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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 = '4.2'; 86our $VERSION = 5.25;
63 87
64our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); 88our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
65our %EXPORT_TAGS = ( 89our %EXPORT_TAGS = (
66 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 90 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
67); 91);
68our @EXPORT_OK = (@{$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 $Coro::idle
136 124
137A callback that is called whenever the scheduler finds no ready coroutines 125This variable is mainly useful to integrate Coro into event loops. It is
126usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
127pretty low-level functionality.
128
129This variable stores a Coro object that is put into the ready queue when
130there are no other ready threads (without invoking any ready hooks).
131
138to run. The default implementation prints "FATAL: deadlock detected" and 132The default implementation dies with "FATAL: deadlock detected.", followed
139exits, because the program has no other way to continue. 133by a thread listing, because the program has no other way to continue.
140 134
141This hook is overwritten by modules such as C<Coro::Timer> and 135This hook is overwritten by modules such as C<Coro::EV> and
142C<Coro::Event> to wait on an external event that hopefully wake up a 136C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
143coroutine so the scheduler can run it. 137coro so the scheduler can run it.
144 138
145Please note that if your callback recursively invokes perl (e.g. for event 139See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
146handlers), then it must be prepared to be called recursively itself.
147 140
148=cut 141=cut
149 142
150$idle = sub { 143# ||= because other modules could have provided their own by now
151 require Carp; 144$idle ||= new Coro sub {
152 Carp::croak ("FATAL: deadlock detected"); 145 require Coro::Debug;
146 die "FATAL: deadlock detected.\n"
147 . Coro::Debug::ps_listing ();
153}; 148};
154 149
155sub _cancel {
156 my ($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 150# this coro is necessary because a coro
168# cannot destroy itself. 151# cannot destroy itself.
169my @destroy; 152our @destroy;
170my $manager; 153our $manager;
171 154
172$manager = new Coro sub { 155$manager = new Coro sub {
173 while () { 156 while () {
174 (shift @destroy)->_cancel 157 Coro::State::cancel shift @destroy
175 while @destroy; 158 while @destroy;
176 159
177 &schedule; 160 &schedule;
178 } 161 }
179}; 162};
180$manager->desc ("[coro manager]"); 163$manager->{desc} = "[coro manager]";
181$manager->prio (PRIO_MAX); 164$manager->prio (PRIO_MAX);
182 165
183# static methods. not really.
184
185=back 166=back
186 167
187=head2 STATIC METHODS 168=head1 SIMPLE CORO CREATION
188
189Static methods are actually functions that operate on the current coroutine only.
190 169
191=over 4 170=over 4
192 171
193=item async { ... } [@args...] 172=item async { ... } [@args...]
194 173
195Create a new asynchronous coroutine and return it's coroutine object 174Create a new coro and return its Coro object (usually
196(usually unused). When the sub returns the new coroutine is automatically 175unused). The coro will be put into the ready queue, so
176it will start running automatically on the next scheduler run.
177
178The first argument is a codeblock/closure that should be executed in the
179coro. When it returns argument returns the coro is automatically
197terminated. 180terminated.
198 181
182The remaining arguments are passed as arguments to the closure.
183
199See the C<Coro::State::new> constructor for info about the coroutine 184See the C<Coro::State::new> constructor for info about the coro
200environment in which coroutines run. 185environment in which coro are executed.
201 186
202Calling C<exit> in a coroutine will do the same as calling exit outside 187Calling C<exit> in a coro will do the same as calling exit outside
203the coroutine. Likewise, when the coroutine dies, the program will exit, 188the coro. Likewise, when the coro dies, the program will exit,
204just as it would in the main program. 189just as it would in the main program.
205 190
191If you do not want that, you can provide a default C<die> handler, or
192simply avoid dieing (by use of C<eval>).
193
206 # create a new coroutine that just prints its arguments 194Example: Create a new coro that just prints its arguments.
195
207 async { 196 async {
208 print "@_\n"; 197 print "@_\n";
209 } 1,2,3,4; 198 } 1,2,3,4;
210 199
211=cut
212
213sub async(&@) {
214 my $coro = new Coro @_;
215 $coro->ready;
216 $coro
217}
218
219=item async_pool { ... } [@args...] 200=item async_pool { ... } [@args...]
220 201
221Similar to C<async>, but uses a coroutine pool, so you should not call 202Similar 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 203terminate 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 :). 204coro that might have executed other code already (which can be good
205or bad :).
