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Revision 1.36 by root, Mon Sep 24 01:36:20 2001 UTC vs.
Revision 1.98 by root, Mon Dec 4 21:56:00 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@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
30callchain, it's own set of lexicals and it's own set of perl's most 37its own set of lexicals and its own set of perls most important global
31important global variables. 38variables.
32 39
33=cut 40=cut
34 41
35package Coro; 42package Coro;
36 43
44use strict;
37no warnings qw(uninitialized); 45no warnings "uninitialized";
38 46
39use Coro::State; 47use Coro::State;
40 48
41use base Exporter; 49use base qw(Coro::State Exporter);
42 50
43$VERSION = 0.5; 51our $idle; # idle handler
52our $main; # main coroutine
53our $current; # current coroutine
44 54
55our $VERSION = '3.1';
56
45@EXPORT = qw(async cede schedule terminate current); 57our @EXPORT = qw(async cede schedule terminate current unblock_sub);
46%EXPORT_TAGS = ( 58our %EXPORT_TAGS = (
47 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48); 60);
49@EXPORT_OK = @{$EXPORT_TAGS{prio}}; 61our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
50 62
51{ 63{
52 my @async; 64 my @async;
53 my $init; 65 my $init;
54 66
55 # this way of handling attributes simply is NOT scalable ;() 67 # this way of handling attributes simply is NOT scalable ;()
56 sub import { 68 sub import {
69 no strict 'refs';
70
57 Coro->export_to_level(1, @_); 71 Coro->export_to_level (1, @_);
72
58 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; 73 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
59 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { 74 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
60 my ($package, $ref) = (shift, shift); 75 my ($package, $ref) = (shift, shift);
61 my @attrs; 76 my @attrs;
62 for (@_) { 77 for (@_) {
77 }; 92 };
78 } 93 }
79 94
80} 95}
81 96
97=over 4
98
82=item $main 99=item $main
83 100
84This coroutine represents the main program. 101This coroutine represents the main program.
85 102
86=cut 103=cut
87 104
88our $main = new Coro; 105$main = new Coro;
89 106
90=item $current (or as function: current) 107=item $current (or as function: current)
91 108
92The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). 109The current coroutine (the last coroutine switched to). The initial value
110is C<$main> (of course).
111
112This variable is B<strictly> I<read-only>. It is provided for performance
113reasons. If performance is not essentiel you are encouraged to use the
114C<Coro::current> function instead.
93 115
94=cut 116=cut
95 117
96# maybe some other module used Coro::Specific before... 118# maybe some other module used Coro::Specific before...
97if ($current) {
98 $main->{specific} = $current->{specific}; 119$main->{specific} = $current->{specific}
99} 120 if $current;
100 121
101our $current = $main; 122_set_current $main;
102 123
103sub current() { $current } 124sub current() { $current }
104 125
105=item $idle 126=item $idle
106 127
107The coroutine to switch to when no other coroutine is running. The default 128A callback that is called whenever the scheduler finds no ready coroutines
108implementation 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.
109 131
110=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.
111 135
112# should be done using priorities :( 136Please note that if your callback recursively invokes perl (e.g. for event
113our $idle = new Coro sub { 137handlers), then it must be prepared to be called recursively.
114 print STDERR "FATAL: deadlock detected\n"; 138
115 exit(51); 139=cut
140
141$idle = sub {
142 require Carp;
143 Carp::croak ("FATAL: deadlock detected");
116}; 144};
117 145
118# this coroutine is necessary because a coroutine 146# this coroutine is necessary because a coroutine
119# cannot destroy itself. 147# cannot destroy itself.
120my @destroy; 148my @destroy;
121my $manager = new Coro sub { 149my $manager; $manager = new Coro sub {
122 while() { 150 while () {
123 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 $coro->{status} ||= [];
159 $_->ready for @{delete $coro->{join} || []};
160
161 # the next line destroys the coro state, but keeps the
162 # coroutine itself intact (we basically make it a zombie
163 # coroutine that always runs the manager thread, so it's possible
164 # to transfer() to this coroutine).
