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

Comparing Coro/Coro.pm (file contents):
Revision 1.142 by root, Tue Oct 2 23:16:24 2007 UTC vs.
Revision 1.269 by root, Thu Oct 1 23:25:03 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$idle = sub {
144 require Carp;
145 Carp::croak ("FATAL: deadlock detected"); 159 Carp::confess ("FATAL: deadlock detected");
146}; 160};
147 161
148sub _cancel {
149 my ($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 162# this coro is necessary because a coro
161# cannot destroy itself. 163# cannot destroy itself.
162my @destroy; 164our @destroy;
163my $manager; 165our $manager;
164 166
165$manager = new Coro sub { 167$manager = new Coro sub {
166 while () { 168 while () {
167 (shift @destroy)->_cancel 169 Coro::State::cancel shift @destroy
168 while @destroy; 170 while @destroy;
169 171
170 &schedule; 172 &schedule;
171 } 173 }
172}; 174};
173$manager->desc ("[coro manager]"); 175$manager->{desc} = "[coro manager]";
174$manager->prio (PRIO_MAX); 176$manager->prio (PRIO_MAX);
175 177
176# static methods. not really.
177
178=back 178=back
179 179
180=head2 STATIC METHODS 180=head1 SIMPLE CORO CREATION
181
182Static methods are actually functions that operate on the current coroutine only.
183 181
184=over 4 182=over 4
185 183
186=item async { ... } [@args...] 184=item async { ... } [@args...]
187 185
188Create a new asynchronous coroutine and return it's coroutine object 186Create a new coro and return its Coro object (usually
189(usually unused). When the sub returns the new coroutine is automatically 187unused). The coro will be put into the ready queue, so
188it will start running automatically on the next scheduler run.
189
190The first argument is a codeblock/closure that should be executed in the
191coro. When it returns argument returns the coro is automatically
190terminated. 192terminated.
191 193
194The remaining arguments are passed as arguments to the closure.
195
196See the C<Coro::State::new> constructor for info about the coro
197environment in which coro are executed.
198
192Calling C<exit> in a coroutine will do the same as calling exit outside 199Calling C<exit> in a coro will do the same as calling exit outside
193the coroutine. Likewise, when the coroutine dies, the program will exit, 200the coro. Likewise, when the coro dies, the program will exit,
194just as it would in the main program. 201just as it would in the main program.
195 202
203If you do not want that, you can provide a default C<die> handler, or
204simply avoid dieing (by use of C<eval>).
205
196 # create a new coroutine that just prints its arguments 206Example: Create a new coro that just prints its arguments.
207
197 async { 208 async {
198 print "@_\n"; 209 print "@_\n";
199 } 1,2,3,4; 210 } 1,2,3,4;
200 211
201=cut
202
203sub async(&@) {
204 my $coro = new Coro @_;
205 $coro->ready;
206 $coro
207}
208
209=item async_pool { ... } [@args...] 212=item async_pool { ... } [@args...]
210 213
211Similar to C<async>, but uses a coroutine pool, so you should not call 214Similar to C<async>, but uses a coro pool, so you should not call
212terminate or join (although you are allowed to), and you get a coroutine 215terminate or join on it (although you are allowed to), and you get a
213that might have executed other code already (which can be good or bad :). 216coro that might have executed other code already (which can be good
217or bad :).
214 218
219On the plus side, this function is about twice as fast as creating (and
220destroying) a completely new coro, so if you need a lot of generic
221coros in quick successsion, use C<async_pool>, not C<async>.
222
215Also, the block is executed in an C<eval> context and a warning will be 223The code block is executed in an C<eval> context and a warning will be
216issued in case of an exception instead of terminating the program, as 224issued in case of an exception instead of terminating the program, as
217C<async> does. As the coroutine is being reused, stuff like C<on_destroy> 225C<async> does. As the coro is being reused, stuff like C<on_destroy>
218will not work in the expected way, unless you call terminate or cancel, 226will not work in the expected way, unless you call terminate or cancel,
219which somehow defeats the purpose of pooling. 227which somehow defeats the purpose of pooling (but is fine in the
228exceptional case).
