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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 my $lock = new Coro::Semaphore; 22 my $lock = new Coro::Semaphore;
22 my $locked; 23 my $locked;
23 24
24 $lock->down; 25 $lock->down;
25 $locked = 1; 26 $locked = 1;
26 $lock->up; 27 $lock->up;
27 28
28=head1 DESCRIPTION 29=head1 DESCRIPTION
29 30
30This module collection manages coroutines. Coroutines are similar to 31For a tutorial-style introduction, please read the L<Coro::Intro>
31threads but don't (in general) run in parallel at the same time even 32manpage. This manpage mainly contains reference information.
32on SMP machines. The specific flavor of coroutine used in this module
33also guarantees you that it will not switch between coroutines unless
34necessary, at easily-identified points in your program, so locking and
35parallel access are rarely an issue, making coroutine programming much
36safer and easier than threads programming.
37 33
38Unlike a normal perl program, however, coroutines allow you to have 34This module collection manages continuations in general, most often in
39multiple running interpreters that share data, which is especially useful 35the form of cooperative threads (also called coros, or simply "coro"
40to code pseudo-parallel processes, such as multiple HTTP-GET requests 36in the documentation). They are similar to kernel threads but don't (in
41running concurrently. 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.
42 43
43Coroutines are also useful because Perl has no support for threads (the so 44Unlike the so-called "Perl threads" (which are not actually real threads
44called "threads" that perl offers are nothing more than the (bad) process 45but only the windows process emulation ported to unix, and as such act
45emulation coming from the Windows platform: On standard operating systems 46as processes), Coro provides a full shared address space, which makes
46they serve no purpose whatsoever, except by making your programs slow and 47communication between threads very easy. And Coro's threads are fast,
47making 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
48aks 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.
49 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
50In this module, coroutines are defined as "callchain + lexical variables + 60In this module, a thread is defined as "callchain + lexical variables +
51@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain, 61some package variables + C stack), that is, a thread has its own callchain,
52its 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
53variables (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.
54 67
55=cut 68=cut
56 69
57package Coro; 70package Coro;
58 71
59use strict; 72use strict qw(vars subs);
60no warnings "uninitialized"; 73no warnings "uninitialized";
61 74
75use Guard ();
76
62use Coro::State; 77use Coro::State;
63 78
64use base qw(Coro::State Exporter); 79use base qw(Coro::State Exporter);
65 80
66our $idle; # idle handler 81our $idle; # idle handler
67our $main; # main coroutine 82our $main; # main coro
68our $current; # current coroutine 83our $current; # current coro
69 84
70our $VERSION = 4.6; 85our $VERSION = 5.132;
71 86
72our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); 87our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
73our %EXPORT_TAGS = ( 88our %EXPORT_TAGS = (
74 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 89 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
75); 90);
76our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); 91our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
77 92
93=head1 GLOBAL VARIABLES
94
78=over 4 95=over 4
79 96
80=item $Coro::main 97=item $Coro::main
81 98
82This variable stores the coroutine object that represents the main 99This variable stores the Coro object that represents the main
83program. While you cna C<ready> it and do most other things you can do to 100program. While you cna C<ready> it and do most other things you can do to
84coroutines, it is mainly useful to compare again C<$Coro::current>, to see 101coro, it is mainly useful to compare again C<$Coro::current>, to see
85wether you are running in the main program or not. 102whether you are running in the main program or not.
86 103
87=cut 104=cut
88 105
89$main = new Coro; 106# $main is now being initialised by Coro::State
90 107
91=item $Coro::current 108=item $Coro::current
92 109
93The coroutine object representing the current coroutine (the last 110The Coro object representing the current coro (the last
94coroutine that the Coro scheduler switched to). The initial value is 111coro that the Coro scheduler switched to). The initial value is
95C<$main> (of course). 112C<$Coro::main> (of course).
96 113
97This variable is B<strictly> I<read-only>. You can take copies of the 114This variable is B<strictly> I<read-only>. You can take copies of the
98value stored in it and use it as any other coroutine object, but you must 115value stored in it and use it as any other Coro object, but you must
99not otherwise modify the variable itself. 116not otherwise modify the variable itself.
100 117
101=cut 118=cut
102 119
103$main->{desc} = "[main::]";
104
105# maybe some other module used Coro::Specific before...
106$main->{_specific} = $current->{_specific}
107 if $current;
108
109_set_current $main;
110
111sub current() { $current } # [DEPRECATED] 120sub current() { $current } # [DEPRECATED]
112 121
113=item $Coro::idle 122=item $Coro::idle
114 123
115This 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
116usually 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
117pretty low-level functionality. 126pretty low-level functionality.
118 127
119This 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
120finds no ready coroutines to run. The default implementation prints 131ready coros to run. The default implementation prints "FATAL:
121"FATAL: deadlock detected" and exits, because the program has no other way 132deadlock detected" and exits, because the program has no other way to
122to continue. 133continue.
123 134
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
124This hook is overwritten by modules such as C<Coro::Timer> and 139This hook is overwritten by modules such as C<Coro::EV> and
125C<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
126coroutine so the scheduler can run it. 141coro so the scheduler can run it.
