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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";
62 70
63use Coro::State; 71use Coro::State;
64 72
65use base qw(Coro::State Exporter); 73use base qw(Coro::State Exporter);
66 74
67our $idle; # idle handler 75our $idle; # idle handler
68our $main; # main coroutine 76our $main; # main coroutine
69our $current; # current coroutine 77our $current; # current coroutine
70 78
71our $VERSION = 4.742; 79our $VERSION = 5.13;
72 80
73our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); 81our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
74our %EXPORT_TAGS = ( 82our %EXPORT_TAGS = (
75 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 83 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
76); 84);
77our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); 85our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
78 86
87=head1 GLOBAL VARIABLES
88
79=over 4 89=over 4
80 90
81=item $Coro::main 91=item $Coro::main
82 92
83This variable stores the coroutine object that represents the main 93This variable stores the coroutine object that represents the main
84program. While you cna C<ready> it and do most other things you can do to 94program. While you cna C<ready> it and do most other things you can do to
85coroutines, it is mainly useful to compare again C<$Coro::current>, to see 95coroutines, it is mainly useful to compare again C<$Coro::current>, to see
86wether you are running in the main program or not. 96whether you are running in the main program or not.
87 97
88=cut 98=cut
89 99
90$main = new Coro; 100# $main is now being initialised by Coro::State
91 101
92=item $Coro::current 102=item $Coro::current
93 103
94The coroutine object representing the current coroutine (the last 104The coroutine object representing the current coroutine (the last
95coroutine that the Coro scheduler switched to). The initial value is 105coroutine that the Coro scheduler switched to). The initial value is
96C<$main> (of course). 106C<$Coro::main> (of course).
97 107
98This variable is B<strictly> I<read-only>. You can take copies of the 108This variable is B<strictly> I<read-only>. You can take copies of the
99value stored in it and use it as any other coroutine object, but you must 109value stored in it and use it as any other coroutine object, but you must
100not otherwise modify the variable itself. 110not otherwise modify the variable itself.
101 111
102=cut 112=cut
103 113
104$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] 114sub current() { $current } # [DEPRECATED]
113 115
114=item $Coro::idle 116=item $Coro::idle
115 117
116This 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
117usually 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
118pretty low-level functionality. 120pretty low-level functionality.
119 121
120This 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
121finds no ready coroutines to run. The default implementation prints 125ready coroutines to run. The default implementation prints "FATAL:
122"FATAL: deadlock detected" and exits, because the program has no other way 126deadlock detected" and exits, because the program has no other way to
123to continue. 127continue.
124 128
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
125This hook is overwritten by modules such as C<Coro::Timer> and 133This 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 134C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
127coroutine so the scheduler can run it. 135coroutine so the scheduler can run it.
128 136
129Note that the callback I<must not>, under any circumstances, block 137Note that the callback I<must not>, under any circumstances, block
130the current coroutine. Normally, this is achieved by having an "idle 138the current coroutine. Normally, this is achieved by having an "idle
131coroutine" that calls the event loop and then blocks again, and then 139coroutine" that calls the event loop and then blocks again, and then
132readying that coroutine in the idle handler. 140readying that coroutine in the idle handler, or by simply placing the idle
141coroutine in this variable.
133 142
134See 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
135technique. 144technique.
136 145
137Please 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
142$idle = sub { 151$idle = sub {
143 require Carp; 152 require Carp;
144 Carp::croak ("FATAL: deadlock detected"); 153 Carp::croak ("FATAL: deadlock detected");
145}; 154};
146 155
147sub _cancel {
148 my ($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 156# this coroutine is necessary because a coroutine
160# cannot destroy itself. 157# cannot destroy itself.
161my @destroy; 158our @destroy;
162my $manager; 159our $manager;
163 160
164$manager = new Coro sub { 161$manager = new Coro sub {
165 while () { 162 while () {
166 (shift @destroy)->_cancel 163 Coro::_cancel shift @destroy
167 while @destroy; 164 while @destroy;
168 165
169 &schedule; 166 &schedule;
170 } 167 }
171}; 168};
172$manager->desc ("[coro manager]"); 169$manager->{desc} = "[coro manager]";
173$manager->prio (PRIO_MAX); 170$manager->prio (PRIO_MAX);
174 171
175=back 172=back
176 173
177=head2 SIMPLE COROUTINE CREATION 174=head1 SIMPLE COROUTINE CREATION
178 175
179=over 4 176=over 4
180 177
181=item async { ... } [@args...] 178=item async { ... } [@args...]
