ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/Coro/Coro.pm
(Generate patch)

Comparing Coro/Coro.pm (file contents):
Revision 1.52 by root, Tue May 27 00:26:34 2003 UTC vs.
Revision 1.128 by root, Wed Sep 19 21:39:15 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 = 0.652; 51our $idle; # idle handler
52our $main; # main coroutine
53our $current; # current coroutine
42 54
55our $VERSION = '3.7';
56
43@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
44%EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
45 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
46); 60);
47@EXPORT_OK = @{$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<$main> (of course).
111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essential you are encouraged to use the
114C<Coro::current> function instead.
93 115
94=cut 116=cut
95 117
96# maybe some other module used Coro::Specific before... 118# maybe some other module used Coro::Specific before...
97if ($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;
121my $manager; 161my $manager;
162
122$manager = new Coro sub { 163$manager = new Coro sub {
123 while() { 164 while () {
124 # by overwriting the state object with the manager we destroy it 165 (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) { 166 while @destroy;
130 my $coro = pop @destroy; 167
131 $coro->{status} ||= [];
132 $_->ready for @{delete $coro->{join} || []};
133 $coro->{_coro_state} = $manager->{_coro_state};
134 }
135 &schedule; 168 &schedule;
136 } 169 }
137}; 170};
138 171
172$manager->prio (PRIO_MAX);
173
139# static methods. not really. 174# static methods. not really.
140 175
141=back 176=back
142 177
143=head2 STATIC METHODS 178=head2 STATIC METHODS
144 179
145Static methods are actually functions that operate on the current process only. 180Static methods are actually functions that operate on the current coroutine only.
146 181
147=over 4 182=over 4
148 183
149=item async { ... } [@args...] 184=item async { ... } [@args...]
150 185
151Create a new asynchronous process and return it's process object 186Create a new asynchronous coroutine and return it's coroutine object
152(usually unused). When the sub returns the new process is automatically 187(usually unused). When the sub returns the new coroutine is automatically
153terminated. 188terminated.
189
190Calling C<exit> in a coroutine will do the same as calling exit outside
191the coroutine. Likewise, when the coroutine dies, the program will exit,
192just as it would in the main program.
154 193
155 # create a new coroutine that just prints its arguments 194 # create a new coroutine that just prints its arguments
156 async { 195 async {
157 print "@_\n"; 196 print "@_\n";
158 } 1,2,3,4; 197 } 1,2,3,4;
159 198
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 199=cut
164 200
165sub async(&@) { 201sub async(&@) {
166 my $pid = new Coro @_; 202 my $coro = new Coro @_;
167 $manager->ready; # this ensures that the stack is cloned from the manager
168 $pid->ready; 203 $coro->ready;
169 $pid; 204 $coro
205}
206
207=item async_pool { ... } [@args...]
208
209Similar to C<async>, but uses a coroutine pool, so you should not call
210terminate or join (although you are allowed to), and you get a coroutine
211that might have executed other code already (which can be good or bad :).
212
213Also, the block is executed in an C<eval> context and a warning will be
214issued in case of an exception instead of terminating the program, as
215C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
216will not work in the expected way, unless you call terminate or cancel,
217which somehow defeats the purpose of pooling.
218
219The priority will be reset to C<0> after each job, otherwise the coroutine
220will be re-used "as-is".
221
222The pool size is limited to 8 idle coroutines (this can be adjusted by
223changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
224required.
225
226If you are concerned about pooled coroutines growing a lot because a
227single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {
228terminate }> once per second or so to slowly replenish the pool.
229
230=cut
231
232our $POOL_SIZE = 8;
233our @pool;
234
235sub pool_handler {
236 while () {
237 eval {
238 my ($cb, @arg) = @{ delete $current->{_invoke} or return };
239 $cb->(@arg);
240 };
241 warn $@ if $@;
242
243 last if @pool >= $POOL_SIZE;
244 push @pool, $current;
245
246 $current->save (Coro::State::SAVE_DEF);
247 $current->prio (0);
248 schedule;
249 }
250}
251
252sub async_pool(&@) {
253 # this is also inlined into the unlock_scheduler
254 my $coro = (pop @pool) || do {
255 my $coro = new Coro \&pool_handler;
256 $coro->{desc} = "async_pool";
257 $coro
258 };
259
260 $coro->{_invoke} = [@_];
261 $coro->ready;
262
263 $coro
170} 264}
171 265
172=item schedule 266=item schedule
173 267
174Calls the scheduler. Please note that the current process will not be put 268Calls the scheduler. Please note that the current coroutine will not be put
175into the ready queue, so calling this function usually means you will 269into the ready queue, so calling this function usually means you will
176never be called again. 270never be called again unless something else (e.g. an event handler) calls
271ready.
