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1=head1 NAME 1=head1 NAME
2 2
3Coro - coroutine process abstraction 3Coro - the only real threads in perl
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use Coro; 7 use Coro;
8 8
11 print "2\n"; 11 print "2\n";
12 cede; # yield back to main 12 cede; # yield back to main
13 print "4\n"; 13 print "4\n";
14 }; 14 };
15 print "1\n"; 15 print "1\n";
16 cede; # yield to coroutine 16 cede; # yield to coro
17 print "3\n"; 17 print "3\n";
18 cede; # and again 18 cede; # and again
19 19
20 # use locking 20 # use locking
21 use Coro::Semaphore;
21 my $lock = new Coro::Semaphore; 22 my $lock = new Coro::Semaphore;
22 my $locked; 23 my $locked;
23 24
24 $lock->down; 25 $lock->down;
25 $locked = 1; 26 $locked = 1;
26 $lock->up; 27 $lock->up;
27 28
28=head1 DESCRIPTION 29=head1 DESCRIPTION
29 30
30This module collection manages coroutines. Coroutines are similar 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 = '4.51'; 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
94=head1 GLOBAL VARIABLES
95
70=over 4 96=over 4
71 97
72=item $main 98=item $Coro::main
73 99
74This coroutine represents the main program. 100This variable stores the Coro object that represents the main
101program. While you cna C<ready> it and do most other things you can do to
102coro, it is mainly useful to compare again C<$Coro::current>, to see
103whether you are running in the main program or not.
75 104
76=cut 105=cut
77 106
78$main = new Coro; 107# $main is now being initialised by Coro::State
79 108
80=item $current (or as function: current) 109=item $Coro::current
81 110
82The current coroutine (the last coroutine switched to). The initial value 111The Coro object representing the current coro (the last
112coro that the Coro scheduler switched to). The initial value is
83is C<$main> (of course). 113C<$Coro::main> (of course).
84 114
85This variable is B<strictly> I<read-only>. It is provided for performance 115This variable is B<strictly> I<read-only>. You can take copies of the
86reasons. If performance is not essential you are encouraged to use the 116value stored in it and use it as any other Coro object, but you must
87C<Coro::current> function instead. 117not otherwise modify the variable itself.
88 118
89=cut 119=cut
90 120
91$main->{desc} = "[main::]";
92
93# maybe some other module used Coro::Specific before...
94$main->{_specific} = $current->{_specific}
95 if $current;
96
97_set_current $main;
98
99sub current() { $current } 121sub current() { $current } # [DEPRECATED]
100 122
101=item $idle 123=item $Coro::idle
102 124
103A callback that is called whenever the scheduler finds no ready coroutines 125This variable is mainly useful to integrate Coro into event loops. It is
126usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
127pretty low-level functionality.
128
129This variable stores a Coro object that is put into the ready queue when
130there are no other ready threads (without invoking any ready hooks).
131
104to run. The default implementation prints "FATAL: deadlock detected" and 132The default implementation dies with "FATAL: deadlock detected.", followed
105exits, because the program has no other way to continue. 133by a thread listing, because the program has no other way to continue.
106 134
107This hook is overwritten by modules such as C<Coro::Timer> and 135This hook is overwritten by modules such as C<Coro::EV> and
108C<Coro::Event> to wait on an external event that hopefully wake up a 136C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
109coroutine so the scheduler can run it. 137coro so the scheduler can run it.
110 138
111Please note that if your callback recursively invokes perl (e.g. for event 139See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
112handlers), then it must be prepared to be called recursively itself.