165 $coro->_clone_state_from ($manager);
166 }
124 &schedule; 167 &schedule;
125 } 168 }
126}; 169};
127 170
128# static methods. not really. 171# static methods. not really.
129 172
173=back
174
130=head2 STATIC METHODS 175=head2 STATIC METHODS
131 176
132Static methods are actually functions that operate on the current process only. 177Static methods are actually functions that operate on the current coroutine only.
133 178
134=over 4 179=over 4
135 180
136=item async { ... } [@args...] 181=item async { ... } [@args...]
137 182
138Create a new asynchronous process and return it's process object 183Create a new asynchronous coroutine and return it's coroutine object
139(usually unused). When the sub returns the new process is automatically 184(usually unused). When the sub returns the new coroutine is automatically
140terminated. 185terminated.
186
187Calling C<exit> in a coroutine will not work correctly, so do not do that.
188
189When the coroutine dies, the program will exit, just as in the main
190program.
141 191
142 # create a new coroutine that just prints its arguments 192 # create a new coroutine that just prints its arguments
143 async { 193 async {
144 print "@_\n"; 194 print "@_\n";
145 } 1,2,3,4; 195 } 1,2,3,4;
146 196
147The coderef you submit MUST NOT be a closure that refers to variables
148in an outer scope. This does NOT work. Pass arguments into it instead.
149
150=cut 197=cut
151 198
152sub async(&@) { 199sub async(&@) {
153 my $pid = new Coro @_; 200 my $pid = new Coro @_;
154 $manager->ready; # this ensures that the stack is cloned from the manager
155 $pid->ready; 201 $pid->ready;
156 $pid; 202 $pid
157} 203}
158 204
159=item schedule 205=item schedule
160 206
161Calls the scheduler. Please note that the current process will not be put 207Calls the scheduler. Please note that the current coroutine will not be put
162into the ready queue, so calling this function usually means you will 208into the ready queue, so calling this function usually means you will
163never be called again. 209never be called again unless something else (e.g. an event handler) calls
210ready.
164 211
165=cut 212The canonical way to wait on external events is this:
213
214 {
215 # remember current coroutine
216 my $current = $Coro::current;
217
218 # register a hypothetical event handler
219 on_event_invoke sub {
220 # wake up sleeping coroutine
221 $current->ready;
222 undef $current;
223 };
224
225 # call schedule until event occured.
226 # in case we are woken up for other reasons
227 # (current still defined), loop.
228 Coro::schedule while $current;
229 }
166 230
167=item cede 231=item cede
168 232
169"Cede" to other processes. This function puts the current process into the 233"Cede" to other coroutines. This function puts the current coroutine into the
170ready queue and calls C<schedule>, which has the effect of giving up the 234ready queue and calls C<schedule>, which has the effect of giving up the
171current "timeslice" to other coroutines of the same or higher priority. 235current "timeslice" to other coroutines of the same or higher priority.
172 236
173=cut
174
175=item terminate 237=item terminate [arg...]
176 238
177Terminates the current process. 239Terminates the current coroutine with the given status values (see L<cancel>).
178
179Future versions of this function will allow result arguments.
180 240
181=cut 241=cut
182 242
183sub terminate { 243sub terminate {
184 $current->cancel; 244 $current->cancel (@_);
185 &schedule;
186 die; # NORETURN
187} 245}
188 246
189=back 247=back
190 248
191# dynamic methods 249# dynamic methods
192 250
193=head2 PROCESS METHODS 251=head2 COROUTINE METHODS
194 252
195These are the methods you can call on process objects. 253These are the methods you can call on coroutine objects.
196 254
197=over 4 255=over 4
198 256
199=item new Coro \&sub [, @args...] 257=item new Coro \&sub [, @args...]
200 258
201Create a new process and return it. When the sub returns the process 259Create a new coroutine and return it. When the sub returns the coroutine
202automatically terminates. To start the process you must first put it into 260automatically terminates as if C<terminate> with the returned values were
261called. To make the coroutine run you must first put it into the ready queue
203the ready queue by calling the ready method. 262by calling the ready method.
