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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
… …
11 print "2\n"; 11 print "2\n";
12 cede; # yield back to main 12 cede; # yield back to main
13 print "4\n"; 13 print "4\n";
14 }; 14 };
15 print "1\n"; 15 print "1\n";
16 cede; # yield to coroutine 16 cede; # yield to coro
17 print "3\n"; 17 print "3\n";
18 cede; # and again 18 cede; # and again
19 19
20 # use locking 20 # use locking
21 use Coro::Semaphore; 21 use Coro::Semaphore;
… …
26 $locked = 1; 26 $locked = 1;
27 $lock->up; 27 $lock->up;
28 28
29=head1 DESCRIPTION 29=head1 DESCRIPTION
30 30
31This module collection manages coroutines. Coroutines are similar to 31For a tutorial-style introduction, please read the L<Coro::Intro>
32threads but don't (in general) run in parallel at the same time even 32manpage. This manpage mainly contains reference information.
33on SMP machines. The specific flavor of coroutine used in this module
34also guarantees you that it will not switch between coroutines unless
35necessary, at easily-identified points in your program, so locking and
36parallel access are rarely an issue, making coroutine programming much
37safer and easier than threads programming.
38 33
39Unlike a normal perl program, however, coroutines allow you to have 34This module collection manages continuations in general, most often in
40multiple running interpreters that share data, which is especially useful 35the form of cooperative threads (also called coros, or simply "coro"
41to code pseudo-parallel processes and for event-based programming, such as 36in the documentation). They are similar to kernel threads but don't (in
42multiple HTTP-GET requests running concurrently. See L<Coro::AnyEvent> to 37general) run in parallel at the same time even on SMP machines. The
43learn more. 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.
44 43
45Coroutines are also useful because Perl has no support for threads (the so 44Unlike the so-called "Perl threads" (which are not actually real threads
46called "threads" that perl offers are nothing more than the (bad) process 45but only the windows process emulation ported to unix, and as such act
47emulation coming from the Windows platform: On standard operating systems 46as processes), Coro provides a full shared address space, which makes
48they serve no purpose whatsoever, except by making your programs slow and 47communication between threads very easy. And Coro's threads are fast,
49making them use a lot of memory. Best disable them when building perl, or 48too: disabling the Windows process emulation code in your perl and using
50aks your software vendor/distributor to do it for you). 49Coro can easily result in a two to four times speed increase for your
50programs. A parallel matrix multiplication benchmark runs over 300 times
51faster on a single core than perl's pseudo-threads on a quad core using
52all four cores.
51 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
52In this module, coroutines are defined as "callchain + lexical variables + 60In this module, a thread is defined as "callchain + lexical variables +
53@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain, 61some package variables + C stack), that is, a thread has its own callchain,
54its 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
55variables (see L<Coro::State> for more configuration). 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.
56 67
57=cut 68=cut
58 69
59package Coro; 70package Coro;
60 71
61use strict qw(vars subs); 72use strict qw(vars subs);
62no warnings "uninitialized"; 73no warnings "uninitialized";
63 74
75use Guard ();
76
64use Coro::State; 77use Coro::State;
65 78
66use base qw(Coro::State Exporter); 79use base qw(Coro::State Exporter);
67 80
68our $idle; # idle handler 81our $idle; # idle handler
69our $main; # main coroutine 82our $main; # main coro
70our $current; # current coroutine 83our $current; # current coro
71 84
72our $VERSION = 5.0; 85our $VERSION = 5.162;
73 86
74our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); 87our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
75our %EXPORT_TAGS = ( 88our %EXPORT_TAGS = (
76 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 89 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
77); 90);
78our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); 91our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
79 92
93=head1 GLOBAL VARIABLES
94
80=over 4 95=over 4
81 96
82=item $Coro::main 97=item $Coro::main
83 98
84This variable stores the coroutine object that represents the main 99This variable stores the Coro object that represents the main
85program. While you cna C<ready> it and do most other things you can do to 100program. While you cna C<ready> it and do most other things you can do to
86coroutines, it is mainly useful to compare again C<$Coro::current>, to see 101coro, it is mainly useful to compare again C<$Coro::current>, to see
87whether you are running in the main program or not. 102whether you are running in the main program or not.
88 103
89=cut 104=cut
90 105
91# $main is now being initialised by Coro::State 106# $main is now being initialised by Coro::State
92 107
93=item $Coro::current 108=item $Coro::current
94 109
95The coroutine object representing the current coroutine (the last 110The Coro object representing the current coro (the last
96coroutine that the Coro scheduler switched to). The initial value is 111coro that the Coro scheduler switched to). The initial value is
97C<$Coro::main> (of course). 112C<$Coro::main> (of course).