182 179
183Create a new coroutine and return it's coroutine object (usually 180Create a new coroutine and return its coroutine object (usually
184unused). The coroutine will be put into the ready queue, so 181unused). The coroutine will be put into the ready queue, so
185it will start running automatically on the next scheduler run. 182it will start running automatically on the next scheduler run.
186 183
187The 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
188coroutine. When it returns argument returns the coroutine is automatically 185coroutine. When it returns argument returns the coroutine is automatically
219Similar 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
220terminate 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
221coroutine that might have executed other code already (which can be good 218coroutine that might have executed other code already (which can be good
222or bad :). 219or bad :).
223 220
224On 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
225a 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
226quick successsion, use C<async_pool>, not C<async>. 223coroutines in quick successsion, use C<async_pool>, not C<async>.
227 224
228The 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
229issued in case of an exception instead of terminating the program, as 226issued 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> 227C<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, 228will not work in the expected way, unless you call terminate or cancel,
234 231
235The 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
236disabled, the description will be reset and the default output filehandle 233disabled, the description will be reset and the default output filehandle
237gets restored, so you can change all these. Otherwise the coroutine will 234gets 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 235be 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 236stuff such as C<$/> you I<must needs> revert that change, which is most
240simply done by using local as in: C< local $/ >. 237simply done by using local as in: C<< local $/ >>.
241 238
242The 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
243changing $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
244required. 241coros as required.
245 242
246If you are concerned about pooled coroutines growing a lot because a 243If 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 244single 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 245{ 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 246addition to that, when the stacks used by a handler grows larger than 32kb
250(adjustable via $Coro::POOL_RSS) it will also be destroyed. 247(adjustable via $Coro::POOL_RSS) it will also be destroyed.
251 248
252=cut 249=cut
253 250
254our $POOL_SIZE = 8; 251our $POOL_SIZE = 8;
255our $POOL_RSS = 16 * 1024; 252our $POOL_RSS = 32 * 1024;
256our @async_pool; 253our @async_pool;
257 254
258sub pool_handler { 255sub pool_handler {
259 my $cb;
260
261 while () { 256 while () {
262 eval { 257 eval {
263 while () { 258 &{&_pool_handler} while 1;
264 _pool_1 $cb;
265 &$cb;
266 _pool_2 $cb;
267 &schedule;
268 }
269 }; 259 };
270 260
271 last if $@ eq "\3async_pool terminate\2\n";
272 warn $@ if $@; 261 warn $@ if $@;
273 } 262 }
274} 263}
275 264
276sub async_pool(&@) {
277 # this is also inlined into the unlock_scheduler
278 my $coro = (pop @async_pool) || new Coro \&pool_handler;
279
280 $coro->{_invoke} = [@_];
281 $coro->ready;
282
283 $coro
284}
285
286=back 265=back
287 266
288=head2 STATIC METHODS 267=head1 STATIC METHODS
289 268
290Static methods are actually functions that operate on the current coroutine. 269Static methods are actually functions that implicitly operate on the
270current coroutine.
291 271
292=over 4 272=over 4
293 273
294=item schedule 274=item schedule
295 275
307This 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
308coroutine and wait for events: first you remember the current coroutine in 288coroutine and wait for events: first you remember the current coroutine in
309a 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
310>> 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
311yourself 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,
312so 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
313status in a variable. 293status in a variable.
314 294
315The 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.
316
317 {
318 # remember current coroutine
319 my $current = $Coro::current;
320
321 # register a hypothetical event handler
322 on_event_invoke sub {
323 # wake up sleeping coroutine
324 $current->ready;
325 undef $current;
326 };
327
328 # call schedule until event occurred.
329 # in case we are woken up for other reasons
330 # (current still defined), loop.