127 142
128Note that the callback I<must not>, under any circumstances, block 143Note that the callback I<must not>, under any circumstances, block
129the current coroutine. Normally, this is achieved by having an "idle 144the current coro. Normally, this is achieved by having an "idle
130coroutine" that calls the event loop and then blocks again, and then 145coro" that calls the event loop and then blocks again, and then
131readying that coroutine in the idle handler. 146readying that coro in the idle handler, or by simply placing the idle
147coro in this variable.
132 148
133See 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
134technique. 150technique.
135 151
136Please 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
… …
141$idle = sub { 157$idle = sub {
142 require Carp; 158 require Carp;
143 Carp::croak ("FATAL: deadlock detected"); 159 Carp::croak ("FATAL: deadlock detected");
144}; 160};
145 161
146sub _cancel {
147 my ($self) = @_;
148
149 # free coroutine data and mark as destructed
150 $self->_destroy
151 or return;
152
153 # call all destruction callbacks
154 $_->(@{$self->{_status}})
155 for @{(delete $self->{_on_destroy}) || []};
156}
157
158# this coroutine is necessary because a coroutine 162# this coro is necessary because a coro
159# cannot destroy itself. 163# cannot destroy itself.
160my @destroy; 164our @destroy;
161my $manager; 165our $manager;
162 166
163$manager = new Coro sub { 167$manager = new Coro sub {
164 while () { 168 while () {
165 (shift @destroy)->_cancel 169 Coro::State::cancel shift @destroy
166 while @destroy; 170 while @destroy;
167 171
168 &schedule; 172 &schedule;
169 } 173 }
170}; 174};
171$manager->desc ("[coro manager]"); 175$manager->{desc} = "[coro manager]";
172$manager->prio (PRIO_MAX); 176$manager->prio (PRIO_MAX);
173 177
174=back 178=back
175 179
176=head2 SIMPLE COROUTINE CREATION 180=head1 SIMPLE CORO CREATION
177 181
178=over 4 182=over 4
179 183
180=item async { ... } [@args...] 184=item async { ... } [@args...]
181 185
182Create a new coroutine and return it's coroutine object (usually 186Create a new coro and return its Coro object (usually
183unused). The coroutine will be put into the ready queue, so 187unused). The coro will be put into the ready queue, so
184it will start running automatically on the next scheduler run. 188it will start running automatically on the next scheduler run.
185 189
186The 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
187coroutine. When it returns argument returns the coroutine is automatically 191coro. When it returns argument returns the coro is automatically
188terminated. 192terminated.
189 193
190The remaining arguments are passed as arguments to the closure. 194The remaining arguments are passed as arguments to the closure.
191 195
192See the C<Coro::State::new> constructor for info about the coroutine 196See the C<Coro::State::new> constructor for info about the coro
193environment in which coroutines are executed. 197environment in which coro are executed.
194 198
195Calling 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
196the coroutine. Likewise, when the coroutine dies, the program will exit, 200the coro. Likewise, when the coro dies, the program will exit,
197just as it would in the main program. 201just as it would in the main program.
198 202
199If 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
200simply avoid dieing (by use of C<eval>). 204simply avoid dieing (by use of C<eval>).
201 205
202Example: Create a new coroutine that just prints its arguments. 206Example: Create a new coro that just prints its arguments.
203 207
204 async { 208 async {
205 print "@_\n"; 209 print "@_\n";
206 } 1,2,3,4; 210 } 1,2,3,4;
207 211
… …
213 $coro 217 $coro
214} 218}
215 219
216=item async_pool { ... } [@args...] 220=item async_pool { ... } [@args...]
217 221
218Similar to C<async>, but uses a coroutine pool, so you should not call 222Similar to C<async>, but uses a coro pool, so you should not call
219terminate or join on it (although you are allowed to), and you get a 223terminate or join on it (although you are allowed to), and you get a
220coroutine that might have executed other code already (which can be good 224coro that might have executed other code already (which can be good
221or bad :). 225or bad :).
222 226
223On the plus side, this function is faster than creating (and destroying) 227On the plus side, this function is about twice as fast as creating (and
224a completely new coroutine, so if you need a lot of generic coroutines in 228destroying) a completely new coro, so if you need a lot of generic
225quick successsion, use C<async_pool>, not C<async>. 229coros in quick successsion, use C<async_pool>, not C<async>.
226 230
227The code block is executed in an C<eval> context and a warning will be 231The code block is executed in an C<eval> context and a warning will be
228issued in case of an exception instead of terminating the program, as 232issued in case of an exception instead of terminating the program, as
229C<async> does. As the coroutine is being reused, stuff like C<on_destroy> 233C<async> does. As the coro is being reused, stuff like C<on_destroy>
230will not work in the expected way, unless you call terminate or cancel, 234will not work in the expected way, unless you call terminate or cancel,
231which somehow defeats the purpose of pooling (but is fine in the 235which somehow defeats the purpose of pooling (but is fine in the
232exceptional case). 236exceptional case).
233 237
234The priority will be reset to C<0> after each run, tracing will be 238The priority will be reset to C<0> after each run, tracing will be
235disabled, the description will be reset and the default output filehandle 239disabled, the description will be reset and the default output filehandle
236gets restored, so you can change all these. Otherwise the coroutine will 240gets restored, so you can change all these. Otherwise the coro will
237be re-used "as-is": most notably if you change other per-coroutine global 241be re-used "as-is": most notably if you change other per-coro global
238stuff such as C<$/> you I<must needs> to revert that change, which is most 242stuff such as C<$/> you I<must needs> revert that change, which is most
239simply done by using local as in: C< local $/ >. 243simply done by using local as in: C<< local $/ >>.
