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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
9 async { 9 async {
10 # some asynchronous thread of execution 10 # some asynchronous thread of execution
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 31For a tutorial-style introduction, please read the L<Coro::Intro>
31to threads but don't run in parallel at the same time even on SMP 32manpage. This manpage mainly contains reference information.
32machines. The specific flavor of coroutine used in this module also
33guarantees 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 than threads programming.
37 33
38(Perl, however, does not natively support real threads but instead does a 34This module collection manages continuations in general, most often in
39very slow and memory-intensive emulation of processes using threads. This 35the form of cooperative threads (also called coros, or simply "coro"
40is a performance win on Windows machines, and a loss everywhere else). 36in the documentation). They are similar to kernel threads but don't (in
37general) run in parallel at the same time even on SMP machines. The
38specific flavor of thread offered by this module also guarantees you that
39it will not switch between threads unless necessary, at easily-identified
40points in your program, so locking and parallel access are rarely an
41issue, making thread programming much safer and easier than using other
42thread models.
41 43
44Unlike the so-called "Perl threads" (which are not actually real threads
45but only the windows process emulation (see section of same name for more
46details) ported to unix, and as such act as processes), Coro provides
47a full shared address space, which makes communication between threads
48very easy. And Coro's threads are fast, too: disabling the Windows
49process emulation code in your perl and using Coro can easily result in
50a two to four times speed increase for your programs. A parallel matrix
51multiplication benchmark runs over 300 times faster on a single core than
52perl's pseudo-threads on a quad core using all four cores.
53
54Coro achieves that by supporting multiple running interpreters that share
55data, which is especially useful to code pseudo-parallel processes and
56for event-based programming, such as multiple HTTP-GET requests running
57concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
58into an event-based environment.
59
42In this module, coroutines are defined as "callchain + lexical variables + 60In this module, a thread is defined as "callchain + lexical variables +
43@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain, 61some package variables + C stack), that is, a thread has its own callchain,
44its 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
45variables (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.
46 67
47=cut 68=cut
48 69
49package Coro; 70package Coro;
50 71
51use strict; 72use common::sense;
52no warnings "uninitialized"; 73
74use Carp ();
75
76use Guard ();
53 77
54use Coro::State; 78use Coro::State;
55 79
56use base qw(Coro::State Exporter); 80use base qw(Coro::State Exporter);
57 81
58our $idle; # idle handler 82our $idle; # idle handler
59our $main; # main coroutine 83our $main; # main coro
60our $current; # current coroutine 84our $current; # current coro
61 85
62our $VERSION = '4.5'; 86our $VERSION = 5.17;
63 87
64our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); 88our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
65our %EXPORT_TAGS = ( 89our %EXPORT_TAGS = (
66 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 90 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
67); 91);
68our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); 92our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
69 93
70{ 94=head1 GLOBAL VARIABLES
71 my @async;
72 my $init;
73
74 # this way of handling attributes simply is NOT scalable ;()
75 sub import {
76 no strict 'refs';
77
78 Coro->export_to_level (1, @_);
79
80 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
81 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
82 my ($package, $ref) = (shift, shift);
83 my @attrs;
84 for (@_) {
85 if ($_ eq "Coro") {
86 push @async, $ref;
87 unless ($init++) {
88 eval q{
89 sub INIT {
90 &async(pop @async) while @async;
91 }
92 };
93 }
94 } else {
95 push @attrs, $_;
96 }
97 }
98 return $old ? $old->($package, $ref, @attrs) : @attrs;
99 };
100 }
101
102}
103 95
104=over 4 96=over 4
105 97
106=item $main 98=item $Coro::main
107 99
108This coroutine represents the main program. 100This variable stores the Coro object that represents the main
101program. While you cna C<ready> it and do most other things you can do to
102coro, it is mainly useful to compare again C<$Coro::current>, to see
103whether you are running in the main program or not.
109 104
110=cut 105=cut
111 106
112$main = new Coro; 107# $main is now being initialised by Coro::State
113 108
114=item $current (or as function: current) 109=item $Coro::current
115 110
116The current coroutine (the last coroutine switched to). The initial value 111The Coro object representing the current coro (the last
112coro that the Coro scheduler switched to). The initial value is
117is C<$main> (of course). 113C<$Coro::main> (of course).
118 114
119This variable is B<strictly> I<read-only>. It is provided for performance 115This variable is B<strictly> I<read-only>. You can take copies of the
120reasons. If performance is not essential you are encouraged to use the 116value stored in it and use it as any other Coro object, but you must
121C<Coro::current> function instead. 117not otherwise modify the variable itself.
122 118
123=cut 119=cut
124 120
125$main->{desc} = "[main::]";
126
127# maybe some other module used Coro::Specific before...
128$main->{_specific} = $current->{_specific}
129 if $current;
130
131_set_current $main;
132
133sub current() { $current } 121sub current() { $current } # [DEPRECATED]
134 122
135=item $idle 123=item $Coro::idle
136 124
125This variable is mainly useful to integrate Coro into event loops. It is
126usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
127pretty low-level functionality.
128
129This variable stores either a Coro object or a callback.
130
137A callback that is called whenever the scheduler finds no ready coroutines 131If it is a callback, the it is called whenever the scheduler finds no
138to run. The default implementation prints "FATAL: deadlock detected" and 132ready coros to run. The default implementation prints "FATAL:
139exits, because the program has no other way to continue. 133deadlock detected" and exits, because the program has no other way to
134continue.
