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Revision 1.78 by root, Wed Nov 1 01:21:21 2006 UTC vs.
Revision 1.148 by root, Fri Oct 5 20:11:25 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 used in this module also
26guarantees 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
35use strict; 44use strict;
36no warnings "uninitialized"; 45no warnings "uninitialized";
37 46
38use Coro::State; 47use Coro::State;
39 48
40use base Exporter::; 49use base qw(Coro::State Exporter);
41 50
42our $idle; # idle coroutine 51our $idle; # idle handler
43our $main; # main coroutine 52our $main; # main coroutine
44our $current; # current coroutine 53our $current; # current coroutine
45 54
46our $VERSION = '2.1'; 55our $VERSION = '4.01';
47 56
48our @EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
49our %EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
50 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
51); 60);
52our @EXPORT_OK = @{$EXPORT_TAGS{prio}}; 61our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
53 62
54{ 63{
55 my @async; 64 my @async;
56 my $init; 65 my $init;
57 66
58 # this way of handling attributes simply is NOT scalable ;() 67 # this way of handling attributes simply is NOT scalable ;()
59 sub import { 68 sub import {
60 no strict 'refs'; 69 no strict 'refs';
61 70
62 Coro->export_to_level(1, @_); 71 Coro->export_to_level (1, @_);
63 72
64 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; 73 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
65 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { 74 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
66 my ($package, $ref) = (shift, shift); 75 my ($package, $ref) = (shift, shift);
67 my @attrs; 76 my @attrs;
95 104
96$main = new Coro; 105$main = new Coro;
97 106
98=item $current (or as function: current) 107=item $current (or as function: current)
99 108
100The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). 109The current coroutine (the last coroutine switched to). The initial value
110is C<$main> (of course).
101 111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essential you are encouraged to use the
114C<Coro::current> function instead.
115
102=cut 116=cut
117
118$main->{desc} = "[main::]";
103 119
104# maybe some other module used Coro::Specific before... 120# maybe some other module used Coro::Specific before...
105if ($current) {
106 $main->{specific} = $current->{specific}; 121$main->{_specific} = $current->{_specific}
107} 122 if $current;
108 123
109$current = $main; 124_set_current $main;
110 125
111sub current() { $current } 126sub current() { $current }
112 127
113=item $idle 128=item $idle
114 129
115The coroutine to switch to when no other coroutine is running. The default 130A callback that is called whenever the scheduler finds no ready coroutines
116implementation prints "FATAL: deadlock detected" and exits. 131to run. The default implementation prints "FATAL: deadlock detected" and
132exits, because the program has no other way to continue.
117 133
118=cut 134This hook is overwritten by modules such as C<Coro::Timer> and
135C<Coro::Event> to wait on an external event that hopefully wake up a
136coroutine so the scheduler can run it.
119 137
120# should be done using priorities :( 138Please note that if your callback recursively invokes perl (e.g. for event
121$idle = new Coro sub { 139handlers), then it must be prepared to be called recursively.
122 print STDERR "FATAL: deadlock detected\n"; 140
123 exit(51); 141=cut
142
143$idle = sub {
144 require Carp;
145 Carp::croak ("FATAL: deadlock detected");
124}; 146};
147
148sub _cancel {
149 my ($self) = @_;
150
151 # free coroutine data and mark as destructed
152 $self->_destroy
153 or return;
154
155 # call all destruction callbacks
156 $_->(@{$self->{_status}})
157 for @{(delete $self->{_on_destroy}) || []};
158}
125 159
126# this coroutine is necessary because a coroutine 160# this coroutine is necessary because a coroutine
127# cannot destroy itself. 161# cannot destroy itself.
128my @destroy; 162my @destroy;
129my $manager; 163my $manager;
164
130$manager = new Coro sub { 165$manager = new Coro sub {
131 while () { 166 while () {
132 # by overwriting the state object with the manager we destroy it 167 (shift @destroy)->_cancel
133 # while still being able to schedule this coroutine (in case it has
134 # been readied multiple times. this is harmless since the manager
135 # can be called as many times as neccessary and will always
136 # remove itself from the runqueue
137 while (@destroy) { 168 while @destroy;
138 my $coro = pop @destroy;
139 $coro->{status} ||= [];
140 $_->ready for @{delete $coro->{join} || []};
141 169
142 # the next line destroys the _coro_state, but keeps the
143 # process itself intact (we basically make it a zombie
144 # process that always runs the manager thread, so it's possible
145 # to transfer() to this process).
