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Revision 1.89 by root, Mon Nov 27 02:01:33 2006 UTC vs.
Revision 1.148 by root, Fri Oct 5 20:11:25 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
41 50
42our $idle; # idle handler 51our $idle; # idle handler
43our $main; # main coroutine 52our $main; # main coroutine
44our $current; # current coroutine 53our $current; # current coroutine
45 54
46our $VERSION = '3.0'; 55our $VERSION = '4.01';
47 56
48our @EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
49our %EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
50 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
51); 60);
52our @EXPORT_OK = @{$EXPORT_TAGS{prio}}; 61our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
53 62
54{ 63{
55 my @async; 64 my @async;
56 my $init; 65 my $init;
57 66
58 # this way of handling attributes simply is NOT scalable ;() 67 # this way of handling attributes simply is NOT scalable ;()
59 sub import { 68 sub import {
60 no strict 'refs'; 69 no strict 'refs';
61 70
62 Coro->export_to_level(1, @_); 71 Coro->export_to_level (1, @_);
63 72
64 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; 73 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
65 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { 74 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
66 my ($package, $ref) = (shift, shift); 75 my ($package, $ref) = (shift, shift);
67 my @attrs; 76 my @attrs;
99 108
100The current coroutine (the last coroutine switched to). The initial value 109The current coroutine (the last coroutine switched to). The initial value
101is C<$main> (of course). 110is C<$main> (of course).
102 111
103This variable is B<strictly> I<read-only>. It is provided for performance 112This variable is B<strictly> I<read-only>. It is provided for performance
104reasons. If performance is not essentiel you are encouraged to use the 113reasons. If performance is not essential you are encouraged to use the
105C<Coro::current> function instead. 114C<Coro::current> function instead.
106 115
107=cut 116=cut
108 117
118$main->{desc} = "[main::]";
119
109# maybe some other module used Coro::Specific before... 120# maybe some other module used Coro::Specific before...
110if ($current) {
111 $main->{specific} = $current->{specific}; 121$main->{_specific} = $current->{_specific}
112} 122 if $current;
113 123
114$current = $main; 124_set_current $main;
115 125
116sub current() { $current } 126sub current() { $current }
117 127
118=item $idle 128=item $idle
119 129
120A callback that is called whenever the scheduler finds no ready coroutines 130A callback that is called whenever the scheduler finds no ready coroutines
121to run. The default implementation prints "FATAL: deadlock detected" and 131to run. The default implementation prints "FATAL: deadlock detected" and
122exits. 132exits, because the program has no other way to continue.
123 133
124This hook is overwritten by modules such as C<Coro::Timer> and 134This hook is overwritten by modules such as C<Coro::Timer> and
125C<Coro::Event> to wait on an external event that hopefully wakes up some 135C<Coro::Event> to wait on an external event that hopefully wake up a
126coroutine. 136coroutine so the scheduler can run it.
137
138Please note that if your callback recursively invokes perl (e.g. for event
139handlers), then it must be prepared to be called recursively.
127 140
128=cut 141=cut
129 142
130$idle = sub { 143$idle = sub {
131 print STDERR "FATAL: deadlock detected\n"; 144 require Carp;
132 exit (51); 145 Carp::croak ("FATAL: deadlock detected");
133}; 146};
147
148sub _cancel {
149 my ($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->{_on_destroy}) || []};
158}
134 159
135# this coroutine is necessary because a coroutine 160# this coroutine is necessary because a coroutine
136# cannot destroy itself. 161# cannot destroy itself.
137my @destroy; 162my @destroy;
163my $manager;
164
138my $manager; $manager = new Coro sub { 165$manager = new Coro sub {
139 while () { 166 while () {
140 # by overwriting the state object with the manager we destroy it 167 (shift @destroy)->_cancel
141 # while still being able to schedule this coroutine (in case it has
142 # been readied multiple times. this is harmless since the manager
143 # can be called as many times as neccessary and will always
144 # remove itself from the runqueue
145 while (@destroy) { 168 while @destroy;
146 my $coro = pop @destroy;
147 $coro->{status} ||= [];
148 $_->ready for @{delete $coro->{join} || []};
149 169
150 # the next line destroys the coro state, but keeps the
151 # process itself intact (we basically make it a zombie
152 # process that always runs the manager thread, so it's possible
153 # to transfer() to this process).
