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Revision 1.137 by root, Wed Sep 26 19:26:48 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 = '2.5'; 55our $VERSION = '3.7';
47 56
48our @EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
49our %EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
50 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
51); 60);
52our @EXPORT_OK = @{$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->{destroy_cb}) || []};
158}
159
160sub _do_trace {
161 $current->{_trace_cb}->();
162}
125 163
126# this coroutine is necessary because a coroutine 164# this coroutine is necessary because a coroutine
127# cannot destroy itself. 165# cannot destroy itself.
128my @destroy; 166my @destroy;
129my $manager; 167my $manager;
168
130$manager = new Coro sub { 169$manager = new Coro sub {
131 while () { 170 while () {
132 # by overwriting the state object with the manager we destroy it 171 (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) { 172 while @destroy;
138 my $coro = pop @destroy;
139 $coro->{status} ||= [];
140 $_->ready for @{delete $coro->{join} || []};
141 173
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} = $manager->{_coro_state};
147 }
148 &schedule; 174 &schedule;
149 } 175 }
150}; 176};
177$manager->desc ("[coro manager]");
178$manager->prio (PRIO_MAX);
151 179
152# static methods. not really. 180# static methods. not really.
153 181
154=back 182=back
155 183
156=head2 STATIC METHODS 184=head2 STATIC METHODS
157 185
158Static methods are actually functions that operate on the current process only. 186Static methods are actually functions that operate on the current coroutine only.
159 187
160=over 4 188=over 4
161 189
162=item async { ... } [@args...] 190=item async { ... } [@args...]
163 191
164Create a new asynchronous process and return it's process object 192Create a new asynchronous coroutine and return it's coroutine object
165(usually unused). When the sub returns the new process is automatically 193(usually unused). When the sub returns the new coroutine is automatically
166terminated. 194terminated.
167 195
168When the coroutine dies, the program will exit, just as in the main 196Calling C<exit> in a coroutine will do the same as calling exit outside
169program. 197the coroutine. Likewise, when the coroutine dies, the program will exit,
198just as it would in the main program.
170 199
171 # create a new coroutine that just prints its arguments 200 # create a new coroutine that just prints its arguments
172 async { 201 async {
173 print "@_\n"; 202 print "@_\n";
174 } 1,2,3,4; 203 } 1,2,3,4;
175 204
176=cut 205=cut
177 206
178sub async(&@) { 207sub async(&@) {
179 my $pid = new Coro @_; 208 my $coro = new Coro @_;
180 $manager->ready; # this ensures that the stack is cloned from the manager
181 $pid->ready; 209 $coro->ready;
182 $pid; 210 $coro
211}
212
213=item async_pool { ... } [@args...]
214
215Similar to C<async>, but uses a coroutine pool, so you should not call
216terminate or join (although you are allowed to), and you get a coroutine
217that might have executed other code already (which can be good or bad :).
218
219Also, the block is executed in an C<eval> context and a warning will be
220issued in case of an exception instead of terminating the program, as
221C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
222will not work in the expected way, unless you call terminate or cancel,
223which somehow defeats the purpose of pooling.
224
225The priority will be reset to C<0> after each job, otherwise the coroutine
226will be re-used "as-is".
227
228The pool size is limited to 8 idle coroutines (this can be adjusted by
229changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
230required.
231
232If you are concerned about pooled coroutines growing a lot because a
233single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
234{ terminate }> once per second or so to slowly replenish the pool. In
235addition to that, when the stacks used by a handler grows larger than 16kb
236(adjustable with $Coro::POOL_RSS) it will also exit.
237
238=cut
239
240our $POOL_SIZE = 8;
241our $POOL_RSS = 16 * 1024;
242our @async_pool;
243
244sub pool_handler {
245 my $cb;
246
247 while () {
248 eval {
249 while () {
250 _pool_1 $cb;
251 &$cb;
252 _pool_2 $cb;
253 &schedule;
254 }
255 };
256
257 last if $@ eq "\3terminate\2\n";
258 warn $@ if $@;
259 }
260}
261
262sub async_pool(&@) {
263 # this is also inlined into the unlock_scheduler
264 my $coro = (pop @async_pool) || new Coro \&pool_handler;
265
266 $coro->{_invoke} = [@_];
267 $coro->ready;
268
269 $coro
183} 270}
184 271
185=item schedule 272=item schedule
186 273
187Calls the scheduler. Please note that the current process will not be put 274Calls the scheduler. Please note that the current coroutine will not be put
188into the ready queue, so calling this function usually means you will 275into the ready queue, so calling this function usually means you will
189never be called again. 276never be called again unless something else (e.g. an event handler) calls
277ready.
