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… …
2 2
3Coro - coroutine process abstraction 3Coro - coroutine process abstraction
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 coroutine
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 my $lock = new Coro::Semaphore; 21 my $lock = new Coro::Semaphore;
22 my $locked; 22 my $locked;
23 23
24 $lock->down; 24 $lock->down;
25 $locked = 1; 25 $locked = 1;
26 $lock->up; 26 $lock->up;
27 27
28=head1 DESCRIPTION 28=head1 DESCRIPTION
29 29
30This module collection manages coroutines. Coroutines are similar 30This module collection manages coroutines. Coroutines are similar to
31to threads but don't run in parallel at the same time even on SMP 31threads but don't (in general) run in parallel at the same time even
32machines. The specific flavor of coroutine used in this module also 32on SMP machines. The specific flavor of coroutine used in this module
33guarantees you that it will not switch between coroutines unless 33also guarantees you that it will not switch between coroutines unless
34necessary, at easily-identified points in your program, so locking and 34necessary, at easily-identified points in your program, so locking and
35parallel access are rarely an issue, making coroutine programming much 35parallel access are rarely an issue, making coroutine programming much
36safer than threads programming. 36safer and easier than threads programming.
37 37
38(Perl, however, does not natively support real threads but instead does a 38Unlike a normal perl program, however, coroutines allow you to have
39very slow and memory-intensive emulation of processes using threads. This 39multiple running interpreters that share data, which is especially useful
40is a performance win on Windows machines, and a loss everywhere else). 40to code pseudo-parallel processes, such as multiple HTTP-GET requests
41running concurrently.
42
43Coroutines are also useful because Perl has no support for threads (the so
44called "threads" that perl offers are nothing more than the (bad) process
45emulation coming from the Windows platform: On standard operating systems
46they serve no purpose whatsoever, except by making your programs slow and
47making them use a lot of memory. Best disable them when building perl, or
48aks your software vendor/distributor to do it for you).
41 49
42In this module, coroutines are defined as "callchain + lexical variables + 50In this module, coroutines are defined as "callchain + lexical variables +
43@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain, 51@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
44its own set of lexicals and its own set of perls most important global 52its own set of lexicals and its own set of perls most important global
45variables (see L<Coro::State> for more configuration). 53variables (see L<Coro::State> for more configuration).
… …
57 65
58our $idle; # idle handler 66our $idle; # idle handler
59our $main; # main coroutine 67our $main; # main coroutine
60our $current; # current coroutine 68our $current; # current coroutine
61 69
62our $VERSION = '4.51'; 70our $VERSION = 4.6;
63 71
64our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); 72our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
65our %EXPORT_TAGS = ( 73our %EXPORT_TAGS = (
66 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 74 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
67); 75);
68our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); 76our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
69 77
70{
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
104=over 4 78=over 4
105 79
106=item $main 80=item $Coro::main
107 81
108This coroutine represents the main program. 82This variable stores the coroutine object that represents the main
83program. While you cna C<ready> it and do most other things you can do to
84coroutines, it is mainly useful to compare again C<$Coro::current>, to see
85wether you are running in the main program or not.
109 86
110=cut 87=cut
111 88
112$main = new Coro; 89$main = new Coro;
113 90
114=item $current (or as function: current) 91=item $Coro::current
115 92
116The current coroutine (the last coroutine switched to). The initial value 93The coroutine object representing the current coroutine (the last
94coroutine that the Coro scheduler switched to). The initial value is
117is C<$main> (of course). 95C<$main> (of course).
118 96
119This variable is B<strictly> I<read-only>. It is provided for performance 97This variable is B<strictly> I<read-only>. You can take copies of the
120reasons. If performance is not essential you are encouraged to use the 98value stored in it and use it as any other coroutine object, but you must
121C<Coro::current> function instead. 99not otherwise modify the variable itself.
122 100
123=cut 101=cut
124 102
125$main->{desc} = "[main::]"; 103$main->{desc} = "[main::]";
126 104
… …
128$main->{_specific} = $current->{_specific} 106$main->{_specific} = $current->{_specific}
129 if $current; 107 if $current;
130 108
131_set_current $main; 109_set_current $main;
132 110
133sub current() { $current } 111sub current() { $current } # [DEPRECATED]
134 112
135=item $idle 113=item $Coro::idle
136 114
137A callback that is called whenever the scheduler finds no ready coroutines 115This variable is mainly useful to integrate Coro into event loops. It is
138to run. The default implementation prints "FATAL: deadlock detected" and 116usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is
139exits, because the program has no other way to continue. 117pretty low-level functionality.
