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1=head1 NAME 1=head1 NAME
2 2
3Coro - coroutine process abstraction 3Coro - the only real threads in perl
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use Coro; 7 use Coro;
8 8
26 $locked = 1; 26 $locked = 1;
27 $lock->up; 27 $lock->up;
28 28
29=head1 DESCRIPTION 29=head1 DESCRIPTION
30 30
31This module collection manages coroutines. Coroutines are similar to 31For a tutorial-style introduction, please read the L<Coro::Intro>
32threads but don't (in general) run in parallel at the same time even 32manpage. This manpage mainly contains reference information.
33on SMP machines. The specific flavor of coroutine used in this module
34also guarantees you that it will not switch between coroutines unless
35necessary, at easily-identified points in your program, so locking and
36parallel access are rarely an issue, making coroutine programming much
37safer and easier than threads programming.
38 33
39Unlike a normal perl program, however, coroutines allow you to have 34This module collection manages continuations in general, most often
40multiple running interpreters that share data, which is especially useful 35in the form of cooperative threads (also called coroutines in the
41to code pseudo-parallel processes and for event-based programming, such as 36documentation). They are similar to kernel threads but don't (in general)
42multiple HTTP-GET requests running concurrently. See L<Coro::AnyEvent> to 37run in parallel at the same time even on SMP machines. The specific flavor
43learn more. 38of thread offered by this module also guarantees you that it will not
39switch between threads unless necessary, at easily-identified points in
40your program, so locking and parallel access are rarely an issue, making
41thread programming much safer and easier than using other thread models.
44 42
45Coroutines are also useful because Perl has no support for threads (the so 43Unlike the so-called "Perl threads" (which are not actually real threads
46called "threads" that perl offers are nothing more than the (bad) process 44but only the windows process emulation ported to unix), Coro provides a
47emulation coming from the Windows platform: On standard operating systems 45full shared address space, which makes communication between threads
48they serve no purpose whatsoever, except by making your programs slow and 46very easy. And threads are fast, too: disabling the Windows process
49making them use a lot of memory. Best disable them when building perl, or 47emulation code in your perl and using Coro can easily result in a two to
50aks your software vendor/distributor to do it for you). 48four times speed increase for your programs.
51 49
50Coro achieves that by supporting multiple running interpreters that share
51data, which is especially useful to code pseudo-parallel processes and
52for event-based programming, such as multiple HTTP-GET requests running
53concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
54into an event-based environment.
55
52In this module, coroutines are defined as "callchain + lexical variables + 56In this module, a thread is defined as "callchain + lexical variables +
53@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain, 57@_ + $_ + $@ + $/ + C stack), that is, a thread has its own callchain,
54its own set of lexicals and its own set of perls most important global 58its own set of lexicals and its own set of perls most important global
55variables (see L<Coro::State> for more configuration). 59variables (see L<Coro::State> for more configuration and background info).
60
61See also the C<SEE ALSO> section at the end of this document - the Coro
62module family is quite large.
56 63
57=cut 64=cut
58 65
59package Coro; 66package Coro;
60 67
61use strict; 68use strict qw(vars subs);
62no warnings "uninitialized"; 69no warnings "uninitialized";
70
71use Guard ();
63 72
64use Coro::State; 73use Coro::State;
65 74
66use base qw(Coro::State Exporter); 75use base qw(Coro::State Exporter);
67 76
68our $idle; # idle handler 77our $idle; # idle handler
69our $main; # main coroutine 78our $main; # main coroutine
70our $current; # current coroutine 79our $current; # current coroutine
71 80
72our $VERSION = 4.8; 81our $VERSION = 5.13;
73 82
74our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); 83our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
75our %EXPORT_TAGS = ( 84our %EXPORT_TAGS = (
76 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 85 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
77); 86);
78our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); 87our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
79 88
89=head1 GLOBAL VARIABLES
90
80=over 4 91=over 4
81 92
82=item $Coro::main 93=item $Coro::main
83 94
84This variable stores the coroutine object that represents the main 95This variable stores the coroutine object that represents the main
86coroutines, it is mainly useful to compare again C<$Coro::current>, to see 97coroutines, it is mainly useful to compare again C<$Coro::current>, to see
87whether you are running in the main program or not. 98whether you are running in the main program or not.