220 229
221The priority will be reset to C<0> after each job, otherwise the coroutine 230The priority will be reset to C<0> after each run, tracing will be
222will be re-used "as-is". 231disabled, the description will be reset and the default output filehandle
232gets restored, so you can change all these. Otherwise the coro will
233be re-used "as-is": most notably if you change other per-coro global
234stuff such as C<$/> you I<must needs> revert that change, which is most
235simply done by using local as in: C<< local $/ >>.
223 236
224The pool size is limited to 8 idle coroutines (this can be adjusted by 237The 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 238adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
226required. 239coros as required.
227 240
228If you are concerned about pooled coroutines growing a lot because a 241If 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 242single 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 243{ 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 244addition to that, when the stacks used by a handler grows larger than 32kb
232(adjustable with $Coro::POOL_RSS) it will also exit. 245(adjustable via $Coro::POOL_RSS) it will also be destroyed.
233 246
234=cut 247=cut
235 248
236our $POOL_SIZE = 8; 249our $POOL_SIZE = 8;
237our $POOL_RSS = 16 * 1024; 250our $POOL_RSS = 32 * 1024;
238our @async_pool; 251our @async_pool;
239 252
240sub pool_handler { 253sub pool_handler {
241 my $cb;
242
243 while () { 254 while () {
244 eval { 255 eval {
245 while () { 256 &{&_pool_handler} while 1;
246 _pool_1 $cb;
247 &$cb;
248 _pool_2 $cb;
249 &schedule;
250 }
251 }; 257 };
252 258
253 last if $@ eq "\3terminate\2\n";
254 warn $@ if $@; 259 warn $@ if $@;
255 } 260 }
256} 261}
257 262
258sub async_pool(&@) { 263=back
259 # this is also inlined into the unlock_scheduler
260 my $coro = (pop @async_pool) || new Coro \&pool_handler;
261 264
262 $coro->{_invoke} = [@_]; 265=head1 STATIC METHODS
263 $coro->ready;
264 266
265 $coro 267Static methods are actually functions that implicitly operate on the
266} 268current coro.
269
270=over 4
267 271
268=item schedule 272=item schedule
269 273
270Calls the scheduler. Please note that the current coroutine will not be put 274Calls the scheduler. The scheduler will find the next coro that is
275to be run from the ready queue and switches to it. The next coro
276to be run is simply the one with the highest priority that is longest
277in its ready queue. If there is no coro ready, it will clal the
278C<$Coro::idle> hook.
279
280Please 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 281queue, so calling this function usually means you will never be called
272never be called again unless something else (e.g. an event handler) calls 282again unless something else (e.g. an event handler) calls C<< ->ready >>,
273ready. 283thus waking you up.
274 284
275The canonical way to wait on external events is this: 285This makes C<schedule> I<the> generic method to use to block the current
286coro and wait for events: first you remember the current coro in
287a variable, then arrange for some callback of yours to call C<< ->ready
288>> on that once some event happens, and last you call C<schedule> to put
289yourself to sleep. Note that a lot of things can wake your coro up,
290so you need to check whether the event indeed happened, e.g. by storing the
291status in a variable.
276 292
277 { 293See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
278 # remember current coroutine
279 my $current = $Coro::current;
280 294
281 # register a hypothetical event handler 295=item cede
282 on_event_invoke sub { 296
283 # wake up sleeping coroutine 297"Cede" to other coros. This function puts the current coro into
284 $current->ready; 298the ready queue and calls C<schedule>, which has the effect of giving
285 undef $current; 299up the current "timeslice" to other coros of the same or higher
300priority. Once your coro gets its turn again it will automatically be
301resumed.
302
303This function is often called C<yield> in other languages.
304
305=item Coro::cede_notself
306
307Works like cede, but is not exported by default and will cede to I<any>
308coro, regardless of priority. This is useful sometimes to ensure
309progress is made.
310
311=item terminate [arg...]
312
313Terminates the current coro with the given status values (see L<cancel>).
314
315=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
316
317These function install enter and leave winders in the current scope. The
318enter block will be executed when on_enter is called and whenever the
319current coro is re-entered by the scheduler, while the leave block is
320executed whenever the current coro is blocked by the scheduler, and
321also when the containing scope is exited (by whatever means, be it exit,
322die, last etc.).