98 113
99This variable is B<strictly> I<read-only>. You can take copies of the 114This variable is B<strictly> I<read-only>. You can take copies of the
100value stored in it and use it as any other coroutine object, but you must 115value stored in it and use it as any other Coro object, but you must
101not otherwise modify the variable itself. 116not otherwise modify the variable itself.
102 117
103=cut 118=cut
104 119
105sub current() { $current } # [DEPRECATED] 120sub current() { $current } # [DEPRECATED]
106 121
107=item $Coro::idle 122=item $Coro::idle
108 123
109This variable is mainly useful to integrate Coro into event loops. It is 124This variable is mainly useful to integrate Coro into event loops. It is
110usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is 125usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
111pretty low-level functionality. 126pretty low-level functionality.
112 127
113This variable stores a callback that is called whenever the scheduler 128This variable stores either a Coro object or a callback.
129
130If it is a callback, the it is called whenever the scheduler finds no
114finds no ready coroutines to run. The default implementation prints 131ready coros to run. The default implementation prints "FATAL:
115"FATAL: deadlock detected" and exits, because the program has no other way 132deadlock detected" and exits, because the program has no other way to
116to continue. 133continue.
117 134
135If it is a coro object, then this object will be readied (without
136invoking any ready hooks, however) when the scheduler finds no other ready
137coros to run.
138
118This hook is overwritten by modules such as C<Coro::Timer> and 139This hook is overwritten by modules such as C<Coro::EV> and
119C<Coro::AnyEvent> to wait on an external event that hopefully wake up a 140C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
120coroutine so the scheduler can run it. 141coro so the scheduler can run it.
121 142
122Note that the callback I<must not>, under any circumstances, block 143Note that the callback I<must not>, under any circumstances, block
123the current coroutine. Normally, this is achieved by having an "idle 144the current coro. Normally, this is achieved by having an "idle
124coroutine" that calls the event loop and then blocks again, and then 145coro" that calls the event loop and then blocks again, and then
125readying that coroutine in the idle handler. 146readying that coro in the idle handler, or by simply placing the idle
147coro in this variable.
126 148
127See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this 149See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
128technique. 150technique.
129 151
130Please note that if your callback recursively invokes perl (e.g. for event 152Please note that if your callback recursively invokes perl (e.g. for event
… …
135$idle = sub { 157$idle = sub {
136 require Carp; 158 require Carp;
137 Carp::croak ("FATAL: deadlock detected"); 159 Carp::croak ("FATAL: deadlock detected");
138}; 160};
139 161
140sub _cancel {
141 my ($self) = @_;
142
143 # free coroutine data and mark as destructed
144 $self->_destroy
145 or return;
146
147 # call all destruction callbacks
148 $_->(@{$self->{_status}})
149 for @{ delete $self->{_on_destroy} || [] };
150}
151
152# this coroutine is necessary because a coroutine 162# this coro is necessary because a coro
153# cannot destroy itself. 163# cannot destroy itself.
154our @destroy; 164our @destroy;
155our $manager; 165our $manager;
156 166
157$manager = new Coro sub { 167$manager = new Coro sub {
158 while () { 168 while () {
159 (shift @destroy)->_cancel 169 Coro::State::cancel shift @destroy
160 while @destroy; 170 while @destroy;
161 171
162 &schedule; 172 &schedule;
163 } 173 }
164}; 174};
165$manager->{desc} = "[coro manager]"; 175$manager->{desc} = "[coro manager]";
166$manager->prio (PRIO_MAX); 176$manager->prio (PRIO_MAX);
167 177
168=back 178=back
169 179
170=head2 SIMPLE COROUTINE CREATION 180=head1 SIMPLE CORO CREATION
171 181
172=over 4 182=over 4
173 183
174=item async { ... } [@args...] 184=item async { ... } [@args...]
175 185
176Create a new coroutine and return it's coroutine object (usually 186Create a new coro and return its Coro object (usually
177unused). The coroutine will be put into the ready queue, so 187unused). The coro will be put into the ready queue, so
178it will start running automatically on the next scheduler run. 188it will start running automatically on the next scheduler run.
179 189
180The first argument is a codeblock/closure that should be executed in the 190The first argument is a codeblock/closure that should be executed in the
181coroutine. When it returns argument returns the coroutine is automatically 191coro. When it returns argument returns the coro is automatically
182terminated. 192terminated.
183 193
184The remaining arguments are passed as arguments to the closure. 194The remaining arguments are passed as arguments to the closure.
185 195
186See the C<Coro::State::new> constructor for info about the coroutine 196See the C<Coro::State::new> constructor for info about the coro
187environment in which coroutines are executed. 197environment in which coro are executed.
