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1=head1 NAME 1=head1 NAME
2 2
3Coro - real threads in perl 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 use Coro::Semaphore;
29=head1 DESCRIPTION 29=head1 DESCRIPTION
30 30
31For a tutorial-style introduction, please read the L<Coro::Intro> 31For a tutorial-style introduction, please read the L<Coro::Intro>
32manpage. This manpage mainly contains reference information. 32manpage. This manpage mainly contains reference information.
33 33
34This module collection manages coroutines, that is, cooperative 34This module collection manages continuations in general, most often in
35threads. Coroutines are similar to kernel threads but don't (in general) 35the form of cooperative threads (also called coros, or simply "coro"
36in the documentation). They are similar to kernel threads but don't (in
36run in parallel at the same time even on SMP machines. The specific flavor 37general) run in parallel at the same time even on SMP machines. The
37of coroutine used in this module also guarantees you that it will not 38specific flavor of thread offered by this module also guarantees you that
38switch between coroutines unless necessary, at easily-identified points 39it will not switch between threads unless necessary, at easily-identified
39in your program, so locking and parallel access are rarely an issue, 40points in your program, so locking and parallel access are rarely an
40making coroutine programming much safer and easier than using other thread 41issue, making thread programming much safer and easier than using other
41models. 42thread models.
42 43
43Unlike the so-called "Perl threads" (which are not actually real threads 44Unlike the so-called "Perl threads" (which are not actually real threads
44but only the windows process emulation ported to unix), Coro provides a 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
45full shared address space, which makes communication between coroutines 47a full shared address space, which makes communication between threads
46very easy. And coroutines are fast, too: disabling the Windows process 48very easy. And Coro's threads are fast, too: disabling the Windows
47emulation code in your perl and using Coro can easily result in a two to 49process emulation code in your perl and using Coro can easily result in
48four times speed increase for your programs. 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.
49 53
50Coro achieves that by supporting multiple running interpreters that share 54Coro achieves that by supporting multiple running interpreters that share
51data, which is especially useful to code pseudo-parallel processes and 55data, which is especially useful to code pseudo-parallel processes and
52for event-based programming, such as multiple HTTP-GET requests running 56for event-based programming, such as multiple HTTP-GET requests running
53concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro 57concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
54into an event-based environment. 58into an event-based environment.
55 59
56In this module, a coroutines is defined as "callchain + lexical variables 60In this module, a thread is defined as "callchain + lexical variables +
57+ @_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own 61some package variables + C stack), that is, a thread has its own callchain,
58callchain, its own set of lexicals and its own set of perls most important 62its own set of lexicals and its own set of perls most important global
59global variables (see L<Coro::State> for more configuration and background 63variables (see L<Coro::State> for more configuration and background info).
60info).
61 64
62See also the C<SEE ALSO> section at the end of this document - the Coro 65See also the C<SEE ALSO> section at the end of this document - the Coro
63module family is quite large. 66module family is quite large.
64 67
65=cut 68=cut
66 69
67package Coro; 70package Coro;
68 71
69use strict qw(vars subs); 72use common::sense;
70no warnings "uninitialized"; 73
74use Carp ();
75
76use Guard ();
71 77
72use Coro::State; 78use Coro::State;
73 79
74use base qw(Coro::State Exporter); 80use base qw(Coro::State Exporter);
75 81
76our $idle; # idle handler 82our $idle; # idle handler
77our $main; # main coroutine 83our $main; # main coro
78our $current; # current coroutine 84our $current; # current coro
79 85
80our $VERSION = "5.0"; 86our $VERSION = 5.2;
81 87
82our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); 88our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
83our %EXPORT_TAGS = ( 89our %EXPORT_TAGS = (
84 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 90 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
85); 91);
86our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); 92our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
87 93
89 95
90=over 4 96=over 4
91 97
92=item $Coro::main 98=item $Coro::main
93 99
94This variable stores the coroutine object that represents the main 100This variable stores the Coro object that represents the main
95program. While you cna C<ready> it and do most other things you can do to 101program. While you cna C<ready> it and do most other things you can do to
96coroutines, it is mainly useful to compare again C<$Coro::current>, to see 102coro, it is mainly useful to compare again C<$Coro::current>, to see
97whether you are running in the main program or not. 103whether you are running in the main program or not.
98 104
99=cut 105=cut
100 106
101# $main is now being initialised by Coro::State 107# $main is now being initialised by Coro::State
102 108
103=item $Coro::current 109=item $Coro::current
104 110
105The coroutine object representing the current coroutine (the last 111The Coro object representing the current coro (the last
106coroutine that the Coro scheduler switched to). The initial value is 112coro that the Coro scheduler switched to). The initial value is
107C<$Coro::main> (of course). 113C<$Coro::main> (of course).
108 114
109This variable is B<strictly> I<read-only>. You can take copies of the 115This variable is B<strictly> I<read-only>. You can take copies of the
110value stored in it and use it as any other coroutine object, but you must 116value stored in it and use it as any other Coro object, but you must
111not otherwise modify the variable itself. 117not otherwise modify the variable itself.
112 118
113=cut 119=cut
114 120
115sub current() { $current } # [DEPRECATED] 121sub current() { $current } # [DEPRECATED]
116 122
117=item $Coro::idle 123=item $Coro::idle
118 124
119This variable is mainly useful to integrate Coro into event loops. It is 125This variable is mainly useful to integrate Coro into event loops. It is
120usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is 126usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
121pretty low-level functionality. 127pretty low-level functionality.
122 128
123This variable stores a callback that is called whenever the scheduler 129This variable stores a Coro object that is put into the ready queue when
124finds no ready coroutines to run. The default implementation prints 130there are no other ready threads (without invoking any ready hooks).
