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Revision 1.178 by root, Thu Apr 17 22:33:10 2008 UTC vs.
Revision 1.226 by root, Wed Nov 19 16:01:32 2008 UTC

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2 2
3Coro - coroutine process abstraction 3Coro - coroutine process abstraction
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use Coro; 7 use Coro;
8 8
9 async { 9 async {
10 # some asynchronous thread of execution 10 # some asynchronous thread of execution
11 print "2\n"; 11 print "2\n";
12 cede; # yield back to main 12 cede; # yield back to main
13 print "4\n"; 13 print "4\n";
14 }; 14 };
15 print "1\n"; 15 print "1\n";
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 31This module collection manages coroutines. Coroutines are similar to
31to threads but don't run in parallel at the same time even on SMP 32threads but don't (in general) run in parallel at the same time even
32machines. The specific flavor of coroutine used in this module also 33on SMP machines. The specific flavor of coroutine used in this module
33guarantees you that it will not switch between coroutines unless 34also guarantees you that it will not switch between coroutines unless
34necessary, at easily-identified points in your program, so locking and 35necessary, at easily-identified points in your program, so locking and
35parallel access are rarely an issue, making coroutine programming much 36parallel access are rarely an issue, making coroutine programming much
36safer than threads programming. 37safer and easier than threads programming.
37 38
38(Perl, however, does not natively support real threads but instead does a 39Unlike a normal perl program, however, coroutines allow you to have
39very slow and memory-intensive emulation of processes using threads. This 40multiple running interpreters that share data, which is especially useful
40is a performance win on Windows machines, and a loss everywhere else). 41to code pseudo-parallel processes and for event-based programming, such as
42multiple HTTP-GET requests running concurrently. See L<Coro::AnyEvent> to
43learn more.
44
45Coroutines are also useful because Perl has no support for threads (the so
46called "threads" that perl offers are nothing more than the (bad) process
47emulation coming from the Windows platform: On standard operating systems
48they serve no purpose whatsoever, except by making your programs slow and
49making them use a lot of memory. Best disable them when building perl, or
50aks your software vendor/distributor to do it for you).
41 51
42In this module, coroutines are defined as "callchain + lexical variables + 52In this module, coroutines are defined as "callchain + lexical variables +
43@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain, 53@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
44its own set of lexicals and its own set of perls most important global 54its own set of lexicals and its own set of perls most important global
45variables (see L<Coro::State> for more configuration). 55variables (see L<Coro::State> for more configuration).
46 56
47=cut 57=cut
48 58
49package Coro; 59package Coro;
50 60
51use strict; 61use strict qw(vars subs);
52no warnings "uninitialized"; 62no warnings "uninitialized";
53 63
54use Coro::State; 64use Coro::State;
55 65
56use base qw(Coro::State Exporter); 66use base qw(Coro::State Exporter);
57 67
58our $idle; # idle handler 68our $idle; # idle handler
59our $main; # main coroutine 69our $main; # main coroutine
60our $current; # current coroutine 70our $current; # current coroutine
61 71
62our $VERSION = '4.51'; 72our $VERSION = 5.0;
63 73
64our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); 74our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
65our %EXPORT_TAGS = ( 75our %EXPORT_TAGS = (
66 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 76 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
67); 77);
68our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); 78our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
69 79
70{
71 my @async;
72 my $init;
73
74 # this way of handling attributes simply is NOT scalable ;()
75 sub import {
76 no strict 'refs';
77
78 Coro->export_to_level (1, @_);
79
80 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
81 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
82 my ($package, $ref) = (shift, shift);
83 my @attrs;
84 for (@_) {
85 if ($_ eq "Coro") {
86 push @async, $ref;
87 unless ($init++) {
88 eval q{
89 sub INIT {
90 &async(pop @async) while @async;
91 }
92 };
93 }
94 } else {
95 push @attrs, $_;
96 }
97 }
98 return $old ? $old->($package, $ref, @attrs) : @attrs;
99 };
100 }
101
102}
103
104=over 4 80=over 4
105 81
106=item $main 82=item $Coro::main
107 83
108This coroutine represents the main program. 84This variable stores the coroutine object that represents the main
85program. While you cna C<ready> it and do most other things you can do to
86coroutines, it is mainly useful to compare again C<$Coro::current>, to see
87whether you are running in the main program or not.
