ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/cvsroot/Coro/Coro.pm
(Generate patch)

Comparing cvsroot/Coro/Coro.pm (file contents):
Revision 1.42 by root, Tue Nov 6 20:37:20 2001 UTC vs.
Revision 1.129 by root, Wed Sep 19 22:33:08 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 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@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
28callchain, it's own set of lexicals and it's own set of perl's most 37its own set of lexicals and its own set of perls most important global
29important global variables. 38variables.
30 39
31=cut 40=cut
32 41
33package Coro; 42package Coro;
34 43
44use strict;
35no warnings qw(uninitialized); 45no warnings "uninitialized";
36 46
37use Coro::State; 47use Coro::State;
38 48
39use base Exporter; 49use base qw(Coro::State Exporter);
40 50
41$VERSION = 0.52; 51our $idle; # idle handler
52our $main; # main coroutine
53our $current; # current coroutine
42 54
55our $VERSION = '3.7';
56
43@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
44%EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
45 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
46); 60);
47@EXPORT_OK = @{$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<$main> (of course).
111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essential you are encouraged to use the
114C<Coro::current> function instead.
91 115
92=cut 116=cut
93 117
94# maybe some other module used Coro::Specific before... 118# maybe some other module used Coro::Specific before...
95if ($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 {
164 $current->desc ("[coro manager]");
165
121 while() { 166 while () {
122 # by overwriting the state object with the manager we destroy it 167 (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) { 168 while @destroy;
128 my $coro = pop @destroy; 169
129 $coro->{status} ||= [];
130 $_->ready for @{delete $coro->{join} || []};
131 $coro->{_coro_state} = $manager->{_coro_state};
132 }
133 &schedule; 170 &schedule;
134 } 171 }
135}; 172};
136 173
174$manager->prio (PRIO_MAX);
175
137# static methods. not really. 176# static methods. not really.
138 177
178=back
179
139=head2 STATIC METHODS 180=head2 STATIC METHODS
140 181
141Static methods are actually functions that operate on the current process only. 182Static methods are actually functions that operate on the current coroutine only.
142 183
143=over 4 184=over 4
144 185
145=item async { ... } [@args...] 186=item async { ... } [@args...]
146 187
147Create a new asynchronous process and return it's process object 188Create a new asynchronous coroutine and return it's coroutine object
148(usually unused). When the sub returns the new process is automatically 189(usually unused). When the sub returns the new coroutine is automatically
149terminated. 190terminated.
191
192Calling C<exit> in a coroutine will do the same as calling exit outside
193the coroutine. Likewise, when the coroutine dies, the program will exit,
194just as it would in the main program.
150 195
151 # create a new coroutine that just prints its arguments 196 # create a new coroutine that just prints its arguments
152 async { 197 async {
153 print "@_\n"; 198 print "@_\n";
154 } 1,2,3,4; 199 } 1,2,3,4;
155 200
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 201=cut
160 202
161sub async(&@) { 203sub async(&@) {
162 my $pid = new Coro @_; 204 my $coro = new Coro @_;
163 $manager->ready; # this ensures that the stack is cloned from the manager
164 $pid->ready; 205 $coro->ready;
165 $pid; 206 $coro
207}
208
209=item async_pool { ... } [@args...]
210
211Similar to C<async>, but uses a coroutine pool, so you should not call
212terminate or join (although you are allowed to), and you get a coroutine
213that might have executed other code already (which can be good or bad :).
214
215Also, the block is executed in an C<eval> context and a warning will be
216issued in case of an exception instead of terminating the program, as
217C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
218will not work in the expected way, unless you call terminate or cancel,
219which somehow defeats the purpose of pooling.
220
221The priority will be reset to C<0> after each job, otherwise the coroutine
222will be re-used "as-is".
223
224The pool size is limited to 8 idle coroutines (this can be adjusted by
225changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
226required.
227
228If you are concerned about pooled coroutines growing a lot because a
229single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {
230terminate }> once per second or so to slowly replenish the pool.