323
324I<Neither invoking the scheduler, nor exceptions, are allowed within those
325BLOCKs>. That means: do not even think about calling C<die> without an
326eval, and do not even think of entering the scheduler in any way.
327
328Since both BLOCKs are tied to the current scope, they will automatically
329be removed when the current scope exits.
330
331These functions implement the same concept as C<dynamic-wind> in scheme
332does, and are useful when you want to localise some resource to a specific
333coro.
334
335They slow down thread switching considerably for coros that use them
336(about 40% for a BLOCK with a single assignment, so thread switching is
337still reasonably fast if the handlers are fast).
338
339These functions are best understood by an example: The following function
340will change the current timezone to "Antarctica/South_Pole", which
341requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
342which remember/change the current timezone and restore the previous
343value, respectively, the timezone is only changed for the coro that
344installed those handlers.
345
346 use POSIX qw(tzset);
347
348 async {
349 my $old_tz; # store outside TZ value here
350
351 Coro::on_enter {
352 $old_tz = $ENV{TZ}; # remember the old value
353
354 $ENV{TZ} = "Antarctica/South_Pole";
355 tzset; # enable new value
286 }; 356 };
287 357
288 # call schedule until event occurred. 358 Coro::on_leave {
289 # in case we are woken up for other reasons 359 $ENV{TZ} = $old_tz;
290 # (current still defined), loop. 360 tzset; # restore old value
291 Coro::schedule while $current; 361 };
362
363 # at this place, the timezone is Antarctica/South_Pole,
364 # without disturbing the TZ of any other coro.
292 } 365 };
293 366
294=item cede 367This can be used to localise about any resource (locale, uid, current
368working directory etc.) to a block, despite the existance of other
369coros.
295 370
296"Cede" to other coroutines. This function puts the current coroutine into the 371Another interesting example implements time-sliced multitasking using
297ready queue and calls C<schedule>, which has the effect of giving up the 372interval timers (this could obviously be optimised, but does the job):
298current "timeslice" to other coroutines of the same or higher priority.
299 373
300Returns true if at least one coroutine switch has happened. 374 # "timeslice" the given block
375 sub timeslice(&) {
376 use Time::HiRes ();
301 377
302=item Coro::cede_notself 378 Coro::on_enter {
379 # on entering the thread, we set an VTALRM handler to cede
380 $SIG{VTALRM} = sub { cede };
381 # and then start the interval timer
382 Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
383 };
384 Coro::on_leave {
385 # on leaving the thread, we stop the interval timer again
386 Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
387 };
303 388
304Works like cede, but is not exported by default and will cede to any 389 &{+shift};
305coroutine, regardless of priority, once. 390 }
306 391
307Returns true if at least one coroutine switch has happened. 392 # use like this:
393 timeslice {
394 # The following is an endless loop that would normally
395 # monopolise the process. Since it runs in a timesliced
396 # environment, it will regularly cede to other threads.
397 while () { }
398 };
308 399
309=item terminate [arg...]
310
311Terminates the current coroutine with the given status values (see L<cancel>).
312 400
313=item killall 401=item killall
314 402
315Kills/terminates/cancels all coroutines except the currently running 403Kills/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.
318 404
319=cut 405Note that while this will try to free some of the main interpreter
406resources if the calling coro isn't the main coro, but one
407cannot free all of them, so if a coro that is not the main coro
408calls this function, there will be some one-time resource leak.
320 409
321sub terminate { 410=cut
322 $current->cancel (@_);
323}
324 411
325sub killall { 412sub killall {
326 for (Coro::State::list) { 413 for (Coro::State::list) {
327 $_->cancel 414 $_->cancel
328 if $_ != $current && UNIVERSAL::isa $_, "Coro"; 415 if $_ != $current && UNIVERSAL::isa $_, "Coro";
329 } 416 }
330} 417}
331 418
332=back 419=back
333 420
334# dynamic methods
335
336=head2 COROUTINE METHODS 421=head1 CORO OBJECT METHODS
337 422
338These are the methods you can call on coroutine objects. 423These are the methods you can call on coro objects (or to create
424them).
339 425
340=over 4 426=over 4
341 427
342=item new Coro \&sub [, @args...] 428=item new Coro \&sub [, @args...]
