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Revision 1.61 by pcg, Fri May 14 13:25:08 2004 UTC vs.
Revision 1.139 by root, Thu Sep 27 15:52:30 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
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).
34
26In this module, coroutines are defined as "callchain + lexical variables 35In this module, coroutines are defined as "callchain + lexical variables +
27+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own 36@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
28callchain, it's own set of lexicals and it's own set of perl's most 37its own set of lexicals and its own set of perls most important global
29important global variables. 38variables.
30 39
31=cut 40=cut
32 41
33package Coro; 42package Coro;
34 43
35BEGIN { eval { require warnings } && warnings->unimport ("uninitialized") } 44use strict;
45no warnings "uninitialized";
36 46
37use Coro::State; 47use Coro::State;
38 48
39use vars qw($idle $main $current); 49use base qw(Coro::State Exporter);
40 50
41use base Exporter; 51our $idle; # idle handler
52our $main; # main coroutine
53our $current; # current coroutine
42 54
43$VERSION = 0.97; 55our $VERSION = '3.8';
44 56
45@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
46%EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
47 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48); 60);
49@EXPORT_OK = @{$EXPORT_TAGS{prio}}; 61our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
50 62
51{ 63{
52 my @async; 64 my @async;
53 my $init; 65 my $init;
54 66
55 # this way of handling attributes simply is NOT scalable ;() 67 # this way of handling attributes simply is NOT scalable ;()
56 sub import { 68 sub import {
69 no strict 'refs';
70
57 Coro->export_to_level(1, @_); 71 Coro->export_to_level (1, @_);
72
58 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; 73 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
59 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { 74 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
60 my ($package, $ref) = (shift, shift); 75 my ($package, $ref) = (shift, shift);
61 my @attrs; 76 my @attrs;
62 for (@_) { 77 for (@_) {
89 104
90$main = new Coro; 105$main = new Coro;
91 106
92=item $current (or as function: current) 107=item $current (or as function: current)
93 108
94The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). 109The current coroutine (the last coroutine switched to). The initial value
110is C<$main> (of course).
95 111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essential you are encouraged to use the
114C<Coro::current> function instead.
115
96=cut 116=cut
117
118$main->{desc} = "[main::]";
97 119
98# maybe some other module used Coro::Specific before... 120# maybe some other module used Coro::Specific before...
99if ($current) {
100 $main->{specific} = $current->{specific}; 121$main->{specific} = $current->{specific}
101} 122 if $current;
102 123
103$current = $main; 124_set_current $main;
104 125
105sub current() { $current } 126sub current() { $current }
106 127
107=item $idle 128=item $idle
108 129
109The coroutine to switch to when no other coroutine is running. The default 130A callback that is called whenever the scheduler finds no ready coroutines
110implementation prints "FATAL: deadlock detected" and exits. 131to run. The default implementation prints "FATAL: deadlock detected" and
132exits, because the program has no other way to continue.
111 133
112=cut 134This hook is overwritten by modules such as C<Coro::Timer> and
135C<Coro::Event> to wait on an external event that hopefully wake up a
136coroutine so the scheduler can run it.
113 137
114# should be done using priorities :( 138Please note that if your callback recursively invokes perl (e.g. for event
115$idle = new Coro sub { 139handlers), then it must be prepared to be called recursively.
116 print STDERR "FATAL: deadlock detected\n"; 140
117 exit(51); 141=cut
142
143$idle = sub {
144 require Carp;
145 Carp::croak ("FATAL: deadlock detected");
118}; 146};
147
148sub _cancel {
149 my ($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 $self->{destroy_cb}) || []};
158}
159
160sub _do_trace_sub {
161 &{$current->{_trace_sub_cb}}
162}
163
164sub _do_trace_line {
165 &{$current->{_trace_line_cb}}
166}
119 167
120# this coroutine is necessary because a coroutine 168# this coroutine is necessary because a coroutine
121# cannot destroy itself. 169# cannot destroy itself.
