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Revision 1.54 by pcg, Sun Sep 28 09:00:48 2003 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@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
28callchain, it's own set of lexicals and it's own set of perl's most 37its own set of lexicals and its own set of perls most important global
29important global variables. 38variables.
30 39
31=cut 40=cut
32 41
33package Coro; 42package Coro;
34 43
44use strict;
35no warnings qw(uninitialized); 45no warnings "uninitialized";
36 46
37use Coro::State; 47use Coro::State;
38 48
39use base Exporter; 49use base qw(Coro::State Exporter);
40 50
41$VERSION = 0.7; 51our $idle; # idle handler
52our $main; # main coroutine
53our $current; # current coroutine
42 54
55our $VERSION = '3.8';
56
43@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
44%EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
45 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
46); 60);
47@EXPORT_OK = @{$EXPORT_TAGS{prio}}; 61our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
48 62
49{ 63{
50 my @async; 64 my @async;
51 my $init; 65 my $init;
52 66
53 # this way of handling attributes simply is NOT scalable ;() 67 # this way of handling attributes simply is NOT scalable ;()
54 sub import { 68 sub import {
69 no strict 'refs';
70
55 Coro->export_to_level(1, @_); 71 Coro->export_to_level (1, @_);
72
56 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; 73 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
57 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { 74 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
58 my ($package, $ref) = (shift, shift); 75 my ($package, $ref) = (shift, shift);
59 my @attrs; 76 my @attrs;
60 for (@_) { 77 for (@_) {
83 100
84This coroutine represents the main program. 101This coroutine represents the main program.
85 102
86=cut 103=cut
87 104
88our $main = new Coro; 105$main = new Coro;
89 106
90=item $current (or as function: current) 107=item $current (or as function: current)
91 108
92The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). 109The current coroutine (the last coroutine switched to). The initial value
110is C<$main> (of course).
93 111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essential you are encouraged to use the
114C<Coro::current> function instead.
115
94=cut 116=cut
117
118$main->{desc} = "[main::]";
95 119
96# maybe some other module used Coro::Specific before... 120# maybe some other module used Coro::Specific before...
97if ($current) {
98 $main->{specific} = $current->{specific}; 121$main->{specific} = $current->{specific}
99} 122 if $current;
100 123
101our $current = $main; 124_set_current $main;
102 125
103sub current() { $current } 126sub current() { $current }
104 127
105=item $idle 128=item $idle
106 129
107The coroutine to switch to when no other coroutine is running. The default 130A callback that is called whenever the scheduler finds no ready coroutines
108implementation 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.
109 133
110=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.
111 137
112# should be done using priorities :( 138Please note that if your callback recursively invokes perl (e.g. for event
113our $idle = new Coro sub { 139handlers), then it must be prepared to be called recursively.
114 print STDERR "FATAL: deadlock detected\n"; 140
115 exit(51); 141=cut
142
143$idle = sub {
144 require Carp;
145 Carp::croak ("FATAL: deadlock detected");
116}; 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}
117 167
118# this coroutine is necessary because a coroutine 168# this coroutine is necessary because a coroutine
119# cannot destroy itself. 169# cannot destroy itself.
120my @destroy; 170my @destroy;
121my $manager; 171my $manager;
172
122$manager = new Coro sub { 173$manager = new Coro sub {
123 while() { 174 while () {
124 # by overwriting the state object with the manager we destroy it 175 (shift @destroy)->_cancel
125 # while still being able to schedule this coroutine (in case it has
126 # been readied multiple times. this is harmless since the manager
127 # can be called as many times as neccessary and will always
128 # remove itself from the runqueue
129 while (@destroy) { 176 while @destroy;
130 my $coro = pop @destroy; 177
131 $coro->{status} ||= [];
132 $_->ready for @{delete $coro->{join} || []};
133 $coro->{_coro_state} = $manager->{_coro_state};
134 }
135 &schedule; 178 &schedule;
136 } 179 }
137}; 180};
181$manager->desc ("[coro manager]");
182$manager->prio (PRIO_MAX);
138 183
139# static methods. not really. 184# static methods. not really.