146 $coro->{_coro_state} = $manager->{_coro_state};
147 }
148 &schedule; 170 &schedule;
149 } 171 }
150}; 172};
173$manager->desc ("[coro manager]");
174$manager->prio (PRIO_MAX);
151 175
152# static methods. not really. 176# static methods. not really.
153 177
154=back 178=back
155 179
156=head2 STATIC METHODS 180=head2 STATIC METHODS
157 181
158Static methods are actually functions that operate on the current process only. 182Static methods are actually functions that operate on the current coroutine only.
159 183
160=over 4 184=over 4
161 185
162=item async { ... } [@args...] 186=item async { ... } [@args...]
163 187
164Create a new asynchronous process and return it's process object 188Create a new asynchronous coroutine and return it's coroutine object
165(usually unused). When the sub returns the new process is automatically 189(usually unused). When the sub returns the new coroutine is automatically
166terminated. 190terminated.
191
192See the C<Coro::State::new> constructor for info about the coroutine
193environment.
194
195Calling C<exit> in a coroutine will do the same as calling exit outside
196the coroutine. Likewise, when the coroutine dies, the program will exit,
197just as it would in the main program.
167 198
168 # create a new coroutine that just prints its arguments 199 # create a new coroutine that just prints its arguments
169 async { 200 async {
170 print "@_\n"; 201 print "@_\n";
171 } 1,2,3,4; 202 } 1,2,3,4;
172 203
173=cut 204=cut
174 205
175sub async(&@) { 206sub async(&@) {
176 my $pid = new Coro @_; 207 my $coro = new Coro @_;
177 $manager->ready; # this ensures that the stack is cloned from the manager
178 $pid->ready; 208 $coro->ready;
179 $pid; 209 $coro
210}
211
212=item async_pool { ... } [@args...]
213
214Similar to C<async>, but uses a coroutine pool, so you should not call
215terminate or join (although you are allowed to), and you get a coroutine
216that might have executed other code already (which can be good or bad :).
217
218Also, the block is executed in an C<eval> context and a warning will be
219issued in case of an exception instead of terminating the program, as
220C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
221will not work in the expected way, unless you call terminate or cancel,
222which somehow defeats the purpose of pooling.
223
224The priority will be reset to C<0> after each job, tracing will be
225disabled, the description will be reset and the default output filehandle
226gets restored, so you can change alkl these. Otherwise the coroutine will
227be re-used "as-is": most notably if you change other per-coroutine global
228stuff such as C<$/> you need to revert that change, which is most simply
229done by using local as in C< local $/ >.
230
231The pool size is limited to 8 idle coroutines (this can be adjusted by
232changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
233required.
234
235If you are concerned about pooled coroutines growing a lot because a
236single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
237{ terminate }> once per second or so to slowly replenish the pool. In
238addition to that, when the stacks used by a handler grows larger than 16kb
239(adjustable with $Coro::POOL_RSS) it will also exit.
240
241=cut
242
243our $POOL_SIZE = 8;
244our $POOL_RSS = 16 * 1024;
245our @async_pool;
246
247sub pool_handler {
248 my $cb;
249
250 while () {
251 eval {
252 while () {
253 _pool_1 $cb;
254 &$cb;
255 _pool_2 $cb;
256 &schedule;
257 }
258 };
259
260 last if $@ eq "\3terminate\2\n";
261 warn $@ if $@;
262 }
263}
264
265sub async_pool(&@) {
266 # this is also inlined into the unlock_scheduler
267 my $coro = (pop @async_pool) || new Coro \&pool_handler;
268
269 $coro->{_invoke} = [@_];
270 $coro->ready;
271
272 $coro
180} 273}
181 274
182=item schedule 275=item schedule
183 276
184Calls the scheduler. Please note that the current process will not be put 277Calls the scheduler. Please note that the current coroutine will not be put
185into the ready queue, so calling this function usually means you will 278into the ready queue, so calling this function usually means you will
186never be called again. 279never be called again unless something else (e.g. an event handler) calls
280ready.
