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Revision 1.22 by root, Mon Jul 23 02:14:19 2001 UTC vs.
Revision 1.137 by root, Wed Sep 26 19:26:48 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), that is, a coroutine has it's own callchain, it's 36@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
30own set of lexicals and it's own set of perl's most important global 37its own set of lexicals and its own set of perls most important global
31variables. 38variables.
32 39
33WARNING: When using this module, make sure that, at program end, no
34coroutines are still running OR just call exit before falling off the
35end. The reason for this is that some coroutine of yours might have called
36into a C function, and falling off the end of main:: results in returning
37to that C function instead if to the main C interpreter.
38
39WARNING: Unless you really know what you are doing, do NOT do context
40switches inside callbacks from the XS level. The reason for this is
41similar to the reason above: A callback calls a perl function, this
42perl function does a context switch, some other callback is called, the
43original function returns from it - to what? To the wrong XS function,
44with totally different return values. Unfortunately, this includes
45callbacks done by perl itself (tie'd variables!).
46
47The only workaround for this is to do coroutines on C level.
48
49=cut 40=cut
50 41
51package Coro; 42package Coro;
52 43
44use strict;
45no warnings "uninitialized";
46
53use Coro::State; 47use Coro::State;
54 48
55use base Exporter; 49use base qw(Coro::State Exporter);
56 50
57$VERSION = 0.10; 51our $idle; # idle handler
52our $main; # main coroutine
53our $current; # current coroutine
58 54
55our $VERSION = '3.7';
56
59@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
60@EXPORT_OK = qw($current); 58our %EXPORT_TAGS = (
59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
60);
61our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
61 62
62{ 63{
63 my @async; 64 my @async;
65 my $init;
64 66
65 # this way of handling attributes simply is NOT scalable ;() 67 # this way of handling attributes simply is NOT scalable ;()
66 sub import { 68 sub import {
69 no strict 'refs';
70
67 Coro->export_to_level(1, @_); 71 Coro->export_to_level (1, @_);
72
68 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; 73 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
69 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { 74 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
70 my ($package, $ref) = (shift, shift); 75 my ($package, $ref) = (shift, shift);
71 my @attrs; 76 my @attrs;
72 for (@_) { 77 for (@_) {
73 if ($_ eq "Coro") { 78 if ($_ eq "Coro") {
74 push @async, $ref; 79 push @async, $ref;
80 unless ($init++) {
81 eval q{
82 sub INIT {
83 &async(pop @async) while @async;
84 }
85 };
86 }
75 } else { 87 } else {
76 push @attrs, $_; 88 push @attrs, $_;
77 } 89 }
78 } 90 }
79 return $old ? $old->($package, $ref, @attrs) : @attrs; 91 return $old ? $old->($package, $ref, @attrs) : @attrs;
80 }; 92 };
81 } 93 }
82 94
83 sub INIT {
84 &async(pop @async) while @async;
85 }
86} 95}
96
97=over 4
87 98
88=item $main 99=item $main
89 100
90This coroutine represents the main program. 101This coroutine represents the main program.
91 102
92=cut 103=cut
93 104
94our $main = new Coro; 105$main = new Coro;
95 106
96=item $current (or as function: current) 107=item $current (or as function: current)
97 108
98The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). 109The current coroutine (the last coroutine switched to). The initial value
110is C<$main> (of course).
99 111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essential you are encouraged to use the
114C<Coro::current> function instead.
115
100=cut 116=cut
117
118$main->{desc} = "[main::]";
101 119
102# maybe some other module used Coro::Specific before... 120# maybe some other module used Coro::Specific before...
103if ($current) {
104 $main->{specific} = $current->{specific}; 121$main->{specific} = $current->{specific}
105} 122 if $current;
106 123
107our $current = $main; 124_set_current $main;
108 125
109sub current() { $current } 126sub current() { $current }
110 127
111=item $idle 128=item $idle
112 129
113The coroutine to switch to when no other coroutine is running. The default 130A callback that is called whenever the scheduler finds no ready coroutines
114implementation 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.