240 244
241The pool size is limited to C<8> idle coroutines (this can be adjusted by 245The idle pool size is limited to C<8> idle coros (this can be
242changing $Coro::POOL_SIZE), and there can be as many non-idle coros as 246adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
243required. 247coros as required.
244 248
245If you are concerned about pooled coroutines growing a lot because a 249If you are concerned about pooled coros growing a lot because a
246single C<async_pool> used a lot of stackspace you can e.g. C<async_pool 250single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
247{ terminate }> once per second or so to slowly replenish the pool. In 251{ terminate }> once per second or so to slowly replenish the pool. In
248addition to that, when the stacks used by a handler grows larger than 16kb 252addition to that, when the stacks used by a handler grows larger than 32kb
249(adjustable via $Coro::POOL_RSS) it will also be destroyed. 253(adjustable via $Coro::POOL_RSS) it will also be destroyed.
250 254
251=cut 255=cut
252 256
253our $POOL_SIZE = 8; 257our $POOL_SIZE = 8;
254our $POOL_RSS = 16 * 1024; 258our $POOL_RSS = 32 * 1024;
255our @async_pool; 259our @async_pool;
256 260
257sub pool_handler { 261sub pool_handler {
258 my $cb;
259
260 while () { 262 while () {
261 eval { 263 eval {
262 while () { 264 &{&_pool_handler} while 1;
263 _pool_1 $cb;
264 &$cb;
265 _pool_2 $cb;
266 &schedule;
267 }
268 }; 265 };
269 266
270 last if $@ eq "\3async_pool terminate\2\n";
271 warn $@ if $@; 267 warn $@ if $@;
272 } 268 }
273} 269}
274 270
275sub async_pool(&@) {
276 # this is also inlined into the unlock_scheduler
277 my $coro = (pop @async_pool) || new Coro \&pool_handler;
278
279 $coro->{_invoke} = [@_];
280 $coro->ready;
281
282 $coro
283}
284
285=back 271=back
286 272
287=head2 STATIC METHODS 273=head1 STATIC METHODS
288 274
289Static methods are actually functions that operate on the current coroutine. 275Static methods are actually functions that implicitly operate on the
276current coro.
290 277
291=over 4 278=over 4
292 279
293=item schedule 280=item schedule
294 281
295Calls the scheduler. The scheduler will find the next coroutine that is 282Calls the scheduler. The scheduler will find the next coro that is
296to be run from the ready queue and switches to it. The next coroutine 283to be run from the ready queue and switches to it. The next coro
297to be run is simply the one with the highest priority that is longest 284to be run is simply the one with the highest priority that is longest
298in its ready queue. If there is no coroutine ready, it will clal the 285in its ready queue. If there is no coro ready, it will clal the
299C<$Coro::idle> hook. 286C<$Coro::idle> hook.
300 287
301Please note that the current coroutine will I<not> be put into the ready 288Please note that the current coro will I<not> be put into the ready
302queue, so calling this function usually means you will never be called 289queue, so calling this function usually means you will never be called
303again unless something else (e.g. an event handler) calls C<< ->ready >>, 290again unless something else (e.g. an event handler) calls C<< ->ready >>,
304thus waking you up. 291thus waking you up.
305 292
306This makes C<schedule> I<the> generic method to use to block the current 293This makes C<schedule> I<the> generic method to use to block the current
307coroutine and wait for events: first you remember the current coroutine in 294coro and wait for events: first you remember the current coro in
308a variable, then arrange for some callback of yours to call C<< ->ready 295a variable, then arrange for some callback of yours to call C<< ->ready
309>> on that once some event happens, and last you call C<schedule> to put 296>> on that once some event happens, and last you call C<schedule> to put
310yourself to sleep. Note that a lot of things can wake your coroutine up, 297yourself to sleep. Note that a lot of things can wake your coro up,
311so you need to check wether the event indeed happened, e.g. by storing the 298so you need to check whether the event indeed happened, e.g. by storing the
312status in a variable. 299status in a variable.
313 300
314The canonical way to wait on external events is this: 301See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
315 302
316 { 303=item cede
317 # remember current coroutine
318 my $current = $Coro::current;
319 304
320 # register a hypothetical event handler 305"Cede" to other coros. This function puts the current coro into
321 on_event_invoke sub { 306the ready queue and calls C<schedule>, which has the effect of giving
322 # wake up sleeping coroutine 307up the current "timeslice" to other coros of the same or higher
323 $current->ready; 308priority. Once your coro gets its turn again it will automatically be
324 undef $current; 309resumed.
310
311This function is often called C<yield> in other languages.
312
313=item Coro::cede_notself
314
315Works like cede, but is not exported by default and will cede to I<any>
316coro, regardless of priority. This is useful sometimes to ensure
317progress is made.
318
319=item terminate [arg...]
320
321Terminates the current coro with the given status values (see L<cancel>).
