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Revision 1.139 by root, Thu Sep 27 15:52:30 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 = 1.9; 55our $VERSION = '3.8';
47 56
48our @EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
49our %EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
50 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
51); 60);
52our @EXPORT_OK = @{$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 $self->{destroy_cb}) || []};
158}
159
160sub _do_trace_sub {
161 &{$current->{_trace_sub_cb}}
162}
163
164sub _do_trace_line {
165 &{$current->{_trace_line_cb}}
166}
125 167
126# this coroutine is necessary because a coroutine 168# this coroutine is necessary because a coroutine
127# cannot destroy itself. 169# cannot destroy itself.
128my @destroy; 170my @destroy;
129my $manager; 171my $manager;
172
130$manager = new Coro sub { 173$manager = new Coro sub {
131 while () { 174 while () {
132 # by overwriting the state object with the manager we destroy it 175 (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) { 176 while @destroy;
138 my $coro = pop @destroy;
139 $coro->{status} ||= [];
140 $_->ready for @{delete $coro->{join} || []};
141 177
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} = $manager->{_coro_state};
147 }
148 &schedule; 178 &schedule;
149 } 179 }
150}; 180};
181$manager->desc ("[coro manager]");
182$manager->prio (PRIO_MAX);
151 183
152# static methods. not really. 184# static methods. not really.
153 185
154=back 186=back
155 187
156=head2 STATIC METHODS 188=head2 STATIC METHODS
157 189
158Static methods are actually functions that operate on the current process only. 190Static methods are actually functions that operate on the current coroutine only.
159 191
160=over 4 192=over 4
161 193
162=item async { ... } [@args...] 194=item async { ... } [@args...]
163 195
164Create a new asynchronous process and return it's process object 196Create a new asynchronous coroutine and return it's coroutine object
165(usually unused). When the sub returns the new process is automatically 197(usually unused). When the sub returns the new coroutine is automatically
166terminated. 198terminated.
199
200Calling C<exit> in a coroutine will do the same as calling exit outside
201the coroutine. Likewise, when the coroutine dies, the program will exit,
202just as it would in the main program.
167 203
168 # create a new coroutine that just prints its arguments 204 # create a new coroutine that just prints its arguments
169 async { 205 async {
170 print "@_\n"; 206 print "@_\n";
171 } 1,2,3,4; 207 } 1,2,3,4;
172 208
173=cut 209=cut
174 210
175sub async(&@) { 211sub async(&@) {
176 my $pid = new Coro @_; 212 my $coro = new Coro @_;
177 $manager->ready; # this ensures that the stack is cloned from the manager
178 $pid->ready; 213 $coro->ready;
179 $pid; 214 $coro
215}
216
217=item async_pool { ... } [@args...]
218
219Similar to C<async>, but uses a coroutine pool, so you should not call
220terminate or join (although you are allowed to), and you get a coroutine
221that might have executed other code already (which can be good or bad :).
222
223Also, the block is executed in an C<eval> context and a warning will be
224issued in case of an exception instead of terminating the program, as
225C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
226will not work in the expected way, unless you call terminate or cancel,
227which somehow defeats the purpose of pooling.
228
229The priority will be reset to C<0> after each job, otherwise the coroutine
230will be re-used "as-is".
231
232The pool size is limited to 8 idle coroutines (this can be adjusted by
233changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
234required.
235
236If you are concerned about pooled coroutines growing a lot because a
237single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
238{ terminate }> once per second or so to slowly replenish the pool. In
239addition to that, when the stacks used by a handler grows larger than 16kb
240(adjustable with $Coro::POOL_RSS) it will also exit.