231
232=cut
233
234our $POOL_SIZE = 8;
235our @pool;
236
237sub pool_handler {
238 while () {
239 $current->{desc} = "[async_pool]";
240
241 eval {
242 my ($cb, @arg) = @{ delete $current->{_invoke} or return };
243 $cb->(@arg);
244 };
245 warn $@ if $@;
246
247 last if @pool >= $POOL_SIZE;
248
249 push @pool, $current;
250 $current->{desc} = "[async_pool idle]";
251 $current->save (Coro::State::SAVE_DEF);
252 $current->prio (0);
253 schedule;
254 }
255}
256
257sub async_pool(&@) {
258 # this is also inlined into the unlock_scheduler
259 my $coro = (pop @pool) || new Coro \&pool_handler;;
260
261 $coro->{_invoke} = [@_];
262 $coro->ready;
263
264 $coro
166} 265}
167 266
168=item schedule 267=item schedule
169 268
170Calls the scheduler. Please note that the current process will not be put 269Calls the scheduler. Please note that the current coroutine will not be put
171into the ready queue, so calling this function usually means you will 270into the ready queue, so calling this function usually means you will
172never be called again. 271never be called again unless something else (e.g. an event handler) calls
272ready.
173 273
174=cut 274The canonical way to wait on external events is this:
275
276 {
277 # remember current coroutine
278 my $current = $Coro::current;
279
280 # register a hypothetical event handler
281 on_event_invoke sub {
282 # wake up sleeping coroutine
283 $current->ready;
284 undef $current;
285 };
286
287 # call schedule until event occurred.
288 # in case we are woken up for other reasons
289 # (current still defined), loop.
290 Coro::schedule while $current;
291 }
175 292
176=item cede 293=item cede
177 294
178"Cede" to other processes. This function puts the current process into the 295"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 296ready queue and calls C<schedule>, which has the effect of giving up the
180current "timeslice" to other coroutines of the same or higher priority. 297current "timeslice" to other coroutines of the same or higher priority.
181 298
182=cut 299Returns true if at least one coroutine switch has happened.
300
301=item Coro::cede_notself
302
303Works like cede, but is not exported by default and will cede to any
304coroutine, regardless of priority, once.
305
306Returns true if at least one coroutine switch has happened.
183 307
184=item terminate [arg...] 308=item terminate [arg...]
185 309
186Terminates the current process. 310Terminates the current coroutine with the given status values (see L<cancel>).
187
188Future versions of this function will allow result arguments.
189 311
190=cut 312=cut
191 313
192sub terminate { 314sub terminate {
193 $current->{status} = [@_];
194 $current->cancel; 315 $current->cancel (@_);
195 &schedule;
196 die; # NORETURN
197} 316}
198 317
199=back 318=back
200 319
201# dynamic methods 320# dynamic methods
202 321
203=head2 PROCESS METHODS 322=head2 COROUTINE METHODS
204 323
205These are the methods you can call on process objects. 324These are the methods you can call on coroutine objects.
206 325
207=over 4 326=over 4
208 327
209=item new Coro \&sub [, @args...] 328=item new Coro \&sub [, @args...]
210 329
211Create a new process and return it. When the sub returns the process 330Create a new coroutine and return it. When the sub returns the coroutine
212automatically terminates as if C<terminate> with the returned values were 331automatically 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 332called. To make the coroutine run you must first put it into the ready queue
214by calling the ready method. 333by calling the ready method.
215 334
216=cut 335See C<async> for additional discussion.
217 336
337=cut
338
218sub _newcoro { 339sub _run_coro {
219 terminate &{+shift}; 340 terminate &{+shift};
220} 341}
221 342
222sub new { 343sub new {
223 my $class = shift; 344 my $class = shift;
224 bless {
225 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
226 }, $class;
227}
228 345
229=item $process->ready 346 $class->SUPER::new (\&_run_coro, @_)
347}
230 348
231Put the given process into the ready queue. 349=item $success = $coroutine->ready
232 350
233=cut 351Put the given coroutine into the ready queue (according to it's priority)
352and return true. If the coroutine is already in the ready queue, do nothing
353and return false.
234 354
235=item $process->cancel 355=item $is_ready = $coroutine->is_ready
236 356
237Like C<terminate>, but terminates the specified process instead. 357Return wether the coroutine is currently the ready queue or not,
358
359=item $coroutine->cancel (arg...)
360
361Terminates the given coroutine and makes it return the given arguments as
362status (default: the empty list). Never returns if the coroutine is the
363current coroutine.