122my @destroy; 170my @destroy;
123my $manager; 171my $manager;
172
124$manager = new Coro sub { 173$manager = new Coro sub {
125 while () { 174 while () {
126 # by overwriting the state object with the manager we destroy it 175 (shift @destroy)->_cancel
127 # while still being able to schedule this coroutine (in case it has
128 # been readied multiple times. this is harmless since the manager
129 # can be called as many times as neccessary and will always
130 # remove itself from the runqueue
131 while (@destroy) { 176 while @destroy;
132 my $coro = pop @destroy;
133 $coro->{status} ||= [];
134 $_->ready for @{delete $coro->{join} || []};
135 177
136 # the next line destroys the _coro_state, but keeps the
137 # process itself intact (we basically make it a zombie
138 # process that always runs the manager thread, so it's possible
139 # to transfer() to this process).
140 $coro->{_coro_state} = $manager->{_coro_state};
141 }
142 &schedule; 178 &schedule;
143 } 179 }
144}; 180};
181$manager->desc ("[coro manager]");
182$manager->prio (PRIO_MAX);
145 183
146# static methods. not really. 184# static methods. not really.
147 185
148=back 186=back
149 187
150=head2 STATIC METHODS 188=head2 STATIC METHODS
151 189
152Static methods are actually functions that operate on the current process only. 190Static methods are actually functions that operate on the current coroutine only.
153 191
154=over 4 192=over 4
155 193
156=item async { ... } [@args...] 194=item async { ... } [@args...]
157 195
158Create a new asynchronous process and return it's process object 196Create a new asynchronous coroutine and return it's coroutine object
159(usually unused). When the sub returns the new process is automatically 197(usually unused). When the sub returns the new coroutine is automatically
160terminated. 198terminated.
199
200Calling C<exit> in a coroutine will do the same as calling exit outside
201the coroutine. Likewise, when the coroutine dies, the program will exit,
202just as it would in the main program.
161 203
162 # create a new coroutine that just prints its arguments 204 # create a new coroutine that just prints its arguments
163 async { 205 async {
164 print "@_\n"; 206 print "@_\n";
165 } 1,2,3,4; 207 } 1,2,3,4;
166 208
167=cut 209=cut
168 210
169sub async(&@) { 211sub async(&@) {
170 my $pid = new Coro @_; 212 my $coro = new Coro @_;
171 $manager->ready; # this ensures that the stack is cloned from the manager
172 $pid->ready; 213 $coro->ready;
173 $pid; 214 $coro
215}
216
217=item async_pool { ... } [@args...]
218
219Similar to C<async>, but uses a coroutine pool, so you should not call
220terminate or join (although you are allowed to), and you get a coroutine
221that might have executed other code already (which can be good or bad :).
222
223Also, the block is executed in an C<eval> context and a warning will be
224issued in case of an exception instead of terminating the program, as
225C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
226will not work in the expected way, unless you call terminate or cancel,
227which somehow defeats the purpose of pooling.
228
229The priority will be reset to C<0> after each job, otherwise the coroutine
230will be re-used "as-is".
231
232The pool size is limited to 8 idle coroutines (this can be adjusted by
233changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
234required.
235
236If you are concerned about pooled coroutines growing a lot because a
237single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
238{ terminate }> once per second or so to slowly replenish the pool. In
239addition to that, when the stacks used by a handler grows larger than 16kb
240(adjustable with $Coro::POOL_RSS) it will also exit.
241
242=cut
243
244our $POOL_SIZE = 8;
245our $POOL_RSS = 16 * 1024;
246our @async_pool;
247
248sub pool_handler {
249 my $cb;
250
251 while () {
252 eval {
253 while () {
254 _pool_1 $cb;
255 &$cb;
256 _pool_2 $cb;
257 &schedule;
258 }
259 };
260
261 last if $@ eq "\3terminate\2\n";
262 warn $@ if $@;
263 }
264}
265
266sub async_pool(&@) {
267 # this is also inlined into the unlock_scheduler
268 my $coro = (pop @async_pool) || new Coro \&pool_handler;
269
270 $coro->{_invoke} = [@_];
271 $coro->ready;
272
273 $coro
174} 274}
175 275
176=item schedule 276=item schedule
177 277
178Calls the scheduler. Please note that the current process will not be put 278Calls the scheduler. Please note that the current coroutine will not be put
179into the ready queue, so calling this function usually means you will 279into the ready queue, so calling this function usually means you will
180never be called again. 280never be called again unless something else (e.g. an event handler) calls
281ready.
