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Revision 1.113 by root, Tue Jan 23 15:55:45 2007 UTC

8 8
9 async { 9 async {
10 # some asynchronous thread of execution 10 # some asynchronous thread of execution
11 }; 11 };
12 12
13 # alternatively create an async process like this: 13 # alternatively create an async coroutine like this:
14 14
15 sub some_func : Coro { 15 sub some_func : Coro {
16 # some more async code 16 # some more async code
17 } 17 }
18 18
19 cede; 19 cede;
20 20
21=head1 DESCRIPTION 21=head1 DESCRIPTION
22 22
23This module collection manages coroutines. Coroutines are similar to 23This module collection manages coroutines. Coroutines are similar
24threads but don't run in parallel. 24to threads but don't run in parallel at the same time even on SMP
25machines. The specific flavor of coroutine use din this module also
26guarentees you that it will not switch between coroutines unless
27necessary, at easily-identified points in your program, so locking and
28parallel access are rarely an issue, making coroutine programming much
29safer than threads programming.
25 30
31(Perl, however, does not natively support real threads but instead does a
32very slow and memory-intensive emulation of processes using threads. This
33is a performance win on Windows machines, and a loss everywhere else).
34
26In this module, coroutines are defined as "callchain + lexical variables 35In this module, coroutines are defined as "callchain + lexical variables +
27+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own 36@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
28callchain, it's own set of lexicals and it's own set of perl's most 37its own set of lexicals and its own set of perls most important global
29important global variables. 38variables.
30 39
31=cut 40=cut
32 41
33package Coro; 42package Coro;
34 43
35BEGIN { eval { require warnings } && warnings->unimport ("uninitialized") } 44use strict;
45no warnings "uninitialized";
36 46
37use Coro::State; 47use Coro::State;
38 48
39use vars qw($idle $main $current); 49use base qw(Coro::State Exporter);
40 50
41use base Exporter; 51our $idle; # idle handler
52our $main; # main coroutine
53our $current; # current coroutine
42 54
43$VERSION = 1.1; 55our $VERSION = '3.42';
44 56
45@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
46%EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
47 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48); 60);
49@EXPORT_OK = @{$EXPORT_TAGS{prio}}; 61our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
50 62
51{ 63{
52 my @async; 64 my @async;
53 my $init; 65 my $init;
54 66
55 # this way of handling attributes simply is NOT scalable ;() 67 # this way of handling attributes simply is NOT scalable ;()
56 sub import { 68 sub import {
69 no strict 'refs';
70
57 Coro->export_to_level(1, @_); 71 Coro->export_to_level (1, @_);
72
58 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; 73 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
59 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { 74 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
60 my ($package, $ref) = (shift, shift); 75 my ($package, $ref) = (shift, shift);
61 my @attrs; 76 my @attrs;
62 for (@_) { 77 for (@_) {
89 104
90$main = new Coro; 105$main = new Coro;
91 106
92=item $current (or as function: current) 107=item $current (or as function: current)
93 108
94The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). 109The current coroutine (the last coroutine switched to). The initial value
110is C<$main> (of course).
111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essentiel you are encouraged to use the
114C<Coro::current> function instead.
95 115
96=cut 116=cut
97 117
98# maybe some other module used Coro::Specific before... 118# maybe some other module used Coro::Specific before...
99if ($current) {
100 $main->{specific} = $current->{specific}; 119$main->{specific} = $current->{specific}
101} 120 if $current;
102 121
103$current = $main; 122_set_current $main;
104 123
105sub current() { $current } 124sub current() { $current }
106 125
107=item $idle 126=item $idle
108 127
109The coroutine to switch to when no other coroutine is running. The default 128A callback that is called whenever the scheduler finds no ready coroutines
110implementation prints "FATAL: deadlock detected" and exits. 129to run. The default implementation prints "FATAL: deadlock detected" and
130exits, because the program has no other way to continue.
111 131
112=cut 132This hook is overwritten by modules such as C<Coro::Timer> and
133C<Coro::Event> to wait on an external event that hopefully wake up a
134coroutine so the scheduler can run it.
113 135
114# should be done using priorities :( 136Please note that if your callback recursively invokes perl (e.g. for event
115$idle = new Coro sub { 137handlers), then it must be prepared to be called recursively.