190 278
191=cut 279The canonical way to wait on external events is this:
280
281 {
282 # remember current coroutine
283 my $current = $Coro::current;
284
285 # register a hypothetical event handler
286 on_event_invoke sub {
287 # wake up sleeping coroutine
288 $current->ready;
289 undef $current;
290 };
291
292 # call schedule until event occurred.
293 # in case we are woken up for other reasons
294 # (current still defined), loop.
295 Coro::schedule while $current;
296 }
192 297
193=item cede 298=item cede
194 299
195"Cede" to other processes. This function puts the current process into the 300"Cede" to other coroutines. This function puts the current coroutine into the
196ready queue and calls C<schedule>, which has the effect of giving up the 301ready queue and calls C<schedule>, which has the effect of giving up the
197current "timeslice" to other coroutines of the same or higher priority. 302current "timeslice" to other coroutines of the same or higher priority.
198 303
199=cut 304Returns true if at least one coroutine switch has happened.
305
306=item Coro::cede_notself
307
308Works like cede, but is not exported by default and will cede to any
309coroutine, regardless of priority, once.
310
311Returns true if at least one coroutine switch has happened.
200 312
201=item terminate [arg...] 313=item terminate [arg...]
202 314
203Terminates the current process with the given status values (see L<cancel>). 315Terminates the current coroutine with the given status values (see L<cancel>).
204 316
205=cut 317=cut
206 318
207sub terminate { 319sub terminate {
208 $current->cancel (@_); 320 $current->cancel (@_);
210 322
211=back 323=back
212 324
213# dynamic methods 325# dynamic methods
214 326
215=head2 PROCESS METHODS 327=head2 COROUTINE METHODS
216 328
217These are the methods you can call on process objects. 329These are the methods you can call on coroutine objects.
218 330
219=over 4 331=over 4
220 332
221=item new Coro \&sub [, @args...] 333=item new Coro \&sub [, @args...]
222 334
223Create a new process and return it. When the sub returns the process 335Create a new coroutine and return it. When the sub returns the coroutine
224automatically terminates as if C<terminate> with the returned values were 336automatically terminates as if C<terminate> with the returned values were
225called. To make the process run you must first put it into the ready queue 337called. To make the coroutine run you must first put it into the ready queue
226by calling the ready method. 338by calling the ready method.
227 339
228=cut 340See C<async> for additional discussion.
229 341
342=cut
343
230sub _newcoro { 344sub _run_coro {
231 terminate &{+shift}; 345 terminate &{+shift};
232} 346}
233 347
234sub new { 348sub new {
235 my $class = shift; 349 my $class = shift;
236 bless {
237 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
238 }, $class;
239}
240 350
241=item $process->ready 351 $class->SUPER::new (\&_run_coro, @_)
352}
242 353
243Put the given process into the ready queue. 354=item $success = $coroutine->ready
244 355
245=cut 356Put the given coroutine into the ready queue (according to it's priority)
357and return true. If the coroutine is already in the ready queue, do nothing
358and return false.
246 359
360=item $is_ready = $coroutine->is_ready
361
362Return wether the coroutine is currently the ready queue or not,
363
247=item $process->cancel (arg...) 364=item $coroutine->cancel (arg...)
248 365
249Terminates the given process and makes it return the given arguments as 366Terminates the given coroutine and makes it return the given arguments as
250status (default: the empty list). 367status (default: the empty list). Never returns if the coroutine is the
368current coroutine.
