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 |
print "2\n"; |
12 |
cede; # yield back to main |
13 |
print "4\n"; |
14 |
}; |
15 |
print "1\n"; |
16 |
cede; # yield to coroutine |
17 |
print "3\n"; |
18 |
cede; # and again |
19 |
|
20 |
# use locking |
21 |
my $lock = new Coro::Semaphore; |
22 |
my $locked; |
23 |
|
24 |
$lock->down; |
25 |
$locked = 1; |
26 |
$lock->up; |
27 |
|
28 |
=head1 DESCRIPTION |
29 |
|
30 |
This module collection manages coroutines. Coroutines are similar |
31 |
to threads but don't run in parallel at the same time even on SMP |
32 |
machines. The specific flavor of coroutine used in this module also |
33 |
guarantees you that it will not switch between coroutines unless |
34 |
necessary, at easily-identified points in your program, so locking and |
35 |
parallel access are rarely an issue, making coroutine programming much |
36 |
safer than threads programming. |
37 |
|
38 |
(Perl, however, does not natively support real threads but instead does a |
39 |
very slow and memory-intensive emulation of processes using threads. This |
40 |
is a performance win on Windows machines, and a loss everywhere else). |
41 |
|
42 |
In this module, coroutines are defined as "callchain + lexical variables + |
43 |
@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain, |
44 |
its own set of lexicals and its own set of perls most important global |
45 |
variables (see L<Coro::State> for more configuration). |
46 |
|
47 |
=cut |
48 |
|
49 |
package Coro; |
50 |
|
51 |
use strict; |
52 |
no warnings "uninitialized"; |
53 |
|
54 |
use Coro::State; |
55 |
|
56 |
use base qw(Coro::State Exporter); |
57 |
|
58 |
our $idle; # idle handler |
59 |
our $main; # main coroutine |
60 |
our $current; # current coroutine |
61 |
|
62 |
our $VERSION = '4.1'; |
63 |
|
64 |
our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); |
65 |
our %EXPORT_TAGS = ( |
66 |
prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
67 |
); |
68 |
our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
69 |
|
70 |
{ |
71 |
my @async; |
72 |
my $init; |
73 |
|
74 |
# this way of handling attributes simply is NOT scalable ;() |
75 |
sub import { |
76 |
no strict 'refs'; |
77 |
|
78 |
Coro->export_to_level (1, @_); |
79 |
|
80 |
my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; |
81 |
*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { |
82 |
my ($package, $ref) = (shift, shift); |
83 |
my @attrs; |
84 |
for (@_) { |
85 |
if ($_ eq "Coro") { |
86 |
push @async, $ref; |
87 |
unless ($init++) { |
88 |
eval q{ |
89 |
sub INIT { |
90 |
&async(pop @async) while @async; |
91 |
} |
92 |
}; |
93 |
} |
94 |
} else { |
95 |
push @attrs, $_; |
96 |
} |
97 |
} |
98 |
return $old ? $old->($package, $ref, @attrs) : @attrs; |
99 |
}; |
100 |
} |
101 |
|
102 |
} |
103 |
|
104 |
=over 4 |
105 |
|
106 |
=item $main |
107 |
|
108 |
This coroutine represents the main program. |
109 |
|
110 |
=cut |
111 |
|
112 |
$main = new Coro; |
113 |
|
114 |
=item $current (or as function: current) |
115 |
|
116 |
The current coroutine (the last coroutine switched to). The initial value |
117 |
is C<$main> (of course). |
118 |
|
119 |
This variable is B<strictly> I<read-only>. It is provided for performance |
120 |
reasons. If performance is not essential you are encouraged to use the |
121 |
C<Coro::current> function instead. |
122 |
|
123 |
=cut |
124 |
|
125 |
$main->{desc} = "[main::]"; |
126 |
|
127 |