125"FATAL: deadlock detected" and exits, because the program has no other way
126to continue.
127 131
132The default implementation dies with "FATAL: deadlock detected.", followed
133by a thread listing, because the program has no other way to continue.
134
128This hook is overwritten by modules such as C<Coro::Timer> and 135This hook is overwritten by modules such as C<Coro::EV> and
129C<Coro::AnyEvent> to wait on an external event that hopefully wake up a 136C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
130coroutine so the scheduler can run it. 137coro so the scheduler can run it.
131 138
132Note that the callback I<must not>, under any circumstances, block
133the current coroutine. Normally, this is achieved by having an "idle
134coroutine" that calls the event loop and then blocks again, and then
135readying that coroutine in the idle handler.
136
137See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this 139See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
138technique.
139 140
140Please note that if your callback recursively invokes perl (e.g. for event
141handlers), then it must be prepared to be called recursively itself.
142
143=cut 141=cut
144 142
145$idle = sub { 143$idle = new Coro sub {
146 require Carp; 144 require Coro::Debug;
147 Carp::croak ("FATAL: deadlock detected"); 145 die "FATAL: deadlock detected.\n"
146 . Coro::Debug::ps_listing ();
148}; 147};
149 148
150# this coroutine is necessary because a coroutine 149# this coro is necessary because a coro
151# cannot destroy itself. 150# cannot destroy itself.
152our @destroy; 151our @destroy;
153our $manager; 152our $manager;
154 153
155$manager = new Coro sub { 154$manager = new Coro sub {
156 while () { 155 while () {
157 Coro::_cancel shift @destroy 156 Coro::State::cancel shift @destroy
158 while @destroy; 157 while @destroy;
159 158
160 &schedule; 159 &schedule;
161 } 160 }
162}; 161};
163$manager->{desc} = "[coro manager]"; 162$manager->{desc} = "[coro manager]";
164$manager->prio (PRIO_MAX); 163$manager->prio (PRIO_MAX);
165 164
166=back 165=back
167 166
168=head1 SIMPLE COROUTINE CREATION 167=head1 SIMPLE CORO CREATION
169 168
170=over 4 169=over 4
171 170
172=item async { ... } [@args...] 171=item async { ... } [@args...]
173 172
174Create a new coroutine and return it's coroutine object (usually 173Create a new coro and return its Coro object (usually
175unused). The coroutine will be put into the ready queue, so 174unused). The coro will be put into the ready queue, so
176it will start running automatically on the next scheduler run. 175it will start running automatically on the next scheduler run.
177 176
178The first argument is a codeblock/closure that should be executed in the 177The first argument is a codeblock/closure that should be executed in the
179coroutine. When it returns argument returns the coroutine is automatically 178coro. When it returns argument returns the coro is automatically
180terminated. 179terminated.
181 180
182The remaining arguments are passed as arguments to the closure. 181The remaining arguments are passed as arguments to the closure.
183 182
184See the C<Coro::State::new> constructor for info about the coroutine 183See the C<Coro::State::new> constructor for info about the coro
185environment in which coroutines are executed. 184environment in which coro are executed.
186 185
187Calling C<exit> in a coroutine will do the same as calling exit outside 186Calling C<exit> in a coro will do the same as calling exit outside
188the coroutine. Likewise, when the coroutine dies, the program will exit, 187the coro. Likewise, when the coro dies, the program will exit,
189just as it would in the main program. 188just as it would in the main program.
190 189
191If you do not want that, you can provide a default C<die> handler, or 190If you do not want that, you can provide a default C<die> handler, or
192simply avoid dieing (by use of C<eval>). 191simply avoid dieing (by use of C<eval>).
193 192
194Example: Create a new coroutine that just prints its arguments. 193Example: Create a new coro that just prints its arguments.
195 194
196 async { 195 async {
197 print "@_\n"; 196 print "@_\n";
198 } 1,2,3,4; 197 } 1,2,3,4;
199 198
200=cut
201
202sub async(&@) {
203 my $coro = new Coro @_;
204 $coro->ready;
205 $coro
206}
207
208=item async_pool { ... } [@args...] 199=item async_pool { ... } [@args...]
209 200
210Similar to C<async>, but uses a coroutine pool, so you should not call 201Similar to C<async>, but uses a coro pool, so you should not call
211terminate or join on it (although you are allowed to), and you get a 202terminate or join on it (although you are allowed to), and you get a
212coroutine that might have executed other code already (which can be good 203coro that might have executed other code already (which can be good
213or bad :). 204or bad :).
214 205
215On the plus side, this function is about twice as fast as creating (and 206On the plus side, this function is about twice as fast as creating (and
216destroying) a completely new coroutine, so if you need a lot of generic 207destroying) a completely new coro, so if you need a lot of generic
217coroutines in quick successsion, use C<async_pool>, not C<async>. 208coros in quick successsion, use C<async_pool>, not C<async>.
218 209
219The code block is executed in an C<eval> context and a warning will be 210The code block is executed in an C<eval> context and a warning will be
220issued in case of an exception instead of terminating the program, as 211issued in case of an exception instead of terminating the program, as
221C<async> does. As the coroutine is being reused, stuff like C<on_destroy> 212C<async> does. As the coro is being reused, stuff like C<on_destroy>
222will not work in the expected way, unless you call terminate or cancel, 213will not work in the expected way, unless you call terminate or cancel,
223which somehow defeats the purpose of pooling (but is fine in the 214which somehow defeats the purpose of pooling (but is fine in the
224exceptional case). 215exceptional case).
