1 |
=head1 NAME |
2 |
|
3 |
Coro - coroutine process abstraction |
4 |
|
5 |
=head1 SYNOPSIS |
6 |
|
7 |
use Coro; |
8 |
|
9 |
async { |
10 |
# some asynchronous thread of execution |
11 |
}; |
12 |
|
13 |
# alternatively create an async coroutine like this: |
14 |
|
15 |
sub some_func : Coro { |
16 |
# some more async code |
17 |
} |
18 |
|
19 |
cede; |
20 |
|
21 |
=head1 DESCRIPTION |
22 |
|
23 |
This module collection manages coroutines. Coroutines are similar |
24 |
to threads but don't run in parallel at the same time even on SMP |
25 |
machines. The specific flavor of coroutine use din this module also |
26 |
guarentees you that it will not switch between coroutines unless |
27 |
necessary, at easily-identified points in your program, so locking and |
28 |
parallel access are rarely an issue, making coroutine programming much |
29 |
safer than threads programming. |
30 |
|
31 |
(Perl, however, does not natively support real threads but instead does a |
32 |
very slow and memory-intensive emulation of processes using threads. This |
33 |
is a performance win on Windows machines, and a loss everywhere else). |
34 |
|
35 |
In this module, coroutines are defined as "callchain + lexical variables + |
36 |
@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain, |
37 |
its own set of lexicals and its own set of perls most important global |
38 |
variables. |
39 |
|
40 |
=cut |
41 |
|
42 |
package Coro; |
43 |
|
44 |
use strict; |
45 |
no warnings "uninitialized"; |
46 |
|
47 |
use Coro::State; |
48 |
|
49 |
use base qw(Coro::State Exporter); |
50 |
|
51 |
our $idle; # idle handler |
52 |
our $main; # main coroutine |
53 |
our $current; # current coroutine |
54 |
|
55 |
our $VERSION = '3.5'; |
56 |
|
57 |
our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); |
58 |
our %EXPORT_TAGS = ( |
59 |
prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
60 |
); |
61 |
our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
62 |
|
63 |
{ |
64 |
my @async; |
65 |
my $init; |
66 |
|
67 |
# this way of handling attributes simply is NOT scalable ;() |
68 |
sub import { |
69 |
no strict 'refs'; |
70 |
|
71 |
Coro->export_to_level (1, @_); |
72 |
|
73 |
my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; |
74 |
*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { |
75 |
my ($package, $ref) = (shift, shift); |
76 |
my @attrs; |
77 |
for (@_) { |
78 |
if ($_ eq "Coro") { |
79 |
push @async, $ref; |
80 |
unless ($init++) { |
81 |
eval q{ |
82 |
sub INIT { |
83 |
&async(pop @async) while @async; |
84 |
} |
85 |
}; |
86 |
} |
87 |
} else { |
88 |
push @attrs, $_; |
89 |
} |
90 |
} |
91 |
return $old ? $old->($package, $ref, @attrs) : @attrs; |
92 |
}; |
93 |
} |
94 |
|
95 |
} |
96 |
|
97 |
=over 4 |
98 |
|
99 |
=item $main |
100 |
|
101 |
This coroutine represents the main program. |
102 |
|
103 |
=cut |
104 |
|
105 |
$main = new Coro; |
106 |
|
107 |
=item $current (or as function: current) |
108 |
|
109 |
The current coroutine (the last coroutine switched to). The initial value |
110 |
is C<$main> (of course). |
111 |
|
112 |
This variable is B<strictly> I<read-only>. It is provided for performance |
113 |
reasons. If performance is not essentiel you are encouraged to use the |
114 |
C<Coro::current> function instead. |
115 |
|
116 |
=cut |
117 |
|
118 |
# maybe some other module used Coro::Specific before... |
119 |
$main->{specific} = $current->{specific} |
120 |
if $current; |
121 |
|
122 |
_set_current $main; |
123 |
|
124 |
sub current() { $current } |
125 |
|
126 |
=item $idle |
127 |
|
128 |
A callback that is called whenever the scheduler finds no ready coroutines |