331 Coro::schedule while $current;
332 }
333 296
334=item cede 297=item cede
335 298
336"Cede" to other coroutines. This function puts the current coroutine into 299"Cede" to other coroutines. This function puts the current coroutine into
337the 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
352Terminates the current coroutine with the given status values (see L<cancel>). 315Terminates the current coroutine with the given status values (see L<cancel>).
353 316
354=item killall 317=item killall
355 318
356Kills/terminates/cancels all coroutines except the currently running 319Kills/terminates/cancels all coroutines except the currently running
357one. This is useful after a fork, either in the child or the parent, as 320one. This can be useful after a fork, either in the child or the parent,
358usually only one of them should inherit the running coroutines. 321as usually only one of them should inherit the running coroutines.
322
323Note that in the implementation, destructors run as normal, making this
324function not so useful after a fork. Future versions of this function
325might try to free resources without running any code.
359 326
360Note that while this will try to free some of the main programs resources, 327Note that while this will try to free some of the main programs resources,
361you cnanot free all of them, so if a coroutine that is not the main 328you cannot free all of them, so if a coroutine that is not the main
362program calls this function, there will be some one-time resource leak. 329program calls this function, there will be some one-time resource leak.
363 330
364=cut 331=cut
365
366sub terminate {
367 $current->cancel (@_);
368}
369 332
370sub killall { 333sub killall {
371 for (Coro::State::list) { 334 for (Coro::State::list) {
372 $_->cancel 335 $_->cancel
373 if $_ != $current && UNIVERSAL::isa $_, "Coro"; 336 if $_ != $current && UNIVERSAL::isa $_, "Coro";
374 } 337 }
375} 338}
376 339
377=back 340=back
378 341
379=head2 COROUTINE METHODS 342=head1 COROUTINE OBJECT METHODS
380 343
381These are the methods you can call on coroutine objects (or to create 344These are the methods you can call on coroutine objects (or to create
382them). 345them).
383 346
384=over 4 347=over 4
393See C<async> and C<Coro::State::new> for additional info about the 356See C<async> and C<Coro::State::new> for additional info about the
394coroutine environment. 357coroutine environment.
395 358
396=cut 359=cut
397 360
398sub _run_coro { 361sub _coro_run {
399 terminate &{+shift}; 362 terminate &{+shift};
400}
401
402sub new {
403 my $class = shift;
404
405 $class->SUPER::new (\&_run_coro, @_)
406} 363}
407 364
408=item $success = $coroutine->ready 365=item $success = $coroutine->ready
409 366
410Put the given coroutine into the end of its ready queue (there is one 367Put the given coroutine into the end of its ready queue (there is one
415once all the coroutines of higher priority and all coroutines of the same 372once all the coroutines of higher priority and all coroutines of the same
416priority that were put into the ready queue earlier have been resumed. 373priority that were put into the ready queue earlier have been resumed.
417 374
418=item $is_ready = $coroutine->is_ready 375=item $is_ready = $coroutine->is_ready
419 376
420Return wether the coroutine is currently the ready queue or not, 377Return whether the coroutine is currently the ready queue or not,
421 378
422=item $coroutine->cancel (arg...) 379=item $coroutine->cancel (arg...)
423 380
424Terminates the given coroutine and makes it return the given arguments as 381Terminates the given coroutine and makes it return the given arguments as
425status (default: the empty list). Never returns if the coroutine is the 382status (default: the empty list). Never returns if the coroutine is the
427 384
428=cut 385=cut
429 386
430sub cancel { 387sub cancel {
431 my $self = shift; 388 my $self = shift;
432 $self->{_status} = [@_];
433 389
434 if ($current == $self) { 390 if ($current == $self) {
435 push @destroy, $self; 391 terminate @_;
436 $manager->ready;
437 &schedule while 1;
438 } else { 392 } else {
393 $self->{_status} = [@_];
439 $self->_cancel; 394 $self->_cancel;
440 } 395 }
441} 396}
397
398=item $coroutine->schedule_to
399
400Puts the current coroutine to sleep (like C<Coro::schedule>), but instead
401of continuing with the next coro from the ready queue, always switch to
402the given coroutine object (regardless of priority etc.). The readyness
403state of that coroutine isn't changed.
404
405This is an advanced method for special cases - I'd love to hear about any
406uses for this one.