88 99
89=cut 100=cut
90 101
91$main = new Coro; 102# $main is now being initialised by Coro::State
92 103
93=item $Coro::current 104=item $Coro::current
94 105
95The coroutine object representing the current coroutine (the last 106The coroutine object representing the current coroutine (the last
96coroutine that the Coro scheduler switched to). The initial value is 107coroutine that the Coro scheduler switched to). The initial value is
97C<$main> (of course). 108C<$Coro::main> (of course).
98 109
99This variable is B<strictly> I<read-only>. You can take copies of the 110This variable is B<strictly> I<read-only>. You can take copies of the
100value stored in it and use it as any other coroutine object, but you must 111value stored in it and use it as any other coroutine object, but you must
101not otherwise modify the variable itself. 112not otherwise modify the variable itself.
102 113
103=cut 114=cut
104 115
105$main->{desc} = "[main::]";
106
107# maybe some other module used Coro::Specific before...
108$main->{_specific} = $current->{_specific}
109 if $current;
110
111_set_current $main;
112
113sub current() { $current } # [DEPRECATED] 116sub current() { $current } # [DEPRECATED]
114 117
115=item $Coro::idle 118=item $Coro::idle
116 119
117This variable is mainly useful to integrate Coro into event loops. It is 120This variable is mainly useful to integrate Coro into event loops. It is
118usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is 121usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
119pretty low-level functionality. 122pretty low-level functionality.
120 123
121This variable stores a callback that is called whenever the scheduler 124This variable stores either a coroutine or a callback.
125
126If it is a callback, the it is called whenever the scheduler finds no
122finds no ready coroutines to run. The default implementation prints 127ready coroutines to run. The default implementation prints "FATAL:
123"FATAL: deadlock detected" and exits, because the program has no other way 128deadlock detected" and exits, because the program has no other way to
124to continue. 129continue.
125 130
131If it is a coroutine object, then this object will be readied (without
132invoking any ready hooks, however) when the scheduler finds no other ready
133coroutines to run.
134
126This hook is overwritten by modules such as C<Coro::Timer> and 135This hook is overwritten by modules such as C<Coro::EV> and
127C<Coro::AnyEvent> to wait on an external event that hopefully wake up a 136C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
128coroutine so the scheduler can run it. 137coroutine so the scheduler can run it.
129 138
130Note that the callback I<must not>, under any circumstances, block 139Note that the callback I<must not>, under any circumstances, block
131the current coroutine. Normally, this is achieved by having an "idle 140the current coroutine. Normally, this is achieved by having an "idle
132coroutine" that calls the event loop and then blocks again, and then 141coroutine" that calls the event loop and then blocks again, and then
133readying that coroutine in the idle handler. 142readying that coroutine in the idle handler, or by simply placing the idle
143coroutine in this variable.
134 144
135See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this 145See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
136technique. 146technique.
137 147
138Please note that if your callback recursively invokes perl (e.g. for event 148Please note that if your callback recursively invokes perl (e.g. for event
143$idle = sub { 153$idle = sub {
144 require Carp; 154 require Carp;
145 Carp::croak ("FATAL: deadlock detected"); 155 Carp::croak ("FATAL: deadlock detected");
146}; 156};
147 157
148sub _cancel {
149 my ($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->{_on_destroy}) || []};
158}
159
160# this coroutine is necessary because a coroutine 158# this coroutine is necessary because a coroutine
161# cannot destroy itself. 159# cannot destroy itself.
