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Revision 1.22 by root, Mon Jul 23 02:14:19 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
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 $VERSION = '3.8';
56
59@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
60@EXPORT_OK = qw($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 $self->{destroy_cb}) || []};
158}
159
160sub _do_trace_sub {
161 &{$current->{_trace_sub_cb}}
162}
163
164sub _do_trace_line {
165 &{$current->{_trace_line_cb}}
166}
167
168# this coroutine is necessary because a coroutine
169# cannot destroy itself.
170my @destroy;
171my $manager;
172
173$manager = new Coro sub {
174 while () {
175 (shift @destroy)->_cancel
176 while @destroy;
177
178 &schedule;
179 }
180};
181$manager->desc ("[coro manager]");
182$manager->prio (PRIO_MAX);
126 183
127# static methods. not really. 184# static methods. not really.
128 185
186=back
187
129=head2 STATIC METHODS 188=head2 STATIC METHODS
130 189
131Static methods are actually functions that operate on the current process only. 190Static methods are actually functions that operate on the current coroutine only.
132 191
133=over 4 192=over 4
134 193
135=item async { ... } [@args...] 194=item async { ... } [@args...]
136 195
137Create a new asynchronous process and return it's process object 196Create a new asynchronous coroutine and return it's coroutine object
138(usually unused). When the sub returns the new process is automatically 197(usually unused). When the sub returns the new coroutine is automatically
139terminated. 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.
140 203
141 # create a new coroutine that just prints its arguments 204 # create a new coroutine that just prints its arguments
142 async { 205 async {
143 print "@_\n"; 206 print "@_\n";
144 } 1,2,3,4; 207 } 1,2,3,4;
145 208
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 209=cut
150 210
151sub async(&@) { 211sub async(&@) {
152 my $pid = new Coro @_; 212 my $coro = new Coro @_;
153 $pid->ready; 213 $coro->ready;
154 $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
155} 274}
156 275
157=item schedule 276=item schedule
158 277
159Calls 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
160into the ready queue, so calling this function usually means you will 279into the ready queue, so calling this function usually means you will
161never be called again. 280never be called again unless something else (e.g. an event handler) calls
281ready.
162 282
163=cut 283The canonical way to wait on external events is this:
164 284
165my $prev; 285 {
286 # remember current coroutine
287 my $current = $Coro::current;
166 288
167sub schedule { 289 # register a hypothetical event handler
168 # should be done using priorities :( 290 on_event_invoke sub {
169 ($prev, $current) = ($current, shift @ready || $idle); 291 # wake up sleeping coroutine
170 Coro::State::transfer($prev, $current); 292 $current->ready;
171} 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 }
172 301
173=item cede 302=item cede
174 303
175"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
176ready 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
177current "timeslice" to other coroutines of the same or higher priority. 306current "timeslice" to other coroutines of the same or higher priority.
178 307
179=cut 308Returns true if at least one coroutine switch has happened.
180 309
181sub cede { 310=item Coro::cede_notself
182 $current->ready;
183 &schedule;
184}
185 311
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.
316
186=item terminate 317=item terminate [arg...]
187 318
188Terminates the current process. 319Terminates the current coroutine with the given status values (see L<cancel>).
189
190Future versions of this function will allow result arguments.
191 320
192=cut 321=cut
193 322
194sub terminate { 323sub terminate {
195 my $self = $current; 324 $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} 325}
202 326
203=back 327=back
204 328
205# dynamic methods 329# dynamic methods
206 330
207=head2 PROCESS METHODS 331=head2 COROUTINE METHODS
208 332
209These are the methods you can call on process objects. 333These are the methods you can call on coroutine objects.
210 334
211=over 4 335=over 4
212 336
213=item new Coro \&sub [, @args...] 337=item new Coro \&sub [, @args...]
214 338
215Create 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
216automatically terminates. To start the process you must first put it into 340automatically terminates as if C<terminate> with the returned values were
341called. To make the coroutine run you must first put it into the ready queue
217the ready queue by calling the ready method. 342by calling the ready method.
218 343
219The coderef you submit MUST NOT be a closure that refers to variables 344See C<async> for additional discussion.