224 206
207On the plus side, this function is about twice as fast as creating (and
208destroying) a completely new coro, so if you need a lot of generic
209coros in quick successsion, use C<async_pool>, not C<async>.
210
225Also, the block is executed in an C<eval> context and a warning will be 211The 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 212issued 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> 213C<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, 214will not work in the expected way, unless you call terminate or cancel,
229which somehow defeats the purpose of pooling. 215which somehow defeats the purpose of pooling (but is fine in the
216exceptional case).
230 217
231The priority will be reset to C<0> after each job, tracing will be 218The priority will be reset to C<0> after each run, tracing will be
232disabled, the description will be reset and the default output filehandle 219disabled, the description will be reset and the default output filehandle
233gets restored, so you can change alkl these. Otherwise the coroutine will 220gets 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 221be 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 222stuff such as C<$/> you I<must needs> revert that change, which is most
236done by using local as in C< local $/ >. 223simply done by using local as in: C<< local $/ >>.
237 224
238The pool size is limited to 8 idle coroutines (this can be adjusted by 225The 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 226adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
240required. 227coros as required.
241 228
242If you are concerned about pooled coroutines growing a lot because a 229If 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 230single 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 231{ 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 232addition to that, when the stacks used by a handler grows larger than 32kb
246(adjustable with $Coro::POOL_RSS) it will also exit. 233(adjustable via $Coro::POOL_RSS) it will also be destroyed.
247 234
248=cut 235=cut
249 236
250our $POOL_SIZE = 8; 237our $POOL_SIZE = 8;
251our $POOL_RSS = 16 * 1024; 238our $POOL_RSS = 32 * 1024;
252our @async_pool; 239our @async_pool;
253 240
254sub pool_handler { 241sub pool_handler {
255 my $cb;
256
257 while () { 242 while () {
258 eval { 243 eval {
259 while () { 244 &{&_pool_handler} while 1;
260 _pool_1 $cb;
261 &$cb;
262 _pool_2 $cb;
263 &schedule;
264 }
265 }; 245 };
266 246
267 last if $@ eq "\3async_pool terminate\2\n";
268 warn $@ if $@; 247 warn $@ if $@;
269 } 248 }
270} 249}
271 250
272sub async_pool(&@) { 251=back
273 # this is also inlined into the unlock_scheduler
274 my $coro = (pop @async_pool) || new Coro \&pool_handler;
275 252
276 $coro->{_invoke} = [@_]; 253=head1 STATIC METHODS
277 $coro->ready;
278 254
279 $coro 255Static methods are actually functions that implicitly operate on the
280} 256current coro.
257
258=over 4
281 259
282=item schedule 260=item schedule
283 261
284Calls the scheduler. Please note that the current coroutine will not be put 262Calls the scheduler. The scheduler will find the next coro that is
263to be run from the ready queue and switches to it. The next coro
264to be run is simply the one with the highest priority that is longest
265in its ready queue. If there is no coro ready, it will call the
266C<$Coro::idle> hook.
267
268Please 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 269queue, so calling this function usually means you will never be called
286never be called again unless something else (e.g. an event handler) calls 270again unless something else (e.g. an event handler) calls C<< ->ready >>,
287ready. 271thus waking you up.
288 272
289The canonical way to wait on external events is this: 273This makes C<schedule> I<the> generic method to use to block the current
274coro and wait for events: first you remember the current coro in
275a variable, then arrange for some callback of yours to call C<< ->ready
276>> on that once some event happens, and last you call C<schedule> to put
277yourself to sleep. Note that a lot of things can wake your coro up,
278so you need to check whether the event indeed happened, e.g. by storing the
279status in a variable.
290 280
291 { 281See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
292 # remember current coroutine
293 my $current = $Coro::current;
294 282
295 # register a hypothetical event handler 283=item cede
296 on_event_invoke sub { 284
297 # wake up sleeping coroutine 285"Cede" to other coros. This function puts the current coro into
298 $current->ready; 286the ready queue and calls C<schedule>, which has the effect of giving
299 undef $current; 287up the current "timeslice" to other coros of the same or higher
288priority. Once your coro gets its turn again it will automatically be
289resumed.
290
291This function is often called C<yield> in other languages.
292
293=item Coro::cede_notself
294
295Works like cede, but is not exported by default and will cede to I<any>
296coro, regardless of priority. This is useful sometimes to ensure
297progress is made.
298
299=item terminate [arg...]
300
301Terminates the current coro with the given status values (see L<cancel>).