188 198
189Calling 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
190the coroutine. Likewise, when the coroutine dies, the program will exit, 200the coro. Likewise, when the coro dies, the program will exit,
191just as it would in the main program. 201just as it would in the main program.
192 202
193If you do not want that, you can provide a default C<die> handler, or 203If you do not want that, you can provide a default C<die> handler, or
194simply avoid dieing (by use of C<eval>). 204simply avoid dieing (by use of C<eval>).
195 205
196Example: Create a new coroutine that just prints its arguments. 206Example: Create a new coro that just prints its arguments.
197 207
198 async { 208 async {
199 print "@_\n"; 209 print "@_\n";
200 } 1,2,3,4; 210 } 1,2,3,4;
201 211
202=cut
203
204sub async(&@) {
205 my $coro = new Coro @_;
206 $coro->ready;
207 $coro
208}
209
210=item async_pool { ... } [@args...] 212=item async_pool { ... } [@args...]
211 213
212Similar 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
213terminate or join on it (although you are allowed to), and you get a 215terminate or join on it (although you are allowed to), and you get a
214coroutine that might have executed other code already (which can be good 216coro that might have executed other code already (which can be good
215or bad :). 217or bad :).
216 218
217On the plus side, this function is faster than creating (and destroying) 219On the plus side, this function is about twice as fast as creating (and
218a completly new coroutine, so if you need a lot of generic coroutines in 220destroying) a completely new coro, so if you need a lot of generic
219quick successsion, use C<async_pool>, not C<async>. 221coros in quick successsion, use C<async_pool>, not C<async>.
220 222
221The code 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
222issued in case of an exception instead of terminating the program, as 224issued in case of an exception instead of terminating the program, as
223C<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>
224will 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,
225which somehow defeats the purpose of pooling (but is fine in the 227which somehow defeats the purpose of pooling (but is fine in the
226exceptional case). 228exceptional case).
227 229
228The priority will be reset to C<0> after each run, tracing will be 230The priority will be reset to C<0> after each run, tracing will be
229disabled, the description will be reset and the default output filehandle 231disabled, the description will be reset and the default output filehandle
230gets restored, so you can change all these. Otherwise the coroutine will 232gets restored, so you can change all these. Otherwise the coro will
231be re-used "as-is": most notably if you change other per-coroutine global 233be re-used "as-is": most notably if you change other per-coro global
232stuff such as C<$/> you I<must needs> revert that change, which is most 234stuff such as C<$/> you I<must needs> revert that change, which is most
233simply done by using local as in: C<< local $/ >>. 235simply done by using local as in: C<< local $/ >>.
234 236
235The idle pool size is limited to C<8> idle coroutines (this can be 237The idle pool size is limited to C<8> idle coros (this can be
236adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle 238adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
237coros as required. 239coros as required.
238 240
239If you are concerned about pooled coroutines growing a lot because a 241If you are concerned about pooled coros growing a lot because a
240single 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
241{ 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
242addition 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
243(adjustable via $Coro::POOL_RSS) it will also be destroyed. 245(adjustable via $Coro::POOL_RSS) it will also be destroyed.
244 246
245=cut 247=cut
246 248
247our $POOL_SIZE = 8; 249our $POOL_SIZE = 8;
248our $POOL_RSS = 16 * 1024; 250our $POOL_RSS = 32 * 1024;
249our @async_pool; 251our @async_pool;
250 252
251sub pool_handler { 253sub pool_handler {
252 while () { 254 while () {
253 eval { 255 eval {
… …
258 } 260 }
259} 261}
260 262
261=back 263=back
262 264
263=head2 STATIC METHODS 265=head1 STATIC METHODS
264 266
265Static methods are actually functions that operate on the current coroutine. 267Static methods are actually functions that implicitly operate on the
268current coro.
266 269
267=over 4 270=over 4
268 271
269=item schedule 272=item schedule
270 273
271Calls the scheduler. The scheduler will find the next coroutine that is 274Calls the scheduler. The scheduler will find the next coro that is
272to be run from the ready queue and switches to it. The next coroutine 275to be run from the ready queue and switches to it. The next coro
273to be run is simply the one with the highest priority that is longest 276to be run is simply the one with the highest priority that is longest
274in its ready queue. If there is no coroutine ready, it will clal the 277in its ready queue. If there is no coro ready, it will clal the
275C<$Coro::idle> hook. 278C<$Coro::idle> hook.