241
242=cut
243
244our $POOL_SIZE = 8;
245our $POOL_RSS = 16 * 1024;
246our @async_pool;
247
248sub pool_handler {
249 my $cb;
250
251 while () {
252 eval {
253 while () {
254 _pool_1 $cb;
255 &$cb;
256 _pool_2 $cb;
257 &schedule;
258 }
259 };
260
261 last if $@ eq "\3terminate\2\n";
262 warn $@ if $@;
263 }
264}
265
266sub async_pool(&@) {
267 # this is also inlined into the unlock_scheduler
268 my $coro = (pop @async_pool) || new Coro \&pool_handler;
269
270 $coro->{_invoke} = [@_];
271 $coro->ready;
272
273 $coro
180} 274}
181 275
182=item schedule 276=item schedule
183 277
184Calls the scheduler. Please note that the current process will not be put 278Calls the scheduler. Please note that the current coroutine will not be put
185into the ready queue, so calling this function usually means you will 279into the ready queue, so calling this function usually means you will
186never be called again. 280never be called again unless something else (e.g. an event handler) calls
281ready.
187 282
188=cut 283The canonical way to wait on external events is this:
284
285 {
286 # remember current coroutine
287 my $current = $Coro::current;
288
289 # register a hypothetical event handler
290 on_event_invoke sub {
291 # wake up sleeping coroutine
292 $current->ready;
293 undef $current;
294 };
295
296 # call schedule until event occurred.
297 # in case we are woken up for other reasons
298 # (current still defined), loop.
299 Coro::schedule while $current;
300 }
189 301
190=item cede 302=item cede
191 303
192"Cede" to other processes. This function puts the current process into the 304"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 305ready queue and calls C<schedule>, which has the effect of giving up the
194current "timeslice" to other coroutines of the same or higher priority. 306current "timeslice" to other coroutines of the same or higher priority.
195 307
196=cut 308Returns true if at least one coroutine switch has happened.
309
310=item Coro::cede_notself
311
312Works like cede, but is not exported by default and will cede to any
313coroutine, regardless of priority, once.
314
315Returns true if at least one coroutine switch has happened.
197 316
198=item terminate [arg...] 317=item terminate [arg...]
199 318
200Terminates the current process with the given status values (see L<cancel>). 319Terminates the current coroutine with the given status values (see L<cancel>).
201 320
202=cut 321=cut
203 322
204sub terminate { 323sub terminate {
205 $current->cancel (@_); 324 $current->cancel (@_);
207 326
208=back 327=back
209 328
210# dynamic methods 329# dynamic methods
211 330
212=head2 PROCESS METHODS 331=head2 COROUTINE METHODS
213 332
214These are the methods you can call on process objects. 333These are the methods you can call on coroutine objects.
215 334
216=over 4 335=over 4
217 336
218=item new Coro \&sub [, @args...] 337=item new Coro \&sub [, @args...]
219 338
220Create a new process and return it. When the sub returns the process 339Create a new coroutine and return it. When the sub returns the coroutine
221automatically terminates as if C<terminate> with the returned values were 340automatically 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 341called. To make the coroutine run you must first put it into the ready queue
223by calling the ready method. 342by calling the ready method.
224 343
225=cut 344See C<async> for additional discussion.
226 345
346=cut
347
227sub _newcoro { 348sub _run_coro {
228 terminate &{+shift}; 349 terminate &{+shift};
229} 350}
230 351
231sub new { 352sub new {
232 my $class = shift; 353 my $class = shift;
233 bless {
234 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
235 }, $class;
236}
237 354
238=item $process->ready 355 $class->SUPER::new (\&_run_coro, @_)
356}
239 357
240Put the given process into the ready queue. 358=item $success = $coroutine->ready
241 359
242=cut 360Put the given coroutine into the ready queue (according to it's priority)
361and return true. If the coroutine is already in the ready queue, do nothing
362and return false.
243 363
364=item $is_ready = $coroutine->is_ready
365
366Return wether the coroutine is currently the ready queue or not,
367
244=item $process->cancel (arg...) 368=item $coroutine->cancel (arg...)
245 369
246Temrinates the given process and makes it return the given arguments as 370Terminates the given coroutine and makes it return the given arguments as
247status (default: the empty list). 371status (default: the empty list). Never returns if the coroutine is the
372current coroutine.
