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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 continuations in general, most often 34This module collection manages continuations in general, most often in
35in the form of cooperative threads (also called coroutines in the 35the form of cooperative threads (also called coros, or simply "coro"
36documentation). They are similar to kernel threads but don't (in general) 36in the documentation). They are similar to kernel threads but don't (in
37run 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
38of thread offered by this module also guarantees you that it will not 38specific flavor of thread offered by this module also guarantees you that
39switch between threads unless necessary, at easily-identified points in 39it will not switch between threads unless necessary, at easily-identified
40your program, so locking and parallel access are rarely an issue, making 40points in your program, so locking and parallel access are rarely an
41thread programming much safer and easier than using other thread models. 41issue, making thread programming much safer and easier than using other
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 threads 47a full shared address space, which makes communication between threads
46very easy. And threads 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 thread is defined as "callchain + lexical variables + 60In this module, a thread is defined as "callchain + lexical variables +
57@_ + $_ + $@ + $/ + C stack), that is, a thread has its own callchain, 61some package variables + C stack), that is, a thread has its own callchain,
58its 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
59variables (see L<Coro::State> for more configuration and background info). 63variables (see L<Coro::State> for more configuration and background info).
60 64
61See 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
62module family is quite large. 66module family is quite large.
63 67
64=cut 68=cut
65 69
66package Coro; 70package Coro;
67 71
68use strict qw(vars subs); 72use common::sense;
69no warnings "uninitialized"; 73
74use Carp ();
70 75
71use Guard (); 76use Guard ();
72 77
73use Coro::State; 78use Coro::State;
74 79
75use base qw(Coro::State Exporter); 80use base qw(Coro::State Exporter);
76 81
77our $idle; # idle handler 82our $idle; # idle handler
78our $main; # main coroutine 83our $main; # main coro
79our $current; # current coroutine 84our $current; # current coro
80 85
81our $VERSION = 5.13; 86our $VERSION = 5.25;
82 87
83our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); 88our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
84our %EXPORT_TAGS = ( 89our %EXPORT_TAGS = (
85 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 90 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
86); 91);
87our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); 92our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
88 93
90 95
91=over 4 96=over 4
92 97
93=item $Coro::main 98=item $Coro::main
94 99
95This variable stores the coroutine object that represents the main 100This variable stores the Coro object that represents the main
96program. While you cna C<ready> it and do most other things you can do to 101program. While you cna C<ready> it and do most other things you can do to
97coroutines, it is mainly useful to compare again C<$Coro::current>, to see 102coro, it is mainly useful to compare again C<$Coro::current>, to see
98whether you are running in the main program or not. 103whether you are running in the main program or not.
99 104
100=cut 105=cut
101 106
102# $main is now being initialised by Coro::State 107# $main is now being initialised by Coro::State
103 108
104=item $Coro::current 109=item $Coro::current
105 110
106The coroutine object representing the current coroutine (the last 111The Coro object representing the current coro (the last
107coroutine that the Coro scheduler switched to). The initial value is 112coro that the Coro scheduler switched to). The initial value is
108C<$Coro::main> (of course). 113C<$Coro::main> (of course).
109 114
110This 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
111value 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
112not otherwise modify the variable itself. 117not otherwise modify the variable itself.
113 118
114=cut 119=cut
115 120
116sub current() { $current } # [DEPRECATED] 121sub current() { $current } # [DEPRECATED]
119 124
120This 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
121usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is 126usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
122pretty low-level functionality. 127pretty low-level functionality.
123 128
124This variable stores either a coroutine or a callback. 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).
125 131
126If it is a callback, the it is called whenever the scheduler finds no 132The default implementation dies with "FATAL: deadlock detected.", followed
127ready coroutines to run. The default implementation prints "FATAL: 133by a thread listing, because the program has no other way to continue.
128deadlock detected" and exits, because the program has no other way to
129continue.
130
131If it is a coroutine object, then this object will be readied (without
132invoking any ready hooks, however) when the scheduler finds no other ready
133coroutines to run.
134 134
135This hook is overwritten by modules such as C<Coro::EV> and 135This hook is overwritten by modules such as C<Coro::EV> and
136C<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
137coroutine so the scheduler can run it. 137coro so the scheduler can run it.
138 138
139Note that the callback I<must not>, under any circumstances, block
140the current coroutine. Normally, this is achieved by having an "idle
141coroutine" that calls the event loop and then blocks again, and then
142readying that coroutine in the idle handler, or by simply placing the idle
143coroutine in this variable.
144
145See 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.
146technique.
147 140
148Please note that if your callback recursively invokes perl (e.g. for event
149handlers), then it must be prepared to be called recursively itself.