407
408=item $coroutine->cede_to
409
410Like C<schedule_to>, but puts the current coroutine into the ready
411queue. This has the effect of temporarily switching to the given
412coroutine, and continuing some time later.
413
414This is an advanced method for special cases - I'd love to hear about any
415uses for this one.
416
417=item $coroutine->throw ([$scalar])
418
419If C<$throw> is specified and defined, it will be thrown as an exception
420inside the coroutine at the next convenient point in time. Otherwise
421clears the exception object.
422
423Coro will check for the exception each time a schedule-like-function
424returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
425>>, C<< Coro::Handle->readable >> and so on. Most of these functions
426detect this case and return early in case an exception is pending.
427
428The exception object will be thrown "as is" with the specified scalar in
429C<$@>, i.e. if it is a string, no line number or newline will be appended
430(unlike with C<die>).
431
432This can be used as a softer means than C<cancel> to ask a coroutine to
433end itself, although there is no guarantee that the exception will lead to
434termination, and if the exception isn't caught it might well end the whole
435program.
436
437You might also think of C<throw> as being the moral equivalent of
438C<kill>ing a coroutine with a signal (in this case, a scalar).
442 439
443=item $coroutine->join 440=item $coroutine->join
444 441
445Wait until the coroutine terminates and return any values given to the 442Wait until the coroutine terminates and return any values given to the
446C<terminate> or C<cancel> functions. C<join> can be called concurrently 443C<terminate> or C<cancel> functions. C<join> can be called concurrently
508higher values mean lower priority, just as in unix). 505higher values mean lower priority, just as in unix).
509 506
510=item $olddesc = $coroutine->desc ($newdesc) 507=item $olddesc = $coroutine->desc ($newdesc)
511 508
512Sets (or gets in case the argument is missing) the description for this 509Sets (or gets in case the argument is missing) the description for this
513coroutine. This is just a free-form string you can associate with a coroutine. 510coroutine. This is just a free-form string you can associate with a
511coroutine.
514 512
515This method simply sets the C<< $coroutine->{desc} >> member to the given string. You 513This method simply sets the C<< $coroutine->{desc} >> member to the given
516can modify this member directly if you wish. 514string. You can modify this member directly if you wish.
517
518=item $coroutine->throw ([$scalar])
519
520If C<$throw> is specified and defined, it will be thrown as an exception
521inside the coroutine at the next convinient point in time (usually after
522it gains control at the next schedule/transfer/cede). Otherwise clears the
523exception object.
524
525The exception object will be thrown "as is" with the specified scalar in
526C<$@>, i.e. if it is a string, no line number or newline will be appended
527(unlike with C<die>).
528
529This can be used as a softer means than C<cancel> to ask a coroutine to
530end itself, although there is no guarentee that the exception will lead to
531termination, and if the exception isn't caught it might well end the whole
532program.
533 515
534=cut 516=cut
535 517
536sub desc { 518sub desc {
537 my $old = $_[0]{desc}; 519 my $old = $_[0]{desc};
538 $_[0]{desc} = $_[1] if @_ > 1; 520 $_[0]{desc} = $_[1] if @_ > 1;
539 $old; 521 $old;
540} 522}
541 523
524sub transfer {
525 require Carp;
526 Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
527}
528
542=back 529=back
543 530
544=head2 GLOBAL FUNCTIONS 531=head1 GLOBAL FUNCTIONS
545 532
546=over 4 533=over 4
547 534
548=item Coro::nready 535=item Coro::nready
549 536
554would cause a deadlock unless there is an idle handler that wakes up some 541would cause a deadlock unless there is an idle handler that wakes up some
555coroutines. 542coroutines.
556 543
557=item my $guard = Coro::guard { ... } 544=item my $guard = Coro::guard { ... }
558 545
559This creates and returns a guard object. Nothing happens until the object 546This function still exists, but is deprecated. Please use the
560gets destroyed, in which case the codeblock given as argument will be 547C<Guard::guard> function instead.
561executed. This is useful to free locks or other resources in case of a
562runtime error or when the coroutine gets canceled, as in both cases the
563guard block will be executed. The guard object supports only one method,
564C<< ->cancel >>, which will keep the codeblock from being executed.
