ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/Coro/Coro.pm
(Generate patch)

Comparing Coro/Coro.pm (file contents):
Revision 1.143 by root, Tue Oct 2 23:27:52 2007 UTC vs.
Revision 1.268 by root, Thu Oct 1 23:16:27 2009 UTC

1=head1 NAME 1=head1 NAME
2 2
3Coro - coroutine process abstraction 3Coro - the only real threads in perl
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 coroutine like this: 16 cede; # yield to coro
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 use Coro::Semaphore;
19 cede; 22 my $lock = new Coro::Semaphore;
23 my $locked;
24
25 $lock->down;
26 $locked = 1;
27 $lock->up;
20 28
21=head1 DESCRIPTION 29=head1 DESCRIPTION
22 30
23This module collection manages coroutines. Coroutines are similar 31For a tutorial-style introduction, please read the L<Coro::Intro>
24to threads but don't run in parallel at the same time even on SMP 32manpage. This manpage mainly contains reference information.
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.
30 33
31(Perl, however, does not natively support real threads but instead does a 34This module collection manages continuations in general, most often in
32very slow and memory-intensive emulation of processes using threads. This 35the form of cooperative threads (also called coros, or simply "coro"
33is a performance win on Windows machines, and a loss everywhere else). 36in the documentation). They are similar to kernel threads but don't (in
37general) run in parallel at the same time even on SMP machines. The
38specific flavor of thread offered by this module also guarantees you that
39it will not switch between threads unless necessary, at easily-identified
40points in your program, so locking and parallel access are rarely an
41issue, making thread programming much safer and easier than using other
42thread models.
34 43
44Unlike the so-called "Perl threads" (which are not actually real threads
45but only the windows process emulation (see section of same name for more
46details) ported to unix, and as such act as processes), Coro provides
47a full shared address space, which makes communication between threads
48very easy. And Coro's threads are fast, too: disabling the Windows
49process emulation code in your perl and using Coro can easily result in
50a two to four times speed increase for your programs. A parallel matrix
51multiplication benchmark runs over 300 times faster on a single core than
52perl's pseudo-threads on a quad core using all four cores.
53
54Coro achieves that by supporting multiple running interpreters that share
55data, which is especially useful to code pseudo-parallel processes and
56for event-based programming, such as multiple HTTP-GET requests running
57concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
58into an event-based environment.
59
35In this module, coroutines are defined as "callchain + lexical variables + 60In this module, a thread is defined as "callchain + lexical variables +
36@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain, 61some package variables + C stack), that is, a thread has its own callchain,
37its own set of lexicals and its own set of perls most important global 62its own set of lexicals and its own set of perls most important global
38variables. 63variables (see L<Coro::State> for more configuration and background info).
64
65See also the C<SEE ALSO> section at the end of this document - the Coro
66module family is quite large.
39 67
40=cut 68=cut
41 69
42package Coro; 70package Coro;
43 71
44use strict; 72use common::sense;
45no warnings "uninitialized"; 73
74use Carp ();
75
76use Guard ();
46 77
47use Coro::State; 78use Coro::State;
48 79
49use base qw(Coro::State Exporter); 80use base qw(Coro::State Exporter);
50 81
51our $idle; # idle handler 82our $idle; # idle handler
52our $main; # main coroutine 83our $main; # main coro
53our $current; # current coroutine 84our $current; # current coro
54 85
55our $VERSION = '3.8'; 86our $VERSION = 5.17;
56 87
57our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); 88our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
58our %EXPORT_TAGS = ( 89our %EXPORT_TAGS = (
59 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 90 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
60); 91);
61our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); 92our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
62 93
63{ 94=head1 GLOBAL VARIABLES
64 my @async;
65 my $init;
66
67 # this way of handling attributes simply is NOT scalable ;()
68 sub import {
69 no strict 'refs';
70
71 Coro->export_to_level (1, @_);
72
73 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
74 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
75 my ($package, $ref) = (shift, shift);
76 my @attrs;
77 for (@_) {
78 if ($_ eq "Coro") {
79 push @async, $ref;
80 unless ($init++) {
81 eval q{
82 sub INIT {
83 &async(pop @async) while @async;
84 }
85 };
86 }
87 } else {
88 push @attrs, $_;
89 }
90 }
91 return $old ? $old->($package, $ref, @attrs) : @attrs;
92 };
93 }
94
95}
96 95
97=over 4 96=over 4
98 97
99=item $main 98=item $Coro::main
100 99
101This coroutine represents the main program. 100This variable stores the Coro object that represents the main
101program. While you cna C<ready> it and do most other things you can do to
102coro, it is mainly useful to compare again C<$Coro::current>, to see
103whether you are running in the main program or not.
102 104
103=cut 105=cut
104 106
105$main = new Coro; 107# $main is now being initialised by Coro::State
106 108
107=item $current (or as function: current) 109=item $Coro::current
108 110
109The current coroutine (the last coroutine switched to). The initial value 111The Coro object representing the current coro (the last
112coro that the Coro scheduler switched to). The initial value is
110is C<$main> (of course). 113C<$Coro::main> (of course).
111 114
112This variable is B<strictly> I<read-only>. It is provided for performance 115This variable is B<strictly> I<read-only>. You can take copies of the
113reasons. If performance is not essential you are encouraged to use the 116value stored in it and use it as any other Coro object, but you must
114C<Coro::current> function instead. 117not otherwise modify the variable itself.