116 print STDERR "FATAL: deadlock detected\n"; 138
117 exit(51); 139=cut
140
141$idle = sub {
142 require Carp;
143 Carp::croak ("FATAL: deadlock detected");
118}; 144};
145
146sub _cancel {
147 my ($self) = @_;
148
149 # free coroutine data and mark as destructed
150 $self->_destroy
151 or return;
152
153 # call all destruction callbacks
154 $_->(@{$self->{status}})
155 for @{(delete $self->{destroy_cb}) || []};
156}
119 157
120# this coroutine is necessary because a coroutine 158# this coroutine is necessary because a coroutine
121# cannot destroy itself. 159# cannot destroy itself.
122my @destroy; 160my @destroy;
123my $manager; 161my $manager;
162
124$manager = new Coro sub { 163$manager = new Coro sub {
125 while () { 164 while () {
126 # by overwriting the state object with the manager we destroy it 165 (shift @destroy)->_cancel
127 # while still being able to schedule this coroutine (in case it has
128 # been readied multiple times. this is harmless since the manager
129 # can be called as many times as neccessary and will always
130 # remove itself from the runqueue
131 while (@destroy) { 166 while @destroy;
132 my $coro = pop @destroy;
133 $coro->{status} ||= [];
134 $_->ready for @{delete $coro->{join} || []};
135 167
136 # the next line destroys the _coro_state, but keeps the
137 # process itself intact (we basically make it a zombie
138 # process that always runs the manager thread, so it's possible
139 # to transfer() to this process).
140 $coro->{_coro_state} = $manager->{_coro_state};
141 }
142 &schedule; 168 &schedule;
143 } 169 }
144}; 170};
145 171
172$manager->prio (PRIO_MAX);
173
146# static methods. not really. 174# static methods. not really.
147 175
148=back 176=back
149 177
150=head2 STATIC METHODS 178=head2 STATIC METHODS
151 179
152Static methods are actually functions that operate on the current process only. 180Static methods are actually functions that operate on the current coroutine only.
153 181
154=over 4 182=over 4
155 183
156=item async { ... } [@args...] 184=item async { ... } [@args...]
157 185
158Create a new asynchronous process and return it's process object 186Create a new asynchronous coroutine and return it's coroutine object
159(usually unused). When the sub returns the new process is automatically 187(usually unused). When the sub returns the new coroutine is automatically
160terminated. 188terminated.
189
190Calling C<exit> in a coroutine will not work correctly, so do not do that.
191
192When the coroutine dies, the program will exit, just as in the main
193program.
161 194
162 # create a new coroutine that just prints its arguments 195 # create a new coroutine that just prints its arguments
163 async { 196 async {
164 print "@_\n"; 197 print "@_\n";
165 } 1,2,3,4; 198 } 1,2,3,4;
166 199
167=cut 200=cut
168 201
169sub async(&@) { 202sub async(&@) {
170 my $pid = new Coro @_; 203 my $coro = new Coro @_;
171 $manager->ready; # this ensures that the stack is cloned from the manager
172 $pid->ready; 204 $coro->ready;
173 $pid; 205 $coro
206}
207
208=item async_pool { ... } [@args...]
209
210Similar to C<async>, but uses a coroutine pool, so you should not call
211terminate or join (although you are allowed to), and you get a coroutine
212that might have executed other code already (which can be good or bad :).
213
214Also, the block is executed in an C<eval> context and a warning will be
215issued in case of an exception instead of terminating the program, as
216C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
217will not work in the expected way, unless you call terminate or cancel,
218which somehow defeats the purpose of pooling.
219
220The priority will be reset to C<0> after each job, otherwise the coroutine
221will be re-used "as-is".
222
223The pool size is limited to 8 idle coroutines (this can be adjusted by
224changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
225required.
226
227If you are concerned about pooled coroutines growing a lot because a
228single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {
229terminate }> once per second or so to slowly replenish the pool.