248 373
249=cut 374=cut
250 375
251sub cancel { 376sub cancel {
252 my $self = shift; 377 my $self = shift;
253 $self->{status} = [@_]; 378 $self->{status} = [@_];
379
380 if ($current == $self) {
254 push @destroy, $self; 381 push @destroy, $self;
255 $manager->ready; 382 $manager->ready;
256 &schedule if $current == $self; 383 &schedule while 1;
384 } else {
385 $self->_cancel;
386 }
257} 387}
258 388
259=item $process->join 389=item $coroutine->join
260 390
261Wait until the coroutine terminates and return any values given to the 391Wait until the coroutine terminates and return any values given to the
262C<terminate> or C<cancel> functions. C<join> can be called multiple times 392C<terminate> or C<cancel> functions. C<join> can be called multiple times
263from multiple processes. 393from multiple coroutine.
264 394
265=cut 395=cut
266 396
267sub join { 397sub join {
268 my $self = shift; 398 my $self = shift;
399
269 unless ($self->{status}) { 400 unless ($self->{status}) {
270 push @{$self->{join}}, $current; 401 my $current = $current;
271 &schedule; 402
403 push @{$self->{destroy_cb}}, sub {
404 $current->ready;
405 undef $current;
406 };
407
408 &schedule while $current;
272 } 409 }
410
273 wantarray ? @{$self->{status}} : $self->{status}[0]; 411 wantarray ? @{$self->{status}} : $self->{status}[0];
274} 412}
275 413
414=item $coroutine->on_destroy (\&cb)
415
416Registers a callback that is called when this coroutine gets destroyed,
417but before it is joined. The callback gets passed the terminate arguments,
418if any.
419
420=cut
421
422sub on_destroy {
423 my ($self, $cb) = @_;
424
425 push @{ $self->{destroy_cb} }, $cb;
426}
427
276=item $oldprio = $process->prio($newprio) 428=item $oldprio = $coroutine->prio ($newprio)
277 429
278Sets (or gets, if the argument is missing) the priority of the 430Sets (or gets, if the argument is missing) the priority of the
279process. Higher priority processes get run before lower priority 431coroutine. Higher priority coroutines get run before lower priority
280processes. Priorities are small signed integers (currently -4 .. +3), 432coroutines. Priorities are small signed integers (currently -4 .. +3),
281that you can refer to using PRIO_xxx constants (use the import tag :prio 433that you can refer to using PRIO_xxx constants (use the import tag :prio
282to get then): 434to get then):
283 435
284 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 436 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
285 3 > 1 > 0 > -1 > -3 > -4 437 3 > 1 > 0 > -1 > -3 > -4
288 current->prio(PRIO_HIGH); 440 current->prio(PRIO_HIGH);
289 441
290The idle coroutine ($Coro::idle) always has a lower priority than any 442The idle coroutine ($Coro::idle) always has a lower priority than any
291existing coroutine. 443existing coroutine.
292 444
293Changing the priority of the current process will take effect immediately, 445Changing the priority of the current coroutine will take effect immediately,
294but changing the priority of processes in the ready queue (but not 446but changing the priority of coroutines in the ready queue (but not
295running) will only take effect after the next schedule (of that 447running) will only take effect after the next schedule (of that
296process). This is a bug that will be fixed in some future version. 448coroutine). This is a bug that will be fixed in some future version.
297 449
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) 450=item $newprio = $coroutine->nice ($change)
307 451
308Similar to C<prio>, but subtract the given value from the priority (i.e. 452Similar to C<prio>, but subtract the given value from the priority (i.e.
309higher values mean lower priority, just as in unix). 453higher values mean lower priority, just as in unix).
310 454
311=cut
312
313sub nice {
314 $_[0]{prio} -= $_[1];
315}
316
317=item $olddesc = $process->desc($newdesc) 455=item $olddesc = $coroutine->desc ($newdesc)
318 456
319Sets (or gets in case the argument is missing) the description for this 457Sets (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. 458coroutine. This is just a free-form string you can associate with a coroutine.
