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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
16 cede; # yield to coroutine 16 cede; # yield to coroutine
17 print "3\n"; 17 print "3\n";
18 cede; # and again 18 cede; # and again
19 19
20 # use locking 20 # use locking
21 use Coro::Semaphore;
21 my $lock = new Coro::Semaphore; 22 my $lock = new Coro::Semaphore;
22 my $locked; 23 my $locked;
23 24
24 $lock->down; 25 $lock->down;
25 $locked = 1; 26 $locked = 1;
26 $lock->up; 27 $lock->up;
27 28
28=head1 DESCRIPTION 29=head1 DESCRIPTION
29 30
30This module collection manages coroutines. Coroutines are similar to 31For a tutorial-style introduction, please read the L<Coro::Intro>
31threads but don't (in general) run in parallel at the same time even 32manpage. This manpage mainly contains reference information.
32on SMP machines. The specific flavor of coroutine used in this module
33also guarantees you that it will not switch between coroutines unless
34necessary, at easily-identified points in your program, so locking and
35parallel access are rarely an issue, making coroutine programming much
36safer and easier than threads programming.
37 33
38Unlike a normal perl program, however, coroutines allow you to have 34This module collection manages continuations in general, most often
39multiple running interpreters that share data, which is especially useful 35in the form of cooperative threads (also called coroutines in the
40to code pseudo-parallel processes, such as multiple HTTP-GET requests 36documentation). They are similar to kernel threads but don't (in general)
41running concurrently. 37run in parallel at the same time even on SMP machines. The specific flavor
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.
42 42
43Coroutines are also useful because Perl has no support for threads (the so 43Unlike the so-called "Perl threads" (which are not actually real threads
44called "threads" that perl offers are nothing more than the (bad) process 44but only the windows process emulation ported to unix), Coro provides a
45emulation coming from the Windows platform: On standard operating systems 45full shared address space, which makes communication between threads
46they serve no purpose whatsoever, except by making your programs slow and 46very easy. And threads are fast, too: disabling the Windows process
47making 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
48aks your software vendor/distributor to do it for you). 48four times speed increase for your programs.
49 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
50In this module, coroutines are defined as "callchain + lexical variables + 56In this module, a thread is defined as "callchain + lexical variables +
51@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain, 57@_ + $_ + $@ + $/ + C stack), that is, a thread has its own callchain,
52its 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
53variables (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.
54 63
55=cut 64=cut
56 65
57package Coro; 66package Coro;
58 67
59use strict; 68use strict qw(vars subs);
60no warnings "uninitialized"; 69no warnings "uninitialized";
61 70
62use Coro::State; 71use Coro::State;
63 72
64use base qw(Coro::State Exporter); 73use base qw(Coro::State Exporter);
65 74
66our $idle; # idle handler 75our $idle; # idle handler
67our $main; # main coroutine 76our $main; # main coroutine
68our $current; # current coroutine 77our $current; # current coroutine
69 78
70our $VERSION = 4.6; 79our $VERSION = 5.13;
71 80
72our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); 81our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
73our %EXPORT_TAGS = ( 82our %EXPORT_TAGS = (
74 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 83 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
75); 84);
76our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); 85our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
77 86
87=head1 GLOBAL VARIABLES
88
78=over 4 89=over 4
79 90
80=item $Coro::main 91=item $Coro::main
81 92
82This variable stores the coroutine object that represents the main 93This variable stores the coroutine object that represents the main
83program. While you cna C<ready> it and do most other things you can do to 94program. While you cna C<ready> it and do most other things you can do to
84coroutines, it is mainly useful to compare again C<$Coro::current>, to see 95coroutines, it is mainly useful to compare again C<$Coro::current>, to see
85wether you are running in the main program or not. 96whether you are running in the main program or not.
86 97
87=cut 98=cut
88 99
89$main = new Coro; 100# $main is now being initialised by Coro::State
90 101
91=item $Coro::current 102=item $Coro::current
92 103
93The coroutine object representing the current coroutine (the last 104The coroutine object representing the current coroutine (the last
94coroutine that the Coro scheduler switched to). The initial value is 105coroutine that the Coro scheduler switched to). The initial value is
95C<$main> (of course). 106C<$Coro::main> (of course).