322
323=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
324
325These function install enter and leave winders in the current scope. The
326enter block will be executed when on_enter is called and whenever the
327current coro is re-entered by the scheduler, while the leave block is
328executed whenever the current coro is blocked by the scheduler, and
329also when the containing scope is exited (by whatever means, be it exit,
330die, last etc.).
331
332I<Neither invoking the scheduler, nor exceptions, are allowed within those
333BLOCKs>. That means: do not even think about calling C<die> without an
334eval, and do not even think of entering the scheduler in any way.
335
336Since both BLOCKs are tied to the current scope, they will automatically
337be removed when the current scope exits.
338
339These functions implement the same concept as C<dynamic-wind> in scheme
340does, and are useful when you want to localise some resource to a specific
341coro.
342
343They slow down thread switching considerably for coros that use them
344(about 40% for a BLOCK with a single assignment, so thread switching is
345still reasonably fast if the handlers are fast).
346
347These functions are best understood by an example: The following function
348will change the current timezone to "Antarctica/South_Pole", which
349requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
350which remember/change the current timezone and restore the previous
351value, respectively, the timezone is only changed for the coro that
352installed those handlers.
353
354 use POSIX qw(tzset);
355
356 async {
357 my $old_tz; # store outside TZ value here
358
359 Coro::on_enter {
360 $old_tz = $ENV{TZ}; # remember the old value
361
362 $ENV{TZ} = "Antarctica/South_Pole";
363 tzset; # enable new value
325 }; 364 };
326 365
327 # call schedule until event occurred. 366 Coro::on_leave {
328 # in case we are woken up for other reasons 367 $ENV{TZ} = $old_tz;
329 # (current still defined), loop. 368 tzset; # restore old value
330 Coro::schedule while $current; 369 };
370
371 # at this place, the timezone is Antarctica/South_Pole,
372 # without disturbing the TZ of any other coro.
331 } 373 };
332 374
333=item cede 375This can be used to localise about any resource (locale, uid, current
376working directory etc.) to a block, despite the existance of other
377coros.
334 378
335"Cede" to other coroutines. This function puts the current coroutine into 379Another interesting example implements time-sliced multitasking using
336the ready queue and calls C<schedule>, which has the effect of giving 380interval timers (this could obviously be optimised, but does the job):
337up the current "timeslice" to other coroutines of the same or higher
338priority. Once your coroutine gets its turn again it will automatically be
339resumed.
340 381
341This function is often called C<yield> in other languages. 382 # "timeslice" the given block
383 sub timeslice(&) {
384 use Time::HiRes ();
342 385
343=item Coro::cede_notself 386 Coro::on_enter {
387 # on entering the thread, we set an VTALRM handler to cede
388 $SIG{VTALRM} = sub { cede };
389 # and then start the interval timer
390 Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
391 };
392 Coro::on_leave {
393 # on leaving the thread, we stop the interval timer again
394 Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
395 };
344 396
345Works like cede, but is not exported by default and will cede to I<any> 397 &{+shift};
346coroutine, regardless of priority. This is useful sometimes to ensure 398 }
347progress is made.
348 399
349=item terminate [arg...] 400 # use like this:
401 timeslice {
402 # The following is an endless loop that would normally
403 # monopolise the process. Since it runs in a timesliced
404 # environment, it will regularly cede to other threads.
405 while () { }
406 };
350 407
351Terminates the current coroutine with the given status values (see L<cancel>).
352 408
353=item killall 409=item killall
354 410
355Kills/terminates/cancels all coroutines except the currently running 411Kills/terminates/cancels all coros except the currently running one.
356one. This is useful after a fork, either in the child or the parent, as
357usually only one of them should inherit the running coroutines.
358 412
359Note that while this will try to free some of the main programs resources, 413Note that while this will try to free some of the main interpreter
414resources if the calling coro isn't the main coro, but one
360you cnanot free all of them, so if a coroutine that is not the main 415cannot free all of them, so if a coro that is not the main coro
361program calls this function, there will be some one-time resource leak. 416calls this function, there will be some one-time resource leak.
362 417
363=cut 418=cut
364
365sub terminate {
366 $current->cancel (@_);
367}
368 419
369sub killall { 420sub killall {
370 for (Coro::State::list) { 421 for (Coro::State::list) {
371 $_->cancel 422 $_->cancel
372 if $_ != $current && UNIVERSAL::isa $_, "Coro"; 423 if $_ != $current && UNIVERSAL::isa $_, "Coro";
373 } 424 }
374} 425}
375 426
376=back 427=back
377 428
378=head2 COROUTINE METHODS 429=head1 CORO OBJECT METHODS
379 430
380These are the methods you can call on coroutine objects (or to create 431These are the methods you can call on coro objects (or to create
381them). 432them).
382 433
383=over 4 434=over 4
384 435
385=item new Coro \&sub [, @args...] 436=item new Coro \&sub [, @args...]
386 437
387Create a new coroutine and return it. When the sub returns, the coroutine 438Create a new coro and return it. When the sub returns, the coro
388automatically terminates as if C<terminate> with the returned values were 439automatically terminates as if C<terminate> with the returned values were
389called. To make the coroutine run you must first put it into the ready 440called. To make the coro run you must first put it into the ready
390queue by calling the ready method. 441queue by calling the ready method.