140 135
136If it is a coro object, then this object will be readied (without
137invoking any ready hooks, however) when the scheduler finds no other ready
138coros to run.
139
141This hook is overwritten by modules such as C<Coro::Timer> and 140This hook is overwritten by modules such as C<Coro::EV> and
142C<Coro::Event> to wait on an external event that hopefully wake up a 141C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
143coroutine so the scheduler can run it. 142coro so the scheduler can run it.
143
144Note that the callback I<must not>, under any circumstances, block
145the current coro. Normally, this is achieved by having an "idle
146coro" that calls the event loop and then blocks again, and then
147readying that coro in the idle handler, or by simply placing the idle
148coro in this variable.
149
150See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
151technique.
144 152
145Please note that if your callback recursively invokes perl (e.g. for event 153Please note that if your callback recursively invokes perl (e.g. for event
146handlers), then it must be prepared to be called recursively itself. 154handlers), then it must be prepared to be called recursively itself.
147 155
148=cut 156=cut
149 157
150$idle = sub { 158$idle = sub {
151 require Carp; 159 warn "oi\n";#d#
152 Carp::croak ("FATAL: deadlock detected"); 160 Carp::confess ("FATAL: deadlock detected");
153}; 161};
154 162
155sub _cancel {
156 my ($self) = @_;
157
158 # free coroutine data and mark as destructed
159 $self->_destroy
160 or return;
161
162 # call all destruction callbacks
163 $_->(@{$self->{_status}})
164 for @{(delete $self->{_on_destroy}) || []};
165}
166
167# this coroutine is necessary because a coroutine 163# this coro is necessary because a coro
168# cannot destroy itself. 164# cannot destroy itself.
169my @destroy; 165our @destroy;
170my $manager; 166our $manager;
171 167
172$manager = new Coro sub { 168$manager = new Coro sub {
173 while () { 169 while () {
174 (shift @destroy)->_cancel 170 Coro::State::cancel shift @destroy
175 while @destroy; 171 while @destroy;
176 172
177 &schedule; 173 &schedule;
178 } 174 }
179}; 175};
180$manager->desc ("[coro manager]"); 176$manager->{desc} = "[coro manager]";
181$manager->prio (PRIO_MAX); 177$manager->prio (PRIO_MAX);
182 178
183# static methods. not really.
184
185=back 179=back
186 180
187=head2 STATIC METHODS 181=head1 SIMPLE CORO CREATION
188
189Static methods are actually functions that operate on the current coroutine only.
190 182
191=over 4 183=over 4
192 184
193=item async { ... } [@args...] 185=item async { ... } [@args...]
194 186
195Create a new asynchronous coroutine and return it's coroutine object 187Create a new coro and return its Coro object (usually
196(usually unused). When the sub returns the new coroutine is automatically 188unused). The coro will be put into the ready queue, so
189it will start running automatically on the next scheduler run.
190
191The first argument is a codeblock/closure that should be executed in the
192coro. When it returns argument returns the coro is automatically
197terminated. 193terminated.
198 194
195The remaining arguments are passed as arguments to the closure.
196
199See the C<Coro::State::new> constructor for info about the coroutine 197See the C<Coro::State::new> constructor for info about the coro
200environment in which coroutines run. 198environment in which coro are executed.
201 199
202Calling C<exit> in a coroutine will do the same as calling exit outside 200Calling C<exit> in a coro will do the same as calling exit outside
203the coroutine. Likewise, when the coroutine dies, the program will exit, 201the coro. Likewise, when the coro dies, the program will exit,
204just as it would in the main program. 202just as it would in the main program.
205 203
204If you do not want that, you can provide a default C<die> handler, or
205simply avoid dieing (by use of C<eval>).
206
206 # create a new coroutine that just prints its arguments 207Example: Create a new coro that just prints its arguments.
208
207 async { 209 async {
208 print "@_\n"; 210 print "@_\n";
209 } 1,2,3,4; 211 } 1,2,3,4;
210 212
211=cut
212
213sub async(&@) {
214 my $coro = new Coro @_;
215 $coro->ready;
216 $coro
217}
218
219=item async_pool { ... } [@args...] 213=item async_pool { ... } [@args...]
220 214
221Similar to C<async>, but uses a coroutine pool, so you should not call 215Similar to C<async>, but uses a coro pool, so you should not call
222terminate or join (although you are allowed to), and you get a coroutine 216terminate or join on it (although you are allowed to), and you get a
223that might have executed other code already (which can be good or bad :). 217coro that might have executed other code already (which can be good
218or bad :).
224 219
220On the plus side, this function is about twice as fast as creating (and
221destroying) a completely new coro, so if you need a lot of generic
222coros in quick successsion, use C<async_pool>, not C<async>.
223
225Also, the block is executed in an C<eval> context and a warning will be 224The code block is executed in an C<eval> context and a warning will be
226issued in case of an exception instead of terminating the program, as 225issued in case of an exception instead of terminating the program, as
227C<async> does. As the coroutine is being reused, stuff like C<on_destroy> 226C<async> does. As the coro is being reused, stuff like C<on_destroy>
228will not work in the expected way, unless you call terminate or cancel, 227will not work in the expected way, unless you call terminate or cancel,
229which somehow defeats the purpose of pooling. 228which somehow defeats the purpose of pooling (but is fine in the
229exceptional case).
