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Revision 1.140 by root, Thu Sep 27 16:25:10 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}
117 159
118# this coroutine is necessary because a coroutine 160# this coroutine is necessary because a coroutine
119# cannot destroy itself. 161# cannot destroy itself.
120my @destroy; 162my @destroy;
121my $manager; 163my $manager;
164
122$manager = new Coro sub { 165$manager = new Coro sub {
123 while() { 166 while () {
124 # by overwriting the state object with the manager we destroy it 167 (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) { 168 while @destroy;
130 my $coro = pop @destroy; 169
131 $coro->{status} ||= [];
132 $_->ready for @{delete $coro->{join} || []};
133 $coro->{_coro_state} = $manager->{_coro_state};
134 }
135 &schedule; 170 &schedule;
136 } 171 }
137}; 172};
173$manager->desc ("[coro manager]");
174$manager->prio (PRIO_MAX);
138 175
139# static methods. not really. 176# static methods. not really.
140 177
141=back 178=back
142 179
143=head2 STATIC METHODS 180=head2 STATIC METHODS
144 181
145Static methods are actually functions that operate on the current process only. 182Static methods are actually functions that operate on the current coroutine only.
146 183
147=over 4 184=over 4
148 185
149=item async { ... } [@args...] 186=item async { ... } [@args...]
150 187
151Create a new asynchronous process and return it's process object 188Create a new asynchronous coroutine and return it's coroutine object
152(usually unused). When the sub returns the new process is automatically 189(usually unused). When the sub returns the new coroutine is automatically
153terminated. 190terminated.
191
192Calling C<exit> in a coroutine will do the same as calling exit outside
193the coroutine. Likewise, when the coroutine dies, the program will exit,
194just as it would in the main program.
154 195
155 # create a new coroutine that just prints its arguments 196 # create a new coroutine that just prints its arguments
156 async { 197 async {
157 print "@_\n"; 198 print "@_\n";
158 } 1,2,3,4; 199 } 1,2,3,4;
159 200
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 201=cut
164 202
165sub async(&@) { 203sub async(&@) {
166 my $pid = new Coro @_; 204 my $coro = new Coro @_;
167 $manager->ready; # this ensures that the stack is cloned from the manager
168 $pid->ready; 205 $coro->ready;
169 $pid; 206 $coro
207}
208
209=item async_pool { ... } [@args...]
210
211Similar to C<async>, but uses a coroutine pool, so you should not call
212terminate or join (although you are allowed to), and you get a coroutine
213that might have executed other code already (which can be good or bad :).
214
215Also, the block is executed in an C<eval> context and a warning will be
216issued in case of an exception instead of terminating the program, as
217C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
218will not work in the expected way, unless you call terminate or cancel,
219which somehow defeats the purpose of pooling.
220
221The priority will be reset to C<0> after each job, otherwise the coroutine
222will be re-used "as-is".
223
224The pool size is limited to 8 idle coroutines (this can be adjusted by
225changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
226required.
227
228If you are concerned about pooled coroutines growing a lot because a
229single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
230{ terminate }> once per second or so to slowly replenish the pool. In
231addition to that, when the stacks used by a handler grows larger than 16kb
232(adjustable with $Coro::POOL_RSS) it will also exit.
233
234=cut
235
236our $POOL_SIZE = 8;
237our $POOL_RSS = 16 * 1024;
238our @async_pool;
239
240sub pool_handler {
241 my $cb;
242
243 while () {
244 eval {
245 while () {
246 _pool_1 $cb;
247 &$cb;
248 _pool_2 $cb;
249 &schedule;
250 }
251 };
252
253 last if $@ eq "\3terminate\2\n";
254 warn $@ if $@;
255 }
256}
257
258sub async_pool(&@) {
259 # this is also inlined into the unlock_scheduler
260 my $coro = (pop @async_pool) || new Coro \&pool_handler;
261
262 $coro->{_invoke} = [@_];
263 $coro->ready;
264
265 $coro
170} 266}
171 267
172=item schedule 268=item schedule
173 269
174Calls the scheduler. Please note that the current process will not be put 270Calls the scheduler. Please note that the current coroutine will not be put
175into the ready queue, so calling this function usually means you will 271into the ready queue, so calling this function usually means you will
176never be called again. 272never be called again unless something else (e.g. an event handler) calls
273ready.