177 272
178=cut 273The canonical way to wait on external events is this:
274
275 {
276 # remember current coroutine
277 my $current = $Coro::current;
278
279 # register a hypothetical event handler
280 on_event_invoke sub {
281 # wake up sleeping coroutine
282 $current->ready;
283 undef $current;
284 };
285
286 # call schedule until event occurred.
287 # in case we are woken up for other reasons
288 # (current still defined), loop.
289 Coro::schedule while $current;
290 }
179 291
180=item cede 292=item cede
181 293
182"Cede" to other processes. This function puts the current process into the 294"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 295ready queue and calls C<schedule>, which has the effect of giving up the
184current "timeslice" to other coroutines of the same or higher priority. 296current "timeslice" to other coroutines of the same or higher priority.
185 297
186=cut 298Returns true if at least one coroutine switch has happened.
299
300=item Coro::cede_notself
301
302Works like cede, but is not exported by default and will cede to any
303coroutine, regardless of priority, once.
304
305Returns true if at least one coroutine switch has happened.
187 306
188=item terminate [arg...] 307=item terminate [arg...]
189 308
190Terminates the current process. 309Terminates the current coroutine with the given status values (see L<cancel>).
191
192Future versions of this function will allow result arguments.
193 310
194=cut 311=cut
195 312
196sub terminate { 313sub terminate {
197 $current->{status} = [@_];
198 $current->cancel; 314 $current->cancel (@_);
199 &schedule;
200 die; # NORETURN
201} 315}
202 316
203=back 317=back
204 318
205# dynamic methods 319# dynamic methods
206 320
207=head2 PROCESS METHODS 321=head2 COROUTINE METHODS
208 322
209These are the methods you can call on process objects. 323These are the methods you can call on coroutine objects.
210 324
211=over 4 325=over 4
212 326
213=item new Coro \&sub [, @args...] 327=item new Coro \&sub [, @args...]
214 328
215Create a new process and return it. When the sub returns the process 329Create a new coroutine and return it. When the sub returns the coroutine
216automatically terminates as if C<terminate> with the returned values were 330automatically 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 331called. To make the coroutine run you must first put it into the ready queue
218by calling the ready method. 332by calling the ready method.
219 333
220=cut 334See C<async> for additional discussion.
221 335
336=cut
337
222sub _newcoro { 338sub _run_coro {
223 terminate &{+shift}; 339 terminate &{+shift};
224} 340}
225 341
226sub new { 342sub new {
227 my $class = shift; 343 my $class = shift;
228 bless {
229 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
230 }, $class;
231}
232 344
233=item $process->ready 345 $class->SUPER::new (\&_run_coro, @_)
346}
234 347
235Put the given process into the ready queue. 348=item $success = $coroutine->ready
236 349
237=cut 350Put the given coroutine into the ready queue (according to it's priority)
351and return true. If the coroutine is already in the ready queue, do nothing
352and return false.
238 353
239=item $process->cancel 354=item $is_ready = $coroutine->is_ready
240 355
241Like C<terminate>, but terminates the specified process instead. 356Return wether the coroutine is currently the ready queue or not,
357
358=item $coroutine->cancel (arg...)
359
360Terminates the given coroutine and makes it return the given arguments as
361status (default: the empty list). Never returns if the coroutine is the
362current coroutine.
