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Revision 1.29 by root, Sat Aug 11 00:37:31 2001 UTC vs.
Revision 1.152 by root, Sun Oct 7 13:53:37 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 cede;
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 + C stack), that is, a coroutine has it's own 43@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
30callchain, it's own set of lexicals and it's own set of perl's most 44its own set of lexicals and its own set of perls most important global
31important global variables. 45variables (see L<Coro::State> for more configuration).
32 46
33=cut 47=cut
34 48
35package Coro; 49package Coro;
36 50
51use strict;
52no warnings "uninitialized";
53
37use Coro::State; 54use Coro::State;
38 55
39use base Exporter; 56use base qw(Coro::State Exporter);
40 57
41$VERSION = 0.45; 58our $idle; # idle handler
59our $main; # main coroutine
60our $current; # current coroutine
42 61
62our $VERSION = '4.1';
63
43@EXPORT = qw(async cede schedule terminate current); 64our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
44@EXPORT_OK = qw($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;
48 my $init; 72 my $init;
49 73
50 # this way of handling attributes simply is NOT scalable ;() 74 # this way of handling attributes simply is NOT scalable ;()
51 sub import { 75 sub import {
76 no strict 'refs';
77
52 Coro->export_to_level(1, @_); 78 Coro->export_to_level (1, @_);
79
53 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; 80 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
54 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { 81 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
55 my ($package, $ref) = (shift, shift); 82 my ($package, $ref) = (shift, shift);
56 my @attrs; 83 my @attrs;
57 for (@_) { 84 for (@_) {
72 }; 99 };
73 } 100 }
74 101
75} 102}
76 103
104=over 4
105
77=item $main 106=item $main
78 107
79This coroutine represents the main program. 108This coroutine represents the main program.
80 109
81=cut 110=cut
82 111
83our $main = new Coro; 112$main = new Coro;
84 113
85=item $current (or as function: current) 114=item $current (or as function: current)
86 115
87The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). 116The current coroutine (the last coroutine switched to). The initial value
117is C<$main> (of course).
88 118
119This variable is B<strictly> I<read-only>. It is provided for performance
120reasons. If performance is not essential you are encouraged to use the
121C<Coro::current> function instead.
122
89=cut 123=cut
124
125$main->{desc} = "[main::]";
90 126
91# maybe some other module used Coro::Specific before... 127# maybe some other module used Coro::Specific before...
92if ($current) {
93 $main->{specific} = $current->{specific}; 128$main->{_specific} = $current->{_specific}
94} 129 if $current;
95 130
96our $current = $main; 131_set_current $main;
97 132
98sub current() { $current } 133sub current() { $current }
99 134
100=item $idle 135=item $idle
101 136
102The coroutine to switch to when no other coroutine is running. The default 137A callback that is called whenever the scheduler finds no ready coroutines
103implementation 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.
104 140
105=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.
106 144
107# should be done using priorities :( 145Please note that if your callback recursively invokes perl (e.g. for event
108our $idle = new Coro sub { 146handlers), then it must be prepared to be called recursively itself.
109 print STDERR "FATAL: deadlock detected\n"; 147
110 exit(51); 148=cut
149
150$idle = sub {
151 require Carp;
152 Carp::croak ("FATAL: deadlock detected");
111}; 153};
154
155sub _cancel {
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}
112 166
113# this coroutine is necessary because a coroutine 167# this coroutine is necessary because a coroutine
114# cannot destroy itself. 168# cannot destroy itself.
115my @destroy; 169my @destroy;
170my $manager;
171
116my $manager = new Coro sub { 172$manager = new Coro sub {
117 while() { 173 while () {
118 delete ((pop @destroy)->{_coro_state}) while @destroy; 174 (shift @destroy)->_cancel
175 while @destroy;
176
119 &schedule; 177 &schedule;
120 } 178 }
121}; 179};
122 180$manager->desc ("[coro manager]");
123# we really need priorities... 181$manager->prio (PRIO_MAX);
124my @ready; # the ready queue. hehe, rather broken ;)
125 182
126# static methods. not really. 183# static methods. not really.
127 184
185=back
186
128=head2 STATIC METHODS 187=head2 STATIC METHODS
129 188
130Static methods are actually functions that operate on the current process only. 189Static methods are actually functions that operate on the current coroutine only.
131 190
132=over 4 191=over 4
133 192
134=item async { ... } [@args...] 193=item async { ... } [@args...]
