
270=head1 AUTHOR 606=head1 AUTHOR
271 607
272 Marc Lehmann <pcg@goof.com> 608 Marc Lehmann <schmorp@schmorp.de>
273 http://www.goof.com/pcg/marc/ 609 http://home.schmorp.de/
274 610
275=cut 611=cut
276 612

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