177 274
178=cut 275The canonical way to wait on external events is this:
276
277 {
278 # remember current coroutine
279 my $current = $Coro::current;
280
281 # register a hypothetical event handler
282 on_event_invoke sub {
283 # wake up sleeping coroutine
284 $current->ready;
285 undef $current;
286 };
287
288 # call schedule until event occurred.
289 # in case we are woken up for other reasons
290 # (current still defined), loop.
291 Coro::schedule while $current;
292 }
179 293
180=item cede 294=item cede
181 295
182"Cede" to other processes. This function puts the current process into the 296"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 297ready queue and calls C<schedule>, which has the effect of giving up the
184current "timeslice" to other coroutines of the same or higher priority. 298current "timeslice" to other coroutines of the same or higher priority.
185 299
186=cut 300Returns true if at least one coroutine switch has happened.
301
302=item Coro::cede_notself
303
304Works like cede, but is not exported by default and will cede to any
305coroutine, regardless of priority, once.
306
307Returns true if at least one coroutine switch has happened.
187 308
188=item terminate [arg...] 309=item terminate [arg...]
189 310
190Terminates the current process. 311Terminates the current coroutine with the given status values (see L<cancel>).
191
192Future versions of this function will allow result arguments.
193 312
194=cut 313=cut
195 314
196sub terminate { 315sub terminate {
197 $current->{status} = [@_];
198 $current->cancel; 316 $current->cancel (@_);
199 &schedule;
200 die; # NORETURN
201} 317}
202 318
203=back 319=back
204 320
205# dynamic methods 321# dynamic methods
206 322
207=head2 PROCESS METHODS 323=head2 COROUTINE METHODS
208 324
209These are the methods you can call on process objects. 325These are the methods you can call on coroutine objects.
210 326
211=over 4 327=over 4
212 328
213=item new Coro \&sub [, @args...] 329=item new Coro \&sub [, @args...]
214 330
215Create a new process and return it. When the sub returns the process 331Create a new coroutine and return it. When the sub returns the coroutine
216automatically terminates as if C<terminate> with the returned values were 332automatically 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 333called. To make the coroutine run you must first put it into the ready queue
218by calling the ready method. 334by calling the ready method.
219 335
220=cut 336See C<async> for additional discussion.
221 337
338=cut
339
222sub _newcoro { 340sub _run_coro {
223 terminate &{+shift}; 341 terminate &{+shift};
224} 342}
225 343
226sub new { 344sub new {
227 my $class = shift; 345 my $class = shift;
228 bless {
229 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
230 }, $class;
231}
232 346
233=item $process->ready 347 $class->SUPER::new (\&_run_coro, @_)
348}
234 349
235Put the given process into the ready queue. 350=item $success = $coroutine->ready
236 351
237=cut 352Put the given coroutine into the ready queue (according to it's priority)
353and return true. If the coroutine is already in the ready queue, do nothing
354and return false.
238 355
239=item $process->cancel 356=item $is_ready = $coroutine->is_ready
240 357
241Like C<terminate>, but terminates the specified process instead. 358Return wether the coroutine is currently the ready queue or not,
359
360=item $coroutine->cancel (arg...)
361
362Terminates the given coroutine and makes it return the given arguments as
363status (default: the empty list). Never returns if the coroutine is the
364current coroutine.