276 279
277Please note that the current coroutine will I<not> be put into the ready 280Please note that the current coro will I<not> be put into the ready
278queue, so calling this function usually means you will never be called 281queue, so calling this function usually means you will never be called
279again unless something else (e.g. an event handler) calls C<< ->ready >>, 282again unless something else (e.g. an event handler) calls C<< ->ready >>,
280thus waking you up. 283thus waking you up.
281 284
282This makes C<schedule> I<the> generic method to use to block the current 285This makes C<schedule> I<the> generic method to use to block the current
283coroutine and wait for events: first you remember the current coroutine in 286coro and wait for events: first you remember the current coro in
284a variable, then arrange for some callback of yours to call C<< ->ready 287a variable, then arrange for some callback of yours to call C<< ->ready
285>> on that once some event happens, and last you call C<schedule> to put 288>> on that once some event happens, and last you call C<schedule> to put
286yourself to sleep. Note that a lot of things can wake your coroutine up, 289yourself to sleep. Note that a lot of things can wake your coro up,
287so you need to check whether the event indeed happened, e.g. by storing the 290so you need to check whether the event indeed happened, e.g. by storing the
288status in a variable. 291status in a variable.
289 292
290See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks. 293See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
291 294
292=item cede 295=item cede
293 296
294"Cede" to other coroutines. This function puts the current coroutine into 297"Cede" to other coros. This function puts the current coro into
295the ready queue and calls C<schedule>, which has the effect of giving 298the ready queue and calls C<schedule>, which has the effect of giving
296up the current "timeslice" to other coroutines of the same or higher 299up the current "timeslice" to other coros of the same or higher
297priority. Once your coroutine gets its turn again it will automatically be 300priority. Once your coro gets its turn again it will automatically be
298resumed. 301resumed.
299 302
300This function is often called C<yield> in other languages. 303This function is often called C<yield> in other languages.
301 304
302=item Coro::cede_notself 305=item Coro::cede_notself
303 306
304Works like cede, but is not exported by default and will cede to I<any> 307Works like cede, but is not exported by default and will cede to I<any>
305coroutine, regardless of priority. This is useful sometimes to ensure 308coro, regardless of priority. This is useful sometimes to ensure
306progress is made. 309progress is made.
307 310
308=item terminate [arg...] 311=item terminate [arg...]
309 312
310Terminates the current coroutine with the given status values (see L<cancel>). 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
356 };
357
358 Coro::on_leave {
359 $ENV{TZ} = $old_tz;
360 tzset; # restore old value
361 };
362
363 # at this place, the timezone is Antarctica/South_Pole,
364 # without disturbing the TZ of any other coro.
365 };
366
367This can be used to localise about any resource (locale, uid, current
368working directory etc.) to a block, despite the existance of other
369coros.
370
371Another interesting example implements time-sliced multitasking using
372interval timers (this could obviously be optimised, but does the job):
373
374 # "timeslice" the given block
375 sub timeslice(&) {
376 use Time::HiRes ();
377
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 };
388
389 &{+shift};
390 }
391
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 };
399
311 400
312=item killall 401=item killall
313 402
314Kills/terminates/cancels all coroutines except the currently running 403Kills/terminates/cancels all coros except the currently running one.
315one. This is useful after a fork, either in the child or the parent, as
316usually only one of them should inherit the running coroutines.
317 404
318Note that while this will try to free some of the main programs resources, 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
319you cannot free all of them, so if a coroutine that is not the main 407cannot free all of them, so if a coro that is not the main coro
320program calls this function, there will be some one-time resource leak. 408calls this function, there will be some one-time resource leak.
321 409
322=cut 410=cut
323
324sub terminate {
325 $current->{_status} = [@_];
326 push @destroy, $current;
327 $manager->ready;
328 do { &schedule } while 1;
329}
330 411
331sub killall { 412sub killall {
332 for (Coro::State::list) { 413 for (Coro::State::list) {
333 $_->cancel 414 $_->cancel
334 if $_ != $current && UNIVERSAL::isa $_, "Coro"; 415 if $_ != $current && UNIVERSAL::isa $_, "Coro";
335 } 416 }
336} 417}
337 418
338=back 419=back
339 420
340=head2 COROUTINE METHODS 421=head1 CORO OBJECT METHODS
341 422
342These are the methods you can call on coroutine objects (or to create 423These are the methods you can call on coro objects (or to create
343them). 424them).
344 425
345=over 4 426=over 4
346 427
347=item new Coro \&sub [, @args...] 428=item new Coro \&sub [, @args...]
348 429
349Create 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
350automatically terminates as if C<terminate> with the returned values were 431automatically terminates as if C<terminate> with the returned values were
351called. To make the coroutine run you must first put it into the ready 432called. To make the coro run you must first put it into the ready
352queue by calling the ready method. 433queue by calling the ready method.