140 185
141=back 186=back
142 187
143=head2 STATIC METHODS 188=head2 STATIC METHODS
144 189
145Static methods are actually functions that operate on the current process only. 190Static methods are actually functions that operate on the current coroutine only.
146 191
147=over 4 192=over 4
148 193
149=item async { ... } [@args...] 194=item async { ... } [@args...]
150 195
151Create a new asynchronous process and return it's process object 196Create a new asynchronous coroutine and return it's coroutine object
152(usually unused). When the sub returns the new process is automatically 197(usually unused). When the sub returns the new coroutine is automatically
153terminated. 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.
154 203
155 # create a new coroutine that just prints its arguments 204 # create a new coroutine that just prints its arguments
156 async { 205 async {
157 print "@_\n"; 206 print "@_\n";
158 } 1,2,3,4; 207 } 1,2,3,4;
159 208
160The coderef you submit MUST NOT be a closure that refers to variables
161in an outer scope. This does NOT work. Pass arguments into it instead.
162
163=cut 209=cut
164 210
165sub async(&@) { 211sub async(&@) {
166 my $pid = new Coro @_; 212 my $coro = new Coro @_;
167 $manager->ready; # this ensures that the stack is cloned from the manager
168 $pid->ready; 213 $coro->ready;
169 $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
170} 274}
171 275
172=item schedule 276=item schedule
173 277
174Calls 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
175into the ready queue, so calling this function usually means you will 279into the ready queue, so calling this function usually means you will
176never be called again. 280never be called again unless something else (e.g. an event handler) calls
281ready.
177 282
178=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 }
179 301
180=item cede 302=item cede
181 303
182"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
183ready 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
184current "timeslice" to other coroutines of the same or higher priority. 306current "timeslice" to other coroutines of the same or higher priority.
185 307
186=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.
187 316
188=item terminate [arg...] 317=item terminate [arg...]
189 318
190Terminates the current process. 319Terminates the current coroutine with the given status values (see L<cancel>).
191
192Future versions of this function will allow result arguments.
193 320
194=cut 321=cut
195 322
196sub terminate { 323sub terminate {
197 $current->{status} = [@_];
198 $current->cancel; 324 $current->cancel (@_);
199 &schedule;
200 die; # NORETURN
201} 325}
202 326
203=back 327=back
204 328
205# dynamic methods 329# dynamic methods
206 330
207=head2 PROCESS METHODS 331=head2 COROUTINE METHODS
208 332
209These are the methods you can call on process objects. 333These are the methods you can call on coroutine objects.
210 334
211=over 4 335=over 4
212 336
213=item new Coro \&sub [, @args...] 337=item new Coro \&sub [, @args...]
214 338
215Create 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
216automatically terminates as if C<terminate> with the returned values were 340automatically terminates as if C<terminate> with the returned values were
217called. 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
218by calling the ready method. 342by calling the ready method.
219 343
220=cut 344See C<async> for additional discussion.
221 345
346=cut
347
222sub _newcoro { 348sub _run_coro {
223 terminate &{+shift}; 349 terminate &{+shift};
224} 350}
225 351
226sub new { 352sub new {
227 my $class = shift; 353 my $class = shift;
228 bless {
229 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
230 }, $class;
231}
232 354
233=item $process->ready 355 $class->SUPER::new (\&_run_coro, @_)
356}
234 357
235Put the given process into the ready queue. 358=item $success = $coroutine->ready
236 359
237=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.
238 363
239=item $process->cancel 364=item $is_ready = $coroutine->is_ready
240 365
241Like C<terminate>, but terminates the specified process instead. 366Return wether the coroutine is currently the ready queue or not,
367
368=item $coroutine->cancel (arg...)
369
370Terminates the given coroutine and makes it return the given arguments as
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 {
377 my $self = shift;
378 $self->{status} = [@_];
379
380 if ($current == $self) {
246 push @destroy, $_[0]; 381 push @destroy, $self;
247 $manager->ready; 382 $manager->ready;
248 &schedule if $current == $_[0]; 383 &schedule while 1;
384 } else {
385 $self->_cancel;
386 }
249} 387}
250 388
251=item $process->join 389=item $coroutine->join
252 390
253Wait until the coroutine terminates and return any values given to the 391Wait until the coroutine terminates and return any values given to the
254C<terminate> function. C<join> can be called multiple times from multiple 392C<terminate> or C<cancel> functions. C<join> can be called multiple times
255processes. 393from multiple coroutine.
