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Revision 1.24 by root, Wed Jul 25 04:14:37 2001 UTC vs.
Revision 1.179 by root, Sat Apr 19 19:06:02 2008 UTC

2 2
3Coro - coroutine process abstraction 3Coro - coroutine process abstraction
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use Coro; 7 use Coro;
8 8
9 async { 9 async {
10 # some asynchronous thread of execution 10 # some asynchronous thread of execution
11 print "2\n";
12 cede; # yield back to main
13 print "4\n";
11 }; 14 };
12 15 print "1\n";
13 # alternatively create an async process like this: 16 cede; # yield to coroutine
14 17 print "3\n";
15 sub some_func : Coro { 18 cede; # and again
16 # some more async code 19
17 } 20 # use locking
18 21 my $lock = new Coro::Semaphore;
19 cede; 22 my $locked;
23
24 $lock->down;
25 $locked = 1;
26 $lock->up;
20 27
21=head1 DESCRIPTION 28=head1 DESCRIPTION
22 29
23This module collection manages coroutines. Coroutines are similar to 30This module collection manages coroutines. Coroutines are similar
24Threads but don't run in parallel. 31to threads but don't run in parallel at the same time even on SMP
32machines. The specific flavor of coroutine used in this module also
33guarantees you that it will not switch between coroutines unless
34necessary, at easily-identified points in your program, so locking and
35parallel access are rarely an issue, making coroutine programming much
36safer than threads programming.
25 37
26This module is still experimental, see the BUGS section below. 38(Perl, however, does not natively support real threads but instead does a
39very slow and memory-intensive emulation of processes using threads. This
40is a performance win on Windows machines, and a loss everywhere else).
27 41
28In this module, coroutines are defined as "callchain + lexical variables 42In this module, coroutines are defined as "callchain + lexical variables +
29+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own 43@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
30callchain, it's own set of lexicals and it's own set of perl's most 44its own set of lexicals and its own set of perls most important global
31important global variables. 45variables (see L<Coro::State> for more configuration).
32 46
33=cut 47=cut
34 48
35package Coro; 49package Coro;
36 50
51use strict;
52no warnings "uninitialized";
53
37use Coro::State; 54use Coro::State;
38 55
39use base Exporter; 56use base qw(Coro::State Exporter);
40 57
41$VERSION = 0.12; 58our $idle; # idle handler
59our $main; # main coroutine
60our $current; # current coroutine
42 61
62our $VERSION = '4.51';
63
43@EXPORT = qw(async cede schedule terminate current); 64our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
44@EXPORT_OK = qw($current); 65our %EXPORT_TAGS = (
66 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
67);
68our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
45 69
46{ 70=over 4
47 my @async;
48
49 # this way of handling attributes simply is NOT scalable ;()
50 sub import {
51 Coro->export_to_level(1, @_);
52 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
53 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
54 my ($package, $ref) = (shift, shift);
55 my @attrs;
56 for (@_) {
57 if ($_ eq "Coro") {
58 push @async, $ref;
59 } else {
60 push @attrs, $_;
61 }
62 }
63 return $old ? $old->($package, $ref, @attrs) : @attrs;
64 };
65 }
66
67 sub INIT {
68 &async(pop @async) while @async;
69 }
70}
71 71
72=item $main 72=item $main
73 73
74This coroutine represents the main program. 74This coroutine represents the main program.
75 75
76=cut 76=cut
77 77
78our $main = new Coro; 78$main = new Coro;
79 79
80=item $current (or as function: current) 80=item $current (or as function: current)
81 81
82The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). 82The current coroutine (the last coroutine switched to). The initial value
83is C<$main> (of course).
83 84
85This variable is B<strictly> I<read-only>. It is provided for performance
86reasons. If performance is not essential you are encouraged to use the
87C<Coro::current> function instead.
88
84=cut 89=cut
90
91$main->{desc} = "[main::]";
85 92
86# maybe some other module used Coro::Specific before... 93# maybe some other module used Coro::Specific before...
87if ($current) {
88 $main->{specific} = $current->{specific}; 94$main->{_specific} = $current->{_specific}
89} 95 if $current;
90 96
91our $current = $main; 97_set_current $main;
92 98
93sub current() { $current } 99sub current() { $current }
94 100
95=item $idle 101=item $idle
96 102
97The coroutine to switch to when no other coroutine is running. The default 103A callback that is called whenever the scheduler finds no ready coroutines
98implementation prints "FATAL: deadlock detected" and exits. 104to run. The default implementation prints "FATAL: deadlock detected" and
105exits, because the program has no other way to continue.
