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Revision 1.42 by root, Tue Nov 6 20:37:20 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
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 = 0.52; 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 (@_) {
75 }; 92 };
76 } 93 }
77 94
78} 95}
79 96
97=over 4
98
80=item $main 99=item $main
81 100
82This coroutine represents the main program. 101This coroutine represents the main program.
83 102
84=cut 103=cut
85 104
86our $main = new Coro; 105$main = new Coro;
87 106
88=item $current (or as function: current) 107=item $current (or as function: current)
89 108
90The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). 109The current coroutine (the last coroutine switched to). The initial value
110is C<$main> (of course).
91 111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essential you are encouraged to use the
114C<Coro::current> function instead.
115
92=cut 116=cut
117
118$main->{desc} = "[main::]";
93 119
94# maybe some other module used Coro::Specific before... 120# maybe some other module used Coro::Specific before...
95if ($current) {
96 $main->{specific} = $current->{specific}; 121$main->{specific} = $current->{specific}
97} 122 if $current;
98 123
99our $current = $main; 124_set_current $main;
100 125
101sub current() { $current } 126sub current() { $current }
102 127
103=item $idle 128=item $idle
104 129
105The coroutine to switch to when no other coroutine is running. The default 130A callback that is called whenever the scheduler finds no ready coroutines
106implementation 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.
107 133
108=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.
109 137
110# should be done using priorities :( 138Please note that if your callback recursively invokes perl (e.g. for event
111our $idle = new Coro sub { 139handlers), then it must be prepared to be called recursively.
112 print STDERR "FATAL: deadlock detected\n"; 140
113 exit(51); 141=cut
142
143$idle = sub {
144 require Carp;
145 Carp::croak ("FATAL: deadlock detected");
114}; 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}
115 167
116# this coroutine is necessary because a coroutine 168# this coroutine is necessary because a coroutine
117# cannot destroy itself. 169# cannot destroy itself.
118my @destroy; 170my @destroy;
119my $manager; 171my $manager;
172
120$manager = new Coro sub { 173$manager = new Coro sub {
121 while() { 174 while () {
122 # by overwriting the state object with the manager we destroy it 175 (shift @destroy)->_cancel
123 # while still being able to schedule this coroutine (in case it has
124 # been readied multiple times. this is harmless since the manager
125 # can be called as many times as neccessary and will always
126 # remove itself from the runqueue
127 while (@destroy) { 176 while @destroy;
128 my $coro = pop @destroy; 177
129 $coro->{status} ||= [];
130 $_->ready for @{delete $coro->{join} || []};
131 $coro->{_coro_state} = $manager->{_coro_state};
132 }
133 &schedule; 178 &schedule;
134 } 179 }
135}; 180};
181$manager->desc ("[coro manager]");
182$manager->prio (PRIO_MAX);
136 183
137# static methods. not really. 184# static methods. not really.
138 185
186=back
187
139=head2 STATIC METHODS 188=head2 STATIC METHODS
140 189
141Static methods are actually functions that operate on the current process only. 190Static methods are actually functions that operate on the current coroutine only.
142 191
143=over 4 192=over 4
144 193
145=item async { ... } [@args...] 194=item async { ... } [@args...]
146 195
147Create a new asynchronous process and return it's process object 196Create a new asynchronous coroutine and return it's coroutine object
148(usually unused). When the sub returns the new process is automatically 197(usually unused). When the sub returns the new coroutine is automatically
149terminated. 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.
150 203
151 # create a new coroutine that just prints its arguments 204 # create a new coroutine that just prints its arguments
152 async { 205 async {
153 print "@_\n"; 206 print "@_\n";
154 } 1,2,3,4; 207 } 1,2,3,4;
155 208
156The coderef you submit MUST NOT be a closure that refers to variables
157in an outer scope. This does NOT work. Pass arguments into it instead.
158
159=cut 209=cut
160 210
161sub async(&@) { 211sub async(&@) {
162 my $pid = new Coro @_; 212 my $coro = new Coro @_;
163 $manager->ready; # this ensures that the stack is cloned from the manager
164 $pid->ready; 213 $coro->ready;
165 $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
166} 274}
167 275
168=item schedule 276=item schedule
169 277
170Calls 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
171into the ready queue, so calling this function usually means you will 279into the ready queue, so calling this function usually means you will
172never be called again. 280never be called again unless something else (e.g. an event handler) calls
281ready.
173 282
174=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 }
175 301
176=item cede 302=item cede
177 303
178"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
179ready 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
180current "timeslice" to other coroutines of the same or higher priority. 306current "timeslice" to other coroutines of the same or higher priority.
181 307
182=cut 308Returns true if at least one coroutine switch has happened.
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.
183 316
184=item terminate [arg...] 317=item terminate [arg...]
185 318
186Terminates the current process. 319Terminates the current coroutine with the given status values (see L<cancel>).
187
188Future versions of this function will allow result arguments.
189 320
190=cut 321=cut
191 322
192sub terminate { 323sub terminate {
193 $current->{status} = [@_];
194 $current->cancel; 324 $current->cancel (@_);
195 &schedule;
196 die; # NORETURN
197} 325}
198 326
199=back 327=back
200 328
201# dynamic methods 329# dynamic methods
202 330
203=head2 PROCESS METHODS 331=head2 COROUTINE METHODS
204 332
205These are the methods you can call on process objects. 333These are the methods you can call on coroutine objects.
206 334
207=over 4 335=over 4
208 336
209=item new Coro \&sub [, @args...] 337=item new Coro \&sub [, @args...]
