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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";
70
71use Guard ();
61 72
62use Coro::State; 73use Coro::State;
63 74
64use base qw(Coro::State Exporter); 75use base qw(Coro::State Exporter);
65 76
66our $idle; # idle handler 77our $idle; # idle handler
67our $main; # main coroutine 78our $main; # main coroutine
68our $current; # current coroutine 79our $current; # current coroutine
69 80
70our $VERSION = 4.6; 81our $VERSION = 5.13;
71 82
72our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); 83our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
73our %EXPORT_TAGS = ( 84our %EXPORT_TAGS = (
74 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 85 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
75); 86);
76our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); 87our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
77 88
89=head1 GLOBAL VARIABLES
90
78=over 4 91=over 4
79 92
80=item $Coro::main 93=item $Coro::main
81 94
82This variable stores the coroutine object that represents the main 95This variable stores the coroutine object that represents the main
83program. While you cna C<ready> it and do most other things you can do to 96program. While you cna C<ready> it and do most other things you can do to
84coroutines, it is mainly useful to compare again C<$Coro::current>, to see 97coroutines, it is mainly useful to compare again C<$Coro::current>, to see
85wether you are running in the main program or not. 98whether you are running in the main program or not.
86 99
87=cut 100=cut
88 101
89$main = new Coro; 102# $main is now being initialised by Coro::State
90 103
91=item $Coro::current 104=item $Coro::current
92 105
93The coroutine object representing the current coroutine (the last 106The coroutine object representing the current coroutine (the last
94coroutine that the Coro scheduler switched to). The initial value is 107coroutine that the Coro scheduler switched to). The initial value is
95C<$main> (of course). 108C<$Coro::main> (of course).
96 109
97This variable is B<strictly> I<read-only>. You can take copies of the 110This variable is B<strictly> I<read-only>. You can take copies of the
98value stored in it and use it as any other coroutine object, but you must 111value stored in it and use it as any other coroutine object, but you must
99not otherwise modify the variable itself. 112not otherwise modify the variable itself.
100 113
101=cut 114=cut
102 115
103$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] 116sub current() { $current } # [DEPRECATED]
112 117
113=item $Coro::idle 118=item $Coro::idle
114 119
115This 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
116usually 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
117pretty low-level functionality. 122pretty low-level functionality.
118 123
119This 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
120finds no ready coroutines to run. The default implementation prints 127ready coroutines to run. The default implementation prints "FATAL:
121"FATAL: deadlock detected" and exits, because the program has no other way 128deadlock detected" and exits, because the program has no other way to
122to continue. 129continue.
123 130
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
124This hook is overwritten by modules such as C<Coro::Timer> and 135This 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 136C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
126coroutine so the scheduler can run it. 137coroutine so the scheduler can run it.
127 138
128Note that the callback I<must not>, under any circumstances, block 139Note that the callback I<must not>, under any circumstances, block
129the current coroutine. Normally, this is achieved by having an "idle 140the current coroutine. Normally, this is achieved by having an "idle
130coroutine" that calls the event loop and then blocks again, and then 141coroutine" that calls the event loop and then blocks again, and then
131readying that coroutine in the idle handler. 142readying that coroutine in the idle handler, or by simply placing the idle
143coroutine in this variable.
132 144
133See 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
134technique. 146technique.
135 147
136Please 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
141$idle = sub { 153$idle = sub {
142 require Carp; 154 require Carp;
143 Carp::croak ("FATAL: deadlock detected"); 155 Carp::croak ("FATAL: deadlock detected");
144}; 156};
145 157
146sub _cancel {
147 my ($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 158# this coroutine is necessary because a coroutine
159# cannot destroy itself. 159# cannot destroy itself.