181 282
182=cut 283The canonical way to wait on external events is this:
284
285 {
286 # remember current coroutine
287 my $current = $Coro::current;
288
289 # register a hypothetical event handler
290 on_event_invoke sub {
291 # wake up sleeping coroutine
292 $current->ready;
293 undef $current;
294 };
295
296 # call schedule until event occurred.
297 # in case we are woken up for other reasons
298 # (current still defined), loop.
299 Coro::schedule while $current;
300 }
183 301
184=item cede 302=item cede
185 303
186"Cede" to other processes. This function puts the current process into the 304"Cede" to other coroutines. This function puts the current coroutine into the
187ready queue and calls C<schedule>, which has the effect of giving up the 305ready queue and calls C<schedule>, which has the effect of giving up the
188current "timeslice" to other coroutines of the same or higher priority. 306current "timeslice" to other coroutines of the same or higher priority.
189 307
190=cut 308Returns true if at least one coroutine switch has happened.
309
310=item Coro::cede_notself
311
312Works like cede, but is not exported by default and will cede to any
313coroutine, regardless of priority, once.
314
315Returns true if at least one coroutine switch has happened.
191 316
192=item terminate [arg...] 317=item terminate [arg...]
193 318
194Terminates the current process with the given status values (see L<cancel>). 319Terminates the current coroutine with the given status values (see L<cancel>).
195 320
196=cut 321=cut
197 322
198sub terminate { 323sub terminate {
199 $current->cancel (@_); 324 $current->cancel (@_);
201 326
202=back 327=back
203 328
204# dynamic methods 329# dynamic methods
205 330
206=head2 PROCESS METHODS 331=head2 COROUTINE METHODS
207 332
208These are the methods you can call on process objects. 333These are the methods you can call on coroutine objects.
209 334
210=over 4 335=over 4
211 336
212=item new Coro \&sub [, @args...] 337=item new Coro \&sub [, @args...]
213 338
214Create a new process and return it. When the sub returns the process 339Create a new coroutine and return it. When the sub returns the coroutine
215automatically terminates as if C<terminate> with the returned values were 340automatically terminates as if C<terminate> with the returned values were
216called. To make the process run you must first put it into the ready queue 341called. To make the coroutine run you must first put it into the ready queue
217by calling the ready method. 342by calling the ready method.
218 343
219=cut 344See C<async> for additional discussion.
220 345
346=cut
347
221sub _newcoro { 348sub _run_coro {
222 terminate &{+shift}; 349 terminate &{+shift};
223} 350}
224 351
225sub new { 352sub new {
226 my $class = shift; 353 my $class = shift;
227 bless {
228 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
229 }, $class;
230}
231 354
232=item $process->ready 355 $class->SUPER::new (\&_run_coro, @_)
356}
233 357
234Put the given process into the ready queue. 358=item $success = $coroutine->ready
235 359
236=cut 360Put the given coroutine into the ready queue (according to it's priority)
361and return true. If the coroutine is already in the ready queue, do nothing
362and return false.
237 363
364=item $is_ready = $coroutine->is_ready
365
366Return wether the coroutine is currently the ready queue or not,
367
238=item $process->cancel (arg...) 368=item $coroutine->cancel (arg...)
239 369
240Temrinates the given process and makes it return the given arguments as 370Terminates the given coroutine and makes it return the given arguments as
241status (default: the empty list). 371status (default: the empty list). Never returns if the coroutine is the
372current coroutine.
242 373
243=cut 374=cut
244 375
245sub cancel { 376sub cancel {
246 my $self = shift; 377 my $self = shift;
247 $self->{status} = [@_]; 378 $self->{status} = [@_];
379
380 if ($current == $self) {
248 push @destroy, $self; 381 push @destroy, $self;
249 $manager->ready; 382 $manager->ready;
250 &schedule if $current == $self; 383 &schedule while 1;
384 } else {
385 $self->_cancel;
386 }
251} 387}
252 388
253=item $process->join 389=item $coroutine->join
254 390
255Wait until the coroutine terminates and return any values given to the 391Wait until the coroutine terminates and return any values given to the
256C<terminate> or C<cancel> functions. C<join> can be called multiple times 392C<terminate> or C<cancel> functions. C<join> can be called multiple times
257from multiple processes. 393from multiple coroutine.
