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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 and for event-based programming, such as 36documentation). They are similar to kernel threads but don't (in general)
41multiple HTTP-GET requests running concurrently. See L<Coro::AnyEvent> to 37run in parallel at the same time even on SMP machines. The specific flavor
42learn more. 38of thread offered by this module also guarantees you that it will not
39switch between threads unless necessary, at easily-identified points in
40your program, so locking and parallel access are rarely an issue, making
41thread programming much safer and easier than using other thread models.
43 42
44Coroutines are also useful because Perl has no support for threads (the so 43Unlike the so-called "Perl threads" (which are not actually real threads
45called "threads" that perl offers are nothing more than the (bad) process 44but only the windows process emulation ported to unix), Coro provides a
46emulation coming from the Windows platform: On standard operating systems 45full shared address space, which makes communication between threads
47they serve no purpose whatsoever, except by making your programs slow and 46very easy. And threads are fast, too: disabling the Windows process
48making 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
49aks your software vendor/distributor to do it for you). 48four times speed increase for your programs.
50 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
51In this module, coroutines are defined as "callchain + lexical variables + 56In this module, a thread is defined as "callchain + lexical variables +
52@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain, 57@_ + $_ + $@ + $/ + C stack), that is, a thread has its own callchain,
53its 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
54variables (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.
55 63
56=cut 64=cut
57 65
58package Coro; 66package Coro;
59 67
60use strict; 68use strict qw(vars subs);
61no warnings "uninitialized"; 69no warnings "uninitialized";
70
71use Guard ();
62 72
63use Coro::State; 73use Coro::State;
64 74
65use base qw(Coro::State Exporter); 75use base qw(Coro::State Exporter);
66 76
67our $idle; # idle handler 77our $idle; # idle handler
68our $main; # main coroutine 78our $main; # main coroutine
69our $current; # current coroutine 79our $current; # current coroutine
70 80
71our $VERSION = 4.744; 81our $VERSION = 5.13;
72 82
73our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); 83our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
74our %EXPORT_TAGS = ( 84our %EXPORT_TAGS = (
75 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 85 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
76); 86);
77our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); 87our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
78 88
89=head1 GLOBAL VARIABLES
90
79=over 4 91=over 4
80 92
81=item $Coro::main 93=item $Coro::main
82 94
83This variable stores the coroutine object that represents the main 95This variable stores the coroutine object that represents the main
84program. While you cna C<ready> it and do most other things you can do to 96program. While you cna C<ready> it and do most other things you can do to
85coroutines, it is mainly useful to compare again C<$Coro::current>, to see 97coroutines, it is mainly useful to compare again C<$Coro::current>, to see
86wether you are running in the main program or not. 98whether you are running in the main program or not.
87 99
88=cut 100=cut
89 101
90$main = new Coro; 102# $main is now being initialised by Coro::State
91 103
92=item $Coro::current 104=item $Coro::current
93 105
94The coroutine object representing the current coroutine (the last 106The coroutine object representing the current coroutine (the last
95coroutine that the Coro scheduler switched to). The initial value is 107coroutine that the Coro scheduler switched to). The initial value is
96C<$main> (of course). 108C<$Coro::main> (of course).
97 109
98This variable is B<strictly> I<read-only>. You can take copies of the 110This variable is B<strictly> I<read-only>. You can take copies of the
99value stored in it and use it as any other coroutine object, but you must 111value stored in it and use it as any other coroutine object, but you must
100not otherwise modify the variable itself. 112not otherwise modify the variable itself.
101 113
102=cut 114=cut
103 115
104$main->{desc} = "[main::]";
105
106# maybe some other module used Coro::Specific before...
107$main->{_specific} = $current->{_specific}
108 if $current;
109
110_set_current $main;
111
112sub current() { $current } # [DEPRECATED] 116sub current() { $current } # [DEPRECATED]
113 117
114=item $Coro::idle 118=item $Coro::idle
115 119
116This 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
117usually 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
118pretty low-level functionality. 122pretty low-level functionality.
