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Revision 1.129 by root, Wed Sep 19 22:33:08 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
26This module is still experimental, see the BUGS section below. 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).
27 34
28In this module, coroutines are defined as "callchain + lexical variables 35In this module, coroutines are defined as "callchain + lexical variables +
29+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own 36@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
30callchain, it's own set of lexicals and it's own set of perl's most 37its own set of lexicals and its own set of perls most important global
31important global variables. 38variables.
32 39
33=cut 40=cut
34 41
35package Coro; 42package Coro;
36 43
44use strict;
37no warnings qw(uninitialized); 45no warnings "uninitialized";
38 46
39use Coro::State; 47use Coro::State;
40 48
41use base Exporter; 49use base qw(Coro::State Exporter);
42 50
43$VERSION = 0.5; 51our $idle; # idle handler
52our $main; # main coroutine
53our $current; # current coroutine
44 54
55our $VERSION = '3.7';
56
45@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
46%EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
47 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48); 60);
49@EXPORT_OK = @{$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 (@_) {
77 }; 92 };
78 } 93 }
79 94
80} 95}
81 96
97=over 4
98
82=item $main 99=item $main
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<$main> (of course).
111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essential you are encouraged to use the
114C<Coro::current> function instead.
93 115
94=cut 116=cut
95 117
96# maybe some other module used Coro::Specific before... 118# maybe some other module used Coro::Specific before...
97if ($current) {
98 $main->{specific} = $current->{specific}; 119$main->{specific} = $current->{specific}
99} 120 if $current;
100 121
101our $current = $main; 122_set_current $main;
102 123
103sub current() { $current } 124sub current() { $current }
104 125
105=item $idle 126=item $idle
106 127
107The coroutine to switch to when no other coroutine is running. The default 128A callback that is called whenever the scheduler finds no ready coroutines
108implementation 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.
109 131
110=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.
111 135
112# should be done using priorities :( 136Please note that if your callback recursively invokes perl (e.g. for event
113our $idle = new Coro sub { 137handlers), then it must be prepared to be called recursively.
114 print STDERR "FATAL: deadlock detected\n"; 138
115 exit(51); 139=cut
140
141$idle = sub {
142 require Carp;
143 Carp::croak ("FATAL: deadlock detected");
116}; 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}
117 157
118# this coroutine is necessary because a coroutine 158# this coroutine is necessary because a coroutine
119# cannot destroy itself. 159# cannot destroy itself.
120my @destroy; 160my @destroy;
161my $manager;
162
121my $manager = new Coro sub { 163$manager = new Coro sub {
164 $current->desc ("[coro manager]");
165
122 while() { 166 while () {
123 delete ((pop @destroy)->{_coro_state}) while @destroy; 167 (shift @destroy)->_cancel
168 while @destroy;
169
124 &schedule; 170 &schedule;
125 } 171 }
126}; 172};
127 173
174$manager->prio (PRIO_MAX);
175
128# static methods. not really. 176# static methods. not really.
129 177
178=back
179
130=head2 STATIC METHODS 180=head2 STATIC METHODS
131 181
132Static methods are actually functions that operate on the current process only. 182Static methods are actually functions that operate on the current coroutine only.
133 183
134=over 4 184=over 4
135 185
136=item async { ... } [@args...] 186=item async { ... } [@args...]
137 187
138Create a new asynchronous process and return it's process object 188Create a new asynchronous coroutine and return it's coroutine object
139(usually unused). When the sub returns the new process is automatically 189(usually unused). When the sub returns the new coroutine is automatically
140terminated. 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.
141 195
142 # create a new coroutine that just prints its arguments 196 # create a new coroutine that just prints its arguments
143 async { 197 async {
144 print "@_\n"; 198 print "@_\n";
145 } 1,2,3,4; 199 } 1,2,3,4;
146 200
147The coderef you submit MUST NOT be a closure that refers to variables
148in an outer scope. This does NOT work. Pass arguments into it instead.
149
150=cut 201=cut
151 202
152sub async(&@) { 203sub async(&@) {
153 my $pid = new Coro @_; 204 my $coro = new Coro @_;
154 $manager->ready; # this ensures that the stack is cloned from the manager
155 $pid->ready; 205 $coro->ready;
156 $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 {
230terminate }> once per second or so to slowly replenish the pool.
