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1=head1 NAME 1=head1 NAME
2 2
3Coro - coroutine process abstraction 3Coro - the only real threads in perl
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use Coro; 7 use Coro;
8 8
9 async { 9 async {
10 # some asynchronous thread of execution 10 # some asynchronous thread of execution
11 print "2\n"; 11 print "2\n";
12 cede; # yield back to main 12 cede; # yield back to main
13 print "4\n"; 13 print "4\n";
14 }; 14 };
15 print "1\n"; 15 print "1\n";
16 cede; # yield to coroutine 16 cede; # yield to coro
17 print "3\n"; 17 print "3\n";
18 cede; # and again 18 cede; # and again
19 19
20 # use locking 20 # use locking
21 use Coro::Semaphore;
21 my $lock = new Coro::Semaphore; 22 my $lock = new Coro::Semaphore;
22 my $locked; 23 my $locked;
23 24
24 $lock->down; 25 $lock->down;
25 $locked = 1; 26 $locked = 1;
26 $lock->up; 27 $lock->up;
27 28
28=head1 DESCRIPTION 29=head1 DESCRIPTION
29 30
30This module collection manages coroutines. Coroutines are similar 31For a tutorial-style introduction, please read the L<Coro::Intro>
31to threads but don't run in parallel at the same time even on SMP 32manpage. This manpage mainly contains reference information.
32machines. The specific flavor of coroutine used in this module also
33guarantees you that it will not switch between coroutines unless
34necessary, at easily-identified points in your program, so locking and
35parallel access are rarely an issue, making coroutine programming much
36safer than threads programming.
37 33
38(Perl, however, does not natively support real threads but instead does a 34This module collection manages continuations in general, most often in
39very slow and memory-intensive emulation of processes using threads. This 35the form of cooperative threads (also called coros, or simply "coro"
40is a performance win on Windows machines, and a loss everywhere else). 36in the documentation). They are similar to kernel threads but don't (in
37general) run in parallel at the same time even on SMP machines. The
38specific flavor of thread offered by this module also guarantees you that
39it will not switch between threads unless necessary, at easily-identified
40points in your program, so locking and parallel access are rarely an
41issue, making thread programming much safer and easier than using other
42thread models.
41 43
44Unlike the so-called "Perl threads" (which are not actually real threads
45but only the windows process emulation (see section of same name for more
46details) ported to unix, and as such act as processes), Coro provides
47a full shared address space, which makes communication between threads
48very easy. And Coro's threads are fast, too: disabling the Windows
49process emulation code in your perl and using Coro can easily result in
50a two to four times speed increase for your programs. A parallel matrix
51multiplication benchmark runs over 300 times faster on a single core than
52perl's pseudo-threads on a quad core using all four cores.
53
54Coro achieves that by supporting multiple running interpreters that share
55data, which is especially useful to code pseudo-parallel processes and
56for event-based programming, such as multiple HTTP-GET requests running
57concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
58into an event-based environment.
59
42In this module, coroutines are defined as "callchain + lexical variables + 60In this module, a thread is defined as "callchain + lexical variables +
43@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain, 61some package variables + C stack), that is, a thread has its own callchain,
44its own set of lexicals and its own set of perls most important global 62its own set of lexicals and its own set of perls most important global
45variables (see L<Coro::State> for more configuration). 63variables (see L<Coro::State> for more configuration and background info).
64
65See also the C<SEE ALSO> section at the end of this document - the Coro
66module family is quite large.