115 118
116=cut 119=cut
117 120
118$main->{desc} = "[main::]";
119
120# maybe some other module used Coro::Specific before...
121$main->{_specific} = $current->{_specific}
122 if $current;
123
124_set_current $main;
125
126sub current() { $current } 121sub current() { $current } # [DEPRECATED]
127 122
128=item $idle 123=item $Coro::idle
129 124
125This variable is mainly useful to integrate Coro into event loops. It is
126usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
127pretty low-level functionality.
128
129This variable stores either a Coro object or a callback.
130
130A callback that is called whenever the scheduler finds no ready coroutines 131If it is a callback, the it is called whenever the scheduler finds no
131to run. The default implementation prints "FATAL: deadlock detected" and 132ready coros to run. The default implementation prints "FATAL:
132exits, because the program has no other way to continue. 133deadlock detected" and exits, because the program has no other way to
134continue.
133 135
136If it is a coro object, then this object will be readied (without
137invoking any ready hooks, however) when the scheduler finds no other ready
138coros to run.
139
134This hook is overwritten by modules such as C<Coro::Timer> and 140This hook is overwritten by modules such as C<Coro::EV> and
135C<Coro::Event> to wait on an external event that hopefully wake up a 141C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
136coroutine so the scheduler can run it. 142coro so the scheduler can run it.
143
144Note that the callback I<must not>, under any circumstances, block
145the current coro. Normally, this is achieved by having an "idle
146coro" that calls the event loop and then blocks again, and then
147readying that coro in the idle handler, or by simply placing the idle
148coro in this variable.
149
150See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
151technique.
137 152
138Please note that if your callback recursively invokes perl (e.g. for event 153Please note that if your callback recursively invokes perl (e.g. for event
139handlers), then it must be prepared to be called recursively. 154handlers), then it must be prepared to be called recursively itself.
140 155
141=cut 156=cut
142 157
143$idle = sub { 158$idle = sub {
144 require Carp; 159 warn "oi\n";#d#
145 Carp::croak ("FATAL: deadlock detected"); 160 Carp::confess ("FATAL: deadlock detected");
146}; 161};
147 162
148sub _cancel {
149 my ($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->{_on_destroy}) || []};
158}
159
160# this coroutine is necessary because a coroutine 163# this coro is necessary because a coro
161# cannot destroy itself. 164# cannot destroy itself.
162my @destroy; 165our @destroy;
163my $manager; 166our $manager;
164 167
165$manager = new Coro sub { 168$manager = new Coro sub {
166 while () { 169 while () {
167 (shift @destroy)->_cancel 170 Coro::State::cancel shift @destroy
168 while @destroy; 171 while @destroy;
169 172
170 &schedule; 173 &schedule;
171 } 174 }
172}; 175};
173$manager->desc ("[coro manager]"); 176$manager->{desc} = "[coro manager]";
174$manager->prio (PRIO_MAX); 177$manager->prio (PRIO_MAX);
175 178
176# static methods. not really.
177
178=back 179=back
179 180
180=head2 STATIC METHODS 181=head1 SIMPLE CORO CREATION
181
182Static methods are actually functions that operate on the current coroutine only.
183 182
184=over 4 183=over 4
185 184
186=item async { ... } [@args...] 185=item async { ... } [@args...]
187 186
188Create a new asynchronous coroutine and return it's coroutine object 187Create a new coro and return its Coro object (usually
189(usually unused). When the sub returns the new coroutine is automatically 188unused). The coro will be put into the ready queue, so
189it will start running automatically on the next scheduler run.
190
191The first argument is a codeblock/closure that should be executed in the
192coro. When it returns argument returns the coro is automatically
190terminated. 193terminated.
191 194
195The remaining arguments are passed as arguments to the closure.
196
197See the C<Coro::State::new> constructor for info about the coro
198environment in which coro are executed.
199
192Calling C<exit> in a coroutine will do the same as calling exit outside 200Calling C<exit> in a coro will do the same as calling exit outside
193the coroutine. Likewise, when the coroutine dies, the program will exit, 201the coro. Likewise, when the coro dies, the program will exit,
194just as it would in the main program. 202just as it would in the main program.
195 203
204If you do not want that, you can provide a default C<die> handler, or
205simply avoid dieing (by use of C<eval>).
206
196 # create a new coroutine that just prints its arguments 207Example: Create a new coro that just prints its arguments.
208
197 async { 209 async {
198 print "@_\n"; 210 print "@_\n";
199 } 1,2,3,4; 211 } 1,2,3,4;
200 212
201=cut
202
203sub async(&@) {
204 my $coro = new Coro @_;
205 $coro->ready;
206 $coro
207}
208
209=item async_pool { ... } [@args...] 213=item async_pool { ... } [@args...]
210 214
211Similar to C<async>, but uses a coroutine pool, so you should not call 215Similar to C<async>, but uses a coro pool, so you should not call
212terminate or join (although you are allowed to), and you get a coroutine 216terminate or join on it (although you are allowed to), and you get a
213that might have executed other code already (which can be good or bad :). 217coro that might have executed other code already (which can be good
218or bad :).
214 219
220On the plus side, this function is about twice as fast as creating (and
221destroying) a completely new coro, so if you need a lot of generic
222coros in quick successsion, use C<async_pool>, not C<async>.
