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Revision 1.42 by root, Tue Nov 6 20:37:20 2001 UTC vs.
Revision 1.114 by root, Wed Jan 24 16:22:08 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
44use strict;
35no warnings qw(uninitialized); 45no warnings "uninitialized";
36 46
37use Coro::State; 47use Coro::State;
38 48
39use base Exporter; 49use base qw(Coro::State Exporter);
40 50
51our $idle; # idle handler
52our $main; # main coroutine
53our $current; # current coroutine
54
41$VERSION = 0.52; 55our $VERSION = '3.5';
42 56
43@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
44%EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
45 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
46); 60);
47@EXPORT_OK = @{$EXPORT_TAGS{prio}}; 61our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
48 62
49{ 63{
50 my @async; 64 my @async;
51 my $init; 65 my $init;
52 66
53 # this way of handling attributes simply is NOT scalable ;() 67 # this way of handling attributes simply is NOT scalable ;()
54 sub import { 68 sub import {
69 no strict 'refs';
70
55 Coro->export_to_level(1, @_); 71 Coro->export_to_level (1, @_);
72
56 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; 73 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
57 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { 74 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
58 my ($package, $ref) = (shift, shift); 75 my ($package, $ref) = (shift, shift);
59 my @attrs; 76 my @attrs;
60 for (@_) { 77 for (@_) {
75 }; 92 };
76 } 93 }
77 94
78} 95}
79 96
97=over 4
98
80=item $main 99=item $main
81 100
82This coroutine represents the main program. 101This coroutine represents the main program.
83 102
84=cut 103=cut
85 104
86our $main = new Coro; 105$main = new Coro;
87 106
88=item $current (or as function: current) 107=item $current (or as function: current)
89 108
90The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). 109The current coroutine (the last coroutine switched to). The initial value
110is C<$main> (of course).
111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essentiel you are encouraged to use the
114C<Coro::current> function instead.
91 115
92=cut 116=cut
93 117
94# maybe some other module used Coro::Specific before... 118# maybe some other module used Coro::Specific before...
95if ($current) {
96 $main->{specific} = $current->{specific}; 119$main->{specific} = $current->{specific}
97} 120 if $current;
98 121
99our $current = $main; 122_set_current $main;
100 123
101sub current() { $current } 124sub current() { $current }
102 125
103=item $idle 126=item $idle
104 127
105The coroutine to switch to when no other coroutine is running. The default 128A callback that is called whenever the scheduler finds no ready coroutines
106implementation 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.
107 131
108=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.
109 135
110# should be done using priorities :( 136Please note that if your callback recursively invokes perl (e.g. for event
111our $idle = new Coro sub { 137handlers), then it must be prepared to be called recursively.
112 print STDERR "FATAL: deadlock detected\n"; 138
113 exit(51); 139=cut
140
141$idle = sub {
142 require Carp;
143 Carp::croak ("FATAL: deadlock detected");
114}; 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}
115 157
116# this coroutine is necessary because a coroutine 158# this coroutine is necessary because a coroutine
117# cannot destroy itself. 159# cannot destroy itself.
118my @destroy; 160my @destroy;
119my $manager; 161my $manager;
162
120$manager = new Coro sub { 163$manager = new Coro sub {
121 while() { 164 while () {
122 # by overwriting the state object with the manager we destroy it 165 (shift @destroy)->_cancel
123 # while still being able to schedule this coroutine (in case it has
124 # been readied multiple times. this is harmless since the manager
125 # can be called as many times as neccessary and will always
126 # remove itself from the runqueue
127 while (@destroy) { 166 while @destroy;
128 my $coro = pop @destroy; 167
129 $coro->{status} ||= [];
130 $_->ready for @{delete $coro->{join} || []};
131 $coro->{_coro_state} = $manager->{_coro_state};
132 }
133 &schedule; 168 &schedule;
134 } 169 }
135}; 170};
136 171
172$manager->prio (PRIO_MAX);
173
137# static methods. not really. 174# static methods. not really.
138 175
176=back
177
139=head2 STATIC METHODS 178=head2 STATIC METHODS
140 179
141Static methods are actually functions that operate on the current process only. 180Static methods are actually functions that operate on the current coroutine only.