46 67
47=cut 68=cut
48 69
49package Coro; 70package Coro;
50 71
51use strict; 72use common::sense;
52no warnings "uninitialized"; 73
74use Carp ();
75
76use Guard ();
53 77
54use Coro::State; 78use Coro::State;
55 79
56use base qw(Coro::State Exporter); 80use base qw(Coro::State Exporter);
57 81
58our $idle; # idle handler 82our $idle; # idle handler
59our $main; # main coroutine 83our $main; # main coro
60our $current; # current coroutine 84our $current; # current coro
61 85
62our $VERSION = '4.2'; 86our $VERSION = 5.21;
63 87
64our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); 88our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
65our %EXPORT_TAGS = ( 89our %EXPORT_TAGS = (
66 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 90 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
67); 91);
68our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); 92our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
69 93
70{ 94=head1 GLOBAL VARIABLES
71 my @async;
72 my $init;
73
74 # this way of handling attributes simply is NOT scalable ;()
75 sub import {
76 no strict 'refs';
77
78 Coro->export_to_level (1, @_);
79
80 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
81 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
82 my ($package, $ref) = (shift, shift);
83 my @attrs;
84 for (@_) {
85 if ($_ eq "Coro") {
86 push @async, $ref;
87 unless ($init++) {
88 eval q{
89 sub INIT {
90 &async(pop @async) while @async;
91 }
92 };
93 }
94 } else {
95 push @attrs, $_;
96 }
97 }
98 return $old ? $old->($package, $ref, @attrs) : @attrs;
99 };
100 }
101
102}
103 95
104=over 4 96=over 4
105 97
106=item $main 98=item $Coro::main
107 99
108This coroutine represents the main program. 100This variable stores the Coro object that represents the main
101program. While you cna C<ready> it and do most other things you can do to
102coro, it is mainly useful to compare again C<$Coro::current>, to see
103whether you are running in the main program or not.
109 104
110=cut 105=cut
111 106
112$main = new Coro; 107# $main is now being initialised by Coro::State
113 108
114=item $current (or as function: current) 109=item $Coro::current
115 110
116The current coroutine (the last coroutine switched to). The initial value 111The Coro object representing the current coro (the last
112coro that the Coro scheduler switched to). The initial value is
117is C<$main> (of course). 113C<$Coro::main> (of course).
118 114
119This variable is B<strictly> I<read-only>. It is provided for performance 115This variable is B<strictly> I<read-only>. You can take copies of the
120reasons. If performance is not essential you are encouraged to use the 116value stored in it and use it as any other Coro object, but you must
121C<Coro::current> function instead. 117not otherwise modify the variable itself.
122 118
123=cut 119=cut
124 120
125$main->{desc} = "[main::]";
126
127# maybe some other module used Coro::Specific before...
128$main->{_specific} = $current->{_specific}
129 if $current;
130
131_set_current $main;
132
133sub current() { $current } 121sub current() { $current } # [DEPRECATED]
134 122
135=item $idle 123=item $Coro::idle
136 124
137A callback that is called whenever the scheduler finds no ready coroutines 125This variable is mainly useful to integrate Coro into event loops. It is
126usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
127pretty low-level functionality.
128
129This variable stores a Coro object that is put into the ready queue when
130there are no other ready threads (without invoking any ready hooks).
131
138to run. The default implementation prints "FATAL: deadlock detected" and 132The default implementation dies with "FATAL: deadlock detected.", followed
139exits, because the program has no other way to continue. 133by a thread listing, because the program has no other way to continue.
140 134
141This hook is overwritten by modules such as C<Coro::Timer> and 135This hook is overwritten by modules such as C<Coro::EV> and
142C<Coro::Event> to wait on an external event that hopefully wake up a 136C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
143coroutine so the scheduler can run it. 137coro so the scheduler can run it.
144 138
145Please note that if your callback recursively invokes perl (e.g. for event 139See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
146handlers), then it must be prepared to be called recursively itself.
147 140
148=cut 141=cut
149 142
150$idle = sub { 143$idle = new Coro sub {
151 require Carp; 144 require Coro::Debug;
152 Carp::croak ("FATAL: deadlock detected"); 145 die "FATAL: deadlock detected.\n"
146 . Coro::Debug::ps_listing ();
153}; 147};
154 148
155sub _cancel {
156 my ($self) = @_;
157
158 # free coroutine data and mark as destructed
159 $self->_destroy
160 or return;
161
162 # call all destruction callbacks
163 $_->(@{$self->{_status}})
164 for @{(delete $self->{_on_destroy}) || []};
165}
166
167# this coroutine is necessary because a coroutine 149# this coro is necessary because a coro
168# cannot destroy itself. 150# cannot destroy itself.