150
151=cut 141=cut
152 142
153$idle = sub { 143# ||= because other modules could have provided their own by now
154 require Carp; 144$idle ||= new Coro sub {
155 Carp::croak ("FATAL: deadlock detected"); 145 require Coro::Debug;
146 die "FATAL: deadlock detected.\n"
147 . Coro::Debug::ps_listing ();
156}; 148};
157 149
158# this coroutine is necessary because a coroutine 150# this coro is necessary because a coro
159# cannot destroy itself. 151# cannot destroy itself.
160our @destroy; 152our @destroy;
161our $manager; 153our $manager;
162 154
163$manager = new Coro sub { 155$manager = new Coro sub {
164 while () { 156 while () {
165 Coro::_cancel shift @destroy 157 Coro::State::cancel shift @destroy
166 while @destroy; 158 while @destroy;
167 159
168 &schedule; 160 &schedule;
169 } 161 }
170}; 162};
171$manager->{desc} = "[coro manager]"; 163$manager->{desc} = "[coro manager]";
172$manager->prio (PRIO_MAX); 164$manager->prio (PRIO_MAX);
173 165
174=back 166=back
175 167
176=head1 SIMPLE COROUTINE CREATION 168=head1 SIMPLE CORO CREATION
177 169
178=over 4 170=over 4
179 171
180=item async { ... } [@args...] 172=item async { ... } [@args...]
181 173
182Create a new coroutine and return its coroutine object (usually 174Create a new coro and return its Coro object (usually
183unused). The coroutine will be put into the ready queue, so 175unused). The coro will be put into the ready queue, so
184it will start running automatically on the next scheduler run. 176it will start running automatically on the next scheduler run.
185 177
186The first argument is a codeblock/closure that should be executed in the 178The first argument is a codeblock/closure that should be executed in the
187coroutine. When it returns argument returns the coroutine is automatically 179coro. When it returns argument returns the coro is automatically
188terminated. 180terminated.
189 181
190The remaining arguments are passed as arguments to the closure. 182The remaining arguments are passed as arguments to the closure.
191 183
192See the C<Coro::State::new> constructor for info about the coroutine 184See the C<Coro::State::new> constructor for info about the coro
193environment in which coroutines are executed. 185environment in which coro are executed.
194 186
195Calling 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
196the coroutine. Likewise, when the coroutine dies, the program will exit, 188the coro. Likewise, when the coro dies, the program will exit,
197just as it would in the main program. 189just as it would in the main program.
198 190
199If you do not want that, you can provide a default C<die> handler, or 191If you do not want that, you can provide a default C<die> handler, or
200simply avoid dieing (by use of C<eval>). 192simply avoid dieing (by use of C<eval>).
201 193
202Example: Create a new coroutine that just prints its arguments. 194Example: Create a new coro that just prints its arguments.
203 195
204 async { 196 async {
205 print "@_\n"; 197 print "@_\n";
206 } 1,2,3,4; 198 } 1,2,3,4;
207 199
208=cut
209
210sub async(&@) {
211 my $coro = new Coro @_;
212 $coro->ready;
213 $coro
214}
215
216=item async_pool { ... } [@args...] 200=item async_pool { ... } [@args...]
217 201
218Similar 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
219terminate or join on it (although you are allowed to), and you get a 203terminate or join on it (although you are allowed to), and you get a
220coroutine that might have executed other code already (which can be good 204coro that might have executed other code already (which can be good
221or bad :). 205or bad :).
222 206
223On the plus side, this function is about twice as fast as creating (and 207On the plus side, this function is about twice as fast as creating (and
224destroying) a completely new coroutine, so if you need a lot of generic 208destroying) a completely new coro, so if you need a lot of generic
225coroutines in quick successsion, use C<async_pool>, not C<async>. 209coros in quick successsion, use C<async_pool>, not C<async>.
226 210
227The code 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
228issued in case of an exception instead of terminating the program, as 212issued in case of an exception instead of terminating the program, as
229C<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>
230will 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,
231which somehow defeats the purpose of pooling (but is fine in the 215which somehow defeats the purpose of pooling (but is fine in the
232exceptional case). 216exceptional case).
233 217
234The priority will be reset to C<0> after each run, tracing will be 218The priority will be reset to C<0> after each run, tracing will be
235disabled, the description will be reset and the default output filehandle 219disabled, the description will be reset and the default output filehandle
236gets restored, so you can change all these. Otherwise the coroutine will 220gets restored, so you can change all these. Otherwise the coro will
237be 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
238stuff such as C<$/> you I<must needs> revert that change, which is most 222stuff such as C<$/> you I<must needs> revert that change, which is most
239simply done by using local as in: C<< local $/ >>. 223simply done by using local as in: C<< local $/ >>.