135 194
136Create a new asynchronous process and return it's process object 195Create a new asynchronous coroutine and return it's coroutine object
137(usually unused). When the sub returns the new process is automatically 196(usually unused). When the sub returns the new coroutine is automatically
138terminated. 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.
139 205
140 # create a new coroutine that just prints its arguments 206 # create a new coroutine that just prints its arguments
141 async { 207 async {
142 print "@_\n"; 208 print "@_\n";
143 } 1,2,3,4; 209 } 1,2,3,4;
144 210
145The coderef you submit MUST NOT be a closure that refers to variables
146in an outer scope. This does NOT work. Pass arguments into it instead.
147
148=cut 211=cut
149 212
150sub async(&@) { 213sub async(&@) {
151 my $pid = new Coro @_; 214 my $coro = new Coro @_;
152 $manager->ready; # this ensures that the stack is cloned from the manager
153 $pid->ready; 215 $coro->ready;
154 $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
155} 280}
156 281
157=item schedule 282=item schedule
158 283
159Calls 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
160into the ready queue, so calling this function usually means you will 285into the ready queue, so calling this function usually means you will
161never be called again. 286never be called again unless something else (e.g. an event handler) calls
287ready.
162 288
163=cut 289The canonical way to wait on external events is this:
164 290
165my $prev; 291 {
292 # remember current coroutine
293 my $current = $Coro::current;
166 294
167sub schedule { 295 # register a hypothetical event handler
168 # should be done using priorities :( 296 on_event_invoke sub {
169 ($prev, $current) = ($current, shift @ready || $idle); 297 # wake up sleeping coroutine
170 Coro::State::transfer($prev, $current); 298 $current->ready;
171} 299 undef $current;
300 };
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 }
172 307
173=item cede 308=item cede
174 309
175"Cede" to other processes. This function puts the current process into the 310"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 311ready queue and calls C<schedule>, which has the effect of giving up the
177current "timeslice" to other coroutines of the same or higher priority. 312current "timeslice" to other coroutines of the same or higher priority.
178 313
179=cut 314Returns true if at least one coroutine switch has happened.
180 315
181sub cede { 316=item Coro::cede_notself
182 $current->ready;
183 &schedule;
184}
185 317
318Works like cede, but is not exported by default and will cede to any
319coroutine, regardless of priority, once.
320
321Returns true if at least one coroutine switch has happened.
322
186=item terminate 323=item terminate [arg...]
187 324
188Terminates the current process. 325Terminates the current coroutine with the given status values (see L<cancel>).
189 326
190Future versions of this function will allow result arguments. 327=item killall
328
329Kills/terminates/cancels all coroutines except the currently running
330one. This is useful after a fork, either in the child or the parent, as
331usually only one of them should inherit the running coroutines.
191 332
192=cut 333=cut
193 334
194sub terminate { 335sub terminate {
195 $current->cancel; 336 $current->cancel (@_);
196 &schedule; 337}
197 die; # NORETURN 338
339sub killall {
340 for (Coro::State::list) {
341 $_->cancel
342 if $_ != $current && UNIVERSAL::isa $_, "Coro";
343 }
198} 344}
199 345
200=back 346=back
201 347
202# dynamic methods 348# dynamic methods
203 349
204=head2 PROCESS METHODS 350=head2 COROUTINE METHODS
205 351
206These are the methods you can call on process objects. 352These are the methods you can call on coroutine objects.
207 353
208=over 4 354=over 4
209 355
210=item new Coro \&sub [, @args...] 356=item new Coro \&sub [, @args...]
211 357
212Create a new process and return it. When the sub returns the process 358Create a new coroutine and return it. When the sub returns the coroutine
213automatically terminates. To start the process you must first put it into 359automatically terminates as if C<terminate> with the returned values were
360called. To make the coroutine run you must first put it into the ready queue
214the ready queue by calling the ready method. 361by calling the ready method.
215 362
216The coderef you submit MUST NOT be a closure that refers to variables 363See C<async> and C<Coro::State::new> for additional info about the
217in an outer scope. This does NOT work. Pass arguments into it instead. 364coroutine environment.
218 365
219=cut 366=cut
220 367
221sub _newcoro { 368sub _run_coro {
222 terminate &{+shift}; 369 terminate &{+shift};
223} 370}
224 371
225sub new { 372sub new {
226 my $class = shift; 373 my $class = shift;
227 bless {
228 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
229 }, $class;
230}
231 374
232=item $process->ready 375 $class->SUPER::new (\&_run_coro, @_)
233
234Put the current process into the ready queue.