154 $coro->_clone_state_from ($manager);
155 }
156 &schedule; 170 &schedule;
157 } 171 }
158}; 172};
173$manager->desc ("[coro manager]");
174$manager->prio (PRIO_MAX);
159 175
160# static methods. not really. 176# static methods. not really.
161 177
162=back 178=back
163 179
164=head2 STATIC METHODS 180=head2 STATIC METHODS
165 181
166Static methods are actually functions that operate on the current process only. 182Static methods are actually functions that operate on the current coroutine only.
167 183
168=over 4 184=over 4
169 185
170=item async { ... } [@args...] 186=item async { ... } [@args...]
171 187
172Create a new asynchronous process and return it's process object 188Create a new asynchronous coroutine and return it's coroutine object
173(usually unused). When the sub returns the new process is automatically 189(usually unused). When the sub returns the new coroutine is automatically
174terminated. 190terminated.
175 191
176Calling C<exit> in a coroutine will not work correctly, so do not do that. 192See the C<Coro::State::new> constructor for info about the coroutine
193environment.
177 194
178When the coroutine dies, the program will exit, just as in the main 195Calling C<exit> in a coroutine will do the same as calling exit outside
179program. 196the coroutine. Likewise, when the coroutine dies, the program will exit,
197just as it would in the main program.
180 198
181 # create a new coroutine that just prints its arguments 199 # create a new coroutine that just prints its arguments
182 async { 200 async {
183 print "@_\n"; 201 print "@_\n";
184 } 1,2,3,4; 202 } 1,2,3,4;
185 203
186=cut 204=cut
187 205
188sub async(&@) { 206sub async(&@) {
189 my $pid = new Coro @_; 207 my $coro = new Coro @_;
190 $pid->ready; 208 $coro->ready;
191 $pid 209 $coro
210}
211
212=item async_pool { ... } [@args...]
213
214Similar to C<async>, but uses a coroutine pool, so you should not call
215terminate or join (although you are allowed to), and you get a coroutine
216that might have executed other code already (which can be good or bad :).
217
218Also, the block is executed in an C<eval> context and a warning will be
219issued in case of an exception instead of terminating the program, as
220C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
221will not work in the expected way, unless you call terminate or cancel,
222which somehow defeats the purpose of pooling.
223
224The priority will be reset to C<0> after each job, tracing will be
225disabled, the description will be reset and the default output filehandle
226gets restored, so you can change alkl these. Otherwise the coroutine will
227be re-used "as-is": most notably if you change other per-coroutine global
228stuff such as C<$/> you need to revert that change, which is most simply
229done by using local as in C< local $/ >.
230
231The pool size is limited to 8 idle coroutines (this can be adjusted by
232changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
233required.
234
235If you are concerned about pooled coroutines growing a lot because a
236single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
237{ terminate }> once per second or so to slowly replenish the pool. In
238addition to that, when the stacks used by a handler grows larger than 16kb
239(adjustable with $Coro::POOL_RSS) it will also exit.
240
241=cut
242
243our $POOL_SIZE = 8;
244our $POOL_RSS = 16 * 1024;
245our @async_pool;
246
247sub pool_handler {
248 my $cb;
249
250 while () {
251 eval {
252 while () {
253 _pool_1 $cb;
254 &$cb;
255 _pool_2 $cb;
256 &schedule;
257 }
258 };
259
260 last if $@ eq "\3terminate\2\n";
261 warn $@ if $@;
262 }
263}
264
265sub async_pool(&@) {
266 # this is also inlined into the unlock_scheduler
267 my $coro = (pop @async_pool) || new Coro \&pool_handler;
268
269 $coro->{_invoke} = [@_];
270 $coro->ready;
271
272 $coro
192} 273}
193 274
194=item schedule 275=item schedule
195 276
196Calls the scheduler. Please note that the current process will not be put 277Calls the scheduler. Please note that the current coroutine will not be put
197into the ready queue, so calling this function usually means you will 278into the ready queue, so calling this function usually means you will
198never be called again. 279never be called again unless something else (e.g. an event handler) calls
280ready.