115 133
116=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.
117 137
118# should be done using priorities :( 138Please note that if your callback recursively invokes perl (e.g. for event
119our $idle = new Coro sub { 139handlers), then it must be prepared to be called recursively.
120 print STDERR "FATAL: deadlock detected\n"; 140
121 exit(51); 141=cut
142
143$idle = sub {
144 require Carp;
145 Carp::croak ("FATAL: deadlock detected");
122}; 146};
123 147
124# we really need priorities... 148sub _cancel {
125my @ready; # the ready queue. hehe, rather broken ;) 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 {
161 $current->{_trace_cb}->();
162}
163
164# this coroutine is necessary because a coroutine
165# cannot destroy itself.
166my @destroy;
167my $manager;
168
169$manager = new Coro sub {
170 while () {
171 (shift @destroy)->_cancel
172 while @destroy;
173
174 &schedule;
175 }
176};
177$manager->desc ("[coro manager]");
178$manager->prio (PRIO_MAX);
126 179
127# static methods. not really. 180# static methods. not really.
128 181
182=back
183
129=head2 STATIC METHODS 184=head2 STATIC METHODS
130 185
131Static methods are actually functions that operate on the current process only. 186Static methods are actually functions that operate on the current coroutine only.
132 187
133=over 4 188=over 4
134 189
135=item async { ... } [@args...] 190=item async { ... } [@args...]
136 191
137Create a new asynchronous process and return it's process object 192Create a new asynchronous coroutine and return it's coroutine object
138(usually unused). When the sub returns the new process is automatically 193(usually unused). When the sub returns the new coroutine is automatically
139terminated. 194terminated.
195
196Calling C<exit> in a coroutine will do the same as calling exit outside
197the coroutine. Likewise, when the coroutine dies, the program will exit,
198just as it would in the main program.
140 199
141 # create a new coroutine that just prints its arguments 200 # create a new coroutine that just prints its arguments
142 async { 201 async {
143 print "@_\n"; 202 print "@_\n";
144 } 1,2,3,4; 203 } 1,2,3,4;
145 204
146The coderef you submit MUST NOT be a closure that refers to variables
147in an outer scope. This does NOT work. Pass arguments into it instead.
148
149=cut 205=cut
150 206
151sub async(&@) { 207sub async(&@) {
152 my $pid = new Coro @_; 208 my $coro = new Coro @_;
153 $pid->ready; 209 $coro->ready;
154 $pid; 210 $coro
211}
212
213=item async_pool { ... } [@args...]
214
215Similar to C<async>, but uses a coroutine pool, so you should not call
216terminate or join (although you are allowed to), and you get a coroutine
217that might have executed other code already (which can be good or bad :).
218
219Also, the block is executed in an C<eval> context and a warning will be
220issued in case of an exception instead of terminating the program, as
221C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
222will not work in the expected way, unless you call terminate or cancel,
223which somehow defeats the purpose of pooling.
224
225The priority will be reset to C<0> after each job, otherwise the coroutine
226will be re-used "as-is".
227
228The pool size is limited to 8 idle coroutines (this can be adjusted by
229changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
230required.
231
232If you are concerned about pooled coroutines growing a lot because a
233single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
234{ terminate }> once per second or so to slowly replenish the pool. In
235addition to that, when the stacks used by a handler grows larger than 16kb
236(adjustable with $Coro::POOL_RSS) it will also exit.