169my @destroy; 151our @destroy;
170my $manager; 152our $manager;
171 153
172$manager = new Coro sub { 154$manager = new Coro sub {
173 while () { 155 while () {
174 (shift @destroy)->_cancel 156 Coro::State::cancel shift @destroy
175 while @destroy; 157 while @destroy;
176 158
177 &schedule; 159 &schedule;
178 } 160 }
179}; 161};
180$manager->desc ("[coro manager]"); 162$manager->{desc} = "[coro manager]";
181$manager->prio (PRIO_MAX); 163$manager->prio (PRIO_MAX);
182 164
183# static methods. not really.
184
185=back 165=back
186 166
187=head2 STATIC METHODS 167=head1 SIMPLE CORO CREATION
188
189Static methods are actually functions that operate on the current coroutine only.
190 168
191=over 4 169=over 4
192 170
193=item async { ... } [@args...] 171=item async { ... } [@args...]
194 172
195Create a new asynchronous coroutine and return it's coroutine object 173Create a new coro and return its Coro object (usually
196(usually unused). When the sub returns the new coroutine is automatically 174unused). The coro will be put into the ready queue, so
175it will start running automatically on the next scheduler run.
176
177The first argument is a codeblock/closure that should be executed in the
178coro. When it returns argument returns the coro is automatically
197terminated. 179terminated.
198 180
181The remaining arguments are passed as arguments to the closure.
182
199See the C<Coro::State::new> constructor for info about the coroutine 183See the C<Coro::State::new> constructor for info about the coro
200environment in which coroutines run. 184environment in which coro are executed.
201 185
202Calling 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
203the coroutine. Likewise, when the coroutine dies, the program will exit, 187the coro. Likewise, when the coro dies, the program will exit,
204just as it would in the main program. 188just as it would in the main program.
205 189
190If you do not want that, you can provide a default C<die> handler, or
191simply avoid dieing (by use of C<eval>).
192
206 # create a new coroutine that just prints its arguments 193Example: Create a new coro that just prints its arguments.
194
207 async { 195 async {
208 print "@_\n"; 196 print "@_\n";
209 } 1,2,3,4; 197 } 1,2,3,4;
210 198
211=cut
212
213sub async(&@) {
214 my $coro = new Coro @_;
215 $coro->ready;
216 $coro
217}
218
219=item async_pool { ... } [@args...] 199=item async_pool { ... } [@args...]
220 200
221Similar 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
222terminate or join (although you are allowed to), and you get a coroutine 202terminate or join on it (although you are allowed to), and you get a
223that might have executed other code already (which can be good or bad :). 203coro that might have executed other code already (which can be good
204or bad :).
224 205
206On the plus side, this function is about twice as fast as creating (and
207destroying) a completely new coro, so if you need a lot of generic
208coros in quick successsion, use C<async_pool>, not C<async>.
209
225Also, the 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
226issued in case of an exception instead of terminating the program, as 211issued in case of an exception instead of terminating the program, as
227C<async> does. As the coroutine is being reused, stuff like C<on_destroy> 212C<async> does. As the coro is being reused, stuff like C<on_destroy>
228will not work in the expected way, unless you call terminate or cancel, 213will not work in the expected way, unless you call terminate or cancel,
229which somehow defeats the purpose of pooling. 214which somehow defeats the purpose of pooling (but is fine in the
215exceptional case).
230 216
231The priority will be reset to C<0> after each job, tracing will be 217The priority will be reset to C<0> after each run, tracing will be
232disabled, the description will be reset and the default output filehandle 218disabled, the description will be reset and the default output filehandle
233gets restored, so you can change alkl these. Otherwise the coroutine will 219gets restored, so you can change all these. Otherwise the coro will
234be re-used "as-is": most notably if you change other per-coroutine global 220be re-used "as-is": most notably if you change other per-coro global
235stuff such as C<$/> you need to revert that change, which is most simply 221stuff such as C<$/> you I<must needs> revert that change, which is most
236done by using local as in C< local $/ >. 222simply done by using local as in: C<< local $/ >>.