96 107
97This variable is B<strictly> I<read-only>. You can take copies of the 108This variable is B<strictly> I<read-only>. You can take copies of the
98value stored in it and use it as any other coroutine object, but you must 109value stored in it and use it as any other coroutine object, but you must
99not otherwise modify the variable itself. 110not otherwise modify the variable itself.
100 111
101=cut 112=cut
102 113
103$main->{desc} = "[main::]";
104
105# maybe some other module used Coro::Specific before...
106$main->{_specific} = $current->{_specific}
107 if $current;
108
109_set_current $main;
110
111sub current() { $current } # [DEPRECATED] 114sub current() { $current } # [DEPRECATED]
112 115
113=item $Coro::idle 116=item $Coro::idle
114 117
115This variable is mainly useful to integrate Coro into event loops. It is 118This variable is mainly useful to integrate Coro into event loops. It is
116usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is 119usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
117pretty low-level functionality. 120pretty low-level functionality.
118 121
119This variable stores a callback that is called whenever the scheduler 122This variable stores either a coroutine or a callback.
123
124If it is a callback, the it is called whenever the scheduler finds no
120finds no ready coroutines to run. The default implementation prints 125ready coroutines to run. The default implementation prints "FATAL:
121"FATAL: deadlock detected" and exits, because the program has no other way 126deadlock detected" and exits, because the program has no other way to
122to continue. 127continue.
123 128
129If it is a coroutine object, then this object will be readied (without
130invoking any ready hooks, however) when the scheduler finds no other ready
131coroutines to run.
132
124This hook is overwritten by modules such as C<Coro::Timer> and 133This hook is overwritten by modules such as C<Coro::EV> and
125C<Coro::AnyEvent> to wait on an external event that hopefully wake up a 134C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
126coroutine so the scheduler can run it. 135coroutine so the scheduler can run it.
127 136
128Note that the callback I<must not>, under any circumstances, block 137Note that the callback I<must not>, under any circumstances, block
129the current coroutine. Normally, this is achieved by having an "idle 138the current coroutine. Normally, this is achieved by having an "idle
130coroutine" that calls the event loop and then blocks again, and then 139coroutine" that calls the event loop and then blocks again, and then
131readying that coroutine in the idle handler. 140readying that coroutine in the idle handler, or by simply placing the idle
141coroutine in this variable.
132 142
133See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this 143See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
134technique. 144technique.
135 145
136Please note that if your callback recursively invokes perl (e.g. for event 146Please note that if your callback recursively invokes perl (e.g. for event
141$idle = sub { 151$idle = sub {
142 require Carp; 152 require Carp;
143 Carp::croak ("FATAL: deadlock detected"); 153 Carp::croak ("FATAL: deadlock detected");
144}; 154};
145 155
146sub _cancel {
147 my ($self) = @_;
148
149 # free coroutine data and mark as destructed
150 $self->_destroy
151 or return;
152
153 # call all destruction callbacks
154 $_->(@{$self->{_status}})
155 for @{(delete $self->{_on_destroy}) || []};
156}
157
158# this coroutine is necessary because a coroutine 156# this coroutine is necessary because a coroutine
159# cannot destroy itself. 157# cannot destroy itself.
160my @destroy; 158our @destroy;
161my $manager; 159our $manager;
162 160
163$manager = new Coro sub { 161$manager = new Coro sub {
164 while () { 162 while () {
165 (shift @destroy)->_cancel 163 Coro::_cancel shift @destroy
166 while @destroy; 164 while @destroy;
167 165
168 &schedule; 166 &schedule;
169 } 167 }
170}; 168};
171$manager->desc ("[coro manager]"); 169$manager->{desc} = "[coro manager]";
172$manager->prio (PRIO_MAX); 170$manager->prio (PRIO_MAX);
173 171
174=back 172=back
175 173
176=head2 SIMPLE COROUTINE CREATION 174=head1 SIMPLE COROUTINE CREATION
177 175
178=over 4 176=over 4
179 177
180=item async { ... } [@args...] 178=item async { ... } [@args...]