109 88
110=cut 89=cut
111 90
112$main = new Coro; 91# $main is now being initialised by Coro::State
113 92
114=item $current (or as function: current) 93=item $Coro::current
115 94
116The current coroutine (the last coroutine switched to). The initial value 95The coroutine object representing the current coroutine (the last
96coroutine that the Coro scheduler switched to). The initial value is
117is C<$main> (of course). 97C<$Coro::main> (of course).
118 98
119This variable is B<strictly> I<read-only>. It is provided for performance 99This variable is B<strictly> I<read-only>. You can take copies of the
120reasons. If performance is not essential you are encouraged to use the 100value stored in it and use it as any other coroutine object, but you must
121C<Coro::current> function instead. 101not otherwise modify the variable itself.
122 102
123=cut 103=cut
124 104
125$main->{desc} = "[main::]";
126
127# maybe some other module used Coro::Specific before...
128$main->{_specific} = $current->{_specific}
129 if $current;
130
131_set_current $main;
132
133sub current() { $current } 105sub current() { $current } # [DEPRECATED]
134 106
135=item $idle 107=item $Coro::idle
136 108
137A callback that is called whenever the scheduler finds no ready coroutines 109This variable is mainly useful to integrate Coro into event loops. It is
138to run. The default implementation prints "FATAL: deadlock detected" and 110usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is
139exits, because the program has no other way to continue. 111pretty low-level functionality.
112
113This variable stores a callback that is called whenever the scheduler
114finds no ready coroutines to run. The default implementation prints
115"FATAL: deadlock detected" and exits, because the program has no other way
116to continue.
140 117
141This hook is overwritten by modules such as C<Coro::Timer> and 118This hook is overwritten by modules such as C<Coro::Timer> and
142C<Coro::Event> to wait on an external event that hopefully wake up a 119C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
143coroutine so the scheduler can run it. 120coroutine so the scheduler can run it.
121
122Note that the callback I<must not>, under any circumstances, block
123the current coroutine. Normally, this is achieved by having an "idle
124coroutine" that calls the event loop and then blocks again, and then
125readying that coroutine in the idle handler.
126
127See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
128technique.
144 129
145Please note that if your callback recursively invokes perl (e.g. for event 130Please note that if your callback recursively invokes perl (e.g. for event
146handlers), then it must be prepared to be called recursively itself. 131handlers), then it must be prepared to be called recursively itself.
147 132
148=cut 133=cut
… …
159 $self->_destroy 144 $self->_destroy
160 or return; 145 or return;
161 146
162 # call all destruction callbacks 147 # call all destruction callbacks
163 $_->(@{$self->{_status}}) 148 $_->(@{$self->{_status}})
164 for @{(delete $self->{_on_destroy}) || []}; 149 for @{ delete $self->{_on_destroy} || [] };
165} 150}
166 151
167# this coroutine is necessary because a coroutine 152# this coroutine is necessary because a coroutine
168# cannot destroy itself. 153# cannot destroy itself.
169my @destroy; 154our @destroy;
170my $manager; 155our $manager;
171 156
172$manager = new Coro sub { 157$manager = new Coro sub {
173 while () { 158 while () {
174 (shift @destroy)->_cancel 159 (shift @destroy)->_cancel
175 while @destroy; 160 while @destroy;
176 161
177 &schedule; 162 &schedule;
178 } 163 }
179}; 164};
180$manager->desc ("[coro manager]"); 165$manager->{desc} = "[coro manager]";
181$manager->prio (PRIO_MAX); 166$manager->prio (PRIO_MAX);
182 167
183=back 168=back
184 169
185=head2 STATIC METHODS 170=head2 SIMPLE COROUTINE CREATION
186
187Static methods are actually functions that operate on the current coroutine only.
188 171
189=over 4 172=over 4
190 173
191=item async { ... } [@args...] 174=item async { ... } [@args...]