162my @destroy; 160our @destroy;
163my $manager; 161our $manager;
164 162
165$manager = new Coro sub { 163$manager = new Coro sub {
166 while () { 164 while () {
167 (shift @destroy)->_cancel 165 Coro::_cancel shift @destroy
168 while @destroy; 166 while @destroy;
169 167
170 &schedule; 168 &schedule;
171 } 169 }
172}; 170};
173$manager->desc ("[coro manager]"); 171$manager->{desc} = "[coro manager]";
174$manager->prio (PRIO_MAX); 172$manager->prio (PRIO_MAX);
175 173
176=back 174=back
177 175
178=head2 SIMPLE COROUTINE CREATION 176=head1 SIMPLE COROUTINE CREATION
179 177
180=over 4 178=over 4
181 179
182=item async { ... } [@args...] 180=item async { ... } [@args...]
183 181
184Create a new coroutine and return it's coroutine object (usually 182Create a new coroutine and return its coroutine object (usually
185unused). The coroutine will be put into the ready queue, so 183unused). The coroutine will be put into the ready queue, so
186it will start running automatically on the next scheduler run. 184it will start running automatically on the next scheduler run.
187 185
188The first argument is a codeblock/closure that should be executed in the 186The first argument is a codeblock/closure that should be executed in the
189coroutine. When it returns argument returns the coroutine is automatically 187coroutine. When it returns argument returns the coroutine is automatically
220Similar to C<async>, but uses a coroutine pool, so you should not call 218Similar to C<async>, but uses a coroutine pool, so you should not call
221terminate or join on it (although you are allowed to), and you get a 219terminate or join on it (although you are allowed to), and you get a
222coroutine that might have executed other code already (which can be good 220coroutine that might have executed other code already (which can be good
223or bad :). 221or bad :).
224 222
225On the plus side, this function is faster than creating (and destroying) 223On the plus side, this function is about twice as fast as creating (and
226a completely new coroutine, so if you need a lot of generic coroutines in 224destroying) a completely new coroutine, so if you need a lot of generic
227quick successsion, use C<async_pool>, not C<async>. 225coroutines in quick successsion, use C<async_pool>, not C<async>.
228 226
229The code block is executed in an C<eval> context and a warning will be 227The code block is executed in an C<eval> context and a warning will be
230issued in case of an exception instead of terminating the program, as 228issued in case of an exception instead of terminating the program, as
231C<async> does. As the coroutine is being reused, stuff like C<on_destroy> 229C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
232will not work in the expected way, unless you call terminate or cancel, 230will not work in the expected way, unless you call terminate or cancel,
235 233
236The priority will be reset to C<0> after each run, tracing will be 234The priority will be reset to C<0> after each run, tracing will be
237disabled, the description will be reset and the default output filehandle 235disabled, the description will be reset and the default output filehandle
238gets restored, so you can change all these. Otherwise the coroutine will 236gets restored, so you can change all these. Otherwise the coroutine will
239be re-used "as-is": most notably if you change other per-coroutine global 237be re-used "as-is": most notably if you change other per-coroutine global
240stuff such as C<$/> you I<must needs> to revert that change, which is most 238stuff such as C<$/> you I<must needs> revert that change, which is most
241simply done by using local as in: C< local $/ >. 239simply done by using local as in: C<< local $/ >>.
242 240
243The pool size is limited to C<8> idle coroutines (this can be adjusted by 241The idle pool size is limited to C<8> idle coroutines (this can be
244changing $Coro::POOL_SIZE), and there can be as many non-idle coros as 242adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
245required. 243coros as required.
246 244
247If you are concerned about pooled coroutines growing a lot because a 245If you are concerned about pooled coroutines growing a lot because a
248single C<async_pool> used a lot of stackspace you can e.g. C<async_pool 246single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
249{ terminate }> once per second or so to slowly replenish the pool. In 247{ terminate }> once per second or so to slowly replenish the pool. In
250addition to that, when the stacks used by a handler grows larger than 16kb 248addition to that, when the stacks used by a handler grows larger than 32kb
251(adjustable via $Coro::POOL_RSS) it will also be destroyed. 249(adjustable via $Coro::POOL_RSS) it will also be destroyed.
