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Revision 1.108 by root, Fri Jan 5 20:00:49 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 use din this module also
26guarentees 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 = 1.1; 55our $VERSION = '3.3';
44 56
45@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
46%EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
47 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48); 60);
49@EXPORT_OK = @{$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<$main> (of course).
111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essentiel you are encouraged to use the
114C<Coro::current> function instead.
95 115
96=cut 116=cut
97 117
98# maybe some other module used Coro::Specific before... 118# maybe some other module used Coro::Specific before...
99if ($current) {
100 $main->{specific} = $current->{specific}; 119$main->{specific} = $current->{specific}
101} 120 if $current;
102 121
103$current = $main; 122_set_current $main;
104 123
105sub current() { $current } 124sub current() { $current }
106 125
107=item $idle 126=item $idle
108 127
109The coroutine to switch to when no other coroutine is running. The default 128A callback that is called whenever the scheduler finds no ready coroutines
110implementation prints "FATAL: deadlock detected" and exits. 129to run. The default implementation prints "FATAL: deadlock detected" and
130exits, because the program has no other way to continue.
111 131
112=cut 132This hook is overwritten by modules such as C<Coro::Timer> and
133C<Coro::Event> to wait on an external event that hopefully wake up a
134coroutine so the scheduler can run it.
113 135
114# should be done using priorities :( 136Please note that if your callback recursively invokes perl (e.g. for event
115$idle = new Coro sub { 137handlers), then it must be prepared to be called recursively.
116 print STDERR "FATAL: deadlock detected\n"; 138
117 exit(51); 139=cut
140
141$idle = sub {
142 require Carp;
143 Carp::croak ("FATAL: deadlock detected");
118}; 144};
145
146sub _cancel {
147 my ($self) = @_;
148
149 # free coroutine data and mark as destructed
150 $self->_destroy
151 or return;
152
153 # call all destruction callbacks
154 $_->(@{$self->{status}})
155 for @{(delete $self->{destroy_cb}) || []};
156}
119 157
120# this coroutine is necessary because a coroutine 158# this coroutine is necessary because a coroutine
121# cannot destroy itself. 159# cannot destroy itself.
122my @destroy; 160my @destroy;
123my $manager; 161my $manager;
162
124$manager = new Coro sub { 163$manager = new Coro sub {
125 while () { 164 while () {
126 # by overwriting the state object with the manager we destroy it 165 (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) { 166 while @destroy;
132 my $coro = pop @destroy;
133 $coro->{status} ||= [];
134 $_->ready for @{delete $coro->{join} || []};
135 167
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} = $manager->{_coro_state};
141 }
142 &schedule; 168 &schedule;
143 } 169 }
144}; 170};
145 171
172$manager->prio (PRIO_MAX);
173
146# static methods. not really. 174# static methods. not really.
147 175
148=back 176=back
149 177
150=head2 STATIC METHODS 178=head2 STATIC METHODS
151 179
152Static methods are actually functions that operate on the current process only. 180Static methods are actually functions that operate on the current coroutine only.
153 181
154=over 4 182=over 4
155 183
156=item async { ... } [@args...] 184=item async { ... } [@args...]
157 185
158Create a new asynchronous process and return it's process object 186Create a new asynchronous coroutine and return it's coroutine object
159(usually unused). When the sub returns the new process is automatically 187(usually unused). When the sub returns the new coroutine is automatically
160terminated. 188terminated.
189
190Calling C<exit> in a coroutine will not work correctly, so do not do that.
191
192When the coroutine dies, the program will exit, just as in the main
193program.
161 194
162 # create a new coroutine that just prints its arguments 195 # create a new coroutine that just prints its arguments
163 async { 196 async {
164 print "@_\n"; 197 print "@_\n";
165 } 1,2,3,4; 198 } 1,2,3,4;
166 199
167=cut 200=cut
168 201
169sub async(&@) { 202sub async(&@) {
170 my $pid = new Coro @_; 203 my $coro = new Coro @_;
171 $manager->ready; # this ensures that the stack is cloned from the manager
172 $pid->ready; 204 $coro->ready;
173 $pid; 205 $coro
206}
207
208=item async_pool { ... } [@args...]
209
210Similar to C<async>, but uses a coroutine pool, so you should not call
211terminate or join (although you are allowed to), and you get a coroutine
212that might have executed other code already (which can be good or bad :).