343 429
344Create a new coroutine and return it. When the sub returns the coroutine 430Create a new coro and return it. When the sub returns, the coro
345automatically terminates as if C<terminate> with the returned values were 431automatically 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 432called. To make the coro run you must first put it into the ready
347by calling the ready method. 433queue by calling the ready method.
348 434
349See C<async> for additional discussion. 435See C<async> and C<Coro::State::new> for additional info about the
436coro environment.
350 437
351=cut 438=cut
352 439
353sub _run_coro { 440sub _coro_run {
354 terminate &{+shift}; 441 terminate &{+shift};
355} 442}
356 443
357sub new {
358 my $class = shift;
359
360 $class->SUPER::new (\&_run_coro, @_)
361}
362
363=item $success = $coroutine->ready 444=item $success = $coro->ready
364 445
365Put the given coroutine into the ready queue (according to it's priority) 446Put 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 447queue for each priority) and return true. If the coro is already in
367and return false. 448the ready queue, do nothing and return false.
368 449
450This ensures that the scheduler will resume this coro automatically
451once all the coro of higher priority and all coro of the same
452priority that were put into the ready queue earlier have been resumed.
453
454=item $coro->suspend
455
456Suspends the specified coro. A suspended coro works just like any other
457coro, except that the scheduler will not select a suspended coro for
458execution.
459
460Suspending a coro can be useful when you want to keep the coro from
461running, but you don't want to destroy it, or when you want to temporarily
462freeze a coro (e.g. for debugging) to resume it later.
463
464A scenario for the former would be to suspend all (other) coros after a
465fork and keep them alive, so their destructors aren't called, but new
466coros can be created.
467
468=item $coro->resume
469
470If the specified coro was suspended, it will be resumed. Note that when
471the coro was in the ready queue when it was suspended, it might have been
472unreadied by the scheduler, so an activation might have been lost.
473
474To avoid this, it is best to put a suspended coro into the ready queue
475unconditionally, as every synchronisation mechanism must protect itself
476against spurious wakeups, and the one in the Coro family certainly do
477that.
478
369=item $is_ready = $coroutine->is_ready 479=item $is_ready = $coro->is_ready
370 480
371Return wether the coroutine is currently the ready queue or not, 481Returns true iff the Coro object is in the ready queue. Unless the Coro
482object gets destroyed, it will eventually be scheduled by the scheduler.
372 483
484=item $is_running = $coro->is_running
485
486Returns true iff the Coro object is currently running. Only one Coro object
487can ever be in the running state (but it currently is possible to have
488multiple running Coro::States).
489
490=item $is_suspended = $coro->is_suspended
491
492Returns true iff this Coro object has been suspended. Suspended Coros will
493not ever be scheduled.
494
373=item $coroutine->cancel (arg...) 495=item $coro->cancel (arg...)
374 496
375Terminates the given coroutine and makes it return the given arguments as 497Terminates the given Coro and makes it return the given arguments as
376status (default: the empty list). Never returns if the coroutine is the 498status (default: the empty list). Never returns if the Coro is the
377current coroutine. 499current Coro.
378 500
379=cut 501=cut
380 502
381sub cancel { 503sub cancel {
382 my $self = shift; 504 my $self = shift;
383 $self->{_status} = [@_];
384 505
385 if ($current == $self) { 506 if ($current == $self) {
386 push @destroy, $self; 507 terminate @_;
387 $manager->ready;
388 &schedule while 1;
389 } else { 508 } else {
390 $self->_cancel; 509 $self->{_status} = [@_];
510 Coro::State::cancel $self;
391 } 511 }
392} 512}
393 513
514=item $coro->schedule_to
515
516Puts the current coro to sleep (like C<Coro::schedule>), but instead
517of continuing with the next coro from the ready queue, always switch to
518the given coro object (regardless of priority etc.). The readyness
519state of that coro isn't changed.
520
521This is an advanced method for special cases - I'd love to hear about any
522uses for this one.
523
524=item $coro->cede_to
525
526Like C<schedule_to>, but puts the current coro into the ready
527queue. This has the effect of temporarily switching to the given
528coro, and continuing some time later.
529
530This is an advanced method for special cases - I'd love to hear about any
531uses for this one.