113 140
114=cut 141=cut
115 142
116$idle = sub { 143# ||= because other modules could have provided their own by now
117 require Carp; 144$idle ||= new Coro sub {
118 Carp::croak ("FATAL: deadlock detected"); 145 require Coro::Debug;
146 die "FATAL: deadlock detected.\n"
147 . Coro::Debug::ps_listing ();
119}; 148};
120 149
121sub _cancel {
122 my ($self) = @_;
123
124 # free coroutine data and mark as destructed
125 $self->_destroy
126 or return;
127
128 # call all destruction callbacks
129 $_->(@{$self->{_status}})
130 for @{(delete $self->{_on_destroy}) || []};
131}
132
133# this coroutine is necessary because a coroutine 150# this coro is necessary because a coro
134# cannot destroy itself. 151# cannot destroy itself.
135my @destroy; 152our @destroy;
136my $manager; 153our $manager;
137 154
138$manager = new Coro sub { 155$manager = new Coro sub {
139 while () { 156 while () {
140 (shift @destroy)->_cancel 157 Coro::State::cancel shift @destroy
141 while @destroy; 158 while @destroy;
142 159
143 &schedule; 160 &schedule;
144 } 161 }
145}; 162};
146$manager->desc ("[coro manager]"); 163$manager->{desc} = "[coro manager]";
147$manager->prio (PRIO_MAX); 164$manager->prio (PRIO_MAX);
148 165
149=back 166=back
150 167
151=head2 STATIC METHODS 168=head1 SIMPLE CORO CREATION
152
153Static methods are actually functions that operate on the current coroutine only.
154 169
155=over 4 170=over 4
156 171
157=item async { ... } [@args...] 172=item async { ... } [@args...]
158 173
159Create a new asynchronous coroutine and return it's coroutine object 174Create a new coro and return its Coro object (usually
160(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
161terminated. 180terminated.
162 181
182The remaining arguments are passed as arguments to the closure.
183
163See the C<Coro::State::new> constructor for info about the coroutine 184See the C<Coro::State::new> constructor for info about the coro
164environment in which coroutines run. 185environment in which coro are executed.
165 186
166Calling 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
167the coroutine. Likewise, when the coroutine dies, the program will exit, 188the coro. Likewise, when the coro dies, the program will exit,
168just as it would in the main program. 189just as it would in the main program.
169 190
191If you do not want that, you can provide a default C<die> handler, or
192simply avoid dieing (by use of C<eval>).
193
170 # create a new coroutine that just prints its arguments 194Example: Create a new coro that just prints its arguments.
195
171 async { 196 async {
172 print "@_\n"; 197 print "@_\n";
173 } 1,2,3,4; 198 } 1,2,3,4;
174 199
175=cut
176
177sub async(&@) {
178 my $coro = new Coro @_;
179 $coro->ready;
180 $coro
181}
182
183=item async_pool { ... } [@args...] 200=item async_pool { ... } [@args...]
184 201
185Similar 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
186terminate 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
187that 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 :).
188 206
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
189Also, 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
190issued in case of an exception instead of terminating the program, as 212issued in case of an exception instead of terminating the program, as
191C<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>
192will 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,
193which somehow defeats the purpose of pooling. 215which somehow defeats the purpose of pooling (but is fine in the
216exceptional case).
194 217
195The 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
196disabled, the description will be reset and the default output filehandle 219disabled, the description will be reset and the default output filehandle
197gets restored, so you can change alkl these. Otherwise the coroutine will 220gets restored, so you can change all these. Otherwise the coro will
198be 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
199stuff 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
200done by using local as in C< local $/ >. 223simply done by using local as in: C<< local $/ >>.
201 224
202The 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
203changing $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
204required. 227coros as required.
205 228
206If you are concerned about pooled coroutines growing a lot because a 229If you are concerned about pooled coros growing a lot because a
207single 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
208{ 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
209addition 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
210(adjustable with $Coro::POOL_RSS) it will also exit. 233(adjustable via $Coro::POOL_RSS) it will also be destroyed.
