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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 $VERSION = 5.12;
71 80
72our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); 81our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
73our %EXPORT_TAGS = ( 82our %EXPORT_TAGS = (
74 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 83 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
75); 84);
76our @EXPORT_OK = (@{$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
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 is useful after a fork, either in the child or the parent, as
357usually only one of them should inherit the running coroutines. 321usually only one of them should inherit the running coroutines.
358 322
359Note that while this will try to free some of the main programs resources, 323Note 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 324you 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. 325program calls this function, there will be some one-time resource leak.
362 326
363=cut 327=cut
364
365sub terminate {
366 $current->cancel (@_);
367}
368 328
369sub killall { 329sub killall {
370 for (Coro::State::list) { 330 for (Coro::State::list) {
371 $_->cancel 331 $_->cancel
372 if $_ != $current && UNIVERSAL::isa $_, "Coro"; 332 if $_ != $current && UNIVERSAL::isa $_, "Coro";
373 } 333 }
374} 334}
375 335
376=back 336=back
377 337
378=head2 COROUTINE METHODS 338=head1 COROUTINE OBJECT METHODS
379 339
380These are the methods you can call on coroutine objects (or to create 340These are the methods you can call on coroutine objects (or to create
381them). 341them).
382 342
383=over 4 343=over 4
392See C<async> and C<Coro::State::new> for additional info about the 352See C<async> and C<Coro::State::new> for additional info about the
393coroutine environment. 353coroutine environment.
394 354
395=cut 355=cut
396 356
397sub _run_coro { 357sub _coro_run {
398 terminate &{+shift}; 358 terminate &{+shift};
399}
400
401sub new {
402 my $class = shift;
403
404 $class->SUPER::new (\&_run_coro, @_)
405} 359}
406 360
407=item $success = $coroutine->ready 361=item $success = $coroutine->ready
408 362
409Put the given coroutine into the end of its ready queue (there is one 363Put 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 368once all the coroutines of higher priority and all coroutines of the same
415priority that were put into the ready queue earlier have been resumed. 369priority that were put into the ready queue earlier have been resumed.
416 370
417=item $is_ready = $coroutine->is_ready 371=item $is_ready = $coroutine->is_ready
418 372
419Return wether the coroutine is currently the ready queue or not, 373Return whether the coroutine is currently the ready queue or not,
420 374
421=item $coroutine->cancel (arg...) 375=item $coroutine->cancel (arg...)
422 376
423Terminates the given coroutine and makes it return the given arguments as 377Terminates the given coroutine and makes it return the given arguments as
424status (default: the empty list). Never returns if the coroutine is the 378status (default: the empty list). Never returns if the coroutine is the
426 380
427=cut 381=cut
428 382
429sub cancel { 383sub cancel {
430 my $self = shift; 384 my $self = shift;
431 $self->{_status} = [@_];
432 385
433 if ($current == $self) { 386 if ($current == $self) {
434 push @destroy, $self; 387 terminate @_;
435 $manager->ready;
436 &schedule while 1;
437 } else { 388 } else {
389 $self->{_status} = [@_];
438 $self->_cancel; 390 $self->_cancel;
439 } 391 }
440} 392}
393
394=item $coroutine->schedule_to
395
396Puts the current coroutine to sleep (like C<Coro::schedule>), but instead
397of continuing with the next coro from the ready queue, always switch to
398the given coroutine object (regardless of priority etc.). The readyness
399state of that coroutine isn't changed.
400
401This is an advanced method for special cases - I'd love to hear about any
402uses for this one.
403
404=item $coroutine->cede_to
405
406Like C<schedule_to>, but puts the current coroutine into the ready
407queue. This has the effect of temporarily switching to the given
408coroutine, and continuing some time later.
409
410This is an advanced method for special cases - I'd love to hear about any
411uses for this one.
412
413=item $coroutine->throw ([$scalar])
414
415If C<$throw> is specified and defined, it will be thrown as an exception
416inside the coroutine at the next convenient point in time. Otherwise
417clears the exception object.
418
419Coro will check for the exception each time a schedule-like-function
420returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
421>>, C<< Coro::Handle->readable >> and so on. Most of these functions
422detect this case and return early in case an exception is pending.
423
424The exception object will be thrown "as is" with the specified scalar in
425C<$@>, i.e. if it is a string, no line number or newline will be appended
426(unlike with C<die>).
427
428This can be used as a softer means than C<cancel> to ask a coroutine to
429end itself, although there is no guarantee that the exception will lead to
430termination, and if the exception isn't caught it might well end the whole
431program.
432
433You might also think of C<throw> as being the moral equivalent of
434C<kill>ing a coroutine with a signal (in this case, a scalar).
441 435
442=item $coroutine->join 436=item $coroutine->join
443 437
444Wait until the coroutine terminates and return any values given to the 438Wait until the coroutine terminates and return any values given to the
445C<terminate> or C<cancel> functions. C<join> can be called concurrently 439C<terminate> or C<cancel> functions. C<join> can be called concurrently
507higher values mean lower priority, just as in unix). 501higher values mean lower priority, just as in unix).