99 106
100=cut 107This hook is overwritten by modules such as C<Coro::Timer> and
108C<Coro::Event> to wait on an external event that hopefully wake up a
109coroutine so the scheduler can run it.
101 110
102# should be done using priorities :( 111Please note that if your callback recursively invokes perl (e.g. for event
103our $idle = new Coro sub { 112handlers), then it must be prepared to be called recursively itself.
104 print STDERR "FATAL: deadlock detected\n"; 113
105 exit(51); 114=cut
115
116$idle = sub {
117 require Carp;
118 Carp::croak ("FATAL: deadlock detected");
106}; 119};
120
121sub _cancel {
122 my ($self) = @_;
123
124 # free coroutine data and mark as destructed
125 $self->_destroy
126 or return;
127
128 # call all destruction callbacks
129 $_->(@{$self->{_status}})
130 for @{(delete $self->{_on_destroy}) || []};
131}
107 132
108# this coroutine is necessary because a coroutine 133# this coroutine is necessary because a coroutine
109# cannot destroy itself. 134# cannot destroy itself.
110my @destroy; 135my @destroy;
136my $manager;
137
111my $manager = new Coro sub { 138$manager = new Coro sub {
112 while() { 139 while () {
113 delete ((pop @destroy)->{_coro_state}) while @destroy; 140 (shift @destroy)->_cancel
141 while @destroy;
142
114 &schedule; 143 &schedule;
115 } 144 }
116}; 145};
146$manager->desc ("[coro manager]");
147$manager->prio (PRIO_MAX);
117 148
118# we really need priorities... 149=back
119my @ready; # the ready queue. hehe, rather broken ;)
120
121# static methods. not really.
122 150
123=head2 STATIC METHODS 151=head2 STATIC METHODS
124 152
125Static methods are actually functions that operate on the current process only. 153Static methods are actually functions that operate on the current coroutine only.
126 154
127=over 4 155=over 4
128 156
129=item async { ... } [@args...] 157=item async { ... } [@args...]
130 158
131Create a new asynchronous process and return it's process object 159Create a new asynchronous coroutine and return it's coroutine object
132(usually unused). When the sub returns the new process is automatically 160(usually unused). When the sub returns the new coroutine is automatically
133terminated. 161terminated.
162
163See the C<Coro::State::new> constructor for info about the coroutine
164environment in which coroutines run.
165
166Calling C<exit> in a coroutine will do the same as calling exit outside
167the coroutine. Likewise, when the coroutine dies, the program will exit,
168just as it would in the main program.
134 169
135 # create a new coroutine that just prints its arguments 170 # create a new coroutine that just prints its arguments
136 async { 171 async {
137 print "@_\n"; 172 print "@_\n";
138 } 1,2,3,4; 173 } 1,2,3,4;
139 174
140The coderef you submit MUST NOT be a closure that refers to variables
141in an outer scope. This does NOT work. Pass arguments into it instead.
142
143=cut 175=cut
144 176
145sub async(&@) { 177sub async(&@) {
146 my $pid = new Coro @_; 178 my $coro = new Coro @_;
147 $manager->ready; # this ensures that the stack is cloned from the manager
148 $pid->ready; 179 $coro->ready;
149 $pid; 180 $coro
181}
182
183=item async_pool { ... } [@args...]
184
185Similar to C<async>, but uses a coroutine pool, so you should not call
186terminate or join (although you are allowed to), and you get a coroutine
187that might have executed other code already (which can be good or bad :).
188
189Also, the block is executed in an C<eval> context and a warning will be
190issued in case of an exception instead of terminating the program, as
191C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
192will not work in the expected way, unless you call terminate or cancel,
193which somehow defeats the purpose of pooling.
194
195The priority will be reset to C<0> after each job, tracing will be
196disabled, the description will be reset and the default output filehandle
197gets restored, so you can change alkl these. Otherwise the coroutine will
198be re-used "as-is": most notably if you change other per-coroutine global
199stuff such as C<$/> you need to revert that change, which is most simply
200done by using local as in C< local $/ >.
201
202The pool size is limited to 8 idle coroutines (this can be adjusted by
203changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
204required.
205
206If you are concerned about pooled coroutines growing a lot because a
207single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
208{ terminate }> once per second or so to slowly replenish the pool. In
209addition to that, when the stacks used by a handler grows larger than 16kb
210(adjustable with $Coro::POOL_RSS) it will also exit.