225 216
226The priority will be reset to C<0> after each run, tracing will be 217The priority will be reset to C<0> after each run, tracing will be
227disabled, the description will be reset and the default output filehandle 218disabled, the description will be reset and the default output filehandle
228gets restored, so you can change all these. Otherwise the coroutine will 219gets restored, so you can change all these. Otherwise the coro will
229be re-used "as-is": most notably if you change other per-coroutine global 220be re-used "as-is": most notably if you change other per-coro global
230stuff such as C<$/> you I<must needs> revert that change, which is most 221stuff such as C<$/> you I<must needs> revert that change, which is most
231simply done by using local as in: C<< local $/ >>. 222simply done by using local as in: C<< local $/ >>.
232 223
233The idle pool size is limited to C<8> idle coroutines (this can be 224The idle pool size is limited to C<8> idle coros (this can be
234adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle 225adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
235coros as required. 226coros as required.
236 227
237If you are concerned about pooled coroutines growing a lot because a 228If you are concerned about pooled coros growing a lot because a
238single C<async_pool> used a lot of stackspace you can e.g. C<async_pool 229single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
239{ terminate }> once per second or so to slowly replenish the pool. In 230{ terminate }> once per second or so to slowly replenish the pool. In
240addition to that, when the stacks used by a handler grows larger than 32kb 231addition to that, when the stacks used by a handler grows larger than 32kb
241(adjustable via $Coro::POOL_RSS) it will also be destroyed. 232(adjustable via $Coro::POOL_RSS) it will also be destroyed.
242 233
259=back 250=back
260 251
261=head1 STATIC METHODS 252=head1 STATIC METHODS
262 253
263Static methods are actually functions that implicitly operate on the 254Static methods are actually functions that implicitly operate on the
264current coroutine. 255current coro.
265 256
266=over 4 257=over 4
267 258
268=item schedule 259=item schedule
269 260
270Calls the scheduler. The scheduler will find the next coroutine that is 261Calls the scheduler. The scheduler will find the next coro that is
271to be run from the ready queue and switches to it. The next coroutine 262to be run from the ready queue and switches to it. The next coro
272to be run is simply the one with the highest priority that is longest 263to be run is simply the one with the highest priority that is longest
273in its ready queue. If there is no coroutine ready, it will clal the 264in its ready queue. If there is no coro ready, it will call the
274C<$Coro::idle> hook. 265C<$Coro::idle> hook.
275 266
276Please note that the current coroutine will I<not> be put into the ready 267Please note that the current coro will I<not> be put into the ready
277queue, so calling this function usually means you will never be called 268queue, so calling this function usually means you will never be called
278again unless something else (e.g. an event handler) calls C<< ->ready >>, 269again unless something else (e.g. an event handler) calls C<< ->ready >>,
279thus waking you up. 270thus waking you up.
280 271
281This makes C<schedule> I<the> generic method to use to block the current 272This makes C<schedule> I<the> generic method to use to block the current
282coroutine and wait for events: first you remember the current coroutine in 273coro and wait for events: first you remember the current coro in
283a variable, then arrange for some callback of yours to call C<< ->ready 274a variable, then arrange for some callback of yours to call C<< ->ready
284>> on that once some event happens, and last you call C<schedule> to put 275>> on that once some event happens, and last you call C<schedule> to put
285yourself to sleep. Note that a lot of things can wake your coroutine up, 276yourself to sleep. Note that a lot of things can wake your coro up,
286so you need to check whether the event indeed happened, e.g. by storing the 277so you need to check whether the event indeed happened, e.g. by storing the
287status in a variable. 278status in a variable.
288 279
289See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks. 280See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
290 281
291=item cede 282=item cede
292 283
293"Cede" to other coroutines. This function puts the current coroutine into 284"Cede" to other coros. This function puts the current coro into
294the ready queue and calls C<schedule>, which has the effect of giving 285the ready queue and calls C<schedule>, which has the effect of giving
295up the current "timeslice" to other coroutines of the same or higher 286up the current "timeslice" to other coros of the same or higher
296priority. Once your coroutine gets its turn again it will automatically be 287priority. Once your coro gets its turn again it will automatically be
297resumed. 288resumed.
298 289
299This function is often called C<yield> in other languages. 290This function is often called C<yield> in other languages.
300 291
301=item Coro::cede_notself 292=item Coro::cede_notself
302 293
303Works like cede, but is not exported by default and will cede to I<any> 294Works like cede, but is not exported by default and will cede to I<any>
304coroutine, regardless of priority. This is useful sometimes to ensure 295coro, regardless of priority. This is useful sometimes to ensure
305progress is made. 296progress is made.
306 297
307=item terminate [arg...] 298=item terminate [arg...]
308 299
309Terminates the current coroutine with the given status values (see L<cancel>). 300Terminates the current coro with the given status values (see L<cancel>).
301
302=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
303
304These function install enter and leave winders in the current scope. The
305enter block will be executed when on_enter is called and whenever the
306current coro is re-entered by the scheduler, while the leave block is
307executed whenever the current coro is blocked by the scheduler, and
308also when the containing scope is exited (by whatever means, be it exit,
309die, last etc.).
310
311I<Neither invoking the scheduler, nor exceptions, are allowed within those
312BLOCKs>. That means: do not even think about calling C<die> without an
313eval, and do not even think of entering the scheduler in any way.
314
315Since both BLOCKs are tied to the current scope, they will automatically
316be removed when the current scope exits.
317
318These functions implement the same concept as C<dynamic-wind> in scheme
319does, and are useful when you want to localise some resource to a specific
320coro.