223
215Also, the block is executed in an C<eval> context and a warning will be 224The code block is executed in an C<eval> context and a warning will be
216issued in case of an exception instead of terminating the program, as 225issued in case of an exception instead of terminating the program, as
217C<async> does. As the coroutine is being reused, stuff like C<on_destroy> 226C<async> does. As the coro is being reused, stuff like C<on_destroy>
218will not work in the expected way, unless you call terminate or cancel, 227will not work in the expected way, unless you call terminate or cancel,
219which somehow defeats the purpose of pooling. 228which somehow defeats the purpose of pooling (but is fine in the
229exceptional case).
220 230
221The priority will be reset to C<0> after each job, otherwise the coroutine 231The priority will be reset to C<0> after each run, tracing will be
222will be re-used "as-is". 232disabled, the description will be reset and the default output filehandle
233gets restored, so you can change all these. Otherwise the coro will
234be re-used "as-is": most notably if you change other per-coro global
235stuff such as C<$/> you I<must needs> revert that change, which is most
236simply done by using local as in: C<< local $/ >>.
223 237
224The pool size is limited to 8 idle coroutines (this can be adjusted by 238The idle pool size is limited to C<8> idle coros (this can be
225changing $Coro::POOL_SIZE), and there can be as many non-idle coros as 239adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
226required. 240coros as required.
227 241
228If you are concerned about pooled coroutines growing a lot because a 242If you are concerned about pooled coros growing a lot because a
229single C<async_pool> used a lot of stackspace you can e.g. C<async_pool 243single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
230{ terminate }> once per second or so to slowly replenish the pool. In 244{ terminate }> once per second or so to slowly replenish the pool. In
231addition to that, when the stacks used by a handler grows larger than 16kb 245addition to that, when the stacks used by a handler grows larger than 32kb
232(adjustable with $Coro::POOL_RSS) it will also exit. 246(adjustable via $Coro::POOL_RSS) it will also be destroyed.
233 247
234=cut 248=cut
235 249
236our $POOL_SIZE = 8; 250our $POOL_SIZE = 8;
237our $POOL_RSS = 16 * 1024; 251our $POOL_RSS = 32 * 1024;
238our @async_pool; 252our @async_pool;
239 253
240sub pool_handler { 254sub pool_handler {
241 my $cb;
242
243 while () { 255 while () {
244 eval { 256 eval {
245 while () { 257 &{&_pool_handler} while 1;
246 _pool_1 $cb;
247 &$cb;
248 _pool_2 $cb;
249 &schedule;
250 }
251 }; 258 };
252 259
253 last if $@ eq "\3terminate\2\n";
254 warn $@ if $@; 260 warn $@ if $@;
255 } 261 }
256} 262}
257 263
258sub async_pool(&@) { 264=back
259 # this is also inlined into the unlock_scheduler
260 my $coro = (pop @async_pool) || new Coro \&pool_handler;
261 265
262 $coro->{_invoke} = [@_]; 266=head1 STATIC METHODS
263 $coro->ready;
264 267
265 $coro 268Static methods are actually functions that implicitly operate on the
266} 269current coro.
270
271=over 4
267 272
268=item schedule 273=item schedule
269 274
270Calls the scheduler. Please note that the current coroutine will not be put 275Calls the scheduler. The scheduler will find the next coro that is
276to be run from the ready queue and switches to it. The next coro
277to be run is simply the one with the highest priority that is longest
278in its ready queue. If there is no coro ready, it will clal the
279C<$Coro::idle> hook.
280
281Please note that the current coro will I<not> be put into the ready
271into the ready queue, so calling this function usually means you will 282queue, so calling this function usually means you will never be called
272never be called again unless something else (e.g. an event handler) calls 283again unless something else (e.g. an event handler) calls C<< ->ready >>,
273ready. 284thus waking you up.
274 285
275The canonical way to wait on external events is this: 286This makes C<schedule> I<the> generic method to use to block the current
287coro and wait for events: first you remember the current coro in
288a variable, then arrange for some callback of yours to call C<< ->ready
289>> on that once some event happens, and last you call C<schedule> to put
290yourself to sleep. Note that a lot of things can wake your coro up,
291so you need to check whether the event indeed happened, e.g. by storing the
292status in a variable.
276 293
277 { 294See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
278 # remember current coroutine
279 my $current = $Coro::current;
280 295
281 # register a hypothetical event handler 296=item cede
282 on_event_invoke sub { 297
283 # wake up sleeping coroutine 298"Cede" to other coros. This function puts the current coro into
284 $current->ready; 299the ready queue and calls C<schedule>, which has the effect of giving
285 undef $current; 300up the current "timeslice" to other coros of the same or higher
301priority. Once your coro gets its turn again it will automatically be
302resumed.
303
304This function is often called C<yield> in other languages.
305
306=item Coro::cede_notself
307
308Works like cede, but is not exported by default and will cede to I<any>
309coro, regardless of priority. This is useful sometimes to ensure
310progress is made.
311
312=item terminate [arg...]
313
314Terminates the current coro with the given status values (see L<cancel>).
315
316=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
317
318These function install enter and leave winders in the current scope. The
319enter block will be executed when on_enter is called and whenever the
320current coro is re-entered by the scheduler, while the leave block is
321executed whenever the current coro is blocked by the scheduler, and
322also when the containing scope is exited (by whatever means, be it exit,
323die, last etc.).
324
325I<Neither invoking the scheduler, nor exceptions, are allowed within those
326BLOCKs>. That means: do not even think about calling C<die> without an
327eval, and do not even think of entering the scheduler in any way.