231
232=cut
233
234our $POOL_SIZE = 8;
235our @pool;
236
237sub pool_handler {
238 while () {
239 $current->{desc} = "[async_pool]";
240
241 eval {
242 my ($cb, @arg) = @{ delete $current->{_invoke} or return };
243 $cb->(@arg);
244 };
245 warn $@ if $@;
246
247 last if @pool >= $POOL_SIZE;
248
249 push @pool, $current;
250 $current->{desc} = "[async_pool idle]";
251 $current->save (Coro::State::SAVE_DEF);
252 $current->prio (0);
253 schedule;
254 }
255}
256
257sub async_pool(&@) {
258 # this is also inlined into the unlock_scheduler
259 my $coro = (pop @pool) || new Coro \&pool_handler;;
260
261 $coro->{_invoke} = [@_];
262 $coro->ready;
263
264 $coro
157} 265}
158 266
159=item schedule 267=item schedule
160 268
161Calls the scheduler. Please note that the current process will not be put 269Calls the scheduler. Please note that the current coroutine will not be put
162into the ready queue, so calling this function usually means you will 270into the ready queue, so calling this function usually means you will
163never be called again. 271never be called again unless something else (e.g. an event handler) calls
272ready.
164 273
165=cut 274The canonical way to wait on external events is this:
275
276 {
277 # remember current coroutine
278 my $current = $Coro::current;
279
280 # register a hypothetical event handler
281 on_event_invoke sub {
282 # wake up sleeping coroutine
283 $current->ready;
284 undef $current;
285 };
286
287 # call schedule until event occurred.
288 # in case we are woken up for other reasons
289 # (current still defined), loop.
290 Coro::schedule while $current;
291 }
166 292
167=item cede 293=item cede
168 294
169"Cede" to other processes. This function puts the current process into the 295"Cede" to other coroutines. This function puts the current coroutine into the
170ready queue and calls C<schedule>, which has the effect of giving up the 296ready queue and calls C<schedule>, which has the effect of giving up the
171current "timeslice" to other coroutines of the same or higher priority. 297current "timeslice" to other coroutines of the same or higher priority.
172 298
173=cut 299Returns true if at least one coroutine switch has happened.
174 300
301=item Coro::cede_notself
302
303Works like cede, but is not exported by default and will cede to any
304coroutine, regardless of priority, once.
305
306Returns true if at least one coroutine switch has happened.
307
175=item terminate 308=item terminate [arg...]
176 309
177Terminates the current process. 310Terminates the current coroutine with the given status values (see L<cancel>).
178
179Future versions of this function will allow result arguments.
180 311
181=cut 312=cut
182 313
183sub terminate { 314sub terminate {
184 $current->cancel; 315 $current->cancel (@_);
185 &schedule;
186 die; # NORETURN
187} 316}
188 317
189=back 318=back
190 319
191# dynamic methods 320# dynamic methods
192 321
193=head2 PROCESS METHODS 322=head2 COROUTINE METHODS
194 323
195These are the methods you can call on process objects. 324These are the methods you can call on coroutine objects.
196 325
197=over 4 326=over 4
198 327
199=item new Coro \&sub [, @args...] 328=item new Coro \&sub [, @args...]
200 329
201Create a new process and return it. When the sub returns the process 330Create a new coroutine and return it. When the sub returns the coroutine
202automatically terminates. To start the process you must first put it into 331automatically terminates as if C<terminate> with the returned values were
332called. To make the coroutine run you must first put it into the ready queue
203the ready queue by calling the ready method. 333by calling the ready method.
204 334
205The coderef you submit MUST NOT be a closure that refers to variables 335See C<async> for additional discussion.
206in an outer scope. This does NOT work. Pass arguments into it instead.
207 336
208=cut 337=cut
209 338
210sub _newcoro { 339sub _run_coro {
211 terminate &{+shift}; 340 terminate &{+shift};
212} 341}
213 342
214sub new { 343sub new {
215 my $class = shift; 344 my $class = shift;
216 bless {
217 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
218 }, $class;
219}
220 345
221=item $process->ready 346 $class->SUPER::new (\&_run_coro, @_)
347}
222 348
223Put the current process into the ready queue. 349=item $success = $coroutine->ready
224 350
225=cut 351Put the given coroutine into the ready queue (according to it's priority)
352and return true. If the coroutine is already in the ready queue, do nothing
353and return false.