211
212=cut
213
214our $POOL_SIZE = 8;
215our $POOL_RSS = 16 * 1024;
216our @async_pool;
217
218sub pool_handler {
219 my $cb;
220
221 while () {
222 eval {
223 while () {
224 _pool_1 $cb;
225 &$cb;
226 _pool_2 $cb;
227 &schedule;
228 }
229 };
230
231 last if $@ eq "\3async_pool terminate\2\n";
232 warn $@ if $@;
233 }
234}
235
236sub async_pool(&@) {
237 # this is also inlined into the unlock_scheduler
238 my $coro = (pop @async_pool) || new Coro \&pool_handler;
239
240 $coro->{_invoke} = [@_];
241 $coro->ready;
242
243 $coro
150} 244}
151 245
152=item schedule 246=item schedule
153 247
154Calls the scheduler. Please note that the current process will not be put 248Calls the scheduler. Please note that the current coroutine will not be put
155into the ready queue, so calling this function usually means you will 249into the ready queue, so calling this function usually means you will
156never be called again. 250never be called again unless something else (e.g. an event handler) calls
251ready.
157 252
158=cut 253The canonical way to wait on external events is this:
159 254
160my $prev; 255 {
256 # remember current coroutine
257 my $current = $Coro::current;
161 258
162sub schedule { 259 # register a hypothetical event handler
163 # should be done using priorities :( 260 on_event_invoke sub {
164 ($prev, $current) = ($current, shift @ready || $idle); 261 # wake up sleeping coroutine
165 Coro::State::transfer($prev, $current); 262 $current->ready;
166} 263 undef $current;
264 };
265
266 # call schedule until event occurred.
267 # in case we are woken up for other reasons
268 # (current still defined), loop.
269 Coro::schedule while $current;
270 }
167 271
168=item cede 272=item cede
169 273
170"Cede" to other processes. This function puts the current process into the 274"Cede" to other coroutines. This function puts the current coroutine into the
171ready queue and calls C<schedule>, which has the effect of giving up the 275ready queue and calls C<schedule>, which has the effect of giving up the
172current "timeslice" to other coroutines of the same or higher priority. 276current "timeslice" to other coroutines of the same or higher priority.
173 277
174=cut 278=item Coro::cede_notself
175 279
176sub cede { 280Works like cede, but is not exported by default and will cede to any
177 $current->ready; 281coroutine, regardless of priority, once.
178 &schedule;
179}
180 282
181=item terminate 283=item terminate [arg...]
182 284
183Terminates the current process. 285Terminates the current coroutine with the given status values (see L<cancel>).
184 286
185Future versions of this function will allow result arguments. 287=item killall
288
289Kills/terminates/cancels all coroutines except the currently running
290one. This is useful after a fork, either in the child or the parent, as
291usually only one of them should inherit the running coroutines.
186 292
187=cut 293=cut
188 294
189sub terminate { 295sub terminate {
190 push @destroy, $current; 296 $current->cancel (@_);
191 $manager->ready; 297}
192 &schedule; 298
193 # NORETURN 299sub killall {
300 for (Coro::State::list) {
301 $_->cancel
302 if $_ != $current && UNIVERSAL::isa $_, "Coro";
303 }
194} 304}
195 305
196=back 306=back
197 307
198# dynamic methods
199
200=head2 PROCESS METHODS 308=head2 COROUTINE METHODS
201 309
202These are the methods you can call on process objects. 310These are the methods you can call on coroutine objects.
203 311
204=over 4 312=over 4
205 313
206=item new Coro \&sub [, @args...] 314=item new Coro \&sub [, @args...]
207 315
208Create a new process and return it. When the sub returns the process 316Create a new coroutine and return it. When the sub returns the coroutine
209automatically terminates. To start the process you must first put it into 317automatically terminates as if C<terminate> with the returned values were
318called. To make the coroutine run you must first put it into the ready queue
210the ready queue by calling the ready method. 319by calling the ready method.
211 320
212The coderef you submit MUST NOT be a closure that refers to variables 321See C<async> and C<Coro::State::new> for additional info about the
213in an outer scope. This does NOT work. Pass arguments into it instead. 322coroutine environment.