252 250
253=cut 251=cut
254 252
255our $POOL_SIZE = 8; 253our $POOL_SIZE = 8;
256our $POOL_RSS = 16 * 1024; 254our $POOL_RSS = 32 * 1024;
257our @async_pool; 255our @async_pool;
258 256
259sub pool_handler { 257sub pool_handler {
260 my $cb;
261
262 while () { 258 while () {
263 eval { 259 eval {
264 while () { 260 &{&_pool_handler} while 1;
265 _pool_1 $cb;
266 &$cb;
267 _pool_2 $cb;
268 &schedule;
269 }
270 }; 261 };
271 262
272 if ($@) {
273 last if $@ eq "\3async_pool terminate\2\n";
274 warn $@; 263 warn $@ if $@;
275 }
276 } 264 }
277} 265}
278 266
279sub async_pool(&@) {
280 # this is also inlined into the unlock_scheduler
281 my $coro = (pop @async_pool) || new Coro \&pool_handler;
282
283 $coro->{_invoke} = [@_];
284 $coro->ready;
285
286 $coro
287}
288
289=back 267=back
290 268
291=head2 STATIC METHODS 269=head1 STATIC METHODS
292 270
293Static methods are actually functions that operate on the current coroutine. 271Static methods are actually functions that implicitly operate on the
272current coroutine.
294 273
295=over 4 274=over 4
296 275
297=item schedule 276=item schedule
298 277
313>> on that once some event happens, and last you call C<schedule> to put 292>> on that once some event happens, and last you call C<schedule> to put
314yourself to sleep. Note that a lot of things can wake your coroutine up, 293yourself to sleep. Note that a lot of things can wake your coroutine up,
315so you need to check whether the event indeed happened, e.g. by storing the 294so you need to check whether the event indeed happened, e.g. by storing the
316status in a variable. 295status in a variable.
317 296
318The canonical way to wait on external events is this: 297See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
319
320 {
321 # remember current coroutine
322 my $current = $Coro::current;
323
324 # register a hypothetical event handler
325 on_event_invoke sub {
326 # wake up sleeping coroutine
327 $current->ready;
328 undef $current;
329 };
330
331 # call schedule until event occurred.
332 # in case we are woken up for other reasons
333 # (current still defined), loop.
334 Coro::schedule while $current;
335 }
336 298
337=item cede 299=item cede
338 300
339"Cede" to other coroutines. This function puts the current coroutine into 301"Cede" to other coroutines. This function puts the current coroutine into
340the ready queue and calls C<schedule>, which has the effect of giving 302the ready queue and calls C<schedule>, which has the effect of giving
352 314
353=item terminate [arg...] 315=item terminate [arg...]
354 316
355Terminates the current coroutine with the given status values (see L<cancel>). 317Terminates the current coroutine with the given status values (see L<cancel>).
356 318
319=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
320
321These function install enter and leave winders in the current scope. The
322enter block will be executed when on_enter is called and whenever the
323current coroutine is re-entered by the scheduler, while the leave block is
324executed whenever the current coroutine is blocked by the scheduler, and
325also when the containing scope is exited (by whatever means, be it exit,
326die, last etc.).
327
328I<Neither invoking the scheduler, nor exceptions, are allowed within those
329BLOCKs>. That means: do not even think about calling C<die> without an
330eval, and do not even think of entering the scheduler in any way.
331
332Since both BLOCKs are tied to the current scope, they will automatically
333be removed when the current scope exits.
334
335These functions implement the same concept as C<dynamic-wind> in scheme
336does, and are useful when you want to localise some resource to a specific
337coroutine.
338
339They slow down coroutine switching considerably for coroutines that use
340them (But coroutine switching is still reasonably fast if the handlers are
341fast).
342
343These functions are best understood by an example: The following function
344will change the current timezone to "Antarctica/South_Pole", which
345requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
346which remember/change the current timezone and restore the previous
347value, respectively, the timezone is only changes for the coroutine that
348installed those handlers.