118
119This variable stores a callback that is called whenever the scheduler
120finds no ready coroutines to run. The default implementation prints
121"FATAL: deadlock detected" and exits, because the program has no other way
122to continue.
140 123
141This hook is overwritten by modules such as C<Coro::Timer> and 124This hook is overwritten by modules such as C<Coro::Timer> and
142C<Coro::Event> to wait on an external event that hopefully wake up a 125C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
143coroutine so the scheduler can run it. 126coroutine so the scheduler can run it.
127
128Note that the callback I<must not>, under any circumstances, block
129the current coroutine. Normally, this is achieved by having an "idle
130coroutine" that calls the event loop and then blocks again, and then
131readying that coroutine in the idle handler.
132
133See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
134technique.
144 135
145Please note that if your callback recursively invokes perl (e.g. for event 136Please note that if your callback recursively invokes perl (e.g. for event
146handlers), then it must be prepared to be called recursively itself. 137handlers), then it must be prepared to be called recursively itself.
147 138
148=cut 139=cut
… …
180$manager->desc ("[coro manager]"); 171$manager->desc ("[coro manager]");
181$manager->prio (PRIO_MAX); 172$manager->prio (PRIO_MAX);
182 173
183=back 174=back
184 175
185=head2 STATIC METHODS 176=head2 SIMPLE COROUTINE CREATION
186
187Static methods are actually functions that operate on the current coroutine only.
188 177
189=over 4 178=over 4
190 179
191=item async { ... } [@args...] 180=item async { ... } [@args...]
192 181
193Create a new asynchronous coroutine and return it's coroutine object 182Create a new coroutine and return it's coroutine object (usually
194(usually unused). When the sub returns the new coroutine is automatically 183unused). The coroutine will be put into the ready queue, so
184it will start running automatically on the next scheduler run.
185
186The first argument is a codeblock/closure that should be executed in the
187coroutine. When it returns argument returns the coroutine is automatically
195terminated. 188terminated.
196 189
190The remaining arguments are passed as arguments to the closure.
191
197See the C<Coro::State::new> constructor for info about the coroutine 192See the C<Coro::State::new> constructor for info about the coroutine
198environment in which coroutines run. 193environment in which coroutines are executed.
199 194
200Calling C<exit> in a coroutine will do the same as calling exit outside 195Calling C<exit> in a coroutine will do the same as calling exit outside
201the coroutine. Likewise, when the coroutine dies, the program will exit, 196the coroutine. Likewise, when the coroutine dies, the program will exit,
202just as it would in the main program. 197just as it would in the main program.
203 198
199If you do not want that, you can provide a default C<die> handler, or
200simply avoid dieing (by use of C<eval>).
201
204 # create a new coroutine that just prints its arguments 202Example: Create a new coroutine that just prints its arguments.
203
205 async { 204 async {
206 print "@_\n"; 205 print "@_\n";
207 } 1,2,3,4; 206 } 1,2,3,4;
208 207
209=cut 208=cut
… …
215} 214}
216 215
217=item async_pool { ... } [@args...] 216=item async_pool { ... } [@args...]
218 217
219Similar to C<async>, but uses a coroutine pool, so you should not call 218Similar to C<async>, but uses a coroutine pool, so you should not call
220terminate or join (although you are allowed to), and you get a coroutine 219terminate or join on it (although you are allowed to), and you get a
221that might have executed other code already (which can be good or bad :). 220coroutine that might have executed other code already (which can be good
221or bad :).
222 222
223On the plus side, this function is faster than creating (and destroying)
224a completely new coroutine, so if you need a lot of generic coroutines in
225quick successsion, use C<async_pool>, not C<async>.
