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Revision 1.36 by root, Mon Sep 24 01:36:20 2001 UTC vs.
Revision 1.139 by root, Thu Sep 27 15:52:30 2007 UTC

8 8
9 async { 9 async {
10 # some asynchronous thread of execution 10 # some asynchronous thread of execution
11 }; 11 };
12 12
13 # alternatively create an async process like this: 13 # alternatively create an async coroutine like this:
14 14
15 sub some_func : Coro { 15 sub some_func : Coro {
16 # some more async code 16 # some more async code
17 } 17 }
18 18
19 cede; 19 cede;
20 20
21=head1 DESCRIPTION 21=head1 DESCRIPTION
22 22
23This module collection manages coroutines. Coroutines are similar to 23This module collection manages coroutines. Coroutines are similar
24Threads but don't run in parallel. 24to threads but don't run in parallel at the same time even on SMP
25machines. The specific flavor of coroutine used in this module also
26guarantees you that it will not switch between coroutines unless
27necessary, at easily-identified points in your program, so locking and
28parallel access are rarely an issue, making coroutine programming much
29safer than threads programming.
25 30
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 $VERSION = '3.8';
56
45@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
46%EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
47 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48); 60);
49@EXPORT_OK = @{$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<$main> (of course).
93 111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essential you are encouraged to use the
114C<Coro::current> function instead.
115
94=cut 116=cut
117
118$main->{desc} = "[main::]";
95 119
96# maybe some other module used Coro::Specific before... 120# maybe some other module used Coro::Specific before...
97if ($current) {
98 $main->{specific} = $current->{specific}; 121$main->{specific} = $current->{specific}
99} 122 if $current;
100 123
101our $current = $main; 124_set_current $main;
102 125
103sub current() { $current } 126sub current() { $current }
104 127
105=item $idle 128=item $idle
106 129
107The coroutine to switch to when no other coroutine is running. The default 130A callback that is called whenever the scheduler finds no ready coroutines
108implementation prints "FATAL: deadlock detected" and exits. 131to run. The default implementation prints "FATAL: deadlock detected" and
132exits, because the program has no other way to continue.
109 133
110=cut 134This hook is overwritten by modules such as C<Coro::Timer> and
135C<Coro::Event> to wait on an external event that hopefully wake up a
136coroutine so the scheduler can run it.
111 137
112# should be done using priorities :( 138Please note that if your callback recursively invokes perl (e.g. for event
113our $idle = new Coro sub { 139handlers), then it must be prepared to be called recursively.
114 print STDERR "FATAL: deadlock detected\n"; 140
115 exit(51); 141=cut
142
143$idle = sub {
144 require Carp;
145 Carp::croak ("FATAL: deadlock detected");
116}; 146};
147
148sub _cancel {
149 my ($self) = @_;
150
151 # free coroutine data and mark as destructed
152 $self->_destroy
153 or return;
154
155 # call all destruction callbacks
156 $_->(@{$self->{status}})
157 for @{(delete $self->{destroy_cb}) || []};
158}
159
160sub _do_trace_sub {
161 &{$current->{_trace_sub_cb}}
162}
163
164sub _do_trace_line {
165 &{$current->{_trace_line_cb}}
166}
117 167
118# this coroutine is necessary because a coroutine 168# this coroutine is necessary because a coroutine
119# cannot destroy itself. 169# cannot destroy itself.
120my @destroy; 170my @destroy;
171my $manager;
172
121my $manager = new Coro sub { 173$manager = new Coro sub {
122 while() { 174 while () {
123 delete ((pop @destroy)->{_coro_state}) while @destroy; 175 (shift @destroy)->_cancel
176 while @destroy;
177
124 &schedule; 178 &schedule;
125 } 179 }
126}; 180};
181$manager->desc ("[coro manager]");
182$manager->prio (PRIO_MAX);
127 183
128# static methods. not really. 184# static methods. not really.
129 185
186=back
187
130=head2 STATIC METHODS 188=head2 STATIC METHODS
131 189
132Static methods are actually functions that operate on the current process only. 190Static methods are actually functions that operate on the current coroutine only.
133 191
134=over 4 192=over 4
135 193
136=item async { ... } [@args...] 194=item async { ... } [@args...]
137 195
138Create a new asynchronous process and return it's process object 196Create a new asynchronous coroutine and return it's coroutine object
139(usually unused). When the sub returns the new process is automatically 197(usually unused). When the sub returns the new coroutine is automatically
140terminated. 198terminated.
199
200Calling C<exit> in a coroutine will do the same as calling exit outside
201the coroutine. Likewise, when the coroutine dies, the program will exit,
202just as it would in the main program.
