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Revision 1.30 by root, Sat Aug 11 19:59:19 2001 UTC vs.
Revision 1.101 by root, Fri Dec 29 08:36:34 2006 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 use din this module also
26guarentees 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
26This module is still experimental, see the BUGS section below. 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).
27 34
28In this module, coroutines are defined as "callchain + lexical variables 35In this module, coroutines are defined as "callchain + lexical variables +
29+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own 36@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
30callchain, it's own set of lexicals and it's own set of perl's most 37its own set of lexicals and its own set of perls most important global
31important global variables. 38variables.
32 39
33=cut 40=cut
34 41
35package Coro; 42package Coro;
36 43
44use strict;
45no warnings "uninitialized";
46
37use Coro::State; 47use Coro::State;
38 48
39use base Exporter; 49use base qw(Coro::State Exporter);
40 50
41$VERSION = 0.45; 51our $idle; # idle handler
52our $main; # main coroutine
53our $current; # current coroutine
42 54
55our $VERSION = '3.3';
56
43@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async cede schedule terminate current unblock_sub);
44@EXPORT_OK = qw($current); 58our %EXPORT_TAGS = (
59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
60);
61our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
45 62
46{ 63{
47 my @async; 64 my @async;
48 my $init; 65 my $init;
49 66
50 # this way of handling attributes simply is NOT scalable ;() 67 # this way of handling attributes simply is NOT scalable ;()
51 sub import { 68 sub import {
69 no strict 'refs';
70
52 Coro->export_to_level(1, @_); 71 Coro->export_to_level (1, @_);
72
53 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; 73 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
54 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { 74 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
55 my ($package, $ref) = (shift, shift); 75 my ($package, $ref) = (shift, shift);
56 my @attrs; 76 my @attrs;
57 for (@_) { 77 for (@_) {
72 }; 92 };
73 } 93 }
74 94
75} 95}
76 96
97=over 4
98
77=item $main 99=item $main
78 100
79This coroutine represents the main program. 101This coroutine represents the main program.
80 102
81=cut 103=cut
82 104
83our $main = new Coro; 105$main = new Coro;
84 106
85=item $current (or as function: current) 107=item $current (or as function: current)
86 108
87The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). 109The current coroutine (the last coroutine switched to). The initial value
110is C<$main> (of course).
111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essentiel you are encouraged to use the
114C<Coro::current> function instead.
88 115
89=cut 116=cut
90 117
91# maybe some other module used Coro::Specific before... 118# maybe some other module used Coro::Specific before...
92if ($current) {
93 $main->{specific} = $current->{specific}; 119$main->{specific} = $current->{specific}
94} 120 if $current;
95 121
96our $current = $main; 122_set_current $main;
97 123
98sub current() { $current } 124sub current() { $current }
99 125
100=item $idle 126=item $idle
101 127
102The coroutine to switch to when no other coroutine is running. The default 128A callback that is called whenever the scheduler finds no ready coroutines
103implementation 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.
104 131
105=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.
106 135
107# should be done using priorities :( 136Please note that if your callback recursively invokes perl (e.g. for event
108our $idle = new Coro sub { 137handlers), then it must be prepared to be called recursively.
109 print STDERR "FATAL: deadlock detected\n"; 138
110 exit(51); 139=cut
140
141$idle = sub {
142 require Carp;
143 Carp::croak ("FATAL: deadlock detected");
111}; 144};
112 145
113# this coroutine is necessary because a coroutine 146# this coroutine is necessary because a coroutine
114# cannot destroy itself. 147# cannot destroy itself.