321
322They slow down thread switching considerably for coros that use them
323(about 40% for a BLOCK with a single assignment, so thread switching is
324still reasonably fast if the handlers are fast).
325
326These functions are best understood by an example: The following function
327will change the current timezone to "Antarctica/South_Pole", which
328requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
329which remember/change the current timezone and restore the previous
330value, respectively, the timezone is only changed for the coro that
331installed those handlers.
332
333 use POSIX qw(tzset);
334
335 async {
336 my $old_tz; # store outside TZ value here
337
338 Coro::on_enter {
339 $old_tz = $ENV{TZ}; # remember the old value
340
341 $ENV{TZ} = "Antarctica/South_Pole";
342 tzset; # enable new value
343 };
344
345 Coro::on_leave {
346 $ENV{TZ} = $old_tz;
347 tzset; # restore old value
348 };
349
350 # at this place, the timezone is Antarctica/South_Pole,
351 # without disturbing the TZ of any other coro.
352 };
353
354This can be used to localise about any resource (locale, uid, current
355working directory etc.) to a block, despite the existance of other
356coros.
357
358Another interesting example implements time-sliced multitasking using
359interval timers (this could obviously be optimised, but does the job):
360
361 # "timeslice" the given block
362 sub timeslice(&) {
363 use Time::HiRes ();
364
365 Coro::on_enter {
366 # on entering the thread, we set an VTALRM handler to cede
367 $SIG{VTALRM} = sub { cede };
368 # and then start the interval timer
369 Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
370 };
371 Coro::on_leave {
372 # on leaving the thread, we stop the interval timer again
373 Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
374 };
375
376 &{+shift};
377 }
378
379 # use like this:
380 timeslice {
381 # The following is an endless loop that would normally
382 # monopolise the process. Since it runs in a timesliced
383 # environment, it will regularly cede to other threads.
384 while () { }
385 };
386
310 387
311=item killall 388=item killall
312 389
313Kills/terminates/cancels all coroutines except the currently running 390Kills/terminates/cancels all coros except the currently running one.
314one. This is useful after a fork, either in the child or the parent, as
315usually only one of them should inherit the running coroutines.
316 391
317Note that while this will try to free some of the main programs resources, 392Note that while this will try to free some of the main interpreter
393resources if the calling coro isn't the main coro, but one
318you cannot free all of them, so if a coroutine that is not the main 394cannot free all of them, so if a coro that is not the main coro
319program calls this function, there will be some one-time resource leak. 395calls this function, there will be some one-time resource leak.
320 396
321=cut 397=cut
322 398
323sub killall { 399sub killall {
324 for (Coro::State::list) { 400 for (Coro::State::list) {
327 } 403 }
328} 404}
329 405
330=back 406=back
331 407
332=head1 COROUTINE OBJECT METHODS 408=head1 CORO OBJECT METHODS
333 409
334These are the methods you can call on coroutine objects (or to create 410These are the methods you can call on coro objects (or to create
335them). 411them).
336 412
337=over 4 413=over 4
338 414
339=item new Coro \&sub [, @args...] 415=item new Coro \&sub [, @args...]
340 416
341Create a new coroutine and return it. When the sub returns, the coroutine 417Create a new coro and return it. When the sub returns, the coro
342automatically terminates as if C<terminate> with the returned values were 418automatically terminates as if C<terminate> with the returned values were
343called. To make the coroutine run you must first put it into the ready 419called. To make the coro run you must first put it into the ready
344queue by calling the ready method. 420queue by calling the ready method.
345 421
346See C<async> and C<Coro::State::new> for additional info about the 422See C<async> and C<Coro::State::new> for additional info about the
347coroutine environment. 423coro environment.
348 424
349=cut 425=cut
350 426
351sub _terminate { 427sub _coro_run {
352 terminate &{+shift}; 428 terminate &{+shift};
353} 429}
354 430
355=item $success = $coroutine->ready 431=item $success = $coro->ready
356 432
357Put the given coroutine into the end of its ready queue (there is one 433Put the given coro into the end of its ready queue (there is one
358queue for each priority) and return true. If the coroutine is already in 434queue for each priority) and return true. If the coro is already in
359the ready queue, do nothing and return false. 435the ready queue, do nothing and return false.
360 436
361This ensures that the scheduler will resume this coroutine automatically 437This ensures that the scheduler will resume this coro automatically
362once all the coroutines of higher priority and all coroutines of the same 438once all the coro of higher priority and all coro of the same
363priority that were put into the ready queue earlier have been resumed. 439priority that were put into the ready queue earlier have been resumed.
364 440
441=item $coro->suspend
442
443Suspends the specified coro. A suspended coro works just like any other
444coro, except that the scheduler will not select a suspended coro for
445execution.
446
447Suspending a coro can be useful when you want to keep the coro from
448running, but you don't want to destroy it, or when you want to temporarily
449freeze a coro (e.g. for debugging) to resume it later.
450
451A scenario for the former would be to suspend all (other) coros after a
452fork and keep them alive, so their destructors aren't called, but new
453coros can be created.
454
455=item $coro->resume
456
457If the specified coro was suspended, it will be resumed. Note that when
458the coro was in the ready queue when it was suspended, it might have been
459unreadied by the scheduler, so an activation might have been lost.
460
461To avoid this, it is best to put a suspended coro into the ready queue
462unconditionally, as every synchronisation mechanism must protect itself
463against spurious wakeups, and the one in the Coro family certainly do
464that.
465
365=item $is_ready = $coroutine->is_ready 466=item $is_ready = $coro->is_ready
366 467
367Return whether the coroutine is currently the ready queue or not, 468Returns true iff the Coro object is in the ready queue. Unless the Coro
469object gets destroyed, it will eventually be scheduled by the scheduler.