204 263
205The coderef you submit MUST NOT be a closure that refers to variables 264Calling C<exit> in a coroutine will not work correctly, so do not do that.
206in an outer scope. This does NOT work. Pass arguments into it instead.
207 265
208=cut 266=cut
209 267
210sub _newcoro { 268sub _run_coro {
211 terminate &{+shift}; 269 terminate &{+shift};
212} 270}
213 271
214sub new { 272sub new {
215 my $class = shift; 273 my $class = shift;
216 bless {
217 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
218 }, $class;
219}
220 274
221=item $process->ready 275 $class->SUPER::new (\&_run_coro, @_)
276}
222 277
223Put the current process into the ready queue. 278=item $success = $coroutine->ready
224 279
225=cut 280Put the given coroutine into the ready queue (according to it's priority)
281and return true. If the coroutine is already in the ready queue, do nothing
282and return false.
226 283
227=item $process->cancel 284=item $is_ready = $coroutine->is_ready
228 285
229Like C<terminate>, but terminates the specified process instead. 286Return wether the coroutine is currently the ready queue or not,
287
288=item $coroutine->cancel (arg...)
289
290Terminates the given coroutine and makes it return the given arguments as
291status (default: the empty list).
230 292
231=cut 293=cut
232 294
233sub cancel { 295sub cancel {
296 my $self = shift;
297 $self->{status} = [@_];
234 push @destroy, $_[0]; 298 push @destroy, $self;
235 $manager->ready; 299 $manager->ready;
236 &schedule if $current == $_[0]; 300 &schedule if $current == $self;
237} 301}
238 302
303=item $coroutine->join
304
305Wait until the coroutine terminates and return any values given to the
306C<terminate> or C<cancel> functions. C<join> can be called multiple times
307from multiple coroutine.
308
309=cut
310
311sub join {
312 my $self = shift;
313 unless ($self->{status}) {
314 push @{$self->{join}}, $current;
315 &schedule;
316 }
317 wantarray ? @{$self->{status}} : $self->{status}[0];
318}
319
239=item $oldprio = $process->prio($newprio) 320=item $oldprio = $coroutine->prio ($newprio)
240 321
241Sets the priority of the process. Higher priority processes get run before 322Sets (or gets, if the argument is missing) the priority of the
242lower priority processes. Priorities are smalled signed integer (currently 323coroutine. Higher priority coroutines get run before lower priority
324coroutines. Priorities are small signed integers (currently -4 .. +3),
243-4 .. +3), that you can refer to using PRIO_xxx constants (use the import 325that you can refer to using PRIO_xxx constants (use the import tag :prio
244tag :prio to get then): 326to get then):
245 327
246 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 328 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
247 3 > 1 > 0 > -1 > -3 > -4 329 3 > 1 > 0 > -1 > -3 > -4
248 330
249 # set priority to HIGH 331 # set priority to HIGH
250 current->prio(PRIO_HIGH); 332 current->prio(PRIO_HIGH);
251 333
252The idle coroutine ($Coro::idle) always has a lower priority than any 334The idle coroutine ($Coro::idle) always has a lower priority than any
253existing coroutine. 335existing coroutine.
254 336
255Changing the priority of the current process will take effect immediately, 337Changing the priority of the current coroutine will take effect immediately,
256but changing the priority of processes in the ready queue (but not 338but changing the priority of coroutines in the ready queue (but not
257running) will only take effect after the next schedule (of that 339running) will only take effect after the next schedule (of that
258process). This is a bug that will be fixed in some future version. 340coroutine). This is a bug that will be fixed in some future version.
259 341
260=cut
261
262sub prio {
263 my $old = $_[0]{prio};
264 $_[0]{prio} = $_[1] if @_ > 1;
265 $old;
266}
267
268=item $newprio = $process->nice($change) 342=item $newprio = $coroutine->nice ($change)
269 343
270Similar to C<prio>, but subtract the given value from the priority (i.e. 344Similar to C<prio>, but subtract the given value from the priority (i.e.