181 179
182Create a new coroutine and return it's coroutine object (usually 180Create a new coroutine and return its coroutine object (usually
183unused). The coroutine will be put into the ready queue, so 181unused). The coroutine will be put into the ready queue, so
184it will start running automatically on the next scheduler run. 182it will start running automatically on the next scheduler run.
185 183
186The first argument is a codeblock/closure that should be executed in the 184The first argument is a codeblock/closure that should be executed in the
187coroutine. When it returns argument returns the coroutine is automatically 185coroutine. When it returns argument returns the coroutine is automatically
218Similar to C<async>, but uses a coroutine pool, so you should not call 216Similar to C<async>, but uses a coroutine pool, so you should not call
219terminate or join on it (although you are allowed to), and you get a 217terminate or join on it (although you are allowed to), and you get a
220coroutine that might have executed other code already (which can be good 218coroutine that might have executed other code already (which can be good
221or bad :). 219or bad :).
222 220
223On the plus side, this function is faster than creating (and destroying) 221On the plus side, this function is about twice as fast as creating (and
224a completely new coroutine, so if you need a lot of generic coroutines in 222destroying) a completely new coroutine, so if you need a lot of generic
225quick successsion, use C<async_pool>, not C<async>. 223coroutines in quick successsion, use C<async_pool>, not C<async>.
226 224
227The code block is executed in an C<eval> context and a warning will be 225The code block is executed in an C<eval> context and a warning will be
228issued in case of an exception instead of terminating the program, as 226issued in case of an exception instead of terminating the program, as
229C<async> does. As the coroutine is being reused, stuff like C<on_destroy> 227C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
230will not work in the expected way, unless you call terminate or cancel, 228will not work in the expected way, unless you call terminate or cancel,
233 231
234The priority will be reset to C<0> after each run, tracing will be 232The priority will be reset to C<0> after each run, tracing will be
235disabled, the description will be reset and the default output filehandle 233disabled, the description will be reset and the default output filehandle
236gets restored, so you can change all these. Otherwise the coroutine will 234gets restored, so you can change all these. Otherwise the coroutine will
237be re-used "as-is": most notably if you change other per-coroutine global 235be re-used "as-is": most notably if you change other per-coroutine global
238stuff such as C<$/> you I<must needs> to revert that change, which is most 236stuff such as C<$/> you I<must needs> revert that change, which is most
239simply done by using local as in: C< local $/ >. 237simply done by using local as in: C<< local $/ >>.
240 238
241The pool size is limited to C<8> idle coroutines (this can be adjusted by 239The idle pool size is limited to C<8> idle coroutines (this can be
242changing $Coro::POOL_SIZE), and there can be as many non-idle coros as 240adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
243required. 241coros as required.
244 242
245If you are concerned about pooled coroutines growing a lot because a 243If you are concerned about pooled coroutines growing a lot because a
246single C<async_pool> used a lot of stackspace you can e.g. C<async_pool 244single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
247{ terminate }> once per second or so to slowly replenish the pool. In 245{ terminate }> once per second or so to slowly replenish the pool. In
248addition to that, when the stacks used by a handler grows larger than 16kb 246addition to that, when the stacks used by a handler grows larger than 32kb
249(adjustable via $Coro::POOL_RSS) it will also be destroyed. 247(adjustable via $Coro::POOL_RSS) it will also be destroyed.