235
236=cut
237
238sub ready {
239 push @ready, $_[0];
240} 376}
241 377
242=item $process->cancel 378=item $success = $coroutine->ready
243 379
244Like C<terminate>, but terminates the specified process instead. 380Put the given coroutine into the ready queue (according to it's priority)
381and return true. If the coroutine is already in the ready queue, do nothing
382and return false.
383
384=item $is_ready = $coroutine->is_ready
385
386Return wether the coroutine is currently the ready queue or not,
387
388=item $coroutine->cancel (arg...)
389
390Terminates the given coroutine and makes it return the given arguments as
391status (default: the empty list). Never returns if the coroutine is the
392current coroutine.
245 393
246=cut 394=cut
247 395
248sub cancel { 396sub cancel {
397 my $self = shift;
398 $self->{_status} = [@_];
399
400 if ($current == $self) {
249 push @destroy, $_[0]; 401 push @destroy, $self;
250 $manager->ready; 402 $manager->ready;
403 &schedule while 1;
404 } else {
405 $self->_cancel;
406 }
407}
408
409=item $coroutine->join
410
411Wait until the coroutine terminates and return any values given to the
412C<terminate> or C<cancel> functions. C<join> can be called concurrently
413from multiple coroutines.
414
415=cut
416
417sub join {
418 my $self = shift;
419
420 unless ($self->{_status}) {
421 my $current = $current;
422
423 push @{$self->{_on_destroy}}, sub {
424 $current->ready;
425 undef $current;
426 };
427
428 &schedule while $current;
429 }
430
431 wantarray ? @{$self->{_status}} : $self->{_status}[0];
432}
433
434=item $coroutine->on_destroy (\&cb)
435
436Registers a callback that is called when this coroutine gets destroyed,
437but before it is joined. The callback gets passed the terminate arguments,
438if any.
439
440=cut
441
442sub on_destroy {
443 my ($self, $cb) = @_;
444
445 push @{ $self->{_on_destroy} }, $cb;
446}
447
448=item $oldprio = $coroutine->prio ($newprio)
449
450Sets (or gets, if the argument is missing) the priority of the
451coroutine. Higher priority coroutines get run before lower priority
452coroutines. Priorities are small signed integers (currently -4 .. +3),
453that you can refer to using PRIO_xxx constants (use the import tag :prio
454to get then):
455
456 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
457 3 > 1 > 0 > -1 > -3 > -4
458
459 # set priority to HIGH
460 current->prio(PRIO_HIGH);
461
462The idle coroutine ($Coro::idle) always has a lower priority than any
463existing coroutine.
464
465Changing the priority of the current coroutine will take effect immediately,
466but changing the priority of coroutines in the ready queue (but not
467running) will only take effect after the next schedule (of that
468coroutine). This is a bug that will be fixed in some future version.
469
470=item $newprio = $coroutine->nice ($change)
471
472Similar to C<prio>, but subtract the given value from the priority (i.e.
473higher values mean lower priority, just as in unix).
474
475=item $olddesc = $coroutine->desc ($newdesc)
476
477Sets (or gets in case the argument is missing) the description for this
478coroutine. This is just a free-form string you can associate with a coroutine.
479
480This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
481can modify this member directly if you wish.
482
483=item $coroutine->throw ([$scalar])
484
485If C<$throw> is specified and defined, it will be thrown as an exception
486inside the coroutine at the next convinient point in time (usually after
487it gains control at the next schedule/transfer/cede). Otherwise clears the
488exception object.
489
490The exception object will be thrown "as is" with the specified scalar in
491C<$@>, i.e. if it is a string, no line number or newline will be appended
492(unlike with C<die>).
493
494This can be used as a softer means than C<cancel> to ask a coroutine to
495end itself, although there is no guarentee that the exception will lead to
496termination, and if the exception isn't caught it might well end the whole
497program.
498
499=cut
500
501sub desc {
502 my $old = $_[0]{desc};
503 $_[0]{desc} = $_[1] if @_ > 1;
504 $old;
251} 505}
252 506
253=back 507=back
254 508
509=head2 GLOBAL FUNCTIONS
510
511=over 4
512
513=item Coro::nready
514
515Returns the number of coroutines that are currently in the ready state,
516i.e. that can be switched to. The value C<0> means that the only runnable
517coroutine is the currently running one, so C<cede> would have no effect,
518and C<schedule> would cause a deadlock unless there is an idle handler
519that wakes up some coroutines.