237
238=cut
239
240our $POOL_SIZE = 8;
241our $POOL_RSS = 16 * 1024;
242our @async_pool;
243
244sub pool_handler {
245 my $cb;
246
247 while () {
248 eval {
249 while () {
250 _pool_1 $cb;
251 &$cb;
252 _pool_2 $cb;
253 &schedule;
254 }
255 };
256
257 last if $@ eq "\3terminate\2\n";
258 warn $@ if $@;
259 }
260}
261
262sub async_pool(&@) {
263 # this is also inlined into the unlock_scheduler
264 my $coro = (pop @async_pool) || new Coro \&pool_handler;
265
266 $coro->{_invoke} = [@_];
267 $coro->ready;
268
269 $coro
155} 270}
156 271
157=item schedule 272=item schedule
158 273
159Calls the scheduler. Please note that the current process will not be put 274Calls the scheduler. Please note that the current coroutine will not be put
160into the ready queue, so calling this function usually means you will 275into the ready queue, so calling this function usually means you will
161never be called again. 276never be called again unless something else (e.g. an event handler) calls
277ready.
162 278
163=cut 279The canonical way to wait on external events is this:
164 280
165my $prev; 281 {
282 # remember current coroutine
283 my $current = $Coro::current;
166 284
167sub schedule { 285 # register a hypothetical event handler
168 # should be done using priorities :( 286 on_event_invoke sub {
169 ($prev, $current) = ($current, shift @ready || $idle); 287 # wake up sleeping coroutine
170 Coro::State::transfer($prev, $current); 288 $current->ready;
171} 289 undef $current;
290 };
291
292 # call schedule until event occurred.
293 # in case we are woken up for other reasons
294 # (current still defined), loop.
295 Coro::schedule while $current;
296 }
172 297
173=item cede 298=item cede
174 299
175"Cede" to other processes. This function puts the current process into the 300"Cede" to other coroutines. This function puts the current coroutine into the
176ready queue and calls C<schedule>, which has the effect of giving up the 301ready queue and calls C<schedule>, which has the effect of giving up the
177current "timeslice" to other coroutines of the same or higher priority. 302current "timeslice" to other coroutines of the same or higher priority.
178 303
179=cut 304Returns true if at least one coroutine switch has happened.
180 305
181sub cede { 306=item Coro::cede_notself
182 $current->ready;
183 &schedule;
184}
185 307
308Works like cede, but is not exported by default and will cede to any
309coroutine, regardless of priority, once.
310
311Returns true if at least one coroutine switch has happened.
312
186=item terminate 313=item terminate [arg...]
187 314
188Terminates the current process. 315Terminates the current coroutine with the given status values (see L<cancel>).
189
190Future versions of this function will allow result arguments.
191 316
192=cut 317=cut
193 318
194sub terminate { 319sub terminate {
195 my $self = $current; 320 $current->cancel (@_);
196 $self->{_results} = [@_];
197 $current = shift @ready || $idle;
198 Coro::State::transfer(delete $self->{_coro_state}, $current);
199 # cannot return
200 die;
201} 321}
202 322
203=back 323=back
204 324
205# dynamic methods 325# dynamic methods
206 326
207=head2 PROCESS METHODS 327=head2 COROUTINE METHODS
208 328
209These are the methods you can call on process objects. 329These are the methods you can call on coroutine objects.
210 330
211=over 4 331=over 4
212 332
213=item new Coro \&sub [, @args...] 333=item new Coro \&sub [, @args...]
214 334
215Create a new process and return it. When the sub returns the process 335Create a new coroutine and return it. When the sub returns the coroutine
216automatically terminates. To start the process you must first put it into 336automatically terminates as if C<terminate> with the returned values were
337called. To make the coroutine run you must first put it into the ready queue
217the ready queue by calling the ready method. 338by calling the ready method.
218 339
219The coderef you submit MUST NOT be a closure that refers to variables 340See C<async> for additional discussion.
220in an outer scope. This does NOT work. Pass arguments into it instead.
221 341
222=cut 342=cut
223 343
224sub _newcoro { 344sub _run_coro {
225 terminate &{+shift}; 345 terminate &{+shift};
226} 346}
227 347
228sub new { 348sub new {
229 my $class = shift; 349 my $class = shift;
230 bless {
231 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
232 }, $class;
233}
234 350
235=item $process->ready 351 $class->SUPER::new (\&_run_coro, @_)
352}
236 353
237Put the current process into the ready queue. 354=item $success = $coroutine->ready
238 355
239=cut 356Put the given coroutine into the ready queue (according to it's priority)
357and return true. If the coroutine is already in the ready queue, do nothing
358and return false.