349
350 use POSIX qw(tzset);
351
352 async {
353 my $old_tz; # store outside TZ value here
354
355 Coro::on_enter {
356 $old_tz = $ENV{TZ}; # remember the old value
357
358 $ENV{TZ} = "Antarctica/South_Pole";
359 tzset; # enable new value
360 };
361
362 Coro::on_leave {
363 $ENV{TZ} = $old_tz;
364 tzset; # restore old value
365 };
366
367 # at this place, the timezone is Antarctica/South_Pole,
368 # without disturbing the TZ of any other coroutine.
369 };
370
371This can be used to localise about any resource (locale, uid, current
372working directory etc.) to a block, despite the existance of other
373coroutines.
374
357=item killall 375=item killall
358 376
359Kills/terminates/cancels all coroutines except the currently running 377Kills/terminates/cancels all coroutines except the currently running one.
360one. This is useful after a fork, either in the child or the parent, as
361usually only one of them should inherit the running coroutines.
362 378
363Note that while this will try to free some of the main programs resources, 379Note that while this will try to free some of the main interpreter
380resources if the calling coroutine isn't the main coroutine, but one
364you cannot free all of them, so if a coroutine that is not the main 381cannot free all of them, so if a coroutine that is not the main coroutine
365program calls this function, there will be some one-time resource leak. 382calls this function, there will be some one-time resource leak.
366 383
367=cut 384=cut
368
369sub terminate {
370 $current->cancel (@_);
371}
372 385
373sub killall { 386sub killall {
374 for (Coro::State::list) { 387 for (Coro::State::list) {
375 $_->cancel 388 $_->cancel
376 if $_ != $current && UNIVERSAL::isa $_, "Coro"; 389 if $_ != $current && UNIVERSAL::isa $_, "Coro";
377 } 390 }
378} 391}
379 392
380=back 393=back
381 394
382=head2 COROUTINE METHODS 395=head1 COROUTINE OBJECT METHODS
383 396
384These are the methods you can call on coroutine objects (or to create 397These are the methods you can call on coroutine objects (or to create
385them). 398them).
386 399
387=over 4 400=over 4
396See C<async> and C<Coro::State::new> for additional info about the 409See C<async> and C<Coro::State::new> for additional info about the
397coroutine environment. 410coroutine environment.
398 411
399=cut 412=cut
400 413
401sub _run_coro { 414sub _coro_run {
402 terminate &{+shift}; 415 terminate &{+shift};
403}
404
405sub new {
406 my $class = shift;
407
408 $class->SUPER::new (\&_run_coro, @_)
409} 416}
410 417
411=item $success = $coroutine->ready 418=item $success = $coroutine->ready
412 419
413Put the given coroutine into the end of its ready queue (there is one 420Put the given coroutine into the end of its ready queue (there is one
430 437
431=cut 438=cut
432 439
433sub cancel { 440sub cancel {
434 my $self = shift; 441 my $self = shift;
435 $self->{_status} = [@_];
436 442
437 if ($current == $self) { 443 if ($current == $self) {
438 push @destroy, $self; 444 terminate @_;
439 $manager->ready;
440 &schedule while 1;
441 } else { 445 } else {
446 $self->{_status} = [@_];
442 $self->_cancel; 447 $self->_cancel;
443 } 448 }
444} 449}
450
451=item $coroutine->schedule_to
452
453Puts the current coroutine to sleep (like C<Coro::schedule>), but instead
454of continuing with the next coro from the ready queue, always switch to
455the given coroutine object (regardless of priority etc.). The readyness
456state of that coroutine isn't changed.
457
458This is an advanced method for special cases - I'd love to hear about any
459uses for this one.
460
461=item $coroutine->cede_to
462
463Like C<schedule_to>, but puts the current coroutine into the ready
464queue. This has the effect of temporarily switching to the given
465coroutine, and continuing some time later.
466
467This is an advanced method for special cases - I'd love to hear about any
468uses for this one.
469
470=item $coroutine->throw ([$scalar])
471
472If C<$throw> is specified and defined, it will be thrown as an exception
473inside the coroutine at the next convenient point in time. Otherwise
474clears the exception object.