230 230
231The priority will be reset to C<0> after each job, tracing will be 231The priority will be reset to C<0> after each run, tracing will be
232disabled, the description will be reset and the default output filehandle 232disabled, the description will be reset and the default output filehandle
233gets restored, so you can change alkl these. Otherwise the coroutine will 233gets restored, so you can change all these. Otherwise the coro will
234be re-used "as-is": most notably if you change other per-coroutine global 234be re-used "as-is": most notably if you change other per-coro global
235stuff such as C<$/> you need to revert that change, which is most simply 235stuff such as C<$/> you I<must needs> revert that change, which is most
236done by using local as in C< local $/ >. 236simply done by using local as in: C<< local $/ >>.
237 237
238The pool size is limited to 8 idle coroutines (this can be adjusted by 238The idle pool size is limited to C<8> idle coros (this can be
239changing $Coro::POOL_SIZE), and there can be as many non-idle coros as 239adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
240required. 240coros as required.
241 241
242If you are concerned about pooled coroutines growing a lot because a 242If you are concerned about pooled coros growing a lot because a
243single C<async_pool> used a lot of stackspace you can e.g. C<async_pool 243single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
244{ terminate }> once per second or so to slowly replenish the pool. In 244{ terminate }> once per second or so to slowly replenish the pool. In
245addition to that, when the stacks used by a handler grows larger than 16kb 245addition to that, when the stacks used by a handler grows larger than 32kb
246(adjustable with $Coro::POOL_RSS) it will also exit. 246(adjustable via $Coro::POOL_RSS) it will also be destroyed.
247 247
248=cut 248=cut
249 249
250our $POOL_SIZE = 8; 250our $POOL_SIZE = 8;
251our $POOL_RSS = 16 * 1024; 251our $POOL_RSS = 32 * 1024;
252our @async_pool; 252our @async_pool;
253 253
254sub pool_handler { 254sub pool_handler {
255 my $cb;
256
257 while () { 255 while () {
258 eval { 256 eval {
259 while () { 257 &{&_pool_handler} while 1;
260 _pool_1 $cb;
261 &$cb;
262 _pool_2 $cb;
263 &schedule;
264 }
265 }; 258 };
266 259
267 last if $@ eq "\3async_pool terminate\2\n";
268 warn $@ if $@; 260 warn $@ if $@;
269 } 261 }
270} 262}
271 263
272sub async_pool(&@) { 264=back
273 # this is also inlined into the unlock_scheduler
274 my $coro = (pop @async_pool) || new Coro \&pool_handler;
275 265
276 $coro->{_invoke} = [@_]; 266=head1 STATIC METHODS
277 $coro->ready;
278 267
279 $coro 268Static methods are actually functions that implicitly operate on the
280} 269current coro.
270
271=over 4
281 272
282=item schedule 273=item schedule
283 274
284Calls the scheduler. Please note that the current coroutine will not be put 275Calls the scheduler. The scheduler will find the next coro that is
276to be run from the ready queue and switches to it. The next coro
277to be run is simply the one with the highest priority that is longest
278in its ready queue. If there is no coro ready, it will clal the
279C<$Coro::idle> hook.
280
281Please note that the current coro will I<not> be put into the ready
285into the ready queue, so calling this function usually means you will 282queue, so calling this function usually means you will never be called
286never be called again unless something else (e.g. an event handler) calls 283again unless something else (e.g. an event handler) calls C<< ->ready >>,
287ready. 284thus waking you up.
288 285
289The canonical way to wait on external events is this: 286This makes C<schedule> I<the> generic method to use to block the current
287coro and wait for events: first you remember the current coro in
288a variable, then arrange for some callback of yours to call C<< ->ready
289>> on that once some event happens, and last you call C<schedule> to put
290yourself to sleep. Note that a lot of things can wake your coro up,
291so you need to check whether the event indeed happened, e.g. by storing the
292status in a variable.
290 293
291 { 294See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
292 # remember current coroutine
293 my $current = $Coro::current;
294 295
295 # register a hypothetical event handler 296=item cede
296 on_event_invoke sub { 297
297 # wake up sleeping coroutine 298"Cede" to other coros. This function puts the current coro into
298 $current->ready; 299the ready queue and calls C<schedule>, which has the effect of giving
299 undef $current; 300up the current "timeslice" to other coros of the same or higher
301priority. Once your coro gets its turn again it will automatically be
302resumed.
303
304This function is often called C<yield> in other languages.
305
306=item Coro::cede_notself
307
308Works like cede, but is not exported by default and will cede to I<any>
309coro, regardless of priority. This is useful sometimes to ensure
310progress is made.
311
312=item terminate [arg...]
313
314Terminates the current coro with the given status values (see L<cancel>).
315
316=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
317
318These function install enter and leave winders in the current scope. The
319enter block will be executed when on_enter is called and whenever the
320current coro is re-entered by the scheduler, while the leave block is
321executed whenever the current coro is blocked by the scheduler, and
322also when the containing scope is exited (by whatever means, be it exit,
323die, last etc.).
324
325I<Neither invoking the scheduler, nor exceptions, are allowed within those
326BLOCKs>. That means: do not even think about calling C<die> without an
327eval, and do not even think of entering the scheduler in any way.
328
329Since both BLOCKs are tied to the current scope, they will automatically
330be removed when the current scope exits.
331
332These functions implement the same concept as C<dynamic-wind> in scheme
333does, and are useful when you want to localise some resource to a specific
334coro.
335
336They slow down thread switching considerably for coros that use them
337(about 40% for a BLOCK with a single assignment, so thread switching is
338still reasonably fast if the handlers are fast).