302
303=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
304
305These function install enter and leave winders in the current scope. The
306enter block will be executed when on_enter is called and whenever the
307current coro is re-entered by the scheduler, while the leave block is
308executed whenever the current coro is blocked by the scheduler, and
309also when the containing scope is exited (by whatever means, be it exit,
310die, last etc.).
311
312I<Neither invoking the scheduler, nor exceptions, are allowed within those
313BLOCKs>. That means: do not even think about calling C<die> without an
314eval, and do not even think of entering the scheduler in any way.
315
316Since both BLOCKs are tied to the current scope, they will automatically
317be removed when the current scope exits.
318
319These functions implement the same concept as C<dynamic-wind> in scheme
320does, and are useful when you want to localise some resource to a specific
321coro.
322
323They slow down thread switching considerably for coros that use them
324(about 40% for a BLOCK with a single assignment, so thread switching is
325still reasonably fast if the handlers are fast).
326
327These functions are best understood by an example: The following function
328will change the current timezone to "Antarctica/South_Pole", which
329requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
330which remember/change the current timezone and restore the previous
331value, respectively, the timezone is only changed for the coro that
332installed those handlers.
333
334 use POSIX qw(tzset);
335
336 async {
337 my $old_tz; # store outside TZ value here
338
339 Coro::on_enter {
340 $old_tz = $ENV{TZ}; # remember the old value
341
342 $ENV{TZ} = "Antarctica/South_Pole";
343 tzset; # enable new value
300 }; 344 };
301 345
302 # call schedule until event occurred. 346 Coro::on_leave {
303 # in case we are woken up for other reasons 347 $ENV{TZ} = $old_tz;
304 # (current still defined), loop. 348 tzset; # restore old value
305 Coro::schedule while $current; 349 };
350
351 # at this place, the timezone is Antarctica/South_Pole,
352 # without disturbing the TZ of any other coro.
306 } 353 };
307 354
308=item cede 355This can be used to localise about any resource (locale, uid, current
356working directory etc.) to a block, despite the existance of other
357coros.
309 358
310"Cede" to other coroutines. This function puts the current coroutine into the 359Another interesting example implements time-sliced multitasking using
311ready queue and calls C<schedule>, which has the effect of giving up the 360interval timers (this could obviously be optimised, but does the job):
312current "timeslice" to other coroutines of the same or higher priority.
313 361
314=item Coro::cede_notself 362 # "timeslice" the given block
363 sub timeslice(&) {
364 use Time::HiRes ();
315 365
316Works like cede, but is not exported by default and will cede to any 366 Coro::on_enter {
317coroutine, regardless of priority, once. 367 # on entering the thread, we set an VTALRM handler to cede
368 $SIG{VTALRM} = sub { cede };
369 # and then start the interval timer
370 Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
371 };
372 Coro::on_leave {
373 # on leaving the thread, we stop the interval timer again
374 Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
375 };
318 376
319=item terminate [arg...] 377 &{+shift};
378 }
320 379
321Terminates the current coroutine with the given status values (see L<cancel>). 380 # use like this:
381 timeslice {
382 # The following is an endless loop that would normally
383 # monopolise the process. Since it runs in a timesliced
384 # environment, it will regularly cede to other threads.
385 while () { }
386 };
387
322 388
323=item killall 389=item killall
324 390
325Kills/terminates/cancels all coroutines except the currently running 391Kills/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.
328 392
329=cut 393Note that while this will try to free some of the main interpreter
394resources if the calling coro isn't the main coro, but one
395cannot free all of them, so if a coro that is not the main coro
396calls this function, there will be some one-time resource leak.
330 397
331sub terminate { 398=cut
332 $current->cancel (@_);
333}
334 399
335sub killall { 400sub killall {
336 for (Coro::State::list) { 401 for (Coro::State::list) {
337 $_->cancel 402 $_->cancel
338 if $_ != $current && UNIVERSAL::isa $_, "Coro"; 403 if $_ != $current && UNIVERSAL::isa $_, "Coro";
339 } 404 }
340} 405}
341 406
342=back 407=back
343 408
344# dynamic methods
345
346=head2 COROUTINE METHODS 409=head1 CORO OBJECT METHODS
347 410
348These are the methods you can call on coroutine objects. 411These are the methods you can call on coro objects (or to create
412them).
349 413
350=over 4 414=over 4
351 415
352=item new Coro \&sub [, @args...] 416=item new Coro \&sub [, @args...]