129 |
to run. The default implementation prints "FATAL: deadlock detected" and |
130 |
exits, because the program has no other way to continue. |
131 |
|
132 |
This hook is overwritten by modules such as C<Coro::Timer> and |
133 |
C<Coro::Event> to wait on an external event that hopefully wake up a |
134 |
coroutine so the scheduler can run it. |
135 |
|
136 |
Please note that if your callback recursively invokes perl (e.g. for event |
137 |
handlers), then it must be prepared to be called recursively. |
138 |
|
139 |
=cut |
140 |
|
141 |
$idle = sub { |
142 |
require Carp; |
143 |
Carp::croak ("FATAL: deadlock detected"); |
144 |
}; |
145 |
|
146 |
sub _cancel { |
147 |
my ($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 |
} |
157 |
|
158 |
# this coroutine is necessary because a coroutine |
159 |
# cannot destroy itself. |
160 |
my @destroy; |
161 |
my $manager; |
162 |
|
163 |
$manager = new Coro sub { |
164 |
while () { |
165 |
(shift @destroy)->_cancel |
166 |
while @destroy; |
167 |
|
168 |
&schedule; |
169 |
} |
170 |
}; |
171 |
|
172 |
$manager->prio (PRIO_MAX); |
173 |
|
174 |
# static methods. not really. |
175 |
|
176 |
=back |
177 |
|
178 |
=head2 STATIC METHODS |
179 |
|
180 |
Static methods are actually functions that operate on the current coroutine only. |
181 |
|
182 |
=over 4 |
183 |
|
184 |
=item async { ... } [@args...] |
185 |
|
186 |
Create a new asynchronous coroutine and return it's coroutine object |
187 |
(usually unused). When the sub returns the new coroutine is automatically |
188 |
terminated. |
189 |
|
190 |
Calling C<exit> in a coroutine will not work correctly, so do not do that. |
191 |
|
192 |
When the coroutine dies, the program will exit, just as in the main |
193 |
program. |
194 |
|
195 |
# create a new coroutine that just prints its arguments |
196 |
async { |
197 |
print "@_\n"; |
198 |
} 1,2,3,4; |
199 |
|
200 |
=cut |
201 |
|
202 |
sub async(&@) { |
203 |
my $coro = new Coro @_; |
204 |
$coro->ready; |
205 |
$coro |
206 |
} |
207 |
|
208 |
=item async_pool { ... } [@args...] |
209 |
|
210 |
Similar to C<async>, but uses a coroutine pool, so you should not call |
211 |
terminate or join (although you are allowed to), and you get a coroutine |
212 |
that might have executed other code already (which can be good or bad :). |
213 |
|
214 |
Also, the block is executed in an C<eval> context and a warning will be |
215 |
issued in case of an exception instead of terminating the program, as |
216 |
C<async> does. As the coroutine is being reused, stuff like C<on_destroy> |
217 |
will not work in the expected way, unless you call terminate or cancel, |
218 |
which somehow defeats the purpose of pooling. |
219 |
|
220 |
The priority will be reset to C<0> after each job, otherwise the coroutine |
221 |
will be re-used "as-is". |
222 |
|
223 |
The pool size is limited to 8 idle coroutines (this can be adjusted by |
224 |
changing $Coro::POOL_SIZE), and there can be as many non-idle coros as |
225 |
required. |
226 |
|
227 |
If you are concerned about pooled coroutines growing a lot because a |
228 |
single C<async_pool> used a lot of stackspace you can e.g. C<async_pool { |
229 |
terminate }> once per second or so to slowly replenish the pool. |
230 |
|
231 |
=cut |
232 |
|
233 |
our $POOL_SIZE = 8; |
234 |
our @pool; |
235 |
|
236 |
sub pool_handler { |
237 |
while () { |
238 |
eval { |
239 |
my ($cb, @arg) = @{ delete $current->{_invoke} or return }; |
240 |
$cb->(@arg); |
241 |
}; |
242 |
warn $@ if $@; |
243 |
|
244 |
last if @pool >= $POOL_SIZE; |
245 |
push @pool, $current; |
246 |
|
247 |