119 123
120This 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
121finds no ready coroutines to run. The default implementation prints 127ready coroutines to run. The default implementation prints "FATAL:
122"FATAL: deadlock detected" and exits, because the program has no other way 128deadlock detected" and exits, because the program has no other way to
123to continue. 129continue.
124 130
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
125This hook is overwritten by modules such as C<Coro::Timer> and 135This hook is overwritten by modules such as C<Coro::EV> and
126C<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
127coroutine so the scheduler can run it. 137coroutine so the scheduler can run it.
128 138
129Note that the callback I<must not>, under any circumstances, block 139Note that the callback I<must not>, under any circumstances, block
130the current coroutine. Normally, this is achieved by having an "idle 140the current coroutine. Normally, this is achieved by having an "idle
131coroutine" that calls the event loop and then blocks again, and then 141coroutine" that calls the event loop and then blocks again, and then
132readying that coroutine in the idle handler. 142readying that coroutine in the idle handler, or by simply placing the idle
143coroutine in this variable.
133 144
134See 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
135technique. 146technique.
136 147
137Please 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
142$idle = sub { 153$idle = sub {
143 require Carp; 154 require Carp;
144 Carp::croak ("FATAL: deadlock detected"); 155 Carp::croak ("FATAL: deadlock detected");
145}; 156};
146 157
147sub _cancel {
148 my ($self) = @_;
149
150 # free coroutine data and mark as destructed
151 $self->_destroy
152 or return;
153
154 # call all destruction callbacks
155 $_->(@{$self->{_status}})
156 for @{(delete $self->{_on_destroy}) || []};
157}
158
159# this coroutine is necessary because a coroutine 158# this coroutine is necessary because a coroutine
160# cannot destroy itself. 159# cannot destroy itself.
161my @destroy; 160our @destroy;
162my $manager; 161our $manager;
163 162
164$manager = new Coro sub { 163$manager = new Coro sub {
165 while () { 164 while () {
166 (shift @destroy)->_cancel 165 Coro::_cancel shift @destroy
167 while @destroy; 166 while @destroy;
168 167
169 &schedule; 168 &schedule;
170 } 169 }
171}; 170};
172$manager->desc ("[coro manager]"); 171$manager->{desc} = "[coro manager]";
173$manager->prio (PRIO_MAX); 172$manager->prio (PRIO_MAX);
174 173
175=back 174=back
176 175
177=head2 SIMPLE COROUTINE CREATION 176=head1 SIMPLE COROUTINE CREATION
178 177
179=over 4 178=over 4
180 179
181=item async { ... } [@args...] 180=item async { ... } [@args...]
182 181
183Create a new coroutine and return it's coroutine object (usually 182Create a new coroutine and return its coroutine object (usually
184unused). The coroutine will be put into the ready queue, so 183unused). The coroutine will be put into the ready queue, so
185it will start running automatically on the next scheduler run. 184it will start running automatically on the next scheduler run.
186 185
187The 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
188coroutine. When it returns argument returns the coroutine is automatically 187coroutine. When it returns argument returns the coroutine is automatically
219Similar 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
220terminate 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
221coroutine that might have executed other code already (which can be good 220coroutine that might have executed other code already (which can be good
222or bad :). 221or bad :).
223 222
224On 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
225a 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
226quick successsion, use C<async_pool>, not C<async>. 225coroutines in quick successsion, use C<async_pool>, not C<async>.
227 226
228The 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
229issued in case of an exception instead of terminating the program, as 228issued in case of an exception instead of terminating the program, as
230C<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>
231will 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,
234 233
235The 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
236disabled, the description will be reset and the default output filehandle 235disabled, the description will be reset and the default output filehandle
237gets restored, so you can change all these. Otherwise the coroutine will 236gets restored, so you can change all these. Otherwise the coroutine will
238be 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
239stuff 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
240simply done by using local as in: C< local $/ >. 239simply done by using local as in: C<< local $/ >>.
241 240
242The 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
243changing $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
244required. 243coros as required.
245 244
246If you are concerned about pooled coroutines growing a lot because a 245If you are concerned about pooled coroutines growing a lot because a
247single 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
248{ 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
249addition 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
250(adjustable via $Coro::POOL_RSS) it will also be destroyed. 249(adjustable via $Coro::POOL_RSS) it will also be destroyed.