328
329Since both BLOCKs are tied to the current scope, they will automatically
330be removed when the current scope exits.
331
332These functions implement the same concept as C<dynamic-wind> in scheme
333does, and are useful when you want to localise some resource to a specific
334coro.
335
336They slow down thread switching considerably for coros that use them
337(about 40% for a BLOCK with a single assignment, so thread switching is
338still reasonably fast if the handlers are fast).
339
340These functions are best understood by an example: The following function
341will change the current timezone to "Antarctica/South_Pole", which
342requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
343which remember/change the current timezone and restore the previous
344value, respectively, the timezone is only changed for the coro that
345installed those handlers.
346
347 use POSIX qw(tzset);
348
349 async {
350 my $old_tz; # store outside TZ value here
351
352 Coro::on_enter {
353 $old_tz = $ENV{TZ}; # remember the old value
354
355 $ENV{TZ} = "Antarctica/South_Pole";
356 tzset; # enable new value
286 }; 357 };
287 358
288 # call schedule until event occurred. 359 Coro::on_leave {
289 # in case we are woken up for other reasons 360 $ENV{TZ} = $old_tz;
290 # (current still defined), loop. 361 tzset; # restore old value
291 Coro::schedule while $current; 362 };
363
364 # at this place, the timezone is Antarctica/South_Pole,
365 # without disturbing the TZ of any other coro.
292 } 366 };
293 367
294=item cede 368This can be used to localise about any resource (locale, uid, current
369working directory etc.) to a block, despite the existance of other
370coros.
295 371
296"Cede" to other coroutines. This function puts the current coroutine into the 372Another interesting example implements time-sliced multitasking using
297ready queue and calls C<schedule>, which has the effect of giving up the 373interval timers (this could obviously be optimised, but does the job):
298current "timeslice" to other coroutines of the same or higher priority.
299 374
300Returns true if at least one coroutine switch has happened. 375 # "timeslice" the given block
376 sub timeslice(&) {
377 use Time::HiRes ();
301 378
302=item Coro::cede_notself 379 Coro::on_enter {
380 # on entering the thread, we set an VTALRM handler to cede
381 $SIG{VTALRM} = sub { cede };
382 # and then start the interval timer
383 Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
384 };
385 Coro::on_leave {
386 # on leaving the thread, we stop the interval timer again
387 Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
388 };
303 389
304Works like cede, but is not exported by default and will cede to any 390 &{+shift};
305coroutine, regardless of priority, once. 391 }
306 392
307Returns true if at least one coroutine switch has happened. 393 # use like this:
394 timeslice {
395 # The following is an endless loop that would normally
396 # monopolise the process. Since it runs in a timesliced
397 # environment, it will regularly cede to other threads.
398 while () { }
399 };
308 400
309=item terminate [arg...]
310
311Terminates the current coroutine with the given status values (see L<cancel>).
312 401
313=item killall 402=item killall
314 403
315Kills/terminates/cancels all coroutines except the currently running 404Kills/terminates/cancels all coros except the currently running one.
316one. This is useful after a fork, either in the child or the parent, as
317usually only one of them should inherit the running coroutines.
318 405
319=cut 406Note that while this will try to free some of the main interpreter
407resources if the calling coro isn't the main coro, but one
408cannot free all of them, so if a coro that is not the main coro
409calls this function, there will be some one-time resource leak.
320 410
321sub terminate { 411=cut
322 $current->cancel (@_);
323}
324 412
325sub killall { 413sub killall {
326 for (Coro::State::list) { 414 for (Coro::State::list) {
327 $_->cancel 415 $_->cancel
328 if $_ != $current && UNIVERSAL::isa $_, "Coro"; 416 if $_ != $current && UNIVERSAL::isa $_, "Coro";
329 } 417 }
330} 418}
331 419
332=back 420=back
333 421
334# dynamic methods
335
336=head2 COROUTINE METHODS 422=head1 CORO OBJECT METHODS
337 423
338These are the methods you can call on coroutine objects. 424These are the methods you can call on coro objects (or to create
425them).
339 426
340=over 4 427=over 4
341 428
342=item new Coro \&sub [, @args...] 429=item new Coro \&sub [, @args...]
343 430
344Create a new coroutine and return it. When the sub returns the coroutine 431Create a new coro and return it. When the sub returns, the coro
345automatically terminates as if C<terminate> with the returned values were 432automatically terminates as if C<terminate> with the returned values were
346called. To make the coroutine run you must first put it into the ready queue 433called. To make the coro run you must first put it into the ready
347by calling the ready method. 434queue by calling the ready method.
348 435
349See C<async> for additional discussion. 436See C<async> and C<Coro::State::new> for additional info about the
437coro environment.
350 438
351=cut 439=cut
352 440
353sub _run_coro { 441sub _coro_run {
354 terminate &{+shift}; 442 terminate &{+shift};
355} 443}
356 444
357sub new {
358 my $class = shift;
359
360 $class->SUPER::new (\&_run_coro, @_)
361}
362
363=item $success = $coroutine->ready 445=item $success = $coro->ready
364 446
365Put the given coroutine into the ready queue (according to it's priority) 447Put the given coro into the end of its ready queue (there is one
366and return true. If the coroutine is already in the ready queue, do nothing 448queue for each priority) and return true. If the coro is already in
367and return false. 449the ready queue, do nothing and return false.