339
340These functions are best understood by an example: The following function
341will change the current timezone to "Antarctica/South_Pole", which
342requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
343which remember/change the current timezone and restore the previous
344value, respectively, the timezone is only changed for the coro that
345installed those handlers.
346
347 use POSIX qw(tzset);
348
349 async {
350 my $old_tz; # store outside TZ value here
351
352 Coro::on_enter {
353 $old_tz = $ENV{TZ}; # remember the old value
354
355 $ENV{TZ} = "Antarctica/South_Pole";
356 tzset; # enable new value
300 }; 357 };
301 358
302 # call schedule until event occurred. 359 Coro::on_leave {
303 # in case we are woken up for other reasons 360 $ENV{TZ} = $old_tz;
304 # (current still defined), loop. 361 tzset; # restore old value
305 Coro::schedule while $current; 362 };
363
364 # at this place, the timezone is Antarctica/South_Pole,
365 # without disturbing the TZ of any other coro.
306 } 366 };
307 367
308=item cede 368This can be used to localise about any resource (locale, uid, current
369working directory etc.) to a block, despite the existance of other
370coros.
309 371
310"Cede" to other coroutines. This function puts the current coroutine into the 372Another interesting example implements time-sliced multitasking using
311ready queue and calls C<schedule>, which has the effect of giving up the 373interval timers (this could obviously be optimised, but does the job):
312current "timeslice" to other coroutines of the same or higher priority.
313 374
314=item Coro::cede_notself 375 # "timeslice" the given block
376 sub timeslice(&) {
377 use Time::HiRes ();
315 378
316Works like cede, but is not exported by default and will cede to any 379 Coro::on_enter {
317coroutine, regardless of priority, once. 380 # on entering the thread, we set an VTALRM handler to cede
381 $SIG{VTALRM} = sub { cede };
382 # and then start the interval timer
383 Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
384 };
385 Coro::on_leave {
386 # on leaving the thread, we stop the interval timer again
387 Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
388 };
318 389
319=item terminate [arg...] 390 &{+shift};
391 }
320 392
321Terminates the current coroutine with the given status values (see L<cancel>). 393 # use like this:
394 timeslice {
395 # The following is an endless loop that would normally
396 # monopolise the process. Since it runs in a timesliced
397 # environment, it will regularly cede to other threads.
398 while () { }
399 };
400
322 401
323=item killall 402=item killall
324 403
325Kills/terminates/cancels all coroutines except the currently running 404Kills/terminates/cancels all coros except the currently running one.
326one. This is useful after a fork, either in the child or the parent, as
327usually only one of them should inherit the running coroutines.
328 405
329=cut 406Note that while this will try to free some of the main interpreter
407resources if the calling coro isn't the main coro, but one
408cannot free all of them, so if a coro that is not the main coro
409calls this function, there will be some one-time resource leak.
330 410
331sub terminate { 411=cut
332 $current->cancel (@_);
333}
334 412
335sub killall { 413sub killall {
336 for (Coro::State::list) { 414 for (Coro::State::list) {
337 $_->cancel 415 $_->cancel
338 if $_ != $current && UNIVERSAL::isa $_, "Coro"; 416 if $_ != $current && UNIVERSAL::isa $_, "Coro";
339 } 417 }
340} 418}
341 419
342=back 420=back
343 421
344# dynamic methods
345
346=head2 COROUTINE METHODS 422=head1 CORO OBJECT METHODS
347 423
348These are the methods you can call on coroutine objects. 424These are the methods you can call on coro objects (or to create
425them).
349 426
350=over 4 427=over 4
351 428
352=item new Coro \&sub [, @args...] 429=item new Coro \&sub [, @args...]
353 430
354Create a new coroutine and return it. When the sub returns the coroutine 431Create a new coro and return it. When the sub returns, the coro
355automatically terminates as if C<terminate> with the returned values were 432automatically terminates as if C<terminate> with the returned values were
356called. To make the coroutine run you must first put it into the ready queue 433called. To make the coro run you must first put it into the ready
357by calling the ready method. 434queue by calling the ready method.
358 435
359See C<async> and C<Coro::State::new> for additional info about the 436See C<async> and C<Coro::State::new> for additional info about the
360coroutine environment. 437coro environment.
361 438
362=cut 439=cut
363 440
364sub _run_coro { 441sub _coro_run {
365 terminate &{+shift}; 442 terminate &{+shift};
366} 443}
367 444
368sub new {
369 my $class = shift;
370
371 $class->SUPER::new (\&_run_coro, @_)
372}
373
374=item $success = $coroutine->ready 445=item $success = $coro->ready
375 446
376Put the given coroutine into the ready queue (according to it's priority) 447Put the given coro into the end of its ready queue (there is one
377and return true. If the coroutine is already in the ready queue, do nothing 448queue for each priority) and return true. If the coro is already in
378and return false. 449the ready queue, do nothing and return false.
379 450
451This ensures that the scheduler will resume this coro automatically
452once all the coro of higher priority and all coro of the same
453priority that were put into the ready queue earlier have been resumed.
454
455=item $coro->suspend
456
457Suspends the specified coro. A suspended coro works just like any other
458coro, except that the scheduler will not select a suspended coro for
459execution.
460
461Suspending a coro can be useful when you want to keep the coro from
462running, but you don't want to destroy it, or when you want to temporarily
463freeze a coro (e.g. for debugging) to resume it later.