353 434
354See C<async> and C<Coro::State::new> for additional info about the 435See C<async> and C<Coro::State::new> for additional info about the
355coroutine environment. 436coro environment.
356 437
357=cut 438=cut
358 439
359sub _terminate { 440sub _coro_run {
360 terminate &{+shift}; 441 terminate &{+shift};
361} 442}
362 443
363=item $success = $coroutine->ready 444=item $success = $coro->ready
364 445
365Put the given coroutine into the end of its ready queue (there is one 446Put the given coro into the end of its ready queue (there is one
366queue for each priority) and return true. If the coroutine is already in 447queue for each priority) and return true. If the coro is already in
367the ready queue, do nothing and return false. 448the ready queue, do nothing and return false.
368 449
369This ensures that the scheduler will resume this coroutine automatically 450This ensures that the scheduler will resume this coro automatically
370once all the coroutines of higher priority and all coroutines of the same 451once all the coro of higher priority and all coro of the same
371priority that were put into the ready queue earlier have been resumed. 452priority that were put into the ready queue earlier have been resumed.
372 453
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
373=item $is_ready = $coroutine->is_ready 479=item $is_ready = $coro->is_ready
374 480
375Return whether 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.
376 483
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
377=item $coroutine->cancel (arg...) 495=item $coro->cancel (arg...)
378 496
379Terminates the given coroutine and makes it return the given arguments as 497Terminates the given Coro and makes it return the given arguments as
380status (default: the empty list). Never returns if the coroutine is the 498status (default: the empty list). Never returns if the Coro is the
381current coroutine. 499current Coro.
382 500
383=cut 501=cut
384 502
385sub cancel { 503sub cancel {
386 my $self = shift; 504 my $self = shift;
387 505
388 if ($current == $self) { 506 if ($current == $self) {
389 terminate @_; 507 terminate @_;
390 } else { 508 } else {
391 $self->{_status} = [@_]; 509 $self->{_status} = [@_];
392 $self->_cancel; 510 Coro::State::cancel $self;
393 } 511 }
394} 512}
395 513
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
396=item $coroutine->throw ([$scalar]) 533=item $coro->throw ([$scalar])
397 534
398If C<$throw> is specified and defined, it will be thrown as an exception 535If C<$throw> is specified and defined, it will be thrown as an exception
399inside the coroutine at the next convenient point in time. Otherwise 536inside the coro at the next convenient point in time. Otherwise
400clears the exception object. 537clears the exception object.
401 538
402Coro will check for the exception each time a schedule-like-function 539Coro will check for the exception each time a schedule-like-function
403returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down 540returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
404>>, C<< Coro::Handle->readable >> and so on. Most of these functions 541>>, C<< Coro::Handle->readable >> and so on. Most of these functions
… …
406 543
407The exception object will be thrown "as is" with the specified scalar in 544The exception object will be thrown "as is" with the specified scalar in
408C<$@>, i.e. if it is a string, no line number or newline will be appended 545C<$@>, i.e. if it is a string, no line number or newline will be appended
409(unlike with C<die>). 546(unlike with C<die>).
410 547
411This can be used as a softer means than C<cancel> to ask a coroutine to 548This can be used as a softer means than C<cancel> to ask a coro to
412end itself, although there is no guarantee that the exception will lead to 549end itself, although there is no guarantee that the exception will lead to
413termination, and if the exception isn't caught it might well end the whole 550termination, and if the exception isn't caught it might well end the whole
414program. 551program.
415 552
416You might also think of C<throw> as being the moral equivalent of 553You might also think of C<throw> as being the moral equivalent of
417C<kill>ing a coroutine with a signal (in this case, a scalar). 554C<kill>ing a coro with a signal (in this case, a scalar).
418 555
419=item $coroutine->join 556=item $coro->join
420 557
421Wait until the coroutine terminates and return any values given to the 558Wait until the coro terminates and return any values given to the
422C<terminate> or C<cancel> functions. C<join> can be called concurrently 559C<terminate> or C<cancel> functions. C<join> can be called concurrently
423from multiple coroutines, and all will be resumed and given the status 560from multiple coro, and all will be resumed and given the status
424return once the C<$coroutine> terminates. 561return once the C<$coro> terminates.