242 365
243=cut 366=cut
244 367
245sub cancel { 368sub cancel {
369 my $self = shift;
370 $self->{status} = [@_];
371
372 if ($current == $self) {
246 push @destroy, $_[0]; 373 push @destroy, $self;
247 $manager->ready; 374 $manager->ready;
248 &schedule if $current == $_[0]; 375 &schedule while 1;
376 } else {
377 $self->_cancel;
378 }
249} 379}
250 380
251=item $process->join 381=item $coroutine->join
252 382
253Wait until the coroutine terminates and return any values given to the 383Wait until the coroutine terminates and return any values given to the
254C<terminate> function. C<join> can be called multiple times from multiple 384C<terminate> or C<cancel> functions. C<join> can be called multiple times
255processes. 385from multiple coroutine.
256 386
257=cut 387=cut
258 388
259sub join { 389sub join {
260 my $self = shift; 390 my $self = shift;
391
261 unless ($self->{status}) { 392 unless ($self->{status}) {
262 push @{$self->{join}}, $current; 393 my $current = $current;
263 &schedule; 394
395 push @{$self->{destroy_cb}}, sub {
396 $current->ready;
397 undef $current;
398 };
399
400 &schedule while $current;
264 } 401 }
402
265 wantarray ? @{$self->{status}} : $self->{status}[0]; 403 wantarray ? @{$self->{status}} : $self->{status}[0];
266} 404}
267 405
406=item $coroutine->on_destroy (\&cb)
407
408Registers a callback that is called when this coroutine gets destroyed,
409but before it is joined. The callback gets passed the terminate arguments,
410if any.
411
412=cut
413
414sub on_destroy {
415 my ($self, $cb) = @_;
416
417 push @{ $self->{destroy_cb} }, $cb;
418}
419
268=item $oldprio = $process->prio($newprio) 420=item $oldprio = $coroutine->prio ($newprio)
269 421
270Sets (or gets, if the argument is missing) the priority of the 422Sets (or gets, if the argument is missing) the priority of the
271process. Higher priority processes get run before lower priority 423coroutine. Higher priority coroutines get run before lower priority
272processes. Priorities are small signed integers (currently -4 .. +3), 424coroutines. Priorities are small signed integers (currently -4 .. +3),
273that you can refer to using PRIO_xxx constants (use the import tag :prio 425that you can refer to using PRIO_xxx constants (use the import tag :prio
274to get then): 426to get then):
275 427
276 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 428 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
277 3 > 1 > 0 > -1 > -3 > -4 429 3 > 1 > 0 > -1 > -3 > -4
280 current->prio(PRIO_HIGH); 432 current->prio(PRIO_HIGH);
281 433
282The idle coroutine ($Coro::idle) always has a lower priority than any 434The idle coroutine ($Coro::idle) always has a lower priority than any
283existing coroutine. 435existing coroutine.
284 436
285Changing the priority of the current process will take effect immediately, 437Changing the priority of the current coroutine will take effect immediately,
286but changing the priority of processes in the ready queue (but not 438but changing the priority of coroutines in the ready queue (but not
287running) will only take effect after the next schedule (of that 439running) will only take effect after the next schedule (of that
288process). This is a bug that will be fixed in some future version. 440coroutine). This is a bug that will be fixed in some future version.
289 441
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) 442=item $newprio = $coroutine->nice ($change)
299 443
300Similar to C<prio>, but subtract the given value from the priority (i.e. 444Similar to C<prio>, but subtract the given value from the priority (i.e.
301higher values mean lower priority, just as in unix). 445higher values mean lower priority, just as in unix).
302 446
303=cut
304
305sub nice {
306 $_[0]{prio} -= $_[1];
307}
308
309=item $olddesc = $process->desc($newdesc) 447=item $olddesc = $coroutine->desc ($newdesc)
310 448
311Sets (or gets in case the argument is missing) the description for this 449Sets (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. 450coroutine. This is just a free-form string you can associate with a coroutine.
313 451
314=cut 452=cut
315 453
316sub desc { 454sub desc {
317 my $old = $_[0]{desc}; 455 my $old = $_[0]{desc};
319 $old; 457 $old;
320} 458}
321 459
322=back 460=back
323 461
462=head2 GLOBAL FUNCTIONS
463
464=over 4
465
466=item Coro::nready
467
468Returns the number of coroutines that are currently in the ready state,
469i.e. that can be switched to. The value C<0> means that the only runnable
470coroutine is the currently running one, so C<cede> would have no effect,
471and C<schedule> would cause a deadlock unless there is an idle handler
472that wakes up some coroutines.