226
223Also, the block is executed in an C<eval> context and a warning will be 227The code block is executed in an C<eval> context and a warning will be
224issued in case of an exception instead of terminating the program, as 228issued in case of an exception instead of terminating the program, as
225C<async> does. As the coroutine is being reused, stuff like C<on_destroy> 229C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
226will not work in the expected way, unless you call terminate or cancel, 230will not work in the expected way, unless you call terminate or cancel,
227which somehow defeats the purpose of pooling. 231which somehow defeats the purpose of pooling (but is fine in the
232exceptional case).
228 233
229The priority will be reset to C<0> after each job, tracing will be 234The priority will be reset to C<0> after each run, tracing will be
230disabled, the description will be reset and the default output filehandle 235disabled, the description will be reset and the default output filehandle
231gets restored, so you can change alkl these. Otherwise the coroutine will 236gets restored, so you can change all these. Otherwise the coroutine will
232be re-used "as-is": most notably if you change other per-coroutine global 237be re-used "as-is": most notably if you change other per-coroutine global
233stuff such as C<$/> you need to revert that change, which is most simply 238stuff such as C<$/> you I<must needs> to revert that change, which is most
234done by using local as in C< local $/ >. 239simply done by using local as in: C< local $/ >.
235 240
236The pool size is limited to 8 idle coroutines (this can be adjusted by 241The pool size is limited to C<8> idle coroutines (this can be adjusted by
237changing $Coro::POOL_SIZE), and there can be as many non-idle coros as 242changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
238required. 243required.
239 244
240If you are concerned about pooled coroutines growing a lot because a 245If you are concerned about pooled coroutines growing a lot because a
241single C<async_pool> used a lot of stackspace you can e.g. C<async_pool 246single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
242{ terminate }> once per second or so to slowly replenish the pool. In 247{ terminate }> once per second or so to slowly replenish the pool. In
243addition to that, when the stacks used by a handler grows larger than 16kb 248addition to that, when the stacks used by a handler grows larger than 16kb
244(adjustable with $Coro::POOL_RSS) it will also exit. 249(adjustable via $Coro::POOL_RSS) it will also be destroyed.
245 250
246=cut 251=cut
247 252
248our $POOL_SIZE = 8; 253our $POOL_SIZE = 8;
249our $POOL_RSS = 16 * 1024; 254our $POOL_RSS = 16 * 1024;
… …
275 $coro->ready; 280 $coro->ready;
276 281
277 $coro 282 $coro
278} 283}
279 284
285=back
286
287=head2 STATIC METHODS
288
289Static methods are actually functions that operate on the current coroutine.
290
291=over 4
292
280=item schedule 293=item schedule
281 294
282Calls the scheduler. Please note that the current coroutine will not be put 295Calls the scheduler. The scheduler will find the next coroutine that is
296to be run from the ready queue and switches to it. The next coroutine
297to be run is simply the one with the highest priority that is longest
298in its ready queue. If there is no coroutine ready, it will clal the
299C<$Coro::idle> hook.
300
301Please note that the current coroutine will I<not> be put into the ready
283into the ready queue, so calling this function usually means you will 302queue, so calling this function usually means you will never be called
284never be called again unless something else (e.g. an event handler) calls 303again unless something else (e.g. an event handler) calls C<< ->ready >>,
285ready. 304thus waking you up.
305
306This 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
308a 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
310yourself to sleep. Note that a lot of things can wake your coroutine up,
311so you need to check wether the event indeed happened, e.g. by storing the
312status in a variable.
286 313
287The canonical way to wait on external events is this: 314The canonical way to wait on external events is this:
288 315
289 { 316 {
290 # remember current coroutine 317 # remember current coroutine
… …
303 Coro::schedule while $current; 330 Coro::schedule while $current;
304 } 331 }
305 332
306=item cede 333=item cede
307 334
308"Cede" to other coroutines. This function puts the current coroutine into the 335"Cede" to other coroutines. This function puts the current coroutine into
309ready queue and calls C<schedule>, which has the effect of giving up the 336the ready queue and calls C<schedule>, which has the effect of giving
310current "timeslice" to other coroutines of the same or higher priority. 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
341This function is often called C<yield> in other languages.
311 342
312=item Coro::cede_notself 343=item Coro::cede_notself
313 344
314Works like cede, but is not exported by default and will cede to any 345Works like cede, but is not exported by default and will cede to I<any>
315coroutine, regardless of priority, once. 346coroutine, regardless of priority. This is useful sometimes to ensure
347progress is made.