256 394
257=cut 395=cut
258 396
259sub join { 397sub join {
260 my $self = shift; 398 my $self = shift;
399
261 unless ($self->{status}) { 400 unless ($self->{status}) {
262 push @{$self->{join}}, $current; 401 my $current = $current;
263 &schedule; 402
403 push @{$self->{destroy_cb}}, sub {
404 $current->ready;
405 undef $current;
406 };
407
408 &schedule while $current;
264 } 409 }
410
265 wantarray ? @{$self->{status}} : $self->{status}[0]; 411 wantarray ? @{$self->{status}} : $self->{status}[0];
266} 412}
267 413
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
268=item $oldprio = $process->prio($newprio) 428=item $oldprio = $coroutine->prio ($newprio)
269 429
270Sets (or gets, if the argument is missing) the priority of the 430Sets (or gets, if the argument is missing) the priority of the
271process. Higher priority processes get run before lower priority 431coroutine. Higher priority coroutines get run before lower priority
272processes. Priorities are small signed integers (currently -4 .. +3), 432coroutines. Priorities are small signed integers (currently -4 .. +3),
273that 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
274to get then): 434to get then):
275 435
276 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
277 3 > 1 > 0 > -1 > -3 > -4 437 3 > 1 > 0 > -1 > -3 > -4
280 current->prio(PRIO_HIGH); 440 current->prio(PRIO_HIGH);
281 441
282The idle coroutine ($Coro::idle) always has a lower priority than any 442The idle coroutine ($Coro::idle) always has a lower priority than any
283existing coroutine. 443existing coroutine.
284 444
285Changing the priority of the current process will take effect immediately, 445Changing the priority of the current coroutine will take effect immediately,
286but changing the priority of processes in the ready queue (but not 446but changing the priority of coroutines in the ready queue (but not
287running) will only take effect after the next schedule (of that 447running) will only take effect after the next schedule (of that
288process). 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.
289 449
290=cut
291
292sub prio {
293 my $old = $_[0]{prio};
294 $_[0]{prio} = $_[1] if @_ > 1;
295 $old;
296}
297
298=item $newprio = $process->nice($change) 450=item $newprio = $coroutine->nice ($change)
299 451
300Similar 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.
301higher values mean lower priority, just as in unix). 453higher values mean lower priority, just as in unix).
302 454
303=cut
304
305sub nice {
306 $_[0]{prio} -= $_[1];
307}
308
309=item $olddesc = $process->desc($newdesc) 455=item $olddesc = $coroutine->desc ($newdesc)
310 456
311Sets (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
312process. 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.
313 459
314=cut 460=cut
315 461
316sub desc { 462sub desc {
317 my $old = $_[0]{desc}; 463 my $old = $_[0]{desc};
319 $old; 465 $old;
320} 466}
321 467
322=back 468=back
323 469
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
324=cut 570=cut
325 571
3261; 5721;
327 573
328=head1 BUGS/LIMITATIONS 574=head1 BUGS/LIMITATIONS
329 575
330 - 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
331 destruction. very bad things might happen otherwise (usually segfaults). 577 destruction. very bad things might happen otherwise (usually segfaults).
332 578
333 - 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
334 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
335 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
336 this). 582 this).
337 583
338=head1 SEE ALSO 584=head1 SEE ALSO
339 585
340L<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>.
341L<Coro::Signal>, L<Coro::State>, L<Coro::Timer>, L<Coro::Event>, 587
342L<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>
343 593
344=head1 AUTHOR 594=head1 AUTHOR
345 595
346 Marc Lehmann <pcg@goof.com> 596 Marc Lehmann <schmorp@schmorp.de>
347 http://www.goof.com/pcg/marc/ 597 http://home.schmorp.de/
348 598
349=cut 599=cut
350 600

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