464
465A scenario for the former would be to suspend all (other) coros after a
466fork and keep them alive, so their destructors aren't called, but new
467coros can be created.
468
469=item $coro->resume
470
471If the specified coro was suspended, it will be resumed. Note that when
472the coro was in the ready queue when it was suspended, it might have been
473unreadied by the scheduler, so an activation might have been lost.
474
475To avoid this, it is best to put a suspended coro into the ready queue
476unconditionally, as every synchronisation mechanism must protect itself
477against spurious wakeups, and the one in the Coro family certainly do
478that.
479
380=item $is_ready = $coroutine->is_ready 480=item $is_ready = $coro->is_ready
381 481
382Return wether the coroutine is currently the ready queue or not, 482Returns true iff the Coro object is in the ready queue. Unless the Coro
483object gets destroyed, it will eventually be scheduled by the scheduler.
383 484
485=item $is_running = $coro->is_running
486
487Returns true iff the Coro object is currently running. Only one Coro object
488can ever be in the running state (but it currently is possible to have
489multiple running Coro::States).
490
491=item $is_suspended = $coro->is_suspended
492
493Returns true iff this Coro object has been suspended. Suspended Coros will
494not ever be scheduled.
495
384=item $coroutine->cancel (arg...) 496=item $coro->cancel (arg...)
385 497
386Terminates the given coroutine and makes it return the given arguments as 498Terminates the given Coro and makes it return the given arguments as
387status (default: the empty list). Never returns if the coroutine is the 499status (default: the empty list). Never returns if the Coro is the
388current coroutine. 500current Coro.
389 501
390=cut 502=cut
391 503
392sub cancel { 504sub cancel {
393 my $self = shift; 505 my $self = shift;
394 $self->{_status} = [@_];
395 506
396 if ($current == $self) { 507 if ($current == $self) {
397 push @destroy, $self; 508 terminate @_;
398 $manager->ready;
399 &schedule while 1;
400 } else { 509 } else {
401 $self->_cancel; 510 $self->{_status} = [@_];
511 Coro::State::cancel $self;
402 } 512 }
403} 513}
404 514
515=item $coro->schedule_to
516
517Puts the current coro to sleep (like C<Coro::schedule>), but instead
518of continuing with the next coro from the ready queue, always switch to
519the given coro object (regardless of priority etc.). The readyness
520state of that coro isn't changed.
521
522This is an advanced method for special cases - I'd love to hear about any
523uses for this one.
524
525=item $coro->cede_to
526
527Like C<schedule_to>, but puts the current coro into the ready
528queue. This has the effect of temporarily switching to the given
529coro, and continuing some time later.
530
531This is an advanced method for special cases - I'd love to hear about any
532uses for this one.
533
534=item $coro->throw ([$scalar])
535
536If C<$throw> is specified and defined, it will be thrown as an exception
537inside the coro at the next convenient point in time. Otherwise
538clears the exception object.
539
540Coro will check for the exception each time a schedule-like-function
541returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
542>>, C<< Coro::Handle->readable >> and so on. Most of these functions
543detect this case and return early in case an exception is pending.
544
545The exception object will be thrown "as is" with the specified scalar in
546C<$@>, i.e. if it is a string, no line number or newline will be appended
547(unlike with C<die>).
548
549This can be used as a softer means than C<cancel> to ask a coro to
550end itself, although there is no guarantee that the exception will lead to
551termination, and if the exception isn't caught it might well end the whole
552program.
553
554You might also think of C<throw> as being the moral equivalent of
555C<kill>ing a coro with a signal (in this case, a scalar).
556
405=item $coroutine->join 557=item $coro->join
406 558
407Wait until the coroutine terminates and return any values given to the 559Wait until the coro terminates and return any values given to the
408C<terminate> or C<cancel> functions. C<join> can be called concurrently 560C<terminate> or C<cancel> functions. C<join> can be called concurrently
409from multiple coroutines. 561from multiple coro, and all will be resumed and given the status
562return once the C<$coro> terminates.
410 563
411=cut 564=cut
412 565
413sub join { 566sub join {
414 my $self = shift; 567 my $self = shift;
425 } 578 }
426 579
427 wantarray ? @{$self->{_status}} : $self->{_status}[0]; 580 wantarray ? @{$self->{_status}} : $self->{_status}[0];
428} 581}
429 582
430=item $coroutine->on_destroy (\&cb) 583=item $coro->on_destroy (\&cb)
431 584
432Registers a callback that is called when this coroutine gets destroyed, 585Registers a callback that is called when this coro gets destroyed,
433but before it is joined. The callback gets passed the terminate arguments, 586but before it is joined. The callback gets passed the terminate arguments,
434if any. 587if any, and I<must not> die, under any circumstances.
435 588
436=cut 589=cut
437 590
438sub on_destroy { 591sub on_destroy {
439 my ($self, $cb) = @_; 592 my ($self, $cb) = @_;
440 593
441 push @{ $self->{_on_destroy} }, $cb; 594 push @{ $self->{_on_destroy} }, $cb;
442} 595}
443 596
444=item $oldprio = $coroutine->prio ($newprio) 597=item $oldprio = $coro->prio ($newprio)
445 598
446Sets (or gets, if the argument is missing) the priority of the 599Sets (or gets, if the argument is missing) the priority of the
447coroutine. Higher priority coroutines get run before lower priority 600coro. Higher priority coro get run before lower priority
448coroutines. Priorities are small signed integers (currently -4 .. +3), 601coro. Priorities are small signed integers (currently -4 .. +3),
449that you can refer to using PRIO_xxx constants (use the import tag :prio 602that you can refer to using PRIO_xxx constants (use the import tag :prio
450to get then): 603to get then):
451 604
452 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 605 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
453 3 > 1 > 0 > -1 > -3 > -4 606 3 > 1 > 0 > -1 > -3 > -4
454 607
455 # set priority to HIGH 608 # set priority to HIGH
456 current->prio(PRIO_HIGH); 609 current->prio (PRIO_HIGH);
457 610
458The idle coroutine ($Coro::idle) always has a lower priority than any 611The idle coro ($Coro::idle) always has a lower priority than any
459existing coroutine. 612existing coro.