368 450
451This ensures that the scheduler will resume this coro automatically
452once all the coro of higher priority and all coro of the same
453priority that were put into the ready queue earlier have been resumed.
454
455=item $coro->suspend
456
457Suspends the specified coro. A suspended coro works just like any other
458coro, except that the scheduler will not select a suspended coro for
459execution.
460
461Suspending a coro can be useful when you want to keep the coro from
462running, but you don't want to destroy it, or when you want to temporarily
463freeze a coro (e.g. for debugging) to resume it later.
464
465A scenario for the former would be to suspend all (other) coros after a
466fork and keep them alive, so their destructors aren't called, but new
467coros can be created.
468
469=item $coro->resume
470
471If the specified coro was suspended, it will be resumed. Note that when
472the coro was in the ready queue when it was suspended, it might have been
473unreadied by the scheduler, so an activation might have been lost.
474
475To avoid this, it is best to put a suspended coro into the ready queue
476unconditionally, as every synchronisation mechanism must protect itself
477against spurious wakeups, and the one in the Coro family certainly do
478that.
479
369=item $is_ready = $coroutine->is_ready 480=item $is_ready = $coro->is_ready
370 481
371Return wether the coroutine is currently the ready queue or not, 482Returns true iff the Coro object is in the ready queue. Unless the Coro
483object gets destroyed, it will eventually be scheduled by the scheduler.
372 484
485=item $is_running = $coro->is_running
486
487Returns true iff the Coro object is currently running. Only one Coro object
488can ever be in the running state (but it currently is possible to have
489multiple running Coro::States).
490
491=item $is_suspended = $coro->is_suspended
492
493Returns true iff this Coro object has been suspended. Suspended Coros will
494not ever be scheduled.
495
373=item $coroutine->cancel (arg...) 496=item $coro->cancel (arg...)
374 497
375Terminates the given coroutine and makes it return the given arguments as 498Terminates the given Coro and makes it return the given arguments as
376status (default: the empty list). Never returns if the coroutine is the 499status (default: the empty list). Never returns if the Coro is the
377current coroutine. 500current Coro.
378 501
379=cut 502=cut
380 503
381sub cancel { 504sub cancel {
382 my $self = shift; 505 my $self = shift;
383 $self->{_status} = [@_];
384 506
385 if ($current == $self) { 507 if ($current == $self) {
386 push @destroy, $self; 508 terminate @_;
387 $manager->ready;
388 &schedule while 1;
389 } else { 509 } else {
390 $self->_cancel; 510 $self->{_status} = [@_];
511 Coro::State::cancel $self;
391 } 512 }
392} 513}
393 514
515=item $coro->schedule_to
516
517Puts the current coro to sleep (like C<Coro::schedule>), but instead
518of continuing with the next coro from the ready queue, always switch to
519the given coro object (regardless of priority etc.). The readyness
520state of that coro isn't changed.
521
522This is an advanced method for special cases - I'd love to hear about any
523uses for this one.
524
525=item $coro->cede_to
526
527Like C<schedule_to>, but puts the current coro into the ready
528queue. This has the effect of temporarily switching to the given
529coro, and continuing some time later.
530
531This is an advanced method for special cases - I'd love to hear about any
532uses for this one.
533
534=item $coro->throw ([$scalar])
535
536If C<$throw> is specified and defined, it will be thrown as an exception
537inside the coro at the next convenient point in time. Otherwise
538clears the exception object.
539
540Coro will check for the exception each time a schedule-like-function
541returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
542>>, C<< Coro::Handle->readable >> and so on. Most of these functions
543detect this case and return early in case an exception is pending.
544
545The exception object will be thrown "as is" with the specified scalar in
546C<$@>, i.e. if it is a string, no line number or newline will be appended
547(unlike with C<die>).
548
549This can be used as a softer means than C<cancel> to ask a coro to
550end itself, although there is no guarantee that the exception will lead to
551termination, and if the exception isn't caught it might well end the whole
552program.
553
554You might also think of C<throw> as being the moral equivalent of
555C<kill>ing a coro with a signal (in this case, a scalar).
556
394=item $coroutine->join 557=item $coro->join
395 558
396Wait until the coroutine terminates and return any values given to the 559Wait until the coro terminates and return any values given to the
397C<terminate> or C<cancel> functions. C<join> can be called concurrently 560C<terminate> or C<cancel> functions. C<join> can be called concurrently
398from multiple coroutines. 561from multiple coro, and all will be resumed and given the status
562return once the C<$coro> terminates.
399 563
400=cut 564=cut
401 565
402sub join { 566sub join {
403 my $self = shift; 567 my $self = shift;
414 } 578 }
415 579
416 wantarray ? @{$self->{_status}} : $self->{_status}[0]; 580 wantarray ? @{$self->{_status}} : $self->{_status}[0];
417} 581}
418 582
419=item $coroutine->on_destroy (\&cb) 583=item $coro->on_destroy (\&cb)
420 584
421Registers a callback that is called when this coroutine gets destroyed, 585Registers a callback that is called when this coro gets destroyed,
422but before it is joined. The callback gets passed the terminate arguments, 586but before it is joined. The callback gets passed the terminate arguments,
423if any. 587if any, and I<must not> die, under any circumstances.