251 250
252=cut 251=cut
253 252
254our $POOL_SIZE = 8; 253our $POOL_SIZE = 8;
255our $POOL_RSS = 16 * 1024; 254our $POOL_RSS = 32 * 1024;
256our @async_pool; 255our @async_pool;
257 256
258sub pool_handler { 257sub pool_handler {
259 my $cb;
260
261 while () { 258 while () {
262 eval { 259 eval {
263 while () { 260 &{&_pool_handler} while 1;
264 _pool_1 $cb;
265 &$cb;
266 _pool_2 $cb;
267 &schedule;
268 }
269 }; 261 };
270 262
271 if ($@) {
272 last if $@ eq "\3async_pool terminate\2\n";
273 warn $@; 263 warn $@ if $@;
274 }
275 } 264 }
276}
277
278sub async_pool(&@) {
279 # this is also inlined into the unlock_scheduler
280 my $coro = (pop @async_pool) || new Coro \&pool_handler;
281
282 $coro->{_invoke} = [@_];
283 $coro->ready;
284
285 $coro
286} 265}
287 266
288=back 267=back
289 268
290=head2 STATIC METHODS 269=head1 STATIC METHODS
291 270
292Static methods are actually functions that operate on the current coroutine. 271Static methods are actually functions that implicitly operate on the
272current coroutine.
293 273
294=over 4 274=over 4
295 275
296=item schedule 276=item schedule
297 277
309This 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
310coroutine and wait for events: first you remember the current coroutine in 290coroutine and wait for events: first you remember the current coroutine in
311a 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
312>> 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
313yourself 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,
314so 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
315status in a variable. 295status in a variable.
316 296
317The 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.
318
319 {
320 # remember current coroutine
321 my $current = $Coro::current;
322
323 # register a hypothetical event handler
324 on_event_invoke sub {
325 # wake up sleeping coroutine
326 $current->ready;
327 undef $current;
328 };
329
330 # call schedule until event occurred.
331 # in case we are woken up for other reasons
332 # (current still defined), loop.
333 Coro::schedule while $current;
334 }
335 298
336=item cede 299=item cede
337 300
338"Cede" to other coroutines. This function puts the current coroutine into 301"Cede" to other coroutines. This function puts the current coroutine into
339the 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
354Terminates the current coroutine with the given status values (see L<cancel>). 317Terminates the current coroutine with the given status values (see L<cancel>).
355 318
356=item killall 319=item killall
357 320
358Kills/terminates/cancels all coroutines except the currently running 321Kills/terminates/cancels all coroutines except the currently running
359one. 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,
360usually 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.
361 328
362Note 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,
363you 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
364program calls this function, there will be some one-time resource leak. 331program calls this function, there will be some one-time resource leak.
365 332
366=cut 333=cut
367
368sub terminate {
369 $current->cancel (@_);
370}
371 334
372sub killall { 335sub killall {
373 for (Coro::State::list) { 336 for (Coro::State::list) {
374 $_->cancel 337 $_->cancel
375 if $_ != $current && UNIVERSAL::isa $_, "Coro"; 338 if $_ != $current && UNIVERSAL::isa $_, "Coro";
376 } 339 }
377} 340}
378 341
379=back 342=back
380 343
381=head2 COROUTINE METHODS 344=head1 COROUTINE OBJECT METHODS
382 345
383These 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
384them). 347them).
385 348
386=over 4 349=over 4
395See 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
396coroutine environment. 359coroutine environment.
397 360
398=cut 361=cut
399 362
400sub _run_coro { 363sub _coro_run {
401 terminate &{+shift}; 364 terminate &{+shift};
402}
403
404sub new {
405 my $class = shift;
406
407 $class->SUPER::new (\&_run_coro, @_)
408} 365}
409 366
410=item $success = $coroutine->ready 367=item $success = $coroutine->ready
411 368
412Put 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
417once 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
418priority that were put into the ready queue earlier have been resumed. 375priority that were put into the ready queue earlier have been resumed.