160my @destroy; 160our @destroy;
161my $manager; 161our $manager;
162 162
163$manager = new Coro sub { 163$manager = new Coro sub {
164 while () { 164 while () {
165 (shift @destroy)->_cancel 165 Coro::_cancel shift @destroy
166 while @destroy; 166 while @destroy;
167 167
168 &schedule; 168 &schedule;
169 } 169 }
170}; 170};
171$manager->desc ("[coro manager]"); 171$manager->{desc} = "[coro manager]";
172$manager->prio (PRIO_MAX); 172$manager->prio (PRIO_MAX);
173 173
174=back 174=back
175 175
176=head2 SIMPLE COROUTINE CREATION 176=head1 SIMPLE COROUTINE CREATION
177 177
178=over 4 178=over 4
179 179
180=item async { ... } [@args...] 180=item async { ... } [@args...]
181 181
182Create a new coroutine and return it's coroutine object (usually 182Create a new coroutine and return its coroutine object (usually
183unused). The coroutine will be put into the ready queue, so 183unused). The coroutine will be put into the ready queue, so
184it will start running automatically on the next scheduler run. 184it will start running automatically on the next scheduler run.
185 185
186The 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
187coroutine. When it returns argument returns the coroutine is automatically 187coroutine. When it returns argument returns the coroutine is automatically
218Similar 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
219terminate 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
220coroutine that might have executed other code already (which can be good 220coroutine that might have executed other code already (which can be good
221or bad :). 221or bad :).
222 222
223On 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
224a 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
225quick successsion, use C<async_pool>, not C<async>. 225coroutines in quick successsion, use C<async_pool>, not C<async>.
226 226
227The 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
228issued in case of an exception instead of terminating the program, as 228issued 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> 229C<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, 230will not work in the expected way, unless you call terminate or cancel,
233 233
234The 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
235disabled, the description will be reset and the default output filehandle 235disabled, the description will be reset and the default output filehandle
236gets restored, so you can change all these. Otherwise the coroutine will 236gets 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 237be 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 238stuff such as C<$/> you I<must needs> revert that change, which is most
239simply done by using local as in: C< local $/ >. 239simply done by using local as in: C<< local $/ >>.
240 240
241The 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
242changing $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
243required. 243coros as required.
244 244
245If you are concerned about pooled coroutines growing a lot because a 245If 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 246single 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 247{ 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 248addition to that, when the stacks used by a handler grows larger than 32kb
249(adjustable via $Coro::POOL_RSS) it will also be destroyed. 249(adjustable via $Coro::POOL_RSS) it will also be destroyed.
250 250
251=cut 251=cut
252 252
253our $POOL_SIZE = 8; 253our $POOL_SIZE = 8;
254our $POOL_RSS = 16 * 1024; 254our $POOL_RSS = 32 * 1024;
255our @async_pool; 255our @async_pool;
256 256
257sub pool_handler { 257sub pool_handler {
258 my $cb;
259
260 while () { 258 while () {
261 eval { 259 eval {
262 while () { 260 &{&_pool_handler} while 1;
263 _pool_1 $cb;
264 &$cb;
265 _pool_2 $cb;
266 &schedule;
267 }
268 }; 261 };
269 262
270 last if $@ eq "\3async_pool terminate\2\n";
271 warn $@ if $@; 263 warn $@ if $@;
272 } 264 }
273} 265}
274 266
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 267=back
286 268
287=head2 STATIC METHODS 269=head1 STATIC METHODS
288 270
289Static methods are actually functions that operate on the current coroutine. 271Static methods are actually functions that implicitly operate on the
272current coroutine.
290 273
291=over 4 274=over 4
292 275
293=item schedule 276=item schedule
294 277
306This makes C<schedule> I<the> generic method to use to block the current 289This 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 290coroutine and wait for events: first you remember the current coroutine in
308a variable, then arrange for some callback of yours to call C<< ->ready 291a 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 292>> 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, 293yourself 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 294so you need to check whether the event indeed happened, e.g. by storing the
312status in a variable. 295status in a variable.
313 296
314The 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.