353 417
354Create a new coroutine and return it. When the sub returns the coroutine 418Create a new coro and return it. When the sub returns, the coro
355automatically terminates as if C<terminate> with the returned values were 419automatically 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 420called. To make the coro run you must first put it into the ready
357by calling the ready method. 421queue by calling the ready method.
358 422
359See C<async> and C<Coro::State::new> for additional info about the 423See C<async> and C<Coro::State::new> for additional info about the
360coroutine environment. 424coro environment.
361 425
362=cut 426=cut
363 427
364sub _run_coro { 428sub _coro_run {
365 terminate &{+shift}; 429 terminate &{+shift};
366} 430}
367 431
368sub new {
369 my $class = shift;
370
371 $class->SUPER::new (\&_run_coro, @_)
372}
373
374=item $success = $coroutine->ready 432=item $success = $coro->ready
375 433
376Put the given coroutine into the ready queue (according to it's priority) 434Put 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 435queue for each priority) and return true. If the coro is already in
378and return false. 436the ready queue, do nothing and return false.
379 437
438This ensures that the scheduler will resume this coro automatically
439once all the coro of higher priority and all coro of the same
440priority that were put into the ready queue earlier have been resumed.
441
442=item $coro->suspend
443
444Suspends the specified coro. A suspended coro works just like any other
445coro, except that the scheduler will not select a suspended coro for
446execution.
447
448Suspending a coro can be useful when you want to keep the coro from
449running, but you don't want to destroy it, or when you want to temporarily
450freeze a coro (e.g. for debugging) to resume it later.
451
452A scenario for the former would be to suspend all (other) coros after a
453fork and keep them alive, so their destructors aren't called, but new
454coros can be created.
455
456=item $coro->resume
457
458If the specified coro was suspended, it will be resumed. Note that when
459the coro was in the ready queue when it was suspended, it might have been
460unreadied by the scheduler, so an activation might have been lost.
461
462To avoid this, it is best to put a suspended coro into the ready queue
463unconditionally, as every synchronisation mechanism must protect itself
464against spurious wakeups, and the one in the Coro family certainly do
465that.
466
380=item $is_ready = $coroutine->is_ready 467=item $is_ready = $coro->is_ready
381 468
382Return wether the coroutine is currently the ready queue or not, 469Returns true iff the Coro object is in the ready queue. Unless the Coro
470object gets destroyed, it will eventually be scheduled by the scheduler.
383 471
472=item $is_running = $coro->is_running
473
474Returns true iff the Coro object is currently running. Only one Coro object
475can ever be in the running state (but it currently is possible to have
476multiple running Coro::States).
477
478=item $is_suspended = $coro->is_suspended
479
480Returns true iff this Coro object has been suspended. Suspended Coros will
481not ever be scheduled.
482
384=item $coroutine->cancel (arg...) 483=item $coro->cancel (arg...)
385 484
386Terminates the given coroutine and makes it return the given arguments as 485Terminates the given Coro and makes it return the given arguments as
387status (default: the empty list). Never returns if the coroutine is the 486status (default: the empty list). Never returns if the Coro is the
388current coroutine. 487current Coro.
389 488
390=cut 489=cut
391 490
392sub cancel { 491sub cancel {
393 my $self = shift; 492 my $self = shift;
394 $self->{_status} = [@_];
395 493
396 if ($current == $self) { 494 if ($current == $self) {
397 push @destroy, $self; 495 terminate @_;
398 $manager->ready;
399 &schedule while 1;
400 } else { 496 } else {
401 $self->_cancel; 497 $self->{_status} = [@_];
498 Coro::State::cancel $self;
402 } 499 }
403} 500}
404 501
502=item $coro->schedule_to
503
504Puts the current coro to sleep (like C<Coro::schedule>), but instead
505of continuing with the next coro from the ready queue, always switch to
506the given coro object (regardless of priority etc.). The readyness
507state of that coro isn't changed.
508
509This is an advanced method for special cases - I'd love to hear about any
510uses for this one.
511
512=item $coro->cede_to
513
514Like C<schedule_to>, but puts the current coro into the ready
515queue. This has the effect of temporarily switching to the given
516coro, and continuing some time later.
517
518This is an advanced method for special cases - I'd love to hear about any
519uses for this one.
520
521=item $coro->throw ([$scalar])
522
523If C<$throw> is specified and defined, it will be thrown as an exception
524inside the coro at the next convenient point in time. Otherwise
525clears the exception object.