199 281
200=cut 282The canonical way to wait on external events is this:
283
284 {
285 # remember current coroutine
286 my $current = $Coro::current;
287
288 # register a hypothetical event handler
289 on_event_invoke sub {
290 # wake up sleeping coroutine
291 $current->ready;
292 undef $current;
293 };
294
295 # call schedule until event occurred.
296 # in case we are woken up for other reasons
297 # (current still defined), loop.
298 Coro::schedule while $current;
299 }
201 300
202=item cede 301=item cede
203 302
204"Cede" to other processes. This function puts the current process into the 303"Cede" to other coroutines. This function puts the current coroutine into the
205ready queue and calls C<schedule>, which has the effect of giving up the 304ready queue and calls C<schedule>, which has the effect of giving up the
206current "timeslice" to other coroutines of the same or higher priority. 305current "timeslice" to other coroutines of the same or higher priority.
207 306
208=cut 307Returns true if at least one coroutine switch has happened.
308
309=item Coro::cede_notself
310
311Works like cede, but is not exported by default and will cede to any
312coroutine, regardless of priority, once.
313
314Returns true if at least one coroutine switch has happened.
209 315
210=item terminate [arg...] 316=item terminate [arg...]
211 317
212Terminates the current process with the given status values (see L<cancel>). 318Terminates the current coroutine with the given status values (see L<cancel>).
319
320=item killall
321
322Kills/terminates/cancels all coroutines except the currently running
323one. This is useful after a fork, either in the child or the parent, as
324usually only one of them should inherit the running coroutines.
213 325
214=cut 326=cut
215 327
216sub terminate { 328sub terminate {
217 $current->cancel (@_); 329 $current->cancel (@_);
218} 330}
219 331
332sub killall {
333 for (Coro::State::list) {
334 $_->cancel
335 if $_ != $current && UNIVERSAL::isa $_, "Coro";
336 }
337}
338
220=back 339=back
221 340
222# dynamic methods 341# dynamic methods
223 342
224=head2 PROCESS METHODS 343=head2 COROUTINE METHODS
225 344
226These are the methods you can call on process objects. 345These are the methods you can call on coroutine objects.
227 346
228=over 4 347=over 4
229 348
230=item new Coro \&sub [, @args...] 349=item new Coro \&sub [, @args...]
231 350
232Create a new process and return it. When the sub returns the process 351Create a new coroutine and return it. When the sub returns the coroutine
233automatically terminates as if C<terminate> with the returned values were 352automatically terminates as if C<terminate> with the returned values were
234called. To make the process run you must first put it into the ready queue 353called. To make the coroutine run you must first put it into the ready queue
235by calling the ready method. 354by calling the ready method.
236 355
237Calling C<exit> in a coroutine will not work correctly, so do not do that. 356See C<async> and C<Coro::State::new> for additional info about the
357coroutine environment.
238 358
239=cut 359=cut
240 360
241sub _new_coro { 361sub _run_coro {
242 terminate &{+shift}; 362 terminate &{+shift};
243} 363}
244 364
245sub new { 365sub new {
246 my $class = shift; 366 my $class = shift;
247 367
248 $class->SUPER::new (\&_new_coro, @_) 368 $class->SUPER::new (\&_run_coro, @_)
249} 369}
250 370
251=item $process->ready 371=item $success = $coroutine->ready
252 372
253Put the given process into the ready queue. 373Put the given coroutine into the ready queue (according to it's priority)
374and return true. If the coroutine is already in the ready queue, do nothing
375and return false.
254 376
255=cut 377=item $is_ready = $coroutine->is_ready
256 378
379Return wether the coroutine is currently the ready queue or not,
380
257=item $process->cancel (arg...) 381=item $coroutine->cancel (arg...)
258 382
259Terminates the given process and makes it return the given arguments as 383Terminates the given coroutine and makes it return the given arguments as
260status (default: the empty list). 384status (default: the empty list). Never returns if the coroutine is the
385current coroutine.