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 }
332 298
333=item cede 299=item cede
334 300
335"Cede" to other coroutines. This function puts the current coroutine into 301"Cede" to other coroutines. This function puts the current coroutine into
336the 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
351Terminates the current coroutine with the given status values (see L<cancel>). 317Terminates the current coroutine with the given status values (see L<cancel>).
352 318
353=item killall 319=item killall
354 320
355Kills/terminates/cancels all coroutines except the currently running 321Kills/terminates/cancels all coroutines except the currently running
356one. This is useful after a fork, either in the child or the parent, as 322one. This can be useful after a fork, either in the child or the parent,
357usually only one of them should inherit the running coroutines. 323as usually only one of them should inherit the running coroutines.
324
325Note that in the implementation, destructors run as normal, making this
326function not so useful after a fork. Future versions of this function
327might try to free resources without running any code.
358 328
359Note that while this will try to free some of the main programs resources, 329Note 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 330you 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. 331program calls this function, there will be some one-time resource leak.
362 332
363=cut 333=cut
364
365sub terminate {
366 $current->cancel (@_);
367}
368 334
369sub killall { 335sub killall {
370 for (Coro::State::list) { 336 for (Coro::State::list) {
371 $_->cancel 337 $_->cancel
372 if $_ != $current && UNIVERSAL::isa $_, "Coro"; 338 if $_ != $current && UNIVERSAL::isa $_, "Coro";
373 } 339 }
374} 340}
375 341
376=back 342=back
377 343
378=head2 COROUTINE METHODS 344=head1 COROUTINE OBJECT METHODS
379 345
380These are the methods you can call on coroutine objects (or to create 346These are the methods you can call on coroutine objects (or to create
381them). 347them).
382 348
383=over 4 349=over 4
392See C<async> and C<Coro::State::new> for additional info about the 358See C<async> and C<Coro::State::new> for additional info about the
393coroutine environment. 359coroutine environment.
394 360
395=cut 361=cut
396 362
397sub _run_coro { 363sub _coro_run {
398 terminate &{+shift}; 364 terminate &{+shift};
399}
400
401sub new {
402 my $class = shift;
403
404 $class->SUPER::new (\&_run_coro, @_)
405} 365}
406 366
407=item $success = $coroutine->ready 367=item $success = $coroutine->ready
408 368
409Put the given coroutine into the end of its ready queue (there is one 369Put 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 374once all the coroutines of higher priority and all coroutines of the same
415priority that were put into the ready queue earlier have been resumed. 375priority that were put into the ready queue earlier have been resumed.
416 376
417=item $is_ready = $coroutine->is_ready 377=item $is_ready = $coroutine->is_ready
418 378
419Return wether the coroutine is currently the ready queue or not, 379Return whether the coroutine is currently the ready queue or not,
420 380
421=item $coroutine->cancel (arg...) 381=item $coroutine->cancel (arg...)
422 382
423Terminates the given coroutine and makes it return the given arguments as 383Terminates the given coroutine and makes it return the given arguments as
424status (default: the empty list). Never returns if the coroutine is the 384status (default: the empty list). Never returns if the coroutine is the
426 386
427=cut 387=cut
428 388
429sub cancel { 389sub cancel {
430 my $self = shift; 390 my $self = shift;
431 $self->{_status} = [@_];
432 391
433 if ($current == $self) { 392 if ($current == $self) {
434 push @destroy, $self; 393 terminate @_;
435 $manager->ready;
436 &schedule while 1;
437 } else { 394 } else {
395 $self->{_status} = [@_];
438 $self->_cancel; 396 $self->_cancel;
439 } 397 }
440} 398}
399
400=item $coroutine->schedule_to
401
402Puts the current coroutine to sleep (like C<Coro::schedule>), but instead
403of continuing with the next coro from the ready queue, always switch to
404the given coroutine object (regardless of priority etc.). The readyness
405state of that coroutine isn't changed.