368 470
471=item $is_running = $coro->is_running
472
473Returns true iff the Coro object is currently running. Only one Coro object
474can ever be in the running state (but it currently is possible to have
475multiple running Coro::States).
476
477=item $is_suspended = $coro->is_suspended
478
479Returns true iff this Coro object has been suspended. Suspended Coros will
480not ever be scheduled.
481
369=item $coroutine->cancel (arg...) 482=item $coro->cancel (arg...)
370 483
371Terminates the given coroutine and makes it return the given arguments as 484Terminates the given Coro and makes it return the given arguments as
372status (default: the empty list). Never returns if the coroutine is the 485status (default: the empty list). Never returns if the Coro is the
373current coroutine. 486current Coro.
374 487
375=cut 488=cut
376 489
377sub cancel { 490sub cancel {
378 my $self = shift; 491 my $self = shift;
379 492
380 if ($current == $self) { 493 if ($current == $self) {
381 terminate @_; 494 terminate @_;
382 } else { 495 } else {
383 $self->{_status} = [@_]; 496 $self->{_status} = [@_];
384 $self->_cancel; 497 Coro::State::cancel $self;
385 } 498 }
386} 499}
387 500
388=item $coroutine->schedule_to 501=item $coro->schedule_to
389 502
390Puts the current coroutine to sleep (like C<Coro::schedule>), but instead 503Puts the current coro to sleep (like C<Coro::schedule>), but instead
391of continuing with the next coro from the ready queue, always switch to 504of continuing with the next coro from the ready queue, always switch to
392the given coroutine object (regardless of priority etc.). The readyness 505the given coro object (regardless of priority etc.). The readyness
393state of that coroutine isn't changed. 506state of that coro isn't changed.
394 507
395This is an advanced method for special cases - I'd love to hear about any 508This is an advanced method for special cases - I'd love to hear about any
396uses for this one. 509uses for this one.
397 510
398=item $coroutine->cede_to 511=item $coro->cede_to
399 512
400Like C<schedule_to>, but puts the current coroutine into the ready 513Like C<schedule_to>, but puts the current coro into the ready
401queue. This has the effect of temporarily switching to the given 514queue. This has the effect of temporarily switching to the given
402coroutine, and continuing some time later. 515coro, and continuing some time later.
403 516
404This is an advanced method for special cases - I'd love to hear about any 517This is an advanced method for special cases - I'd love to hear about any
405uses for this one. 518uses for this one.
406 519
407=item $coroutine->throw ([$scalar]) 520=item $coro->throw ([$scalar])
408 521
409If C<$throw> is specified and defined, it will be thrown as an exception 522If C<$throw> is specified and defined, it will be thrown as an exception
410inside the coroutine at the next convenient point in time. Otherwise 523inside the coro at the next convenient point in time. Otherwise
411clears the exception object. 524clears the exception object.
412 525
413Coro will check for the exception each time a schedule-like-function 526Coro will check for the exception each time a schedule-like-function
414returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down 527returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
415>>, C<< Coro::Handle->readable >> and so on. Most of these functions 528>>, C<< Coro::Handle->readable >> and so on. Most of these functions
417 530
418The exception object will be thrown "as is" with the specified scalar in 531The exception object will be thrown "as is" with the specified scalar in
419C<$@>, i.e. if it is a string, no line number or newline will be appended 532C<$@>, i.e. if it is a string, no line number or newline will be appended
420(unlike with C<die>). 533(unlike with C<die>).
421 534
422This can be used as a softer means than C<cancel> to ask a coroutine to 535This can be used as a softer means than C<cancel> to ask a coro to
423end itself, although there is no guarantee that the exception will lead to 536end itself, although there is no guarantee that the exception will lead to
424termination, and if the exception isn't caught it might well end the whole 537termination, and if the exception isn't caught it might well end the whole
425program. 538program.
426 539
427You might also think of C<throw> as being the moral equivalent of 540You might also think of C<throw> as being the moral equivalent of
428C<kill>ing a coroutine with a signal (in this case, a scalar). 541C<kill>ing a coro with a signal (in this case, a scalar).
429 542
430=item $coroutine->join 543=item $coro->join
431 544
432Wait until the coroutine terminates and return any values given to the 545Wait until the coro terminates and return any values given to the
433C<terminate> or C<cancel> functions. C<join> can be called concurrently 546C<terminate> or C<cancel> functions. C<join> can be called concurrently
434from multiple coroutines, and all will be resumed and given the status 547from multiple coro, and all will be resumed and given the status
435return once the C<$coroutine> terminates. 548return once the C<$coro> terminates.
436 549
437=cut 550=cut
438 551
439sub join { 552sub join {
440 my $self = shift; 553 my $self = shift;
451 } 564 }
452 565
453 wantarray ? @{$self->{_status}} : $self->{_status}[0]; 566 wantarray ? @{$self->{_status}} : $self->{_status}[0];
454} 567}
455 568
456=item $coroutine->on_destroy (\&cb) 569=item $coro->on_destroy (\&cb)
457 570
458Registers a callback that is called when this coroutine gets destroyed, 571Registers a callback that is called when this coro gets destroyed,
459but before it is joined. The callback gets passed the terminate arguments, 572but before it is joined. The callback gets passed the terminate arguments,
460if any, and I<must not> die, under any circumstances. 573if any, and I<must not> die, under any circumstances.