242 363
243=cut 364=cut
244 365
245sub cancel { 366sub cancel {
367 my $self = shift;
368 $self->{status} = [@_];
369
370 if ($current == $self) {
246 push @destroy, $_[0]; 371 push @destroy, $self;
247 $manager->ready; 372 $manager->ready;
248 &schedule if $current == $_[0]; 373 &schedule while 1;
374 } else {
375 $self->_cancel;
376 }
249} 377}
250 378
251=item $process->join 379=item $coroutine->join
252 380
253Wait until the coroutine terminates and return any values given to the 381Wait until the coroutine terminates and return any values given to the
254C<terminate> function. C<join> can be called multiple times from multiple 382C<terminate> or C<cancel> functions. C<join> can be called multiple times
255processes. 383from multiple coroutine.
256 384
257=cut 385=cut
258 386
259sub join { 387sub join {
260 my $self = shift; 388 my $self = shift;
389
261 unless ($self->{status}) { 390 unless ($self->{status}) {
262 push @{$self->{join}}, $current; 391 my $current = $current;
263 &schedule; 392
393 push @{$self->{destroy_cb}}, sub {
394 $current->ready;
395 undef $current;
396 };
397
398 &schedule while $current;
264 } 399 }
400
265 wantarray ? @{$self->{status}} : $self->{status}[0]; 401 wantarray ? @{$self->{status}} : $self->{status}[0];
266} 402}
267 403
404=item $coroutine->on_destroy (\&cb)
405
406Registers a callback that is called when this coroutine gets destroyed,
407but before it is joined. The callback gets passed the terminate arguments,
408if any.
409
410=cut
411
412sub on_destroy {
413 my ($self, $cb) = @_;
414
415 push @{ $self->{destroy_cb} }, $cb;
416}
417
268=item $oldprio = $process->prio($newprio) 418=item $oldprio = $coroutine->prio ($newprio)
269 419
270Sets (or gets, if the argument is missing) the priority of the 420Sets (or gets, if the argument is missing) the priority of the
271process. Higher priority processes get run before lower priority 421coroutine. Higher priority coroutines get run before lower priority
272processes. Priorities are small signed integers (currently -4 .. +3), 422coroutines. Priorities are small signed integers (currently -4 .. +3),
273that you can refer to using PRIO_xxx constants (use the import tag :prio 423that you can refer to using PRIO_xxx constants (use the import tag :prio
274to get then): 424to get then):
275 425
276 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 426 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
277 3 > 1 > 0 > -1 > -3 > -4 427 3 > 1 > 0 > -1 > -3 > -4
280 current->prio(PRIO_HIGH); 430 current->prio(PRIO_HIGH);
281 431
282The idle coroutine ($Coro::idle) always has a lower priority than any 432The idle coroutine ($Coro::idle) always has a lower priority than any
283existing coroutine. 433existing coroutine.
284 434
285Changing the priority of the current process will take effect immediately, 435Changing the priority of the current coroutine will take effect immediately,
286but changing the priority of processes in the ready queue (but not 436but changing the priority of coroutines in the ready queue (but not
287running) will only take effect after the next schedule (of that 437running) will only take effect after the next schedule (of that
288process). This is a bug that will be fixed in some future version. 438coroutine). This is a bug that will be fixed in some future version.
289 439
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) 440=item $newprio = $coroutine->nice ($change)
299 441
300Similar to C<prio>, but subtract the given value from the priority (i.e. 442Similar to C<prio>, but subtract the given value from the priority (i.e.
301higher values mean lower priority, just as in unix). 443higher values mean lower priority, just as in unix).
302 444
303=cut
304
305sub nice {
306 $_[0]{prio} -= $_[1];
307}
308
309=item $olddesc = $process->desc($newdesc) 445=item $olddesc = $coroutine->desc ($newdesc)
310 446
311Sets (or gets in case the argument is missing) the description for this 447Sets (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. 448coroutine. This is just a free-form string you can associate with a coroutine.
313 449
314=cut 450=cut
315 451
316sub desc { 452sub desc {
317 my $old = $_[0]{desc}; 453 my $old = $_[0]{desc};
319 $old; 455 $old;
320} 456}
321 457
322=back 458=back
323 459
460=head2 GLOBAL FUNCTIONS
461
462=over 4
463
464=item Coro::nready
465
466Returns the number of coroutines that are currently in the ready state,
467i.e. that can be switched to. The value C<0> means that the only runnable
468coroutine is the currently running one, so C<cede> would have no effect,
469and C<schedule> would cause a deadlock unless there is an idle handler
470that wakes up some coroutines.