424 588
425=cut 589=cut
426 590
427sub on_destroy { 591sub on_destroy {
428 my ($self, $cb) = @_; 592 my ($self, $cb) = @_;
429 593
430 push @{ $self->{_on_destroy} }, $cb; 594 push @{ $self->{_on_destroy} }, $cb;
431} 595}
432 596
433=item $oldprio = $coroutine->prio ($newprio) 597=item $oldprio = $coro->prio ($newprio)
434 598
435Sets (or gets, if the argument is missing) the priority of the 599Sets (or gets, if the argument is missing) the priority of the
436coroutine. Higher priority coroutines get run before lower priority 600coro. Higher priority coro get run before lower priority
437coroutines. Priorities are small signed integers (currently -4 .. +3), 601coro. Priorities are small signed integers (currently -4 .. +3),
438that you can refer to using PRIO_xxx constants (use the import tag :prio 602that you can refer to using PRIO_xxx constants (use the import tag :prio
439to get then): 603to get then):
440 604
441 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 605 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
442 3 > 1 > 0 > -1 > -3 > -4 606 3 > 1 > 0 > -1 > -3 > -4
443 607
444 # set priority to HIGH 608 # set priority to HIGH
445 current->prio(PRIO_HIGH); 609 current->prio (PRIO_HIGH);
446 610
447The idle coroutine ($Coro::idle) always has a lower priority than any 611The idle coro ($Coro::idle) always has a lower priority than any
448existing coroutine. 612existing coro.
449 613
450Changing the priority of the current coroutine will take effect immediately, 614Changing the priority of the current coro will take effect immediately,
451but changing the priority of coroutines in the ready queue (but not 615but changing the priority of coro in the ready queue (but not
452running) will only take effect after the next schedule (of that 616running) will only take effect after the next schedule (of that
453coroutine). This is a bug that will be fixed in some future version. 617coro). This is a bug that will be fixed in some future version.
454 618
455=item $newprio = $coroutine->nice ($change) 619=item $newprio = $coro->nice ($change)
456 620
457Similar to C<prio>, but subtract the given value from the priority (i.e. 621Similar to C<prio>, but subtract the given value from the priority (i.e.
458higher values mean lower priority, just as in unix). 622higher values mean lower priority, just as in unix).
459 623
460=item $olddesc = $coroutine->desc ($newdesc) 624=item $olddesc = $coro->desc ($newdesc)
461 625
462Sets (or gets in case the argument is missing) the description for this 626Sets (or gets in case the argument is missing) the description for this
463coroutine. This is just a free-form string you can associate with a coroutine. 627coro. This is just a free-form string you can associate with a
628coro.
464 629
465This method simply sets the C<< $coroutine->{desc} >> member to the given string. You 630This method simply sets the C<< $coro->{desc} >> member to the given
466can modify this member directly if you wish. 631string. You can modify this member directly if you wish.
467 632
468=cut 633=cut
469 634
470sub desc { 635sub desc {
471 my $old = $_[0]{desc}; 636 my $old = $_[0]{desc};
472 $_[0]{desc} = $_[1] if @_ > 1; 637 $_[0]{desc} = $_[1] if @_ > 1;
473 $old; 638 $old;
474} 639}
475 640
641sub transfer {
642 require Carp;
643 Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
644}
645
476=back 646=back
477 647
478=head2 GLOBAL FUNCTIONS 648=head1 GLOBAL FUNCTIONS
479 649
480=over 4 650=over 4
481 651
482=item Coro::nready 652=item Coro::nready
483 653
484Returns the number of coroutines that are currently in the ready state, 654Returns the number of coro that are currently in the ready state,
485i.e. that can be switched to. The value C<0> means that the only runnable 655i.e. that can be switched to by calling C<schedule> directory or
656indirectly. The value C<0> means that the only runnable coro is the
486coroutine is the currently running one, so C<cede> would have no effect, 657currently running one, so C<cede> would have no effect, and C<schedule>
487and C<schedule> would cause a deadlock unless there is an idle handler 658would cause a deadlock unless there is an idle handler that wakes up some
488that wakes up some coroutines. 659coro.
489 660
490=item my $guard = Coro::guard { ... } 661=item my $guard = Coro::guard { ... }
491 662
492This creates and returns a guard object. Nothing happens until the object 663This function still exists, but is deprecated. Please use the
493gets destroyed, in which case the codeblock given as argument will be 664C<Guard::guard> function instead.
494executed. This is useful to free locks or other resources in case of a
495runtime error or when the coroutine gets canceled, as in both cases the
496guard block will be executed. The guard object supports only one method,
497C<< ->cancel >>, which will keep the codeblock from being executed.
498 665
499Example: set some flag and clear it again when the coroutine gets canceled
500or the function returns:
501
502 sub do_something {
503 my $guard = Coro::guard { $busy = 0 };
504 $busy = 1;
505
506 # do something that requires $busy to be true
507 }
508
509=cut 666=cut
510 667
511sub guard(&) { 668BEGIN { *guard = \&Guard::guard }
512 bless \(my $cb = $_[0]), "Coro::guard"
513}
514
515sub Coro::guard::cancel {
516 ${$_[0]} = sub { };
517}
518
519sub Coro::guard::DESTROY {
520 ${$_[0]}->();
521}
522
523 669
524=item unblock_sub { ... } 670=item unblock_sub { ... }
525 671
526This utility function takes a BLOCK or code reference and "unblocks" it, 672This utility function takes a BLOCK or code reference and "unblocks" it,
527returning the new coderef. This means that the new coderef will return 673returning a new coderef. Unblocking means that calling the new coderef
528immediately without blocking, returning nothing, while the original code 674will return immediately without blocking, returning nothing, while the
529ref will be called (with parameters) from within its own coroutine. 675original code ref will be called (with parameters) from within another
676coro.