192 175
193Create a new asynchronous coroutine and return it's coroutine object 176Create a new coroutine and return it's coroutine object (usually
194(usually unused). When the sub returns the new coroutine is automatically 177unused). The coroutine will be put into the ready queue, so
178it will start running automatically on the next scheduler run.
179
180The first argument is a codeblock/closure that should be executed in the
181coroutine. When it returns argument returns the coroutine is automatically
195terminated. 182terminated.
196 183
184The remaining arguments are passed as arguments to the closure.
185
197See the C<Coro::State::new> constructor for info about the coroutine 186See the C<Coro::State::new> constructor for info about the coroutine
198environment in which coroutines run. 187environment in which coroutines are executed.
199 188
200Calling C<exit> in a coroutine will do the same as calling exit outside 189Calling C<exit> in a coroutine will do the same as calling exit outside
201the coroutine. Likewise, when the coroutine dies, the program will exit, 190the coroutine. Likewise, when the coroutine dies, the program will exit,
202just as it would in the main program. 191just as it would in the main program.
203 192
193If you do not want that, you can provide a default C<die> handler, or
194simply avoid dieing (by use of C<eval>).
195
204 # create a new coroutine that just prints its arguments 196Example: Create a new coroutine that just prints its arguments.
197
205 async { 198 async {
206 print "@_\n"; 199 print "@_\n";
207 } 1,2,3,4; 200 } 1,2,3,4;
208 201
209=cut 202=cut
… …
215} 208}
216 209
217=item async_pool { ... } [@args...] 210=item async_pool { ... } [@args...]
218 211
219Similar to C<async>, but uses a coroutine pool, so you should not call 212Similar to C<async>, but uses a coroutine pool, so you should not call
220terminate or join (although you are allowed to), and you get a coroutine 213terminate or join on it (although you are allowed to), and you get a
221that might have executed other code already (which can be good or bad :). 214coroutine that might have executed other code already (which can be good
215or bad :).
222 216
217On the plus side, this function is faster than creating (and destroying)
218a completly new coroutine, so if you need a lot of generic coroutines in
219quick successsion, use C<async_pool>, not C<async>.
220
223Also, the block is executed in an C<eval> context and a warning will be 221The code block is executed in an C<eval> context and a warning will be
224issued in case of an exception instead of terminating the program, as 222issued in case of an exception instead of terminating the program, as
225C<async> does. As the coroutine is being reused, stuff like C<on_destroy> 223C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
226will not work in the expected way, unless you call terminate or cancel, 224will not work in the expected way, unless you call terminate or cancel,
227which somehow defeats the purpose of pooling. 225which somehow defeats the purpose of pooling (but is fine in the
226exceptional case).
228 227
229The priority will be reset to C<0> after each job, tracing will be 228The priority will be reset to C<0> after each run, tracing will be
230disabled, the description will be reset and the default output filehandle 229disabled, the description will be reset and the default output filehandle
231gets restored, so you can change alkl these. Otherwise the coroutine will 230gets restored, so you can change all these. Otherwise the coroutine will
232be re-used "as-is": most notably if you change other per-coroutine global 231be re-used "as-is": most notably if you change other per-coroutine global
233stuff such as C<$/> you need to revert that change, which is most simply 232stuff such as C<$/> you I<must needs> revert that change, which is most
234done by using local as in C< local $/ >. 233simply done by using local as in: C<< local $/ >>.
235 234
236The pool size is limited to 8 idle coroutines (this can be adjusted by 235The idle pool size is limited to C<8> idle coroutines (this can be
237changing $Coro::POOL_SIZE), and there can be as many non-idle coros as 236adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
238required. 237coros as required.
239 238
240If you are concerned about pooled coroutines growing a lot because a 239If you are concerned about pooled coroutines growing a lot because a
241single C<async_pool> used a lot of stackspace you can e.g. C<async_pool 240single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
242{ terminate }> once per second or so to slowly replenish the pool. In 241{ terminate }> once per second or so to slowly replenish the pool. In
243addition to that, when the stacks used by a handler grows larger than 16kb 242addition to that, when the stacks used by a handler grows larger than 16kb
244(adjustable with $Coro::POOL_RSS) it will also exit. 243(adjustable via $Coro::POOL_RSS) it will also be destroyed.