226 354
227=item $process->cancel 355=item $is_ready = $coroutine->is_ready
228 356
229Like C<terminate>, but terminates the specified process instead. 357Return wether the coroutine is currently the ready queue or not,
358
359=item $coroutine->cancel (arg...)
360
361Terminates the given coroutine and makes it return the given arguments as
362status (default: the empty list). Never returns if the coroutine is the
363current coroutine.
230 364
231=cut 365=cut
232 366
233sub cancel { 367sub cancel {
368 my $self = shift;
369 $self->{status} = [@_];
370
371 if ($current == $self) {
234 push @destroy, $_[0]; 372 push @destroy, $self;
235 $manager->ready; 373 $manager->ready;
236 &schedule if $current == $_[0]; 374 &schedule while 1;
375 } else {
376 $self->_cancel;
377 }
237} 378}
238 379
380=item $coroutine->join
381
382Wait until the coroutine terminates and return any values given to the
383C<terminate> or C<cancel> functions. C<join> can be called multiple times
384from multiple coroutine.
385
386=cut
387
388sub join {
389 my $self = shift;
390
391 unless ($self->{status}) {
392 my $current = $current;
393
394 push @{$self->{destroy_cb}}, sub {
395 $current->ready;
396 undef $current;
397 };
398
399 &schedule while $current;
400 }
401
402 wantarray ? @{$self->{status}} : $self->{status}[0];
403}
404
405=item $coroutine->on_destroy (\&cb)
406
407Registers a callback that is called when this coroutine gets destroyed,
408but before it is joined. The callback gets passed the terminate arguments,
409if any.
410
411=cut
412
413sub on_destroy {
414 my ($self, $cb) = @_;
415
416 push @{ $self->{destroy_cb} }, $cb;
417}
418
239=item $oldprio = $process->prio($newprio) 419=item $oldprio = $coroutine->prio ($newprio)
240 420
241Sets the priority of the process. Higher priority processes get run before 421Sets (or gets, if the argument is missing) the priority of the
242lower priority processes. Priorities are smalled signed integer (currently 422coroutine. Higher priority coroutines get run before lower priority
423coroutines. Priorities are small signed integers (currently -4 .. +3),
243-4 .. +3), that you can refer to using PRIO_xxx constants (use the import 424that you can refer to using PRIO_xxx constants (use the import tag :prio
244tag :prio to get then): 425to get then):
245 426
246 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 427 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
247 3 > 1 > 0 > -1 > -3 > -4 428 3 > 1 > 0 > -1 > -3 > -4
248 429
249 # set priority to HIGH 430 # set priority to HIGH
250 current->prio(PRIO_HIGH); 431 current->prio(PRIO_HIGH);
251 432
252The idle coroutine ($Coro::idle) always has a lower priority than any 433The idle coroutine ($Coro::idle) always has a lower priority than any
253existing coroutine. 434existing coroutine.
254 435
255Changing the priority of the current process will take effect immediately, 436Changing the priority of the current coroutine will take effect immediately,
256but changing the priority of processes in the ready queue (but not 437but changing the priority of coroutines in the ready queue (but not
257running) will only take effect after the next schedule (of that 438running) will only take effect after the next schedule (of that
258process). This is a bug that will be fixed in some future version. 439coroutine). This is a bug that will be fixed in some future version.
259 440
260=cut
261
262sub prio {
263 my $old = $_[0]{prio};
264 $_[0]{prio} = $_[1] if @_ > 1;
265 $old;
266}
267
268=item $newprio = $process->nice($change) 441=item $newprio = $coroutine->nice ($change)
269 442
270Similar to C<prio>, but subtract the given value from the priority (i.e. 443Similar to C<prio>, but subtract the given value from the priority (i.e.
271higher values mean lower priority, just as in unix). 444higher values mean lower priority, just as in unix).
272 445
273=cut 446=item $olddesc = $coroutine->desc ($newdesc)
274 447
275sub nice { 448Sets (or gets in case the argument is missing) the description for this
276 $_[0]{prio} -= $_[1]; 449coroutine. This is just a free-form string you can associate with a coroutine.