475
476Coro will check for the exception each time a schedule-like-function
477returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
478>>, C<< Coro::Handle->readable >> and so on. Most of these functions
479detect this case and return early in case an exception is pending.
480
481The exception object will be thrown "as is" with the specified scalar in
482C<$@>, i.e. if it is a string, no line number or newline will be appended
483(unlike with C<die>).
484
485This can be used as a softer means than C<cancel> to ask a coroutine to
486end itself, although there is no guarantee that the exception will lead to
487termination, and if the exception isn't caught it might well end the whole
488program.
489
490You might also think of C<throw> as being the moral equivalent of
491C<kill>ing a coroutine with a signal (in this case, a scalar).
445 492
446=item $coroutine->join 493=item $coroutine->join
447 494
448Wait until the coroutine terminates and return any values given to the 495Wait until the coroutine terminates and return any values given to the
449C<terminate> or C<cancel> functions. C<join> can be called concurrently 496C<terminate> or C<cancel> functions. C<join> can be called concurrently
511higher values mean lower priority, just as in unix). 558higher values mean lower priority, just as in unix).
512 559
513=item $olddesc = $coroutine->desc ($newdesc) 560=item $olddesc = $coroutine->desc ($newdesc)
514 561
515Sets (or gets in case the argument is missing) the description for this 562Sets (or gets in case the argument is missing) the description for this
516coroutine. This is just a free-form string you can associate with a coroutine. 563coroutine. This is just a free-form string you can associate with a
564coroutine.
517 565
518This method simply sets the C<< $coroutine->{desc} >> member to the given string. You 566This method simply sets the C<< $coroutine->{desc} >> member to the given
519can modify this member directly if you wish. 567string. You can modify this member directly if you wish.
520
521=item $coroutine->throw ([$scalar])
522
523If C<$throw> is specified and defined, it will be thrown as an exception
524inside the coroutine at the next convinient point in time (usually after
525it gains control at the next schedule/transfer/cede). Otherwise clears the
526exception object.
527
528The exception object will be thrown "as is" with the specified scalar in
529C<$@>, i.e. if it is a string, no line number or newline will be appended
530(unlike with C<die>).
531
532This can be used as a softer means than C<cancel> to ask a coroutine to
533end itself, although there is no guarentee that the exception will lead to
534termination, and if the exception isn't caught it might well end the whole
535program.
536 568
537=cut 569=cut
538 570
539sub desc { 571sub desc {
540 my $old = $_[0]{desc}; 572 my $old = $_[0]{desc};
541 $_[0]{desc} = $_[1] if @_ > 1; 573 $_[0]{desc} = $_[1] if @_ > 1;
542 $old; 574 $old;
543} 575}
544 576
577sub transfer {
578 require Carp;
579 Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
580}
581
545=back 582=back
546 583
547=head2 GLOBAL FUNCTIONS 584=head1 GLOBAL FUNCTIONS
548 585
549=over 4 586=over 4
550 587
551=item Coro::nready 588=item Coro::nready
552 589
557would cause a deadlock unless there is an idle handler that wakes up some 594would cause a deadlock unless there is an idle handler that wakes up some
558coroutines. 595coroutines.
559 596
560=item my $guard = Coro::guard { ... } 597=item my $guard = Coro::guard { ... }
561 598
562This creates and returns a guard object. Nothing happens until the object 599This function still exists, but is deprecated. Please use the
563gets destroyed, in which case the codeblock given as argument will be 600C<Guard::guard> function instead.
564executed. This is useful to free locks or other resources in case of a
565runtime error or when the coroutine gets canceled, as in both cases the
566guard block will be executed. The guard object supports only one method,
567C<< ->cancel >>, which will keep the codeblock from being executed.