230
231=cut
232
233our $POOL_SIZE = 8;
234our @pool;
235
236sub pool_handler {
237 while () {
238 eval {
239 my ($cb, @arg) = @{ delete $current->{_invoke} or return };
240 $cb->(@arg);
241 };
242 warn $@ if $@;
243
244 last if @pool >= $POOL_SIZE;
245 push @pool, $current;
246
247 $current->prio (0);
248 schedule;
249 }
250}
251
252sub async_pool(&@) {
253 # this is also inlined into the unlock_scheduler
254 my $coro = (pop @pool or new Coro \&pool_handler);
255
256 $coro->{_invoke} = [@_];
257 $coro->ready;
258
259 $coro
174} 260}
175 261
176=item schedule 262=item schedule
177 263
178Calls the scheduler. Please note that the current process will not be put 264Calls the scheduler. Please note that the current coroutine will not be put
179into the ready queue, so calling this function usually means you will 265into the ready queue, so calling this function usually means you will
180never be called again. 266never be called again unless something else (e.g. an event handler) calls
267ready.
181 268
182=cut 269The canonical way to wait on external events is this:
270
271 {
272 # remember current coroutine
273 my $current = $Coro::current;
274
275 # register a hypothetical event handler
276 on_event_invoke sub {
277 # wake up sleeping coroutine
278 $current->ready;
279 undef $current;
280 };
281
282 # call schedule until event occured.
283 # in case we are woken up for other reasons
284 # (current still defined), loop.
285 Coro::schedule while $current;
286 }
183 287
184=item cede 288=item cede
185 289
186"Cede" to other processes. This function puts the current process into the 290"Cede" to other coroutines. This function puts the current coroutine into the
187ready queue and calls C<schedule>, which has the effect of giving up the 291ready queue and calls C<schedule>, which has the effect of giving up the
188current "timeslice" to other coroutines of the same or higher priority. 292current "timeslice" to other coroutines of the same or higher priority.
189 293
190=cut 294Returns true if at least one coroutine switch has happened.
295
296=item Coro::cede_notself
297
298Works like cede, but is not exported by default and will cede to any
299coroutine, regardless of priority, once.
300
301Returns true if at least one coroutine switch has happened.
191 302
192=item terminate [arg...] 303=item terminate [arg...]
193 304
194Terminates the current process with the given status values (see L<cancel>). 305Terminates the current coroutine with the given status values (see L<cancel>).
195 306
196=cut 307=cut
197 308
198sub terminate { 309sub terminate {
199 $current->cancel (@_); 310 $current->cancel (@_);
201 312
202=back 313=back
203 314
204# dynamic methods 315# dynamic methods
205 316
206=head2 PROCESS METHODS 317=head2 COROUTINE METHODS
207 318
208These are the methods you can call on process objects. 319These are the methods you can call on coroutine objects.
209 320
210=over 4 321=over 4
211 322
212=item new Coro \&sub [, @args...] 323=item new Coro \&sub [, @args...]
213 324
214Create a new process and return it. When the sub returns the process 325Create a new coroutine and return it. When the sub returns the coroutine
215automatically terminates as if C<terminate> with the returned values were 326automatically terminates as if C<terminate> with the returned values were
216called. To make the process run you must first put it into the ready queue 327called. To make the coroutine run you must first put it into the ready queue
217by calling the ready method. 328by calling the ready method.
218 329
219=cut 330Calling C<exit> in a coroutine will not work correctly, so do not do that.
220 331
332=cut
333
221sub _newcoro { 334sub _run_coro {
222 terminate &{+shift}; 335 terminate &{+shift};
223} 336}
224 337
225sub new { 338sub new {
226 my $class = shift; 339 my $class = shift;
227 bless {
228 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
229 }, $class;
230}
231 340
232=item $process->ready 341 $class->SUPER::new (\&_run_coro, @_)
342}
233 343
234Put the given process into the ready queue. 344=item $success = $coroutine->ready
235 345
236=cut 346Put the given coroutine into the ready queue (according to it's priority)
347and return true. If the coroutine is already in the ready queue, do nothing
348and return false.
237 349
350=item $is_ready = $coroutine->is_ready
351
352Return wether the coroutine is currently the ready queue or not,
353
238=item $process->cancel (arg...) 354=item $coroutine->cancel (arg...)
239 355
240Temrinates the given process and makes it return the given arguments as 356Terminates the given coroutine and makes it return the given arguments as
241status (default: the empty list). 357status (default: the empty list). Never returns if the coroutine is the
358current coroutine.