250 248
251=cut 249=cut
252 250
253our $POOL_SIZE = 8; 251our $POOL_SIZE = 8;
254our $POOL_RSS = 16 * 1024; 252our $POOL_RSS = 32 * 1024;
255our @async_pool; 253our @async_pool;
256 254
257sub pool_handler { 255sub pool_handler {
258 my $cb;
259
260 while () { 256 while () {
261 eval { 257 eval {
262 while () { 258 &{&_pool_handler} while 1;
263 _pool_1 $cb;
264 &$cb;
265 _pool_2 $cb;
266 &schedule;
267 }
268 }; 259 };
269 260
270 last if $@ eq "\3async_pool terminate\2\n";
271 warn $@ if $@; 261 warn $@ if $@;
272 } 262 }
273} 263}
274 264
275sub async_pool(&@) {
276 # this is also inlined into the unlock_scheduler
277 my $coro = (pop @async_pool) || new Coro \&pool_handler;
278
279 $coro->{_invoke} = [@_];
280 $coro->ready;
281
282 $coro
283}
284
285=back 265=back
286 266
287=head2 STATIC METHODS 267=head1 STATIC METHODS
288 268
289Static methods are actually functions that operate on the current coroutine. 269Static methods are actually functions that implicitly operate on the
270current coroutine.
290 271
291=over 4 272=over 4
292 273
293=item schedule 274=item schedule
294 275
306This makes C<schedule> I<the> generic method to use to block the current 287This makes C<schedule> I<the> generic method to use to block the current
307coroutine and wait for events: first you remember the current coroutine in 288coroutine and wait for events: first you remember the current coroutine in
308a variable, then arrange for some callback of yours to call C<< ->ready 289a variable, then arrange for some callback of yours to call C<< ->ready
309>> on that once some event happens, and last you call C<schedule> to put 290>> on that once some event happens, and last you call C<schedule> to put
310yourself to sleep. Note that a lot of things can wake your coroutine up, 291yourself to sleep. Note that a lot of things can wake your coroutine up,
311so you need to check wether the event indeed happened, e.g. by storing the 292so you need to check whether the event indeed happened, e.g. by storing the
312status in a variable. 293status in a variable.
313 294
314The canonical way to wait on external events is this: 295See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
315
316 {
317 # remember current coroutine
318 my $current = $Coro::current;
319
320 # register a hypothetical event handler
321 on_event_invoke sub {
322 # wake up sleeping coroutine
323 $current->ready;
324 undef $current;
325 };
326
327 # call schedule until event occurred.
328 # in case we are woken up for other reasons
329 # (current still defined), loop.
330 Coro::schedule while $current;
331 }
332 296
333=item cede 297=item cede
334 298
335"Cede" to other coroutines. This function puts the current coroutine into 299"Cede" to other coroutines. This function puts the current coroutine into
336the ready queue and calls C<schedule>, which has the effect of giving 300the ready queue and calls C<schedule>, which has the effect of giving
351Terminates the current coroutine with the given status values (see L<cancel>). 315Terminates the current coroutine with the given status values (see L<cancel>).
352 316
353=item killall 317=item killall
354 318
355Kills/terminates/cancels all coroutines except the currently running 319Kills/terminates/cancels all coroutines except the currently running
356one. This is useful after a fork, either in the child or the parent, as 320one. This can be useful after a fork, either in the child or the parent,
357usually only one of them should inherit the running coroutines. 321as usually only one of them should inherit the running coroutines.
322
323Note that in the implementation, destructors run as normal, making this
324function not so useful after a fork. Future versions of this function
325might try to free resources without running any code.
358 326
359Note that while this will try to free some of the main programs resources, 327Note that while this will try to free some of the main programs resources,
360you cnanot free all of them, so if a coroutine that is not the main 328you cannot free all of them, so if a coroutine that is not the main
361program calls this function, there will be some one-time resource leak. 329program calls this function, there will be some one-time resource leak.
362 330
363=cut 331=cut
364
365sub terminate {
366 $current->cancel (@_);
367}
368 332
369sub killall { 333sub killall {
370 for (Coro::State::list) { 334 for (Coro::State::list) {
371 $_->cancel 335 $_->cancel
372 if $_ != $current && UNIVERSAL::isa $_, "Coro"; 336 if $_ != $current && UNIVERSAL::isa $_, "Coro";
373 } 337 }
374} 338}
375 339
376=back 340=back
377 341
378=head2 COROUTINE METHODS 342=head1 COROUTINE OBJECT METHODS
379 343
380These are the methods you can call on coroutine objects (or to create 344These are the methods you can call on coroutine objects (or to create
381them). 345them).