211 234
212=cut 235=cut
213 236
214our $POOL_SIZE = 8; 237our $POOL_SIZE = 8;
215our $POOL_RSS = 16 * 1024; 238our $POOL_RSS = 32 * 1024;
216our @async_pool; 239our @async_pool;
217 240
218sub pool_handler { 241sub pool_handler {
219 my $cb;
220
221 while () { 242 while () {
222 eval { 243 eval {
223 while () { 244 &{&_pool_handler} while 1;
224 _pool_1 $cb;
225 &$cb;
226 _pool_2 $cb;
227 &schedule;
228 }
229 }; 245 };
230 246
231 last if $@ eq "\3async_pool terminate\2\n";
232 warn $@ if $@; 247 warn $@ if $@;
233 } 248 }
234} 249}
235 250
236sub async_pool(&@) { 251=back
237 # this is also inlined into the unlock_scheduler
238 my $coro = (pop @async_pool) || new Coro \&pool_handler;
239 252
240 $coro->{_invoke} = [@_]; 253=head1 STATIC METHODS
241 $coro->ready;
242 254
243 $coro 255Static methods are actually functions that implicitly operate on the
244} 256current coro.
257
258=over 4
245 259
246=item schedule 260=item schedule
247 261
248Calls the scheduler. Please note that the current coroutine will not be put 262Calls the scheduler. The scheduler will find the next coro that is
263to be run from the ready queue and switches to it. The next coro
264to be run is simply the one with the highest priority that is longest
265in its ready queue. If there is no coro ready, it will call the
266C<$Coro::idle> hook.
267
268Please note that the current coro will I<not> be put into the ready
249into the ready queue, so calling this function usually means you will 269queue, so calling this function usually means you will never be called
250never be called again unless something else (e.g. an event handler) calls 270again unless something else (e.g. an event handler) calls C<< ->ready >>,
251ready. 271thus waking you up.
252 272
253The 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.
254 280
255 { 281See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
256 # remember current coroutine
257 my $current = $Coro::current;
258 282
259 # register a hypothetical event handler 283=item cede
260 on_event_invoke sub { 284
261 # wake up sleeping coroutine 285"Cede" to other coros. This function puts the current coro into
262 $current->ready; 286the ready queue and calls C<schedule>, which has the effect of giving
263 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
264 }; 344 };
265 345
266 # call schedule until event occurred. 346 Coro::on_leave {
267 # in case we are woken up for other reasons 347 $ENV{TZ} = $old_tz;
268 # (current still defined), loop. 348 tzset; # restore old value
269 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.
270 } 353 };
271 354
272=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.
273 358
274"Cede" to other coroutines. This function puts the current coroutine into the 359Another interesting example implements time-sliced multitasking using
275ready queue and calls C<schedule>, which has the effect of giving up the 360interval timers (this could obviously be optimised, but does the job):
276current "timeslice" to other coroutines of the same or higher priority.
277 361
278=item Coro::cede_notself 362 # "timeslice" the given block
363 sub timeslice(&) {
364 use Time::HiRes ();
279 365
280Works like cede, but is not exported by default and will cede to any 366 Coro::on_enter {
281coroutine, 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 };
282 376
283=item terminate [arg...] 377 &{+shift};
378 }
284 379
285Terminates 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
286 388
287=item killall 389=item killall
288 390
289Kills/terminates/cancels all coroutines except the currently running 391Kills/terminates/cancels all coros except the currently running one.
290one. This is useful after a fork, either in the child or the parent, as
291usually only one of them should inherit the running coroutines.
292 392
293=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.
294 397
295sub terminate { 398=cut
296 $current->cancel (@_);
297}
298 399
299sub killall { 400sub killall {
300 for (Coro::State::list) { 401 for (Coro::State::list) {
301 $_->cancel 402 $_->cancel
302 if $_ != $current && UNIVERSAL::isa $_, "Coro"; 403 if $_ != $current && UNIVERSAL::isa $_, "Coro";
303 } 404 }
304} 405}
305 406
306=back 407=back
307 408
308=head2 COROUTINE METHODS 409=head1 CORO OBJECT METHODS
309 410
310These are the methods you can call on coroutine objects. 411These are the methods you can call on coro objects (or to create
412them).