242 359
243=cut 360=cut
244 361
245sub cancel { 362sub cancel {
246 my $self = shift; 363 my $self = shift;
247 $self->{status} = [@_]; 364 $self->{status} = [@_];
365
366 if ($current == $self) {
248 push @destroy, $self; 367 push @destroy, $self;
249 $manager->ready; 368 $manager->ready;
250 &schedule if $current == $self; 369 &schedule while 1;
370 } else {
371 $self->_cancel;
372 }
251} 373}
252 374
253=item $process->join 375=item $coroutine->join
254 376
255Wait until the coroutine terminates and return any values given to the 377Wait until the coroutine terminates and return any values given to the
256C<terminate> or C<cancel> functions. C<join> can be called multiple times 378C<terminate> or C<cancel> functions. C<join> can be called multiple times
257from multiple processes. 379from multiple coroutine.
258 380
259=cut 381=cut
260 382
261sub join { 383sub join {
262 my $self = shift; 384 my $self = shift;
385
263 unless ($self->{status}) { 386 unless ($self->{status}) {
264 push @{$self->{join}}, $current; 387 my $current = $current;
265 &schedule; 388
389 push @{$self->{destroy_cb}}, sub {
390 $current->ready;
391 undef $current;
392 };
393
394 &schedule while $current;
266 } 395 }
396
267 wantarray ? @{$self->{status}} : $self->{status}[0]; 397 wantarray ? @{$self->{status}} : $self->{status}[0];
268} 398}
269 399
400=item $coroutine->on_destroy (\&cb)
401
402Registers a callback that is called when this coroutine gets destroyed,
403but before it is joined. The callback gets passed the terminate arguments,
404if any.
405
406=cut
407
408sub on_destroy {
409 my ($self, $cb) = @_;
410
411 push @{ $self->{destroy_cb} }, $cb;
412}
413
270=item $oldprio = $process->prio($newprio) 414=item $oldprio = $coroutine->prio ($newprio)
271 415
272Sets (or gets, if the argument is missing) the priority of the 416Sets (or gets, if the argument is missing) the priority of the
273process. Higher priority processes get run before lower priority 417coroutine. Higher priority coroutines get run before lower priority
274processes. Priorities are small signed integers (currently -4 .. +3), 418coroutines. Priorities are small signed integers (currently -4 .. +3),
275that you can refer to using PRIO_xxx constants (use the import tag :prio 419that you can refer to using PRIO_xxx constants (use the import tag :prio
276to get then): 420to get then):
277 421
278 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 422 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
279 3 > 1 > 0 > -1 > -3 > -4 423 3 > 1 > 0 > -1 > -3 > -4
282 current->prio(PRIO_HIGH); 426 current->prio(PRIO_HIGH);
283 427
284The idle coroutine ($Coro::idle) always has a lower priority than any 428The idle coroutine ($Coro::idle) always has a lower priority than any
285existing coroutine. 429existing coroutine.
286 430
287Changing the priority of the current process will take effect immediately, 431Changing the priority of the current coroutine will take effect immediately,
288but changing the priority of processes in the ready queue (but not 432but changing the priority of coroutines in the ready queue (but not
289running) will only take effect after the next schedule (of that 433running) will only take effect after the next schedule (of that
290process). This is a bug that will be fixed in some future version. 434coroutine). This is a bug that will be fixed in some future version.
291 435
292=cut
293
294sub prio {
295 my $old = $_[0]{prio};
296 $_[0]{prio} = $_[1] if @_ > 1;
297 $old;
298}
299
300=item $newprio = $process->nice($change) 436=item $newprio = $coroutine->nice ($change)
301 437
302Similar to C<prio>, but subtract the given value from the priority (i.e. 438Similar to C<prio>, but subtract the given value from the priority (i.e.
303higher values mean lower priority, just as in unix). 439higher values mean lower priority, just as in unix).
304 440
305=cut
306
307sub nice {
308 $_[0]{prio} -= $_[1];
309}
310
311=item $olddesc = $process->desc($newdesc) 441=item $olddesc = $coroutine->desc ($newdesc)
312 442
313Sets (or gets in case the argument is missing) the description for this 443Sets (or gets in case the argument is missing) the description for this
314process. This is just a free-form string you can associate with a process. 444coroutine. This is just a free-form string you can associate with a coroutine.