568 601
569Example: set some flag and clear it again when the coroutine gets canceled
570or the function returns:
571
572 sub do_something {
573 my $guard = Coro::guard { $busy = 0 };
574 $busy = 1;
575
576 # do something that requires $busy to be true
577 }
578
579=cut 602=cut
580 603
581sub guard(&) { 604BEGIN { *guard = \&Guard::guard }
582 bless \(my $cb = $_[0]), "Coro::guard"
583}
584
585sub Coro::guard::cancel {
586 ${$_[0]} = sub { };
587}
588
589sub Coro::guard::DESTROY {
590 ${$_[0]}->();
591}
592
593 605
594=item unblock_sub { ... } 606=item unblock_sub { ... }
595 607
596This utility function takes a BLOCK or code reference and "unblocks" it, 608This utility function takes a BLOCK or code reference and "unblocks" it,
597returning a new coderef. Unblocking means that calling the new coderef 609returning a new coderef. Unblocking means that calling the new coderef
599original code ref will be called (with parameters) from within another 611original code ref will be called (with parameters) from within another
600coroutine. 612coroutine.
601 613
602The reason this function exists is that many event libraries (such as the 614The reason this function exists is that many event libraries (such as the
603venerable L<Event|Event> module) are not coroutine-safe (a weaker form 615venerable L<Event|Event> module) are not coroutine-safe (a weaker form
604of thread-safety). This means you must not block within event callbacks, 616of reentrancy). This means you must not block within event callbacks,
605otherwise you might suffer from crashes or worse. The only event library 617otherwise you might suffer from crashes or worse. The only event library
606currently known that is safe to use without C<unblock_sub> is L<EV>. 618currently known that is safe to use without C<unblock_sub> is L<EV>.
607 619
608This function allows your callbacks to block by executing them in another 620This function allows your callbacks to block by executing them in another
609coroutine where it is safe to block. One example where blocking is handy 621coroutine where it is safe to block. One example where blocking is handy
632# return immediately and can be reused) and because we cannot cede 644# return immediately and can be reused) and because we cannot cede
633# inside an event callback. 645# inside an event callback.
634our $unblock_scheduler = new Coro sub { 646our $unblock_scheduler = new Coro sub {
635 while () { 647 while () {
636 while (my $cb = pop @unblock_queue) { 648 while (my $cb = pop @unblock_queue) {
637 # this is an inlined copy of async_pool 649 &async_pool (@$cb);
638 my $coro = (pop @async_pool) || new Coro \&pool_handler;
639 650
640 $coro->{_invoke} = $cb;
641 $coro->ready;
642 cede; # for short-lived callbacks, this reduces pressure on the coro pool 651 # for short-lived callbacks, this reduces pressure on the coro pool
652 # as the chance is very high that the async_poll coro will be back
653 # in the idle state when cede returns
654 cede;
643 } 655 }
644 schedule; # sleep well 656 schedule; # sleep well
645 } 657 }
646}; 658};
647$unblock_scheduler->desc ("[unblock_sub scheduler]"); 659$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
648 660
649sub unblock_sub(&) { 661sub unblock_sub(&) {
650 my $cb = shift; 662 my $cb = shift;
651 663
652 sub { 664 sub {
653 unshift @unblock_queue, [$cb, @_]; 665 unshift @unblock_queue, [$cb, @_];
654 $unblock_scheduler->ready; 666 $unblock_scheduler->ready;
655 } 667 }
656} 668}
657 669
670=item $cb = Coro::rouse_cb
671
672Create and return a "rouse callback". That's a code reference that,
673when called, will remember a copy of its arguments and notify the owner
674coroutine of the callback.
675
676See the next function.
677
678=item @args = Coro::rouse_wait [$cb]
679
680Wait for the specified rouse callback (or the last one that was created in
681this coroutine).
682
683As soon as the callback is invoked (or when the callback was invoked
684before C<rouse_wait>), it will return the arguments originally passed to
685the rouse callback.
686
687See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
688
658=back 689=back
659 690
660=cut 691=cut
661 692
6621; 6931;
663 694
695=head1 HOW TO WAIT FOR A CALLBACK
696
697It is very common for a coroutine to wait for some callback to be
698called. This occurs naturally when you use coroutines in an otherwise
699event-based program, or when you use event-based libraries.
700
701These typically register a callback for some event, and call that callback
702when the event occured. In a coroutine, however, you typically want to
703just wait for the event, simplyifying things.