245 244
246=cut 245=cut
247 246
248our $POOL_SIZE = 8; 247our $POOL_SIZE = 8;
249our $POOL_RSS = 16 * 1024; 248our $POOL_RSS = 16 * 1024;
… …
260 _pool_2 $cb; 259 _pool_2 $cb;
261 &schedule; 260 &schedule;
262 } 261 }
263 }; 262 };
264 263
264 if ($@) {
265 last if $@ eq "\3async_pool terminate\2\n"; 265 last if $@ eq "\3async_pool terminate\2\n";
266 warn $@ if $@; 266 warn $@;
267 }
267 } 268 }
268} 269}
269 270
270sub async_pool(&@) { 271sub async_pool(&@) {
271 # this is also inlined into the unlock_scheduler 272 # this is also inlined into the unblock_scheduler
272 my $coro = (pop @async_pool) || new Coro \&pool_handler; 273 my $coro = (pop @async_pool) || new Coro \&pool_handler;
273 274
274 $coro->{_invoke} = [@_]; 275 $coro->{_invoke} = [@_];
275 $coro->ready; 276 $coro->ready;
276 277
277 $coro 278 $coro
278} 279}
279 280
281=back
282
283=head2 STATIC METHODS
284
285Static methods are actually functions that operate on the current coroutine.
286
287=over 4
288
280=item schedule 289=item schedule
281 290
282Calls the scheduler. Please note that the current coroutine will not be put 291Calls the scheduler. The scheduler will find the next coroutine that is
292to be run from the ready queue and switches to it. The next coroutine
293to be run is simply the one with the highest priority that is longest
294in its ready queue. If there is no coroutine ready, it will clal the
295C<$Coro::idle> hook.
296
297Please note that the current coroutine will I<not> be put into the ready
283into the ready queue, so calling this function usually means you will 298queue, so calling this function usually means you will never be called
284never be called again unless something else (e.g. an event handler) calls 299again unless something else (e.g. an event handler) calls C<< ->ready >>,
285ready. 300thus waking you up.
286 301
287The canonical way to wait on external events is this: 302This makes C<schedule> I<the> generic method to use to block the current
303coroutine and wait for events: first you remember the current coroutine in
304a variable, then arrange for some callback of yours to call C<< ->ready
305>> on that once some event happens, and last you call C<schedule> to put
306yourself to sleep. Note that a lot of things can wake your coroutine up,
307so you need to check whether the event indeed happened, e.g. by storing the
308status in a variable.
288 309
289 { 310See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
290 # remember current coroutine
291 my $current = $Coro::current;
292
293 # register a hypothetical event handler
294 on_event_invoke sub {
295 # wake up sleeping coroutine
296 $current->ready;
297 undef $current;
298 };
299
300 # call schedule until event occurred.
301 # in case we are woken up for other reasons
302 # (current still defined), loop.
303 Coro::schedule while $current;
304 }
305 311
306=item cede 312=item cede
307 313
308"Cede" to other coroutines. This function puts the current coroutine into the 314"Cede" to other coroutines. This function puts the current coroutine into
309ready queue and calls C<schedule>, which has the effect of giving up the 315the ready queue and calls C<schedule>, which has the effect of giving
310current "timeslice" to other coroutines of the same or higher priority. 316up the current "timeslice" to other coroutines of the same or higher
317priority. Once your coroutine gets its turn again it will automatically be
318resumed.
319
320This function is often called C<yield> in other languages.
311 321
312=item Coro::cede_notself 322=item Coro::cede_notself
313 323
314Works like cede, but is not exported by default and will cede to any 324Works like cede, but is not exported by default and will cede to I<any>
315coroutine, regardless of priority, once. 325coroutine, regardless of priority. This is useful sometimes to ensure
326progress is made.
316 327
317=item terminate [arg...] 328=item terminate [arg...]
318 329
319Terminates the current coroutine with the given status values (see L<cancel>). 330Terminates the current coroutine with the given status values (see L<cancel>).