115my @destroy; 148my @destroy;
116my $manager = new Coro sub { 149my $manager; $manager = new Coro sub {
117 while() { 150 while () {
118 delete ((pop @destroy)->{_coro_state}) while @destroy; 151 # by overwriting the state object with the manager we destroy it
152 # while still being able to schedule this coroutine (in case it has
153 # been readied multiple times. this is harmless since the manager
154 # can be called as many times as neccessary and will always
155 # remove itself from the runqueue
156 while (@destroy) {
157 my $coro = pop @destroy;
158
159 $coro->{status} ||= [];
160
161 $_->ready for @{(delete $coro->{join} ) || []};
162 $_->(@{$coro->{status}}) for @{(delete $coro->{destroy_cb}) || []};
163
164 # the next line destroys the coro state, but keeps the
165 # coroutine itself intact (we basically make it a zombie
166 # coroutine that always runs the manager thread, so it's possible
167 # to transfer() to this coroutine).
168 $coro->_clone_state_from ($manager);
169 }
119 &schedule; 170 &schedule;
120 } 171 }
121}; 172};
122 173
123# static methods. not really. 174# static methods. not really.
124 175
176=back
177
125=head2 STATIC METHODS 178=head2 STATIC METHODS
126 179
127Static methods are actually functions that operate on the current process only. 180Static methods are actually functions that operate on the current coroutine only.
128 181
129=over 4 182=over 4
130 183
131=item async { ... } [@args...] 184=item async { ... } [@args...]
132 185
133Create a new asynchronous process and return it's process object 186Create a new asynchronous coroutine and return it's coroutine object
134(usually unused). When the sub returns the new process is automatically 187(usually unused). When the sub returns the new coroutine is automatically
135terminated. 188terminated.
189
190Calling C<exit> in a coroutine will not work correctly, so do not do that.
191
192When the coroutine dies, the program will exit, just as in the main
193program.
136 194
137 # create a new coroutine that just prints its arguments 195 # create a new coroutine that just prints its arguments
138 async { 196 async {
139 print "@_\n"; 197 print "@_\n";
140 } 1,2,3,4; 198 } 1,2,3,4;
141 199
142The coderef you submit MUST NOT be a closure that refers to variables
143in an outer scope. This does NOT work. Pass arguments into it instead.
144
145=cut 200=cut
146 201
147sub async(&@) { 202sub async(&@) {
148 my $pid = new Coro @_; 203 my $pid = new Coro @_;
149 $manager->ready; # this ensures that the stack is cloned from the manager
150 $pid->ready; 204 $pid->ready;
151 $pid; 205 $pid
152} 206}
153 207
154=item schedule 208=item schedule
155 209
156Calls the scheduler. Please note that the current process will not be put 210Calls the scheduler. Please note that the current coroutine will not be put
157into the ready queue, so calling this function usually means you will 211into the ready queue, so calling this function usually means you will
158never be called again. 212never be called again unless something else (e.g. an event handler) calls
213ready.
159 214
160=cut 215The canonical way to wait on external events is this:
216
217 {
218 # remember current coroutine
219 my $current = $Coro::current;
220
221 # register a hypothetical event handler
222 on_event_invoke sub {
223 # wake up sleeping coroutine
224 $current->ready;
225 undef $current;
226 };
227
228 # call schedule until event occured.
229 # in case we are woken up for other reasons
230 # (current still defined), loop.
231 Coro::schedule while $current;
232 }
161 233
162=item cede 234=item cede
163 235
164"Cede" to other processes. This function puts the current process into the 236"Cede" to other coroutines. This function puts the current coroutine into the
165ready queue and calls C<schedule>, which has the effect of giving up the 237ready queue and calls C<schedule>, which has the effect of giving up the
166current "timeslice" to other coroutines of the same or higher priority. 238current "timeslice" to other coroutines of the same or higher priority.
167 239
168=cut
169
170=item terminate 240=item terminate [arg...]
171 241
172Terminates the current process. 242Terminates the current coroutine with the given status values (see L<cancel>).
173
174Future versions of this function will allow result arguments.
175 243
176=cut 244=cut
177 245
178sub terminate { 246sub terminate {
179 $current->cancel; 247 $current->cancel (@_);
180 &schedule;
181 die; # NORETURN
182} 248}
183 249
184=back 250=back
185 251
186# dynamic methods 252# dynamic methods
187 253
188=head2 PROCESS METHODS 254=head2 COROUTINE METHODS
189 255
190These are the methods you can call on process objects. 256These are the methods you can call on coroutine objects.