450
451=cut
452
453sub desc {
454 my $old = $_[0]{desc};
455 $_[0]{desc} = $_[1] if @_ > 1;
456 $old;
277} 457}
278 458
279=back 459=back
280 460
461=head2 GLOBAL FUNCTIONS
462
463=over 4
464
465=item Coro::nready
466
467Returns the number of coroutines that are currently in the ready state,
468i.e. that can be switched to. The value C<0> means that the only runnable
469coroutine is the currently running one, so C<cede> would have no effect,
470and C<schedule> would cause a deadlock unless there is an idle handler
471that wakes up some coroutines.
472
473=item my $guard = Coro::guard { ... }
474
475This creates and returns a guard object. Nothing happens until the object
476gets destroyed, in which case the codeblock given as argument will be
477executed. This is useful to free locks or other resources in case of a
478runtime error or when the coroutine gets canceled, as in both cases the
479guard block will be executed. The guard object supports only one method,
480C<< ->cancel >>, which will keep the codeblock from being executed.
481
482Example: set some flag and clear it again when the coroutine gets canceled
483or the function returns:
484
485 sub do_something {
486 my $guard = Coro::guard { $busy = 0 };
487 $busy = 1;
488
489 # do something that requires $busy to be true
490 }
491
492=cut
493
494sub guard(&) {
495 bless \(my $cb = $_[0]), "Coro::guard"
496}
497
498sub Coro::guard::cancel {
499 ${$_[0]} = sub { };
500}
501
502sub Coro::guard::DESTROY {
503 ${$_[0]}->();
504}
505
506
507=item unblock_sub { ... }
508
509This utility function takes a BLOCK or code reference and "unblocks" it,
510returning the new coderef. This means that the new coderef will return
511immediately without blocking, returning nothing, while the original code
512ref will be called (with parameters) from within its own coroutine.
513
514The reason this function exists is that many event libraries (such as the
515venerable L<Event|Event> module) are not coroutine-safe (a weaker form
516of thread-safety). This means you must not block within event callbacks,
517otherwise you might suffer from crashes or worse.
518
519This function allows your callbacks to block by executing them in another
520coroutine where it is safe to block. One example where blocking is handy
521is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
522disk.
523
524In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
525creating event callbacks that want to block.
526
527=cut
528
529our @unblock_queue;
530
531# we create a special coro because we want to cede,
532# to reduce pressure on the coro pool (because most callbacks
533# return immediately and can be reused) and because we cannot cede
534# inside an event callback.
535our $unblock_scheduler = async {
536 $current->desc ("[unblock_sub scheduler]");
537 while () {
538 while (my $cb = pop @unblock_queue) {
539 # this is an inlined copy of async_pool
540 my $coro = (pop @pool or 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
550sub unblock_sub(&) {
551 my $cb = shift;
552
553 sub {
554 unshift @unblock_queue, [$cb, @_];
555 $unblock_scheduler->ready;
556 }
557}
558
559=back
560
281=cut 561=cut
282 562
2831; 5631;
284 564
285=head1 BUGS/LIMITATIONS 565=head1 BUGS/LIMITATIONS
286 566
287 - you must make very sure that no coro is still active on global destruction. 567 - you must make very sure that no coro is still active on global
288 very bad things might happen otherwise (usually segfaults). 568 destruction. very bad things might happen otherwise (usually segfaults).
569
289 - this module is not thread-safe. You must only ever use this module from 570 - this module is not thread-safe. You should only ever use this module
290 the same thread (this requirement might be loosened in the future to 571 from the same thread (this requirement might be loosened in the future
291 allow per-thread schedulers, but Coro::State does not yet allow this). 572 to allow per-thread schedulers, but Coro::State does not yet allow
573 this).
292 574
293=head1 SEE ALSO 575=head1 SEE ALSO
294 576
295L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 577Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
296L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>, 578
297L<Coro::Handle>, L<Coro::Socket>. 579Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
580
581Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
582
583Embedding: L<Coro:MakeMaker>
298 584
299=head1 AUTHOR 585=head1 AUTHOR
300 586
301 Marc Lehmann <pcg@goof.com> 587 Marc Lehmann <schmorp@schmorp.de>
302 http://www.goof.com/pcg/marc/ 588 http://home.schmorp.de/
303 589
304=cut 590=cut
305 591

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