210 338
211Create 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
212automatically terminates as if C<terminate> with the returned values were 340automatically terminates as if C<terminate> with the returned values were
213called. To make the process run you must first put it into the ready queue 341called. To make the coroutine run you must first put it into the ready queue
214by calling the ready method. 342by calling the ready method.
215 343
216=cut 344See C<async> for additional discussion.
217 345
346=cut
347
218sub _newcoro { 348sub _run_coro {
219 terminate &{+shift}; 349 terminate &{+shift};
220} 350}
221 351
222sub new { 352sub new {
223 my $class = shift; 353 my $class = shift;
224 bless {
225 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
226 }, $class;
227}
228 354
229=item $process->ready 355 $class->SUPER::new (\&_run_coro, @_)
356}
230 357
231Put the given process into the ready queue. 358=item $success = $coroutine->ready
232 359
233=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.
234 363
235=item $process->cancel 364=item $is_ready = $coroutine->is_ready
236 365
237Like 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.
238 373
239=cut 374=cut
240 375
241sub cancel { 376sub cancel {
377 my $self = shift;
378 $self->{status} = [@_];
379
380 if ($current == $self) {
242 push @destroy, $_[0]; 381 push @destroy, $self;
243 $manager->ready; 382 $manager->ready;
244 &schedule if $current == $_[0]; 383 &schedule while 1;
384 } else {
385 $self->_cancel;
386 }
245} 387}
246 388
247=item $process->join 389=item $coroutine->join
248 390
249Wait until the coroutine terminates and return any values given to the 391Wait until the coroutine terminates and return any values given to the
250C<terminate> function. C<join> can be called multiple times from multiple 392C<terminate> or C<cancel> functions. C<join> can be called multiple times
251processes. 393from multiple coroutine.
252 394
253=cut 395=cut
254 396
255sub join { 397sub join {
256 my $self = shift; 398 my $self = shift;
399
257 unless ($self->{status}) { 400 unless ($self->{status}) {
258 push @{$self->{join}}, $current; 401 my $current = $current;
259 &schedule; 402
403 push @{$self->{destroy_cb}}, sub {
404 $current->ready;
405 undef $current;
406 };
407
408 &schedule while $current;
260 } 409 }
410
261 wantarray ? @{$self->{status}} : $self->{status}[0]; 411 wantarray ? @{$self->{status}} : $self->{status}[0];
262} 412}
263 413
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
264=item $oldprio = $process->prio($newprio) 428=item $oldprio = $coroutine->prio ($newprio)
265 429
266Sets (or gets, if the argument is missing) the priority of the 430Sets (or gets, if the argument is missing) the priority of the
267process. Higher priority processes get run before lower priority 431coroutine. Higher priority coroutines get run before lower priority
268processes. Priorities are smalled signed integer (currently -4 .. +3), 432coroutines. Priorities are small signed integers (currently -4 .. +3),
269that you can refer to using PRIO_xxx constants (use the import tag :prio 433that you can refer to using PRIO_xxx constants (use the import tag :prio
270to get then): 434to get then):
271 435
272 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
273 3 > 1 > 0 > -1 > -3 > -4 437 3 > 1 > 0 > -1 > -3 > -4
276 current->prio(PRIO_HIGH); 440 current->prio(PRIO_HIGH);
277 441
278The idle coroutine ($Coro::idle) always has a lower priority than any 442The idle coroutine ($Coro::idle) always has a lower priority than any
279existing coroutine. 443existing coroutine.
280 444
281Changing the priority of the current process will take effect immediately, 445Changing the priority of the current coroutine will take effect immediately,
282but changing the priority of processes in the ready queue (but not 446but changing the priority of coroutines in the ready queue (but not
283running) will only take effect after the next schedule (of that 447running) will only take effect after the next schedule (of that
284process). 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.
285 449
286=cut
287
288sub prio {
289 my $old = $_[0]{prio};
290 $_[0]{prio} = $_[1] if @_ > 1;
291 $old;
292}
293
294=item $newprio = $process->nice($change) 450=item $newprio = $coroutine->nice ($change)
295 451
296Similar 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.
297higher values mean lower priority, just as in unix). 453higher values mean lower priority, just as in unix).
298 454
299=cut
300
301sub nice {
302 $_[0]{prio} -= $_[1];
303}
304
305=item $olddesc = $process->desc($newdesc) 455=item $olddesc = $coroutine->desc ($newdesc)
306 456
307Sets (or gets in case the argument is missing) the description for this 457Sets (or gets in case the argument is missing) the description for this
308process. This is just a free-form string you can associate with a process. 458coroutine. This is just a free-form string you can associate with a coroutine.
309 459
310=cut 460=cut
311 461
312sub desc { 462sub desc {
313 my $old = $_[0]{desc}; 463 my $old = $_[0]{desc};
315 $old; 465 $old;
316} 466}
317 467
318=back 468=back
319 469
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
320=cut 570=cut
321 571
3221; 5721;
323 573
324=head1 BUGS/LIMITATIONS 574=head1 BUGS/LIMITATIONS
325 575
326 - 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
327 very bad things might happen otherwise (usually segfaults). 577 destruction. very bad things might happen otherwise (usually segfaults).
578
328 - this module is not thread-safe. You should only ever use this module from 579 - this module is not thread-safe. You should only ever use this module
329 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
330 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).
331 583
332=head1 SEE ALSO 584=head1 SEE ALSO
333 585
334L<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>.
335L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>, 587
336L<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>
337 593
338=head1 AUTHOR 594=head1 AUTHOR
339 595
340 Marc Lehmann <pcg@goof.com> 596 Marc Lehmann <schmorp@schmorp.de>
341 http://www.goof.com/pcg/marc/ 597 http://home.schmorp.de/
342 598
343=cut 599=cut
344 600

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