142 181
143=over 4 182=over 4
144 183
145=item async { ... } [@args...] 184=item async { ... } [@args...]
146 185
147Create a new asynchronous process and return it's process object 186Create a new asynchronous coroutine and return it's coroutine object
148(usually unused). When the sub returns the new process is automatically 187(usually unused). When the sub returns the new coroutine is automatically
149terminated. 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.
150 194
151 # create a new coroutine that just prints its arguments 195 # create a new coroutine that just prints its arguments
152 async { 196 async {
153 print "@_\n"; 197 print "@_\n";
154 } 1,2,3,4; 198 } 1,2,3,4;
155 199
156The coderef you submit MUST NOT be a closure that refers to variables
157in an outer scope. This does NOT work. Pass arguments into it instead.
158
159=cut 200=cut
160 201
161sub async(&@) { 202sub async(&@) {
162 my $pid = new Coro @_; 203 my $coro = new Coro @_;
163 $manager->ready; # this ensures that the stack is cloned from the manager
164 $pid->ready; 204 $coro->ready;
165 $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
166} 260}
167 261
168=item schedule 262=item schedule
169 263
170Calls 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
171into the ready queue, so calling this function usually means you will 265into the ready queue, so calling this function usually means you will
172never be called again. 266never be called again unless something else (e.g. an event handler) calls
267ready.
173 268
174=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 }
175 287
176=item cede 288=item cede
177 289
178"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
179ready 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
180current "timeslice" to other coroutines of the same or higher priority. 292current "timeslice" to other coroutines of the same or higher priority.
181 293
182=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.
183 302
184=item terminate [arg...] 303=item terminate [arg...]
185 304
186Terminates the current process. 305Terminates the current coroutine with the given status values (see L<cancel>).
187
188Future versions of this function will allow result arguments.
189 306
190=cut 307=cut
191 308
192sub terminate { 309sub terminate {
193 $current->{status} = [@_];
194 $current->cancel; 310 $current->cancel (@_);
195 &schedule;
196 die; # NORETURN
197} 311}
198 312
199=back 313=back
200 314
201# dynamic methods 315# dynamic methods
202 316
203=head2 PROCESS METHODS 317=head2 COROUTINE METHODS
204 318
205These are the methods you can call on process objects. 319These are the methods you can call on coroutine objects.
206 320
207=over 4 321=over 4
208 322
209=item new Coro \&sub [, @args...] 323=item new Coro \&sub [, @args...]
210 324
211Create 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
212automatically terminates as if C<terminate> with the returned values were 326automatically terminates as if C<terminate> with the returned values were
213called. 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
214by calling the ready method. 328by calling the ready method.
215 329
216=cut 330Calling C<exit> in a coroutine will not work correctly, so do not do that.
217 331
332=cut
333
218sub _newcoro { 334sub _run_coro {
219 terminate &{+shift}; 335 terminate &{+shift};
220} 336}
221 337
222sub new { 338sub new {
223 my $class = shift; 339 my $class = shift;
224 bless {
225 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
226 }, $class;
227}
228 340
229=item $process->ready 341 $class->SUPER::new (\&_run_coro, @_)
342}
230 343
231Put the given process into the ready queue. 344=item $success = $coroutine->ready
232 345
233=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.
234 349
235=item $process->cancel 350=item $is_ready = $coroutine->is_ready
236 351
237Like C<terminate>, but terminates the specified process instead. 352Return wether the coroutine is currently the ready queue or not,
353
354=item $coroutine->cancel (arg...)
355
356Terminates the given coroutine and makes it return the given arguments as
357status (default: the empty list). Never returns if the coroutine is the
358current coroutine.
238 359
239=cut 360=cut
240 361
241sub cancel { 362sub cancel {
363 my $self = shift;
364 $self->{status} = [@_];
365
366 if ($current == $self) {
242 push @destroy, $_[0]; 367 push @destroy, $self;
243 $manager->ready; 368 $manager->ready;
244 &schedule if $current == $_[0]; 369 &schedule while 1;
370 } else {
371 $self->_cancel;
372 }
245} 373}
246 374
247=item $process->join 375=item $coroutine->join
248 376
249Wait until the coroutine terminates and return any values given to the 377Wait until the coroutine terminates and return any values given to the
250C<terminate> function. C<join> can be called multiple times from multiple 378C<terminate> or C<cancel> functions. C<join> can be called multiple times
251processes. 379from multiple coroutine.