382 346
383=over 4 347=over 4
392See C<async> and C<Coro::State::new> for additional info about the 356See C<async> and C<Coro::State::new> for additional info about the
393coroutine environment. 357coroutine environment.
394 358
395=cut 359=cut
396 360
397sub _run_coro { 361sub _coro_run {
398 terminate &{+shift}; 362 terminate &{+shift};
399}
400
401sub new {
402 my $class = shift;
403
404 $class->SUPER::new (\&_run_coro, @_)
405} 363}
406 364
407=item $success = $coroutine->ready 365=item $success = $coroutine->ready
408 366
409Put the given coroutine into the end of its ready queue (there is one 367Put the given coroutine into the end of its ready queue (there is one
414once all the coroutines of higher priority and all coroutines of the same 372once all the coroutines of higher priority and all coroutines of the same
415priority that were put into the ready queue earlier have been resumed. 373priority that were put into the ready queue earlier have been resumed.
416 374
417=item $is_ready = $coroutine->is_ready 375=item $is_ready = $coroutine->is_ready
418 376
419Return wether the coroutine is currently the ready queue or not, 377Return whether the coroutine is currently the ready queue or not,
420 378
421=item $coroutine->cancel (arg...) 379=item $coroutine->cancel (arg...)
422 380
423Terminates the given coroutine and makes it return the given arguments as 381Terminates the given coroutine and makes it return the given arguments as
424status (default: the empty list). Never returns if the coroutine is the 382status (default: the empty list). Never returns if the coroutine is the
426 384
427=cut 385=cut
428 386
429sub cancel { 387sub cancel {
430 my $self = shift; 388 my $self = shift;
431 $self->{_status} = [@_];
432 389
433 if ($current == $self) { 390 if ($current == $self) {
434 push @destroy, $self; 391 terminate @_;
435 $manager->ready;
436 &schedule while 1;
437 } else { 392 } else {
393 $self->{_status} = [@_];
438 $self->_cancel; 394 $self->_cancel;
439 } 395 }
440} 396}
397
398=item $coroutine->schedule_to
399
400Puts the current coroutine to sleep (like C<Coro::schedule>), but instead
401of continuing with the next coro from the ready queue, always switch to
402the given coroutine object (regardless of priority etc.). The readyness
403state of that coroutine isn't changed.
404
405This is an advanced method for special cases - I'd love to hear about any
406uses for this one.
407
408=item $coroutine->cede_to
409
410Like C<schedule_to>, but puts the current coroutine into the ready
411queue. This has the effect of temporarily switching to the given
412coroutine, and continuing some time later.
413
414This is an advanced method for special cases - I'd love to hear about any
415uses for this one.
416
417=item $coroutine->throw ([$scalar])
418
419If C<$throw> is specified and defined, it will be thrown as an exception
420inside the coroutine at the next convenient point in time. Otherwise
421clears the exception object.
422
423Coro will check for the exception each time a schedule-like-function
424returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
425>>, C<< Coro::Handle->readable >> and so on. Most of these functions
426detect this case and return early in case an exception is pending.
427
428The exception object will be thrown "as is" with the specified scalar in
429C<$@>, i.e. if it is a string, no line number or newline will be appended
430(unlike with C<die>).
431
432This can be used as a softer means than C<cancel> to ask a coroutine to
433end itself, although there is no guarantee that the exception will lead to
434termination, and if the exception isn't caught it might well end the whole
435program.
436
437You might also think of C<throw> as being the moral equivalent of
438C<kill>ing a coroutine with a signal (in this case, a scalar).