# maybe some other module used Coro::Specific before... |
128 |
$main->{_specific} = $current->{_specific} |
129 |
if $current; |
130 |
|
131 |
_set_current $main; |
132 |
|
133 |
sub current() { $current } |
134 |
|
135 |
=item $idle |
136 |
|
137 |
A callback that is called whenever the scheduler finds no ready coroutines |
138 |
to run. The default implementation prints "FATAL: deadlock detected" and |
139 |
exits, because the program has no other way to continue. |
140 |
|
141 |
This hook is overwritten by modules such as C<Coro::Timer> and |
142 |
C<Coro::Event> to wait on an external event that hopefully wake up a |
143 |
coroutine so the scheduler can run it. |
144 |
|
145 |
Please note that if your callback recursively invokes perl (e.g. for event |
146 |
handlers), then it must be prepared to be called recursively itself. |
147 |
|
148 |
=cut |
149 |
|
150 |
$idle = sub { |
151 |
require Carp; |
152 |
Carp::croak ("FATAL: deadlock detected"); |
153 |
}; |
154 |
|
155 |
sub _cancel { |
156 |
my ($self) = @_; |
157 |
|
158 |
# free coroutine data and mark as destructed |
159 |
$self->_destroy |
160 |
or return; |
161 |
|
162 |
# call all destruction callbacks |
163 |
$_->(@{$self->{_status}}) |
164 |
for @{(delete $self->{_on_destroy}) || []}; |
165 |
} |
166 |
|
167 |
# this coroutine is necessary because a coroutine |
168 |
# cannot destroy itself. |
169 |
my @destroy; |
170 |
my $manager; |
171 |
|
172 |
$manager = new Coro sub { |
173 |
while () { |
174 |
(shift @destroy)->_cancel |
175 |
while @destroy; |
176 |
|
177 |
&schedule; |
178 |
} |
179 |
}; |
180 |
$manager->desc ("[coro manager]"); |
181 |
$manager->prio (PRIO_MAX); |
182 |
|
183 |
# static methods. not really. |
184 |
|
185 |
=back |
186 |
|
187 |
=head2 STATIC METHODS |
188 |
|
189 |
Static methods are actually functions that operate on the current coroutine only. |
190 |
|
191 |
=over 4 |
192 |
|
193 |
=item async { ... } [@args...] |
194 |
|
195 |
Create a new asynchronous coroutine and return it's coroutine object |
196 |
(usually unused). When the sub returns the new coroutine is automatically |
197 |
terminated. |
198 |
|
199 |
See the C<Coro::State::new> constructor for info about the coroutine |
200 |
environment in which coroutines run. |
201 |
|
202 |
Calling C<exit> in a coroutine will do the same as calling exit outside |
203 |
the coroutine. Likewise, when the coroutine dies, the program will exit, |
204 |
just as it would in the main program. |
205 |
|
206 |
# create a new coroutine that just prints its arguments |
207 |
async { |
208 |
print "@_\n"; |
209 |
} 1,2,3,4; |
210 |
|
211 |
=cut |
212 |
|
213 |
sub async(&@) { |
214 |
my $coro = new Coro @_; |
215 |
$coro->ready; |
216 |
$coro |
217 |
} |
218 |
|
219 |
=item async_pool { ... } [@args...] |
220 |
|
221 |
Similar to C<async>, but uses a coroutine pool, so you should not call |
222 |
terminate or join (although you are allowed to), and you get a coroutine |
223 |
that might have executed other code already (which can be good or bad :). |
224 |
|
225 |
Also, the block is executed in an C<eval> context and a warning will be |
226 |
issued in case of an exception instead of terminating the program, as |
227 |
C<async> does. As the coroutine is being reused, stuff like C<on_destroy> |
228 |
will not work in the expected way, unless you call terminate or cancel, |
229 |
which somehow defeats the purpose of pooling. |
230 |
|
231 |
The priority will be reset to C<0> after each job, tracing will be |