520
521=item my $guard = Coro::guard { ... }
522
523This creates and returns a guard object. Nothing happens until the object
524gets destroyed, in which case the codeblock given as argument will be
525executed. This is useful to free locks or other resources in case of a
526runtime error or when the coroutine gets canceled, as in both cases the
527guard block will be executed. The guard object supports only one method,
528C<< ->cancel >>, which will keep the codeblock from being executed.
529
530Example: set some flag and clear it again when the coroutine gets canceled
531or the function returns:
532
533 sub do_something {
534 my $guard = Coro::guard { $busy = 0 };
535 $busy = 1;
536
537 # do something that requires $busy to be true
538 }
539
540=cut
541
542sub guard(&) {
543 bless \(my $cb = $_[0]), "Coro::guard"
544}
545
546sub Coro::guard::cancel {
547 ${$_[0]} = sub { };
548}
549
550sub Coro::guard::DESTROY {
551 ${$_[0]}->();
552}
553
554
555=item unblock_sub { ... }
556
557This utility function takes a BLOCK or code reference and "unblocks" it,
558returning the new coderef. This means that the new coderef will return
559immediately without blocking, returning nothing, while the original code
560ref will be called (with parameters) from within its own coroutine.
561
562The reason this function exists is that many event libraries (such as the
563venerable L<Event|Event> module) are not coroutine-safe (a weaker form
564of thread-safety). This means you must not block within event callbacks,
565otherwise you might suffer from crashes or worse.
566
567This function allows your callbacks to block by executing them in another
568coroutine where it is safe to block. One example where blocking is handy
569is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
570disk.
571
572In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
573creating event callbacks that want to block.
574
575=cut
576
577our @unblock_queue;
578
579# we create a special coro because we want to cede,
580# to reduce pressure on the coro pool (because most callbacks
581# return immediately and can be reused) and because we cannot cede
582# inside an event callback.
583our $unblock_scheduler = new Coro sub {
584 while () {
585 while (my $cb = pop @unblock_queue) {
586 # this is an inlined copy of async_pool
587 my $coro = (pop @async_pool) || new Coro \&pool_handler;
588
589 $coro->{_invoke} = $cb;
590 $coro->ready;
591 cede; # for short-lived callbacks, this reduces pressure on the coro pool
592 }
593 schedule; # sleep well
594 }
595};
596$unblock_scheduler->desc ("[unblock_sub scheduler]");
597
598sub unblock_sub(&) {
599 my $cb = shift;
600
601 sub {
602 unshift @unblock_queue, [$cb, @_];
603 $unblock_scheduler->ready;
604 }
605}
606
607=back
608
255=cut 609=cut
256 610
2571; 6111;
258 612
259=head1 BUGS/LIMITATIONS 613=head1 BUGS/LIMITATIONS
260 614
261 - could be faster, especially when the core would introduce special 615 - you must make very sure that no coro is still active on global
262 support for coroutines (like it does for threads). 616 destruction. very bad things might happen otherwise (usually segfaults).
263 - there is still a memleak on coroutine termination that I could not 617
264 identify. Could be as small as a single SV.
265 - this module is not well-tested.
266 - if variables or arguments "disappear" (become undef) or become
267 corrupted please contact the author so he cen iron out the
268 remaining bugs.
269 - this module is not thread-safe. You must only ever use this module from 618 - this module is not thread-safe. You should only ever use this module
270 the same thread (this requirement might be loosened in the future to 619 from the same thread (this requirement might be loosened in the future
271 allow per-thread schedulers, but Coro::State does not yet allow this). 620 to allow per-thread schedulers, but Coro::State does not yet allow
621 this).
272 622
273=head1 SEE ALSO 623=head1 SEE ALSO
274 624
275L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 625Lower level Configuration, Coroutine Environment: L<Coro::State>.
276L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>, 626
277L<Coro::Handle>, L<Coro::Socket>. 627Debugging: L<Coro::Debug>.
628
629Support/Utility: L<Coro::Specific>, L<Coro::Util>.
630
631Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
632
633Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>.
634
635Compatibility: L<Coro::LWP>, L<Coro::Storable>, L<Coro::Select>.
636
637Embedding: L<Coro:MakeMaker>.
278 638
279=head1 AUTHOR 639=head1 AUTHOR
280 640
281 Marc Lehmann <pcg@goof.com> 641 Marc Lehmann <schmorp@schmorp.de>
282 http://www.goof.com/pcg/marc/ 642 http://home.schmorp.de/
283 643
284=cut 644=cut
285 645

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