704
705For example C<< AnyEvent->child >> registers a callback to be called when
706a specific child has exited:
707
708 my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
709
710But from withina coroutine, you often just want to write this:
711
712 my $status = wait_for_child $pid;
713
714Coro offers two functions specifically designed to make this easy,
715C<Coro::rouse_cb> and C<Coro::rouse_wait>.
716
717The first function, C<rouse_cb>, generates and returns a callback that,
718when invoked, will save its arguments and notify the coroutine that
719created the callback.
720
721The second function, C<rouse_wait>, waits for the callback to be called
722(by calling C<schedule> to go to sleep) and returns the arguments
723originally passed to the callback.
724
725Using these functions, it becomes easy to write the C<wait_for_child>
726function mentioned above:
727
728 sub wait_for_child($) {
729 my ($pid) = @_;
730
731 my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
732
733 my ($rpid, $rstatus) = Coro::rouse_wait;
734 $rstatus
735 }
736
737In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
738you can roll your own, using C<schedule>:
739
740 sub wait_for_child($) {
741 my ($pid) = @_;
742
743 # store the current coroutine in $current,
744 # and provide result variables for the closure passed to ->child
745 my $current = $Coro::current;
746 my ($done, $rstatus);
747
748 # pass a closure to ->child
749 my $watcher = AnyEvent->child (pid => $pid, cb => sub {
750 $rstatus = $_[1]; # remember rstatus
751 $done = 1; # mark $rstatus as valud
752 });
753
754 # wait until the closure has been called
755 schedule while !$done;
756
757 $rstatus
758 }
759
760
664=head1 BUGS/LIMITATIONS 761=head1 BUGS/LIMITATIONS
665 762
763=over 4
764
765=item fork with pthread backend
766
767When Coro is compiled using the pthread backend (which isn't recommended
768but required on many BSDs as their libcs are completely broken), then
769coroutines will not survive a fork. There is no known workaround except to
770fix your libc and use a saner backend.
771
772=item perl process emulation ("threads")
773
666This module is not perl-pseudo-thread-safe. You should only ever use this 774This module is not perl-pseudo-thread-safe. You should only ever use this
667module from the same thread (this requirement might be removed in the 775module from the first thread (this requirement might be removed in the
668future to allow per-thread schedulers, but Coro::State does not yet allow 776future to allow per-thread schedulers, but Coro::State does not yet allow
669this). I recommend disabling thread support and using processes, as this 777this). I recommend disabling thread support and using processes, as having
670is much faster and uses less memory. 778the windows process emulation enabled under unix roughly halves perl
779performance, even when not used.
780
781=item coroutine switching not signal safe
782
783You must not switch to another coroutine from within a signal handler
784(only relevant with %SIG - most event libraries provide safe signals).
785
786That means you I<MUST NOT> call any function that might "block" the
787current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
788anything that calls those. Everything else, including calling C<ready>,
789works.
790
791=back
792
671 793
672=head1 SEE ALSO 794=head1 SEE ALSO
673 795
674Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. 796Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
675 797
676Debugging: L<Coro::Debug>. 798Debugging: L<Coro::Debug>.
677 799
678Support/Utility: L<Coro::Specific>, L<Coro::Util>. 800Support/Utility: L<Coro::Specific>, L<Coro::Util>.
679 801
680Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. 802Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
803L<Coro::SemaphoreSet>, L<Coro::RWLock>.
681 804
682IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>. 805I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
683 806
684Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>. 807Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
808a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
809L<Coro::Select>.
685 810
686XS API: L<Coro::MakeMaker>. 811XS API: L<Coro::MakeMaker>.
687 812
688Low level Configuration, Coroutine Environment: L<Coro::State>. 813Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
689 814
690=head1 AUTHOR 815=head1 AUTHOR
691 816
692 Marc Lehmann <schmorp@schmorp.de> 817 Marc Lehmann <schmorp@schmorp.de>
693 http://home.schmorp.de/ 818 http://home.schmorp.de/

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