391 442
392See C<async> and C<Coro::State::new> for additional info about the 443See C<async> and C<Coro::State::new> for additional info about the
393coroutine environment. 444coro environment.
394 445
395=cut 446=cut
396 447
397sub _run_coro { 448sub _coro_run {
398 terminate &{+shift}; 449 terminate &{+shift};
399} 450}
400 451
401sub new {
402 my $class = shift;
403
404 $class->SUPER::new (\&_run_coro, @_)
405}
406
407=item $success = $coroutine->ready 452=item $success = $coro->ready
408 453
409Put the given coroutine into the end of its ready queue (there is one 454Put the given coro into the end of its ready queue (there is one
410queue for each priority) and return true. If the coroutine is already in 455queue for each priority) and return true. If the coro is already in
411the ready queue, do nothing and return false. 456the ready queue, do nothing and return false.
412 457
413This ensures that the scheduler will resume this coroutine automatically 458This ensures that the scheduler will resume this coro automatically
414once all the coroutines of higher priority and all coroutines of the same 459once all the coro of higher priority and all coro of the same
415priority that were put into the ready queue earlier have been resumed. 460priority that were put into the ready queue earlier have been resumed.
416 461
462=item $coro->suspend
463
464Suspends the specified coro. A suspended coro works just like any other
465coro, except that the scheduler will not select a suspended coro for
466execution.
467
468Suspending a coro can be useful when you want to keep the coro from
469running, but you don't want to destroy it, or when you want to temporarily
470freeze a coro (e.g. for debugging) to resume it later.
471
472A scenario for the former would be to suspend all (other) coros after a
473fork and keep them alive, so their destructors aren't called, but new
474coros can be created.
475
476=item $coro->resume
477
478If the specified coro was suspended, it will be resumed. Note that when
479the coro was in the ready queue when it was suspended, it might have been
480unreadied by the scheduler, so an activation might have been lost.
481
482To avoid this, it is best to put a suspended coro into the ready queue
483unconditionally, as every synchronisation mechanism must protect itself
484against spurious wakeups, and the one in the Coro family certainly do
485that.
486
417=item $is_ready = $coroutine->is_ready 487=item $is_ready = $coro->is_ready
418 488
419Return wether the coroutine is currently the ready queue or not, 489Returns true iff the Coro object is in the ready queue. Unless the Coro
490object gets destroyed, it will eventually be scheduled by the scheduler.
420 491
492=item $is_running = $coro->is_running
493
494Returns true iff the Coro object is currently running. Only one Coro object
495can ever be in the running state (but it currently is possible to have
496multiple running Coro::States).
497
498=item $is_suspended = $coro->is_suspended
499
500Returns true iff this Coro object has been suspended. Suspended Coros will
501not ever be scheduled.
502
421=item $coroutine->cancel (arg...) 503=item $coro->cancel (arg...)
422 504
423Terminates the given coroutine and makes it return the given arguments as 505Terminates the given Coro and makes it return the given arguments as
424status (default: the empty list). Never returns if the coroutine is the 506status (default: the empty list). Never returns if the Coro is the
425current coroutine. 507current Coro.
426 508
427=cut 509=cut
428 510
429sub cancel { 511sub cancel {
430 my $self = shift; 512 my $self = shift;
431 $self->{_status} = [@_];
432 513
433 if ($current == $self) { 514 if ($current == $self) {
434 push @destroy, $self; 515 terminate @_;
435 $manager->ready;
436 &schedule while 1;
437 } else { 516 } else {
438 $self->_cancel; 517 $self->{_status} = [@_];
518 Coro::State::cancel $self;
439 } 519 }
440} 520}
441 521
522=item $coro->schedule_to
523
524Puts the current coro to sleep (like C<Coro::schedule>), but instead
525of continuing with the next coro from the ready queue, always switch to
526the given coro object (regardless of priority etc.). The readyness
527state of that coro isn't changed.
528
529This is an advanced method for special cases - I'd love to hear about any
530uses for this one.
531
532=item $coro->cede_to
533
534Like C<schedule_to>, but puts the current coro into the ready
535queue. This has the effect of temporarily switching to the given
536coro, and continuing some time later.
537
538This is an advanced method for special cases - I'd love to hear about any
539uses for this one.
540
541=item $coro->throw ([$scalar])
542
543If C<$throw> is specified and defined, it will be thrown as an exception
544inside the coro at the next convenient point in time. Otherwise
545clears the exception object.
546
547Coro will check for the exception each time a schedule-like-function
548returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
549>>, C<< Coro::Handle->readable >> and so on. Most of these functions
550detect this case and return early in case an exception is pending.
551
552The exception object will be thrown "as is" with the specified scalar in
553C<$@>, i.e. if it is a string, no line number or newline will be appended
554(unlike with C<die>).
555
556This can be used as a softer means than C<cancel> to ask a coro to
557end itself, although there is no guarantee that the exception will lead to
558termination, and if the exception isn't caught it might well end the whole
559program.
560
561You might also think of C<throw> as being the moral equivalent of
562C<kill>ing a coro with a signal (in this case, a scalar).