240 224
241The idle pool size is limited to C<8> idle coroutines (this can be 225The idle pool size is limited to C<8> idle coros (this can be
242adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle 226adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
243coros as required. 227coros as required.
244 228
245If you are concerned about pooled coroutines growing a lot because a 229If you are concerned about pooled coros growing a lot because a
246single 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
247{ 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
248addition to that, when the stacks used by a handler grows larger than 32kb 232addition to that, when the stacks used by a handler grows larger than 32kb
249(adjustable via $Coro::POOL_RSS) it will also be destroyed. 233(adjustable via $Coro::POOL_RSS) it will also be destroyed.
250 234
267=back 251=back
268 252
269=head1 STATIC METHODS 253=head1 STATIC METHODS
270 254
271Static methods are actually functions that implicitly operate on the 255Static methods are actually functions that implicitly operate on the
272current coroutine. 256current coro.
273 257
274=over 4 258=over 4
275 259
276=item schedule 260=item schedule
277 261
278Calls the scheduler. The scheduler will find the next coroutine that is 262Calls the scheduler. The scheduler will find the next coro that is
279to be run from the ready queue and switches to it. The next coroutine 263to be run from the ready queue and switches to it. The next coro
280to be run is simply the one with the highest priority that is longest 264to be run is simply the one with the highest priority that is longest
281in its ready queue. If there is no coroutine ready, it will clal the 265in its ready queue. If there is no coro ready, it will call the
282C<$Coro::idle> hook. 266C<$Coro::idle> hook.
283 267
284Please note that the current coroutine will I<not> be put into the ready 268Please note that the current coro will I<not> be put into the ready
285queue, so calling this function usually means you will never be called 269queue, so calling this function usually means you will never be called
286again unless something else (e.g. an event handler) calls C<< ->ready >>, 270again unless something else (e.g. an event handler) calls C<< ->ready >>,
287thus waking you up. 271thus waking you up.
288 272
289This makes C<schedule> I<the> generic method to use to block the current 273This makes C<schedule> I<the> generic method to use to block the current
290coroutine and wait for events: first you remember the current coroutine in 274coro and wait for events: first you remember the current coro in
291a variable, then arrange for some callback of yours to call C<< ->ready 275a variable, then arrange for some callback of yours to call C<< ->ready
292>> on that once some event happens, and last you call C<schedule> to put 276>> on that once some event happens, and last you call C<schedule> to put
293yourself to sleep. Note that a lot of things can wake your coroutine up, 277yourself to sleep. Note that a lot of things can wake your coro up,
294so you need to check whether the event indeed happened, e.g. by storing the 278so you need to check whether the event indeed happened, e.g. by storing the
295status in a variable. 279status in a variable.
296 280
297See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks. 281See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
298 282
299=item cede 283=item cede
300 284
301"Cede" to other coroutines. This function puts the current coroutine into 285"Cede" to other coros. This function puts the current coro into
302the ready queue and calls C<schedule>, which has the effect of giving 286the ready queue and calls C<schedule>, which has the effect of giving
303up the current "timeslice" to other coroutines of the same or higher 287up the current "timeslice" to other coros of the same or higher
304priority. Once your coroutine gets its turn again it will automatically be 288priority. Once your coro gets its turn again it will automatically be
305resumed. 289resumed.
306 290
307This function is often called C<yield> in other languages. 291This function is often called C<yield> in other languages.
308 292
309=item Coro::cede_notself 293=item Coro::cede_notself
310 294
311Works like cede, but is not exported by default and will cede to I<any> 295Works like cede, but is not exported by default and will cede to I<any>
312coroutine, regardless of priority. This is useful sometimes to ensure 296coro, regardless of priority. This is useful sometimes to ensure
313progress is made. 297progress is made.
314 298
315=item terminate [arg...] 299=item terminate [arg...]
316 300
317Terminates the current coroutine with the given status values (see L<cancel>). 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
344 };
345
346 Coro::on_leave {
347 $ENV{TZ} = $old_tz;
348 tzset; # restore old value
349 };
350
351 # at this place, the timezone is Antarctica/South_Pole,
352 # without disturbing the TZ of any other coro.
353 };
354
355This can be used to localise about any resource (locale, uid, current
356working directory etc.) to a block, despite the existance of other
357coros.