406
407This is an advanced method for special cases - I'd love to hear about any
408uses for this one.
409
410=item $coroutine->cede_to
411
412Like C<schedule_to>, but puts the current coroutine into the ready
413queue. This has the effect of temporarily switching to the given
414coroutine, and continuing some time later.
415
416This is an advanced method for special cases - I'd love to hear about any
417uses for this one.
418
419=item $coroutine->throw ([$scalar])
420
421If C<$throw> is specified and defined, it will be thrown as an exception
422inside the coroutine at the next convenient point in time. Otherwise
423clears the exception object.
424
425Coro will check for the exception each time a schedule-like-function
426returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
427>>, C<< Coro::Handle->readable >> and so on. Most of these functions
428detect this case and return early in case an exception is pending.
429
430The exception object will be thrown "as is" with the specified scalar in
431C<$@>, i.e. if it is a string, no line number or newline will be appended
432(unlike with C<die>).
433
434This can be used as a softer means than C<cancel> to ask a coroutine to
435end itself, although there is no guarantee that the exception will lead to
436termination, and if the exception isn't caught it might well end the whole
437program.
438
439You might also think of C<throw> as being the moral equivalent of
440C<kill>ing a coroutine with a signal (in this case, a scalar).
441 441
442=item $coroutine->join 442=item $coroutine->join
443 443
444Wait until the coroutine terminates and return any values given to the 444Wait until the coroutine terminates and return any values given to the
445C<terminate> or C<cancel> functions. C<join> can be called concurrently 445C<terminate> or C<cancel> functions. C<join> can be called concurrently
507higher values mean lower priority, just as in unix). 507higher values mean lower priority, just as in unix).
508 508
509=item $olddesc = $coroutine->desc ($newdesc) 509=item $olddesc = $coroutine->desc ($newdesc)
510 510
511Sets (or gets in case the argument is missing) the description for this 511Sets (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. 512coroutine. This is just a free-form string you can associate with a
513coroutine.
513 514
514This method simply sets the C<< $coroutine->{desc} >> member to the given string. You 515This method simply sets the C<< $coroutine->{desc} >> member to the given
515can modify this member directly if you wish. 516string. 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.
532 517
533=cut 518=cut
534 519
535sub desc { 520sub desc {
536 my $old = $_[0]{desc}; 521 my $old = $_[0]{desc};
537 $_[0]{desc} = $_[1] if @_ > 1; 522 $_[0]{desc} = $_[1] if @_ > 1;
538 $old; 523 $old;
539} 524}
540 525
526sub transfer {
527 require Carp;
528 Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
529}
530
541=back 531=back
542 532
543=head2 GLOBAL FUNCTIONS 533=head1 GLOBAL FUNCTIONS
544 534
545=over 4 535=over 4
546 536
547=item Coro::nready 537=item Coro::nready
548 538
553would cause a deadlock unless there is an idle handler that wakes up some 543would cause a deadlock unless there is an idle handler that wakes up some
554coroutines. 544coroutines.
555 545
556=item my $guard = Coro::guard { ... } 546=item my $guard = Coro::guard { ... }
557 547
558This creates and returns a guard object. Nothing happens until the object 548This function still exists, but is deprecated. Please use the
559gets destroyed, in which case the codeblock given as argument will be 549C<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.
564 550
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 551=cut
576 552
577sub guard(&) { 553BEGIN { *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
589 554
590=item unblock_sub { ... } 555=item unblock_sub { ... }
591 556
592This utility function takes a BLOCK or code reference and "unblocks" it, 557This utility function takes a BLOCK or code reference and "unblocks" it,
593returning a new coderef. Unblocking means that calling the new coderef 558returning a new coderef. Unblocking means that calling the new coderef
595original code ref will be called (with parameters) from within another 560original code ref will be called (with parameters) from within another
596coroutine. 561coroutine.