311 413
312=over 4 414=over 4
313 415
314=item new Coro \&sub [, @args...] 416=item new Coro \&sub [, @args...]
315 417
316Create 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
317automatically terminates as if C<terminate> with the returned values were 419automatically terminates as if C<terminate> with the returned values were
318called. 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
319by calling the ready method. 421queue by calling the ready method.
320 422
321See 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
322coroutine environment. 424coro environment.
323 425
324=cut 426=cut
325 427
326sub _run_coro { 428sub _coro_run {
327 terminate &{+shift}; 429 terminate &{+shift};
328} 430}
329 431
330sub new {
331 my $class = shift;
332
333 $class->SUPER::new (\&_run_coro, @_)
334}
335
336=item $success = $coroutine->ready 432=item $success = $coro->ready
337 433
338Put 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
339and 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
340and return false. 436the ready queue, do nothing and return false.
341 437
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
342=item $is_ready = $coroutine->is_ready 467=item $is_ready = $coro->is_ready
343 468
344Return 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.
345 471
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
346=item $coroutine->cancel (arg...) 483=item $coro->cancel (arg...)
347 484
348Terminates the given coroutine and makes it return the given arguments as 485Terminates the given Coro and makes it return the given arguments as
349status (default: the empty list). Never returns if the coroutine is the 486status (default: the empty list). Never returns if the Coro is the
350current coroutine. 487current Coro.
351 488
352=cut 489=cut
353 490
354sub cancel { 491sub cancel {
355 my $self = shift; 492 my $self = shift;
356 $self->{_status} = [@_];
357 493
358 if ($current == $self) { 494 if ($current == $self) {
359 push @destroy, $self; 495 terminate @_;
360 $manager->ready;
361 &schedule while 1;
362 } else { 496 } else {
363 $self->_cancel; 497 $self->{_status} = [@_];
498 Coro::State::cancel $self;
364 } 499 }
365} 500}
366 501
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
367=item $coroutine->join 544=item $coro->join
368 545
369Wait until the coroutine terminates and return any values given to the 546Wait until the coro terminates and return any values given to the
370C<terminate> or C<cancel> functions. C<join> can be called concurrently 547C<terminate> or C<cancel> functions. C<join> can be called concurrently
371from multiple coroutines. 548from multiple coro, and all will be resumed and given the status
549return once the C<$coro> terminates.
372 550
373=cut 551=cut
374 552
375sub join { 553sub join {
376 my $self = shift; 554 my $self = shift;
387 } 565 }
388 566
389 wantarray ? @{$self->{_status}} : $self->{_status}[0]; 567 wantarray ? @{$self->{_status}} : $self->{_status}[0];
390} 568}
391 569
392=item $coroutine->on_destroy (\&cb) 570=item $coro->on_destroy (\&cb)
393 571
394Registers a callback that is called when this coroutine gets destroyed, 572Registers a callback that is called when this coro gets destroyed,
395but before it is joined. The callback gets passed the terminate arguments, 573but before it is joined. The callback gets passed the terminate arguments,
396if any. 574if any, and I<must not> die, under any circumstances.
397 575
398=cut 576=cut
399 577
400sub on_destroy { 578sub on_destroy {
401 my ($self, $cb) = @_; 579 my ($self, $cb) = @_;
402 580
403 push @{ $self->{_on_destroy} }, $cb; 581 push @{ $self->{_on_destroy} }, $cb;
404} 582}
405 583
406=item $oldprio = $coroutine->prio ($newprio) 584=item $oldprio = $coro->prio ($newprio)
407 585
408Sets (or gets, if the argument is missing) the priority of the 586Sets (or gets, if the argument is missing) the priority of the
409coroutine. Higher priority coroutines get run before lower priority 587coro. Higher priority coro get run before lower priority
410coroutines. Priorities are small signed integers (currently -4 .. +3), 588coro. Priorities are small signed integers (currently -4 .. +3),
411that 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
412to get then): 590to get then):
413 591
414 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
415 3 > 1 > 0 > -1 > -3 > -4 593 3 > 1 > 0 > -1 > -3 > -4
416 594
417 # set priority to HIGH 595 # set priority to HIGH
418 current->prio(PRIO_HIGH); 596 current->prio (PRIO_HIGH);
419 597
420The idle coroutine ($Coro::idle) always has a lower priority than any 598The idle coro ($Coro::idle) always has a lower priority than any
421existing coroutine. 599existing coro.