425 562
426=cut 563=cut
427 564
428sub join { 565sub join {
429 my $self = shift; 566 my $self = shift;
… …
440 } 577 }
441 578
442 wantarray ? @{$self->{_status}} : $self->{_status}[0]; 579 wantarray ? @{$self->{_status}} : $self->{_status}[0];
443} 580}
444 581
445=item $coroutine->on_destroy (\&cb) 582=item $coro->on_destroy (\&cb)
446 583
447Registers a callback that is called when this coroutine gets destroyed, 584Registers a callback that is called when this coro gets destroyed,
448but before it is joined. The callback gets passed the terminate arguments, 585but before it is joined. The callback gets passed the terminate arguments,
449if any, and I<must not> die, under any circumstances. 586if any, and I<must not> die, under any circumstances.
450 587
451=cut 588=cut
452 589
… …
454 my ($self, $cb) = @_; 591 my ($self, $cb) = @_;
455 592
456 push @{ $self->{_on_destroy} }, $cb; 593 push @{ $self->{_on_destroy} }, $cb;
457} 594}
458 595
459=item $oldprio = $coroutine->prio ($newprio) 596=item $oldprio = $coro->prio ($newprio)
460 597
461Sets (or gets, if the argument is missing) the priority of the 598Sets (or gets, if the argument is missing) the priority of the
462coroutine. Higher priority coroutines get run before lower priority 599coro. Higher priority coro get run before lower priority
463coroutines. Priorities are small signed integers (currently -4 .. +3), 600coro. Priorities are small signed integers (currently -4 .. +3),
464that 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
465to get then): 602to get then):
466 603
467 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
468 3 > 1 > 0 > -1 > -3 > -4 605 3 > 1 > 0 > -1 > -3 > -4
469 606
470 # set priority to HIGH 607 # set priority to HIGH
471 current->prio(PRIO_HIGH); 608 current->prio (PRIO_HIGH);
472 609
473The idle coroutine ($Coro::idle) always has a lower priority than any 610The idle coro ($Coro::idle) always has a lower priority than any
474existing coroutine. 611existing coro.
475 612
476Changing the priority of the current coroutine will take effect immediately, 613Changing the priority of the current coro will take effect immediately,
477but changing the priority of coroutines in the ready queue (but not 614but changing the priority of coro in the ready queue (but not
478running) will only take effect after the next schedule (of that 615running) will only take effect after the next schedule (of that
479coroutine). 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.
480 617
481=item $newprio = $coroutine->nice ($change) 618=item $newprio = $coro->nice ($change)
482 619
483Similar 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.
484higher values mean lower priority, just as in unix). 621higher values mean lower priority, just as in unix).
485 622
486=item $olddesc = $coroutine->desc ($newdesc) 623=item $olddesc = $coro->desc ($newdesc)
487 624
488Sets (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
489coroutine. This is just a free-form string you can associate with a 626coro. This is just a free-form string you can associate with a
490coroutine. 627coro.
491 628
492This method simply sets the C<< $coroutine->{desc} >> member to the given 629This method simply sets the C<< $coro->{desc} >> member to the given
493string. You can modify this member directly if you wish. 630string. You can modify this member directly if you wish.
494 631
495=cut 632=cut
496 633
497sub desc { 634sub desc {
498 my $old = $_[0]{desc}; 635 my $old = $_[0]{desc};
499 $_[0]{desc} = $_[1] if @_ > 1; 636 $_[0]{desc} = $_[1] if @_ > 1;
500 $old; 637 $old;
501} 638}
502 639
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
503=back 645=back
504 646
505=head2 GLOBAL FUNCTIONS 647=head1 GLOBAL FUNCTIONS
506 648
507=over 4 649=over 4
508 650
509=item Coro::nready 651=item Coro::nready
510 652
511Returns the number of coroutines that are currently in the ready state, 653Returns the number of coro that are currently in the ready state,
512i.e. that can be switched to by calling C<schedule> directory or 654i.e. that can be switched to by calling C<schedule> directory or
513indirectly. The value C<0> means that the only runnable coroutine is the 655indirectly. The value C<0> means that the only runnable coro is the
514currently running one, so C<cede> would have no effect, and C<schedule> 656currently running one, so C<cede> would have no effect, and C<schedule>
515would cause a deadlock unless there is an idle handler that wakes up some 657would cause a deadlock unless there is an idle handler that wakes up some
516coroutines. 658coro.
517 659
518=item my $guard = Coro::guard { ... } 660=item my $guard = Coro::guard { ... }
519 661
520This creates and returns a guard object. Nothing happens until the object 662This function still exists, but is deprecated. Please use the
521gets destroyed, in which case the codeblock given as argument will be 663C<Guard::guard> function instead.
522executed. This is useful to free locks or other resources in case of a
523runtime error or when the coroutine gets canceled, as in both cases the
524guard block will be executed. The guard object supports only one method,
525C<< ->cancel >>, which will keep the codeblock from being executed.