261 386
262=cut 387=cut
263 388
264sub cancel { 389sub cancel {
265 my $self = shift; 390 my $self = shift;
266 $self->{status} = [@_]; 391 $self->{_status} = [@_];
392
393 if ($current == $self) {
267 push @destroy, $self; 394 push @destroy, $self;
268 $manager->ready; 395 $manager->ready;
269 &schedule if $current == $self; 396 &schedule while 1;
397 } else {
398 $self->_cancel;
399 }
270} 400}
271 401
272=item $process->join 402=item $coroutine->join
273 403
274Wait until the coroutine terminates and return any values given to the 404Wait until the coroutine terminates and return any values given to the
275C<terminate> or C<cancel> functions. C<join> can be called multiple times 405C<terminate> or C<cancel> functions. C<join> can be called concurrently
276from multiple processes. 406from multiple coroutines.
277 407
278=cut 408=cut
279 409
280sub join { 410sub join {
281 my $self = shift; 411 my $self = shift;
412
282 unless ($self->{status}) { 413 unless ($self->{_status}) {
283 push @{$self->{join}}, $current; 414 my $current = $current;
284 &schedule; 415
416 push @{$self->{_on_destroy}}, sub {
417 $current->ready;
418 undef $current;
419 };
420
421 &schedule while $current;
285 } 422 }
423
286 wantarray ? @{$self->{status}} : $self->{status}[0]; 424 wantarray ? @{$self->{_status}} : $self->{_status}[0];
287} 425}
288 426
427=item $coroutine->on_destroy (\&cb)
428
429Registers a callback that is called when this coroutine gets destroyed,
430but before it is joined. The callback gets passed the terminate arguments,
431if any.
432
433=cut
434
435sub on_destroy {
436 my ($self, $cb) = @_;
437
438 push @{ $self->{_on_destroy} }, $cb;
439}
440
289=item $oldprio = $process->prio ($newprio) 441=item $oldprio = $coroutine->prio ($newprio)
290 442
291Sets (or gets, if the argument is missing) the priority of the 443Sets (or gets, if the argument is missing) the priority of the
292process. Higher priority processes get run before lower priority 444coroutine. Higher priority coroutines get run before lower priority
293processes. Priorities are small signed integers (currently -4 .. +3), 445coroutines. Priorities are small signed integers (currently -4 .. +3),
294that you can refer to using PRIO_xxx constants (use the import tag :prio 446that you can refer to using PRIO_xxx constants (use the import tag :prio
295to get then): 447to get then):
296 448
297 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 449 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
298 3 > 1 > 0 > -1 > -3 > -4 450 3 > 1 > 0 > -1 > -3 > -4
301 current->prio(PRIO_HIGH); 453 current->prio(PRIO_HIGH);
302 454
303The idle coroutine ($Coro::idle) always has a lower priority than any 455The idle coroutine ($Coro::idle) always has a lower priority than any
304existing coroutine. 456existing coroutine.
305 457
306Changing the priority of the current process will take effect immediately, 458Changing the priority of the current coroutine will take effect immediately,
307but changing the priority of processes in the ready queue (but not 459but changing the priority of coroutines in the ready queue (but not
308running) will only take effect after the next schedule (of that 460running) will only take effect after the next schedule (of that
309process). This is a bug that will be fixed in some future version. 461coroutine). This is a bug that will be fixed in some future version.
310 462
311=item $newprio = $process->nice ($change) 463=item $newprio = $coroutine->nice ($change)
312 464
313Similar to C<prio>, but subtract the given value from the priority (i.e. 465Similar to C<prio>, but subtract the given value from the priority (i.e.
314higher values mean lower priority, just as in unix). 466higher values mean lower priority, just as in unix).
315 467
316=item $olddesc = $process->desc ($newdesc) 468=item $olddesc = $coroutine->desc ($newdesc)
317 469
318Sets (or gets in case the argument is missing) the description for this 470Sets (or gets in case the argument is missing) the description for this
319process. This is just a free-form string you can associate with a process. 471coroutine. This is just a free-form string you can associate with a coroutine.
472
473This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
474can modify this member directly if you wish.