461 574
462=cut 575=cut
463 576
465 my ($self, $cb) = @_; 578 my ($self, $cb) = @_;
466 579
467 push @{ $self->{_on_destroy} }, $cb; 580 push @{ $self->{_on_destroy} }, $cb;
468} 581}
469 582
470=item $oldprio = $coroutine->prio ($newprio) 583=item $oldprio = $coro->prio ($newprio)
471 584
472Sets (or gets, if the argument is missing) the priority of the 585Sets (or gets, if the argument is missing) the priority of the
473coroutine. Higher priority coroutines get run before lower priority 586coro. Higher priority coro get run before lower priority
474coroutines. Priorities are small signed integers (currently -4 .. +3), 587coro. Priorities are small signed integers (currently -4 .. +3),
475that you can refer to using PRIO_xxx constants (use the import tag :prio 588that you can refer to using PRIO_xxx constants (use the import tag :prio
476to get then): 589to get then):
477 590
478 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 591 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
479 3 > 1 > 0 > -1 > -3 > -4 592 3 > 1 > 0 > -1 > -3 > -4
480 593
481 # set priority to HIGH 594 # set priority to HIGH
482 current->prio(PRIO_HIGH); 595 current->prio (PRIO_HIGH);
483 596
484The idle coroutine ($Coro::idle) always has a lower priority than any 597The idle coro ($Coro::idle) always has a lower priority than any
485existing coroutine. 598existing coro.
486 599
487Changing the priority of the current coroutine will take effect immediately, 600Changing the priority of the current coro will take effect immediately,
488but changing the priority of coroutines in the ready queue (but not 601but changing the priority of coro in the ready queue (but not
489running) will only take effect after the next schedule (of that 602running) will only take effect after the next schedule (of that
490coroutine). This is a bug that will be fixed in some future version. 603coro). This is a bug that will be fixed in some future version.
491 604
492=item $newprio = $coroutine->nice ($change) 605=item $newprio = $coro->nice ($change)
493 606
494Similar to C<prio>, but subtract the given value from the priority (i.e. 607Similar to C<prio>, but subtract the given value from the priority (i.e.
495higher values mean lower priority, just as in unix). 608higher values mean lower priority, just as in unix).
496 609
497=item $olddesc = $coroutine->desc ($newdesc) 610=item $olddesc = $coro->desc ($newdesc)
498 611
499Sets (or gets in case the argument is missing) the description for this 612Sets (or gets in case the argument is missing) the description for this
500coroutine. This is just a free-form string you can associate with a 613coro. This is just a free-form string you can associate with a
501coroutine. 614coro.
502 615
503This method simply sets the C<< $coroutine->{desc} >> member to the given 616This method simply sets the C<< $coro->{desc} >> member to the given
504string. You can modify this member directly if you wish. 617string. You can modify this member directly if you wish.
505 618
506=cut 619=cut
507 620
508sub desc { 621sub desc {
522 635
523=over 4 636=over 4
524 637
525=item Coro::nready 638=item Coro::nready
526 639
527Returns the number of coroutines that are currently in the ready state, 640Returns the number of coro that are currently in the ready state,
528i.e. that can be switched to by calling C<schedule> directory or 641i.e. that can be switched to by calling C<schedule> directory or
529indirectly. The value C<0> means that the only runnable coroutine is the 642indirectly. The value C<0> means that the only runnable coro is the
530currently running one, so C<cede> would have no effect, and C<schedule> 643currently running one, so C<cede> would have no effect, and C<schedule>
531would cause a deadlock unless there is an idle handler that wakes up some 644would cause a deadlock unless there is an idle handler that wakes up some
532coroutines. 645coro.
533 646
534=item my $guard = Coro::guard { ... } 647=item my $guard = Coro::guard { ... }
535 648
536This creates and returns a guard object. Nothing happens until the object 649This function still exists, but is deprecated. Please use the
537gets destroyed, in which case the codeblock given as argument will be 650C<Guard::guard> function instead.
538executed. This is useful to free locks or other resources in case of a
539runtime error or when the coroutine gets canceled, as in both cases the
540guard block will be executed. The guard object supports only one method,
541C<< ->cancel >>, which will keep the codeblock from being executed.
542 651
543Example: set some flag and clear it again when the coroutine gets canceled
544or the function returns:
545
546 sub do_something {
547 my $guard = Coro::guard { $busy = 0 };
548 $busy = 1;
549
550 # do something that requires $busy to be true
551 }
552
553=cut 652=cut
554 653
555sub guard(&) { 654BEGIN { *guard = \&Guard::guard }
556 bless \(my $cb = $_[0]), "Coro::guard"
557}
558
559sub Coro::guard::cancel {
560 ${$_[0]} = sub { };
561}
562
563sub Coro::guard::DESTROY {
564 ${$_[0]}->();
565}
566
567 655
568=item unblock_sub { ... } 656=item unblock_sub { ... }
569 657
570This utility function takes a BLOCK or code reference and "unblocks" it, 658This utility function takes a BLOCK or code reference and "unblocks" it,
571returning a new coderef. Unblocking means that calling the new coderef 659returning a new coderef. Unblocking means that calling the new coderef
572will return immediately without blocking, returning nothing, while the 660will return immediately without blocking, returning nothing, while the
573original code ref will be called (with parameters) from within another 661original code ref will be called (with parameters) from within another
574coroutine. 662coro.
575 663
576The reason this function exists is that many event libraries (such as the 664The reason this function exists is that many event libraries (such as the
577venerable L<Event|Event> module) are not coroutine-safe (a weaker form 665venerable L<Event|Event> module) are not thread-safe (a weaker form
578of thread-safety). This means you must not block within event callbacks, 666of reentrancy). This means you must not block within event callbacks,
579otherwise you might suffer from crashes or worse. The only event library 667otherwise you might suffer from crashes or worse. The only event library
580currently known that is safe to use without C<unblock_sub> is L<EV>. 668currently known that is safe to use without C<unblock_sub> is L<EV>.