526
527Coro will check for the exception each time a schedule-like-function
528returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
529>>, C<< Coro::Handle->readable >> and so on. Most of these functions
530detect this case and return early in case an exception is pending.
531
532The exception object will be thrown "as is" with the specified scalar in
533C<$@>, i.e. if it is a string, no line number or newline will be appended
534(unlike with C<die>).
535
536This can be used as a softer means than C<cancel> to ask a coro to
537end itself, although there is no guarantee that the exception will lead to
538termination, and if the exception isn't caught it might well end the whole
539program.
540
541You might also think of C<throw> as being the moral equivalent of
542C<kill>ing a coro with a signal (in this case, a scalar).
543
405=item $coroutine->join 544=item $coro->join
406 545
407Wait until the coroutine terminates and return any values given to the 546Wait until the coro terminates and return any values given to the
408C<terminate> or C<cancel> functions. C<join> can be called concurrently 547C<terminate> or C<cancel> functions. C<join> can be called concurrently
409from multiple coroutines. 548from multiple coro, and all will be resumed and given the status
549return once the C<$coro> terminates.
410 550
411=cut 551=cut
412 552
413sub join { 553sub join {
414 my $self = shift; 554 my $self = shift;
425 } 565 }
426 566
427 wantarray ? @{$self->{_status}} : $self->{_status}[0]; 567 wantarray ? @{$self->{_status}} : $self->{_status}[0];
428} 568}
429 569
430=item $coroutine->on_destroy (\&cb) 570=item $coro->on_destroy (\&cb)
431 571
432Registers a callback that is called when this coroutine gets destroyed, 572Registers a callback that is called when this coro gets destroyed,
433but before it is joined. The callback gets passed the terminate arguments, 573but before it is joined. The callback gets passed the terminate arguments,
434if any. 574if any, and I<must not> die, under any circumstances.
435 575
436=cut 576=cut
437 577
438sub on_destroy { 578sub on_destroy {
439 my ($self, $cb) = @_; 579 my ($self, $cb) = @_;
440 580
441 push @{ $self->{_on_destroy} }, $cb; 581 push @{ $self->{_on_destroy} }, $cb;
442} 582}
443 583
444=item $oldprio = $coroutine->prio ($newprio) 584=item $oldprio = $coro->prio ($newprio)
445 585
446Sets (or gets, if the argument is missing) the priority of the 586Sets (or gets, if the argument is missing) the priority of the
447coroutine. Higher priority coroutines get run before lower priority 587coro. Higher priority coro get run before lower priority
448coroutines. Priorities are small signed integers (currently -4 .. +3), 588coro. Priorities are small signed integers (currently -4 .. +3),
449that you can refer to using PRIO_xxx constants (use the import tag :prio 589that you can refer to using PRIO_xxx constants (use the import tag :prio
450to get then): 590to get then):
451 591
452 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 592 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
453 3 > 1 > 0 > -1 > -3 > -4 593 3 > 1 > 0 > -1 > -3 > -4
454 594
455 # set priority to HIGH 595 # set priority to HIGH
456 current->prio(PRIO_HIGH); 596 current->prio (PRIO_HIGH);
457 597
458The idle coroutine ($Coro::idle) always has a lower priority than any 598The idle coro ($Coro::idle) always has a lower priority than any
459existing coroutine. 599existing coro.
460 600
461Changing the priority of the current coroutine will take effect immediately, 601Changing the priority of the current coro will take effect immediately,
462but changing the priority of coroutines in the ready queue (but not 602but changing the priority of coro in the ready queue (but not
463running) will only take effect after the next schedule (of that 603running) will only take effect after the next schedule (of that
464coroutine). This is a bug that will be fixed in some future version. 604coro). This is a bug that will be fixed in some future version.
465 605
466=item $newprio = $coroutine->nice ($change) 606=item $newprio = $coro->nice ($change)
467 607
468Similar to C<prio>, but subtract the given value from the priority (i.e. 608Similar to C<prio>, but subtract the given value from the priority (i.e.
469higher values mean lower priority, just as in unix). 609higher values mean lower priority, just as in unix).
470 610
471=item $olddesc = $coroutine->desc ($newdesc) 611=item $olddesc = $coro->desc ($newdesc)
472 612
473Sets (or gets in case the argument is missing) the description for this 613Sets (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. 614coro. This is just a free-form string you can associate with a
615coro.