532
533=item $coro->throw ([$scalar])
534
535If C<$throw> is specified and defined, it will be thrown as an exception
536inside the coro at the next convenient point in time. Otherwise
537clears the exception object.
538
539Coro will check for the exception each time a schedule-like-function
540returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
541>>, C<< Coro::Handle->readable >> and so on. Most of these functions
542detect this case and return early in case an exception is pending.
543
544The exception object will be thrown "as is" with the specified scalar in
545C<$@>, i.e. if it is a string, no line number or newline will be appended
546(unlike with C<die>).
547
548This can be used as a softer means than C<cancel> to ask a coro to
549end itself, although there is no guarantee that the exception will lead to
550termination, and if the exception isn't caught it might well end the whole
551program.
552
553You might also think of C<throw> as being the moral equivalent of
554C<kill>ing a coro with a signal (in this case, a scalar).
555
394=item $coroutine->join 556=item $coro->join
395 557
396Wait until the coroutine terminates and return any values given to the 558Wait until the coro terminates and return any values given to the
397C<terminate> or C<cancel> functions. C<join> can be called multiple times 559C<terminate> or C<cancel> functions. C<join> can be called concurrently
398from multiple coroutine. 560from multiple coro, and all will be resumed and given the status
561return once the C<$coro> terminates.
399 562
400=cut 563=cut
401 564
402sub join { 565sub join {
403 my $self = shift; 566 my $self = shift;
414 } 577 }
415 578
416 wantarray ? @{$self->{_status}} : $self->{_status}[0]; 579 wantarray ? @{$self->{_status}} : $self->{_status}[0];
417} 580}
418 581
419=item $coroutine->on_destroy (\&cb) 582=item $coro->on_destroy (\&cb)
420 583
421Registers a callback that is called when this coroutine gets destroyed, 584Registers a callback that is called when this coro gets destroyed,
422but before it is joined. The callback gets passed the terminate arguments, 585but before it is joined. The callback gets passed the terminate arguments,
423if any. 586if any, and I<must not> die, under any circumstances.
424 587
425=cut 588=cut
426 589
427sub on_destroy { 590sub on_destroy {
428 my ($self, $cb) = @_; 591 my ($self, $cb) = @_;
429 592
430 push @{ $self->{_on_destroy} }, $cb; 593 push @{ $self->{_on_destroy} }, $cb;
431} 594}
432 595
433=item $oldprio = $coroutine->prio ($newprio) 596=item $oldprio = $coro->prio ($newprio)
434 597
435Sets (or gets, if the argument is missing) the priority of the 598Sets (or gets, if the argument is missing) the priority of the
436coroutine. Higher priority coroutines get run before lower priority 599coro. Higher priority coro get run before lower priority
437coroutines. Priorities are small signed integers (currently -4 .. +3), 600coro. Priorities are small signed integers (currently -4 .. +3),
438that you can refer to using PRIO_xxx constants (use the import tag :prio 601that you can refer to using PRIO_xxx constants (use the import tag :prio
439to get then): 602to get then):
440 603
441 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 604 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
442 3 > 1 > 0 > -1 > -3 > -4 605 3 > 1 > 0 > -1 > -3 > -4
443 606
444 # set priority to HIGH 607 # set priority to HIGH
445 current->prio(PRIO_HIGH); 608 current->prio (PRIO_HIGH);
446 609
447The idle coroutine ($Coro::idle) always has a lower priority than any 610The idle coro ($Coro::idle) always has a lower priority than any
448existing coroutine. 611existing coro.
449 612
450Changing the priority of the current coroutine will take effect immediately, 613Changing the priority of the current coro will take effect immediately,
451but changing the priority of coroutines in the ready queue (but not 614but changing the priority of coro in the ready queue (but not
452running) will only take effect after the next schedule (of that 615running) will only take effect after the next schedule (of that
453coroutine). This is a bug that will be fixed in some future version. 616coro). This is a bug that will be fixed in some future version.
454 617
455=item $newprio = $coroutine->nice ($change) 618=item $newprio = $coro->nice ($change)
456 619
457Similar to C<prio>, but subtract the given value from the priority (i.e. 620Similar to C<prio>, but subtract the given value from the priority (i.e.
458higher values mean lower priority, just as in unix). 621higher values mean lower priority, just as in unix).