441 439
442=item $coroutine->join 440=item $coroutine->join
443 441
444Wait until the coroutine terminates and return any values given to the 442Wait until the coroutine terminates and return any values given to the
445C<terminate> or C<cancel> functions. C<join> can be called concurrently 443C<terminate> or C<cancel> functions. C<join> can be called concurrently
507higher values mean lower priority, just as in unix). 505higher values mean lower priority, just as in unix).
508 506
509=item $olddesc = $coroutine->desc ($newdesc) 507=item $olddesc = $coroutine->desc ($newdesc)
510 508
511Sets (or gets in case the argument is missing) the description for this 509Sets (or gets in case the argument is missing) the description for this
512coroutine. This is just a free-form string you can associate with a coroutine. 510coroutine. This is just a free-form string you can associate with a
511coroutine.
513 512
514This method simply sets the C<< $coroutine->{desc} >> member to the given string. You 513This method simply sets the C<< $coroutine->{desc} >> member to the given
515can modify this member directly if you wish. 514string. You can modify this member directly if you wish.
516
517=item $coroutine->throw ([$scalar])
518
519If C<$throw> is specified and defined, it will be thrown as an exception
520inside the coroutine at the next convinient point in time (usually after
521it gains control at the next schedule/transfer/cede). Otherwise clears the
522exception object.
523
524The exception object will be thrown "as is" with the specified scalar in
525C<$@>, i.e. if it is a string, no line number or newline will be appended
526(unlike with C<die>).
527
528This can be used as a softer means than C<cancel> to ask a coroutine to
529end itself, although there is no guarentee that the exception will lead to
530termination, and if the exception isn't caught it might well end the whole
531program.
532 515
533=cut 516=cut
534 517
535sub desc { 518sub desc {
536 my $old = $_[0]{desc}; 519 my $old = $_[0]{desc};
537 $_[0]{desc} = $_[1] if @_ > 1; 520 $_[0]{desc} = $_[1] if @_ > 1;
538 $old; 521 $old;
539} 522}
540 523
524sub transfer {
525 require Carp;
526 Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
527}
528
541=back 529=back
542 530
543=head2 GLOBAL FUNCTIONS 531=head1 GLOBAL FUNCTIONS
544 532
545=over 4 533=over 4
546 534
547=item Coro::nready 535=item Coro::nready
548 536
553would cause a deadlock unless there is an idle handler that wakes up some 541would cause a deadlock unless there is an idle handler that wakes up some
554coroutines. 542coroutines.
555 543
556=item my $guard = Coro::guard { ... } 544=item my $guard = Coro::guard { ... }
557 545
558This creates and returns a guard object. Nothing happens until the object 546This function still exists, but is deprecated. Please use the
559gets destroyed, in which case the codeblock given as argument will be 547C<Guard::guard> function instead.
560executed. This is useful to free locks or other resources in case of a
561runtime error or when the coroutine gets canceled, as in both cases the
562guard block will be executed. The guard object supports only one method,
563C<< ->cancel >>, which will keep the codeblock from being executed.
564 548
565Example: set some flag and clear it again when the coroutine gets canceled
566or the function returns:
567
568 sub do_something {
569 my $guard = Coro::guard { $busy = 0 };
570 $busy = 1;
571
572 # do something that requires $busy to be true
573 }
574
575=cut 549=cut
576 550
577sub guard(&) { 551BEGIN { *guard = \&Guard::guard }
578 bless \(my $cb = $_[0]), "Coro::guard"
579}
580
581sub Coro::guard::cancel {
582 ${$_[0]} = sub { };
583}
584
585sub Coro::guard::DESTROY {
586 ${$_[0]}->();
587}
588
589 552
590=item unblock_sub { ... } 553=item unblock_sub { ... }
591 554
592This utility function takes a BLOCK or code reference and "unblocks" it, 555This utility function takes a BLOCK or code reference and "unblocks" it,
593returning a new coderef. Unblocking means that calling the new coderef 556returning a new coderef. Unblocking means that calling the new coderef
595original code ref will be called (with parameters) from within another 558original code ref will be called (with parameters) from within another
596coroutine. 559coroutine.