213
214Also, the block is executed in an C<eval> context and a warning will be
215issued in case of an exception instead of terminating the program, as
216C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
217will not work in the expected way, unless you call terminate or cancel,
218which somehow defeats the purpose of pooling.
219
220The priority will be reset to C<0> after each job, otherwise the coroutine
221will be re-used "as-is".
222
223The pool size is limited to 8 idle coroutines (this can be adjusted by
224changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
225required.
226
227If you are concerned about pooled coroutines growing a lot because a
228single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {
229terminate }> once per second or so to slowly replenish the pool.
230
231=cut
232
233our $POOL_SIZE = 8;
234our @pool;
235
236sub pool_handler {
237 while () {
238 my ($cb, @arg) = @{ delete $current->{_invoke} };
239
240 eval {
241 $cb->(@arg);
242 };
243 warn $@ if $@;
244
245 last if @pool >= $POOL_SIZE;
246 push @pool, $current;
247
248 $current->prio (0);
249 schedule;
250 }
251}
252
253sub async_pool(&@) {
254 # this is also inlined into the unlock_scheduler
255 my $coro = (pop @pool or new Coro \&pool_handler);
256
257 $coro->{_invoke} = [@_];
258 $coro->ready;
259
260 $coro
174} 261}
175 262
176=item schedule 263=item schedule
177 264
178Calls the scheduler. Please note that the current process will not be put 265Calls the scheduler. Please note that the current coroutine will not be put
179into the ready queue, so calling this function usually means you will 266into the ready queue, so calling this function usually means you will
180never be called again. 267never be called again unless something else (e.g. an event handler) calls
268ready.
181 269
182=cut 270The canonical way to wait on external events is this:
271
272 {
273 # remember current coroutine
274 my $current = $Coro::current;
275
276 # register a hypothetical event handler
277 on_event_invoke sub {
278 # wake up sleeping coroutine
279 $current->ready;
280 undef $current;
281 };
282
283 # call schedule until event occured.
284 # in case we are woken up for other reasons
285 # (current still defined), loop.
286 Coro::schedule while $current;
287 }
183 288
184=item cede 289=item cede
185 290
186"Cede" to other processes. This function puts the current process into the 291"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 292ready queue and calls C<schedule>, which has the effect of giving up the
188current "timeslice" to other coroutines of the same or higher priority. 293current "timeslice" to other coroutines of the same or higher priority.
189 294
190=cut 295Returns true if at least one coroutine switch has happened.
296
297=item Coro::cede_notself
298
299Works like cede, but is not exported by default and will cede to any
300coroutine, regardless of priority, once.
301
302Returns true if at least one coroutine switch has happened.
191 303
192=item terminate [arg...] 304=item terminate [arg...]
193 305
194Terminates the current process with the given status values (see L<cancel>). 306Terminates the current coroutine with the given status values (see L<cancel>).
195 307
196=cut 308=cut
197 309
198sub terminate { 310sub terminate {
199 $current->cancel (@_); 311 $current->cancel (@_);
201 313
202=back 314=back
203 315
204# dynamic methods 316# dynamic methods
205 317
206=head2 PROCESS METHODS 318=head2 COROUTINE METHODS
207 319
208These are the methods you can call on process objects. 320These are the methods you can call on coroutine objects.
209 321
210=over 4 322=over 4
211 323
212=item new Coro \&sub [, @args...] 324=item new Coro \&sub [, @args...]
213 325
214Create a new process and return it. When the sub returns the process 326Create a new coroutine and return it. When the sub returns the coroutine
215automatically terminates as if C<terminate> with the returned values were 327automatically 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 328called. To make the coroutine run you must first put it into the ready queue
217by calling the ready method. 329by calling the ready method.
218 330
219=cut 331Calling C<exit> in a coroutine will not work correctly, so do not do that.
220 332
333=cut
334
221sub _newcoro { 335sub _run_coro {
222 terminate &{+shift}; 336 terminate &{+shift};
223} 337}
224 338
225sub new { 339sub new {
226 my $class = shift; 340 my $class = shift;
227 bless {
228 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
229 }, $class;
230}
231 341
232=item $process->ready 342 $class->SUPER::new (\&_run_coro, @_)
343}
233 344
234Put the given process into the ready queue. 345=item $success = $coroutine->ready
235 346
236=cut 347Put the given coroutine into the ready queue (according to it's priority)
348and return true. If the coroutine is already in the ready queue, do nothing
349and return false.