220in an outer scope. This does NOT work. Pass arguments into it instead.
221 345
222=cut 346=cut
223 347
224sub _newcoro { 348sub _run_coro {
225 terminate &{+shift}; 349 terminate &{+shift};
226} 350}
227 351
228sub new { 352sub new {
229 my $class = shift; 353 my $class = shift;
230 bless {
231 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
232 }, $class;
233}
234 354
235=item $process->ready 355 $class->SUPER::new (\&_run_coro, @_)
356}
236 357
237Put the current process into the ready queue. 358=item $success = $coroutine->ready
238 359
239=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.
240 363
241sub ready { 364=item $is_ready = $coroutine->is_ready
242 push @ready, $_[0]; 365
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.
373
374=cut
375
376sub cancel {
377 my $self = shift;
378 $self->{status} = [@_];
379
380 if ($current == $self) {
381 push @destroy, $self;
382 $manager->ready;
383 &schedule while 1;
384 } else {
385 $self->_cancel;
386 }
387}
388
389=item $coroutine->join
390
391Wait until the coroutine terminates and return any values given to the
392C<terminate> or C<cancel> functions. C<join> can be called multiple times
393from multiple coroutine.
394
395=cut
396
397sub join {
398 my $self = shift;
399
400 unless ($self->{status}) {
401 my $current = $current;
402
403 push @{$self->{destroy_cb}}, sub {
404 $current->ready;
405 undef $current;
406 };
407
408 &schedule while $current;
409 }
410
411 wantarray ? @{$self->{status}} : $self->{status}[0];
412}
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
428=item $oldprio = $coroutine->prio ($newprio)
429
430Sets (or gets, if the argument is missing) the priority of the
431coroutine. Higher priority coroutines get run before lower priority
432coroutines. Priorities are small signed integers (currently -4 .. +3),
433that you can refer to using PRIO_xxx constants (use the import tag :prio
434to get then):
435
436 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
437 3 > 1 > 0 > -1 > -3 > -4
438
439 # set priority to HIGH
440 current->prio(PRIO_HIGH);
441
442The idle coroutine ($Coro::idle) always has a lower priority than any
443existing coroutine.
444
445Changing the priority of the current coroutine will take effect immediately,
446but changing the priority of coroutines in the ready queue (but not
447running) will only take effect after the next schedule (of that
448coroutine). This is a bug that will be fixed in some future version.
449
450=item $newprio = $coroutine->nice ($change)
451
452Similar to C<prio>, but subtract the given value from the priority (i.e.
453higher values mean lower priority, just as in unix).
454
455=item $olddesc = $coroutine->desc ($newdesc)
456
457Sets (or gets in case the argument is missing) the description for this
458coroutine. This is just a free-form string you can associate with a coroutine.
459
460=cut
461
462sub desc {
463 my $old = $_[0]{desc};
464 $_[0]{desc} = $_[1] if @_ > 1;
465 $old;
243} 466}
244 467
245=back 468=back
246 469
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
247=cut 570=cut
248 571
2491; 5721;
250 573
251=head1 BUGS/LIMITATIONS 574=head1 BUGS/LIMITATIONS
252 575
253 - could be faster, especially when the core would introduce special 576 - you must make very sure that no coro is still active on global
254 support for coroutines (like it does for threads). 577 destruction. very bad things might happen otherwise (usually segfaults).
255 - there is still a memleak on coroutine termination that I could not 578
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 579 - 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 580 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). 581 to allow per-thread schedulers, but Coro::State does not yet allow
582 this).
264 583
265=head1 SEE ALSO 584=head1 SEE ALSO
266 585
267L<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>.
268L<Coro::Signal>, L<Coro::State>, L<Coro::Event>. 587
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>
269 593
270=head1 AUTHOR 594=head1 AUTHOR
271 595
272 Marc Lehmann <pcg@goof.com> 596 Marc Lehmann <schmorp@schmorp.de>
273 http://www.goof.com/pcg/marc/ 597 http://home.schmorp.de/
274 598
275=cut 599=cut
276 600

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