473
474=item my $guard = Coro::guard { ... }
475
476This creates and returns a guard object. Nothing happens until the object
477gets destroyed, in which case the codeblock given as argument will be
478executed. This is useful to free locks or other resources in case of a
479runtime error or when the coroutine gets canceled, as in both cases the
480guard block will be executed. The guard object supports only one method,
481C<< ->cancel >>, which will keep the codeblock from being executed.
482
483Example: set some flag and clear it again when the coroutine gets canceled
484or the function returns:
485
486 sub do_something {
487 my $guard = Coro::guard { $busy = 0 };
488 $busy = 1;
489
490 # do something that requires $busy to be true
491 }
492
493=cut
494
495sub guard(&) {
496 bless \(my $cb = $_[0]), "Coro::guard"
497}
498
499sub Coro::guard::cancel {
500 ${$_[0]} = sub { };
501}
502
503sub Coro::guard::DESTROY {
504 ${$_[0]}->();
505}
506
507
508=item unblock_sub { ... }
509
510This utility function takes a BLOCK or code reference and "unblocks" it,
511returning the new coderef. This means that the new coderef will return
512immediately without blocking, returning nothing, while the original code
513ref will be called (with parameters) from within its own coroutine.
514
515The reason this function exists is that many event libraries (such as the
516venerable L<Event|Event> module) are not coroutine-safe (a weaker form
517of thread-safety). This means you must not block within event callbacks,
518otherwise you might suffer from crashes or worse.
519
520This function allows your callbacks to block by executing them in another
521coroutine where it is safe to block. One example where blocking is handy
522is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
523disk.
524
525In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
526creating event callbacks that want to block.
527
528=cut
529
530our @unblock_queue;
531
532# we create a special coro because we want to cede,
533# to reduce pressure on the coro pool (because most callbacks
534# return immediately and can be reused) and because we cannot cede
535# inside an event callback.
536our $unblock_scheduler = new Coro sub {
537 while () {
538 while (my $cb = pop @unblock_queue) {
539 # this is an inlined copy of async_pool
540 my $coro = (pop @async_pool) || new Coro \&pool_handler;
541
542 $coro->{_invoke} = $cb;
543 $coro->ready;
544 cede; # for short-lived callbacks, this reduces pressure on the coro pool
545 }
546 schedule; # sleep well
547 }
548};
549$unblock_scheduler->desc ("[unblock_sub scheduler]");
550
551sub unblock_sub(&) {
552 my $cb = shift;
553
554 sub {
555 unshift @unblock_queue, [$cb, @_];
556 $unblock_scheduler->ready;
557 }
558}
559
560=back
561
324=cut 562=cut
325 563
3261; 5641;
327 565
328=head1 BUGS/LIMITATIONS 566=head1 BUGS/LIMITATIONS
329 567
330 - you must make very sure that no coro is still active on global 568 - you must make very sure that no coro is still active on global
331 destruction. very bad things might happen otherwise (usually segfaults). 569 destruction. very bad things might happen otherwise (usually segfaults).
332 570
333 - this module is not thread-safe. You should only ever use this module 571 - 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 572 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 573 to allow per-thread schedulers, but Coro::State does not yet allow
336 this). 574 this).
337 575
338=head1 SEE ALSO 576=head1 SEE ALSO
339 577
340L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 578Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
341L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>, 579
342L<Coro::Handle>, L<Coro::Socket>. 580Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
581
582Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
583
584Embedding: L<Coro:MakeMaker>
343 585
344=head1 AUTHOR 586=head1 AUTHOR
345 587
346 Marc Lehmann <pcg@goof.com> 588 Marc Lehmann <schmorp@schmorp.de>
347 http://www.goof.com/pcg/marc/ 589 http://home.schmorp.de/
348 590
349=cut 591=cut
350 592

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