271higher values mean lower priority, just as in unix). 345higher values mean lower priority, just as in unix).
272 346
273=cut 347=item $olddesc = $coroutine->desc ($newdesc)
274 348
275sub nice { 349Sets (or gets in case the argument is missing) the description for this
276 $_[0]{prio} -= $_[1]; 350coroutine. This is just a free-form string you can associate with a coroutine.
351
352=cut
353
354sub desc {
355 my $old = $_[0]{desc};
356 $_[0]{desc} = $_[1] if @_ > 1;
357 $old;
277} 358}
278 359
279=back 360=back
280 361
362=head2 GLOBAL FUNCTIONS
363
364=over 4
365
366=item Coro::nready
367
368Returns the number of coroutines that are currently in the ready state,
369i.e. that can be swicthed to. The value C<0> means that the only runnable
370coroutine is the currently running one, so C<cede> would have no effect,
371and C<schedule> would cause a deadlock unless there is an idle handler
372that wakes up some coroutines.
373
374=item unblock_sub { ... }
375
376This utility function takes a BLOCK or code reference and "unblocks" it,
377returning the new coderef. This means that the new coderef will return
378immediately without blocking, returning nothing, while the original code
379ref will be called (with parameters) from within its own coroutine.
380
381The reason this fucntion exists is that many event libraries (such as the
382venerable L<Event|Event> module) are not coroutine-safe (a weaker form
383of thread-safety). This means you must not block within event callbacks,
384otherwise you might suffer from crashes or worse.
385
386This function allows your callbacks to block by executing them in another
387coroutine where it is safe to block. One example where blocking is handy
388is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
389disk.
390
391In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
392creating event callbacks that want to block.
393
394=cut
395
396our @unblock_pool;
397our @unblock_queue;
398our $UNBLOCK_POOL_SIZE = 2;
399
400sub unblock_handler_ {
401 while () {
402 my ($cb, @arg) = @{ delete $Coro::current->{arg} };
403 $cb->(@arg);
404
405 last if @unblock_pool >= $UNBLOCK_POOL_SIZE;
406 push @unblock_pool, $Coro::current;
407 schedule;
408 }
409}
410
411our $unblock_scheduler = async {
412 while () {
413 while (my $cb = pop @unblock_queue) {
414 my $handler = (pop @unblock_pool or new Coro \&unblock_handler_);
415 $handler->{arg} = $cb;
416 $handler->ready;
417 cede;
418 }
419
420 schedule;
421 }
422};
423
424sub unblock_sub(&) {
425 my $cb = shift;
426
427 sub {
428 push @unblock_queue, [$cb, @_];
429 $unblock_scheduler->ready;
430 }
431}
432
433=back
434
281=cut 435=cut
282 436
2831; 4371;
284 438
285=head1 BUGS/LIMITATIONS 439=head1 BUGS/LIMITATIONS
286 440
287 - you must make very sure that no coro is still active on global destruction. 441 - you must make very sure that no coro is still active on global
288 very bad things might happen otherwise (usually segfaults). 442 destruction. very bad things might happen otherwise (usually segfaults).
443
289 - this module is not thread-safe. You must only ever use this module from 444 - this module is not thread-safe. You should only ever use this module
290 the same thread (this requirement might be loosened in the future to 445 from the same thread (this requirement might be losened in the future
291 allow per-thread schedulers, but Coro::State does not yet allow this). 446 to allow per-thread schedulers, but Coro::State does not yet allow
447 this).
292 448
293=head1 SEE ALSO 449=head1 SEE ALSO
294 450
295L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 451Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
296L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>, 452
297L<Coro::Handle>, L<Coro::Socket>. 453Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
454
455Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
456
457Embedding: L<Coro:MakeMaker>
298 458
299=head1 AUTHOR 459=head1 AUTHOR
300 460
301 Marc Lehmann <pcg@goof.com> 461 Marc Lehmann <schmorp@schmorp.de>
302 http://www.goof.com/pcg/marc/ 462 http://home.schmorp.de/
303 463
304=cut 464=cut
305 465

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