$current->prio (0); |
248 |
schedule; |
249 |
} |
250 |
} |
251 |
|
252 |
sub async_pool(&@) { |
253 |
# this is also inlined into the unlock_scheduler |
254 |
my $coro = (pop @pool or new Coro \&pool_handler); |
255 |
|
256 |
$coro->{_invoke} = [@_]; |
257 |
$coro->ready; |
258 |
|
259 |
$coro |
260 |
} |
261 |
|
262 |
=item schedule |
263 |
|
264 |
Calls the scheduler. Please note that the current coroutine will not be put |
265 |
into the ready queue, so calling this function usually means you will |
266 |
never be called again unless something else (e.g. an event handler) calls |
267 |
ready. |
268 |
|
269 |
The canonical way to wait on external events is this: |
270 |
|
271 |
{ |
272 |
# remember current coroutine |
273 |
my $current = $Coro::current; |
274 |
|
275 |
# register a hypothetical event handler |
276 |
on_event_invoke sub { |
277 |
# wake up sleeping coroutine |
278 |
$current->ready; |
279 |
undef $current; |
280 |
}; |
281 |
|
282 |
# call schedule until event occured. |
283 |
# in case we are woken up for other reasons |
284 |
# (current still defined), loop. |
285 |
Coro::schedule while $current; |
286 |
} |
287 |
|
288 |
=item cede |
289 |
|
290 |
"Cede" to other coroutines. This function puts the current coroutine into the |
291 |
ready queue and calls C<schedule>, which has the effect of giving up the |
292 |
current "timeslice" to other coroutines of the same or higher priority. |
293 |
|
294 |
Returns true if at least one coroutine switch has happened. |
295 |
|
296 |
=item Coro::cede_notself |
297 |
|
298 |
Works like cede, but is not exported by default and will cede to any |
299 |
coroutine, regardless of priority, once. |
300 |
|
301 |
Returns true if at least one coroutine switch has happened. |
302 |
|
303 |
=item terminate [arg...] |
304 |
|
305 |
Terminates the current coroutine with the given status values (see L<cancel>). |
306 |
|
307 |
=cut |
308 |
|
309 |
sub terminate { |
310 |
$current->cancel (@_); |
311 |
} |
312 |
|
313 |
=back |
314 |
|
315 |
# dynamic methods |
316 |
|
317 |
=head2 COROUTINE METHODS |
318 |
|
319 |
These are the methods you can call on coroutine objects. |
320 |
|
321 |
=over 4 |
322 |
|
323 |
=item new Coro \&sub [, @args...] |
324 |
|
325 |
Create a new coroutine and return it. When the sub returns the coroutine |
326 |
automatically terminates as if C<terminate> with the returned values were |
327 |
called. To make the coroutine run you must first put it into the ready queue |
328 |
by calling the ready method. |
329 |
|
330 |
Calling C<exit> in a coroutine will not work correctly, so do not do that. |
331 |
|
332 |
=cut |
333 |
|
334 |
sub _run_coro { |
335 |
terminate &{+shift}; |
336 |
} |
337 |
|
338 |
sub new { |
339 |
my $class = shift; |
340 |
|
341 |
$class->SUPER::new (\&_run_coro, @_) |
342 |
} |
343 |
|
344 |
=item $success = $coroutine->ready |
345 |
|
346 |
Put the given coroutine into the ready queue (according to it's priority) |
347 |
and return true. If the coroutine is already in the ready queue, do nothing |
348 |
and return false. |
349 |
|
350 |
=item $is_ready = $coroutine->is_ready |
351 |
|
352 |
Return wether the coroutine is currently the ready queue or not, |
353 |
|
354 |
=item $coroutine->cancel (arg...) |
355 |
|
356 |
Terminates the given coroutine and makes it return the given arguments as |
357 |
status (default: the empty list). Never returns if the coroutine is the |
358 |
current coroutine. |
359 |
|
360 |
=cut |
361 |
|
362 |
sub cancel { |
363 |
my $self = shift; |
364 |
$self->{status} = [@_]; |
365 |
|
366 |
if ($current == $self) { |
367 |