460 613
461Changing the priority of the current coroutine will take effect immediately, 614Changing the priority of the current coro will take effect immediately,
462but changing the priority of coroutines in the ready queue (but not 615but changing the priority of coro in the ready queue (but not
463running) will only take effect after the next schedule (of that 616running) will only take effect after the next schedule (of that
464coroutine). This is a bug that will be fixed in some future version. 617coro). This is a bug that will be fixed in some future version.
465 618
466=item $newprio = $coroutine->nice ($change) 619=item $newprio = $coro->nice ($change)
467 620
468Similar to C<prio>, but subtract the given value from the priority (i.e. 621Similar to C<prio>, but subtract the given value from the priority (i.e.
469higher values mean lower priority, just as in unix). 622higher values mean lower priority, just as in unix).
470 623
471=item $olddesc = $coroutine->desc ($newdesc) 624=item $olddesc = $coro->desc ($newdesc)
472 625
473Sets (or gets in case the argument is missing) the description for this 626Sets (or gets in case the argument is missing) the description for this
474coroutine. This is just a free-form string you can associate with a coroutine. 627coro. This is just a free-form string you can associate with a
628coro.
475 629
476This method simply sets the C<< $coroutine->{desc} >> member to the given string. You 630This method simply sets the C<< $coro->{desc} >> member to the given
477can modify this member directly if you wish. 631string. You can modify this member directly if you wish.
478
479=item $coroutine->throw ([$scalar])
480
481If C<$throw> is specified and defined, it will be thrown as an exception
482inside the coroutine at the next convinient point in time (usually after
483it gains control at the next schedule/transfer/cede). Otherwise clears the
484exception object.
485
486The exception object will be thrown "as is" with the specified scalar in
487C<$@>, i.e. if it is a string, no line number or newline will be appended
488(unlike with C<die>).
489
490This can be used as a softer means than C<cancel> to ask a coroutine to
491end itself, although there is no guarentee that the exception will lead to
492termination, and if the exception isn't caught it might well end the whole
493program.
494 632
495=cut 633=cut
496 634
497sub desc { 635sub desc {
498 my $old = $_[0]{desc}; 636 my $old = $_[0]{desc};
499 $_[0]{desc} = $_[1] if @_ > 1; 637 $_[0]{desc} = $_[1] if @_ > 1;
500 $old; 638 $old;
501} 639}
502 640
641sub transfer {
642 require Carp;
643 Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
644}
645
503=back 646=back
504 647
505=head2 GLOBAL FUNCTIONS 648=head1 GLOBAL FUNCTIONS
506 649
507=over 4 650=over 4
508 651
509=item Coro::nready 652=item Coro::nready
510 653
511Returns the number of coroutines that are currently in the ready state, 654Returns the number of coro that are currently in the ready state,
512i.e. that can be switched to. The value C<0> means that the only runnable 655i.e. that can be switched to by calling C<schedule> directory or
656indirectly. The value C<0> means that the only runnable coro is the
513coroutine is the currently running one, so C<cede> would have no effect, 657currently running one, so C<cede> would have no effect, and C<schedule>
514and C<schedule> would cause a deadlock unless there is an idle handler 658would cause a deadlock unless there is an idle handler that wakes up some
515that wakes up some coroutines. 659coro.
516 660
517=item my $guard = Coro::guard { ... } 661=item my $guard = Coro::guard { ... }
518 662
519This creates and returns a guard object. Nothing happens until the object 663This function still exists, but is deprecated. Please use the
520gets destroyed, in which case the codeblock given as argument will be 664C<Guard::guard> function instead.
521executed. This is useful to free locks or other resources in case of a
522runtime error or when the coroutine gets canceled, as in both cases the
523guard block will be executed. The guard object supports only one method,
524C<< ->cancel >>, which will keep the codeblock from being executed.
525 665
526Example: set some flag and clear it again when the coroutine gets canceled
527or the function returns:
528
529 sub do_something {
530 my $guard = Coro::guard { $busy = 0 };
531 $busy = 1;
532
533 # do something that requires $busy to be true
534 }
535
536=cut 666=cut
537 667
538sub guard(&) { 668BEGIN { *guard = \&Guard::guard }
539 bless \(my $cb = $_[0]), "Coro::guard"
540}
541
542sub Coro::guard::cancel {
543 ${$_[0]} = sub { };
544}
545
546sub Coro::guard::DESTROY {
547 ${$_[0]}->();
548}
549
550 669
551=item unblock_sub { ... } 670=item unblock_sub { ... }
552 671
553This utility function takes a BLOCK or code reference and "unblocks" it, 672This utility function takes a BLOCK or code reference and "unblocks" it,
554returning the new coderef. This means that the new coderef will return 673returning a new coderef. Unblocking means that calling the new coderef
555immediately without blocking, returning nothing, while the original code 674will return immediately without blocking, returning nothing, while the
556ref will be called (with parameters) from within its own coroutine. 675original code ref will be called (with parameters) from within another
676coro.