475 616
476This method simply sets the C<< $coroutine->{desc} >> member to the given string. You 617This method simply sets the C<< $coro->{desc} >> member to the given
477can modify this member directly if you wish. 618string. You can modify this member directly if you wish, and in fact, this
619is often preferred to indicate major processing states that cna then be
620seen for example in a L<Coro::Debug> session:
478 621
479=item $coroutine->throw ([$scalar]) 622 sub my_long_function {
480 623 local $Coro::current->{desc} = "now in my_long_function";
481If C<$throw> is specified and defined, it will be thrown as an exception 624 ...
482inside the coroutine at the next convinient point in time (usually after 625 $Coro::current->{desc} = "my_long_function: phase 1";
483it gains control at the next schedule/transfer/cede). Otherwise clears the 626 ...
484exception object. 627 $Coro::current->{desc} = "my_long_function: phase 2";
485 628 ...
486The exception object will be thrown "as is" with the specified scalar in 629 }
487C<$@>, 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.
494 630
495=cut 631=cut
496 632
497sub desc { 633sub desc {
498 my $old = $_[0]{desc}; 634 my $old = $_[0]{desc};
499 $_[0]{desc} = $_[1] if @_ > 1; 635 $_[0]{desc} = $_[1] if @_ > 1;
500 $old; 636 $old;
501} 637}
502 638
639sub transfer {
640 require Carp;
641 Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
642}
643
503=back 644=back
504 645
505=head2 GLOBAL FUNCTIONS 646=head1 GLOBAL FUNCTIONS
506 647
507=over 4 648=over 4
508 649
509=item Coro::nready 650=item Coro::nready
510 651
511Returns the number of coroutines that are currently in the ready state, 652Returns 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 653i.e. that can be switched to by calling C<schedule> directory or
654indirectly. 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, 655currently 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 656would cause a deadlock unless there is an idle handler that wakes up some
515that wakes up some coroutines. 657coro.
516 658
517=item my $guard = Coro::guard { ... } 659=item my $guard = Coro::guard { ... }
518 660
519This creates and returns a guard object. Nothing happens until the object 661This function still exists, but is deprecated. Please use the
520gets destroyed, in which case the codeblock given as argument will be 662C<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.
525 663
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 664=cut
537 665
538sub guard(&) { 666BEGIN { *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
550 667
551=item unblock_sub { ... } 668=item unblock_sub { ... }
552 669
553This utility function takes a BLOCK or code reference and "unblocks" it, 670This utility function takes a BLOCK or code reference and "unblocks" it,
554returning the new coderef. This means that the new coderef will return 671returning a new coderef. Unblocking means that calling the new coderef
555immediately without blocking, returning nothing, while the original code 672will return immediately without blocking, returning nothing, while the
556ref will be called (with parameters) from within its own coroutine. 673original code ref will be called (with parameters) from within another
674coro.
557 675
558The reason this function exists is that many event libraries (such as the 676The reason this function exists is that many event libraries (such as the
559venerable L<Event|Event> module) are not coroutine-safe (a weaker form 677venerable L<Event|Event> module) are not thread-safe (a weaker form
560of thread-safety). This means you must not block within event callbacks, 678of reentrancy). This means you must not block within event callbacks,
561otherwise you might suffer from crashes or worse. 679otherwise you might suffer from crashes or worse. The only event library
680currently known that is safe to use without C<unblock_sub> is L<EV>.
681
682Coro will try to catch you when you block in the event loop
683("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and
684only works when you do not run your own event loop.
562 685
563This function allows your callbacks to block by executing them in another 686This function allows your callbacks to block by executing them in another
564coroutine where it is safe to block. One example where blocking is handy 687coro 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 688is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
566disk. 689disk, for example.
567 690
568In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when 691In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
569creating event callbacks that want to block. 692creating event callbacks that want to block.
693
694If your handler does not plan to block (e.g. simply sends a message to
695another coro, or puts some other coro into the ready queue), there is
696no reason to use C<unblock_sub>.
697
698Note that you also need to use C<unblock_sub> for any other callbacks that
699are indirectly executed by any C-based event loop. For example, when you
700use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
701provides callbacks that are the result of some event callback, then you
702must not block either, or use C<unblock_sub>.
570 703
571=cut 704=cut
572 705
573our @unblock_queue; 706our @unblock_queue;
574 707
577# return immediately and can be reused) and because we cannot cede 710# return immediately and can be reused) and because we cannot cede
578# inside an event callback. 711# inside an event callback.