237 223
238The pool size is limited to 8 idle coroutines (this can be adjusted by 224The idle pool size is limited to C<8> idle coros (this can be
239changing $Coro::POOL_SIZE), and there can be as many non-idle coros as 225adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
240required. 226coros as required.
241 227
242If you are concerned about pooled coroutines growing a lot because a 228If you are concerned about pooled coros growing a lot because a
243single C<async_pool> used a lot of stackspace you can e.g. C<async_pool 229single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
244{ terminate }> once per second or so to slowly replenish the pool. In 230{ terminate }> once per second or so to slowly replenish the pool. In
245addition to that, when the stacks used by a handler grows larger than 16kb 231addition to that, when the stacks used by a handler grows larger than 32kb
246(adjustable with $Coro::POOL_RSS) it will also exit. 232(adjustable via $Coro::POOL_RSS) it will also be destroyed.
247 233
248=cut 234=cut
249 235
250our $POOL_SIZE = 8; 236our $POOL_SIZE = 8;
251our $POOL_RSS = 16 * 1024; 237our $POOL_RSS = 32 * 1024;
252our @async_pool; 238our @async_pool;
253 239
254sub pool_handler { 240sub pool_handler {
255 my $cb;
256
257 while () { 241 while () {
258 eval { 242 eval {
259 while () { 243 &{&_pool_handler} while 1;
260 _pool_1 $cb;
261 &$cb;
262 _pool_2 $cb;
263 &schedule;
264 }
265 }; 244 };
266 245
267 last if $@ eq "\3async_pool terminate\2\n";
268 warn $@ if $@; 246 warn $@ if $@;
269 } 247 }
270} 248}
271 249
272sub async_pool(&@) { 250=back
273 # this is also inlined into the unlock_scheduler
274 my $coro = (pop @async_pool) || new Coro \&pool_handler;
275 251
276 $coro->{_invoke} = [@_]; 252=head1 STATIC METHODS
277 $coro->ready;
278 253
279 $coro 254Static methods are actually functions that implicitly operate on the
280} 255current coro.
256
257=over 4
281 258
282=item schedule 259=item schedule
283 260
284Calls the scheduler. Please note that the current coroutine will not be put 261Calls the scheduler. The scheduler will find the next coro that is
262to be run from the ready queue and switches to it. The next coro
263to be run is simply the one with the highest priority that is longest
264in its ready queue. If there is no coro ready, it will call the
265C<$Coro::idle> hook.
266
267Please note that the current coro will I<not> be put into the ready
285into the ready queue, so calling this function usually means you will 268queue, so calling this function usually means you will never be called
286never be called again unless something else (e.g. an event handler) calls 269again unless something else (e.g. an event handler) calls C<< ->ready >>,
287ready. 270thus waking you up.
288 271
289The canonical way to wait on external events is this: 272This makes C<schedule> I<the> generic method to use to block the current
273coro and wait for events: first you remember the current coro in
274a variable, then arrange for some callback of yours to call C<< ->ready
275>> on that once some event happens, and last you call C<schedule> to put
276yourself to sleep. Note that a lot of things can wake your coro up,
277so you need to check whether the event indeed happened, e.g. by storing the
278status in a variable.
290 279
291 { 280See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
292 # remember current coroutine
293 my $current = $Coro::current;
294 281
295 # register a hypothetical event handler 282=item cede
296 on_event_invoke sub { 283
297 # wake up sleeping coroutine 284"Cede" to other coros. This function puts the current coro into
298 $current->ready; 285the ready queue and calls C<schedule>, which has the effect of giving
299 undef $current; 286up the current "timeslice" to other coros of the same or higher
287priority. Once your coro gets its turn again it will automatically be
288resumed.
289
290This function is often called C<yield> in other languages.
291
292=item Coro::cede_notself
293
294Works like cede, but is not exported by default and will cede to I<any>
295coro, regardless of priority. This is useful sometimes to ensure
296progress is made.