258 394
259=cut 395=cut
260 396
261sub join { 397sub join {
262 my $self = shift; 398 my $self = shift;
399
263 unless ($self->{status}) { 400 unless ($self->{status}) {
264 push @{$self->{join}}, $current; 401 my $current = $current;
265 &schedule; 402
403 push @{$self->{destroy_cb}}, sub {
404 $current->ready;
405 undef $current;
406 };
407
408 &schedule while $current;
266 } 409 }
410
267 wantarray ? @{$self->{status}} : $self->{status}[0]; 411 wantarray ? @{$self->{status}} : $self->{status}[0];
268} 412}
269 413
414=item $coroutine->on_destroy (\&cb)
415
416Registers a callback that is called when this coroutine gets destroyed,
417but before it is joined. The callback gets passed the terminate arguments,
418if any.
419
420=cut
421
422sub on_destroy {
423 my ($self, $cb) = @_;
424
425 push @{ $self->{destroy_cb} }, $cb;
426}
427
270=item $oldprio = $process->prio($newprio) 428=item $oldprio = $coroutine->prio ($newprio)
271 429
272Sets (or gets, if the argument is missing) the priority of the 430Sets (or gets, if the argument is missing) the priority of the
273process. Higher priority processes get run before lower priority 431coroutine. Higher priority coroutines get run before lower priority
274processes. Priorities are small signed integers (currently -4 .. +3), 432coroutines. Priorities are small signed integers (currently -4 .. +3),
275that you can refer to using PRIO_xxx constants (use the import tag :prio 433that you can refer to using PRIO_xxx constants (use the import tag :prio
276to get then): 434to get then):
277 435
278 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 436 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
279 3 > 1 > 0 > -1 > -3 > -4 437 3 > 1 > 0 > -1 > -3 > -4
282 current->prio(PRIO_HIGH); 440 current->prio(PRIO_HIGH);
283 441
284The idle coroutine ($Coro::idle) always has a lower priority than any 442The idle coroutine ($Coro::idle) always has a lower priority than any
285existing coroutine. 443existing coroutine.
286 444
287Changing the priority of the current process will take effect immediately, 445Changing the priority of the current coroutine will take effect immediately,
288but changing the priority of processes in the ready queue (but not 446but changing the priority of coroutines in the ready queue (but not
289running) will only take effect after the next schedule (of that 447running) will only take effect after the next schedule (of that
290process). This is a bug that will be fixed in some future version. 448coroutine). This is a bug that will be fixed in some future version.
291 449
292=cut
293
294sub prio {
295 my $old = $_[0]{prio};
296 $_[0]{prio} = $_[1] if @_ > 1;
297 $old;
298}
299
300=item $newprio = $process->nice($change) 450=item $newprio = $coroutine->nice ($change)
301 451
302Similar to C<prio>, but subtract the given value from the priority (i.e. 452Similar to C<prio>, but subtract the given value from the priority (i.e.
303higher values mean lower priority, just as in unix). 453higher values mean lower priority, just as in unix).
304 454
305=cut
306
307sub nice {
308 $_[0]{prio} -= $_[1];
309}
310
311=item $olddesc = $process->desc($newdesc) 455=item $olddesc = $coroutine->desc ($newdesc)
312 456
313Sets (or gets in case the argument is missing) the description for this 457Sets (or gets in case the argument is missing) the description for this
314process. This is just a free-form string you can associate with a process. 458coroutine. This is just a free-form string you can associate with a coroutine.
315 459
316=cut 460=cut
317 461
318sub desc { 462sub desc {
319 my $old = $_[0]{desc}; 463 my $old = $_[0]{desc};
321 $old; 465 $old;
322} 466}
323 467
324=back 468=back
325 469
470=head2 GLOBAL FUNCTIONS
471
472=over 4
473
474=item Coro::nready
475
476Returns the number of coroutines that are currently in the ready state,
477i.e. that can be switched to. The value C<0> means that the only runnable
478coroutine is the currently running one, so C<cede> would have no effect,
479and C<schedule> would cause a deadlock unless there is an idle handler
480that wakes up some coroutines.