252 380
253=cut 381=cut
254 382
255sub join { 383sub join {
256 my $self = shift; 384 my $self = shift;
385
257 unless ($self->{status}) { 386 unless ($self->{status}) {
258 push @{$self->{join}}, $current; 387 my $current = $current;
259 &schedule; 388
389 push @{$self->{destroy_cb}}, sub {
390 $current->ready;
391 undef $current;
392 };
393
394 &schedule while $current;
260 } 395 }
396
261 wantarray ? @{$self->{status}} : $self->{status}[0]; 397 wantarray ? @{$self->{status}} : $self->{status}[0];
262} 398}
263 399
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
264=item $oldprio = $process->prio($newprio) 414=item $oldprio = $coroutine->prio ($newprio)
265 415
266Sets (or gets, if the argument is missing) the priority of the 416Sets (or gets, if the argument is missing) the priority of the
267process. Higher priority processes get run before lower priority 417coroutine. Higher priority coroutines get run before lower priority
268processes. Priorities are smalled signed integer (currently -4 .. +3), 418coroutines. Priorities are small signed integers (currently -4 .. +3),
269that 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
270to get then): 420to get then):
271 421
272 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
273 3 > 1 > 0 > -1 > -3 > -4 423 3 > 1 > 0 > -1 > -3 > -4
276 current->prio(PRIO_HIGH); 426 current->prio(PRIO_HIGH);
277 427
278The idle coroutine ($Coro::idle) always has a lower priority than any 428The idle coroutine ($Coro::idle) always has a lower priority than any
279existing coroutine. 429existing coroutine.
280 430
281Changing the priority of the current process will take effect immediately, 431Changing the priority of the current coroutine will take effect immediately,
282but changing the priority of processes in the ready queue (but not 432but changing the priority of coroutines in the ready queue (but not
283running) will only take effect after the next schedule (of that 433running) will only take effect after the next schedule (of that
284process). 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.
285 435
286=cut
287
288sub prio {
289 my $old = $_[0]{prio};
290 $_[0]{prio} = $_[1] if @_ > 1;
291 $old;
292}
293
294=item $newprio = $process->nice($change) 436=item $newprio = $coroutine->nice ($change)
295 437
296Similar 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.
297higher values mean lower priority, just as in unix). 439higher values mean lower priority, just as in unix).
298 440
299=cut
300
301sub nice {
302 $_[0]{prio} -= $_[1];
303}
304
305=item $olddesc = $process->desc($newdesc) 441=item $olddesc = $coroutine->desc ($newdesc)
306 442
307Sets (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
308process. 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.
309 445
310=cut 446=cut
311 447
312sub desc { 448sub desc {
313 my $old = $_[0]{desc}; 449 my $old = $_[0]{desc};
315 $old; 451 $old;
316} 452}
317 453
318=back 454=back
319 455
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
320=cut 555=cut
321 556
3221; 5571;
323 558
324=head1 BUGS/LIMITATIONS 559=head1 BUGS/LIMITATIONS
325 560
326 - you must make very sure that no coro is still active on global destruction. 561 - you must make very sure that no coro is still active on global
327 very bad things might happen otherwise (usually segfaults). 562 destruction. very bad things might happen otherwise (usually segfaults).
563
328 - this module is not thread-safe. You should only ever use this module from 564 - this module is not thread-safe. You should only ever use this module
329 the same thread (this requirement might be loosened in the future to 565 from the same thread (this requirement might be losened in the future
330 allow per-thread schedulers, but Coro::State does not yet allow this). 566 to allow per-thread schedulers, but Coro::State does not yet allow
567 this).
331 568
332=head1 SEE ALSO 569=head1 SEE ALSO
333 570
334L<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>.
335L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>, 572
336L<Coro::Handle>, 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>
337 578
338=head1 AUTHOR 579=head1 AUTHOR
339 580
340 Marc Lehmann <pcg@goof.com> 581 Marc Lehmann <schmorp@schmorp.de>
341 http://www.goof.com/pcg/marc/ 582 http://home.schmorp.de/
342 583
343=cut 584=cut
344 585

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