232 |
disabled, the description will be reset and the default output filehandle |
233 |
gets restored, so you can change alkl these. Otherwise the coroutine will |
234 |
be re-used "as-is": most notably if you change other per-coroutine global |
235 |
stuff such as C<$/> you need to revert that change, which is most simply |
236 |
done by using local as in C< local $/ >. |
237 |
|
238 |
The pool size is limited to 8 idle coroutines (this can be adjusted by |
239 |
changing $Coro::POOL_SIZE), and there can be as many non-idle coros as |
240 |
required. |
241 |
|
242 |
If you are concerned about pooled coroutines growing a lot because a |
243 |
single C<async_pool> used a lot of stackspace you can e.g. C<async_pool |
244 |
{ terminate }> once per second or so to slowly replenish the pool. In |
245 |
addition to that, when the stacks used by a handler grows larger than 16kb |
246 |
(adjustable with $Coro::POOL_RSS) it will also exit. |
247 |
|
248 |
=cut |
249 |
|
250 |
our $POOL_SIZE = 8; |
251 |
our $POOL_RSS = 16 * 1024; |
252 |
our @async_pool; |
253 |
|
254 |
sub pool_handler { |
255 |
my $cb; |
256 |
|
257 |
while () { |
258 |
eval { |
259 |
while () { |
260 |
_pool_1 $cb; |
261 |
&$cb; |
262 |
_pool_2 $cb; |
263 |
&schedule; |
264 |
} |
265 |
}; |
266 |
|
267 |
last if $@ eq "\3async_pool terminate\2\n"; |
268 |
warn $@ if $@; |
269 |
} |
270 |
} |
271 |
|
272 |
sub async_pool(&@) { |
273 |
# this is also inlined into the unlock_scheduler |
274 |
my $coro = (pop @async_pool) || new Coro \&pool_handler; |
275 |
|
276 |
$coro->{_invoke} = [@_]; |
277 |
$coro->ready; |
278 |
|
279 |
$coro |
280 |
} |
281 |
|
282 |
=item schedule |
283 |
|
284 |
Calls the scheduler. Please note that the current coroutine will not be put |
285 |
into the ready queue, so calling this function usually means you will |
286 |
never be called again unless something else (e.g. an event handler) calls |
287 |
ready. |
288 |
|
289 |
The canonical way to wait on external events is this: |
290 |
|
291 |
{ |
292 |
# remember current coroutine |
293 |
my $current = $Coro::current; |
294 |
|
295 |
# register a hypothetical event handler |
296 |
on_event_invoke sub { |
297 |
# wake up sleeping coroutine |
298 |
$current->ready; |
299 |
undef $current; |
300 |
}; |
301 |
|
302 |
# call schedule until event occurred. |
303 |
# in case we are woken up for other reasons |
304 |
# (current still defined), loop. |
305 |
Coro::schedule while $current; |
306 |
} |
307 |
|
308 |
=item cede |
309 |
|
310 |
"Cede" to other coroutines. This function puts the current coroutine into the |
311 |
ready queue and calls C<schedule>, which has the effect of giving up the |
312 |
current "timeslice" to other coroutines of the same or higher priority. |
313 |
|
314 |
Returns true if at least one coroutine switch has happened. |
315 |
|
316 |
=item Coro::cede_notself |
317 |
|
318 |
Works like cede, but is not exported by default and will cede to any |
319 |
coroutine, regardless of priority, once. |
320 |
|
321 |
Returns true if at least one coroutine switch has happened. |
322 |
|
323 |
=item terminate [arg...] |
324 |
|
325 |
Terminates the current coroutine with the given status values (see L<cancel>). |
326 |
|
327 |
=item killall |
328 |
|
329 |
Kills/terminates/cancels all coroutines except the currently running |
330 |
one. This is useful after a fork, either in the child or the parent, as |
331 |
usually only one of them should inherit the running coroutines. |