214 323
215=cut 324=cut
216 325
217sub _newcoro { 326sub _run_coro {
218 terminate &{+shift}; 327 terminate &{+shift};
219} 328}
220 329
221sub new { 330sub new {
222 my $class = shift; 331 my $class = shift;
223 bless {
224 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
225 }, $class;
226}
227 332
228=item $process->ready 333 $class->SUPER::new (\&_run_coro, @_)
334}
229 335
230Put the current process into the ready queue. 336=item $success = $coroutine->ready
231 337
232=cut 338Put the given coroutine into the ready queue (according to it's priority)
339and return true. If the coroutine is already in the ready queue, do nothing
340and return false.
233 341
234sub ready { 342=item $is_ready = $coroutine->is_ready
235 push @ready, $_[0]; 343
344Return wether the coroutine is currently the ready queue or not,
345
346=item $coroutine->cancel (arg...)
347
348Terminates the given coroutine and makes it return the given arguments as
349status (default: the empty list). Never returns if the coroutine is the
350current coroutine.
351
352=cut
353
354sub cancel {
355 my $self = shift;
356 $self->{_status} = [@_];
357
358 if ($current == $self) {
359 push @destroy, $self;
360 $manager->ready;
361 &schedule while 1;
362 } else {
363 $self->_cancel;
364 }
365}
366
367=item $coroutine->join
368
369Wait until the coroutine terminates and return any values given to the
370C<terminate> or C<cancel> functions. C<join> can be called concurrently
371from multiple coroutines.
372
373=cut
374
375sub join {
376 my $self = shift;
377
378 unless ($self->{_status}) {
379 my $current = $current;
380
381 push @{$self->{_on_destroy}}, sub {
382 $current->ready;
383 undef $current;
384 };
385
386 &schedule while $current;
387 }
388
389 wantarray ? @{$self->{_status}} : $self->{_status}[0];
390}
391
392=item $coroutine->on_destroy (\&cb)
393
394Registers a callback that is called when this coroutine gets destroyed,
395but before it is joined. The callback gets passed the terminate arguments,
396if any.
397
398=cut
399
400sub on_destroy {
401 my ($self, $cb) = @_;
402
403 push @{ $self->{_on_destroy} }, $cb;
404}
405
406=item $oldprio = $coroutine->prio ($newprio)
407
408Sets (or gets, if the argument is missing) the priority of the
409coroutine. Higher priority coroutines get run before lower priority
410coroutines. Priorities are small signed integers (currently -4 .. +3),
411that you can refer to using PRIO_xxx constants (use the import tag :prio
412to get then):
413
414 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
415 3 > 1 > 0 > -1 > -3 > -4
416
417 # set priority to HIGH
418 current->prio(PRIO_HIGH);
419
420The idle coroutine ($Coro::idle) always has a lower priority than any
421existing coroutine.
422
423Changing the priority of the current coroutine will take effect immediately,
424but changing the priority of coroutines in the ready queue (but not
425running) will only take effect after the next schedule (of that
426coroutine). This is a bug that will be fixed in some future version.
427
428=item $newprio = $coroutine->nice ($change)
429
430Similar to C<prio>, but subtract the given value from the priority (i.e.
431higher values mean lower priority, just as in unix).
432
433=item $olddesc = $coroutine->desc ($newdesc)
434
435Sets (or gets in case the argument is missing) the description for this
436coroutine. This is just a free-form string you can associate with a coroutine.
437
438This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
439can modify this member directly if you wish.
440
441=item $coroutine->throw ([$scalar])
442
443If C<$throw> is specified and defined, it will be thrown as an exception
444inside the coroutine at the next convinient point in time (usually after
445it gains control at the next schedule/transfer/cede). Otherwise clears the
446exception object.
447
448The exception object will be thrown "as is" with the specified scalar in
449C<$@>, i.e. if it is a string, no line number or newline will be appended
450(unlike with C<die>).
451
452This can be used as a softer means than C<cancel> to ask a coroutine to
453end itself, although there is no guarentee that the exception will lead to
454termination, and if the exception isn't caught it might well end the whole
455program.
456
457=cut
458
459sub desc {
460 my $old = $_[0]{desc};
461 $_[0]{desc} = $_[1] if @_ > 1;
462 $old;
236} 463}
237 464
238=back 465=back
239 466
467=head2 GLOBAL FUNCTIONS
468
469=over 4
470
471=item Coro::nready
472
473Returns the number of coroutines that are currently in the ready state,
474i.e. that can be switched to. The value C<0> means that the only runnable
475coroutine is the currently running one, so C<cede> would have no effect,
476and C<schedule> would cause a deadlock unless there is an idle handler
477that wakes up some coroutines.