581 669
582This function allows your callbacks to block by executing them in another 670This function allows your callbacks to block by executing them in another
583coroutine where it is safe to block. One example where blocking is handy 671coro where it is safe to block. One example where blocking is handy
584is when you use the L<Coro::AIO|Coro::AIO> functions to save results to 672is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
585disk, for example. 673disk, for example.
586 674
587In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when 675In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
588creating event callbacks that want to block. 676creating event callbacks that want to block.
589 677
590If your handler does not plan to block (e.g. simply sends a message to 678If your handler does not plan to block (e.g. simply sends a message to
591another coroutine, or puts some other coroutine into the ready queue), 679another coro, or puts some other coro into the ready queue), there is
592there is no reason to use C<unblock_sub>. 680no reason to use C<unblock_sub>.
593 681
594Note that you also need to use C<unblock_sub> for any other callbacks that 682Note that you also need to use C<unblock_sub> for any other callbacks that
595are indirectly executed by any C-based event loop. For example, when you 683are indirectly executed by any C-based event loop. For example, when you
596use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it 684use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
597provides callbacks that are the result of some event callback, then you 685provides callbacks that are the result of some event callback, then you
627 unshift @unblock_queue, [$cb, @_]; 715 unshift @unblock_queue, [$cb, @_];
628 $unblock_scheduler->ready; 716 $unblock_scheduler->ready;
629 } 717 }
630} 718}
631 719
632=item $cb = Coro::rouse_cb 720=item $cb = rouse_cb
633 721
634Create and return a "rouse callback". That's a code reference that, when 722Create and return a "rouse callback". That's a code reference that,
635called, will save its arguments and notify the owner coroutine of the 723when called, will remember a copy of its arguments and notify the owner
636callback. 724coro of the callback.
637 725
638See the next function. 726See the next function.
639 727
640=item @args = Coro::rouse_wait [$cb] 728=item @args = rouse_wait [$cb]
641 729
642Wait for the specified rouse callback (or the last one tht was created in 730Wait for the specified rouse callback (or the last one that was created in
643this coroutine). 731this coro).
644 732
645As soon as the callback is invoked (or when the calback was invoked before 733As soon as the callback is invoked (or when the callback was invoked
646C<rouse_wait>), it will return a copy of the arguments originally passed 734before C<rouse_wait>), it will return the arguments originally passed to
647to the rouse callback. 735the rouse callback. In scalar context, that means you get the I<last>
736argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
737statement at the end.
648 738
649See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. 739See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
650 740
651=back 741=back
652 742
654 744
6551; 7451;
656 746
657=head1 HOW TO WAIT FOR A CALLBACK 747=head1 HOW TO WAIT FOR A CALLBACK
658 748
659It is very common for a coroutine to wait for some callback to be 749It is very common for a coro to wait for some callback to be
660called. This occurs naturally when you use coroutines in an otherwise 750called. This occurs naturally when you use coro in an otherwise
661event-based program, or when you use event-based libraries. 751event-based program, or when you use event-based libraries.
662 752
663These typically register a callback for some event, and call that callback 753These typically register a callback for some event, and call that callback
664when the event occured. In a coroutine, however, you typically want to 754when the event occured. In a coro, however, you typically want to
665just wait for the event, simplyifying things. 755just wait for the event, simplyifying things.
666 756
667For example C<< AnyEvent->child >> registers a callback to be called when 757For example C<< AnyEvent->child >> registers a callback to be called when
668a specific child has exited: 758a specific child has exited:
669 759
670 my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... }); 760 my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
671 761
672But from withina coroutine, you often just want to write this: 762But from within a coro, you often just want to write this:
673 763
674 my $status = wait_for_child $pid; 764 my $status = wait_for_child $pid;
675 765
676Coro offers two functions specifically designed to make this easy, 766Coro offers two functions specifically designed to make this easy,
677C<Coro::rouse_cb> and C<Coro::rouse_wait>. 767C<Coro::rouse_cb> and C<Coro::rouse_wait>.
678 768
679The first function, C<rouse_cb>, generates and returns a callback that, 769The first function, C<rouse_cb>, generates and returns a callback that,
680when invoked, will save it's arguments and notify the coroutine that 770when invoked, will save its arguments and notify the coro that
681created the callback. 771created the callback.
682 772
683The second function, C<rouse_wait>, waits for the callback to be called 773The second function, C<rouse_wait>, waits for the callback to be called
684(by calling C<schedule> to go to sleep) and returns the arguments 774(by calling C<schedule> to go to sleep) and returns the arguments
685originally passed to the callback. 775originally passed to the callback.
700you can roll your own, using C<schedule>: 790you can roll your own, using C<schedule>:
701 791
702 sub wait_for_child($) { 792 sub wait_for_child($) {
703 my ($pid) = @_; 793 my ($pid) = @_;
704 794
705 # store the current coroutine in $current, 795 # store the current coro in $current,
706 # and provide result variables for the closure passed to ->child 796 # and provide result variables for the closure passed to ->child
707 my $current = $Coro::current; 797 my $current = $Coro::current;
708 my ($done, $rstatus); 798 my ($done, $rstatus);
709 799
710 # pass a closure to ->child 800 # pass a closure to ->child
726 816
727=item fork with pthread backend 817=item fork with pthread backend
728 818
729When Coro is compiled using the pthread backend (which isn't recommended 819When Coro is compiled using the pthread backend (which isn't recommended
730but required on many BSDs as their libcs are completely broken), then 820but required on many BSDs as their libcs are completely broken), then
731coroutines will not survive a fork. There is no known workaround except to 821coro will not survive a fork. There is no known workaround except to
732fix your libc and use a saner backend. 822fix your libc and use a saner backend.