563
442=item $coroutine->join 564=item $coro->join
443 565
444Wait until the coroutine terminates and return any values given to the 566Wait until the coro terminates and return any values given to the
445C<terminate> or C<cancel> functions. C<join> can be called concurrently 567C<terminate> or C<cancel> functions. C<join> can be called concurrently
446from multiple coroutines, and all will be resumed and given the status 568from multiple coro, and all will be resumed and given the status
447return once the C<$coroutine> terminates. 569return once the C<$coro> terminates.
448 570
449=cut 571=cut
450 572
451sub join { 573sub join {
452 my $self = shift; 574 my $self = shift;
… …
463 } 585 }
464 586
465 wantarray ? @{$self->{_status}} : $self->{_status}[0]; 587 wantarray ? @{$self->{_status}} : $self->{_status}[0];
466} 588}
467 589
468=item $coroutine->on_destroy (\&cb) 590=item $coro->on_destroy (\&cb)
469 591
470Registers a callback that is called when this coroutine gets destroyed, 592Registers a callback that is called when this coro gets destroyed,
471but before it is joined. The callback gets passed the terminate arguments, 593but before it is joined. The callback gets passed the terminate arguments,
472if any, and I<must not> die, under any circumstances. 594if any, and I<must not> die, under any circumstances.
473 595
474=cut 596=cut
475 597
… …
477 my ($self, $cb) = @_; 599 my ($self, $cb) = @_;
478 600
479 push @{ $self->{_on_destroy} }, $cb; 601 push @{ $self->{_on_destroy} }, $cb;
480} 602}
481 603
482=item $oldprio = $coroutine->prio ($newprio) 604=item $oldprio = $coro->prio ($newprio)
483 605
484Sets (or gets, if the argument is missing) the priority of the 606Sets (or gets, if the argument is missing) the priority of the
485coroutine. Higher priority coroutines get run before lower priority 607coro. Higher priority coro get run before lower priority
486coroutines. Priorities are small signed integers (currently -4 .. +3), 608coro. Priorities are small signed integers (currently -4 .. +3),
487that you can refer to using PRIO_xxx constants (use the import tag :prio 609that you can refer to using PRIO_xxx constants (use the import tag :prio
488to get then): 610to get then):
489 611
490 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 612 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
491 3 > 1 > 0 > -1 > -3 > -4 613 3 > 1 > 0 > -1 > -3 > -4
492 614
493 # set priority to HIGH 615 # set priority to HIGH
494 current->prio(PRIO_HIGH); 616 current->prio (PRIO_HIGH);
495 617
496The idle coroutine ($Coro::idle) always has a lower priority than any 618The idle coro ($Coro::idle) always has a lower priority than any
497existing coroutine. 619existing coro.
498 620
499Changing the priority of the current coroutine will take effect immediately, 621Changing the priority of the current coro will take effect immediately,
500but changing the priority of coroutines in the ready queue (but not 622but changing the priority of coro in the ready queue (but not
501running) will only take effect after the next schedule (of that 623running) will only take effect after the next schedule (of that
502coroutine). This is a bug that will be fixed in some future version. 624coro). This is a bug that will be fixed in some future version.
503 625
504=item $newprio = $coroutine->nice ($change) 626=item $newprio = $coro->nice ($change)
505 627
506Similar to C<prio>, but subtract the given value from the priority (i.e. 628Similar to C<prio>, but subtract the given value from the priority (i.e.
507higher values mean lower priority, just as in unix). 629higher values mean lower priority, just as in unix).
508 630
509=item $olddesc = $coroutine->desc ($newdesc) 631=item $olddesc = $coro->desc ($newdesc)
510 632
511Sets (or gets in case the argument is missing) the description for this 633Sets (or gets in case the argument is missing) the description for this
512coroutine. This is just a free-form string you can associate with a coroutine. 634coro. This is just a free-form string you can associate with a
635coro.
513 636
514This method simply sets the C<< $coroutine->{desc} >> member to the given string. You 637This method simply sets the C<< $coro->{desc} >> member to the given
515can modify this member directly if you wish. 638string. You can modify this member directly if you wish.
516
517=item $coroutine->throw ([$scalar])
518
519If C<$throw> is specified and defined, it will be thrown as an exception
520inside the coroutine at the next convinient point in time (usually after
521it gains control at the next schedule/transfer/cede). Otherwise clears the
522exception object.
523
524The exception object will be thrown "as is" with the specified scalar in
525C<$@>, i.e. if it is a string, no line number or newline will be appended
526(unlike with C<die>).
527
528This can be used as a softer means than C<cancel> to ask a coroutine to
529end itself, although there is no guarentee that the exception will lead to
530termination, and if the exception isn't caught it might well end the whole
531program.
532 639
533=cut 640=cut
534 641
535sub desc { 642sub desc {
536 my $old = $_[0]{desc}; 643 my $old = $_[0]{desc};
537 $_[0]{desc} = $_[1] if @_ > 1; 644 $_[0]{desc} = $_[1] if @_ > 1;
538 $old; 645 $old;
539} 646}
540 647
648sub transfer {
649 require Carp;
650 Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
651}
652
541=back 653=back
542 654
543=head2 GLOBAL FUNCTIONS 655=head1 GLOBAL FUNCTIONS
544 656
545=over 4 657=over 4
546 658
547=item Coro::nready 659=item Coro::nready
548 660
549Returns the number of coroutines that are currently in the ready state, 661Returns the number of coro that are currently in the ready state,
550i.e. that can be switched to by calling C<schedule> directory or 662i.e. that can be switched to by calling C<schedule> directory or
551indirectly. The value C<0> means that the only runnable coroutine is the 663indirectly. The value C<0> means that the only runnable coro is the
552currently running one, so C<cede> would have no effect, and C<schedule> 664currently running one, so C<cede> would have no effect, and C<schedule>
553would cause a deadlock unless there is an idle handler that wakes up some 665would cause a deadlock unless there is an idle handler that wakes up some
554coroutines. 666coro.