358
359Another interesting example implements time-sliced multitasking using
360interval timers (this could obviously be optimised, but does the job):
361
362 # "timeslice" the given block
363 sub timeslice(&) {
364 use Time::HiRes ();
365
366 Coro::on_enter {
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 };
376
377 &{+shift};
378 }
379
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
318 388
319=item killall 389=item killall
320 390
321Kills/terminates/cancels all coroutines except the currently running 391Kills/terminates/cancels all coros except the currently running one.
322one. This can be useful after a fork, either in the child or the parent,
323as usually only one of them should inherit the running coroutines.
324 392
325Note that in the implementation, destructors run as normal, making this
326function not so useful after a fork. Future versions of this function
327might try to free resources without running any code.
328
329Note that while this will try to free some of the main programs resources, 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
330you cannot free all of them, so if a coroutine that is not the main 395cannot free all of them, so if a coro that is not the main coro
331program calls this function, there will be some one-time resource leak. 396calls this function, there will be some one-time resource leak.
332 397
333=cut 398=cut
334 399
335sub killall { 400sub killall {
336 for (Coro::State::list) { 401 for (Coro::State::list) {
339 } 404 }
340} 405}
341 406
342=back 407=back
343 408
344=head1 COROUTINE OBJECT METHODS 409=head1 CORO OBJECT METHODS
345 410
346These are the methods you can call on coroutine objects (or to create 411These are the methods you can call on coro objects (or to create
347them). 412them).
348 413
349=over 4 414=over 4
350 415
351=item new Coro \&sub [, @args...] 416=item new Coro \&sub [, @args...]
352 417
353Create 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
354automatically terminates as if C<terminate> with the returned values were 419automatically terminates as if C<terminate> with the returned values were
355called. To make the coroutine run you must first put it into the ready 420called. To make the coro run you must first put it into the ready
356queue by calling the ready method. 421queue by calling the ready method.
357 422
358See 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
359coroutine environment. 424coro environment.
360 425
361=cut 426=cut
362 427
363sub _coro_run { 428sub _coro_run {
364 terminate &{+shift}; 429 terminate &{+shift};
365} 430}
366 431
367=item $success = $coroutine->ready 432=item $success = $coro->ready
368 433
369Put the given coroutine into the end of its ready queue (there is one 434Put the given coro into the end of its ready queue (there is one
370queue for each priority) and return true. If the coroutine is already in 435queue for each priority) and return true. If the coro is already in
371the ready queue, do nothing and return false. 436the ready queue, do nothing and return false.
372 437
373This ensures that the scheduler will resume this coroutine automatically 438This ensures that the scheduler will resume this coro automatically
374once all the coroutines of higher priority and all coroutines of the same 439once all the coro of higher priority and all coro of the same
375priority that were put into the ready queue earlier have been resumed. 440priority that were put into the ready queue earlier have been resumed.
376 441
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
377=item $is_ready = $coroutine->is_ready 467=item $is_ready = $coro->is_ready
378 468
379Return whether 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.
380 471
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
381=item $coroutine->cancel (arg...) 483=item $coro->cancel (arg...)
382 484
383Terminates the given coroutine and makes it return the given arguments as 485Terminates the given Coro and makes it return the given arguments as
384status (default: the empty list). Never returns if the coroutine is the 486status (default: the empty list). Never returns if the Coro is the
385current coroutine. 487current Coro.
386 488
387=cut 489=cut
388 490
389sub cancel { 491sub cancel {
390 my $self = shift; 492 my $self = shift;
391 493
392 if ($current == $self) { 494 if ($current == $self) {
393 terminate @_; 495 terminate @_;
394 } else { 496 } else {
395 $self->{_status} = [@_]; 497 $self->{_status} = [@_];
396 $self->_cancel; 498 Coro::State::cancel $self;
397 } 499 }
398} 500}
399 501
400=item $coroutine->schedule_to 502=item $coro->schedule_to
401 503
402Puts the current coroutine to sleep (like C<Coro::schedule>), but instead 504Puts the current coro to sleep (like C<Coro::schedule>), but instead
403of continuing with the next coro from the ready queue, always switch to 505of continuing with the next coro from the ready queue, always switch to
404the given coroutine object (regardless of priority etc.). The readyness 506the given coro object (regardless of priority etc.). The readyness
405state of that coroutine isn't changed. 507state of that coro isn't changed.
406 508
407This is an advanced method for special cases - I'd love to hear about any 509This is an advanced method for special cases - I'd love to hear about any
408uses for this one. 510uses for this one.
409 511
410=item $coroutine->cede_to 512=item $coro->cede_to
411 513
412Like C<schedule_to>, but puts the current coroutine into the ready 514Like C<schedule_to>, but puts the current coro into the ready
413queue. This has the effect of temporarily switching to the given 515queue. This has the effect of temporarily switching to the given
414coroutine, and continuing some time later. 516coro, and continuing some time later.