422 600
423Changing the priority of the current coroutine will take effect immediately, 601Changing the priority of the current coro will take effect immediately,
424but changing the priority of coroutines in the ready queue (but not 602but changing the priority of coro in the ready queue (but not
425running) will only take effect after the next schedule (of that 603running) will only take effect after the next schedule (of that
426coroutine). 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.
427 605
428=item $newprio = $coroutine->nice ($change) 606=item $newprio = $coro->nice ($change)
429 607
430Similar 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.
431higher values mean lower priority, just as in unix). 609higher values mean lower priority, just as in unix).
432 610
433=item $olddesc = $coroutine->desc ($newdesc) 611=item $olddesc = $coro->desc ($newdesc)
434 612
435Sets (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
436coroutine. 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.
437 616
438This 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
439can 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:
440 621
441=item $coroutine->throw ([$scalar]) 622 sub my_long_function {
442 623 local $Coro::current->{desc} = "now in my_long_function";
443If C<$throw> is specified and defined, it will be thrown as an exception 624 ...
444inside the coroutine at the next convinient point in time (usually after 625 $Coro::current->{desc} = "my_long_function: phase 1";
445it gains control at the next schedule/transfer/cede). Otherwise clears the 626 ...
446exception object. 627 $Coro::current->{desc} = "my_long_function: phase 2";
447 628 ...
448The exception object will be thrown "as is" with the specified scalar in 629 }
449C<$@>, i.e. if it is a string, no line number or newline will be appended
450(unlike with C<die>).
451
452This can be used as a softer means than C<cancel> to ask a coroutine to
453end itself, although there is no guarentee that the exception will lead to
454termination, and if the exception isn't caught it might well end the whole
455program.
456 630
457=cut 631=cut
458 632
459sub desc { 633sub desc {
460 my $old = $_[0]{desc}; 634 my $old = $_[0]{desc};
461 $_[0]{desc} = $_[1] if @_ > 1; 635 $_[0]{desc} = $_[1] if @_ > 1;
462 $old; 636 $old;
463} 637}
464 638
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
465=back 644=back
466 645
467=head2 GLOBAL FUNCTIONS 646=head1 GLOBAL FUNCTIONS
468 647
469=over 4 648=over 4
470 649
471=item Coro::nready 650=item Coro::nready
472 651
473Returns the number of coroutines that are currently in the ready state, 652Returns the number of coro that are currently in the ready state,
474i.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
475coroutine 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>
476and 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
477that wakes up some coroutines. 657coro.
478 658
479=item my $guard = Coro::guard { ... } 659=item my $guard = Coro::guard { ... }
480 660
481This creates and returns a guard object. Nothing happens until the object 661This function still exists, but is deprecated. Please use the
482gets destroyed, in which case the codeblock given as argument will be 662C<Guard::guard> function instead.
483executed. This is useful to free locks or other resources in case of a
484runtime error or when the coroutine gets canceled, as in both cases the
485guard block will be executed. The guard object supports only one method,
486C<< ->cancel >>, which will keep the codeblock from being executed.