555 667
556=item my $guard = Coro::guard { ... } 668=item my $guard = Coro::guard { ... }
557 669
558This creates and returns a guard object. Nothing happens until the object 670This function still exists, but is deprecated. Please use the
559gets destroyed, in which case the codeblock given as argument will be 671C<Guard::guard> function instead.
560executed. This is useful to free locks or other resources in case of a
561runtime error or when the coroutine gets canceled, as in both cases the
562guard block will be executed. The guard object supports only one method,
563C<< ->cancel >>, which will keep the codeblock from being executed.
564 672
565Example: set some flag and clear it again when the coroutine gets canceled
566or the function returns:
567
568 sub do_something {
569 my $guard = Coro::guard { $busy = 0 };
570 $busy = 1;
571
572 # do something that requires $busy to be true
573 }
574
575=cut 673=cut
576 674
577sub guard(&) { 675BEGIN { *guard = \&Guard::guard }
578 bless \(my $cb = $_[0]), "Coro::guard"
579}
580
581sub Coro::guard::cancel {
582 ${$_[0]} = sub { };
583}
584
585sub Coro::guard::DESTROY {
586 ${$_[0]}->();
587}
588
589 676
590=item unblock_sub { ... } 677=item unblock_sub { ... }
591 678
592This utility function takes a BLOCK or code reference and "unblocks" it, 679This utility function takes a BLOCK or code reference and "unblocks" it,
593returning a new coderef. Unblocking means that calling the new coderef 680returning a new coderef. Unblocking means that calling the new coderef
594will return immediately without blocking, returning nothing, while the 681will return immediately without blocking, returning nothing, while the
595original code ref will be called (with parameters) from within another 682original code ref will be called (with parameters) from within another
596coroutine. 683coro.
597 684
598The reason this function exists is that many event libraries (such as the 685The reason this function exists is that many event libraries (such as the
599venerable L<Event|Event> module) are not coroutine-safe (a weaker form 686venerable L<Event|Event> module) are not thread-safe (a weaker form
600of thread-safety). This means you must not block within event callbacks, 687of reentrancy). This means you must not block within event callbacks,
601otherwise you might suffer from crashes or worse. The only event library 688otherwise you might suffer from crashes or worse. The only event library
602currently known that is safe to use without C<unblock_sub> is L<EV>. 689currently known that is safe to use without C<unblock_sub> is L<EV>.
603 690
604This function allows your callbacks to block by executing them in another 691This function allows your callbacks to block by executing them in another
605coroutine where it is safe to block. One example where blocking is handy 692coro where it is safe to block. One example where blocking is handy
606is when you use the L<Coro::AIO|Coro::AIO> functions to save results to 693is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
607disk, for example. 694disk, for example.
608 695
609In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when 696In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
610creating event callbacks that want to block. 697creating event callbacks that want to block.
611 698
612If your handler does not plan to block (e.g. simply sends a message to 699If your handler does not plan to block (e.g. simply sends a message to
613another coroutine, or puts some other coroutine into the ready queue), 700another coro, or puts some other coro into the ready queue), there is
614there is no reason to use C<unblock_sub>. 701no reason to use C<unblock_sub>.
702
703Note that you also need to use C<unblock_sub> for any other callbacks that
704are indirectly executed by any C-based event loop. For example, when you
705use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
706provides callbacks that are the result of some event callback, then you
707must not block either, or use C<unblock_sub>.
615 708
616=cut 709=cut
617 710
618our @unblock_queue; 711our @unblock_queue;
619 712
… …
622# return immediately and can be reused) and because we cannot cede 715# return immediately and can be reused) and because we cannot cede
623# inside an event callback. 716# inside an event callback.
624our $unblock_scheduler = new Coro sub { 717our $unblock_scheduler = new Coro sub {
625 while () { 718 while () {
626 while (my $cb = pop @unblock_queue) { 719 while (my $cb = pop @unblock_queue) {
627 # this is an inlined copy of async_pool 720 &async_pool (@$cb);
628 my $coro = (pop @async_pool) || new Coro \&pool_handler;
629 721
630 $coro->{_invoke} = $cb;
631 $coro->ready;
632 cede; # for short-lived callbacks, this reduces pressure on the coro pool 722 # for short-lived callbacks, this reduces pressure on the coro pool
723 # as the chance is very high that the async_poll coro will be back
724 # in the idle state when cede returns
725 cede;
633 } 726 }
634 schedule; # sleep well 727 schedule; # sleep well
635 } 728 }
636}; 729};
637$unblock_scheduler->desc ("[unblock_sub scheduler]"); 730$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
638 731
639sub unblock_sub(&) { 732sub unblock_sub(&) {
640 my $cb = shift; 733 my $cb = shift;
641 734
642 sub { 735 sub {
643 unshift @unblock_queue, [$cb, @_]; 736 unshift @unblock_queue, [$cb, @_];
644 $unblock_scheduler->ready; 737 $unblock_scheduler->ready;
645 } 738 }
646} 739}
647 740
741=item $cb = Coro::rouse_cb
742
743Create and return a "rouse callback". That's a code reference that,
744when called, will remember a copy of its arguments and notify the owner
745coro of the callback.