316 348
317=item terminate [arg...] 349=item terminate [arg...]
318 350
319Terminates the current coroutine with the given status values (see L<cancel>). 351Terminates the current coroutine with the given status values (see L<cancel>).
320 352
321=item killall 353=item killall
322 354
323Kills/terminates/cancels all coroutines except the currently running 355Kills/terminates/cancels all coroutines except the currently running
324one. This is useful after a fork, either in the child or the parent, as 356one. This is useful after a fork, either in the child or the parent, as
325usually only one of them should inherit the running coroutines. 357usually only one of them should inherit the running coroutines.
358
359Note that while this will try to free some of the main programs resources,
360you cnanot free all of them, so if a coroutine that is not the main
361program calls this function, there will be some one-time resource leak.
326 362
327=cut 363=cut
328 364
329sub terminate { 365sub terminate {
330 $current->cancel (@_); 366 $current->cancel (@_);
… …
339 375
340=back 376=back
341 377
342=head2 COROUTINE METHODS 378=head2 COROUTINE METHODS
343 379
344These are the methods you can call on coroutine objects. 380These are the methods you can call on coroutine objects (or to create
381them).
345 382
346=over 4 383=over 4
347 384
348=item new Coro \&sub [, @args...] 385=item new Coro \&sub [, @args...]
349 386
350Create a new coroutine and return it. When the sub returns the coroutine 387Create a new coroutine and return it. When the sub returns, the coroutine
351automatically terminates as if C<terminate> with the returned values were 388automatically terminates as if C<terminate> with the returned values were
352called. To make the coroutine run you must first put it into the ready queue 389called. To make the coroutine run you must first put it into the ready
353by calling the ready method. 390queue by calling the ready method.
354 391
355See C<async> and C<Coro::State::new> for additional info about the 392See C<async> and C<Coro::State::new> for additional info about the
356coroutine environment. 393coroutine environment.
357 394
358=cut 395=cut
… …
367 $class->SUPER::new (\&_run_coro, @_) 404 $class->SUPER::new (\&_run_coro, @_)
368} 405}
369 406
370=item $success = $coroutine->ready 407=item $success = $coroutine->ready
371 408
372Put the given coroutine into the ready queue (according to it's priority) 409Put the given coroutine into the end of its ready queue (there is one
373and return true. If the coroutine is already in the ready queue, do nothing 410queue for each priority) and return true. If the coroutine is already in
374and return false. 411the ready queue, do nothing and return false.
412
413This ensures that the scheduler will resume this coroutine automatically
414once all the coroutines of higher priority and all coroutines of the same
415priority that were put into the ready queue earlier have been resumed.
375 416
376=item $is_ready = $coroutine->is_ready 417=item $is_ready = $coroutine->is_ready
377 418
378Return wether the coroutine is currently the ready queue or not, 419Return wether the coroutine is currently the ready queue or not,
379 420
… …
400 441
401=item $coroutine->join 442=item $coroutine->join
402 443
403Wait until the coroutine terminates and return any values given to the 444Wait until the coroutine terminates and return any values given to the
404C<terminate> or C<cancel> functions. C<join> can be called concurrently 445C<terminate> or C<cancel> functions. C<join> can be called concurrently
405from multiple coroutines. 446from multiple coroutines, and all will be resumed and given the status
447return once the C<$coroutine> terminates.
406 448
407=cut 449=cut
408 450
409sub join { 451sub join {
410 my $self = shift; 452 my $self = shift;
… …
425 467
426=item $coroutine->on_destroy (\&cb) 468=item $coroutine->on_destroy (\&cb)
427 469
428Registers a callback that is called when this coroutine gets destroyed, 470Registers a callback that is called when this coroutine gets destroyed,
429but before it is joined. The callback gets passed the terminate arguments, 471but before it is joined. The callback gets passed the terminate arguments,
430if any. 472if any, and I<must not> die, under any circumstances.