487 663
488Example: set some flag and clear it again when the coroutine gets canceled
489or the function returns:
490
491 sub do_something {
492 my $guard = Coro::guard { $busy = 0 };
493 $busy = 1;
494
495 # do something that requires $busy to be true
496 }
497
498=cut 664=cut
499 665
500sub guard(&) { 666BEGIN { *guard = \&Guard::guard }
501 bless \(my $cb = $_[0]), "Coro::guard"
502}
503
504sub Coro::guard::cancel {
505 ${$_[0]} = sub { };
506}
507
508sub Coro::guard::DESTROY {
509 ${$_[0]}->();
510}
511
512 667
513=item unblock_sub { ... } 668=item unblock_sub { ... }
514 669
515This utility function takes a BLOCK or code reference and "unblocks" it, 670This utility function takes a BLOCK or code reference and "unblocks" it,
516returning the new coderef. This means that the new coderef will return 671returning a new coderef. Unblocking means that calling the new coderef
517immediately without blocking, returning nothing, while the original code 672will return immediately without blocking, returning nothing, while the
518ref will be called (with parameters) from within its own coroutine. 673original code ref will be called (with parameters) from within another
674coro.
519 675
520The reason this function exists is that many event libraries (such as the 676The reason this function exists is that many event libraries (such as
521venerable L<Event|Event> module) are not coroutine-safe (a weaker form 677the venerable L<Event|Event> module) are not thread-safe (a weaker form
522of thread-safety). This means you must not block within event callbacks, 678of reentrancy). This means you must not block within event callbacks,
523otherwise 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> (but
681you might still run into deadlocks if all event loops are blocked).
682
683Coro will try to catch you when you block in the event loop
684("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and
685only works when you do not run your own event loop.
524 686
525This function allows your callbacks to block by executing them in another 687This function allows your callbacks to block by executing them in another
526coroutine where it is safe to block. One example where blocking is handy 688coro where it is safe to block. One example where blocking is handy
527is when you use the L<Coro::AIO|Coro::AIO> functions to save results to 689is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
528disk. 690disk, for example.
529 691
530In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when 692In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
531creating event callbacks that want to block. 693creating event callbacks that want to block.
694
695If your handler does not plan to block (e.g. simply sends a message to
696another coro, or puts some other coro into the ready queue), there is
697no reason to use C<unblock_sub>.
698
699Note that you also need to use C<unblock_sub> for any other callbacks that
700are indirectly executed by any C-based event loop. For example, when you
701use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
702provides callbacks that are the result of some event callback, then you
703must not block either, or use C<unblock_sub>.
532 704
533=cut 705=cut
534 706
535our @unblock_queue; 707our @unblock_queue;
536 708
539# return immediately and can be reused) and because we cannot cede 711# return immediately and can be reused) and because we cannot cede
540# inside an event callback. 712# inside an event callback.
541our $unblock_scheduler = new Coro sub { 713our $unblock_scheduler = new Coro sub {
542 while () { 714 while () {
543 while (my $cb = pop @unblock_queue) { 715 while (my $cb = pop @unblock_queue) {
544 # this is an inlined copy of async_pool 716 &async_pool (@$cb);
545 my $coro = (pop @async_pool) || new Coro \&pool_handler;
546 717
547 $coro->{_invoke} = $cb;
548 $coro->ready;
549 cede; # for short-lived callbacks, this reduces pressure on the coro pool 718 # for short-lived callbacks, this reduces pressure on the coro pool
719 # as the chance is very high that the async_poll coro will be back
720 # in the idle state when cede returns
721 cede;
550 } 722 }
551 schedule; # sleep well 723 schedule; # sleep well
552 } 724 }
553}; 725};
554$unblock_scheduler->desc ("[unblock_sub scheduler]"); 726$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
555 727
556sub unblock_sub(&) { 728sub unblock_sub(&) {
557 my $cb = shift; 729 my $cb = shift;
558 730
559 sub { 731 sub {
560 unshift @unblock_queue, [$cb, @_]; 732 unshift @unblock_queue, [$cb, @_];
561 $unblock_scheduler->ready; 733 $unblock_scheduler->ready;
562 } 734 }
563} 735}
564 736
737=item $cb = rouse_cb
738
739Create and return a "rouse callback". That's a code reference that,
740when called, will remember a copy of its arguments and notify the owner
741coro of the callback.