530 677
531The reason this function exists is that many event libraries (such as the 678The reason this function exists is that many event libraries (such as the
532venerable L<Event|Event> module) are not coroutine-safe (a weaker form 679venerable L<Event|Event> module) are not thread-safe (a weaker form
533of thread-safety). This means you must not block within event callbacks, 680of reentrancy). This means you must not block within event callbacks,
534otherwise you might suffer from crashes or worse. 681otherwise you might suffer from crashes or worse. The only event library
682currently known that is safe to use without C<unblock_sub> is L<EV>.
535 683
536This function allows your callbacks to block by executing them in another 684This function allows your callbacks to block by executing them in another
537coroutine where it is safe to block. One example where blocking is handy 685coro where it is safe to block. One example where blocking is handy
538is when you use the L<Coro::AIO|Coro::AIO> functions to save results to 686is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
539disk. 687disk, for example.
540 688
541In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when 689In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
542creating event callbacks that want to block. 690creating event callbacks that want to block.
691
692If your handler does not plan to block (e.g. simply sends a message to
693another coro, or puts some other coro into the ready queue), there is
694no reason to use C<unblock_sub>.
695
696Note that you also need to use C<unblock_sub> for any other callbacks that
697are indirectly executed by any C-based event loop. For example, when you
698use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
699provides callbacks that are the result of some event callback, then you
700must not block either, or use C<unblock_sub>.
543 701
544=cut 702=cut
545 703
546our @unblock_queue; 704our @unblock_queue;
547 705
550# return immediately and can be reused) and because we cannot cede 708# return immediately and can be reused) and because we cannot cede
551# inside an event callback. 709# inside an event callback.
552our $unblock_scheduler = new Coro sub { 710our $unblock_scheduler = new Coro sub {
553 while () { 711 while () {
554 while (my $cb = pop @unblock_queue) { 712 while (my $cb = pop @unblock_queue) {
555 # this is an inlined copy of async_pool 713 &async_pool (@$cb);
556 my $coro = (pop @async_pool) || new Coro \&pool_handler;
557 714
558 $coro->{_invoke} = $cb;
559 $coro->ready;
560 cede; # for short-lived callbacks, this reduces pressure on the coro pool 715 # for short-lived callbacks, this reduces pressure on the coro pool
716 # as the chance is very high that the async_poll coro will be back
717 # in the idle state when cede returns
718 cede;
561 } 719 }
562 schedule; # sleep well 720 schedule; # sleep well
563 } 721 }
564}; 722};
565$unblock_scheduler->desc ("[unblock_sub scheduler]"); 723$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
566 724
567sub unblock_sub(&) { 725sub unblock_sub(&) {
568 my $cb = shift; 726 my $cb = shift;
569 727
570 sub { 728 sub {
571 unshift @unblock_queue, [$cb, @_]; 729 unshift @unblock_queue, [$cb, @_];
572 $unblock_scheduler->ready; 730 $unblock_scheduler->ready;
573 } 731 }
574} 732}
575 733
734=item $cb = Coro::rouse_cb
735
736Create and return a "rouse callback". That's a code reference that,
737when called, will remember a copy of its arguments and notify the owner
738coro of the callback.
739
740See the next function.
741
742=item @args = Coro::rouse_wait [$cb]
743
744Wait for the specified rouse callback (or the last one that was created in
745this coro).
746
747As soon as the callback is invoked (or when the callback was invoked
748before C<rouse_wait>), it will return the arguments originally passed to
749the rouse callback. In scalar context, that means you get the I<last>
750argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
751statement at the end.
752
753See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
754
576=back 755=back
577 756
578=cut 757=cut
579 758
5801; 7591;
581 760
761=head1 HOW TO WAIT FOR A CALLBACK
762
763It is very common for a coro to wait for some callback to be
764called. This occurs naturally when you use coro in an otherwise
765event-based program, or when you use event-based libraries.
766
767These typically register a callback for some event, and call that callback
768when the event occured. In a coro, however, you typically want to
769just wait for the event, simplyifying things.
770
771For example C<< AnyEvent->child >> registers a callback to be called when
772a specific child has exited:
773
774 my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
775
776But from within a coro, you often just want to write this:
777
778 my $status = wait_for_child $pid;
779
780Coro offers two functions specifically designed to make this easy,
781C<Coro::rouse_cb> and C<Coro::rouse_wait>.
782
783The first function, C<rouse_cb>, generates and returns a callback that,
784when invoked, will save its arguments and notify the coro that
785created the callback.
786
787The second function, C<rouse_wait>, waits for the callback to be called
788(by calling C<schedule> to go to sleep) and returns the arguments
789originally passed to the callback.