320 331
… …
322 333
323Kills/terminates/cancels all coroutines except the currently running 334Kills/terminates/cancels all coroutines except the currently running
324one. This is useful after a fork, either in the child or the parent, as 335one. This is useful after a fork, either in the child or the parent, as
325usually only one of them should inherit the running coroutines. 336usually only one of them should inherit the running coroutines.
326 337
338Note that while this will try to free some of the main programs resources,
339you cannot free all of them, so if a coroutine that is not the main
340program calls this function, there will be some one-time resource leak.
341
327=cut 342=cut
328 343
329sub terminate { 344sub terminate {
330 $current->cancel (@_); 345 $current->{_status} = [@_];
346 push @destroy, $current;
347 $manager->ready;
348 do { &schedule } while 1;
331} 349}
332 350
333sub killall { 351sub killall {
334 for (Coro::State::list) { 352 for (Coro::State::list) {
335 $_->cancel 353 $_->cancel
… …
339 357
340=back 358=back
341 359
342=head2 COROUTINE METHODS 360=head2 COROUTINE METHODS
343 361
344These are the methods you can call on coroutine objects. 362These are the methods you can call on coroutine objects (or to create
363them).
345 364
346=over 4 365=over 4
347 366
348=item new Coro \&sub [, @args...] 367=item new Coro \&sub [, @args...]
349 368
350Create a new coroutine and return it. When the sub returns the coroutine 369Create a new coroutine and return it. When the sub returns, the coroutine
351automatically terminates as if C<terminate> with the returned values were 370automatically terminates as if C<terminate> with the returned values were
352called. To make the coroutine run you must first put it into the ready queue 371called. To make the coroutine run you must first put it into the ready
353by calling the ready method. 372queue by calling the ready method.
354 373
355See C<async> and C<Coro::State::new> for additional info about the 374See C<async> and C<Coro::State::new> for additional info about the
356coroutine environment. 375coroutine environment.
357 376
358=cut 377=cut
359 378
360sub _run_coro { 379sub _terminate {
361 terminate &{+shift}; 380 terminate &{+shift};
362} 381}
363 382
364sub new {
365 my $class = shift;
366
367 $class->SUPER::new (\&_run_coro, @_)
368}
369
370=item $success = $coroutine->ready 383=item $success = $coroutine->ready
371 384
372Put the given coroutine into the ready queue (according to it's priority) 385Put the given coroutine into the end of its ready queue (there is one
373and return true. If the coroutine is already in the ready queue, do nothing 386queue for each priority) and return true. If the coroutine is already in
374and return false. 387the ready queue, do nothing and return false.
388
389This ensures that the scheduler will resume this coroutine automatically
390once all the coroutines of higher priority and all coroutines of the same
391priority that were put into the ready queue earlier have been resumed.
375 392
376=item $is_ready = $coroutine->is_ready 393=item $is_ready = $coroutine->is_ready
377 394
378Return wether the coroutine is currently the ready queue or not, 395Return whether the coroutine is currently the ready queue or not,
379 396
380=item $coroutine->cancel (arg...) 397=item $coroutine->cancel (arg...)
381 398
382Terminates the given coroutine and makes it return the given arguments as 399Terminates the given coroutine and makes it return the given arguments as
383status (default: the empty list). Never returns if the coroutine is the 400status (default: the empty list). Never returns if the coroutine is the
… …
385 402
386=cut 403=cut
387 404
388sub cancel { 405sub cancel {
389 my $self = shift; 406 my $self = shift;
390 $self->{_status} = [@_];
391 407
392 if ($current == $self) { 408 if ($current == $self) {
393 push @destroy, $self; 409 terminate @_;
394 $manager->ready;
395 &schedule while 1;
396 } else { 410 } else {
411 $self->{_status} = [@_];
397 $self->_cancel; 412 $self->_cancel;
398 } 413 }
399} 414}
415
416=item $coroutine->throw ([$scalar])
417
418If C<$throw> is specified and defined, it will be thrown as an exception
419inside the coroutine at the next convenient point in time. Otherwise
420clears the exception object.