526 664
527Example: set some flag and clear it again when the coroutine gets canceled
528or the function returns:
529
530 sub do_something {
531 my $guard = Coro::guard { $busy = 0 };
532 $busy = 1;
533
534 # do something that requires $busy to be true
535 }
536
537=cut 665=cut
538 666
539sub guard(&) { 667BEGIN { *guard = \&Guard::guard }
540 bless \(my $cb = $_[0]), "Coro::guard"
541}
542
543sub Coro::guard::cancel {
544 ${$_[0]} = sub { };
545}
546
547sub Coro::guard::DESTROY {
548 ${$_[0]}->();
549}
550
551 668
552=item unblock_sub { ... } 669=item unblock_sub { ... }
553 670
554This utility function takes a BLOCK or code reference and "unblocks" it, 671This utility function takes a BLOCK or code reference and "unblocks" it,
555returning a new coderef. Unblocking means that calling the new coderef 672returning a new coderef. Unblocking means that calling the new coderef
556will return immediately without blocking, returning nothing, while the 673will return immediately without blocking, returning nothing, while the
557original code ref will be called (with parameters) from within another 674original code ref will be called (with parameters) from within another
558coroutine. 675coro.
559 676
560The 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
561venerable L<Event|Event> module) are not coroutine-safe (a weaker form 678venerable L<Event|Event> module) are not thread-safe (a weaker form
562of thread-safety). This means you must not block within event callbacks, 679of reentrancy). This means you must not block within event callbacks,
563otherwise you might suffer from crashes or worse. The only event library 680otherwise you might suffer from crashes or worse. The only event library
564currently known that is safe to use without C<unblock_sub> is L<EV>. 681currently known that is safe to use without C<unblock_sub> is L<EV>.
565 682
566This function allows your callbacks to block by executing them in another 683This function allows your callbacks to block by executing them in another
567coroutine 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
568is 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
569disk, for example. 686disk, for example.
570 687
571In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when 688In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
572creating event callbacks that want to block. 689creating event callbacks that want to block.
573 690
574If your handler does not plan to block (e.g. simply sends a message to 691If your handler does not plan to block (e.g. simply sends a message to
575another coroutine, or puts some other coroutine into the ready queue), 692another coro, or puts some other coro into the ready queue), there is
576there is no reason to use C<unblock_sub>. 693no reason to use C<unblock_sub>.
577 694
578Note that you also need to use C<unblock_sub> for any other callbacks that 695Note that you also need to use C<unblock_sub> for any other callbacks that
579are indirectly executed by any C-based event loop. For example, when you 696are indirectly executed by any C-based event loop. For example, when you
580use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it 697use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
581provides callbacks that are the result of some event callback, then you 698provides callbacks that are the result of some event callback, then you
… …
613 } 730 }
614} 731}
615 732
616=item $cb = Coro::rouse_cb 733=item $cb = Coro::rouse_cb
617 734
618Create and return a "rouse callback". That's a code reference that, when 735Create and return a "rouse callback". That's a code reference that,
619called, will save its arguments and notify the owner coroutine of the 736when called, will remember a copy of its arguments and notify the owner
620callback. 737coro of the callback.
621 738
622See the next function. 739See the next function.
623 740
624=item @args = Coro::rouse_wait [$cb] 741=item @args = Coro::rouse_wait [$cb]
625 742
626Wait for the specified rouse callback (or the last one tht was created in 743Wait for the specified rouse callback (or the last one that was created in
627this coroutine). 744this coro).
628 745
629As soon as the callback is invoked (or when the calback was invoked before 746As soon as the callback is invoked (or when the callback was invoked
630C<rouse_wait>), it will return a copy of the arguments originally passed 747before C<rouse_wait>), it will return the arguments originally passed to
631to the rouse callback. 748the rouse callback. In scalar context, that means you get the I<last>
749argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
750statement at the end.
632 751
633See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. 752See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
634 753
635=back 754=back
636 755
… …
638 757
6391; 7581;
640 759
641=head1 HOW TO WAIT FOR A CALLBACK 760=head1 HOW TO WAIT FOR A CALLBACK
642 761
643It is very common for a coroutine to wait for some callback to be 762It is very common for a coro to wait for some callback to be
644called. This occurs naturally when you use coroutines in an otherwise 763called. This occurs naturally when you use coro in an otherwise
645event-based program, or when you use event-based libraries. 764event-based program, or when you use event-based libraries.
646 765
647These typically register a callback for some event, and call that callback 766These typically register a callback for some event, and call that callback
648when the event occured. In a coroutine, however, you typically want to 767when the event occured. In a coro, however, you typically want to
649just wait for the event, simplyifying things. 768just wait for the event, simplyifying things.