238 364
239=cut 365=cut
240 366
241sub cancel { 367sub cancel {
368 my $self = shift;
369 $self->{status} = [@_];
370
371 if ($current == $self) {
242 push @destroy, $_[0]; 372 push @destroy, $self;
243 $manager->ready; 373 $manager->ready;
244 &schedule if $current == $_[0]; 374 &schedule while 1;
375 } else {
376 $self->_cancel;
377 }
245} 378}
246 379
247=item $process->join 380=item $coroutine->join
248 381
249Wait until the coroutine terminates and return any values given to the 382Wait until the coroutine terminates and return any values given to the
250C<terminate> function. C<join> can be called multiple times from multiple 383C<terminate> or C<cancel> functions. C<join> can be called multiple times
251processes. 384from multiple coroutine.
252 385
253=cut 386=cut
254 387
255sub join { 388sub join {
256 my $self = shift; 389 my $self = shift;
390
257 unless ($self->{status}) { 391 unless ($self->{status}) {
258 push @{$self->{join}}, $current; 392 my $current = $current;
259 &schedule; 393
394 push @{$self->{destroy_cb}}, sub {
395 $current->ready;
396 undef $current;
397 };
398
399 &schedule while $current;
260 } 400 }
401
261 wantarray ? @{$self->{status}} : $self->{status}[0]; 402 wantarray ? @{$self->{status}} : $self->{status}[0];
262} 403}
263 404
405=item $coroutine->on_destroy (\&cb)
406
407Registers a callback that is called when this coroutine gets destroyed,
408but before it is joined. The callback gets passed the terminate arguments,
409if any.
410
411=cut
412
413sub on_destroy {
414 my ($self, $cb) = @_;
415
416 push @{ $self->{destroy_cb} }, $cb;
417}
418
264=item $oldprio = $process->prio($newprio) 419=item $oldprio = $coroutine->prio ($newprio)
265 420
266Sets (or gets, if the argument is missing) the priority of the 421Sets (or gets, if the argument is missing) the priority of the
267process. Higher priority processes get run before lower priority 422coroutine. Higher priority coroutines get run before lower priority
268processes. Priorities are smalled signed integer (currently -4 .. +3), 423coroutines. Priorities are small signed integers (currently -4 .. +3),
269that you can refer to using PRIO_xxx constants (use the import tag :prio 424that you can refer to using PRIO_xxx constants (use the import tag :prio
270to get then): 425to get then):
271 426
272 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 427 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
273 3 > 1 > 0 > -1 > -3 > -4 428 3 > 1 > 0 > -1 > -3 > -4
276 current->prio(PRIO_HIGH); 431 current->prio(PRIO_HIGH);
277 432
278The idle coroutine ($Coro::idle) always has a lower priority than any 433The idle coroutine ($Coro::idle) always has a lower priority than any
279existing coroutine. 434existing coroutine.
280 435
281Changing the priority of the current process will take effect immediately, 436Changing the priority of the current coroutine will take effect immediately,
282but changing the priority of processes in the ready queue (but not 437but changing the priority of coroutines in the ready queue (but not
283running) will only take effect after the next schedule (of that 438running) will only take effect after the next schedule (of that
284process). This is a bug that will be fixed in some future version. 439coroutine). This is a bug that will be fixed in some future version.
285 440
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) 441=item $newprio = $coroutine->nice ($change)
295 442
296Similar to C<prio>, but subtract the given value from the priority (i.e. 443Similar to C<prio>, but subtract the given value from the priority (i.e.
297higher values mean lower priority, just as in unix). 444higher values mean lower priority, just as in unix).
298 445
299=cut
300
301sub nice {
302 $_[0]{prio} -= $_[1];
303}
304
305=item $olddesc = $process->desc($newdesc) 446=item $olddesc = $coroutine->desc ($newdesc)
306 447
307Sets (or gets in case the argument is missing) the description for this 448Sets (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. 449coroutine. This is just a free-form string you can associate with a coroutine.