790
791Using these functions, it becomes easy to write the C<wait_for_child>
792function mentioned above:
793
794 sub wait_for_child($) {
795 my ($pid) = @_;
796
797 my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
798
799 my ($rpid, $rstatus) = Coro::rouse_wait;
800 $rstatus
801 }
802
803In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
804you can roll your own, using C<schedule>:
805
806 sub wait_for_child($) {
807 my ($pid) = @_;
808
809 # store the current coro in $current,
810 # and provide result variables for the closure passed to ->child
811 my $current = $Coro::current;
812 my ($done, $rstatus);
813
814 # pass a closure to ->child
815 my $watcher = AnyEvent->child (pid => $pid, cb => sub {
816 $rstatus = $_[1]; # remember rstatus
817 $done = 1; # mark $rstatus as valud
818 });
819
820 # wait until the closure has been called
821 schedule while !$done;
822
823 $rstatus
824 }
825
826
582=head1 BUGS/LIMITATIONS 827=head1 BUGS/LIMITATIONS
583 828
584 - you must make very sure that no coro is still active on global 829=over 4
585 destruction. very bad things might happen otherwise (usually segfaults).
586 830
831=item fork with pthread backend
832
833When Coro is compiled using the pthread backend (which isn't recommended
834but required on many BSDs as their libcs are completely broken), then
835coro will not survive a fork. There is no known workaround except to
836fix your libc and use a saner backend.
837
838=item perl process emulation ("threads")
839
587 - this module is not thread-safe. You should only ever use this module 840This module is not perl-pseudo-thread-safe. You should only ever use this
588 from the same thread (this requirement might be loosened in the future 841module from the first thread (this requirement might be removed in the
589 to allow per-thread schedulers, but Coro::State does not yet allow 842future to allow per-thread schedulers, but Coro::State does not yet allow
590 this). 843this). I recommend disabling thread support and using processes, as having
844the windows process emulation enabled under unix roughly halves perl
845performance, even when not used.
846
847=item coro switching is not signal safe
848
849You must not switch to another coro from within a signal handler
850(only relevant with %SIG - most event libraries provide safe signals).
851
852That means you I<MUST NOT> call any function that might "block" the
853current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
854anything that calls those. Everything else, including calling C<ready>,
855works.
856
857=back
858
859
860=head1 WINDOWS PROCESS EMULATION
861
862A great many people seem to be confused about ithreads (for example, Chip
863Salzenberg called me unintelligent, incapable, stupid and gullible,
864while in the same mail making rather confused statements about perl
865ithreads (for example, that memory or files would be shared), showing his
866lack of understanding of this area - if it is hard to understand for Chip,
867it is probably not obvious to everybody).
868
869What follows is an ultra-condensed version of my talk about threads in
870scripting languages given onthe perl workshop 2009:
871
872The so-called "ithreads" were originally implemented for two reasons:
873first, to (badly) emulate unix processes on native win32 perls, and
874secondly, to replace the older, real thread model ("5.005-threads").
875
876It does that by using threads instead of OS processes. The difference
877between processes and threads is that threads share memory (and other
878state, such as files) between threads within a single process, while
879processes do not share anything (at least not semantically). That
880means that modifications done by one thread are seen by others, while
881modifications by one process are not seen by other processes.
882
883The "ithreads" work exactly like that: when creating a new ithreads
884process, all state is copied (memory is copied physically, files and code
885is copied logically). Afterwards, it isolates all modifications. On UNIX,
886the same behaviour can be achieved by using operating system processes,
887except that UNIX typically uses hardware built into the system to do this
888efficiently, while the windows process emulation emulates this hardware in
889software (rather efficiently, but of course it is still much slower than
890dedicated hardware).
891
892As mentioned before, loading code, modifying code, modifying data
893structures and so on is only visible in the ithreads process doing the
894modification, not in other ithread processes within the same OS process.
895
896This is why "ithreads" do not implement threads for perl at all, only
897processes. What makes it so bad is that on non-windows platforms, you can
898actually take advantage of custom hardware for this purpose (as evidenced
899by the forks module, which gives you the (i-) threads API, just much
900faster).
901
902Sharing data is in the i-threads model is done by transfering data
903structures between threads using copying semantics, which is very slow -
904shared data simply does not exist. Benchmarks using i-threads which are
905communication-intensive show extremely bad behaviour with i-threads (in
906fact, so bad that Coro, which cannot take direct advantage of multiple
907CPUs, is often orders of magnitude faster because it shares data using
908real threads, refer to my talk for details).
909
910As summary, i-threads *use* threads to implement processes, while
911the compatible forks module *uses* processes to emulate, uhm,
912processes. I-threads slow down every perl program when enabled, and
913outside of windows, serve no (or little) practical purpose, but
914disadvantages every single-threaded Perl program.
915
916This is the reason that I try to avoid the name "ithreads", as it is
917misleading as it implies that it implements some kind of thread model for
918perl, and prefer the name "windows process emulation", which describes the
919actual use and behaviour of it much better.
591 920
592=head1 SEE ALSO 921=head1 SEE ALSO
593 922
923Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
924
925Debugging: L<Coro::Debug>.
926
594Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>. 927Support/Utility: L<Coro::Specific>, L<Coro::Util>.
595 928
596Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. 929Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
930L<Coro::SemaphoreSet>, L<Coro::RWLock>.
597 931
598Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>. 932I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
599 933
600Embedding: L<Coro:MakeMaker> 934Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
935a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
936L<Coro::Select>.
937
938XS API: L<Coro::MakeMaker>.
939
940Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
601 941
602=head1 AUTHOR 942=head1 AUTHOR
603 943
604 Marc Lehmann <schmorp@schmorp.de> 944 Marc Lehmann <schmorp@schmorp.de>
605 http://home.schmorp.de/ 945 http://home.schmorp.de/

Diff Legend

Removed lines
+ Added lines
< Changed lines
> Changed lines