315 445
316=cut 446=cut
317 447
318sub desc { 448sub desc {
319 my $old = $_[0]{desc}; 449 my $old = $_[0]{desc};
321 $old; 451 $old;
322} 452}
323 453
324=back 454=back
325 455
456=head2 GLOBAL FUNCTIONS
457
458=over 4
459
460=item Coro::nready
461
462Returns the number of coroutines that are currently in the ready state,
463i.e. that can be swicthed to. The value C<0> means that the only runnable
464coroutine is the currently running one, so C<cede> would have no effect,
465and C<schedule> would cause a deadlock unless there is an idle handler
466that wakes up some coroutines.
467
468=item my $guard = Coro::guard { ... }
469
470This creates and returns a guard object. Nothing happens until the objetc
471gets destroyed, in which case the codeblock given as argument will be
472executed. This is useful to free locks or other resources in case of a
473runtime error or when the coroutine gets canceled, as in both cases the
474guard block will be executed. The guard object supports only one method,
475C<< ->cancel >>, which will keep the codeblock from being executed.
476
477Example: set some flag and clear it again when the coroutine gets canceled
478or the function returns:
479
480 sub do_something {
481 my $guard = Coro::guard { $busy = 0 };
482 $busy = 1;
483
484 # do something that requires $busy to be true
485 }
486
487=cut
488
489sub guard(&) {
490 bless \(my $cb = $_[0]), "Coro::guard"
491}
492
493sub Coro::guard::cancel {
494 ${$_[0]} = sub { };
495}
496
497sub Coro::guard::DESTROY {
498 ${$_[0]}->();
499}
500
501
502=item unblock_sub { ... }
503
504This utility function takes a BLOCK or code reference and "unblocks" it,
505returning the new coderef. This means that the new coderef will return
506immediately without blocking, returning nothing, while the original code
507ref will be called (with parameters) from within its own coroutine.
508
509The reason this fucntion exists is that many event libraries (such as the
510venerable L<Event|Event> module) are not coroutine-safe (a weaker form
511of thread-safety). This means you must not block within event callbacks,
512otherwise you might suffer from crashes or worse.
513
514This function allows your callbacks to block by executing them in another
515coroutine where it is safe to block. One example where blocking is handy
516is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
517disk.
518
519In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
520creating event callbacks that want to block.
521
522=cut
523
524our @unblock_queue;
525
526# we create a special coro because we want to cede,
527# to reduce pressure on the coro pool (because most callbacks
528# return immediately and can be reused) and because we cannot cede
529# inside an event callback.
530our $unblock_scheduler = async {
531 while () {
532 while (my $cb = pop @unblock_queue) {
533 # this is an inlined copy of async_pool
534 my $coro = (pop @pool or new Coro \&pool_handler);
535
536 $coro->{_invoke} = $cb;
537 $coro->ready;
538 cede; # for short-lived callbacks, this reduces pressure on the coro pool
539 }
540 schedule; # sleep well
541 }
542};
543
544sub unblock_sub(&) {
545 my $cb = shift;
546
547 sub {
548 unshift @unblock_queue, [$cb, @_];
549 $unblock_scheduler->ready;
550 }
551}
552
553=back
554
326=cut 555=cut
327 556
3281; 5571;
329 558
330=head1 BUGS/LIMITATIONS 559=head1 BUGS/LIMITATIONS
337 to allow per-thread schedulers, but Coro::State does not yet allow 566 to allow per-thread schedulers, but Coro::State does not yet allow
338 this). 567 this).
339 568
340=head1 SEE ALSO 569=head1 SEE ALSO
341 570
342L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 571Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
343L<Coro::Signal>, L<Coro::State>, L<Coro::Timer>, L<Coro::Event>, 572
344L<Coro::Handle>, L<Coro::RWLock>, L<Coro::Socket>. 573Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
574
575Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
576
577Embedding: L<Coro:MakeMaker>
345 578
346=head1 AUTHOR 579=head1 AUTHOR
347 580
348 Marc Lehmann <pcg@goof.com> 581 Marc Lehmann <schmorp@schmorp.de>
349 http://home.schmorp.de/ 582 http://home.schmorp.de/
350 583
351=cut 584=cut
352 585

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