251 369
252=cut 370=cut
253 371
254sub cancel { 372sub cancel {
255 my $self = shift; 373 my $self = shift;
256 $self->{status} = [@_]; 374 $self->{status} = [@_];
375
376 if ($current == $self) {
257 push @destroy, $self; 377 push @destroy, $self;
258 $manager->ready; 378 $manager->ready;
259 &schedule if $current == $self; 379 &schedule while 1;
380 } else {
381 $self->_cancel;
382 }
260} 383}
261 384
262=item $process->join 385=item $coroutine->join
263 386
264Wait until the coroutine terminates and return any values given to the 387Wait until the coroutine terminates and return any values given to the
265C<terminate> or C<cancel> functions. C<join> can be called multiple times 388C<terminate> or C<cancel> functions. C<join> can be called multiple times
266from multiple processes. 389from multiple coroutine.
267 390
268=cut 391=cut
269 392
270sub join { 393sub join {
271 my $self = shift; 394 my $self = shift;
395
272 unless ($self->{status}) { 396 unless ($self->{status}) {
273 push @{$self->{join}}, $current; 397 my $current = $current;
274 &schedule; 398
399 push @{$self->{destroy_cb}}, sub {
400 $current->ready;
401 undef $current;
402 };
403
404 &schedule while $current;
275 } 405 }
406
276 wantarray ? @{$self->{status}} : $self->{status}[0]; 407 wantarray ? @{$self->{status}} : $self->{status}[0];
277} 408}
278 409
410=item $coroutine->on_destroy (\&cb)
411
412Registers a callback that is called when this coroutine gets destroyed,
413but before it is joined. The callback gets passed the terminate arguments,
414if any.
415
416=cut
417
418sub on_destroy {
419 my ($self, $cb) = @_;
420
421 push @{ $self->{destroy_cb} }, $cb;
422}
423
279=item $oldprio = $process->prio($newprio) 424=item $oldprio = $coroutine->prio ($newprio)
280 425
281Sets (or gets, if the argument is missing) the priority of the 426Sets (or gets, if the argument is missing) the priority of the
282process. Higher priority processes get run before lower priority 427coroutine. Higher priority coroutines get run before lower priority
283processes. Priorities are small signed integers (currently -4 .. +3), 428coroutines. Priorities are small signed integers (currently -4 .. +3),
284that you can refer to using PRIO_xxx constants (use the import tag :prio 429that you can refer to using PRIO_xxx constants (use the import tag :prio
285to get then): 430to get then):
286 431
287 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 432 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
288 3 > 1 > 0 > -1 > -3 > -4 433 3 > 1 > 0 > -1 > -3 > -4
291 current->prio(PRIO_HIGH); 436 current->prio(PRIO_HIGH);
292 437
293The idle coroutine ($Coro::idle) always has a lower priority than any 438The idle coroutine ($Coro::idle) always has a lower priority than any
294existing coroutine. 439existing coroutine.
295 440
296Changing the priority of the current process will take effect immediately, 441Changing the priority of the current coroutine will take effect immediately,
297but changing the priority of processes in the ready queue (but not 442but changing the priority of coroutines in the ready queue (but not
298running) will only take effect after the next schedule (of that 443running) will only take effect after the next schedule (of that
299process). This is a bug that will be fixed in some future version. 444coroutine). This is a bug that will be fixed in some future version.
300 445
301=cut
302
303sub prio {
304 my $old = $_[0]{prio};
305 $_[0]{prio} = $_[1] if @_ > 1;
306 $old;
307}
308
309=item $newprio = $process->nice($change) 446=item $newprio = $coroutine->nice ($change)
310 447
311Similar to C<prio>, but subtract the given value from the priority (i.e. 448Similar to C<prio>, but subtract the given value from the priority (i.e.
312higher values mean lower priority, just as in unix). 449higher values mean lower priority, just as in unix).
313 450
314=cut
315
316sub nice {
317 $_[0]{prio} -= $_[1];
318}
319
320=item $olddesc = $process->desc($newdesc) 451=item $olddesc = $coroutine->desc ($newdesc)
321 452
322Sets (or gets in case the argument is missing) the description for this 453Sets (or gets in case the argument is missing) the description for this
323process. This is just a free-form string you can associate with a process. 454coroutine. This is just a free-form string you can associate with a coroutine.