332 |
|
333 |
=cut |
334 |
|
335 |
sub terminate { |
336 |
$current->cancel (@_); |
337 |
} |
338 |
|
339 |
sub killall { |
340 |
for (Coro::State::list) { |
341 |
$_->cancel |
342 |
if $_ != $current && UNIVERSAL::isa $_, "Coro"; |
343 |
} |
344 |
} |
345 |
|
346 |
=back |
347 |
|
348 |
# dynamic methods |
349 |
|
350 |
=head2 COROUTINE METHODS |
351 |
|
352 |
These are the methods you can call on coroutine objects. |
353 |
|
354 |
=over 4 |
355 |
|
356 |
=item new Coro \&sub [, @args...] |
357 |
|
358 |
Create a new coroutine and return it. When the sub returns the coroutine |
359 |
automatically terminates as if C<terminate> with the returned values were |
360 |
called. To make the coroutine run you must first put it into the ready queue |
361 |
by calling the ready method. |
362 |
|
363 |
See C<async> and C<Coro::State::new> for additional info about the |
364 |
coroutine environment. |
365 |
|
366 |
=cut |
367 |
|
368 |
sub _run_coro { |
369 |
terminate &{+shift}; |
370 |
} |
371 |
|
372 |
sub new { |
373 |
my $class = shift; |
374 |
|
375 |
$class->SUPER::new (\&_run_coro, @_) |
376 |
} |
377 |
|
378 |
=item $success = $coroutine->ready |
379 |
|
380 |
Put the given coroutine into the ready queue (according to it's priority) |
381 |
and return true. If the coroutine is already in the ready queue, do nothing |
382 |
and return false. |
383 |
|
384 |
=item $is_ready = $coroutine->is_ready |
385 |
|
386 |
Return wether the coroutine is currently the ready queue or not, |
387 |
|
388 |
=item $coroutine->cancel (arg...) |
389 |
|
390 |
Terminates the given coroutine and makes it return the given arguments as |
391 |
status (default: the empty list). Never returns if the coroutine is the |
392 |
current coroutine. |
393 |
|
394 |
=cut |
395 |
|
396 |
sub cancel { |
397 |
my $self = shift; |
398 |
$self->{_status} = [@_]; |
399 |
|
400 |
if ($current == $self) { |
401 |
push @destroy, $self; |
402 |
$manager->ready; |
403 |
&schedule while 1; |
404 |
} else { |
405 |
$self->_cancel; |
406 |
} |
407 |
} |
408 |
|
409 |
=item $coroutine->join |
410 |
|
411 |
Wait until the coroutine terminates and return any values given to the |
412 |
C<terminate> or C<cancel> functions. C<join> can be called concurrently |
413 |
from multiple coroutines. |
414 |
|
415 |
=cut |
416 |
|
417 |
sub join { |
418 |
my $self = shift; |
419 |
|
420 |
unless ($self->{_status}) { |
421 |
my $current = $current; |
422 |
|
423 |
push @{$self->{_on_destroy}}, sub { |
424 |
$current->ready; |
425 |
undef $current; |
426 |
}; |
427 |
|
428 |
&schedule while $current; |
429 |
} |
430 |
|
431 |
wantarray ? @{$self->{_status}} : $self->{_status}[0]; |
432 |
} |
433 |
|
434 |
=item $coroutine->on_destroy (\&cb) |
435 |
|
436 |
Registers a callback that is called when this coroutine gets destroyed, |
437 |
but before it is joined. The callback gets passed the terminate arguments, |
438 |
if any. |
439 |
|
440 |
=cut |
441 |
|
442 |
sub on_destroy { |
443 |
my ($self, $cb) = @_; |
444 |
|
445 |
push @{ $self->{_on_destroy} }, $cb; |
446 |
} |
447 |
|
448 |
=item $oldprio = $coroutine->prio ($newprio) |
449 |
|
450 |
Sets (or gets, if the argument is missing) the priority of the |
451 |
coroutine. Higher priority coroutines get run before lower priority |
452 |
coroutines. Priorities are small signed integers (currently -4 .. +3), |
453 |
that you can refer to using PRIO_xxx constants (use the import tag :prio |
454 |
to get then): |