237 350
351=item $is_ready = $coroutine->is_ready
352
353Return wether the coroutine is currently the ready queue or not,
354
238=item $process->cancel (arg...) 355=item $coroutine->cancel (arg...)
239 356
240Temrinates the given process and makes it return the given arguments as 357Terminates the given coroutine and makes it return the given arguments as
241status (default: the empty list). 358status (default: the empty list). Never returns if the coroutine is the
359current coroutine.
242 360
243=cut 361=cut
244 362
245sub cancel { 363sub cancel {
246 my $self = shift; 364 my $self = shift;
247 $self->{status} = [@_]; 365 $self->{status} = [@_];
366
367 if ($current == $self) {
248 push @destroy, $self; 368 push @destroy, $self;
249 $manager->ready; 369 $manager->ready;
250 &schedule if $current == $self; 370 &schedule while 1;
371 } else {
372 $self->_cancel;
373 }
251} 374}
252 375
253=item $process->join 376=item $coroutine->join
254 377
255Wait until the coroutine terminates and return any values given to the 378Wait until the coroutine terminates and return any values given to the
256C<terminate> or C<cancel> functions. C<join> can be called multiple times 379C<terminate> or C<cancel> functions. C<join> can be called multiple times
257from multiple processes. 380from multiple coroutine.
258 381
259=cut 382=cut
260 383
261sub join { 384sub join {
262 my $self = shift; 385 my $self = shift;
386
263 unless ($self->{status}) { 387 unless ($self->{status}) {
264 push @{$self->{join}}, $current; 388 my $current = $current;
265 &schedule; 389
390 push @{$self->{destroy_cb}}, sub {
391 $current->ready;
392 undef $current;
393 };
394
395 &schedule while $current;
266 } 396 }
397
267 wantarray ? @{$self->{status}} : $self->{status}[0]; 398 wantarray ? @{$self->{status}} : $self->{status}[0];
268} 399}
269 400
401=item $coroutine->on_destroy (\&cb)
402
403Registers a callback that is called when this coroutine gets destroyed,
404but before it is joined. The callback gets passed the terminate arguments,
405if any.
406
407=cut
408
409sub on_destroy {
410 my ($self, $cb) = @_;
411
412 push @{ $self->{destroy_cb} }, $cb;
413}
414
270=item $oldprio = $process->prio($newprio) 415=item $oldprio = $coroutine->prio ($newprio)
271 416
272Sets (or gets, if the argument is missing) the priority of the 417Sets (or gets, if the argument is missing) the priority of the
273process. Higher priority processes get run before lower priority 418coroutine. Higher priority coroutines get run before lower priority
274processes. Priorities are small signed integers (currently -4 .. +3), 419coroutines. Priorities are small signed integers (currently -4 .. +3),
275that you can refer to using PRIO_xxx constants (use the import tag :prio 420that you can refer to using PRIO_xxx constants (use the import tag :prio
276to get then): 421to get then):
277 422
278 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 423 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
279 3 > 1 > 0 > -1 > -3 > -4 424 3 > 1 > 0 > -1 > -3 > -4
282 current->prio(PRIO_HIGH); 427 current->prio(PRIO_HIGH);
283 428
284The idle coroutine ($Coro::idle) always has a lower priority than any 429The idle coroutine ($Coro::idle) always has a lower priority than any
285existing coroutine. 430existing coroutine.
286 431
287Changing the priority of the current process will take effect immediately, 432Changing the priority of the current coroutine will take effect immediately,
288but changing the priority of processes in the ready queue (but not 433but changing the priority of coroutines in the ready queue (but not
289running) will only take effect after the next schedule (of that 434running) will only take effect after the next schedule (of that
290process). This is a bug that will be fixed in some future version. 435coroutine). This is a bug that will be fixed in some future version.
291 436
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) 437=item $newprio = $coroutine->nice ($change)
301 438
302Similar to C<prio>, but subtract the given value from the priority (i.e. 439Similar to C<prio>, but subtract the given value from the priority (i.e.
303higher values mean lower priority, just as in unix). 440higher values mean lower priority, just as in unix).