415 517
416This is an advanced method for special cases - I'd love to hear about any 518This is an advanced method for special cases - I'd love to hear about any
417uses for this one. 519uses for this one.
418 520
419=item $coroutine->throw ([$scalar]) 521=item $coro->throw ([$scalar])
420 522
421If C<$throw> is specified and defined, it will be thrown as an exception 523If C<$throw> is specified and defined, it will be thrown as an exception
422inside the coroutine at the next convenient point in time. Otherwise 524inside the coro at the next convenient point in time. Otherwise
423clears the exception object. 525clears the exception object.
424 526
425Coro will check for the exception each time a schedule-like-function 527Coro will check for the exception each time a schedule-like-function
426returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down 528returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
427>>, C<< Coro::Handle->readable >> and so on. Most of these functions 529>>, C<< Coro::Handle->readable >> and so on. Most of these functions
429 531
430The exception object will be thrown "as is" with the specified scalar in 532The exception object will be thrown "as is" with the specified scalar in
431C<$@>, i.e. if it is a string, no line number or newline will be appended 533C<$@>, i.e. if it is a string, no line number or newline will be appended
432(unlike with C<die>). 534(unlike with C<die>).
433 535
434This can be used as a softer means than C<cancel> to ask a coroutine to 536This can be used as a softer means than C<cancel> to ask a coro to
435end itself, although there is no guarantee that the exception will lead to 537end itself, although there is no guarantee that the exception will lead to
436termination, and if the exception isn't caught it might well end the whole 538termination, and if the exception isn't caught it might well end the whole
437program. 539program.
438 540
439You might also think of C<throw> as being the moral equivalent of 541You might also think of C<throw> as being the moral equivalent of
440C<kill>ing a coroutine with a signal (in this case, a scalar). 542C<kill>ing a coro with a signal (in this case, a scalar).
441 543
442=item $coroutine->join 544=item $coro->join
443 545
444Wait until the coroutine terminates and return any values given to the 546Wait until the coro terminates and return any values given to the
445C<terminate> or C<cancel> functions. C<join> can be called concurrently 547C<terminate> or C<cancel> functions. C<join> can be called concurrently
446from multiple coroutines, and all will be resumed and given the status 548from multiple coro, and all will be resumed and given the status
447return once the C<$coroutine> terminates. 549return once the C<$coro> terminates.
448 550
449=cut 551=cut
450 552
451sub join { 553sub join {
452 my $self = shift; 554 my $self = shift;
463 } 565 }
464 566
465 wantarray ? @{$self->{_status}} : $self->{_status}[0]; 567 wantarray ? @{$self->{_status}} : $self->{_status}[0];
466} 568}
467 569
468=item $coroutine->on_destroy (\&cb) 570=item $coro->on_destroy (\&cb)
469 571
470Registers a callback that is called when this coroutine gets destroyed, 572Registers a callback that is called when this coro gets destroyed,
471but before it is joined. The callback gets passed the terminate arguments, 573but before it is joined. The callback gets passed the terminate arguments,
472if any, and I<must not> die, under any circumstances. 574if any, and I<must not> die, under any circumstances.
473 575
474=cut 576=cut
475 577
477 my ($self, $cb) = @_; 579 my ($self, $cb) = @_;
478 580
479 push @{ $self->{_on_destroy} }, $cb; 581 push @{ $self->{_on_destroy} }, $cb;
480} 582}
481 583
482=item $oldprio = $coroutine->prio ($newprio) 584=item $oldprio = $coro->prio ($newprio)
483 585
484Sets (or gets, if the argument is missing) the priority of the 586Sets (or gets, if the argument is missing) the priority of the
485coroutine. Higher priority coroutines get run before lower priority 587coro. Higher priority coro get run before lower priority
486coroutines. Priorities are small signed integers (currently -4 .. +3), 588coro. Priorities are small signed integers (currently -4 .. +3),
487that 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
488to get then): 590to get then):
489 591
490 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
491 3 > 1 > 0 > -1 > -3 > -4 593 3 > 1 > 0 > -1 > -3 > -4
492 594
493 # set priority to HIGH 595 # set priority to HIGH
494 current->prio(PRIO_HIGH); 596 current->prio (PRIO_HIGH);
495 597
496The idle coroutine ($Coro::idle) always has a lower priority than any 598The idle coro ($Coro::idle) always has a lower priority than any
497existing coroutine. 599existing coro.