471
472=item my $guard = Coro::guard { ... }
473
474This creates and returns a guard object. Nothing happens until the object
475gets destroyed, in which case the codeblock given as argument will be
476executed. This is useful to free locks or other resources in case of a
477runtime error or when the coroutine gets canceled, as in both cases the
478guard block will be executed. The guard object supports only one method,
479C<< ->cancel >>, which will keep the codeblock from being executed.
480
481Example: set some flag and clear it again when the coroutine gets canceled
482or the function returns:
483
484 sub do_something {
485 my $guard = Coro::guard { $busy = 0 };
486 $busy = 1;
487
488 # do something that requires $busy to be true
489 }
490
491=cut
492
493sub guard(&) {
494 bless \(my $cb = $_[0]), "Coro::guard"
495}
496
497sub Coro::guard::cancel {
498 ${$_[0]} = sub { };
499}
500
501sub Coro::guard::DESTROY {
502 ${$_[0]}->();
503}
504
505
506=item unblock_sub { ... }
507
508This utility function takes a BLOCK or code reference and "unblocks" it,
509returning the new coderef. This means that the new coderef will return
510immediately without blocking, returning nothing, while the original code
511ref will be called (with parameters) from within its own coroutine.
512
513The reason this function exists is that many event libraries (such as the
514venerable L<Event|Event> module) are not coroutine-safe (a weaker form
515of thread-safety). This means you must not block within event callbacks,
516otherwise you might suffer from crashes or worse.
517
518This function allows your callbacks to block by executing them in another
519coroutine where it is safe to block. One example where blocking is handy
520is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
521disk.
522
523In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
524creating event callbacks that want to block.
525
526=cut
527
528our @unblock_queue;
529
530# we create a special coro because we want to cede,
531# to reduce pressure on the coro pool (because most callbacks
532# return immediately and can be reused) and because we cannot cede
533# inside an event callback.
534our $unblock_scheduler = async {
535 while () {
536 while (my $cb = pop @unblock_queue) {
537 # this is an inlined copy of async_pool
538 my $coro = (pop @pool or new Coro \&pool_handler);
539
540 $coro->{_invoke} = $cb;
541 $coro->ready;
542 cede; # for short-lived callbacks, this reduces pressure on the coro pool
543 }
544 schedule; # sleep well
545 }
546};
547
548sub unblock_sub(&) {
549 my $cb = shift;
550
551 sub {
552 unshift @unblock_queue, [$cb, @_];
553 $unblock_scheduler->ready;
554 }
555}
556
557=back
558
324=cut 559=cut
325 560
3261; 5611;
327 562
328=head1 BUGS/LIMITATIONS 563=head1 BUGS/LIMITATIONS
329 564
330 - you must make very sure that no coro is still active on global 565 - you must make very sure that no coro is still active on global
331 destruction. very bad things might happen otherwise (usually segfaults 566 destruction. very bad things might happen otherwise (usually segfaults).
332 or "panic: top_env").
333 567
334 - this module is not thread-safe. You should only ever use this module 568 - this module is not thread-safe. You should only ever use this module
335 from the same thread (this requirement might be losened in the future 569 from the same thread (this requirement might be loosened in the future
336 to allow per-thread schedulers, but Coro::State does not yet allow 570 to allow per-thread schedulers, but Coro::State does not yet allow
337 this). 571 this).
338 572
339=head1 SEE ALSO 573=head1 SEE ALSO
340 574
341L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 575Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
342L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>, 576
343L<Coro::Handle>, L<Coro::Socket>. 577Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
578
579Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
580
581Embedding: L<Coro:MakeMaker>
344 582
345=head1 AUTHOR 583=head1 AUTHOR
346 584
347 Marc Lehmann <pcg@goof.com> 585 Marc Lehmann <schmorp@schmorp.de>
348 http://www.goof.com/pcg/marc/ 586 http://home.schmorp.de/
349 587
350=cut 588=cut
351 589

Diff Legend

Removed lines
+ Added lines
< Changed lines
> Changed lines