650 769
651For example C<< AnyEvent->child >> registers a callback to be called when 770For example C<< AnyEvent->child >> registers a callback to be called when
652a specific child has exited: 771a specific child has exited:
653 772
654 my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... }); 773 my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
655 774
656But from withina coroutine, you often just want to write this: 775But from within a coro, you often just want to write this:
657 776
658 my $status = wait_for_child $pid; 777 my $status = wait_for_child $pid;
659 778
660Coro offers two functions specifically designed to make this easy, 779Coro offers two functions specifically designed to make this easy,
661C<Coro::rouse_cb> and C<Coro::rouse_wait>. 780C<Coro::rouse_cb> and C<Coro::rouse_wait>.
662 781
663The first function, C<rouse_cb>, generates and returns a callback that, 782The first function, C<rouse_cb>, generates and returns a callback that,
664when invoked, will save it's arguments and notify the coroutine that 783when invoked, will save its arguments and notify the coro that
665created the callback. 784created the callback.
666 785
667The second function, C<rouse_wait>, waits for the callback to be called 786The second function, C<rouse_wait>, waits for the callback to be called
668(by calling C<schedule> to go to sleep) and returns the arguments 787(by calling C<schedule> to go to sleep) and returns the arguments
669originally passed to the callback. 788originally passed to the callback.
… …
684you can roll your own, using C<schedule>: 803you can roll your own, using C<schedule>:
685 804
686 sub wait_for_child($) { 805 sub wait_for_child($) {
687 my ($pid) = @_; 806 my ($pid) = @_;
688 807
689 # store the current coroutine in $current, 808 # store the current coro in $current,
690 # and provide result variables for the closure passed to ->child 809 # and provide result variables for the closure passed to ->child
691 my $current = $Coro::current; 810 my $current = $Coro::current;
692 my ($done, $rstatus); 811 my ($done, $rstatus);
693 812
694 # pass a closure to ->child 813 # pass a closure to ->child
… …
710 829
711=item fork with pthread backend 830=item fork with pthread backend
712 831
713When Coro is compiled using the pthread backend (which isn't recommended 832When Coro is compiled using the pthread backend (which isn't recommended
714but required on many BSDs as their libcs are completely broken), then 833but required on many BSDs as their libcs are completely broken), then
715coroutines will not survive a fork. There is no known workaround except to 834coro will not survive a fork. There is no known workaround except to
716fix your libc and use a saner backend. 835fix your libc and use a saner backend.
717 836
718=item perl process emulation ("threads") 837=item perl process emulation ("threads")
719 838
720This module is not perl-pseudo-thread-safe. You should only ever use this 839This module is not perl-pseudo-thread-safe. You should only ever use this
721module from the same thread (this requirement might be removed in the 840module from the first thread (this requirement might be removed in the
722future 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
723this). I recommend disabling thread support and using processes, as having 842this). I recommend disabling thread support and using processes, as having
724the windows process emulation enabled under unix roughly halves perl 843the windows process emulation enabled under unix roughly halves perl
725performance, even when not used. 844performance, even when not used.
726 845
727=item coroutine switching not signal safe 846=item coro switching is not signal safe
728 847
729You must not switch to another coroutine from within a signal handler 848You must not switch to another coro from within a signal handler
730(only relevant with %SIG - most event libraries provide safe signals). 849(only relevant with %SIG - most event libraries provide safe signals).
731 850
732That means you I<MUST NOT> call any function that might "block" the 851That means you I<MUST NOT> call any function that might "block" the
733current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or 852current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
734anything that calls those. Everything else, including calling C<ready>, 853anything that calls those. Everything else, including calling C<ready>,
735works. 854works.
736 855
737=back 856=back
738 857
… …
743 862
744Debugging: L<Coro::Debug>. 863Debugging: L<Coro::Debug>.
745 864
746Support/Utility: L<Coro::Specific>, L<Coro::Util>. 865Support/Utility: L<Coro::Specific>, L<Coro::Util>.
747 866
748Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. 867Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
868L<Coro::SemaphoreSet>, L<Coro::RWLock>.
749 869
750IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>. 870I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
751 871
752Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>. 872Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
873a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
874L<Coro::Select>.
753 875
754XS API: L<Coro::MakeMaker>. 876XS API: L<Coro::MakeMaker>.
755 877
756Low level Configuration, Coroutine Environment: L<Coro::State>. 878Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
757 879
758=head1 AUTHOR 880=head1 AUTHOR
759 881
760 Marc Lehmann <schmorp@schmorp.de> 882 Marc Lehmann <schmorp@schmorp.de>
761 http://home.schmorp.de/ 883 http://home.schmorp.de/

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