557 677
558The reason this function exists is that many event libraries (such as the 678The reason this function exists is that many event libraries (such as the
559venerable L<Event|Event> module) are not coroutine-safe (a weaker form 679venerable L<Event|Event> module) are not thread-safe (a weaker form
560of thread-safety). This means you must not block within event callbacks, 680of reentrancy). This means you must not block within event callbacks,
561otherwise you might suffer from crashes or worse. 681otherwise you might suffer from crashes or worse. The only event library
682currently known that is safe to use without C<unblock_sub> is L<EV>.
562 683
563This function allows your callbacks to block by executing them in another 684This function allows your callbacks to block by executing them in another
564coroutine where it is safe to block. One example where blocking is handy 685coro where it is safe to block. One example where blocking is handy
565is when you use the L<Coro::AIO|Coro::AIO> functions to save results to 686is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
566disk. 687disk, for example.
567 688
568In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when 689In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
569creating event callbacks that want to block. 690creating event callbacks that want to block.
691
692If your handler does not plan to block (e.g. simply sends a message to
693another coro, or puts some other coro into the ready queue), there is
694no reason to use C<unblock_sub>.
695
696Note that you also need to use C<unblock_sub> for any other callbacks that
697are indirectly executed by any C-based event loop. For example, when you
698use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
699provides callbacks that are the result of some event callback, then you
700must not block either, or use C<unblock_sub>.
570 701
571=cut 702=cut
572 703
573our @unblock_queue; 704our @unblock_queue;
574 705
577# return immediately and can be reused) and because we cannot cede 708# return immediately and can be reused) and because we cannot cede
578# inside an event callback. 709# inside an event callback.
579our $unblock_scheduler = new Coro sub { 710our $unblock_scheduler = new Coro sub {
580 while () { 711 while () {
581 while (my $cb = pop @unblock_queue) { 712 while (my $cb = pop @unblock_queue) {
582 # this is an inlined copy of async_pool 713 &async_pool (@$cb);
583 my $coro = (pop @async_pool) || new Coro \&pool_handler;
584 714
585 $coro->{_invoke} = $cb;
586 $coro->ready;
587 cede; # for short-lived callbacks, this reduces pressure on the coro pool 715 # for short-lived callbacks, this reduces pressure on the coro pool
716 # as the chance is very high that the async_poll coro will be back
717 # in the idle state when cede returns
718 cede;
588 } 719 }
589 schedule; # sleep well 720 schedule; # sleep well
590 } 721 }
591}; 722};
592$unblock_scheduler->desc ("[unblock_sub scheduler]"); 723$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
593 724
594sub unblock_sub(&) { 725sub unblock_sub(&) {
595 my $cb = shift; 726 my $cb = shift;
596 727
597 sub { 728 sub {
598 unshift @unblock_queue, [$cb, @_]; 729 unshift @unblock_queue, [$cb, @_];
599 $unblock_scheduler->ready; 730 $unblock_scheduler->ready;
600 } 731 }
601} 732}
602 733
734=item $cb = Coro::rouse_cb
735
736Create and return a "rouse callback". That's a code reference that,
737when called, will remember a copy of its arguments and notify the owner
738coro of the callback.
739
740See the next function.
741
742=item @args = Coro::rouse_wait [$cb]
743
744Wait for the specified rouse callback (or the last one that was created in
745this coro).
746
747As soon as the callback is invoked (or when the callback was invoked
748before C<rouse_wait>), it will return the arguments originally passed to
749the rouse callback. In scalar context, that means you get the I<last>
750argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
751statement at the end.
752
753See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
754
603=back 755=back
604 756
605=cut 757=cut
606 758
6071; 7591;
608 760
761=head1 HOW TO WAIT FOR A CALLBACK
762
763It is very common for a coro to wait for some callback to be
764called. This occurs naturally when you use coro in an otherwise
765event-based program, or when you use event-based libraries.
766
767These typically register a callback for some event, and call that callback
768when the event occured. In a coro, however, you typically want to
769just wait for the event, simplyifying things.
770
771For example C<< AnyEvent->child >> registers a callback to be called when
772a specific child has exited:
773
774 my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
775
776But from within a coro, you often just want to write this:
777
778 my $status = wait_for_child $pid;
779
780Coro offers two functions specifically designed to make this easy,
781C<Coro::rouse_cb> and C<Coro::rouse_wait>.
782
783The first function, C<rouse_cb>, generates and returns a callback that,
784when invoked, will save its arguments and notify the coro that
785created the callback.
786
787The second function, C<rouse_wait>, waits for the callback to be called
788(by calling C<schedule> to go to sleep) and returns the arguments
789originally passed to the callback.
790
791Using these functions, it becomes easy to write the C<wait_for_child>
792function mentioned above:
793
794 sub wait_for_child($) {
795 my ($pid) = @_;
796
797 my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
798
799 my ($rpid, $rstatus) = Coro::rouse_wait;
800 $rstatus
801 }
802
803In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
804you can roll your own, using C<schedule>:
805
806 sub wait_for_child($) {
807 my ($pid) = @_;
808
809 # store the current coro in $current,
810 # and provide result variables for the closure passed to ->child
811 my $current = $Coro::current;
812 my ($done, $rstatus);
813
814 # pass a closure to ->child
815 my $watcher = AnyEvent->child (pid => $pid, cb => sub {
816 $rstatus = $_[1]; # remember rstatus
817 $done = 1; # mark $rstatus as valud
818 });
819
820 # wait until the closure has been called
821 schedule while !$done;
822
823 $rstatus
824 }
825
826
609=head1 BUGS/LIMITATIONS 827=head1 BUGS/LIMITATIONS
610 828
611 - you must make very sure that no coro is still active on global 829=over 4
612 destruction. very bad things might happen otherwise (usually segfaults).