421
422Coro will check for the exception each time a schedule-like-function
423returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
424>>, C<< Coro::Handle->readable >> and so on. Most of these functions
425detect this case and return early in case an exception is pending.
426
427The exception object will be thrown "as is" with the specified scalar in
428C<$@>, i.e. if it is a string, no line number or newline will be appended
429(unlike with C<die>).
430
431This can be used as a softer means than C<cancel> to ask a coroutine to
432end itself, although there is no guarantee that the exception will lead to
433termination, and if the exception isn't caught it might well end the whole
434program.
435
436You might also think of C<throw> as being the moral equivalent of
437C<kill>ing a coroutine with a signal (in this case, a scalar).
400 438
401=item $coroutine->join 439=item $coroutine->join
402 440
403Wait until the coroutine terminates and return any values given to the 441Wait until the coroutine terminates and return any values given to the
404C<terminate> or C<cancel> functions. C<join> can be called concurrently 442C<terminate> or C<cancel> functions. C<join> can be called concurrently
405from multiple coroutines. 443from multiple coroutines, and all will be resumed and given the status
444return once the C<$coroutine> terminates.
406 445
407=cut 446=cut
408 447
409sub join { 448sub join {
410 my $self = shift; 449 my $self = shift;
… …
425 464
426=item $coroutine->on_destroy (\&cb) 465=item $coroutine->on_destroy (\&cb)
427 466
428Registers a callback that is called when this coroutine gets destroyed, 467Registers a callback that is called when this coroutine gets destroyed,
429but before it is joined. The callback gets passed the terminate arguments, 468but before it is joined. The callback gets passed the terminate arguments,
430if any. 469if any, and I<must not> die, under any circumstances.
431 470
432=cut 471=cut
433 472
434sub on_destroy { 473sub on_destroy {
435 my ($self, $cb) = @_; 474 my ($self, $cb) = @_;
… …
465higher values mean lower priority, just as in unix). 504higher values mean lower priority, just as in unix).
466 505
467=item $olddesc = $coroutine->desc ($newdesc) 506=item $olddesc = $coroutine->desc ($newdesc)
468 507
469Sets (or gets in case the argument is missing) the description for this 508Sets (or gets in case the argument is missing) the description for this
470coroutine. This is just a free-form string you can associate with a coroutine. 509coroutine. This is just a free-form string you can associate with a
510coroutine.
471 511
472This method simply sets the C<< $coroutine->{desc} >> member to the given string. You 512This method simply sets the C<< $coroutine->{desc} >> member to the given
473can modify this member directly if you wish. 513string. You can modify this member directly if you wish.
474
475=item $coroutine->throw ([$scalar])
476
477If C<$throw> is specified and defined, it will be thrown as an exception
478inside the coroutine at the next convinient point in time (usually after
479it gains control at the next schedule/transfer/cede). Otherwise clears the
480exception object.
481
482The exception object will be thrown "as is" with the specified scalar in
483C<$@>, i.e. if it is a string, no line number or newline will be appended
484(unlike with C<die>).
485
486This can be used as a softer means than C<cancel> to ask a coroutine to
487end itself, although there is no guarentee that the exception will lead to
488termination, and if the exception isn't caught it might well end the whole
489program.
490 514
491=cut 515=cut
492 516
493sub desc { 517sub desc {
494 my $old = $_[0]{desc}; 518 my $old = $_[0]{desc};
… …
503=over 4 527=over 4
504 528
505=item Coro::nready 529=item Coro::nready
506 530
507Returns the number of coroutines that are currently in the ready state, 531Returns the number of coroutines that are currently in the ready state,
508i.e. that can be switched to. The value C<0> means that the only runnable 532i.e. that can be switched to by calling C<schedule> directory or
533indirectly. The value C<0> means that the only runnable coroutine is the
509coroutine is the currently running one, so C<cede> would have no effect, 534currently running one, so C<cede> would have no effect, and C<schedule>
510and C<schedule> would cause a deadlock unless there is an idle handler 535would cause a deadlock unless there is an idle handler that wakes up some
511that wakes up some coroutines. 536coroutines.