141 203
142 # create a new coroutine that just prints its arguments 204 # create a new coroutine that just prints its arguments
143 async { 205 async {
144 print "@_\n"; 206 print "@_\n";
145 } 1,2,3,4; 207 } 1,2,3,4;
146 208
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 209=cut
151 210
152sub async(&@) { 211sub async(&@) {
153 my $pid = new Coro @_; 212 my $coro = new Coro @_;
154 $manager->ready; # this ensures that the stack is cloned from the manager
155 $pid->ready; 213 $coro->ready;
156 $pid; 214 $coro
215}
216
217=item async_pool { ... } [@args...]
218
219Similar to C<async>, but uses a coroutine pool, so you should not call
220terminate or join (although you are allowed to), and you get a coroutine
221that might have executed other code already (which can be good or bad :).
222
223Also, the block is executed in an C<eval> context and a warning will be
224issued in case of an exception instead of terminating the program, as
225C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
226will not work in the expected way, unless you call terminate or cancel,
227which somehow defeats the purpose of pooling.
228
229The priority will be reset to C<0> after each job, otherwise the coroutine
230will be re-used "as-is".
231
232The pool size is limited to 8 idle coroutines (this can be adjusted by
233changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
234required.
235
236If you are concerned about pooled coroutines growing a lot because a
237single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
238{ terminate }> once per second or so to slowly replenish the pool. In
239addition to that, when the stacks used by a handler grows larger than 16kb
240(adjustable with $Coro::POOL_RSS) it will also exit.
241
242=cut
243
244our $POOL_SIZE = 8;
245our $POOL_RSS = 16 * 1024;
246our @async_pool;
247
248sub pool_handler {
249 my $cb;
250
251 while () {
252 eval {
253 while () {
254 _pool_1 $cb;
255 &$cb;
256 _pool_2 $cb;
257 &schedule;
258 }
259 };
260
261 last if $@ eq "\3terminate\2\n";
262 warn $@ if $@;
263 }
264}
265
266sub async_pool(&@) {
267 # this is also inlined into the unlock_scheduler
268 my $coro = (pop @async_pool) || new Coro \&pool_handler;
269
270 $coro->{_invoke} = [@_];
271 $coro->ready;
272
273 $coro
157} 274}
158 275
159=item schedule 276=item schedule
160 277
161Calls the scheduler. Please note that the current process will not be put 278Calls the scheduler. Please note that the current coroutine will not be put
162into the ready queue, so calling this function usually means you will 279into the ready queue, so calling this function usually means you will
163never be called again. 280never be called again unless something else (e.g. an event handler) calls
281ready.
164 282
165=cut 283The canonical way to wait on external events is this:
284
285 {
286 # remember current coroutine
287 my $current = $Coro::current;
288
289 # register a hypothetical event handler
290 on_event_invoke sub {
291 # wake up sleeping coroutine
292 $current->ready;
293 undef $current;
294 };
295
296 # call schedule until event occurred.
297 # in case we are woken up for other reasons
298 # (current still defined), loop.
299 Coro::schedule while $current;
300 }
166 301
167=item cede 302=item cede
168 303
169"Cede" to other processes. This function puts the current process into the 304"Cede" to other coroutines. This function puts the current coroutine into the
170ready queue and calls C<schedule>, which has the effect of giving up the 305ready queue and calls C<schedule>, which has the effect of giving up the
171current "timeslice" to other coroutines of the same or higher priority. 306current "timeslice" to other coroutines of the same or higher priority.
172 307
173=cut 308Returns true if at least one coroutine switch has happened.
174 309
310=item Coro::cede_notself
311
312Works like cede, but is not exported by default and will cede to any
313coroutine, regardless of priority, once.
314
315Returns true if at least one coroutine switch has happened.
316
175=item terminate 317=item terminate [arg...]
176 318
177Terminates the current process. 319Terminates the current coroutine with the given status values (see L<cancel>).
178
179Future versions of this function will allow result arguments.
180 320
181=cut 321=cut
182 322
183sub terminate { 323sub terminate {
184 $current->cancel; 324 $current->cancel (@_);
185 &schedule;
186 die; # NORETURN
187} 325}
188 326
189=back 327=back
190 328
191# dynamic methods 329# dynamic methods
192 330
193=head2 PROCESS METHODS 331=head2 COROUTINE METHODS
194 332
195These are the methods you can call on process objects. 333These are the methods you can call on coroutine objects.
196 334
197=over 4 335=over 4
198 336
199=item new Coro \&sub [, @args...] 337=item new Coro \&sub [, @args...]