597 562
598The reason this function exists is that many event libraries (such as the 563The reason this function exists is that many event libraries (such as the
599venerable L<Event|Event> module) are not coroutine-safe (a weaker form 564venerable L<Event|Event> module) are not coroutine-safe (a weaker form
600of thread-safety). This means you must not block within event callbacks, 565of reentrancy). This means you must not block within event callbacks,
601otherwise you might suffer from crashes or worse. The only event library 566otherwise 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>. 567currently known that is safe to use without C<unblock_sub> is L<EV>.
603 568
604This function allows your callbacks to block by executing them in another 569This function allows your callbacks to block by executing them in another
605coroutine where it is safe to block. One example where blocking is handy 570coroutine where it is safe to block. One example where blocking is handy
610creating event callbacks that want to block. 575creating event callbacks that want to block.
611 576
612If your handler does not plan to block (e.g. simply sends a message to 577If 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), 578another coroutine, or puts some other coroutine into the ready queue),
614there is no reason to use C<unblock_sub>. 579there is no reason to use C<unblock_sub>.
580
581Note that you also need to use C<unblock_sub> for any other callbacks that
582are indirectly executed by any C-based event loop. For example, when you
583use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
584provides callbacks that are the result of some event callback, then you
585must not block either, or use C<unblock_sub>.
615 586
616=cut 587=cut
617 588
618our @unblock_queue; 589our @unblock_queue;
619 590
622# return immediately and can be reused) and because we cannot cede 593# return immediately and can be reused) and because we cannot cede
623# inside an event callback. 594# inside an event callback.
624our $unblock_scheduler = new Coro sub { 595our $unblock_scheduler = new Coro sub {
625 while () { 596 while () {
626 while (my $cb = pop @unblock_queue) { 597 while (my $cb = pop @unblock_queue) {
627 # this is an inlined copy of async_pool 598 &async_pool (@$cb);
628 my $coro = (pop @async_pool) || new Coro \&pool_handler;
629 599
630 $coro->{_invoke} = $cb;
631 $coro->ready;
632 cede; # for short-lived callbacks, this reduces pressure on the coro pool 600 # for short-lived callbacks, this reduces pressure on the coro pool
601 # as the chance is very high that the async_poll coro will be back
602 # in the idle state when cede returns
603 cede;
633 } 604 }
634 schedule; # sleep well 605 schedule; # sleep well
635 } 606 }
636}; 607};
637$unblock_scheduler->desc ("[unblock_sub scheduler]"); 608$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
638 609
639sub unblock_sub(&) { 610sub unblock_sub(&) {
640 my $cb = shift; 611 my $cb = shift;
641 612
642 sub { 613 sub {
643 unshift @unblock_queue, [$cb, @_]; 614 unshift @unblock_queue, [$cb, @_];
644 $unblock_scheduler->ready; 615 $unblock_scheduler->ready;
645 } 616 }
646} 617}
647 618
619=item $cb = Coro::rouse_cb
620
621Create and return a "rouse callback". That's a code reference that,
622when called, will remember a copy of its arguments and notify the owner
623coroutine of the callback.
624
625See the next function.
626
627=item @args = Coro::rouse_wait [$cb]
628
629Wait for the specified rouse callback (or the last one that was created in
630this coroutine).
631
632As soon as the callback is invoked (or when the callback was invoked
633before C<rouse_wait>), it will return the arguments originally passed to
634the rouse callback.
635
636See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
637
648=back 638=back
649 639
650=cut 640=cut
651 641
6521; 6421;
653 643
644=head1 HOW TO WAIT FOR A CALLBACK
645
646It is very common for a coroutine to wait for some callback to be
647called. This occurs naturally when you use coroutines in an otherwise
648event-based program, or when you use event-based libraries.
649
650These typically register a callback for some event, and call that callback
651when the event occured. In a coroutine, however, you typically want to
652just wait for the event, simplyifying things.