508 502
509=item $olddesc = $coroutine->desc ($newdesc) 503=item $olddesc = $coroutine->desc ($newdesc)
510 504
511Sets (or gets in case the argument is missing) the description for this 505Sets (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. 506coroutine. This is just a free-form string you can associate with a
507coroutine.
513 508
514This method simply sets the C<< $coroutine->{desc} >> member to the given string. You 509This method simply sets the C<< $coroutine->{desc} >> member to the given
515can modify this member directly if you wish. 510string. 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.
532 511
533=cut 512=cut
534 513
535sub desc { 514sub desc {
536 my $old = $_[0]{desc}; 515 my $old = $_[0]{desc};
537 $_[0]{desc} = $_[1] if @_ > 1; 516 $_[0]{desc} = $_[1] if @_ > 1;
538 $old; 517 $old;
539} 518}
540 519
520sub transfer {
521 require Carp;
522 Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
523}
524
541=back 525=back
542 526
543=head2 GLOBAL FUNCTIONS 527=head1 GLOBAL FUNCTIONS
544 528
545=over 4 529=over 4
546 530
547=item Coro::nready 531=item Coro::nready
548 532
553would cause a deadlock unless there is an idle handler that wakes up some 537would cause a deadlock unless there is an idle handler that wakes up some
554coroutines. 538coroutines.
555 539
556=item my $guard = Coro::guard { ... } 540=item my $guard = Coro::guard { ... }
557 541
558This creates and returns a guard object. Nothing happens until the object 542This function still exists, but is deprecated. Please use the
559gets destroyed, in which case the codeblock given as argument will be 543C<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.
564 544
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 545=cut
576 546
577sub guard(&) { 547BEGIN { *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
589 548
590=item unblock_sub { ... } 549=item unblock_sub { ... }
591 550
592This utility function takes a BLOCK or code reference and "unblocks" it, 551This utility function takes a BLOCK or code reference and "unblocks" it,
593returning a new coderef. Unblocking means that calling the new coderef 552returning a new coderef. Unblocking means that calling the new coderef
595original code ref will be called (with parameters) from within another 554original code ref will be called (with parameters) from within another
596coroutine. 555coroutine.
597 556
598The reason this function exists is that many event libraries (such as the 557The reason this function exists is that many event libraries (such as the
599venerable L<Event|Event> module) are not coroutine-safe (a weaker form 558venerable L<Event|Event> module) are not coroutine-safe (a weaker form
600of thread-safety). This means you must not block within event callbacks, 559of reentrancy). This means you must not block within event callbacks,
601otherwise you might suffer from crashes or worse. The only event library 560otherwise 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>. 561currently known that is safe to use without C<unblock_sub> is L<EV>.
603 562
604This function allows your callbacks to block by executing them in another 563This function allows your callbacks to block by executing them in another
605coroutine where it is safe to block. One example where blocking is handy 564coroutine where it is safe to block. One example where blocking is handy
610creating event callbacks that want to block. 569creating event callbacks that want to block.
611 570
612If your handler does not plan to block (e.g. simply sends a message to 571If 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), 572another coroutine, or puts some other coroutine into the ready queue),
614there is no reason to use C<unblock_sub>. 573there is no reason to use C<unblock_sub>.
574
575Note that you also need to use C<unblock_sub> for any other callbacks that
576are indirectly executed by any C-based event loop. For example, when you
577use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
578provides callbacks that are the result of some event callback, then you
579must not block either, or use C<unblock_sub>.
615 580
616=cut 581=cut
617 582
618our @unblock_queue; 583our @unblock_queue;
619 584
622# return immediately and can be reused) and because we cannot cede 587# return immediately and can be reused) and because we cannot cede
623# inside an event callback. 588# inside an event callback.
624our $unblock_scheduler = new Coro sub { 589our $unblock_scheduler = new Coro sub {
625 while () { 590 while () {
626 while (my $cb = pop @unblock_queue) { 591 while (my $cb = pop @unblock_queue) {
627 # this is an inlined copy of async_pool 592 &async_pool (@$cb);
628 my $coro = (pop @async_pool) || new Coro \&pool_handler;
629 593
630 $coro->{_invoke} = $cb;
631 $coro->ready;
632 cede; # for short-lived callbacks, this reduces pressure on the coro pool 594 # for short-lived callbacks, this reduces pressure on the coro pool
595 # as the chance is very high that the async_poll coro will be back
596 # in the idle state when cede returns
597 cede;
633 } 598 }
634 schedule; # sleep well 599 schedule; # sleep well
635 } 600 }
636}; 601};
637$unblock_scheduler->desc ("[unblock_sub scheduler]"); 602$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
638 603
639sub unblock_sub(&) { 604sub unblock_sub(&) {
640 my $cb = shift; 605 my $cb = shift;
641 606
642 sub { 607 sub {
643 unshift @unblock_queue, [$cb, @_]; 608 unshift @unblock_queue, [$cb, @_];
644 $unblock_scheduler->ready; 609 $unblock_scheduler->ready;
645 } 610 }
646} 611}
647 612
613=item $cb = Coro::rouse_cb
614
615Create and return a "rouse callback". That's a code reference that,
616when called, will remember a copy of its arguments and notify the owner
617coroutine of the callback.