419 376
420=item $is_ready = $coroutine->is_ready 377=item $is_ready = $coroutine->is_ready
421 378
422Return wether the coroutine is currently the ready queue or not, 379Return whether the coroutine is currently the ready queue or not,
423 380
424=item $coroutine->cancel (arg...) 381=item $coroutine->cancel (arg...)
425 382
426Terminates the given coroutine and makes it return the given arguments as 383Terminates the given coroutine and makes it return the given arguments as
427status (default: the empty list). Never returns if the coroutine is the 384status (default: the empty list). Never returns if the coroutine is the
429 386
430=cut 387=cut
431 388
432sub cancel { 389sub cancel {
433 my $self = shift; 390 my $self = shift;
434 $self->{_status} = [@_];
435 391
436 if ($current == $self) { 392 if ($current == $self) {
437 push @destroy, $self; 393 terminate @_;
438 $manager->ready;
439 &schedule while 1;
440 } else { 394 } else {
395 $self->{_status} = [@_];
441 $self->_cancel; 396 $self->_cancel;
442 } 397 }
443} 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).
444 441
445=item $coroutine->join 442=item $coroutine->join
446 443
447Wait until the coroutine terminates and return any values given to the 444Wait until the coroutine terminates and return any values given to the
448C<terminate> or C<cancel> functions. C<join> can be called concurrently 445C<terminate> or C<cancel> functions. C<join> can be called concurrently
510higher values mean lower priority, just as in unix). 507higher values mean lower priority, just as in unix).
511 508
512=item $olddesc = $coroutine->desc ($newdesc) 509=item $olddesc = $coroutine->desc ($newdesc)
513 510
514Sets (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
515coroutine. 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.
516 514
517This 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
518can modify this member directly if you wish. 516string. You can modify this member directly if you wish.
519
520=item $coroutine->throw ([$scalar])
521
522If C<$throw> is specified and defined, it will be thrown as an exception
523inside the coroutine at the next convinient point in time (usually after
524it gains control at the next schedule/transfer/cede). Otherwise clears the
525exception object.
526
527The exception object will be thrown "as is" with the specified scalar in
528C<$@>, i.e. if it is a string, no line number or newline will be appended
529(unlike with C<die>).
530
531This can be used as a softer means than C<cancel> to ask a coroutine to
532end itself, although there is no guarentee that the exception will lead to
533termination, and if the exception isn't caught it might well end the whole
534program.
535 517
536=cut 518=cut
537 519
538sub desc { 520sub desc {
539 my $old = $_[0]{desc}; 521 my $old = $_[0]{desc};
540 $_[0]{desc} = $_[1] if @_ > 1; 522 $_[0]{desc} = $_[1] if @_ > 1;
541 $old; 523 $old;
542} 524}
543 525
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
544=back 531=back
545 532
546=head2 GLOBAL FUNCTIONS 533=head1 GLOBAL FUNCTIONS
547 534
548=over 4 535=over 4
549 536
550=item Coro::nready 537=item Coro::nready
551 538
556would 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
557coroutines. 544coroutines.
558 545
559=item my $guard = Coro::guard { ... } 546=item my $guard = Coro::guard { ... }
560 547
561This creates and returns a guard object. Nothing happens until the object 548This function still exists, but is deprecated. Please use the
562gets destroyed, in which case the codeblock given as argument will be 549C<Guard::guard> function instead.
563executed. This is useful to free locks or other resources in case of a
564runtime error or when the coroutine gets canceled, as in both cases the
565guard block will be executed. The guard object supports only one method,
566C<< ->cancel >>, which will keep the codeblock from being executed.