478
479=item my $guard = Coro::guard { ... }
480
481This creates and returns a guard object. Nothing happens until the object
482gets destroyed, in which case the codeblock given as argument will be
483executed. This is useful to free locks or other resources in case of a
484runtime error or when the coroutine gets canceled, as in both cases the
485guard block will be executed. The guard object supports only one method,
486C<< ->cancel >>, which will keep the codeblock from being executed.
487
488Example: set some flag and clear it again when the coroutine gets canceled
489or the function returns:
490
491 sub do_something {
492 my $guard = Coro::guard { $busy = 0 };
493 $busy = 1;
494
495 # do something that requires $busy to be true
496 }
497
498=cut
499
500sub guard(&) {
501 bless \(my $cb = $_[0]), "Coro::guard"
502}
503
504sub Coro::guard::cancel {
505 ${$_[0]} = sub { };
506}
507
508sub Coro::guard::DESTROY {
509 ${$_[0]}->();
510}
511
512
513=item unblock_sub { ... }
514
515This utility function takes a BLOCK or code reference and "unblocks" it,
516returning the new coderef. This means that the new coderef will return
517immediately without blocking, returning nothing, while the original code
518ref will be called (with parameters) from within its own coroutine.
519
520The reason this function exists is that many event libraries (such as the
521venerable L<Event|Event> module) are not coroutine-safe (a weaker form
522of thread-safety). This means you must not block within event callbacks,
523otherwise you might suffer from crashes or worse.
524
525This function allows your callbacks to block by executing them in another
526coroutine where it is safe to block. One example where blocking is handy
527is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
528disk.
529
530In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
531creating event callbacks that want to block.
532
533=cut
534
535our @unblock_queue;
536
537# we create a special coro because we want to cede,
538# to reduce pressure on the coro pool (because most callbacks
539# return immediately and can be reused) and because we cannot cede
540# inside an event callback.
541our $unblock_scheduler = new Coro sub {
542 while () {
543 while (my $cb = pop @unblock_queue) {
544 # this is an inlined copy of async_pool
545 my $coro = (pop @async_pool) || new Coro \&pool_handler;
546
547 $coro->{_invoke} = $cb;
548 $coro->ready;
549 cede; # for short-lived callbacks, this reduces pressure on the coro pool
550 }
551 schedule; # sleep well
552 }
553};
554$unblock_scheduler->desc ("[unblock_sub scheduler]");
555
556sub unblock_sub(&) {
557 my $cb = shift;
558
559 sub {
560 unshift @unblock_queue, [$cb, @_];
561 $unblock_scheduler->ready;
562 }
563}
564
565=back
566
240=cut 567=cut
241 568
2421; 5691;
243 570
244=head1 BUGS/LIMITATIONS 571=head1 BUGS/LIMITATIONS
245 572
246 - could be faster, especially when the core would introduce special 573 - you must make very sure that no coro is still active on global
247 support for coroutines (like it does for threads). 574 destruction. very bad things might happen otherwise (usually segfaults).
248 - there is still a memleak on coroutine termination that I could not 575
249 identify. Could be as small as a single SV.
250 - this module is not well-tested.
251 - if variables or arguments "disappear" (become undef) or become
252 corrupted please contact the author so he cen iron out the
253 remaining bugs.
254 - this module is not thread-safe. You must only ever use this module from 576 - this module is not thread-safe. You should only ever use this module
255 the same thread (this requirement might be loosened in the future to 577 from the same thread (this requirement might be loosened in the future
256 allow per-thread schedulers, but Coro::State does not yet allow this). 578 to allow per-thread schedulers, but Coro::State does not yet allow
579 this).
257 580
258=head1 SEE ALSO 581=head1 SEE ALSO
259 582
260L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 583Lower level Configuration, Coroutine Environment: L<Coro::State>.
261L<Coro::Signal>, L<Coro::State>, L<Coro::Event>. 584
585Debugging: L<Coro::Debug>.
586
587Support/Utility: L<Coro::Specific>, L<Coro::Util>.
588
589Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
590
591Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>.
592
593Compatibility: L<Coro::LWP>, L<Coro::Storable>, L<Coro::Select>.
594
595Embedding: L<Coro::MakeMaker>.
262 596
263=head1 AUTHOR 597=head1 AUTHOR
264 598
265 Marc Lehmann <pcg@goof.com> 599 Marc Lehmann <schmorp@schmorp.de>
266 http://www.goof.com/pcg/marc/ 600 http://home.schmorp.de/
267 601
268=cut 602=cut
269 603

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