187 281
188=cut 282The canonical way to wait on external events is this:
283
284 {
285 # remember current coroutine
286 my $current = $Coro::current;
287
288 # register a hypothetical event handler
289 on_event_invoke sub {
290 # wake up sleeping coroutine
291 $current->ready;
292 undef $current;
293 };
294
295 # call schedule until event occurred.
296 # in case we are woken up for other reasons
297 # (current still defined), loop.
298 Coro::schedule while $current;
299 }
189 300
190=item cede 301=item cede
191 302
192"Cede" to other processes. This function puts the current process into the 303"Cede" to other coroutines. This function puts the current coroutine into the
193ready queue and calls C<schedule>, which has the effect of giving up the 304ready queue and calls C<schedule>, which has the effect of giving up the
194current "timeslice" to other coroutines of the same or higher priority. 305current "timeslice" to other coroutines of the same or higher priority.
195 306
196=cut 307Returns true if at least one coroutine switch has happened.
308
309=item Coro::cede_notself
310
311Works like cede, but is not exported by default and will cede to any
312coroutine, regardless of priority, once.
313
314Returns true if at least one coroutine switch has happened.
197 315
198=item terminate [arg...] 316=item terminate [arg...]
199 317
200Terminates the current process with the given status values (see L<cancel>). 318Terminates the current coroutine with the given status values (see L<cancel>).
319
320=item killall
321
322Kills/terminates/cancels all coroutines except the currently running
323one. This is useful after a fork, either in the child or the parent, as
324usually only one of them should inherit the running coroutines.
201 325
202=cut 326=cut
203 327
204sub terminate { 328sub terminate {
205 $current->cancel (@_); 329 $current->cancel (@_);
206} 330}
207 331
332sub killall {
333 for (Coro::State::list) {
334 $_->cancel
335 if $_ != $current && UNIVERSAL::isa $_, "Coro";
336 }
337}
338
208=back 339=back
209 340
210# dynamic methods 341# dynamic methods
211 342
212=head2 PROCESS METHODS 343=head2 COROUTINE METHODS
213 344
214These are the methods you can call on process objects. 345These are the methods you can call on coroutine objects.
215 346
216=over 4 347=over 4
217 348
218=item new Coro \&sub [, @args...] 349=item new Coro \&sub [, @args...]
219 350
220Create a new process and return it. When the sub returns the process 351Create a new coroutine and return it. When the sub returns the coroutine
221automatically terminates as if C<terminate> with the returned values were 352automatically terminates as if C<terminate> with the returned values were
222called. To make the process run you must first put it into the ready queue 353called. To make the coroutine run you must first put it into the ready queue
223by calling the ready method. 354by calling the ready method.
224 355
225=cut 356See C<async> and C<Coro::State::new> for additional info about the
357coroutine environment.
226 358
359=cut
360
227sub _newcoro { 361sub _run_coro {
228 terminate &{+shift}; 362 terminate &{+shift};
229} 363}
230 364
231sub new { 365sub new {
232 my $class = shift; 366 my $class = shift;
233 bless {
234 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
235 }, $class;
236}
237 367
238=item $process->ready 368 $class->SUPER::new (\&_run_coro, @_)
369}
239 370
240Put the given process into the ready queue. 371=item $success = $coroutine->ready
241 372
242=cut 373Put the given coroutine into the ready queue (according to it's priority)
374and return true. If the coroutine is already in the ready queue, do nothing
375and return false.
243 376
377=item $is_ready = $coroutine->is_ready
378
379Return wether the coroutine is currently the ready queue or not,
380
244=item $process->cancel (arg...) 381=item $coroutine->cancel (arg...)
245 382
246Temrinates the given process and makes it return the given arguments as 383Terminates the given coroutine and makes it return the given arguments as
247status (default: the empty list). 384status (default: the empty list). Never returns if the coroutine is the
385current coroutine.