498 600
499Changing the priority of the current coroutine will take effect immediately, 601Changing the priority of the current coro will take effect immediately,
500but changing the priority of coroutines in the ready queue (but not 602but changing the priority of coro in the ready queue (but not
501running) will only take effect after the next schedule (of that 603running) will only take effect after the next schedule (of that
502coroutine). 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.
503 605
504=item $newprio = $coroutine->nice ($change) 606=item $newprio = $coro->nice ($change)
505 607
506Similar 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.
507higher values mean lower priority, just as in unix). 609higher values mean lower priority, just as in unix).
508 610
509=item $olddesc = $coroutine->desc ($newdesc) 611=item $olddesc = $coro->desc ($newdesc)
510 612
511Sets (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
512coroutine. This is just a free-form string you can associate with a 614coro. This is just a free-form string you can associate with a
513coroutine. 615coro.
514 616
515This method simply sets the C<< $coroutine->{desc} >> member to the given 617This method simply sets the C<< $coro->{desc} >> member to the given
516string. You can 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:
621
622 sub my_long_function {
623 local $Coro::current->{desc} = "now in my_long_function";
624 ...
625 $Coro::current->{desc} = "my_long_function: phase 1";
626 ...
627 $Coro::current->{desc} = "my_long_function: phase 2";
628 ...
629 }
517 630
518=cut 631=cut
519 632
520sub desc { 633sub desc {
521 my $old = $_[0]{desc}; 634 my $old = $_[0]{desc};
534 647
535=over 4 648=over 4
536 649
537=item Coro::nready 650=item Coro::nready
538 651
539Returns the number of coroutines that are currently in the ready state, 652Returns the number of coro that are currently in the ready state,
540i.e. that can be switched to by calling C<schedule> directory or 653i.e. that can be switched to by calling C<schedule> directory or
541indirectly. The value C<0> means that the only runnable coroutine is the 654indirectly. The value C<0> means that the only runnable coro is the
542currently running one, so C<cede> would have no effect, and C<schedule> 655currently running one, so C<cede> would have no effect, and C<schedule>
543would cause a deadlock unless there is an idle handler that wakes up some 656would cause a deadlock unless there is an idle handler that wakes up some
544coroutines. 657coro.
545 658
546=item my $guard = Coro::guard { ... } 659=item my $guard = Coro::guard { ... }
547 660
548This function still exists, but is deprecated. Please use the 661This function still exists, but is deprecated. Please use the
549C<Guard::guard> function instead. 662C<Guard::guard> function instead.
556 669
557This utility function takes a BLOCK or code reference and "unblocks" it, 670This utility function takes a BLOCK or code reference and "unblocks" it,
558returning a new coderef. Unblocking means that calling the new coderef 671returning a new coderef. Unblocking means that calling the new coderef
559will return immediately without blocking, returning nothing, while the 672will return immediately without blocking, returning nothing, while the
560original code ref will be called (with parameters) from within another 673original code ref will be called (with parameters) from within another
561coroutine. 674coro.
562 675
563The reason this function exists is that many event libraries (such as the 676The reason this function exists is that many event libraries (such as
564venerable L<Event|Event> module) are not coroutine-safe (a weaker form 677the venerable L<Event|Event> module) are not thread-safe (a weaker form
565of reentrancy). This means you must not block within event callbacks, 678of reentrancy). This means you must not block within event callbacks,
566otherwise you might suffer from crashes or worse. The only event library 679otherwise you might suffer from crashes or worse. The only event library
567currently known that is safe to use without C<unblock_sub> is L<EV>. 680currently known that is safe to use without C<unblock_sub> is L<EV> (but
681you might still run into deadlocks if all event loops are blocked).
682
683Coro will try to catch you when you block in the event loop
684("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and
685only works when you do not run your own event loop.
568 686
569This function allows your callbacks to block by executing them in another 687This function allows your callbacks to block by executing them in another
570coroutine 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
571is 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
572disk, for example. 690disk, for example.
573 691
574In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when 692In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
575creating event callbacks that want to block. 693creating event callbacks that want to block.
576 694
577If your handler does not plan to block (e.g. simply sends a message to 695If your handler does not plan to block (e.g. simply sends a message to
578another coroutine, or puts some other coroutine into the ready queue), 696another coro, or puts some other coro into the ready queue), there is
579there is no reason to use C<unblock_sub>. 697no reason to use C<unblock_sub>.