309 450
310=cut 451=cut
311 452
312sub desc { 453sub desc {
313 my $old = $_[0]{desc}; 454 my $old = $_[0]{desc};
315 $old; 456 $old;
316} 457}
317 458
318=back 459=back
319 460
461=head2 GLOBAL FUNCTIONS
462
463=over 4
464
465=item Coro::nready
466
467Returns the number of coroutines that are currently in the ready state,
468i.e. that can be switched to. The value C<0> means that the only runnable
469coroutine is the currently running one, so C<cede> would have no effect,
470and C<schedule> would cause a deadlock unless there is an idle handler
471that wakes up some coroutines.
472
473=item my $guard = Coro::guard { ... }
474
475This creates and returns a guard object. Nothing happens until the object
476gets destroyed, in which case the codeblock given as argument will be
477executed. This is useful to free locks or other resources in case of a
478runtime error or when the coroutine gets canceled, as in both cases the
479guard block will be executed. The guard object supports only one method,
480C<< ->cancel >>, which will keep the codeblock from being executed.
481
482Example: set some flag and clear it again when the coroutine gets canceled
483or the function returns:
484
485 sub do_something {
486 my $guard = Coro::guard { $busy = 0 };
487 $busy = 1;
488
489 # do something that requires $busy to be true
490 }
491
492=cut
493
494sub guard(&) {
495 bless \(my $cb = $_[0]), "Coro::guard"
496}
497
498sub Coro::guard::cancel {
499 ${$_[0]} = sub { };
500}
501
502sub Coro::guard::DESTROY {
503 ${$_[0]}->();
504}
505
506
507=item unblock_sub { ... }
508
509This utility function takes a BLOCK or code reference and "unblocks" it,
510returning the new coderef. This means that the new coderef will return
511immediately without blocking, returning nothing, while the original code
512ref will be called (with parameters) from within its own coroutine.
513
514The reason this function exists is that many event libraries (such as the
515venerable L<Event|Event> module) are not coroutine-safe (a weaker form
516of thread-safety). This means you must not block within event callbacks,
517otherwise you might suffer from crashes or worse.
518
519This function allows your callbacks to block by executing them in another
520coroutine where it is safe to block. One example where blocking is handy
521is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
522disk.
523
524In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
525creating event callbacks that want to block.
526
527=cut
528
529our @unblock_queue;
530
531# we create a special coro because we want to cede,
532# to reduce pressure on the coro pool (because most callbacks
533# return immediately and can be reused) and because we cannot cede
534# inside an event callback.
535our $unblock_scheduler = async {
536 $current->desc ("[unblock_sub scheduler]");
537 while () {
538 while (my $cb = pop @unblock_queue) {
539 # this is an inlined copy of async_pool
540 my $coro = (pop @pool or new Coro \&pool_handler);
541
542 $coro->{_invoke} = $cb;
543 $coro->ready;
544 cede; # for short-lived callbacks, this reduces pressure on the coro pool
545 }
546 schedule; # sleep well
547 }
548};
549
550sub unblock_sub(&) {
551 my $cb = shift;
552
553 sub {
554 unshift @unblock_queue, [$cb, @_];
555 $unblock_scheduler->ready;
556 }
557}
558
559=back
560
320=cut 561=cut
321 562
3221; 5631;
323 564
324=head1 BUGS/LIMITATIONS 565=head1 BUGS/LIMITATIONS
325 566
326 - you must make very sure that no coro is still active on global destruction. 567 - you must make very sure that no coro is still active on global
327 very bad things might happen otherwise (usually segfaults). 568 destruction. very bad things might happen otherwise (usually segfaults).
569
328 - this module is not thread-safe. You should only ever use this module from 570 - 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 571 from the same thread (this requirement might be loosened in the future
330 allow per-thread schedulers, but Coro::State does not yet allow this). 572 to allow per-thread schedulers, but Coro::State does not yet allow
573 this).
331 574
332=head1 SEE ALSO 575=head1 SEE ALSO
333 576
334L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 577Support/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>, 578
336L<Coro::Handle>, L<Coro::Socket>. 579Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
580
581Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
582
583Embedding: L<Coro:MakeMaker>
337 584
338=head1 AUTHOR 585=head1 AUTHOR
339 586
340 Marc Lehmann <pcg@goof.com> 587 Marc Lehmann <schmorp@schmorp.de>
341 http://www.goof.com/pcg/marc/ 588 http://home.schmorp.de/
342 589
343=cut 590=cut
344 591

Diff Legend

Removed lines
+ Added lines
< Changed lines
> Changed lines