297
298=item terminate [arg...]
299
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
300 }; 343 };
301 344
302 # call schedule until event occurred. 345 Coro::on_leave {
303 # in case we are woken up for other reasons 346 $ENV{TZ} = $old_tz;
304 # (current still defined), loop. 347 tzset; # restore old value
305 Coro::schedule while $current; 348 };
349
350 # at this place, the timezone is Antarctica/South_Pole,
351 # without disturbing the TZ of any other coro.
306 } 352 };
307 353
308=item cede 354This can be used to localise about any resource (locale, uid, current
355working directory etc.) to a block, despite the existance of other
356coros.
309 357
310"Cede" to other coroutines. This function puts the current coroutine into the 358Another interesting example implements time-sliced multitasking using
311ready queue and calls C<schedule>, which has the effect of giving up the 359interval timers (this could obviously be optimised, but does the job):
312current "timeslice" to other coroutines of the same or higher priority.
313 360
314=item Coro::cede_notself 361 # "timeslice" the given block
362 sub timeslice(&) {
363 use Time::HiRes ();
315 364
316Works like cede, but is not exported by default and will cede to any 365 Coro::on_enter {
317coroutine, regardless of priority, once. 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 };
318 375
319=item terminate [arg...] 376 &{+shift};
377 }
320 378
321Terminates the current coroutine with the given status values (see L<cancel>). 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
322 387
323=item killall 388=item killall
324 389
325Kills/terminates/cancels all coroutines except the currently running 390Kills/terminates/cancels all coros except the currently running one.
326one. This is useful after a fork, either in the child or the parent, as
327usually only one of them should inherit the running coroutines.
328 391
329=cut 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
394cannot free all of them, so if a coro that is not the main coro
395calls this function, there will be some one-time resource leak.
330 396
331sub terminate { 397=cut
332 $current->cancel (@_);
333}
334 398
335sub killall { 399sub killall {
336 for (Coro::State::list) { 400 for (Coro::State::list) {
337 $_->cancel 401 $_->cancel
338 if $_ != $current && UNIVERSAL::isa $_, "Coro"; 402 if $_ != $current && UNIVERSAL::isa $_, "Coro";
339 } 403 }
340} 404}
341 405
342=back 406=back
343 407
344# dynamic methods
345
346=head2 COROUTINE METHODS 408=head1 CORO OBJECT METHODS
347 409
348These are the methods you can call on coroutine objects. 410These are the methods you can call on coro objects (or to create
411them).
349 412
350=over 4 413=over 4
351 414
352=item new Coro \&sub [, @args...] 415=item new Coro \&sub [, @args...]
353 416
354Create 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
355automatically terminates as if C<terminate> with the returned values were 418automatically terminates as if C<terminate> with the returned values were
356called. To make the coroutine run you must first put it into the ready queue 419called. To make the coro run you must first put it into the ready
357by calling the ready method. 420queue by calling the ready method.
358 421
359See 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
360coroutine environment. 423coro environment.
361 424
362=cut 425=cut
363 426
364sub _run_coro { 427sub _coro_run {
365 terminate &{+shift}; 428 terminate &{+shift};
366} 429}
367 430
368sub new {
369 my $class = shift;
370
371 $class->SUPER::new (\&_run_coro, @_)
372}
373
374=item $success = $coroutine->ready 431=item $success = $coro->ready
375 432
376Put the given coroutine into the ready queue (according to it's priority) 433Put the given coro into the end of its ready queue (there is one
377and return true. If the coroutine is already in the ready queue, do nothing 434queue for each priority) and return true. If the coro is already in
378and return false. 435the ready queue, do nothing and return false.
379 436
437This ensures that the scheduler will resume this coro automatically
438once all the coro of higher priority and all coro of the same
439priority that were put into the ready queue earlier have been resumed.
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
380=item $is_ready = $coroutine->is_ready 466=item $is_ready = $coro->is_ready
381 467
382Return wether 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.