567 550
568Example: set some flag and clear it again when the coroutine gets canceled
569or the function returns:
570
571 sub do_something {
572 my $guard = Coro::guard { $busy = 0 };
573 $busy = 1;
574
575 # do something that requires $busy to be true
576 }
577
578=cut 551=cut
579 552
580sub guard(&) { 553BEGIN { *guard = \&Guard::guard }
581 bless \(my $cb = $_[0]), "Coro::guard"
582}
583
584sub Coro::guard::cancel {
585 ${$_[0]} = sub { };
586}
587
588sub Coro::guard::DESTROY {
589 ${$_[0]}->();
590}
591
592 554
593=item unblock_sub { ... } 555=item unblock_sub { ... }
594 556
595This utility function takes a BLOCK or code reference and "unblocks" it, 557This utility function takes a BLOCK or code reference and "unblocks" it,
596returning a new coderef. Unblocking means that calling the new coderef 558returning a new coderef. Unblocking means that calling the new coderef
598original code ref will be called (with parameters) from within another 560original code ref will be called (with parameters) from within another
599coroutine. 561coroutine.
600 562
601The 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
602venerable L<Event|Event> module) are not coroutine-safe (a weaker form 564venerable L<Event|Event> module) are not coroutine-safe (a weaker form
603of thread-safety). This means you must not block within event callbacks, 565of reentrancy). This means you must not block within event callbacks,
604otherwise you might suffer from crashes or worse. The only event library 566otherwise you might suffer from crashes or worse. The only event library
605currently 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>.
606 568
607This function allows your callbacks to block by executing them in another 569This function allows your callbacks to block by executing them in another
608coroutine 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
631# return immediately and can be reused) and because we cannot cede 593# return immediately and can be reused) and because we cannot cede
632# inside an event callback. 594# inside an event callback.
633our $unblock_scheduler = new Coro sub { 595our $unblock_scheduler = new Coro sub {
634 while () { 596 while () {
635 while (my $cb = pop @unblock_queue) { 597 while (my $cb = pop @unblock_queue) {
636 # this is an inlined copy of async_pool 598 &async_pool (@$cb);
637 my $coro = (pop @async_pool) || new Coro \&pool_handler;
638 599
639 $coro->{_invoke} = $cb;
640 $coro->ready;
641 cede; # for short-lived callbacks, this reduces pressure on the coro pool 600 # for short-lived callbacks, this reduces pressure on the coro pool
601 # as the chance is very high that the async_poll coro will be back
602 # in the idle state when cede returns
603 cede;
642 } 604 }
643 schedule; # sleep well 605 schedule; # sleep well
644 } 606 }
645}; 607};
646$unblock_scheduler->desc ("[unblock_sub scheduler]"); 608$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
647 609
648sub unblock_sub(&) { 610sub unblock_sub(&) {
649 my $cb = shift; 611 my $cb = shift;
650 612
651 sub { 613 sub {
652 unshift @unblock_queue, [$cb, @_]; 614 unshift @unblock_queue, [$cb, @_];
653 $unblock_scheduler->ready; 615 $unblock_scheduler->ready;
654 } 616 }
655} 617}
656 618
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
657=back 638=back
658 639
659=cut 640=cut
660 641
6611; 6421;
662 643
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
663=head1 BUGS/LIMITATIONS 710=head1 BUGS/LIMITATIONS
664 711
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
665This 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
666module from the same thread (this requirement might be removed in the 724module from the first thread (this requirement might be removed in the
667future 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
668this). I recommend disabling thread support and using processes, as this 726this). I recommend disabling thread support and using processes, as having
669is 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
670 742
671=head1 SEE ALSO 743=head1 SEE ALSO
672 744
673Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. 745Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
674 746
675Debugging: L<Coro::Debug>. 747Debugging: L<Coro::Debug>.
676 748
677Support/Utility: L<Coro::Specific>, L<Coro::Util>. 749Support/Utility: L<Coro::Specific>, L<Coro::Util>.
678 750
679Locking/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>.
680 753
681IO/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>.
682 755
683Compatibility: 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>.
684 759
685XS API: L<Coro::MakeMaker>. 760XS API: L<Coro::MakeMaker>.
686 761
687Low level Configuration, Coroutine Environment: L<Coro::State>. 762Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
688 763
689=head1 AUTHOR 764=head1 AUTHOR
690 765
691 Marc Lehmann <schmorp@schmorp.de> 766 Marc Lehmann <schmorp@schmorp.de>
692 http://home.schmorp.de/ 767 http://home.schmorp.de/

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