455 |
|
456 |
PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
457 |
3 > 1 > 0 > -1 > -3 > -4 |
458 |
|
459 |
# set priority to HIGH |
460 |
current->prio(PRIO_HIGH); |
461 |
|
462 |
The idle coroutine ($Coro::idle) always has a lower priority than any |
463 |
existing coroutine. |
464 |
|
465 |
Changing the priority of the current coroutine will take effect immediately, |
466 |
but changing the priority of coroutines in the ready queue (but not |
467 |
running) will only take effect after the next schedule (of that |
468 |
coroutine). This is a bug that will be fixed in some future version. |
469 |
|
470 |
=item $newprio = $coroutine->nice ($change) |
471 |
|
472 |
Similar to C<prio>, but subtract the given value from the priority (i.e. |
473 |
higher values mean lower priority, just as in unix). |
474 |
|
475 |
=item $olddesc = $coroutine->desc ($newdesc) |
476 |
|
477 |
Sets (or gets in case the argument is missing) the description for this |
478 |
coroutine. This is just a free-form string you can associate with a coroutine. |
479 |
|
480 |
This method simply sets the C<< $coroutine->{desc} >> member to the given string. You |
481 |
can modify this member directly if you wish. |
482 |
|
483 |
=item $coroutine->throw ([$scalar]) |
484 |
|
485 |
If C<$throw> is specified and defined, it will be thrown as an exception |
486 |
inside the coroutine at the next convinient point in time (usually after |
487 |
it gains control at the next schedule/transfer/cede). Otherwise clears the |
488 |
exception object. |
489 |
|
490 |
The exception object will be thrown "as is" with the specified scalar in |
491 |
C<$@>, i.e. if it is a string, no line number or newline will be appended |
492 |
(unlike with C<die>). |
493 |
|
494 |
This can be used as a softer means than C<cancel> to ask a coroutine to |
495 |
end itself, although there is no guarentee that the exception will lead to |
496 |
termination, and if the exception isn't caught it might well end the whole |
497 |
program. |
498 |
|
499 |
=cut |
500 |
|
501 |
sub desc { |
502 |
my $old = $_[0]{desc}; |
503 |
$_[0]{desc} = $_[1] if @_ > 1; |
504 |
$old; |
505 |
} |
506 |
|
507 |
=back |
508 |
|
509 |
=head2 GLOBAL FUNCTIONS |
510 |
|
511 |
=over 4 |
512 |
|
513 |
=item Coro::nready |
514 |
|
515 |
Returns the number of coroutines that are currently in the ready state, |
516 |
i.e. that can be switched to. The value C<0> means that the only runnable |
517 |
coroutine is the currently running one, so C<cede> would have no effect, |
518 |
and C<schedule> would cause a deadlock unless there is an idle handler |
519 |
that wakes up some coroutines. |
520 |
|
521 |
=item my $guard = Coro::guard { ... } |
522 |
|
523 |
This creates and returns a guard object. Nothing happens until the object |
524 |
gets destroyed, in which case the codeblock given as argument will be |
525 |
executed. This is useful to free locks or other resources in case of a |
526 |
runtime error or when the coroutine gets canceled, as in both cases the |
527 |
guard block will be executed. The guard object supports only one method, |
528 |
C<< ->cancel >>, which will keep the codeblock from being executed. |
529 |
|
530 |
Example: set some flag and clear it again when the coroutine gets canceled |
531 |
or the function returns: |
532 |
|
533 |
sub do_something { |
534 |
my $guard = Coro::guard { $busy = 0 }; |
535 |
$busy = 1; |
536 |
|
537 |
# do something that requires $busy to be true |
538 |