240 359
241sub ready { 360=item $is_ready = $coroutine->is_ready
242 push @ready, $_[0]; 361
362Return wether the coroutine is currently the ready queue or not,
363
364=item $coroutine->cancel (arg...)
365
366Terminates the given coroutine and makes it return the given arguments as
367status (default: the empty list). Never returns if the coroutine is the
368current coroutine.
369
370=cut
371
372sub cancel {
373 my $self = shift;
374 $self->{status} = [@_];
375
376 if ($current == $self) {
377 push @destroy, $self;
378 $manager->ready;
379 &schedule while 1;
380 } else {
381 $self->_cancel;
382 }
383}
384
385=item $coroutine->join
386
387Wait until the coroutine terminates and return any values given to the
388C<terminate> or C<cancel> functions. C<join> can be called multiple times
389from multiple coroutine.
390
391=cut
392
393sub join {
394 my $self = shift;
395
396 unless ($self->{status}) {
397 my $current = $current;
398
399 push @{$self->{destroy_cb}}, sub {
400 $current->ready;
401 undef $current;
402 };
403
404 &schedule while $current;
405 }
406
407 wantarray ? @{$self->{status}} : $self->{status}[0];
408}
409
410=item $coroutine->on_destroy (\&cb)
411
412Registers a callback that is called when this coroutine gets destroyed,
413but before it is joined. The callback gets passed the terminate arguments,
414if any.
415
416=cut
417
418sub on_destroy {
419 my ($self, $cb) = @_;
420
421 push @{ $self->{destroy_cb} }, $cb;
422}
423
424=item $oldprio = $coroutine->prio ($newprio)
425
426Sets (or gets, if the argument is missing) the priority of the
427coroutine. Higher priority coroutines get run before lower priority
428coroutines. Priorities are small signed integers (currently -4 .. +3),
429that you can refer to using PRIO_xxx constants (use the import tag :prio
430to get then):
431
432 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
433 3 > 1 > 0 > -1 > -3 > -4
434
435 # set priority to HIGH
436 current->prio(PRIO_HIGH);
437
438The idle coroutine ($Coro::idle) always has a lower priority than any
439existing coroutine.
440
441Changing the priority of the current coroutine will take effect immediately,
442but changing the priority of coroutines in the ready queue (but not
443running) will only take effect after the next schedule (of that
444coroutine). This is a bug that will be fixed in some future version.
445
446=item $newprio = $coroutine->nice ($change)
447
448Similar to C<prio>, but subtract the given value from the priority (i.e.
449higher values mean lower priority, just as in unix).
450
451=item $olddesc = $coroutine->desc ($newdesc)
452
453Sets (or gets in case the argument is missing) the description for this
454coroutine. This is just a free-form string you can associate with a coroutine.
455
456=cut
457
458sub desc {
459 my $old = $_[0]{desc};
460 $_[0]{desc} = $_[1] if @_ > 1;
461 $old;
243} 462}
244 463
245=back 464=back
246 465
466=head2 GLOBAL FUNCTIONS
467
468=over 4
469
470=item Coro::nready
471
472Returns the number of coroutines that are currently in the ready state,
473i.e. that can be switched to. The value C<0> means that the only runnable
474coroutine is the currently running one, so C<cede> would have no effect,
475and C<schedule> would cause a deadlock unless there is an idle handler
476that wakes up some coroutines.
477
478=item my $guard = Coro::guard { ... }
479
480This creates and returns a guard object. Nothing happens until the object
481gets destroyed, in which case the codeblock given as argument will be
482executed. This is useful to free locks or other resources in case of a
483runtime error or when the coroutine gets canceled, as in both cases the
484guard block will be executed. The guard object supports only one method,
485C<< ->cancel >>, which will keep the codeblock from being executed.