512 537
513=item my $guard = Coro::guard { ... } 538=item my $guard = Coro::guard { ... }
514 539
515This creates and returns a guard object. Nothing happens until the object 540This creates and returns a guard object. Nothing happens until the object
516gets destroyed, in which case the codeblock given as argument will be 541gets destroyed, in which case the codeblock given as argument will be
… …
545 570
546 571
547=item unblock_sub { ... } 572=item unblock_sub { ... }
548 573
549This utility function takes a BLOCK or code reference and "unblocks" it, 574This utility function takes a BLOCK or code reference and "unblocks" it,
550returning the new coderef. This means that the new coderef will return 575returning a new coderef. Unblocking means that calling the new coderef
551immediately without blocking, returning nothing, while the original code 576will return immediately without blocking, returning nothing, while the
552ref will be called (with parameters) from within its own coroutine. 577original code ref will be called (with parameters) from within another
578coroutine.
553 579
554The reason this function exists is that many event libraries (such as the 580The reason this function exists is that many event libraries (such as the
555venerable L<Event|Event> module) are not coroutine-safe (a weaker form 581venerable L<Event|Event> module) are not coroutine-safe (a weaker form
556of thread-safety). This means you must not block within event callbacks, 582of thread-safety). This means you must not block within event callbacks,
557otherwise you might suffer from crashes or worse. 583otherwise you might suffer from crashes or worse. The only event library
584currently known that is safe to use without C<unblock_sub> is L<EV>.
558 585
559This function allows your callbacks to block by executing them in another 586This function allows your callbacks to block by executing them in another
560coroutine where it is safe to block. One example where blocking is handy 587coroutine where it is safe to block. One example where blocking is handy
561is when you use the L<Coro::AIO|Coro::AIO> functions to save results to 588is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
562disk. 589disk, for example.
563 590
564In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when 591In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
565creating event callbacks that want to block. 592creating event callbacks that want to block.
593
594If your handler does not plan to block (e.g. simply sends a message to
595another coroutine, or puts some other coroutine into the ready queue),
596there is no reason to use C<unblock_sub>.
597
598Note that you also need to use C<unblock_sub> for any other callbacks that
599are indirectly executed by any C-based event loop. For example, when you
600use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
601provides callbacks that are the result of some event callback, then you
602must not block either, or use C<unblock_sub>.
566 603
567=cut 604=cut
568 605
569our @unblock_queue; 606our @unblock_queue;
570 607
… …
583 cede; # for short-lived callbacks, this reduces pressure on the coro pool 620 cede; # for short-lived callbacks, this reduces pressure on the coro pool
584 } 621 }
585 schedule; # sleep well 622 schedule; # sleep well
586 } 623 }
587}; 624};
588$unblock_scheduler->desc ("[unblock_sub scheduler]"); 625$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
589 626
590sub unblock_sub(&) { 627sub unblock_sub(&) {
591 my $cb = shift; 628 my $cb = shift;
592 629
593 sub { 630 sub {
594 unshift @unblock_queue, [$cb, @_]; 631 unshift @unblock_queue, [$cb, @_];
595 $unblock_scheduler->ready; 632 $unblock_scheduler->ready;
596 } 633 }
597} 634}
598 635
636=item $cb = Coro::rouse_cb
637
638Create and return a "rouse callback". That's a code reference that, when
639called, will save its arguments and notify the owner coroutine of the
640callback.
641
642See the next function.
643
644=item @args = Coro::rouse_wait [$cb]
645
646Wait for the specified rouse callback (or the last one tht was created in
647this coroutine).
648
649As soon as the callback is invoked (or when the calback was invoked before
650C<rouse_wait>), it will return a copy of the arguments originally passed
651to the rouse callback.
652
653See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
654
599=back 655=back
600 656
601=cut 657=cut
602 658
6031; 6591;
604 660
661=head1 HOW TO WAIT FOR A CALLBACK
662
663It is very common for a coroutine to wait for some callback to be
664called. This occurs naturally when you use coroutines in an otherwise
665event-based program, or when you use event-based libraries.