383 470
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
384=item $coroutine->cancel (arg...) 482=item $coro->cancel (arg...)
385 483
386Terminates the given coroutine and makes it return the given arguments as 484Terminates the given Coro and makes it return the given arguments as
387status (default: the empty list). Never returns if the coroutine is the 485status (default: the empty list). Never returns if the Coro is the
388current coroutine. 486current Coro.
389 487
390=cut 488=cut
391 489
392sub cancel { 490sub cancel {
393 my $self = shift; 491 my $self = shift;
394 $self->{_status} = [@_];
395 492
396 if ($current == $self) { 493 if ($current == $self) {
397 push @destroy, $self; 494 terminate @_;
398 $manager->ready;
399 &schedule while 1;
400 } else { 495 } else {
401 $self->_cancel; 496 $self->{_status} = [@_];
497 Coro::State::cancel $self;
402 } 498 }
403} 499}
404 500
501=item $coro->schedule_to
502
503Puts the current coro to sleep (like C<Coro::schedule>), but instead
504of continuing with the next coro from the ready queue, always switch to
505the given coro object (regardless of priority etc.). The readyness
506state of that coro isn't changed.
507
508This is an advanced method for special cases - I'd love to hear about any
509uses for this one.
510
511=item $coro->cede_to
512
513Like C<schedule_to>, but puts the current coro into the ready
514queue. This has the effect of temporarily switching to the given
515coro, and continuing some time later.
516
517This is an advanced method for special cases - I'd love to hear about any
518uses for this one.
519
520=item $coro->throw ([$scalar])
521
522If C<$throw> is specified and defined, it will be thrown as an exception
523inside the coro at the next convenient point in time. Otherwise
524clears the exception object.
525
526Coro will check for the exception each time a schedule-like-function
527returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
528>>, C<< Coro::Handle->readable >> and so on. Most of these functions
529detect this case and return early in case an exception is pending.
530
531The exception object will be thrown "as is" with the specified scalar in
532C<$@>, i.e. if it is a string, no line number or newline will be appended
533(unlike with C<die>).
534
535This can be used as a softer means than C<cancel> to ask a coro to
536end itself, although there is no guarantee that the exception will lead to
537termination, and if the exception isn't caught it might well end the whole
538program.
539
540You might also think of C<throw> as being the moral equivalent of
541C<kill>ing a coro with a signal (in this case, a scalar).
542
405=item $coroutine->join 543=item $coro->join
406 544
407Wait until the coroutine terminates and return any values given to the 545Wait until the coro terminates and return any values given to the
408C<terminate> or C<cancel> functions. C<join> can be called concurrently 546C<terminate> or C<cancel> functions. C<join> can be called concurrently
409from multiple coroutines. 547from multiple coro, and all will be resumed and given the status
548return once the C<$coro> terminates.
410 549
411=cut 550=cut
412 551
413sub join { 552sub join {
414 my $self = shift; 553 my $self = shift;
425 } 564 }
426 565
427 wantarray ? @{$self->{_status}} : $self->{_status}[0]; 566 wantarray ? @{$self->{_status}} : $self->{_status}[0];
428} 567}
429 568
430=item $coroutine->on_destroy (\&cb) 569=item $coro->on_destroy (\&cb)
431 570
432Registers a callback that is called when this coroutine gets destroyed, 571Registers a callback that is called when this coro gets destroyed,
433but before it is joined. The callback gets passed the terminate arguments, 572but before it is joined. The callback gets passed the terminate arguments,
434if any. 573if any, and I<must not> die, under any circumstances.