459 622
460=item $olddesc = $coroutine->desc ($newdesc) 623=item $olddesc = $coro->desc ($newdesc)
461 624
462Sets (or gets in case the argument is missing) the description for this 625Sets (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. 626coro. This is just a free-form string you can associate with a
627coro.
464 628
465This method simply sets the C<< $coroutine->{desc} >> member to the given string. You 629This method simply sets the C<< $coro->{desc} >> member to the given
466can modify this member directly if you wish. 630string. You can modify this member directly if you wish.
467 631
468=cut 632=cut
469 633
470sub desc { 634sub desc {
471 my $old = $_[0]{desc}; 635 my $old = $_[0]{desc};
472 $_[0]{desc} = $_[1] if @_ > 1; 636 $_[0]{desc} = $_[1] if @_ > 1;
473 $old; 637 $old;
474} 638}
475 639
640sub transfer {
641 require Carp;
642 Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
643}
644
476=back 645=back
477 646
478=head2 GLOBAL FUNCTIONS 647=head1 GLOBAL FUNCTIONS
479 648
480=over 4 649=over 4
481 650
482=item Coro::nready 651=item Coro::nready
483 652
484Returns the number of coroutines that are currently in the ready state, 653Returns 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 654i.e. that can be switched to by calling C<schedule> directory or
655indirectly. 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, 656currently 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 657would cause a deadlock unless there is an idle handler that wakes up some
488that wakes up some coroutines. 658coro.
489 659
490=item my $guard = Coro::guard { ... } 660=item my $guard = Coro::guard { ... }
491 661
492This creates and returns a guard object. Nothing happens until the object 662This function still exists, but is deprecated. Please use the
493gets destroyed, in which case the codeblock given as argument will be 663C<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.
498 664
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 665=cut
510 666
511sub guard(&) { 667BEGIN { *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
523 668
524=item unblock_sub { ... } 669=item unblock_sub { ... }
525 670
526This utility function takes a BLOCK or code reference and "unblocks" it, 671This utility function takes a BLOCK or code reference and "unblocks" it,
527returning the new coderef. This means that the new coderef will return 672returning a new coderef. Unblocking means that calling the new coderef
528immediately without blocking, returning nothing, while the original code 673will return immediately without blocking, returning nothing, while the
529ref will be called (with parameters) from within its own coroutine. 674original code ref will be called (with parameters) from within another
675coro.
530 676
531The reason this function exists is that many event libraries (such as the 677The reason this function exists is that many event libraries (such as the
532venerable L<Event|Event> module) are not coroutine-safe (a weaker form 678venerable L<Event|Event> module) are not thread-safe (a weaker form
533of thread-safety). This means you must not block within event callbacks, 679of reentrancy). This means you must not block within event callbacks,
534otherwise you might suffer from crashes or worse. 680otherwise you might suffer from crashes or worse. The only event library
681currently known that is safe to use without C<unblock_sub> is L<EV>.
535 682
536This function allows your callbacks to block by executing them in another 683This function allows your callbacks to block by executing them in another
537coroutine where it is safe to block. One example where blocking is handy 684coro 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 685is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
539disk. 686disk, for example.
540 687
541In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when 688In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
542creating event callbacks that want to block. 689creating event callbacks that want to block.
690
691If your handler does not plan to block (e.g. simply sends a message to
692another coro, or puts some other coro into the ready queue), there is
693no reason to use C<unblock_sub>.
694
695Note that you also need to use C<unblock_sub> for any other callbacks that
696are indirectly executed by any C-based event loop. For example, when you
697use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
698provides callbacks that are the result of some event callback, then you
699must not block either, or use C<unblock_sub>.
543 700
544=cut 701=cut
545 702
546our @unblock_queue; 703our @unblock_queue;
547 704
550# return immediately and can be reused) and because we cannot cede 707# return immediately and can be reused) and because we cannot cede
551# inside an event callback. 708# inside an event callback.