304 441
305=cut
306
307sub nice {
308 $_[0]{prio} -= $_[1];
309}
310
311=item $olddesc = $process->desc($newdesc) 442=item $olddesc = $coroutine->desc ($newdesc)
312 443
313Sets (or gets in case the argument is missing) the description for this 444Sets (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. 445coroutine. This is just a free-form string you can associate with a coroutine.
315 446
316=cut 447=cut
317 448
318sub desc { 449sub desc {
319 my $old = $_[0]{desc}; 450 my $old = $_[0]{desc};
321 $old; 452 $old;
322} 453}
323 454
324=back 455=back
325 456
457=head2 GLOBAL FUNCTIONS
458
459=over 4
460
461=item Coro::nready
462
463Returns the number of coroutines that are currently in the ready state,
464i.e. that can be swicthed to. The value C<0> means that the only runnable
465coroutine is the currently running one, so C<cede> would have no effect,
466and C<schedule> would cause a deadlock unless there is an idle handler
467that wakes up some coroutines.
468
469=item my $guard = Coro::guard { ... }
470
471This creates and returns a guard object. Nothing happens until the objetc
472gets destroyed, in which case the codeblock given as argument will be
473executed. This is useful to free locks or other resources in case of a
474runtime error or when the coroutine gets canceled, as in both cases the
475guard block will be executed. The guard object supports only one method,
476C<< ->cancel >>, which will keep the codeblock from being executed.
477
478Example: set some flag and clear it again when the coroutine gets canceled
479or the function returns:
480
481 sub do_something {
482 my $guard = Coro::guard { $busy = 0 };
483 $busy = 1;
484
485 # do something that requires $busy to be true
486 }
487
488=cut
489
490sub guard(&) {
491 bless \(my $cb = $_[0]), "Coro::guard"
492}
493
494sub Coro::guard::cancel {
495 ${$_[0]} = sub { };
496}
497
498sub Coro::guard::DESTROY {
499 ${$_[0]}->();
500}
501
502
503=item unblock_sub { ... }
504
505This utility function takes a BLOCK or code reference and "unblocks" it,
506returning the new coderef. This means that the new coderef will return
507immediately without blocking, returning nothing, while the original code
508ref will be called (with parameters) from within its own coroutine.
509
510The reason this fucntion exists is that many event libraries (such as the
511venerable L<Event|Event> module) are not coroutine-safe (a weaker form
512of thread-safety). This means you must not block within event callbacks,
513otherwise you might suffer from crashes or worse.
514
515This function allows your callbacks to block by executing them in another
516coroutine where it is safe to block. One example where blocking is handy
517is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
518disk.
519
520In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
521creating event callbacks that want to block.
522
523=cut
524
525our @unblock_queue;
526
527# we create a special coro because we want to cede,
528# to reduce pressure on the coro pool (because most callbacks
529# return immediately and can be reused) and because we cannot cede
530# inside an event callback.
531our $unblock_scheduler = async {
532 while () {
533 while (my $cb = pop @unblock_queue) {
534 # this is an inlined copy of async_pool
535 my $coro = (pop @pool or new Coro \&pool_handler);
536
537 $coro->{_invoke} = $cb;
538 $coro->ready;
539 cede; # for short-lived callbacks, this reduces pressure on the coro pool
540 }
541 schedule; # sleep well
542 }
543};
544
545sub unblock_sub(&) {
546 my $cb = shift;
547
548 sub {
549 unshift @unblock_queue, [$cb, @_];
550 $unblock_scheduler->ready;
551 }
552}
553
554=back
555
326=cut 556=cut
327 557
3281; 5581;
329 559
330=head1 BUGS/LIMITATIONS 560=head1 BUGS/LIMITATIONS
337 to allow per-thread schedulers, but Coro::State does not yet allow 567 to allow per-thread schedulers, but Coro::State does not yet allow
338 this). 568 this).
339 569
340=head1 SEE ALSO 570=head1 SEE ALSO
341 571
342L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 572Support/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>, 573
344L<Coro::Handle>, L<Coro::RWLock>, L<Coro::Socket>. 574Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
575
576Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
577
578Embedding: L<Coro:MakeMaker>
345 579
346=head1 AUTHOR 580=head1 AUTHOR
347 581
348 Marc Lehmann <pcg@goof.com> 582 Marc Lehmann <schmorp@schmorp.de>
349 http://home.schmorp.de/ 583 http://home.schmorp.de/
350 584
351=cut 585=cut
352 586

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