580 698
581Note that you also need to use C<unblock_sub> for any other callbacks that 699Note that you also need to use C<unblock_sub> for any other callbacks that
582are indirectly executed by any C-based event loop. For example, when you 700are indirectly executed by any C-based event loop. For example, when you
583use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it 701use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
584provides callbacks that are the result of some event callback, then you 702provides callbacks that are the result of some event callback, then you
614 unshift @unblock_queue, [$cb, @_]; 732 unshift @unblock_queue, [$cb, @_];
615 $unblock_scheduler->ready; 733 $unblock_scheduler->ready;
616 } 734 }
617} 735}
618 736
619=item $cb = Coro::rouse_cb 737=item $cb = rouse_cb
620 738
621Create and return a "rouse callback". That's a code reference that, 739Create and return a "rouse callback". That's a code reference that,
622when called, will remember a copy of its arguments and notify the owner 740when called, will remember a copy of its arguments and notify the owner
623coroutine of the callback. 741coro of the callback.
624 742
625See the next function. 743See the next function.
626 744
627=item @args = Coro::rouse_wait [$cb] 745=item @args = rouse_wait [$cb]
628 746
629Wait for the specified rouse callback (or the last one that was created in 747Wait for the specified rouse callback (or the last one that was created in
630this coroutine). 748this coro).
631 749
632As soon as the callback is invoked (or when the callback was invoked 750As soon as the callback is invoked (or when the callback was invoked
633before C<rouse_wait>), it will return the arguments originally passed to 751before C<rouse_wait>), it will return the arguments originally passed to
634the rouse callback. 752the rouse callback. In scalar context, that means you get the I<last>
753argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
754statement at the end.
635 755
636See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. 756See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
637 757
638=back 758=back
639 759
640=cut 760=cut
641 761
762for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) {
763 my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"};
764
765 *{"Coro::$module\::new"} = sub {
766 require "Coro/$module.pm";
767
768 # some modules have their new predefined in State.xs, some don't
769 *{"Coro::$module\::new"} = $old
770 if $old;
771
772 goto &{"Coro::$module\::new"};
773 };
774}
775
6421; 7761;
643 777
644=head1 HOW TO WAIT FOR A CALLBACK 778=head1 HOW TO WAIT FOR A CALLBACK
645 779
646It is very common for a coroutine to wait for some callback to be 780It is very common for a coro to wait for some callback to be
647called. This occurs naturally when you use coroutines in an otherwise 781called. This occurs naturally when you use coro in an otherwise
648event-based program, or when you use event-based libraries. 782event-based program, or when you use event-based libraries.
649 783
650These typically register a callback for some event, and call that callback 784These typically register a callback for some event, and call that callback
651when the event occured. In a coroutine, however, you typically want to 785when the event occured. In a coro, however, you typically want to
652just wait for the event, simplyifying things. 786just wait for the event, simplyifying things.
653 787
654For example C<< AnyEvent->child >> registers a callback to be called when 788For example C<< AnyEvent->child >> registers a callback to be called when
655a specific child has exited: 789a specific child has exited:
656 790
657 my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... }); 791 my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
658 792
659But from withina coroutine, you often just want to write this: 793But from within a coro, you often just want to write this:
660 794
661 my $status = wait_for_child $pid; 795 my $status = wait_for_child $pid;
662 796
663Coro offers two functions specifically designed to make this easy, 797Coro offers two functions specifically designed to make this easy,
664C<Coro::rouse_cb> and C<Coro::rouse_wait>. 798C<Coro::rouse_cb> and C<Coro::rouse_wait>.
665 799
666The first function, C<rouse_cb>, generates and returns a callback that, 800The first function, C<rouse_cb>, generates and returns a callback that,
667when invoked, will save its arguments and notify the coroutine that 801when invoked, will save its arguments and notify the coro that
668created the callback. 802created the callback.
669 803
670The second function, C<rouse_wait>, waits for the callback to be called 804The second function, C<rouse_wait>, waits for the callback to be called
671(by calling C<schedule> to go to sleep) and returns the arguments 805(by calling C<schedule> to go to sleep) and returns the arguments
672originally passed to the callback. 806originally passed to the callback.
687you can roll your own, using C<schedule>: 821you can roll your own, using C<schedule>:
688 822
689 sub wait_for_child($) { 823 sub wait_for_child($) {
690 my ($pid) = @_; 824 my ($pid) = @_;
691 825
692 # store the current coroutine in $current, 826 # store the current coro in $current,
693 # and provide result variables for the closure passed to ->child 827 # and provide result variables for the closure passed to ->child
694 my $current = $Coro::current; 828 my $current = $Coro::current;
695 my ($done, $rstatus); 829 my ($done, $rstatus);
696 830
697 # pass a closure to ->child 831 # pass a closure to ->child
713 847
714=item fork with pthread backend 848=item fork with pthread backend
715 849
716When Coro is compiled using the pthread backend (which isn't recommended 850When Coro is compiled using the pthread backend (which isn't recommended
717but required on many BSDs as their libcs are completely broken), then 851but required on many BSDs as their libcs are completely broken), then
718coroutines will not survive a fork. There is no known workaround except to 852coro will not survive a fork. There is no known workaround except to
719fix your libc and use a saner backend. 853fix your libc and use a saner backend.