191 257
192=over 4 258=over 4
193 259
194=item new Coro \&sub [, @args...] 260=item new Coro \&sub [, @args...]
195 261
196Create a new process and return it. When the sub returns the process 262Create a new coroutine and return it. When the sub returns the coroutine
197automatically terminates. To start the process you must first put it into 263automatically terminates as if C<terminate> with the returned values were
264called. To make the coroutine run you must first put it into the ready queue
198the ready queue by calling the ready method. 265by calling the ready method.
199 266
200The coderef you submit MUST NOT be a closure that refers to variables 267Calling C<exit> in a coroutine will not work correctly, so do not do that.
201in an outer scope. This does NOT work. Pass arguments into it instead.
202 268
203=cut 269=cut
204 270
205sub _newcoro { 271sub _run_coro {
206 terminate &{+shift}; 272 terminate &{+shift};
207} 273}
208 274
209sub new { 275sub new {
210 my $class = shift; 276 my $class = shift;
211 bless {
212 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
213 }, $class;
214}
215 277
216=item $process->ready 278 $class->SUPER::new (\&_run_coro, @_)
279}
217 280
218Put the current process into the ready queue. 281=item $success = $coroutine->ready
219 282
220=cut 283Put the given coroutine into the ready queue (according to it's priority)
284and return true. If the coroutine is already in the ready queue, do nothing
285and return false.
221 286
222=item $process->cancel 287=item $is_ready = $coroutine->is_ready
223 288
224Like C<terminate>, but terminates the specified process instead. 289Return wether the coroutine is currently the ready queue or not,
290
291=item $coroutine->cancel (arg...)
292
293Terminates the given coroutine and makes it return the given arguments as
294status (default: the empty list).
225 295
226=cut 296=cut
227 297
228sub cancel { 298sub cancel {
299 my $self = shift;
300 $self->{status} = [@_];
229 push @destroy, $_[0]; 301 push @destroy, $self;
230 $manager->ready; 302 $manager->ready;
303 &schedule if $current == $self;
304}
305
306=item $coroutine->join
307
308Wait until the coroutine terminates and return any values given to the
309C<terminate> or C<cancel> functions. C<join> can be called multiple times
310from multiple coroutine.
311
312=cut
313
314sub join {
315 my $self = shift;
316 unless ($self->{status}) {
317 push @{$self->{join}}, $current;
318 &schedule;
319 }
320 wantarray ? @{$self->{status}} : $self->{status}[0];
321}
322
323=item $coroutine->on_destroy (\&cb)
324
325Registers a callback that is called when this coroutine gets destroyed,
326but before it is joined. The callback gets passed the terminate arguments,
327if any.
328
329=cut
330
331sub on_destroy {
332 my ($self, $cb) = @_;
333
334 push @{ $self->{destroy_cb} }, $cb;
335}
336
337=item $oldprio = $coroutine->prio ($newprio)
338
339Sets (or gets, if the argument is missing) the priority of the
340coroutine. Higher priority coroutines get run before lower priority
341coroutines. Priorities are small signed integers (currently -4 .. +3),
342that you can refer to using PRIO_xxx constants (use the import tag :prio
343to get then):
344
345 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
346 3 > 1 > 0 > -1 > -3 > -4
347
348 # set priority to HIGH
349 current->prio(PRIO_HIGH);
350
351The idle coroutine ($Coro::idle) always has a lower priority than any
352existing coroutine.
353
354Changing the priority of the current coroutine will take effect immediately,
355but changing the priority of coroutines in the ready queue (but not
356running) will only take effect after the next schedule (of that
357coroutine). This is a bug that will be fixed in some future version.
358
359=item $newprio = $coroutine->nice ($change)
360
361Similar to C<prio>, but subtract the given value from the priority (i.e.
362higher values mean lower priority, just as in unix).
363
364=item $olddesc = $coroutine->desc ($newdesc)
365
366Sets (or gets in case the argument is missing) the description for this
367coroutine. This is just a free-form string you can associate with a coroutine.