742
743See the next function.
744
745=item @args = rouse_wait [$cb]
746
747Wait for the specified rouse callback (or the last one that was created in
748this coro).
749
750As soon as the callback is invoked (or when the callback was invoked
751before C<rouse_wait>), it will return the arguments originally passed to
752the rouse callback. In scalar context, that means you get the I<last>
753argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
754statement at the end.
755
756See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
757
565=back 758=back
566 759
567=cut 760=cut
568 761
5691; 7621;
570 763
764=head1 HOW TO WAIT FOR A CALLBACK
765
766It is very common for a coro to wait for some callback to be
767called. This occurs naturally when you use coro in an otherwise
768event-based program, or when you use event-based libraries.
769
770These typically register a callback for some event, and call that callback
771when the event occured. In a coro, however, you typically want to
772just wait for the event, simplyifying things.
773
774For example C<< AnyEvent->child >> registers a callback to be called when
775a specific child has exited:
776
777 my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
778
779But from within a coro, you often just want to write this:
780
781 my $status = wait_for_child $pid;
782
783Coro offers two functions specifically designed to make this easy,
784C<Coro::rouse_cb> and C<Coro::rouse_wait>.
785
786The first function, C<rouse_cb>, generates and returns a callback that,
787when invoked, will save its arguments and notify the coro that
788created the callback.
789
790The second function, C<rouse_wait>, waits for the callback to be called
791(by calling C<schedule> to go to sleep) and returns the arguments
792originally passed to the callback.
793
794Using these functions, it becomes easy to write the C<wait_for_child>
795function mentioned above:
796
797 sub wait_for_child($) {
798 my ($pid) = @_;
799
800 my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
801
802 my ($rpid, $rstatus) = Coro::rouse_wait;
803 $rstatus
804 }
805
806In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
807you can roll your own, using C<schedule>:
808
809 sub wait_for_child($) {
810 my ($pid) = @_;
811
812 # store the current coro in $current,
813 # and provide result variables for the closure passed to ->child
814 my $current = $Coro::current;
815 my ($done, $rstatus);
816
817 # pass a closure to ->child
818 my $watcher = AnyEvent->child (pid => $pid, cb => sub {
819 $rstatus = $_[1]; # remember rstatus
820 $done = 1; # mark $rstatus as valud
821 });
822
823 # wait until the closure has been called
824 schedule while !$done;
825
826 $rstatus
827 }
828
829
571=head1 BUGS/LIMITATIONS 830=head1 BUGS/LIMITATIONS
572 831
573 - you must make very sure that no coro is still active on global 832=over 4
574 destruction. very bad things might happen otherwise (usually segfaults).
575 833
834=item fork with pthread backend
835
836When Coro is compiled using the pthread backend (which isn't recommended
837but required on many BSDs as their libcs are completely broken), then
838coro will not survive a fork. There is no known workaround except to
839fix your libc and use a saner backend.
840
841=item perl process emulation ("threads")
842
576 - this module is not thread-safe. You should only ever use this module 843This module is not perl-pseudo-thread-safe. You should only ever use this
577 from the same thread (this requirement might be loosened in the future 844module from the first thread (this requirement might be removed in the
578 to allow per-thread schedulers, but Coro::State does not yet allow 845future to allow per-thread schedulers, but Coro::State does not yet allow
579 this). 846this). I recommend disabling thread support and using processes, as having
847the windows process emulation enabled under unix roughly halves perl
848performance, even when not used.
849
850=item coro switching is not signal safe
851
852You must not switch to another coro from within a signal handler (only
853relevant with %SIG - most event libraries provide safe signals), I<unless>
854you are sure you are not interrupting a Coro function.
855
856That means you I<MUST NOT> call any function that might "block" the
857current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
858anything that calls those. Everything else, including calling C<ready>,
859works.