720 854
721=item perl process emulation ("threads") 855=item perl process emulation ("threads")
722 856
723This module is not perl-pseudo-thread-safe. You should only ever use this 857This module is not perl-pseudo-thread-safe. You should only ever use this
725future to allow per-thread schedulers, but Coro::State does not yet allow 859future to allow per-thread schedulers, but Coro::State does not yet allow
726this). I recommend disabling thread support and using processes, as having 860this). I recommend disabling thread support and using processes, as having
727the windows process emulation enabled under unix roughly halves perl 861the windows process emulation enabled under unix roughly halves perl
728performance, even when not used. 862performance, even when not used.
729 863
730=item coroutine switching not signal safe 864=item coro switching is not signal safe
731 865
732You must not switch to another coroutine from within a signal handler 866You must not switch to another coro from within a signal handler (only
733(only relevant with %SIG - most event libraries provide safe signals). 867relevant with %SIG - most event libraries provide safe signals), I<unless>
868you are sure you are not interrupting a Coro function.
734 869
735That means you I<MUST NOT> call any function that might "block" the 870That means you I<MUST NOT> call any function that might "block" the
736current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or 871current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
737anything that calls those. Everything else, including calling C<ready>, 872anything that calls those. Everything else, including calling C<ready>,
738works. 873works.
739 874
740=back 875=back
741 876
877
878=head1 WINDOWS PROCESS EMULATION
879
880A great many people seem to be confused about ithreads (for example, Chip
881Salzenberg called me unintelligent, incapable, stupid and gullible,
882while in the same mail making rather confused statements about perl
883ithreads (for example, that memory or files would be shared), showing his
884lack of understanding of this area - if it is hard to understand for Chip,
885it is probably not obvious to everybody).
886
887What follows is an ultra-condensed version of my talk about threads in
888scripting languages given on the perl workshop 2009:
889
890The so-called "ithreads" were originally implemented for two reasons:
891first, to (badly) emulate unix processes on native win32 perls, and
892secondly, to replace the older, real thread model ("5.005-threads").
893
894It does that by using threads instead of OS processes. The difference
895between processes and threads is that threads share memory (and other
896state, such as files) between threads within a single process, while
897processes do not share anything (at least not semantically). That
898means that modifications done by one thread are seen by others, while
899modifications by one process are not seen by other processes.
900
901The "ithreads" work exactly like that: when creating a new ithreads
902process, all state is copied (memory is copied physically, files and code
903is copied logically). Afterwards, it isolates all modifications. On UNIX,
904the same behaviour can be achieved by using operating system processes,
905except that UNIX typically uses hardware built into the system to do this
906efficiently, while the windows process emulation emulates this hardware in
907software (rather efficiently, but of course it is still much slower than
908dedicated hardware).
909
910As mentioned before, loading code, modifying code, modifying data
911structures and so on is only visible in the ithreads process doing the
912modification, not in other ithread processes within the same OS process.
913
914This is why "ithreads" do not implement threads for perl at all, only
915processes. What makes it so bad is that on non-windows platforms, you can
916actually take advantage of custom hardware for this purpose (as evidenced
917by the forks module, which gives you the (i-) threads API, just much
918faster).
919
920Sharing data is in the i-threads model is done by transfering data
921structures between threads using copying semantics, which is very slow -
922shared data simply does not exist. Benchmarks using i-threads which are
923communication-intensive show extremely bad behaviour with i-threads (in
924fact, so bad that Coro, which cannot take direct advantage of multiple
925CPUs, is often orders of magnitude faster because it shares data using
926real threads, refer to my talk for details).
927
928As summary, i-threads *use* threads to implement processes, while
929the compatible forks module *uses* processes to emulate, uhm,
930processes. I-threads slow down every perl program when enabled, and
931outside of windows, serve no (or little) practical purpose, but
932disadvantages every single-threaded Perl program.
933
934This is the reason that I try to avoid the name "ithreads", as it is
935misleading as it implies that it implements some kind of thread model for
936perl, and prefer the name "windows process emulation", which describes the
937actual use and behaviour of it much better.
742 938
743=head1 SEE ALSO 939=head1 SEE ALSO
744 940
745Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. 941Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
746 942

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