248 386
249=cut 387=cut
250 388
251sub cancel { 389sub cancel {
252 my $self = shift; 390 my $self = shift;
253 $self->{status} = [@_]; 391 $self->{_status} = [@_];
392
393 if ($current == $self) {
254 push @destroy, $self; 394 push @destroy, $self;
255 $manager->ready; 395 $manager->ready;
256 &schedule if $current == $self; 396 &schedule while 1;
397 } else {
398 $self->_cancel;
399 }
257} 400}
258 401
259=item $process->join 402=item $coroutine->join
260 403
261Wait until the coroutine terminates and return any values given to the 404Wait until the coroutine terminates and return any values given to the
262C<terminate> or C<cancel> functions. C<join> can be called multiple times 405C<terminate> or C<cancel> functions. C<join> can be called concurrently
263from multiple processes. 406from multiple coroutines.
264 407
265=cut 408=cut
266 409
267sub join { 410sub join {
268 my $self = shift; 411 my $self = shift;
412
269 unless ($self->{status}) { 413 unless ($self->{_status}) {
270 push @{$self->{join}}, $current; 414 my $current = $current;
271 &schedule; 415
416 push @{$self->{_on_destroy}}, sub {
417 $current->ready;
418 undef $current;
419 };
420
421 &schedule while $current;
272 } 422 }
423
273 wantarray ? @{$self->{status}} : $self->{status}[0]; 424 wantarray ? @{$self->{_status}} : $self->{_status}[0];
274} 425}
275 426
427=item $coroutine->on_destroy (\&cb)
428
429Registers a callback that is called when this coroutine gets destroyed,
430but before it is joined. The callback gets passed the terminate arguments,
431if any.
432
433=cut
434
435sub on_destroy {
436 my ($self, $cb) = @_;
437
438 push @{ $self->{_on_destroy} }, $cb;
439}
440
276=item $oldprio = $process->prio($newprio) 441=item $oldprio = $coroutine->prio ($newprio)
277 442
278Sets (or gets, if the argument is missing) the priority of the 443Sets (or gets, if the argument is missing) the priority of the
279process. Higher priority processes get run before lower priority 444coroutine. Higher priority coroutines get run before lower priority
280processes. Priorities are small signed integers (currently -4 .. +3), 445coroutines. Priorities are small signed integers (currently -4 .. +3),
281that you can refer to using PRIO_xxx constants (use the import tag :prio 446that you can refer to using PRIO_xxx constants (use the import tag :prio
282to get then): 447to get then):
283 448
284 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 449 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
285 3 > 1 > 0 > -1 > -3 > -4 450 3 > 1 > 0 > -1 > -3 > -4
288 current->prio(PRIO_HIGH); 453 current->prio(PRIO_HIGH);
289 454
290The idle coroutine ($Coro::idle) always has a lower priority than any 455The idle coroutine ($Coro::idle) always has a lower priority than any
291existing coroutine. 456existing coroutine.
292 457
293Changing the priority of the current process will take effect immediately, 458Changing the priority of the current coroutine will take effect immediately,
294but changing the priority of processes in the ready queue (but not 459but changing the priority of coroutines in the ready queue (but not
295running) will only take effect after the next schedule (of that 460running) will only take effect after the next schedule (of that
296process). This is a bug that will be fixed in some future version. 461coroutine). This is a bug that will be fixed in some future version.
297 462
298=cut
299
300sub prio {
301 my $old = $_[0]{prio};
302 $_[0]{prio} = $_[1] if @_ > 1;
303 $old;
304}
305
306=item $newprio = $process->nice($change) 463=item $newprio = $coroutine->nice ($change)
307 464
308Similar to C<prio>, but subtract the given value from the priority (i.e. 465Similar to C<prio>, but subtract the given value from the priority (i.e.
309higher values mean lower priority, just as in unix). 466higher values mean lower priority, just as in unix).
310 467
311=cut
312
313sub nice {
314 $_[0]{prio} -= $_[1];
315}
316
317=item $olddesc = $process->desc($newdesc) 468=item $olddesc = $coroutine->desc ($newdesc)
318 469
319Sets (or gets in case the argument is missing) the description for this 470Sets (or gets in case the argument is missing) the description for this
320process. This is just a free-form string you can associate with a process. 471coroutine. This is just a free-form string you can associate with a coroutine.
472
473This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
474can modify this member directly if you wish.