368
369=cut
370
371sub desc {
372 my $old = $_[0]{desc};
373 $_[0]{desc} = $_[1] if @_ > 1;
374 $old;
231} 375}
232 376
233=back 377=back
234 378
379=head2 GLOBAL FUNCTIONS
380
381=over 4
382
383=item Coro::nready
384
385Returns the number of coroutines that are currently in the ready state,
386i.e. that can be swicthed to. The value C<0> means that the only runnable
387coroutine is the currently running one, so C<cede> would have no effect,
388and C<schedule> would cause a deadlock unless there is an idle handler
389that wakes up some coroutines.
390
391=item unblock_sub { ... }
392
393This utility function takes a BLOCK or code reference and "unblocks" it,
394returning the new coderef. This means that the new coderef will return
395immediately without blocking, returning nothing, while the original code
396ref will be called (with parameters) from within its own coroutine.
397
398The reason this fucntion exists is that many event libraries (such as the
399venerable L<Event|Event> module) are not coroutine-safe (a weaker form
400of thread-safety). This means you must not block within event callbacks,
401otherwise you might suffer from crashes or worse.
402
403This function allows your callbacks to block by executing them in another
404coroutine where it is safe to block. One example where blocking is handy
405is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
406disk.
407
408In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
409creating event callbacks that want to block.
410
411=cut
412
413our @unblock_pool;
414our @unblock_queue;
415our $UNBLOCK_POOL_SIZE = 2;
416
417sub unblock_handler_ {
418 while () {
419 my ($cb, @arg) = @{ delete $Coro::current->{arg} };
420 $cb->(@arg);
421
422 last if @unblock_pool >= $UNBLOCK_POOL_SIZE;
423 push @unblock_pool, $Coro::current;
424 schedule;
425 }
426}
427
428our $unblock_scheduler = async {
429 while () {
430 while (my $cb = pop @unblock_queue) {
431 my $handler = (pop @unblock_pool or new Coro \&unblock_handler_);
432 $handler->{arg} = $cb;
433 $handler->ready;
434 cede;
435 }
436
437 schedule;
438 }
439};
440
441sub unblock_sub(&) {
442 my $cb = shift;
443
444 sub {
445 push @unblock_queue, [$cb, @_];
446 $unblock_scheduler->ready;
447 }
448}
449
450=back
451
235=cut 452=cut
236 453
2371; 4541;
238 455
239=head1 BUGS/LIMITATIONS 456=head1 BUGS/LIMITATIONS
240 457
241 - could be faster, especially when the core would introduce special 458 - you must make very sure that no coro is still active on global
242 support for coroutines (like it does for threads). 459 destruction. very bad things might happen otherwise (usually segfaults).
243 - there is still a memleak on coroutine termination that I could not 460
244 identify. Could be as small as a single SV.
245 - this module is not well-tested.
246 - if variables or arguments "disappear" (become undef) or become
247 corrupted please contact the author so he cen iron out the
248 remaining bugs.
249 - this module is not thread-safe. You must only ever use this module from 461 - this module is not thread-safe. You should only ever use this module
250 the same thread (this requirement might be loosened in the future to 462 from the same thread (this requirement might be losened in the future
251 allow per-thread schedulers, but Coro::State does not yet allow this). 463 to allow per-thread schedulers, but Coro::State does not yet allow
464 this).
252 465
253=head1 SEE ALSO 466=head1 SEE ALSO
254 467
255L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 468Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
256L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>, 469
257L<Coro::Handle>, L<Coro::Socket>. 470Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
471
472Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
473
474Embedding: L<Coro:MakeMaker>
258 475
259=head1 AUTHOR 476=head1 AUTHOR
260 477
261 Marc Lehmann <pcg@goof.com> 478 Marc Lehmann <schmorp@schmorp.de>
262 http://www.goof.com/pcg/marc/ 479 http://home.schmorp.de/
263 480
264=cut 481=cut
265 482

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