200 338
201Create a new process and return it. When the sub returns the process 339Create a new coroutine and return it. When the sub returns the coroutine
202automatically terminates. To start the process you must first put it into 340automatically terminates as if C<terminate> with the returned values were
341called. To make the coroutine run you must first put it into the ready queue
203the ready queue by calling the ready method. 342by calling the ready method.
204 343
205The coderef you submit MUST NOT be a closure that refers to variables 344See C<async> for additional discussion.
206in an outer scope. This does NOT work. Pass arguments into it instead.
207 345
208=cut 346=cut
209 347
210sub _newcoro { 348sub _run_coro {
211 terminate &{+shift}; 349 terminate &{+shift};
212} 350}
213 351
214sub new { 352sub new {
215 my $class = shift; 353 my $class = shift;
216 bless {
217 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
218 }, $class;
219}
220 354
221=item $process->ready 355 $class->SUPER::new (\&_run_coro, @_)
356}
222 357
223Put the current process into the ready queue. 358=item $success = $coroutine->ready
224 359
225=cut 360Put the given coroutine into the ready queue (according to it's priority)
361and return true. If the coroutine is already in the ready queue, do nothing
362and return false.
226 363
227=item $process->cancel 364=item $is_ready = $coroutine->is_ready
228 365
229Like C<terminate>, but terminates the specified process instead. 366Return wether the coroutine is currently the ready queue or not,
367
368=item $coroutine->cancel (arg...)
369
370Terminates the given coroutine and makes it return the given arguments as
371status (default: the empty list). Never returns if the coroutine is the
372current coroutine.
230 373
231=cut 374=cut
232 375
233sub cancel { 376sub cancel {
377 my $self = shift;
378 $self->{status} = [@_];
379
380 if ($current == $self) {
234 push @destroy, $_[0]; 381 push @destroy, $self;
235 $manager->ready; 382 $manager->ready;
236 &schedule if $current == $_[0]; 383 &schedule while 1;
384 } else {
385 $self->_cancel;
386 }
237} 387}
238 388
389=item $coroutine->join
390
391Wait until the coroutine terminates and return any values given to the
392C<terminate> or C<cancel> functions. C<join> can be called multiple times
393from multiple coroutine.
394
395=cut
396
397sub join {
398 my $self = shift;
399
400 unless ($self->{status}) {
401 my $current = $current;
402
403 push @{$self->{destroy_cb}}, sub {
404 $current->ready;
405 undef $current;
406 };
407
408 &schedule while $current;
409 }
410
411 wantarray ? @{$self->{status}} : $self->{status}[0];
412}
413
414=item $coroutine->on_destroy (\&cb)
415
416Registers a callback that is called when this coroutine gets destroyed,
417but before it is joined. The callback gets passed the terminate arguments,
418if any.
419
420=cut
421
422sub on_destroy {
423 my ($self, $cb) = @_;
424
425 push @{ $self->{destroy_cb} }, $cb;
426}
427
239=item $oldprio = $process->prio($newprio) 428=item $oldprio = $coroutine->prio ($newprio)
240 429
241Sets the priority of the process. Higher priority processes get run before 430Sets (or gets, if the argument is missing) the priority of the
242lower priority processes. Priorities are smalled signed integer (currently 431coroutine. Higher priority coroutines get run before lower priority
432coroutines. Priorities are small signed integers (currently -4 .. +3),
243-4 .. +3), that you can refer to using PRIO_xxx constants (use the import 433that you can refer to using PRIO_xxx constants (use the import tag :prio
244tag :prio to get then): 434to get then):
245 435
246 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 436 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
247 3 > 1 > 0 > -1 > -3 > -4 437 3 > 1 > 0 > -1 > -3 > -4
248 438
249 # set priority to HIGH 439 # set priority to HIGH
250 current->prio(PRIO_HIGH); 440 current->prio(PRIO_HIGH);
251 441
252The idle coroutine ($Coro::idle) always has a lower priority than any 442The idle coroutine ($Coro::idle) always has a lower priority than any
253existing coroutine. 443existing coroutine.
254 444
255Changing the priority of the current process will take effect immediately, 445Changing the priority of the current coroutine will take effect immediately,
256but changing the priority of processes in the ready queue (but not 446but changing the priority of coroutines in the ready queue (but not
257running) will only take effect after the next schedule (of that 447running) will only take effect after the next schedule (of that
258process). This is a bug that will be fixed in some future version. 448coroutine). This is a bug that will be fixed in some future version.
259 449
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) 450=item $newprio = $coroutine->nice ($change)
269 451
270Similar to C<prio>, but subtract the given value from the priority (i.e. 452Similar to C<prio>, but subtract the given value from the priority (i.e.
271higher values mean lower priority, just as in unix). 453higher values mean lower priority, just as in unix).