320 475
321=cut 476=cut
322 477
323sub desc { 478sub desc {
324 my $old = $_[0]{desc}; 479 my $old = $_[0]{desc};
326 $old; 481 $old;
327} 482}
328 483
329=back 484=back
330 485
486=head2 GLOBAL FUNCTIONS
487
488=over 4
489
490=item Coro::nready
491
492Returns the number of coroutines that are currently in the ready state,
493i.e. that can be switched to. The value C<0> means that the only runnable
494coroutine is the currently running one, so C<cede> would have no effect,
495and C<schedule> would cause a deadlock unless there is an idle handler
496that wakes up some coroutines.
497
498=item my $guard = Coro::guard { ... }
499
500This creates and returns a guard object. Nothing happens until the object
501gets destroyed, in which case the codeblock given as argument will be
502executed. This is useful to free locks or other resources in case of a
503runtime error or when the coroutine gets canceled, as in both cases the
504guard block will be executed. The guard object supports only one method,
505C<< ->cancel >>, which will keep the codeblock from being executed.
506
507Example: set some flag and clear it again when the coroutine gets canceled
508or the function returns:
509
510 sub do_something {
511 my $guard = Coro::guard { $busy = 0 };
512 $busy = 1;
513
514 # do something that requires $busy to be true
515 }
516
517=cut
518
519sub guard(&) {
520 bless \(my $cb = $_[0]), "Coro::guard"
521}
522
523sub Coro::guard::cancel {
524 ${$_[0]} = sub { };
525}
526
527sub Coro::guard::DESTROY {
528 ${$_[0]}->();
529}
530
531
532=item unblock_sub { ... }
533
534This utility function takes a BLOCK or code reference and "unblocks" it,
535returning the new coderef. This means that the new coderef will return
536immediately without blocking, returning nothing, while the original code
537ref will be called (with parameters) from within its own coroutine.
538
539The reason this function exists is that many event libraries (such as the
540venerable L<Event|Event> module) are not coroutine-safe (a weaker form
541of thread-safety). This means you must not block within event callbacks,
542otherwise you might suffer from crashes or worse.
543
544This function allows your callbacks to block by executing them in another
545coroutine where it is safe to block. One example where blocking is handy
546is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
547disk.
548
549In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
550creating event callbacks that want to block.
551
552=cut
553
554our @unblock_queue;
555
556# we create a special coro because we want to cede,
557# to reduce pressure on the coro pool (because most callbacks
558# return immediately and can be reused) and because we cannot cede
559# inside an event callback.
560our $unblock_scheduler = new Coro sub {
561 while () {
562 while (my $cb = pop @unblock_queue) {
563 # this is an inlined copy of async_pool
564 my $coro = (pop @async_pool) || new Coro \&pool_handler;
565
566 $coro->{_invoke} = $cb;
567 $coro->ready;
568 cede; # for short-lived callbacks, this reduces pressure on the coro pool
569 }
570 schedule; # sleep well
571 }
572};
573$unblock_scheduler->desc ("[unblock_sub scheduler]");
574
575sub unblock_sub(&) {
576 my $cb = shift;
577
578 sub {
579 unshift @unblock_queue, [$cb, @_];
580 $unblock_scheduler->ready;
581 }
582}
583
584=back
585
331=cut 586=cut
332 587
3331; 5881;
334 589
335=head1 BUGS/LIMITATIONS 590=head1 BUGS/LIMITATIONS
336 591
337 - you must make very sure that no coro is still active on global 592 - you must make very sure that no coro is still active on global
338 destruction. very bad things might happen otherwise (usually segfaults). 593 destruction. very bad things might happen otherwise (usually segfaults).
339 594
340 - this module is not thread-safe. You should only ever use this module 595 - this module is not thread-safe. You should only ever use this module
341 from the same thread (this requirement might be losened in the future 596 from the same thread (this requirement might be loosened in the future
342 to allow per-thread schedulers, but Coro::State does not yet allow 597 to allow per-thread schedulers, but Coro::State does not yet allow
343 this). 598 this).
344 599
345=head1 SEE ALSO 600=head1 SEE ALSO
346 601
347Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>. 602Support/Utility: L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
348 603
349Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. 604Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
350 605
351Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>. 606Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
352 607

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