} |
539 |
|
540 |
=cut |
541 |
|
542 |
sub guard(&) { |
543 |
bless \(my $cb = $_[0]), "Coro::guard" |
544 |
} |
545 |
|
546 |
sub Coro::guard::cancel { |
547 |
${$_[0]} = sub { }; |
548 |
} |
549 |
|
550 |
sub Coro::guard::DESTROY { |
551 |
${$_[0]}->(); |
552 |
} |
553 |
|
554 |
|
555 |
=item unblock_sub { ... } |
556 |
|
557 |
This utility function takes a BLOCK or code reference and "unblocks" it, |
558 |
returning the new coderef. This means that the new coderef will return |
559 |
immediately without blocking, returning nothing, while the original code |
560 |
ref will be called (with parameters) from within its own coroutine. |
561 |
|
562 |
The reason this function exists is that many event libraries (such as the |
563 |
venerable L<Event|Event> module) are not coroutine-safe (a weaker form |
564 |
of thread-safety). This means you must not block within event callbacks, |
565 |
otherwise you might suffer from crashes or worse. |
566 |
|
567 |
This function allows your callbacks to block by executing them in another |
568 |
coroutine where it is safe to block. One example where blocking is handy |
569 |
is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
570 |
disk. |
571 |
|
572 |
In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
573 |
creating event callbacks that want to block. |
574 |
|
575 |
=cut |
576 |
|
577 |
our @unblock_queue; |
578 |
|
579 |
# we create a special coro because we want to cede, |
580 |
# to reduce pressure on the coro pool (because most callbacks |
581 |
# return immediately and can be reused) and because we cannot cede |
582 |
# inside an event callback. |
583 |
our $unblock_scheduler = new Coro sub { |
584 |
while () { |
585 |
while (my $cb = pop @unblock_queue) { |
586 |
# this is an inlined copy of async_pool |
587 |
my $coro = (pop @async_pool) || new Coro \&pool_handler; |
588 |
|
589 |
$coro->{_invoke} = $cb; |
590 |
$coro->ready; |
591 |
cede; # for short-lived callbacks, this reduces pressure on the coro pool |
592 |
} |
593 |
schedule; # sleep well |
594 |
} |
595 |
}; |
596 |
$unblock_scheduler->desc ("[unblock_sub scheduler]"); |
597 |
|
598 |
sub unblock_sub(&) { |
599 |
my $cb = shift; |
600 |
|
601 |
sub { |
602 |
unshift @unblock_queue, [$cb, @_]; |
603 |
$unblock_scheduler->ready; |
604 |
} |
605 |
} |
606 |
|
607 |
=back |
608 |
|
609 |
=cut |
610 |
|
611 |
1; |
612 |
|
613 |
=head1 BUGS/LIMITATIONS |
614 |
|
615 |
- you must make very sure that no coro is still active on global |
616 |
destruction. very bad things might happen otherwise (usually segfaults). |
617 |
|
618 |
- this module is not thread-safe. You should only ever use this module |
619 |
from the same thread (this requirement might be loosened in the future |
620 |
to allow per-thread schedulers, but Coro::State does not yet allow |
621 |
this). |
622 |
|
623 |
=head1 SEE ALSO |
624 |
|
625 |
Lower level Configuration, Coroutine Environment: L<Coro::State>. |
626 |
|
627 |
Debugging: L<Coro::Debug>. |
628 |
|
629 |
Support/Utility: L<Coro::Specific>, L<Coro::Util>. |
630 |
|
631 |
Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. |
632 |
|
633 |
Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>. |
634 |
|
635 |
Compatibility: L<Coro::LWP>, L<Coro::Storable>, L<Coro::Select>. |
636 |
|
637 |
Embedding: L<Coro:MakeMaker>. |
638 |
|
639 |
=head1 AUTHOR |
640 |
|
641 |
Marc Lehmann <schmorp@schmorp.de> |
642 |
http://home.schmorp.de/ |
643 |
|
644 |
=cut |
645 |
|