597 560
598The reason this function exists is that many event libraries (such as the 561The reason this function exists is that many event libraries (such as the
599venerable L<Event|Event> module) are not coroutine-safe (a weaker form 562venerable L<Event|Event> module) are not coroutine-safe (a weaker form
600of thread-safety). This means you must not block within event callbacks, 563of reentrancy). This means you must not block within event callbacks,
601otherwise you might suffer from crashes or worse. The only event library 564otherwise you might suffer from crashes or worse. The only event library
602currently known that is safe to use without C<unblock_sub> is L<EV>. 565currently known that is safe to use without C<unblock_sub> is L<EV>.
603 566
604This function allows your callbacks to block by executing them in another 567This function allows your callbacks to block by executing them in another
605coroutine where it is safe to block. One example where blocking is handy 568coroutine where it is safe to block. One example where blocking is handy
610creating event callbacks that want to block. 573creating event callbacks that want to block.
611 574
612If your handler does not plan to block (e.g. simply sends a message to 575If your handler does not plan to block (e.g. simply sends a message to
613another coroutine, or puts some other coroutine into the ready queue), 576another coroutine, or puts some other coroutine into the ready queue),
614there is no reason to use C<unblock_sub>. 577there is no reason to use C<unblock_sub>.
578
579Note that you also need to use C<unblock_sub> for any other callbacks that
580are indirectly executed by any C-based event loop. For example, when you
581use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
582provides callbacks that are the result of some event callback, then you
583must not block either, or use C<unblock_sub>.
615 584
616=cut 585=cut
617 586
618our @unblock_queue; 587our @unblock_queue;
619 588
622# return immediately and can be reused) and because we cannot cede 591# return immediately and can be reused) and because we cannot cede
623# inside an event callback. 592# inside an event callback.
624our $unblock_scheduler = new Coro sub { 593our $unblock_scheduler = new Coro sub {
625 while () { 594 while () {
626 while (my $cb = pop @unblock_queue) { 595 while (my $cb = pop @unblock_queue) {
627 # this is an inlined copy of async_pool 596 &async_pool (@$cb);
628 my $coro = (pop @async_pool) || new Coro \&pool_handler;
629 597
630 $coro->{_invoke} = $cb;
631 $coro->ready;
632 cede; # for short-lived callbacks, this reduces pressure on the coro pool 598 # for short-lived callbacks, this reduces pressure on the coro pool
599 # as the chance is very high that the async_poll coro will be back
600 # in the idle state when cede returns
601 cede;
633 } 602 }
634 schedule; # sleep well 603 schedule; # sleep well
635 } 604 }
636}; 605};
637$unblock_scheduler->desc ("[unblock_sub scheduler]"); 606$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
638 607
639sub unblock_sub(&) { 608sub unblock_sub(&) {
640 my $cb = shift; 609 my $cb = shift;
641 610
642 sub { 611 sub {
643 unshift @unblock_queue, [$cb, @_]; 612 unshift @unblock_queue, [$cb, @_];
644 $unblock_scheduler->ready; 613 $unblock_scheduler->ready;
645 } 614 }
646} 615}
647 616
617=item $cb = Coro::rouse_cb
618
619Create and return a "rouse callback". That's a code reference that,
620when called, will remember a copy of its arguments and notify the owner
621coroutine of the callback.
622
623See the next function.
624
625=item @args = Coro::rouse_wait [$cb]
626
627Wait for the specified rouse callback (or the last one that was created in
628this coroutine).
629
630As soon as the callback is invoked (or when the callback was invoked
631before C<rouse_wait>), it will return the arguments originally passed to
632the rouse callback.
633
634See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
635
648=back 636=back
649 637
650=cut 638=cut
651 639
6521; 6401;
653 641
642=head1 HOW TO WAIT FOR A CALLBACK
643
644It is very common for a coroutine to wait for some callback to be
645called. This occurs naturally when you use coroutines in an otherwise
646event-based program, or when you use event-based libraries.
647
648These typically register a callback for some event, and call that callback
649when the event occured. In a coroutine, however, you typically want to
650just wait for the event, simplyifying things.