push @destroy, $self; |
368 |
$manager->ready; |
369 |
&schedule while 1; |
370 |
} else { |
371 |
$self->_cancel; |
372 |
} |
373 |
} |
374 |
|
375 |
=item $coroutine->join |
376 |
|
377 |
Wait until the coroutine terminates and return any values given to the |
378 |
C<terminate> or C<cancel> functions. C<join> can be called multiple times |
379 |
from multiple coroutine. |
380 |
|
381 |
=cut |
382 |
|
383 |
sub join { |
384 |
my $self = shift; |
385 |
|
386 |
unless ($self->{status}) { |
387 |
my $current = $current; |
388 |
|
389 |
push @{$self->{destroy_cb}}, sub { |
390 |
$current->ready; |
391 |
undef $current; |
392 |
}; |
393 |
|
394 |
&schedule while $current; |
395 |
} |
396 |
|
397 |
wantarray ? @{$self->{status}} : $self->{status}[0]; |
398 |
} |
399 |
|
400 |
=item $coroutine->on_destroy (\&cb) |
401 |
|
402 |
Registers a callback that is called when this coroutine gets destroyed, |
403 |
but before it is joined. The callback gets passed the terminate arguments, |
404 |
if any. |
405 |
|
406 |
=cut |
407 |
|
408 |
sub on_destroy { |
409 |
my ($self, $cb) = @_; |
410 |
|
411 |
push @{ $self->{destroy_cb} }, $cb; |
412 |
} |
413 |
|
414 |
=item $oldprio = $coroutine->prio ($newprio) |
415 |
|
416 |
Sets (or gets, if the argument is missing) the priority of the |
417 |
coroutine. Higher priority coroutines get run before lower priority |
418 |
coroutines. Priorities are small signed integers (currently -4 .. +3), |
419 |
that you can refer to using PRIO_xxx constants (use the import tag :prio |
420 |
to get then): |
421 |
|
422 |
PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
423 |
3 > 1 > 0 > -1 > -3 > -4 |
424 |
|
425 |
# set priority to HIGH |
426 |
current->prio(PRIO_HIGH); |
427 |
|
428 |
The idle coroutine ($Coro::idle) always has a lower priority than any |
429 |
existing coroutine. |
430 |
|
431 |
Changing the priority of the current coroutine will take effect immediately, |
432 |
but changing the priority of coroutines in the ready queue (but not |
433 |
running) will only take effect after the next schedule (of that |
434 |
coroutine). This is a bug that will be fixed in some future version. |
435 |
|
436 |
=item $newprio = $coroutine->nice ($change) |
437 |
|
438 |
Similar to C<prio>, but subtract the given value from the priority (i.e. |
439 |
higher values mean lower priority, just as in unix). |
440 |
|
441 |
=item $olddesc = $coroutine->desc ($newdesc) |
442 |
|
443 |
Sets (or gets in case the argument is missing) the description for this |
444 |
coroutine. This is just a free-form string you can associate with a coroutine. |
445 |
|
446 |
=cut |
447 |
|
448 |
sub desc { |
449 |
my $old = $_[0]{desc}; |
450 |
$_[0]{desc} = $_[1] if @_ > 1; |
451 |
$old; |
452 |
} |
453 |
|
454 |
=back |
455 |
|
456 |
=head2 GLOBAL FUNCTIONS |
457 |
|
458 |
=over 4 |
459 |
|
460 |
=item Coro::nready |
461 |
|
462 |
Returns the number of coroutines that are currently in the ready state, |
463 |
i.e. that can be swicthed to. The value C<0> means that the only runnable |
464 |
coroutine is the currently running one, so C<cede> would have no effect, |
465 |
and C<schedule> would cause a deadlock unless there is an idle handler |
466 |
that wakes up some coroutines. |
467 |
|
468 |
=item my $guard = Coro::guard { ... } |
469 |
|
470 |
This creates and returns a guard object. Nothing happens until the objetc |
471 |
gets destroyed, in which case the codeblock given as argument will be |
472 |
executed. This is useful to free locks or other resources in case of a |
473 |
runtime error or when the coroutine gets canceled, as in both cases the |
474 |