435 574
436=cut 575=cut
437 576
438sub on_destroy { 577sub on_destroy {
439 my ($self, $cb) = @_; 578 my ($self, $cb) = @_;
440 579
441 push @{ $self->{_on_destroy} }, $cb; 580 push @{ $self->{_on_destroy} }, $cb;
442} 581}
443 582
444=item $oldprio = $coroutine->prio ($newprio) 583=item $oldprio = $coro->prio ($newprio)
445 584
446Sets (or gets, if the argument is missing) the priority of the 585Sets (or gets, if the argument is missing) the priority of the
447coroutine. Higher priority coroutines get run before lower priority 586coro. Higher priority coro get run before lower priority
448coroutines. Priorities are small signed integers (currently -4 .. +3), 587coro. Priorities are small signed integers (currently -4 .. +3),
449that 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
450to get then): 589to get then):
451 590
452 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
453 3 > 1 > 0 > -1 > -3 > -4 592 3 > 1 > 0 > -1 > -3 > -4
454 593
455 # set priority to HIGH 594 # set priority to HIGH
456 current->prio(PRIO_HIGH); 595 current->prio (PRIO_HIGH);
457 596
458The idle coroutine ($Coro::idle) always has a lower priority than any 597The idle coro ($Coro::idle) always has a lower priority than any
459existing coroutine. 598existing coro.
460 599
461Changing the priority of the current coroutine will take effect immediately, 600Changing the priority of the current coro will take effect immediately,
462but changing the priority of coroutines in the ready queue (but not 601but changing the priority of coro in the ready queue (but not
463running) will only take effect after the next schedule (of that 602running) will only take effect after the next schedule (of that
464coroutine). 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.
465 604
466=item $newprio = $coroutine->nice ($change) 605=item $newprio = $coro->nice ($change)
467 606
468Similar 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.
469higher values mean lower priority, just as in unix). 608higher values mean lower priority, just as in unix).
470 609
471=item $olddesc = $coroutine->desc ($newdesc) 610=item $olddesc = $coro->desc ($newdesc)
472 611
473Sets (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
474coroutine. This is just a free-form string you can associate with a coroutine. 613coro. This is just a free-form string you can associate with a
614coro.
475 615
476This method simply sets the C<< $coroutine->{desc} >> member to the given string. You 616This method simply sets the C<< $coro->{desc} >> member to the given
477can modify this member directly if you wish. 617string. You can modify this member directly if you wish.
478
479=item $coroutine->throw ([$scalar])
480
481If C<$throw> is specified and defined, it will be thrown as an exception
482inside the coroutine at the next convinient point in time (usually after
483it gains control at the next schedule/transfer/cede). Otherwise clears the
484exception object.
485
486The exception object will be thrown "as is" with the specified scalar in
487C<$@>, i.e. if it is a string, no line number or newline will be appended
488(unlike with C<die>).
489
490This can be used as a softer means than C<cancel> to ask a coroutine to
491end itself, although there is no guarentee that the exception will lead to
492termination, and if the exception isn't caught it might well end the whole
493program.
494 618
495=cut 619=cut
496 620
497sub desc { 621sub desc {
498 my $old = $_[0]{desc}; 622 my $old = $_[0]{desc};
499 $_[0]{desc} = $_[1] if @_ > 1; 623 $_[0]{desc} = $_[1] if @_ > 1;
500 $old; 624 $old;
501} 625}
502 626
627sub transfer {
628 require Carp;
629 Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
630}
631
503=back 632=back
504 633
505=head2 GLOBAL FUNCTIONS 634=head1 GLOBAL FUNCTIONS
506 635
507=over 4 636=over 4
508 637
509=item Coro::nready 638=item Coro::nready
510 639
511Returns the number of coroutines that are currently in the ready state, 640Returns the number of coro that are currently in the ready state,
512i.e. that can be switched to. The value C<0> means that the only runnable 641i.e. that can be switched to by calling C<schedule> directory or
642indirectly. The value C<0> means that the only runnable coro is the
513coroutine is the currently running one, so C<cede> would have no effect, 643currently running one, so C<cede> would have no effect, and C<schedule>
514and C<schedule> would cause a deadlock unless there is an idle handler 644would cause a deadlock unless there is an idle handler that wakes up some
515that wakes up some coroutines. 645coro.
516 646
517=item my $guard = Coro::guard { ... } 647=item my $guard = Coro::guard { ... }
518 648
519This creates and returns a guard object. Nothing happens until the object 649This function still exists, but is deprecated. Please use the
520gets destroyed, in which case the codeblock given as argument will be 650C<Guard::guard> function instead.