486
487Example: set some flag and clear it again when the coroutine gets canceled
488or the function returns:
489
490 sub do_something {
491 my $guard = Coro::guard { $busy = 0 };
492 $busy = 1;
493
494 # do something that requires $busy to be true
495 }
496
497=cut
498
499sub guard(&) {
500 bless \(my $cb = $_[0]), "Coro::guard"
501}
502
503sub Coro::guard::cancel {
504 ${$_[0]} = sub { };
505}
506
507sub Coro::guard::DESTROY {
508 ${$_[0]}->();
509}
510
511
512=item unblock_sub { ... }
513
514This utility function takes a BLOCK or code reference and "unblocks" it,
515returning the new coderef. This means that the new coderef will return
516immediately without blocking, returning nothing, while the original code
517ref will be called (with parameters) from within its own coroutine.
518
519The reason this function exists is that many event libraries (such as the
520venerable L<Event|Event> module) are not coroutine-safe (a weaker form
521of thread-safety). This means you must not block within event callbacks,
522otherwise you might suffer from crashes or worse.
523
524This function allows your callbacks to block by executing them in another
525coroutine where it is safe to block. One example where blocking is handy
526is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
527disk.
528
529In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
530creating event callbacks that want to block.
531
532=cut
533
534our @unblock_queue;
535
536# we create a special coro because we want to cede,
537# to reduce pressure on the coro pool (because most callbacks
538# return immediately and can be reused) and because we cannot cede
539# inside an event callback.
540our $unblock_scheduler = new Coro sub {
541 while () {
542 while (my $cb = pop @unblock_queue) {
543 # this is an inlined copy of async_pool
544 my $coro = (pop @async_pool) || new Coro \&pool_handler;
545
546 $coro->{_invoke} = $cb;
547 $coro->ready;
548 cede; # for short-lived callbacks, this reduces pressure on the coro pool
549 }
550 schedule; # sleep well
551 }
552};
553$unblock_scheduler->desc ("[unblock_sub scheduler]");
554
555sub unblock_sub(&) {
556 my $cb = shift;
557
558 sub {
559 unshift @unblock_queue, [$cb, @_];
560 $unblock_scheduler->ready;
561 }
562}
563
564=back
565
247=cut 566=cut
248 567
2491; 5681;
250 569
251=head1 BUGS/LIMITATIONS 570=head1 BUGS/LIMITATIONS
252 571
253 - could be faster, especially when the core would introduce special 572 - you must make very sure that no coro is still active on global
254 support for coroutines (like it does for threads). 573 destruction. very bad things might happen otherwise (usually segfaults).
255 - there is still a memleak on coroutine termination that I could not 574
256 identify. Could be as small as a single SV.
257 - this module is not well-tested.
258 - if variables or arguments "disappear" (become undef) or become
259 corrupted please contact the author so he cen iron out the
260 remaining bugs.
261 - this module is not thread-safe. You must only ever use this module from 575 - this module is not thread-safe. You should only ever use this module
262 the same thread (this requirement might be loosened in the future to 576 from the same thread (this requirement might be loosened in the future
263 allow per-thread schedulers, but Coro::State does not yet allow this). 577 to allow per-thread schedulers, but Coro::State does not yet allow
578 this).
264 579
265=head1 SEE ALSO 580=head1 SEE ALSO
266 581
267L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 582Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
268L<Coro::Signal>, L<Coro::State>, L<Coro::Event>. 583
584Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
585
586Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
587
588Embedding: L<Coro:MakeMaker>
269 589
270=head1 AUTHOR 590=head1 AUTHOR
271 591
272 Marc Lehmann <pcg@goof.com> 592 Marc Lehmann <schmorp@schmorp.de>
273 http://www.goof.com/pcg/marc/ 593 http://home.schmorp.de/
274 594
275=cut 595=cut
276 596

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