653
654For example C<< AnyEvent->child >> registers a callback to be called when
655a specific child has exited:
656
657 my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
658
659But from withina coroutine, you often just want to write this:
660
661 my $status = wait_for_child $pid;
662
663Coro offers two functions specifically designed to make this easy,
664C<Coro::rouse_cb> and C<Coro::rouse_wait>.
665
666The first function, C<rouse_cb>, generates and returns a callback that,
667when invoked, will save its arguments and notify the coroutine that
668created the callback.
669
670The second function, C<rouse_wait>, waits for the callback to be called
671(by calling C<schedule> to go to sleep) and returns the arguments
672originally passed to the callback.
673
674Using these functions, it becomes easy to write the C<wait_for_child>
675function mentioned above:
676
677 sub wait_for_child($) {
678 my ($pid) = @_;
679
680 my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
681
682 my ($rpid, $rstatus) = Coro::rouse_wait;
683 $rstatus
684 }
685
686In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
687you can roll your own, using C<schedule>:
688
689 sub wait_for_child($) {
690 my ($pid) = @_;
691
692 # store the current coroutine in $current,
693 # and provide result variables for the closure passed to ->child
694 my $current = $Coro::current;
695 my ($done, $rstatus);
696
697 # pass a closure to ->child
698 my $watcher = AnyEvent->child (pid => $pid, cb => sub {
699 $rstatus = $_[1]; # remember rstatus
700 $done = 1; # mark $rstatus as valud
701 });
702
703 # wait until the closure has been called
704 schedule while !$done;
705
706 $rstatus
707 }
708
709
654=head1 BUGS/LIMITATIONS 710=head1 BUGS/LIMITATIONS
655 711
712=over 4
713
714=item fork with pthread backend
715
716When Coro is compiled using the pthread backend (which isn't recommended
717but required on many BSDs as their libcs are completely broken), then
718coroutines will not survive a fork. There is no known workaround except to
719fix your libc and use a saner backend.
720
721=item perl process emulation ("threads")
722
656This module is not perl-pseudo-thread-safe. You should only ever use this 723This 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 724module from the first thread (this requirement might be removed in the
658future to allow per-thread schedulers, but Coro::State does not yet allow 725future to allow per-thread schedulers, but Coro::State does not yet allow
659this). I recommend disabling thread support and using processes, as this 726this). I recommend disabling thread support and using processes, as having
660is much faster and uses less memory. 727the windows process emulation enabled under unix roughly halves perl
728performance, even when not used.
729
730=item coroutine switching not signal safe
731
732You must not switch to another coroutine from within a signal handler
733(only relevant with %SIG - most event libraries provide safe signals).
734
735That means you I<MUST NOT> call any function that might "block" the
736current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
737anything that calls those. Everything else, including calling C<ready>,
738works.
739
740=back
741
661 742
662=head1 SEE ALSO 743=head1 SEE ALSO
663 744
664Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. 745Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
665 746
666Debugging: L<Coro::Debug>. 747Debugging: L<Coro::Debug>.
667 748
668Support/Utility: L<Coro::Specific>, L<Coro::Util>. 749Support/Utility: L<Coro::Specific>, L<Coro::Util>.
669 750
670Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. 751Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
752L<Coro::SemaphoreSet>, L<Coro::RWLock>.
671 753
672IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>. 754I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
673 755
674Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>. 756Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
757a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
758L<Coro::Select>.
675 759
676XS API: L<Coro::MakeMaker>. 760XS API: L<Coro::MakeMaker>.
677 761
678Low level Configuration, Coroutine Environment: L<Coro::State>. 762Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
679 763
680=head1 AUTHOR 764=head1 AUTHOR
681 765
682 Marc Lehmann <schmorp@schmorp.de> 766 Marc Lehmann <schmorp@schmorp.de>
683 http://home.schmorp.de/ 767 http://home.schmorp.de/

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