860
861=back
862
863
864=head1 WINDOWS PROCESS EMULATION
865
866A great many people seem to be confused about ithreads (for example, Chip
867Salzenberg called me unintelligent, incapable, stupid and gullible,
868while in the same mail making rather confused statements about perl
869ithreads (for example, that memory or files would be shared), showing his
870lack of understanding of this area - if it is hard to understand for Chip,
871it is probably not obvious to everybody).
872
873What follows is an ultra-condensed version of my talk about threads in
874scripting languages given on the perl workshop 2009:
875
876The so-called "ithreads" were originally implemented for two reasons:
877first, to (badly) emulate unix processes on native win32 perls, and
878secondly, to replace the older, real thread model ("5.005-threads").
879
880It does that by using threads instead of OS processes. The difference
881between processes and threads is that threads share memory (and other
882state, such as files) between threads within a single process, while
883processes do not share anything (at least not semantically). That
884means that modifications done by one thread are seen by others, while
885modifications by one process are not seen by other processes.
886
887The "ithreads" work exactly like that: when creating a new ithreads
888process, all state is copied (memory is copied physically, files and code
889is copied logically). Afterwards, it isolates all modifications. On UNIX,
890the same behaviour can be achieved by using operating system processes,
891except that UNIX typically uses hardware built into the system to do this
892efficiently, while the windows process emulation emulates this hardware in
893software (rather efficiently, but of course it is still much slower than
894dedicated hardware).
895
896As mentioned before, loading code, modifying code, modifying data
897structures and so on is only visible in the ithreads process doing the
898modification, not in other ithread processes within the same OS process.
899
900This is why "ithreads" do not implement threads for perl at all, only
901processes. What makes it so bad is that on non-windows platforms, you can
902actually take advantage of custom hardware for this purpose (as evidenced
903by the forks module, which gives you the (i-) threads API, just much
904faster).
905
906Sharing data is in the i-threads model is done by transfering data
907structures between threads using copying semantics, which is very slow -
908shared data simply does not exist. Benchmarks using i-threads which are
909communication-intensive show extremely bad behaviour with i-threads (in
910fact, so bad that Coro, which cannot take direct advantage of multiple
911CPUs, is often orders of magnitude faster because it shares data using
912real threads, refer to my talk for details).
913
914As summary, i-threads *use* threads to implement processes, while
915the compatible forks module *uses* processes to emulate, uhm,
916processes. I-threads slow down every perl program when enabled, and
917outside of windows, serve no (or little) practical purpose, but
918disadvantages every single-threaded Perl program.
919
920This is the reason that I try to avoid the name "ithreads", as it is
921misleading as it implies that it implements some kind of thread model for
922perl, and prefer the name "windows process emulation", which describes the
923actual use and behaviour of it much better.
580 924
581=head1 SEE ALSO 925=head1 SEE ALSO
582 926
583Lower level Configuration, Coroutine Environment: L<Coro::State>. 927Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
584 928
585Debugging: L<Coro::Debug>. 929Debugging: L<Coro::Debug>.
586 930
587Support/Utility: L<Coro::Specific>, L<Coro::Util>. 931Support/Utility: L<Coro::Specific>, L<Coro::Util>.
588 932
589Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. 933Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
934L<Coro::SemaphoreSet>, L<Coro::RWLock>.
590 935
591Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>. 936I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
592 937
593Compatibility: L<Coro::LWP>, L<Coro::Storable>, L<Coro::Select>. 938Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
939a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
940L<Coro::Select>.
594 941
595Embedding: L<Coro::MakeMaker>. 942XS API: L<Coro::MakeMaker>.
943
944Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
596 945
597=head1 AUTHOR 946=head1 AUTHOR
598 947
599 Marc Lehmann <schmorp@schmorp.de> 948 Marc Lehmann <schmorp@schmorp.de>
600 http://home.schmorp.de/ 949 http://home.schmorp.de/

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