321 459
322=cut 460=cut
323 461
324sub desc { 462sub desc {
325 my $old = $_[0]{desc}; 463 my $old = $_[0]{desc};
327 $old; 465 $old;
328} 466}
329 467
330=back 468=back
331 469
470=head2 GLOBAL FUNCTIONS
471
472=over 4
473
474=item Coro::nready
475
476Returns the number of coroutines that are currently in the ready state,
477i.e. that can be switched to. The value C<0> means that the only runnable
478coroutine is the currently running one, so C<cede> would have no effect,
479and C<schedule> would cause a deadlock unless there is an idle handler
480that wakes up some coroutines.
481
482=item my $guard = Coro::guard { ... }
483
484This creates and returns a guard object. Nothing happens until the object
485gets destroyed, in which case the codeblock given as argument will be
486executed. This is useful to free locks or other resources in case of a
487runtime error or when the coroutine gets canceled, as in both cases the
488guard block will be executed. The guard object supports only one method,
489C<< ->cancel >>, which will keep the codeblock from being executed.
490
491Example: set some flag and clear it again when the coroutine gets canceled
492or the function returns:
493
494 sub do_something {
495 my $guard = Coro::guard { $busy = 0 };
496 $busy = 1;
497
498 # do something that requires $busy to be true
499 }
500
501=cut
502
503sub guard(&) {
504 bless \(my $cb = $_[0]), "Coro::guard"
505}
506
507sub Coro::guard::cancel {
508 ${$_[0]} = sub { };
509}
510
511sub Coro::guard::DESTROY {
512 ${$_[0]}->();
513}
514
515
516=item unblock_sub { ... }
517
518This utility function takes a BLOCK or code reference and "unblocks" it,
519returning the new coderef. This means that the new coderef will return
520immediately without blocking, returning nothing, while the original code
521ref will be called (with parameters) from within its own coroutine.
522
523The reason this function exists is that many event libraries (such as the
524venerable L<Event|Event> module) are not coroutine-safe (a weaker form
525of thread-safety). This means you must not block within event callbacks,
526otherwise you might suffer from crashes or worse.
527
528This function allows your callbacks to block by executing them in another
529coroutine where it is safe to block. One example where blocking is handy
530is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
531disk.
532
533In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
534creating event callbacks that want to block.
535
536=cut
537
538our @unblock_queue;
539
540# we create a special coro because we want to cede,
541# to reduce pressure on the coro pool (because most callbacks
542# return immediately and can be reused) and because we cannot cede
543# inside an event callback.
544our $unblock_scheduler = new Coro sub {
545 while () {
546 while (my $cb = pop @unblock_queue) {
547 # this is an inlined copy of async_pool
548 my $coro = (pop @async_pool) || new Coro \&pool_handler;
549
550 $coro->{_invoke} = $cb;
551 $coro->ready;
552 cede; # for short-lived callbacks, this reduces pressure on the coro pool
553 }
554 schedule; # sleep well
555 }
556};
557$unblock_scheduler->desc ("[unblock_sub scheduler]");
558
559sub unblock_sub(&) {
560 my $cb = shift;
561
562 sub {
563 unshift @unblock_queue, [$cb, @_];
564 $unblock_scheduler->ready;
565 }
566}
567
568=back
569
332=cut 570=cut
333 571
3341; 5721;
335 573
336=head1 BUGS/LIMITATIONS 574=head1 BUGS/LIMITATIONS
337 575
338 - you must make very sure that no coro is still active on global 576 - you must make very sure that no coro is still active on global
339 destruction. very bad things might happen otherwise (usually segfaults). 577 destruction. very bad things might happen otherwise (usually segfaults).
340 578
341 - this module is not thread-safe. You should only ever use this module 579 - 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 580 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 581 to allow per-thread schedulers, but Coro::State does not yet allow
344 this). 582 this).
345 583
346=head1 SEE ALSO 584=head1 SEE ALSO
347 585

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