733 823
734=item perl process emulation ("threads") 824=item perl process emulation ("threads")
735 825
736This module is not perl-pseudo-thread-safe. You should only ever use this 826This module is not perl-pseudo-thread-safe. You should only ever use this
737module from the same thread (this requirement might be removed in the 827module from the first thread (this requirement might be removed in the
738future to allow per-thread schedulers, but Coro::State does not yet allow 828future to allow per-thread schedulers, but Coro::State does not yet allow
739this). I recommend disabling thread support and using processes, as having 829this). I recommend disabling thread support and using processes, as having
740the windows process emulation enabled under unix roughly halves perl 830the windows process emulation enabled under unix roughly halves perl
741performance, even when not used. 831performance, even when not used.
742 832
743=item coroutine switching not signal safe 833=item coro switching is not signal safe
744 834
745You must not switch to another coroutine from within a signal handler 835You must not switch to another coro from within a signal handler (only
746(only relevant with %SIG - most event libraries provide safe signals). 836relevant with %SIG - most event libraries provide safe signals), I<unless>
837you are sure you are not interrupting a Coro function.
747 838
748That means you I<MUST NOT> call any function that might "block" the 839That means you I<MUST NOT> call any function that might "block" the
749current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or 840current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
750anything that calls those. Everything else, including calling C<ready>, 841anything that calls those. Everything else, including calling C<ready>,
751works. 842works.
752 843
753=back 844=back
754 845
755 846
847=head1 WINDOWS PROCESS EMULATION
848
849A great many people seem to be confused about ithreads (for example, Chip
850Salzenberg called me unintelligent, incapable, stupid and gullible,
851while in the same mail making rather confused statements about perl
852ithreads (for example, that memory or files would be shared), showing his
853lack of understanding of this area - if it is hard to understand for Chip,
854it is probably not obvious to everybody).
855
856What follows is an ultra-condensed version of my talk about threads in
857scripting languages given onthe perl workshop 2009:
858
859The so-called "ithreads" were originally implemented for two reasons:
860first, to (badly) emulate unix processes on native win32 perls, and
861secondly, to replace the older, real thread model ("5.005-threads").
862
863It does that by using threads instead of OS processes. The difference
864between processes and threads is that threads share memory (and other
865state, such as files) between threads within a single process, while
866processes do not share anything (at least not semantically). That
867means that modifications done by one thread are seen by others, while
868modifications by one process are not seen by other processes.
869
870The "ithreads" work exactly like that: when creating a new ithreads
871process, all state is copied (memory is copied physically, files and code
872is copied logically). Afterwards, it isolates all modifications. On UNIX,
873the same behaviour can be achieved by using operating system processes,
874except that UNIX typically uses hardware built into the system to do this
875efficiently, while the windows process emulation emulates this hardware in
876software (rather efficiently, but of course it is still much slower than
877dedicated hardware).
878
879As mentioned before, loading code, modifying code, modifying data
880structures and so on is only visible in the ithreads process doing the
881modification, not in other ithread processes within the same OS process.
882
883This is why "ithreads" do not implement threads for perl at all, only
884processes. What makes it so bad is that on non-windows platforms, you can
885actually take advantage of custom hardware for this purpose (as evidenced
886by the forks module, which gives you the (i-) threads API, just much
887faster).
888
889Sharing data is in the i-threads model is done by transfering data
890structures between threads using copying semantics, which is very slow -
891shared data simply does not exist. Benchmarks using i-threads which are
892communication-intensive show extremely bad behaviour with i-threads (in
893fact, so bad that Coro, which cannot take direct advantage of multiple
894CPUs, is often orders of magnitude faster because it shares data using
895real threads, refer to my talk for details).
896
897As summary, i-threads *use* threads to implement processes, while
898the compatible forks module *uses* processes to emulate, uhm,
899processes. I-threads slow down every perl program when enabled, and
900outside of windows, serve no (or little) practical purpose, but
901disadvantages every single-threaded Perl program.
902
903This is the reason that I try to avoid the name "ithreads", as it is
904misleading as it implies that it implements some kind of thread model for
905perl, and prefer the name "windows process emulation", which describes the
906actual use and behaviour of it much better.
907
756=head1 SEE ALSO 908=head1 SEE ALSO
757 909
758Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. 910Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
759 911
760Debugging: L<Coro::Debug>. 912Debugging: L<Coro::Debug>.
761 913
762Support/Utility: L<Coro::Specific>, L<Coro::Util>. 914Support/Utility: L<Coro::Specific>, L<Coro::Util>.
763 915
764Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, 916Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
765L<Coro::SemaphoreSet>, L<Coro::RWLock>. 917L<Coro::SemaphoreSet>, L<Coro::RWLock>.
766 918
767IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>. 919I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
768 920
769Compatibility: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for 921Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
770a better-working alternative), L<Coro::BDB>, L<Coro::Storable>, 922a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
771L<Coro::Select>. 923L<Coro::Select>.
772 924
773XS API: L<Coro::MakeMaker>. 925XS API: L<Coro::MakeMaker>.
774 926
775Low level Configuration, Coroutine Environment: L<Coro::State>. 927Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
776 928
777=head1 AUTHOR 929=head1 AUTHOR
778 930
779 Marc Lehmann <schmorp@schmorp.de> 931 Marc Lehmann <schmorp@schmorp.de>
780 http://home.schmorp.de/ 932 http://home.schmorp.de/

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