272 454
273=cut 455=item $olddesc = $coroutine->desc ($newdesc)
274 456
275sub nice { 457Sets (or gets in case the argument is missing) the description for this
276 $_[0]{prio} -= $_[1]; 458coroutine. This is just a free-form string you can associate with a coroutine.
459
460=cut
461
462sub desc {
463 my $old = $_[0]{desc};
464 $_[0]{desc} = $_[1] if @_ > 1;
465 $old;
277} 466}
278 467
279=back 468=back
280 469
470=head2 GLOBAL FUNCTIONS
471
472=over 4
473
474=item Coro::nready
475
476Returns the number of coroutines that are currently in the ready state,
477i.e. that can be switched to. The value C<0> means that the only runnable
478coroutine is the currently running one, so C<cede> would have no effect,
479and C<schedule> would cause a deadlock unless there is an idle handler
480that wakes up some coroutines.
481
482=item my $guard = Coro::guard { ... }
483
484This creates and returns a guard object. Nothing happens until the object
485gets destroyed, in which case the codeblock given as argument will be
486executed. This is useful to free locks or other resources in case of a
487runtime error or when the coroutine gets canceled, as in both cases the
488guard block will be executed. The guard object supports only one method,
489C<< ->cancel >>, which will keep the codeblock from being executed.
490
491Example: set some flag and clear it again when the coroutine gets canceled
492or the function returns:
493
494 sub do_something {
495 my $guard = Coro::guard { $busy = 0 };
496 $busy = 1;
497
498 # do something that requires $busy to be true
499 }
500
501=cut
502
503sub guard(&) {
504 bless \(my $cb = $_[0]), "Coro::guard"
505}
506
507sub Coro::guard::cancel {
508 ${$_[0]} = sub { };
509}
510
511sub Coro::guard::DESTROY {
512 ${$_[0]}->();
513}
514
515
516=item unblock_sub { ... }
517
518This utility function takes a BLOCK or code reference and "unblocks" it,
519returning the new coderef. This means that the new coderef will return
520immediately without blocking, returning nothing, while the original code
521ref will be called (with parameters) from within its own coroutine.
522
523The reason this function exists is that many event libraries (such as the
524venerable L<Event|Event> module) are not coroutine-safe (a weaker form
525of thread-safety). This means you must not block within event callbacks,
526otherwise you might suffer from crashes or worse.
527
528This function allows your callbacks to block by executing them in another
529coroutine where it is safe to block. One example where blocking is handy
530is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
531disk.
532
533In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
534creating event callbacks that want to block.
535
536=cut
537
538our @unblock_queue;
539
540# we create a special coro because we want to cede,
541# to reduce pressure on the coro pool (because most callbacks
542# return immediately and can be reused) and because we cannot cede
543# inside an event callback.
544our $unblock_scheduler = new Coro sub {
545 while () {
546 while (my $cb = pop @unblock_queue) {
547 # this is an inlined copy of async_pool
548 my $coro = (pop @async_pool) || new Coro \&pool_handler;
549
550 $coro->{_invoke} = $cb;
551 $coro->ready;
552 cede; # for short-lived callbacks, this reduces pressure on the coro pool
553 }
554 schedule; # sleep well
555 }
556};
557$unblock_scheduler->desc ("[unblock_sub scheduler]");
558
559sub unblock_sub(&) {
560 my $cb = shift;
561
562 sub {
563 unshift @unblock_queue, [$cb, @_];
564 $unblock_scheduler->ready;
565 }
566}
567
568=back
569
281=cut 570=cut
282 571
2831; 5721;
284 573
285=head1 BUGS/LIMITATIONS 574=head1 BUGS/LIMITATIONS
286 575
287 - you must make very sure that no coro is still active on global destruction. 576 - you must make very sure that no coro is still active on global
288 very bad things might happen otherwise (usually segfaults). 577 destruction. very bad things might happen otherwise (usually segfaults).
578
289 - this module is not thread-safe. You must only ever use this module from 579 - 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 580 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). 581 to allow per-thread schedulers, but Coro::State does not yet allow
582 this).
292 583
293=head1 SEE ALSO 584=head1 SEE ALSO
294 585
295L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 586Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
296L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>, 587
297L<Coro::Handle>, L<Coro::Socket>. 588Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
589
590Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
591
592Embedding: L<Coro:MakeMaker>
298 593
299=head1 AUTHOR 594=head1 AUTHOR
300 595
301 Marc Lehmann <pcg@goof.com> 596 Marc Lehmann <schmorp@schmorp.de>
302 http://www.goof.com/pcg/marc/ 597 http://home.schmorp.de/
303 598
304=cut 599=cut
305 600

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