579our $unblock_scheduler = new Coro sub { 712our $unblock_scheduler = new Coro sub {
580 while () { 713 while () {
581 while (my $cb = pop @unblock_queue) { 714 while (my $cb = pop @unblock_queue) {
582 # this is an inlined copy of async_pool 715 &async_pool (@$cb);
583 my $coro = (pop @async_pool) || new Coro \&pool_handler;
584 716
585 $coro->{_invoke} = $cb;
586 $coro->ready;
587 cede; # for short-lived callbacks, this reduces pressure on the coro pool 717 # for short-lived callbacks, this reduces pressure on the coro pool
718 # as the chance is very high that the async_poll coro will be back
719 # in the idle state when cede returns
720 cede;
588 } 721 }
589 schedule; # sleep well 722 schedule; # sleep well
590 } 723 }
591}; 724};
592$unblock_scheduler->desc ("[unblock_sub scheduler]"); 725$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
593 726
594sub unblock_sub(&) { 727sub unblock_sub(&) {
595 my $cb = shift; 728 my $cb = shift;
596 729
597 sub { 730 sub {
598 unshift @unblock_queue, [$cb, @_]; 731 unshift @unblock_queue, [$cb, @_];
599 $unblock_scheduler->ready; 732 $unblock_scheduler->ready;
600 } 733 }
601} 734}
602 735
736=item $cb = rouse_cb
737
738Create and return a "rouse callback". That's a code reference that,
739when called, will remember a copy of its arguments and notify the owner
740coro of the callback.
741
742See the next function.
743
744=item @args = rouse_wait [$cb]
745
746Wait for the specified rouse callback (or the last one that was created in
747this coro).
748
749As soon as the callback is invoked (or when the callback was invoked
750before C<rouse_wait>), it will return the arguments originally passed to
751the rouse callback. In scalar context, that means you get the I<last>
752argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
753statement at the end.
754
755See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
756
603=back 757=back
604 758
605=cut 759=cut
606 760
6071; 7611;
608 762
763=head1 HOW TO WAIT FOR A CALLBACK
764
765It is very common for a coro to wait for some callback to be
766called. This occurs naturally when you use coro in an otherwise
767event-based program, or when you use event-based libraries.
768
769These typically register a callback for some event, and call that callback
770when the event occured. In a coro, however, you typically want to
771just wait for the event, simplyifying things.
772
773For example C<< AnyEvent->child >> registers a callback to be called when
774a specific child has exited:
775
776 my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
777
778But from within a coro, you often just want to write this:
779
780 my $status = wait_for_child $pid;
781
782Coro offers two functions specifically designed to make this easy,
783C<Coro::rouse_cb> and C<Coro::rouse_wait>.
784
785The first function, C<rouse_cb>, generates and returns a callback that,
786when invoked, will save its arguments and notify the coro that
787created the callback.
788
789The second function, C<rouse_wait>, waits for the callback to be called
790(by calling C<schedule> to go to sleep) and returns the arguments
791originally passed to the callback.
792
793Using these functions, it becomes easy to write the C<wait_for_child>
794function mentioned above:
795
796 sub wait_for_child($) {
797 my ($pid) = @_;
798
799 my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
800
801 my ($rpid, $rstatus) = Coro::rouse_wait;
802 $rstatus
803 }
804
805In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
806you can roll your own, using C<schedule>:
807
808 sub wait_for_child($) {
809 my ($pid) = @_;
810
811 # store the current coro in $current,
812 # and provide result variables for the closure passed to ->child
813 my $current = $Coro::current;
814 my ($done, $rstatus);
815
816 # pass a closure to ->child
817 my $watcher = AnyEvent->child (pid => $pid, cb => sub {
818 $rstatus = $_[1]; # remember rstatus
819 $done = 1; # mark $rstatus as valud
820 });
821
822 # wait until the closure has been called
823 schedule while !$done;
824
825 $rstatus
826 }
827
828
609=head1 BUGS/LIMITATIONS 829=head1 BUGS/LIMITATIONS
610 830
611 - you must make very sure that no coro is still active on global 831=over 4
612 destruction. very bad things might happen otherwise (usually segfaults).
613 832
833=item fork with pthread backend
834
835When Coro is compiled using the pthread backend (which isn't recommended
836but required on many BSDs as their libcs are completely broken), then
837coro will not survive a fork. There is no known workaround except to
838fix your libc and use a saner backend.