431 473
432=cut 474=cut
433 475
434sub on_destroy { 476sub on_destroy {
435 my ($self, $cb) = @_; 477 my ($self, $cb) = @_;
… …
503=over 4 545=over 4
504 546
505=item Coro::nready 547=item Coro::nready
506 548
507Returns the number of coroutines that are currently in the ready state, 549Returns the number of coroutines that are currently in the ready state,
508i.e. that can be switched to. The value C<0> means that the only runnable 550i.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
509coroutine is the currently running one, so C<cede> would have no effect, 552currently running one, so C<cede> would have no effect, and C<schedule>
510and C<schedule> would cause a deadlock unless there is an idle handler 553would cause a deadlock unless there is an idle handler that wakes up some
511that wakes up some coroutines. 554coroutines.
512 555
513=item my $guard = Coro::guard { ... } 556=item my $guard = Coro::guard { ... }
514 557
515This creates and returns a guard object. Nothing happens until the object 558This creates and returns a guard object. Nothing happens until the object
516gets destroyed, in which case the codeblock given as argument will be 559gets destroyed, in which case the codeblock given as argument will be
… …
545 588
546 589
547=item unblock_sub { ... } 590=item unblock_sub { ... }
548 591
549This utility function takes a BLOCK or code reference and "unblocks" it, 592This utility function takes a BLOCK or code reference and "unblocks" it,
550returning the new coderef. This means that the new coderef will return 593returning a new coderef. Unblocking means that calling the new coderef
551immediately without blocking, returning nothing, while the original code 594will return immediately without blocking, returning nothing, while the
552ref will be called (with parameters) from within its own coroutine. 595original code ref will be called (with parameters) from within another
596coroutine.
553 597
554The reason this function exists is that many event libraries (such as the 598The reason this function exists is that many event libraries (such as the
555venerable L<Event|Event> module) are not coroutine-safe (a weaker form 599venerable L<Event|Event> module) are not coroutine-safe (a weaker form
556of thread-safety). This means you must not block within event callbacks, 600of thread-safety). This means you must not block within event callbacks,
557otherwise you might suffer from crashes or worse. 601otherwise 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>.
558 603
559This function allows your callbacks to block by executing them in another 604This function allows your callbacks to block by executing them in another
560coroutine where it is safe to block. One example where blocking is handy 605coroutine where it is safe to block. One example where blocking is handy
561is when you use the L<Coro::AIO|Coro::AIO> functions to save results to 606is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
562disk. 607disk, for example.
563 608
564In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when 609In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
565creating event callbacks that want to block. 610creating event callbacks that want to block.
611
612If 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),
614there is no reason to use C<unblock_sub>.
566 615
567=cut 616=cut
568 617
569our @unblock_queue; 618our @unblock_queue;
570 619
… …
602 651
6031; 6521;
604 653
605=head1 BUGS/LIMITATIONS 654=head1 BUGS/LIMITATIONS
606 655
607 - you must make very sure that no coro is still active on global
608 destruction. very bad things might happen otherwise (usually segfaults).
609
610 - this module is not thread-safe. You should only ever use this module 656This module is not perl-pseudo-thread-safe. You should only ever use this
611 from the same thread (this requirement might be loosened in the future 657module from the same thread (this requirement might be removed in the
612 to allow per-thread schedulers, but Coro::State does not yet allow 658future to allow per-thread schedulers, but Coro::State does not yet allow
613 this). 659this). I recommend disabling thread support and using processes, as this
660is much faster and uses less memory.
614 661
615=head1 SEE ALSO 662=head1 SEE ALSO
616 663
617Lower level Configuration, Coroutine Environment: L<Coro::State>. 664Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
618 665
619Debugging: L<Coro::Debug>. 666Debugging: L<Coro::Debug>.
620 667
621Support/Utility: L<Coro::Specific>, L<Coro::Util>. 668Support/Utility: L<Coro::Specific>, L<Coro::Util>.
622 669
623Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. 670Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
624 671
625Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>. 672IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
626 673
627Compatibility: L<Coro::LWP>, L<Coro::Storable>, L<Coro::Select>. 674Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.
628 675
629Embedding: L<Coro::MakeMaker>. 676XS API: L<Coro::MakeMaker>.
677
678Low level Configuration, Coroutine Environment: L<Coro::State>.
630 679
631=head1 AUTHOR 680=head1 AUTHOR
632 681
633 Marc Lehmann <schmorp@schmorp.de> 682 Marc Lehmann <schmorp@schmorp.de>
634 http://home.schmorp.de/ 683 http://home.schmorp.de/

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