552our $unblock_scheduler = new Coro sub { 709our $unblock_scheduler = new Coro sub {
553 while () { 710 while () {
554 while (my $cb = pop @unblock_queue) { 711 while (my $cb = pop @unblock_queue) {
555 # this is an inlined copy of async_pool 712 &async_pool (@$cb);
556 my $coro = (pop @async_pool) || new Coro \&pool_handler;
557 713
558 $coro->{_invoke} = $cb;
559 $coro->ready;
560 cede; # for short-lived callbacks, this reduces pressure on the coro pool 714 # for short-lived callbacks, this reduces pressure on the coro pool
715 # as the chance is very high that the async_poll coro will be back
716 # in the idle state when cede returns
717 cede;
561 } 718 }
562 schedule; # sleep well 719 schedule; # sleep well
563 } 720 }
564}; 721};
565$unblock_scheduler->desc ("[unblock_sub scheduler]"); 722$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
566 723
567sub unblock_sub(&) { 724sub unblock_sub(&) {
568 my $cb = shift; 725 my $cb = shift;
569 726
570 sub { 727 sub {
571 unshift @unblock_queue, [$cb, @_]; 728 unshift @unblock_queue, [$cb, @_];
572 $unblock_scheduler->ready; 729 $unblock_scheduler->ready;
573 } 730 }
574} 731}
575 732
733=item $cb = Coro::rouse_cb
734
735Create and return a "rouse callback". That's a code reference that,
736when called, will remember a copy of its arguments and notify the owner
737coro of the callback.
738
739See the next function.
740
741=item @args = Coro::rouse_wait [$cb]
742
743Wait for the specified rouse callback (or the last one that was created in
744this coro).
745
746As soon as the callback is invoked (or when the callback was invoked
747before C<rouse_wait>), it will return the arguments originally passed to
748the rouse callback. In scalar context, that means you get the I<last>
749argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
750statement at the end.
751
752See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
753
576=back 754=back
577 755
578=cut 756=cut
579 757
5801; 7581;
581 759
760=head1 HOW TO WAIT FOR A CALLBACK
761
762It is very common for a coro to wait for some callback to be
763called. This occurs naturally when you use coro in an otherwise
764event-based program, or when you use event-based libraries.
765
766These typically register a callback for some event, and call that callback
767when the event occured. In a coro, however, you typically want to
768just wait for the event, simplyifying things.
769
770For example C<< AnyEvent->child >> registers a callback to be called when
771a specific child has exited:
772
773 my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
774
775But from within a coro, you often just want to write this:
776
777 my $status = wait_for_child $pid;
778
779Coro offers two functions specifically designed to make this easy,
780C<Coro::rouse_cb> and C<Coro::rouse_wait>.
781
782The first function, C<rouse_cb>, generates and returns a callback that,
783when invoked, will save its arguments and notify the coro that
784created the callback.
785
786The second function, C<rouse_wait>, waits for the callback to be called
787(by calling C<schedule> to go to sleep) and returns the arguments
788originally passed to the callback.
789
790Using these functions, it becomes easy to write the C<wait_for_child>
791function mentioned above:
792
793 sub wait_for_child($) {
794 my ($pid) = @_;
795
796 my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
797
798 my ($rpid, $rstatus) = Coro::rouse_wait;
799 $rstatus
800 }
801
802In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
803you can roll your own, using C<schedule>:
804
805 sub wait_for_child($) {
806 my ($pid) = @_;
807
808 # store the current coro in $current,
809 # and provide result variables for the closure passed to ->child
810 my $current = $Coro::current;
811 my ($done, $rstatus);
812
813 # pass a closure to ->child
814 my $watcher = AnyEvent->child (pid => $pid, cb => sub {
815 $rstatus = $_[1]; # remember rstatus
816 $done = 1; # mark $rstatus as valud
817 });
818
819 # wait until the closure has been called
820 schedule while !$done;
821
822 $rstatus
823 }
824
825
582=head1 BUGS/LIMITATIONS 826=head1 BUGS/LIMITATIONS
583 827
584 - you must make very sure that no coro is still active on global 828=over 4
585 destruction. very bad things might happen otherwise (usually segfaults).
586 829
830=item fork with pthread backend
831
832When Coro is compiled using the pthread backend (which isn't recommended
833but required on many BSDs as their libcs are completely broken), then
834coro will not survive a fork. There is no known workaround except to
835fix your libc and use a saner backend.