666
667These typically register a callback for some event, and call that callback
668when the event occured. In a coroutine, however, you typically want to
669just wait for the event, simplyifying things.
670
671For example C<< AnyEvent->child >> registers a callback to be called when
672a specific child has exited:
673
674 my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
675
676But from withina coroutine, you often just want to write this:
677
678 my $status = wait_for_child $pid;
679
680Coro offers two functions specifically designed to make this easy,
681C<Coro::rouse_cb> and C<Coro::rouse_wait>.
682
683The first function, C<rouse_cb>, generates and returns a callback that,
684when invoked, will save it's arguments and notify the coroutine that
685created the callback.
686
687The second function, C<rouse_wait>, waits for the callback to be called
688(by calling C<schedule> to go to sleep) and returns the arguments
689originally passed to the callback.
690
691Using these functions, it becomes easy to write the C<wait_for_child>
692function mentioned above:
693
694 sub wait_for_child($) {
695 my ($pid) = @_;
696
697 my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
698
699 my ($rpid, $rstatus) = Coro::rouse_wait;
700 $rstatus
701 }
702
703In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
704you can roll your own, using C<schedule>:
705
706 sub wait_for_child($) {
707 my ($pid) = @_;
708
709 # store the current coroutine in $current,
710 # and provide result variables for the closure passed to ->child
711 my $current = $Coro::current;
712 my ($done, $rstatus);
713
714 # pass a closure to ->child
715 my $watcher = AnyEvent->child (pid => $pid, cb => sub {
716 $rstatus = $_[1]; # remember rstatus
717 $done = 1; # mark $rstatus as valud
718 });
719
720 # wait until the closure has been called
721 schedule while !$done;
722
723 $rstatus
724 }
725
726
605=head1 BUGS/LIMITATIONS 727=head1 BUGS/LIMITATIONS
606 728
607 - you must make very sure that no coro is still active on global 729=over 4
608 destruction. very bad things might happen otherwise (usually segfaults).
609 730
731=item fork with pthread backend
732
733When Coro is compiled using the pthread backend (which isn't recommended
734but required on many BSDs as their libcs are completely broken), then
735coroutines will not survive a fork. There is no known workaround except to
736fix your libc and use a saner backend.
737
738=item perl process emulation ("threads")
739
610 - this module is not thread-safe. You should only ever use this module 740This module is not perl-pseudo-thread-safe. You should only ever use this
611 from the same thread (this requirement might be loosened in the future 741module from the same thread (this requirement might be removed in the
612 to allow per-thread schedulers, but Coro::State does not yet allow 742future to allow per-thread schedulers, but Coro::State does not yet allow
613 this). 743this). I recommend disabling thread support and using processes, as having
744the windows process emulation enabled under unix roughly halves perl
745performance, even when not used.
746
747=item coroutine switching not signal safe
748
749You must not switch to another coroutine from within a signal handler
750(only relevant with %SIG - most event libraries provide safe signals).
751
752That means you I<MUST NOT> call any function that might "block" the
753current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
754anything that calls those. Everything else, including calling C<ready>,
755works.
756
757=back
758
614 759
615=head1 SEE ALSO 760=head1 SEE ALSO
616 761
617Lower level Configuration, Coroutine Environment: L<Coro::State>. 762Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
618 763
619Debugging: L<Coro::Debug>. 764Debugging: L<Coro::Debug>.
620 765
621Support/Utility: L<Coro::Specific>, L<Coro::Util>. 766Support/Utility: L<Coro::Specific>, L<Coro::Util>.
622 767
623Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. 768Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
624 769
625Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>. 770IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
626 771
627Compatibility: L<Coro::LWP>, L<Coro::Storable>, L<Coro::Select>. 772Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.
628 773
629Embedding: L<Coro::MakeMaker>. 774XS API: L<Coro::MakeMaker>.
775
776Low level Configuration, Coroutine Environment: L<Coro::State>.
630 777
631=head1 AUTHOR 778=head1 AUTHOR
632 779
633 Marc Lehmann <schmorp@schmorp.de> 780 Marc Lehmann <schmorp@schmorp.de>
634 http://home.schmorp.de/ 781 http://home.schmorp.de/

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