321 475
322=cut 476=cut
323 477
324sub desc { 478sub desc {
325 my $old = $_[0]{desc}; 479 my $old = $_[0]{desc};
327 $old; 481 $old;
328} 482}
329 483
330=back 484=back
331 485
486=head2 GLOBAL FUNCTIONS
487
488=over 4
489
490=item Coro::nready
491
492Returns the number of coroutines that are currently in the ready state,
493i.e. that can be switched to. The value C<0> means that the only runnable
494coroutine is the currently running one, so C<cede> would have no effect,
495and C<schedule> would cause a deadlock unless there is an idle handler
496that wakes up some coroutines.
497
498=item my $guard = Coro::guard { ... }
499
500This creates and returns a guard object. Nothing happens until the object
501gets destroyed, in which case the codeblock given as argument will be
502executed. This is useful to free locks or other resources in case of a
503runtime error or when the coroutine gets canceled, as in both cases the
504guard block will be executed. The guard object supports only one method,
505C<< ->cancel >>, which will keep the codeblock from being executed.
506
507Example: set some flag and clear it again when the coroutine gets canceled
508or the function returns:
509
510 sub do_something {
511 my $guard = Coro::guard { $busy = 0 };
512 $busy = 1;
513
514 # do something that requires $busy to be true
515 }
516
517=cut
518
519sub guard(&) {
520 bless \(my $cb = $_[0]), "Coro::guard"
521}
522
523sub Coro::guard::cancel {
524 ${$_[0]} = sub { };
525}
526
527sub Coro::guard::DESTROY {
528 ${$_[0]}->();
529}
530
531
532=item unblock_sub { ... }
533
534This utility function takes a BLOCK or code reference and "unblocks" it,
535returning the new coderef. This means that the new coderef will return
536immediately without blocking, returning nothing, while the original code
537ref will be called (with parameters) from within its own coroutine.
538
539The reason this function exists is that many event libraries (such as the
540venerable L<Event|Event> module) are not coroutine-safe (a weaker form
541of thread-safety). This means you must not block within event callbacks,
542otherwise you might suffer from crashes or worse.
543
544This function allows your callbacks to block by executing them in another
545coroutine where it is safe to block. One example where blocking is handy
546is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
547disk.
548
549In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
550creating event callbacks that want to block.
551
552=cut
553
554our @unblock_queue;
555
556# we create a special coro because we want to cede,
557# to reduce pressure on the coro pool (because most callbacks
558# return immediately and can be reused) and because we cannot cede
559# inside an event callback.
560our $unblock_scheduler = new Coro sub {
561 while () {
562 while (my $cb = pop @unblock_queue) {
563 # this is an inlined copy of async_pool
564 my $coro = (pop @async_pool) || new Coro \&pool_handler;
565
566 $coro->{_invoke} = $cb;
567 $coro->ready;
568 cede; # for short-lived callbacks, this reduces pressure on the coro pool
569 }
570 schedule; # sleep well
571 }
572};
573$unblock_scheduler->desc ("[unblock_sub scheduler]");
574
575sub unblock_sub(&) {
576 my $cb = shift;
577
578 sub {
579 unshift @unblock_queue, [$cb, @_];
580 $unblock_scheduler->ready;
581 }
582}
583
584=back
585
332=cut 586=cut
333 587
3341; 5881;
335 589
336=head1 BUGS/LIMITATIONS 590=head1 BUGS/LIMITATIONS
337 591
338 - you must make very sure that no coro is still active on global 592 - you must make very sure that no coro is still active on global
339 destruction. very bad things might happen otherwise (usually segfaults). 593 destruction. very bad things might happen otherwise (usually segfaults).
340 594
341 - this module is not thread-safe. You should only ever use this module 595 - this module is not thread-safe. You should only ever use this module
342 from the same thread (this requirement might be losened in the future 596 from the same thread (this requirement might be loosened in the future
343 to allow per-thread schedulers, but Coro::State does not yet allow 597 to allow per-thread schedulers, but Coro::State does not yet allow
344 this). 598 this).
345 599
346=head1 SEE ALSO 600=head1 SEE ALSO
347 601
348Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>. 602Support/Utility: L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
349 603
350Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. 604Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
351 605
352Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>. 606Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
353 607

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