565 548
566Example: set some flag and clear it again when the coroutine gets canceled
567or the function returns:
568
569 sub do_something {
570 my $guard = Coro::guard { $busy = 0 };
571 $busy = 1;
572
573 # do something that requires $busy to be true
574 }
575
576=cut 549=cut
577 550
578sub guard(&) { 551BEGIN { *guard = \&Guard::guard }
579 bless \(my $cb = $_[0]), "Coro::guard"
580}
581
582sub Coro::guard::cancel {
583 ${$_[0]} = sub { };
584}
585
586sub Coro::guard::DESTROY {
587 ${$_[0]}->();
588}
589
590 552
591=item unblock_sub { ... } 553=item unblock_sub { ... }
592 554
593This utility function takes a BLOCK or code reference and "unblocks" it, 555This utility function takes a BLOCK or code reference and "unblocks" it,
594returning a new coderef. Unblocking means that calling the new coderef 556returning a new coderef. Unblocking means that calling the new coderef
596original code ref will be called (with parameters) from within another 558original code ref will be called (with parameters) from within another
597coroutine. 559coroutine.
598 560
599The reason this function exists is that many event libraries (such as the 561The reason this function exists is that many event libraries (such as the
600venerable L<Event|Event> module) are not coroutine-safe (a weaker form 562venerable L<Event|Event> module) are not coroutine-safe (a weaker form
601of thread-safety). This means you must not block within event callbacks, 563of reentrancy). This means you must not block within event callbacks,
602otherwise you might suffer from crashes or worse. The only event library 564otherwise you might suffer from crashes or worse. The only event library
603currently known that is safe to use without C<unblock_sub> is L<EV>. 565currently known that is safe to use without C<unblock_sub> is L<EV>.
604 566
605This function allows your callbacks to block by executing them in another 567This function allows your callbacks to block by executing them in another
606coroutine where it is safe to block. One example where blocking is handy 568coroutine where it is safe to block. One example where blocking is handy
629# return immediately and can be reused) and because we cannot cede 591# return immediately and can be reused) and because we cannot cede
630# inside an event callback. 592# inside an event callback.
631our $unblock_scheduler = new Coro sub { 593our $unblock_scheduler = new Coro sub {
632 while () { 594 while () {
633 while (my $cb = pop @unblock_queue) { 595 while (my $cb = pop @unblock_queue) {
634 # this is an inlined copy of async_pool 596 &async_pool (@$cb);
635 my $coro = (pop @async_pool) || new Coro \&pool_handler;
636 597
637 $coro->{_invoke} = $cb;
638 $coro->ready;
639 cede; # for short-lived callbacks, this reduces pressure on the coro pool 598 # for short-lived callbacks, this reduces pressure on the coro pool
599 # as the chance is very high that the async_poll coro will be back
600 # in the idle state when cede returns
601 cede;
640 } 602 }
641 schedule; # sleep well 603 schedule; # sleep well
642 } 604 }
643}; 605};
644$unblock_scheduler->desc ("[unblock_sub scheduler]"); 606$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
645 607
646sub unblock_sub(&) { 608sub unblock_sub(&) {
647 my $cb = shift; 609 my $cb = shift;
648 610
649 sub { 611 sub {
650 unshift @unblock_queue, [$cb, @_]; 612 unshift @unblock_queue, [$cb, @_];
651 $unblock_scheduler->ready; 613 $unblock_scheduler->ready;
652 } 614 }
653} 615}
654 616
617=item $cb = Coro::rouse_cb
618
619Create and return a "rouse callback". That's a code reference that,
620when called, will remember a copy of its arguments and notify the owner
621coroutine of the callback.
622
623See the next function.
624
625=item @args = Coro::rouse_wait [$cb]
626
627Wait for the specified rouse callback (or the last one that was created in
628this coroutine).
629
630As soon as the callback is invoked (or when the callback was invoked
631before C<rouse_wait>), it will return the arguments originally passed to
632the rouse callback.
633
634See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
635
655=back 636=back
656 637
657=cut 638=cut
658 639
6591; 6401;
660 641
642=head1 HOW TO WAIT FOR A CALLBACK
643
644It is very common for a coroutine to wait for some callback to be
645called. This occurs naturally when you use coroutines in an otherwise
646event-based program, or when you use event-based libraries.