324 455
325=cut 456=cut
326 457
327sub desc { 458sub desc {
328 my $old = $_[0]{desc}; 459 my $old = $_[0]{desc};
330 $old; 461 $old;
331} 462}
332 463
333=back 464=back
334 465
466=head2 GLOBAL FUNCTIONS
467
468=over 4
469
470=item Coro::nready
471
472Returns the number of coroutines that are currently in the ready state,
473i.e. that can be switched to. The value C<0> means that the only runnable
474coroutine is the currently running one, so C<cede> would have no effect,
475and C<schedule> would cause a deadlock unless there is an idle handler
476that wakes up some coroutines.
477
478=item my $guard = Coro::guard { ... }
479
480This creates and returns a guard object. Nothing happens until the object
481gets destroyed, in which case the codeblock given as argument will be
482executed. This is useful to free locks or other resources in case of a
483runtime error or when the coroutine gets canceled, as in both cases the
484guard block will be executed. The guard object supports only one method,
485C<< ->cancel >>, which will keep the codeblock from being executed.
486
487Example: set some flag and clear it again when the coroutine gets canceled
488or the function returns:
489
490 sub do_something {
491 my $guard = Coro::guard { $busy = 0 };
492 $busy = 1;
493
494 # do something that requires $busy to be true
495 }
496
497=cut
498
499sub guard(&) {
500 bless \(my $cb = $_[0]), "Coro::guard"
501}
502
503sub Coro::guard::cancel {
504 ${$_[0]} = sub { };
505}
506
507sub Coro::guard::DESTROY {
508 ${$_[0]}->();
509}
510
511
512=item unblock_sub { ... }
513
514This utility function takes a BLOCK or code reference and "unblocks" it,
515returning the new coderef. This means that the new coderef will return
516immediately without blocking, returning nothing, while the original code
517ref will be called (with parameters) from within its own coroutine.
518
519The reason this function exists is that many event libraries (such as the
520venerable L<Event|Event> module) are not coroutine-safe (a weaker form
521of thread-safety). This means you must not block within event callbacks,
522otherwise you might suffer from crashes or worse.
523
524This function allows your callbacks to block by executing them in another
525coroutine where it is safe to block. One example where blocking is handy
526is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
527disk.
528
529In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
530creating event callbacks that want to block.
531
532=cut
533
534our @unblock_queue;
535
536# we create a special coro because we want to cede,
537# to reduce pressure on the coro pool (because most callbacks
538# return immediately and can be reused) and because we cannot cede
539# inside an event callback.
540our $unblock_scheduler = new Coro sub {
541 while () {
542 while (my $cb = pop @unblock_queue) {
543 # this is an inlined copy of async_pool
544 my $coro = (pop @async_pool) || new Coro \&pool_handler;
545
546 $coro->{_invoke} = $cb;
547 $coro->ready;
548 cede; # for short-lived callbacks, this reduces pressure on the coro pool
549 }
550 schedule; # sleep well
551 }
552};
553$unblock_scheduler->desc ("[unblock_sub scheduler]");
554
555sub unblock_sub(&) {
556 my $cb = shift;
557
558 sub {
559 unshift @unblock_queue, [$cb, @_];
560 $unblock_scheduler->ready;
561 }
562}
563
564=back
565
335=cut 566=cut
336 567
3371; 5681;
338 569
339=head1 BUGS/LIMITATIONS 570=head1 BUGS/LIMITATIONS
340 571
341 - you must make very sure that no coro is still active on global 572 - you must make very sure that no coro is still active on global
342 destruction. very bad things might happen otherwise (usually segfaults). 573 destruction. very bad things might happen otherwise (usually segfaults).
343 574
344 - this module is not thread-safe. You should only ever use this module 575 - this module is not thread-safe. You should only ever use this module
345 from the same thread (this requirement might be losened in the future 576 from the same thread (this requirement might be loosened in the future
346 to allow per-thread schedulers, but Coro::State does not yet allow 577 to allow per-thread schedulers, but Coro::State does not yet allow
347 this). 578 this).
348 579
349=head1 SEE ALSO 580=head1 SEE ALSO
350 581

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