651
652For example C<< AnyEvent->child >> registers a callback to be called when
653a specific child has exited:
654
655 my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
656
657But from withina coroutine, you often just want to write this:
658
659 my $status = wait_for_child $pid;
660
661Coro offers two functions specifically designed to make this easy,
662C<Coro::rouse_cb> and C<Coro::rouse_wait>.
663
664The first function, C<rouse_cb>, generates and returns a callback that,
665when invoked, will save its arguments and notify the coroutine that
666created the callback.
667
668The second function, C<rouse_wait>, waits for the callback to be called
669(by calling C<schedule> to go to sleep) and returns the arguments
670originally passed to the callback.
671
672Using these functions, it becomes easy to write the C<wait_for_child>
673function mentioned above:
674
675 sub wait_for_child($) {
676 my ($pid) = @_;
677
678 my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
679
680 my ($rpid, $rstatus) = Coro::rouse_wait;
681 $rstatus
682 }
683
684In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
685you can roll your own, using C<schedule>:
686
687 sub wait_for_child($) {
688 my ($pid) = @_;
689
690 # store the current coroutine in $current,
691 # and provide result variables for the closure passed to ->child
692 my $current = $Coro::current;
693 my ($done, $rstatus);
694
695 # pass a closure to ->child
696 my $watcher = AnyEvent->child (pid => $pid, cb => sub {
697 $rstatus = $_[1]; # remember rstatus
698 $done = 1; # mark $rstatus as valud
699 });
700
701 # wait until the closure has been called
702 schedule while !$done;
703
704 $rstatus
705 }
706
707
654=head1 BUGS/LIMITATIONS 708=head1 BUGS/LIMITATIONS
655 709
710=over 4
711
712=item fork with pthread backend
713
714When Coro is compiled using the pthread backend (which isn't recommended
715but required on many BSDs as their libcs are completely broken), then
716coroutines will not survive a fork. There is no known workaround except to
717fix your libc and use a saner backend.
718
719=item perl process emulation ("threads")
720
656This module is not perl-pseudo-thread-safe. You should only ever use this 721This module is not perl-pseudo-thread-safe. You should only ever use this
657module from the same thread (this requirement might be removed in the 722module from the first thread (this requirement might be removed in the
658future to allow per-thread schedulers, but Coro::State does not yet allow 723future to allow per-thread schedulers, but Coro::State does not yet allow
659this). I recommend disabling thread support and using processes, as this 724this). I recommend disabling thread support and using processes, as having
660is much faster and uses less memory. 725the windows process emulation enabled under unix roughly halves perl
726performance, even when not used.
727
728=item coroutine switching not signal safe
729
730You must not switch to another coroutine from within a signal handler
731(only relevant with %SIG - most event libraries provide safe signals).
732
733That means you I<MUST NOT> call any function that might "block" the
734current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
735anything that calls those. Everything else, including calling C<ready>,
736works.
737
738=back
739
661 740
662=head1 SEE ALSO 741=head1 SEE ALSO
663 742
664Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. 743Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
665 744
666Debugging: L<Coro::Debug>. 745Debugging: L<Coro::Debug>.
667 746
668Support/Utility: L<Coro::Specific>, L<Coro::Util>. 747Support/Utility: L<Coro::Specific>, L<Coro::Util>.
669 748
670Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. 749Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
750L<Coro::SemaphoreSet>, L<Coro::RWLock>.
671 751
672IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>. 752I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
673 753
674Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>. 754Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
755a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
756L<Coro::Select>.
675 757
676XS API: L<Coro::MakeMaker>. 758XS API: L<Coro::MakeMaker>.
677 759
678Low level Configuration, Coroutine Environment: L<Coro::State>. 760Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
679 761
680=head1 AUTHOR 762=head1 AUTHOR
681 763
682 Marc Lehmann <schmorp@schmorp.de> 764 Marc Lehmann <schmorp@schmorp.de>
683 http://home.schmorp.de/ 765 http://home.schmorp.de/

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