618
619See the next function.
620
621=item @args = Coro::rouse_wait [$cb]
622
623Wait for the specified rouse callback (or the last one that was created in
624this coroutine).
625
626As soon as the callback is invoked (or when the callback was invoked
627before C<rouse_wait>), it will return the arguments originally passed to
628the rouse callback.
629
630See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
631
648=back 632=back
649 633
650=cut 634=cut
651 635
6521; 6361;
653 637
638=head1 HOW TO WAIT FOR A CALLBACK
639
640It is very common for a coroutine to wait for some callback to be
641called. This occurs naturally when you use coroutines in an otherwise
642event-based program, or when you use event-based libraries.
643
644These typically register a callback for some event, and call that callback
645when the event occured. In a coroutine, however, you typically want to
646just wait for the event, simplyifying things.
647
648For example C<< AnyEvent->child >> registers a callback to be called when
649a specific child has exited:
650
651 my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
652
653But from withina coroutine, you often just want to write this:
654
655 my $status = wait_for_child $pid;
656
657Coro offers two functions specifically designed to make this easy,
658C<Coro::rouse_cb> and C<Coro::rouse_wait>.
659
660The first function, C<rouse_cb>, generates and returns a callback that,
661when invoked, will save its arguments and notify the coroutine that
662created the callback.
663
664The second function, C<rouse_wait>, waits for the callback to be called
665(by calling C<schedule> to go to sleep) and returns the arguments
666originally passed to the callback.
667
668Using these functions, it becomes easy to write the C<wait_for_child>
669function mentioned above:
670
671 sub wait_for_child($) {
672 my ($pid) = @_;
673
674 my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
675
676 my ($rpid, $rstatus) = Coro::rouse_wait;
677 $rstatus
678 }
679
680In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
681you can roll your own, using C<schedule>:
682
683 sub wait_for_child($) {
684 my ($pid) = @_;
685
686 # store the current coroutine in $current,
687 # and provide result variables for the closure passed to ->child
688 my $current = $Coro::current;
689 my ($done, $rstatus);
690
691 # pass a closure to ->child
692 my $watcher = AnyEvent->child (pid => $pid, cb => sub {
693 $rstatus = $_[1]; # remember rstatus
694 $done = 1; # mark $rstatus as valud
695 });
696
697 # wait until the closure has been called
698 schedule while !$done;
699
700 $rstatus
701 }
702
703
654=head1 BUGS/LIMITATIONS 704=head1 BUGS/LIMITATIONS
655 705
706=over 4
707
708=item fork with pthread backend
709
710When Coro is compiled using the pthread backend (which isn't recommended
711but required on many BSDs as their libcs are completely broken), then
712coroutines will not survive a fork. There is no known workaround except to
713fix your libc and use a saner backend.
714
715=item perl process emulation ("threads")
716
656This module is not perl-pseudo-thread-safe. You should only ever use this 717This 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 718module from the first thread (this requirement might be removed in the
658future to allow per-thread schedulers, but Coro::State does not yet allow 719future to allow per-thread schedulers, but Coro::State does not yet allow
659this). I recommend disabling thread support and using processes, as this 720this). I recommend disabling thread support and using processes, as having
660is much faster and uses less memory. 721the windows process emulation enabled under unix roughly halves perl
722performance, even when not used.
723
724=item coroutine switching not signal safe
725
726You must not switch to another coroutine from within a signal handler
727(only relevant with %SIG - most event libraries provide safe signals).
728
729That means you I<MUST NOT> call any function that might "block" the
730current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
731anything that calls those. Everything else, including calling C<ready>,
732works.
733
734=back
735
661 736
662=head1 SEE ALSO 737=head1 SEE ALSO
663 738
664Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. 739Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
665 740
666Debugging: L<Coro::Debug>. 741Debugging: L<Coro::Debug>.
667 742
668Support/Utility: L<Coro::Specific>, L<Coro::Util>. 743Support/Utility: L<Coro::Specific>, L<Coro::Util>.
669 744
670Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. 745Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
746L<Coro::SemaphoreSet>, L<Coro::RWLock>.
671 747
672IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>. 748I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
673 749
674Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>. 750Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
751a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
752L<Coro::Select>.
675 753
676XS API: L<Coro::MakeMaker>. 754XS API: L<Coro::MakeMaker>.
677 755
678Low level Configuration, Coroutine Environment: L<Coro::State>. 756Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
679 757
680=head1 AUTHOR 758=head1 AUTHOR
681 759
682 Marc Lehmann <schmorp@schmorp.de> 760 Marc Lehmann <schmorp@schmorp.de>
683 http://home.schmorp.de/ 761 http://home.schmorp.de/

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