613 830
831=item fork with pthread backend
832
833When Coro is compiled using the pthread backend (which isn't recommended
834but required on many BSDs as their libcs are completely broken), then
835coro will not survive a fork. There is no known workaround except to
836fix your libc and use a saner backend.
837
838=item perl process emulation ("threads")
839
614 - this module is not thread-safe. You should only ever use this module 840This module is not perl-pseudo-thread-safe. You should only ever use this
615 from the same thread (this requirement might be loosened in the future 841module from the first thread (this requirement might be removed in the
616 to allow per-thread schedulers, but Coro::State does not yet allow 842future to allow per-thread schedulers, but Coro::State does not yet allow
617 this). 843this). I recommend disabling thread support and using processes, as having
844the windows process emulation enabled under unix roughly halves perl
845performance, even when not used.
846
847=item coro switching is not signal safe
848
849You must not switch to another coro from within a signal handler
850(only relevant with %SIG - most event libraries provide safe signals).
851
852That means you I<MUST NOT> call any function that might "block" the
853current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
854anything that calls those. Everything else, including calling C<ready>,
855works.
856
857=back
858
859
860=head1 WINDOWS PROCESS EMULATION
861
862A great many people seem to be confused about ithreads (for example, Chip
863Salzenberg called me unintelligent, incapable, stupid and gullible,
864while in the same mail making rather confused statements about perl
865ithreads (for example, that memory or files would be shared), showing his
866lack of understanding of this area - if it is hard to understand for Chip,
867it is probably not obvious to everybody).
868
869What follows is an ultra-condensed version of my talk about threads in
870scripting languages given onthe perl workshop 2009:
871
872The so-called "ithreads" were originally implemented for two reasons:
873first, to (badly) emulate unix processes on native win32 perls, and
874secondly, to replace the older, real thread model ("5.005-threads").
875
876It does that by using threads instead of OS processes. The difference
877between processes and threads is that threads share memory (and other
878state, such as files) between threads within a single process, while
879processes do not share anything (at least not semantically). That
880means that modifications done by one thread are seen by others, while
881modifications by one process are not seen by other processes.
882
883The "ithreads" work exactly like that: when creating a new ithreads
884process, all state is copied (memory is copied physically, files and code
885is copied logically). Afterwards, it isolates all modifications. On UNIX,
886the same behaviour can be achieved by using operating system processes,
887except that UNIX typically uses hardware built into the system to do this
888efficiently, while the windows process emulation emulates this hardware in
889software (rather efficiently, but of course it is still much slower than
890dedicated hardware).
891
892As mentioned before, loading code, modifying code, modifying data
893structures and so on is only visible in the ithreads process doing the
894modification, not in other ithread processes within the same OS process.
895
896This is why "ithreads" do not implement threads for perl at all, only
897processes. What makes it so bad is that on non-windows platforms, you can
898actually take advantage of custom hardware for this purpose (as evidenced
899by the forks module, which gives you the (i-) threads API, just much
900faster).
901
902Sharing data is in the i-threads model is done by transfering data
903structures between threads using copying semantics, which is very slow -
904shared data simply does not exist. Benchmarks using i-threads which are
905communication-intensive show extremely bad behaviour with i-threads (in
906fact, so bad that Coro, which cannot take direct advantage of multiple
907CPUs, is often orders of magnitude faster because it shares data using
908real threads, refer to my talk for details).
909
910As summary, i-threads *use* threads to implement processes, while
911the compatible forks module *uses* processes to emulate, uhm,
912processes. I-threads slow down every perl program when enabled, and
913outside of windows, serve no (or little) practical purpose, but
914disadvantages every single-threaded Perl program.
915
916This is the reason that I try to avoid the name "ithreads", as it is
917misleading as it implies that it implements some kind of thread model for
918perl, and prefer the name "windows process emulation", which describes the
919actual use and behaviour of it much better.
618 920
619=head1 SEE ALSO 921=head1 SEE ALSO
620 922
621Lower level Configuration, Coroutine Environment: L<Coro::State>. 923Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
622 924
623Debugging: L<Coro::Debug>. 925Debugging: L<Coro::Debug>.
624 926
625Support/Utility: L<Coro::Specific>, L<Coro::Util>. 927Support/Utility: L<Coro::Specific>, L<Coro::Util>.
626 928
627Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. 929Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
930L<Coro::SemaphoreSet>, L<Coro::RWLock>.
628 931
629Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>. 932I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
630 933
631Compatibility: L<Coro::LWP>, L<Coro::Storable>, L<Coro::Select>. 934Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
935a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
936L<Coro::Select>.
632 937
633Embedding: L<Coro::MakeMaker>. 938XS API: L<Coro::MakeMaker>.
939
940Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
634 941
635=head1 AUTHOR 942=head1 AUTHOR
636 943
637 Marc Lehmann <schmorp@schmorp.de> 944 Marc Lehmann <schmorp@schmorp.de>
638 http://home.schmorp.de/ 945 http://home.schmorp.de/

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