746
747See the next function.
748
749=item @args = Coro::rouse_wait [$cb]
750
751Wait for the specified rouse callback (or the last one that was created in
752this coro).
753
754As soon as the callback is invoked (or when the callback was invoked
755before C<rouse_wait>), it will return the arguments originally passed to
756the rouse callback.
757
758See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
759
648=back 760=back
649 761
650=cut 762=cut
651 763
6521; 7641;
653 765
766=head1 HOW TO WAIT FOR A CALLBACK
767
768It is very common for a coro to wait for some callback to be
769called. This occurs naturally when you use coro in an otherwise
770event-based program, or when you use event-based libraries.
771
772These typically register a callback for some event, and call that callback
773when the event occured. In a coro, however, you typically want to
774just wait for the event, simplyifying things.
775
776For example C<< AnyEvent->child >> registers a callback to be called when
777a specific child has exited:
778
779 my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
780
781But from within a coro, you often just want to write this:
782
783 my $status = wait_for_child $pid;
784
785Coro offers two functions specifically designed to make this easy,
786C<Coro::rouse_cb> and C<Coro::rouse_wait>.
787
788The first function, C<rouse_cb>, generates and returns a callback that,
789when invoked, will save its arguments and notify the coro that
790created the callback.
791
792The second function, C<rouse_wait>, waits for the callback to be called
793(by calling C<schedule> to go to sleep) and returns the arguments
794originally passed to the callback.
795
796Using these functions, it becomes easy to write the C<wait_for_child>
797function mentioned above:
798
799 sub wait_for_child($) {
800 my ($pid) = @_;
801
802 my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
803
804 my ($rpid, $rstatus) = Coro::rouse_wait;
805 $rstatus
806 }
807
808In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
809you can roll your own, using C<schedule>:
810
811 sub wait_for_child($) {
812 my ($pid) = @_;
813
814 # store the current coro in $current,
815 # and provide result variables for the closure passed to ->child
816 my $current = $Coro::current;
817 my ($done, $rstatus);
818
819 # pass a closure to ->child
820 my $watcher = AnyEvent->child (pid => $pid, cb => sub {
821 $rstatus = $_[1]; # remember rstatus
822 $done = 1; # mark $rstatus as valud
823 });
824
825 # wait until the closure has been called
826 schedule while !$done;
827
828 $rstatus
829 }
830
831
654=head1 BUGS/LIMITATIONS 832=head1 BUGS/LIMITATIONS
655 833
834=over 4
835
836=item fork with pthread backend
837
838When Coro is compiled using the pthread backend (which isn't recommended
839but required on many BSDs as their libcs are completely broken), then
840coro will not survive a fork. There is no known workaround except to
841fix your libc and use a saner backend.
842
843=item perl process emulation ("threads")
844
656This module is not perl-pseudo-thread-safe. You should only ever use this 845This module is not perl-pseudo-thread-safe. You should only ever use this
657module from the same thread (this requirement might be removed in the 846module from the first thread (this requirement might be removed in the
658future to allow per-thread schedulers, but Coro::State does not yet allow 847future to allow per-thread schedulers, but Coro::State does not yet allow
659this). I recommend disabling thread support and using processes, as this 848this). I recommend disabling thread support and using processes, as having
660is much faster and uses less memory. 849the windows process emulation enabled under unix roughly halves perl
850performance, even when not used.
851
852=item coro switching is not signal safe
853
854You must not switch to another coro from within a signal handler
855(only relevant with %SIG - most event libraries provide safe signals).
856
857That means you I<MUST NOT> call any function that might "block" the
858current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
859anything that calls those. Everything else, including calling C<ready>,
860works.
861
862=back
863
661 864
662=head1 SEE ALSO 865=head1 SEE ALSO
663 866
664Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. 867Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
665 868
666Debugging: L<Coro::Debug>. 869Debugging: L<Coro::Debug>.
667 870
668Support/Utility: L<Coro::Specific>, L<Coro::Util>. 871Support/Utility: L<Coro::Specific>, L<Coro::Util>.
669 872
670Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. 873Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
874L<Coro::SemaphoreSet>, L<Coro::RWLock>.
671 875
672IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>. 876I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
673 877
674Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>. 878Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
879a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
880L<Coro::Select>.
675 881
676XS API: L<Coro::MakeMaker>. 882XS API: L<Coro::MakeMaker>.
677 883
678Low level Configuration, Coroutine Environment: L<Coro::State>. 884Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
679 885
680=head1 AUTHOR 886=head1 AUTHOR
681 887
682 Marc Lehmann <schmorp@schmorp.de> 888 Marc Lehmann <schmorp@schmorp.de>
683 http://home.schmorp.de/ 889 http://home.schmorp.de/

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