836
837=item perl process emulation ("threads")
838
587 - this module is not thread-safe. You should only ever use this module 839This 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 840module from the first thread (this requirement might be removed in the
589 to allow per-thread schedulers, but Coro::State does not yet allow 841future to allow per-thread schedulers, but Coro::State does not yet allow
590 this). 842this). I recommend disabling thread support and using processes, as having
843the windows process emulation enabled under unix roughly halves perl
844performance, even when not used.
845
846=item coro switching is not signal safe
847
848You must not switch to another coro from within a signal handler
849(only relevant with %SIG - most event libraries provide safe signals).
850
851That means you I<MUST NOT> call any function that might "block" the
852current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
853anything that calls those. Everything else, including calling C<ready>,
854works.
855
856=back
857
858
859=head1 WINDOWS PROCESS EMULATION
860
861A great many people seem to be confused about ithreads (for example, Chip
862Salzenberg called me unintelligent, incapable, stupid and gullible,
863while in the same mail making rather confused statements about perl
864ithreads (for example, that memory or files would be shared), showing his
865lack of understanding of this area - if it is hard to understand for Chip,
866it is probably not obvious to everybody).
867
868What follows is an ultra-condensed version of my talk about threads in
869scripting languages given onthe perl workshop 2009:
870
871The so-called "ithreads" were originally implemented for two reasons:
872first, to (badly) emulate unix processes on native win32 perls, and
873secondly, to replace the older, real thread model ("5.005-threads").
874
875It does that by using threads instead of OS processes. The difference
876between processes and threads is that threads share memory (and other
877state, such as files) between threads within a single process, while
878processes do not share anything (at least not semantically). That
879means that modifications done by one thread are seen by others, while
880modifications by one process are not seen by other processes.
881
882The "ithreads" work exactly like that: when creating a new ithreads
883process, all state is copied (memory is copied physically, files and code
884is copied logically). Afterwards, it isolates all modifications. On UNIX,
885the same behaviour can be achieved by using operating system processes,
886except that UNIX typically uses hardware built into the system to do this
887efficiently, while the windows process emulation emulates this hardware in
888software (rather efficiently, but of course it is still much slower than
889dedicated hardware).
890
891As mentioned before, loading code, modifying code, modifying data
892structures and so on is only visible in the ithreads process doing the
893modification, not in other ithread processes within the same OS process.
894
895This is why "ithreads" do not implement threads for perl at all, only
896processes. What makes it so bad is that on non-windows platforms, you can
897actually take advantage of custom hardware for this purpose (as evidenced
898by the forks module, which gives you the (i-) threads API, just much
899faster).
900
901Sharing data is in the i-threads model is done by transfering data
902structures between threads using copying semantics, which is very slow -
903shared data simply does not exist. Benchmarks using i-threads which are
904communication-intensive show extremely bad behaviour with i-threads (in
905fact, so bad that Coro, which cannot take direct advantage of multiple
906CPUs, is often orders of magnitude faster because it shares data using
907real threads, refer to my talk for details).
908
909As summary, i-threads *use* threads to implement processes, while
910the compatible forks module *uses* processes to emulate, uhm,
911processes. I-threads slow down every perl program when enabled, and
912outside of windows, serve no (or little) practical purpose, but
913disadvantages every single-threaded Perl program.
914
915This is the reason that I try to avoid the name "ithreads", as it is
916misleading as it implies that it implements some kind of thread model for
917perl, and prefer the name "windows process emulation", which describes the
918actual use and behaviour of it much better.
591 919
592=head1 SEE ALSO 920=head1 SEE ALSO
593 921
922Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
923
924Debugging: L<Coro::Debug>.
925
594Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>. 926Support/Utility: L<Coro::Specific>, L<Coro::Util>.
595 927
596Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. 928Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
929L<Coro::SemaphoreSet>, L<Coro::RWLock>.
597 930
598Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>. 931I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
599 932
600Embedding: L<Coro:MakeMaker> 933Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
934a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
935L<Coro::Select>.
936
937XS API: L<Coro::MakeMaker>.
938
939Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
601 940
602=head1 AUTHOR 941=head1 AUTHOR
603 942
604 Marc Lehmann <schmorp@schmorp.de> 943 Marc Lehmann <schmorp@schmorp.de>
605 http://home.schmorp.de/ 944 http://home.schmorp.de/

Diff Legend

Removed lines
+ Added lines
< Changed lines
> Changed lines