647
648These typically register a callback for some event, and call that callback
649when the event occured. In a coroutine, however, you typically want to
650just wait for the event, simplyifying things.
651
652For example C<< AnyEvent->child >> registers a callback to be called when
653a specific child has exited:
654
655 my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
656
657But from withina coroutine, you often just want to write this:
658
659 my $status = wait_for_child $pid;
660
661Coro offers two functions specifically designed to make this easy,
662C<Coro::rouse_cb> and C<Coro::rouse_wait>.
663
664The first function, C<rouse_cb>, generates and returns a callback that,
665when invoked, will save its arguments and notify the coroutine that
666created the callback.
667
668The second function, C<rouse_wait>, waits for the callback to be called
669(by calling C<schedule> to go to sleep) and returns the arguments
670originally passed to the callback.
671
672Using these functions, it becomes easy to write the C<wait_for_child>
673function mentioned above:
674
675 sub wait_for_child($) {
676 my ($pid) = @_;
677
678 my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
679
680 my ($rpid, $rstatus) = Coro::rouse_wait;
681 $rstatus
682 }
683
684In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
685you can roll your own, using C<schedule>:
686
687 sub wait_for_child($) {
688 my ($pid) = @_;
689
690 # store the current coroutine in $current,
691 # and provide result variables for the closure passed to ->child
692 my $current = $Coro::current;
693 my ($done, $rstatus);
694
695 # pass a closure to ->child
696 my $watcher = AnyEvent->child (pid => $pid, cb => sub {
697 $rstatus = $_[1]; # remember rstatus
698 $done = 1; # mark $rstatus as valud
699 });
700
701 # wait until the closure has been called
702 schedule while !$done;
703
704 $rstatus
705 }
706
707
661=head1 BUGS/LIMITATIONS 708=head1 BUGS/LIMITATIONS
662 709
710=over 4
711
712=item fork with pthread backend
713
714When Coro is compiled using the pthread backend (which isn't recommended
715but required on many BSDs as their libcs are completely broken), then
716coroutines will not survive a fork. There is no known workaround except to
717fix your libc and use a saner backend.
718
719=item perl process emulation ("threads")
720
663This module is not perl-pseudo-thread-safe. You should only ever use this 721This module is not perl-pseudo-thread-safe. You should only ever use this
664module from the same thread (this requirement might be removed in the 722module from the first thread (this requirement might be removed in the
665future to allow per-thread schedulers, but Coro::State does not yet allow 723future to allow per-thread schedulers, but Coro::State does not yet allow
666this). I recommend disabling thread support and using processes, as this 724this). I recommend disabling thread support and using processes, as having
667is much faster and uses less memory. 725the windows process emulation enabled under unix roughly halves perl
726performance, even when not used.
727
728=item coroutine switching not signal safe
729
730You must not switch to another coroutine from within a signal handler
731(only relevant with %SIG - most event libraries provide safe signals).
732
733That means you I<MUST NOT> call any function that might "block" the
734current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
735anything that calls those. Everything else, including calling C<ready>,
736works.
737
738=back
739
668 740
669=head1 SEE ALSO 741=head1 SEE ALSO
670 742
671Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. 743Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
672 744
673Debugging: L<Coro::Debug>. 745Debugging: L<Coro::Debug>.
674 746
675Support/Utility: L<Coro::Specific>, L<Coro::Util>. 747Support/Utility: L<Coro::Specific>, L<Coro::Util>.
676 748
677Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. 749Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
750L<Coro::SemaphoreSet>, L<Coro::RWLock>.
678 751
679IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>. 752I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
680 753
681Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>. 754Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
755a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
756L<Coro::Select>.
682 757
683XS API: L<Coro::MakeMaker>. 758XS API: L<Coro::MakeMaker>.
684 759
685Low level Configuration, Coroutine Environment: L<Coro::State>. 760Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
686 761
687=head1 AUTHOR 762=head1 AUTHOR
688 763
689 Marc Lehmann <schmorp@schmorp.de> 764 Marc Lehmann <schmorp@schmorp.de>
690 http://home.schmorp.de/ 765 http://home.schmorp.de/

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