guard block will be executed. The guard object supports only one method, |
475 |
C<< ->cancel >>, which will keep the codeblock from being executed. |
476 |
|
477 |
Example: set some flag and clear it again when the coroutine gets canceled |
478 |
or the function returns: |
479 |
|
480 |
sub do_something { |
481 |
my $guard = Coro::guard { $busy = 0 }; |
482 |
$busy = 1; |
483 |
|
484 |
# do something that requires $busy to be true |
485 |
} |
486 |
|
487 |
=cut |
488 |
|
489 |
sub guard(&) { |
490 |
bless \(my $cb = $_[0]), "Coro::guard" |
491 |
} |
492 |
|
493 |
sub Coro::guard::cancel { |
494 |
${$_[0]} = sub { }; |
495 |
} |
496 |
|
497 |
sub Coro::guard::DESTROY { |
498 |
${$_[0]}->(); |
499 |
} |
500 |
|
501 |
|
502 |
=item unblock_sub { ... } |
503 |
|
504 |
This utility function takes a BLOCK or code reference and "unblocks" it, |
505 |
returning the new coderef. This means that the new coderef will return |
506 |
immediately without blocking, returning nothing, while the original code |
507 |
ref will be called (with parameters) from within its own coroutine. |
508 |
|
509 |
The reason this fucntion exists is that many event libraries (such as the |
510 |
venerable L<Event|Event> module) are not coroutine-safe (a weaker form |
511 |
of thread-safety). This means you must not block within event callbacks, |
512 |
otherwise you might suffer from crashes or worse. |
513 |
|
514 |
This function allows your callbacks to block by executing them in another |
515 |
coroutine where it is safe to block. One example where blocking is handy |
516 |
is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
517 |
disk. |
518 |
|
519 |
In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
520 |
creating event callbacks that want to block. |
521 |
|
522 |
=cut |
523 |
|
524 |
our @unblock_queue; |
525 |
|
526 |
# we create a special coro because we want to cede, |
527 |
# to reduce pressure on the coro pool (because most callbacks |
528 |
# return immediately and can be reused) and because we cannot cede |
529 |
# inside an event callback. |
530 |
our $unblock_scheduler = async { |
531 |
while () { |
532 |
while (my $cb = pop @unblock_queue) { |
533 |
# this is an inlined copy of async_pool |
534 |
my $coro = (pop @pool or new Coro \&pool_handler); |
535 |
|
536 |
$coro->{_invoke} = $cb; |
537 |
$coro->ready; |
538 |
cede; # for short-lived callbacks, this reduces pressure on the coro pool |
539 |
} |
540 |
schedule; # sleep well |
541 |
} |
542 |
}; |
543 |
|
544 |
sub unblock_sub(&) { |
545 |
my $cb = shift; |
546 |
|
547 |
sub { |
548 |
unshift @unblock_queue, [$cb, @_]; |
549 |
$unblock_scheduler->ready; |
550 |
} |
551 |
} |
552 |
|
553 |
=back |
554 |
|
555 |
=cut |
556 |
|
557 |
1; |
558 |
|
559 |
=head1 BUGS/LIMITATIONS |
560 |
|
561 |
- you must make very sure that no coro is still active on global |
562 |
destruction. very bad things might happen otherwise (usually segfaults). |
563 |
|
564 |
- this module is not thread-safe. You should only ever use this module |
565 |
from the same thread (this requirement might be losened in the future |
566 |
to allow per-thread schedulers, but Coro::State does not yet allow |
567 |
this). |
568 |
|
569 |
=head1 SEE ALSO |
570 |
|
571 |
Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>. |
572 |
|
573 |
Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. |
574 |
|
575 |
Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>. |
576 |
|
577 |
Embedding: L<Coro:MakeMaker> |
578 |
|
579 |
=head1 AUTHOR |
580 |
|
581 |
Marc Lehmann <schmorp@schmorp.de> |
582 |
http://home.schmorp.de/ |
583 |
|
584 |
=cut |
585 |
|