839
840=item perl process emulation ("threads")
841
614 - this module is not thread-safe. You should only ever use this module 842This 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 843module from the first thread (this requirement might be removed in the
616 to allow per-thread schedulers, but Coro::State does not yet allow 844future to allow per-thread schedulers, but Coro::State does not yet allow
617 this). 845this). I recommend disabling thread support and using processes, as having
846the windows process emulation enabled under unix roughly halves perl
847performance, even when not used.
848
849=item coro switching is not signal safe
850
851You must not switch to another coro from within a signal handler (only
852relevant with %SIG - most event libraries provide safe signals), I<unless>
853you are sure you are not interrupting a Coro function.
854
855That means you I<MUST NOT> call any function that might "block" the
856current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
857anything that calls those. Everything else, including calling C<ready>,
858works.
859
860=back
861
862
863=head1 WINDOWS PROCESS EMULATION
864
865A great many people seem to be confused about ithreads (for example, Chip
866Salzenberg called me unintelligent, incapable, stupid and gullible,
867while in the same mail making rather confused statements about perl
868ithreads (for example, that memory or files would be shared), showing his
869lack of understanding of this area - if it is hard to understand for Chip,
870it is probably not obvious to everybody).
871
872What follows is an ultra-condensed version of my talk about threads in
873scripting languages given onthe perl workshop 2009:
874
875The so-called "ithreads" were originally implemented for two reasons:
876first, to (badly) emulate unix processes on native win32 perls, and
877secondly, to replace the older, real thread model ("5.005-threads").
878
879It does that by using threads instead of OS processes. The difference
880between processes and threads is that threads share memory (and other
881state, such as files) between threads within a single process, while
882processes do not share anything (at least not semantically). That
883means that modifications done by one thread are seen by others, while
884modifications by one process are not seen by other processes.
885
886The "ithreads" work exactly like that: when creating a new ithreads
887process, all state is copied (memory is copied physically, files and code
888is copied logically). Afterwards, it isolates all modifications. On UNIX,
889the same behaviour can be achieved by using operating system processes,
890except that UNIX typically uses hardware built into the system to do this
891efficiently, while the windows process emulation emulates this hardware in
892software (rather efficiently, but of course it is still much slower than
893dedicated hardware).
894
895As mentioned before, loading code, modifying code, modifying data
896structures and so on is only visible in the ithreads process doing the
897modification, not in other ithread processes within the same OS process.
898
899This is why "ithreads" do not implement threads for perl at all, only
900processes. What makes it so bad is that on non-windows platforms, you can
901actually take advantage of custom hardware for this purpose (as evidenced
902by the forks module, which gives you the (i-) threads API, just much
903faster).
904
905Sharing data is in the i-threads model is done by transfering data
906structures between threads using copying semantics, which is very slow -
907shared data simply does not exist. Benchmarks using i-threads which are
908communication-intensive show extremely bad behaviour with i-threads (in
909fact, so bad that Coro, which cannot take direct advantage of multiple
910CPUs, is often orders of magnitude faster because it shares data using
911real threads, refer to my talk for details).
912
913As summary, i-threads *use* threads to implement processes, while
914the compatible forks module *uses* processes to emulate, uhm,
915processes. I-threads slow down every perl program when enabled, and
916outside of windows, serve no (or little) practical purpose, but
917disadvantages every single-threaded Perl program.
918
919This is the reason that I try to avoid the name "ithreads", as it is
920misleading as it implies that it implements some kind of thread model for
921perl, and prefer the name "windows process emulation", which describes the
922actual use and behaviour of it much better.
618 923
619=head1 SEE ALSO 924=head1 SEE ALSO
620 925
621Lower level Configuration, Coroutine Environment: L<Coro::State>. 926Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
622 927
623Debugging: L<Coro::Debug>. 928Debugging: L<Coro::Debug>.
624 929
625Support/Utility: L<Coro::Specific>, L<Coro::Util>. 930Support/Utility: L<Coro::Specific>, L<Coro::Util>.
626 931
627Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. 932Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
933L<Coro::SemaphoreSet>, L<Coro::RWLock>.
628 934
629Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>. 935I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
630 936
631Compatibility: L<Coro::LWP>, L<Coro::Storable>, L<Coro::Select>. 937Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
938a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
939L<Coro::Select>.
632 940
633Embedding: L<Coro:MakeMaker>. 941XS API: L<Coro::MakeMaker>.
942
943Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
634 944
635=head1 AUTHOR 945=head1 AUTHOR
636 946
637 Marc Lehmann <schmorp@schmorp.de> 947 Marc Lehmann <schmorp@schmorp.de>
638 http://home.schmorp.de/ 948 http://home.schmorp.de/

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