481
482=item my $guard = Coro::guard { ... }
483
484This creates and returns a guard object. Nothing happens until the object
485gets destroyed, in which case the codeblock given as argument will be
486executed. This is useful to free locks or other resources in case of a
487runtime error or when the coroutine gets canceled, as in both cases the
488guard block will be executed. The guard object supports only one method,
489C<< ->cancel >>, which will keep the codeblock from being executed.
490
491Example: set some flag and clear it again when the coroutine gets canceled
492or the function returns:
493
494 sub do_something {
495 my $guard = Coro::guard { $busy = 0 };
496 $busy = 1;
497
498 # do something that requires $busy to be true
499 }
500
501=cut
502
503sub guard(&) {
504 bless \(my $cb = $_[0]), "Coro::guard"
505}
506
507sub Coro::guard::cancel {
508 ${$_[0]} = sub { };
509}
510
511sub Coro::guard::DESTROY {
512 ${$_[0]}->();
513}
514
515
516=item unblock_sub { ... }
517
518This utility function takes a BLOCK or code reference and "unblocks" it,
519returning the new coderef. This means that the new coderef will return
520immediately without blocking, returning nothing, while the original code
521ref will be called (with parameters) from within its own coroutine.
522
523The reason this function exists is that many event libraries (such as the
524venerable L<Event|Event> module) are not coroutine-safe (a weaker form
525of thread-safety). This means you must not block within event callbacks,
526otherwise you might suffer from crashes or worse.
527
528This function allows your callbacks to block by executing them in another
529coroutine where it is safe to block. One example where blocking is handy
530is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
531disk.
532
533In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
534creating event callbacks that want to block.
535
536=cut
537
538our @unblock_queue;
539
540# we create a special coro because we want to cede,
541# to reduce pressure on the coro pool (because most callbacks
542# return immediately and can be reused) and because we cannot cede
543# inside an event callback.
544our $unblock_scheduler = new Coro sub {
545 while () {
546 while (my $cb = pop @unblock_queue) {
547 # this is an inlined copy of async_pool
548 my $coro = (pop @async_pool) || new Coro \&pool_handler;
549
550 $coro->{_invoke} = $cb;
551 $coro->ready;
552 cede; # for short-lived callbacks, this reduces pressure on the coro pool
553 }
554 schedule; # sleep well
555 }
556};
557$unblock_scheduler->desc ("[unblock_sub scheduler]");
558
559sub unblock_sub(&) {
560 my $cb = shift;
561
562 sub {
563 unshift @unblock_queue, [$cb, @_];
564 $unblock_scheduler->ready;
565 }
566}
567
568=back
569
326=cut 570=cut
327 571
3281; 5721;
329 573
330=head1 BUGS/LIMITATIONS 574=head1 BUGS/LIMITATIONS
331 575
332 - you must make very sure that no coro is still active on global 576 - you must make very sure that no coro is still active on global
333 destruction. very bad things might happen otherwise (usually segfaults). 577 destruction. very bad things might happen otherwise (usually segfaults).
334 578
335 - this module is not thread-safe. You should only ever use this module 579 - this module is not thread-safe. You should only ever use this module
336 from the same thread (this requirement might be losened in the future 580 from the same thread (this requirement might be loosened in the future
337 to allow per-thread schedulers, but Coro::State does not yet allow 581 to allow per-thread schedulers, but Coro::State does not yet allow
338 this). 582 this).
339 583
340=head1 SEE ALSO 584=head1 SEE ALSO
341 585
342L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 586Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
343L<Coro::Signal>, L<Coro::State>, L<Coro::Timer>, L<Coro::Event>, 587
344L<Coro::L<Coro::RWLock>, Handle>, L<Coro::Socket>. 588Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
589
590Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
591
592Embedding: L<Coro:MakeMaker>
345 593
346=head1 AUTHOR 594=head1 AUTHOR
347 595
348 Marc Lehmann <pcg@goof.com> 596 Marc Lehmann <schmorp@schmorp.de>
349 http://www.goof.com/pcg/marc/ 597 http://home.schmorp.de/
350 598
351=cut 599=cut
352 600

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