521executed. This is useful to free locks or other resources in case of a
522runtime error or when the coroutine gets canceled, as in both cases the
523guard block will be executed. The guard object supports only one method,
524C<< ->cancel >>, which will keep the codeblock from being executed.
525 651
526Example: set some flag and clear it again when the coroutine gets canceled
527or the function returns:
528
529 sub do_something {
530 my $guard = Coro::guard { $busy = 0 };
531 $busy = 1;
532
533 # do something that requires $busy to be true
534 }
535
536=cut 652=cut
537 653
538sub guard(&) { 654BEGIN { *guard = \&Guard::guard }
539 bless \(my $cb = $_[0]), "Coro::guard"
540}
541
542sub Coro::guard::cancel {
543 ${$_[0]} = sub { };
544}
545
546sub Coro::guard::DESTROY {
547 ${$_[0]}->();
548}
549
550 655
551=item unblock_sub { ... } 656=item unblock_sub { ... }
552 657
553This utility function takes a BLOCK or code reference and "unblocks" it, 658This utility function takes a BLOCK or code reference and "unblocks" it,
554returning the new coderef. This means that the new coderef will return 659returning a new coderef. Unblocking means that calling the new coderef
555immediately without blocking, returning nothing, while the original code 660will return immediately without blocking, returning nothing, while the
556ref will be called (with parameters) from within its own coroutine. 661original code ref will be called (with parameters) from within another
662coro.
557 663
558The 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
559venerable L<Event|Event> module) are not coroutine-safe (a weaker form 665venerable L<Event|Event> module) are not thread-safe (a weaker form
560of thread-safety). This means you must not block within event callbacks, 666of reentrancy). This means you must not block within event callbacks,
561otherwise you might suffer from crashes or worse. 667otherwise you might suffer from crashes or worse. The only event library
668currently known that is safe to use without C<unblock_sub> is L<EV>.
562 669
563This function allows your callbacks to block by executing them in another 670This function allows your callbacks to block by executing them in another
564coroutine 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
565is 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
566disk. 673disk, for example.
567 674
568In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when 675In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
569creating event callbacks that want to block. 676creating event callbacks that want to block.
677
678If your handler does not plan to block (e.g. simply sends a message to
679another coro, or puts some other coro into the ready queue), there is
680no reason to use C<unblock_sub>.
681
682Note that you also need to use C<unblock_sub> for any other callbacks that
683are indirectly executed by any C-based event loop. For example, when you
684use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
685provides callbacks that are the result of some event callback, then you
686must not block either, or use C<unblock_sub>.
570 687
571=cut 688=cut
572 689
573our @unblock_queue; 690our @unblock_queue;
574 691
577# return immediately and can be reused) and because we cannot cede 694# return immediately and can be reused) and because we cannot cede
578# inside an event callback. 695# inside an event callback.
579our $unblock_scheduler = new Coro sub { 696our $unblock_scheduler = new Coro sub {
580 while () { 697 while () {
581 while (my $cb = pop @unblock_queue) { 698 while (my $cb = pop @unblock_queue) {
582 # this is an inlined copy of async_pool 699 &async_pool (@$cb);
583 my $coro = (pop @async_pool) || new Coro \&pool_handler;
584 700
585 $coro->{_invoke} = $cb;
586 $coro->ready;
587 cede; # for short-lived callbacks, this reduces pressure on the coro pool 701 # for short-lived callbacks, this reduces pressure on the coro pool
702 # as the chance is very high that the async_poll coro will be back
703 # in the idle state when cede returns
704 cede;
588 } 705 }
589 schedule; # sleep well 706 schedule; # sleep well
590 } 707 }
591}; 708};
592$unblock_scheduler->desc ("[unblock_sub scheduler]"); 709$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
593 710
594sub unblock_sub(&) { 711sub unblock_sub(&) {
595 my $cb = shift; 712 my $cb = shift;
596 713
597 sub { 714 sub {
598 unshift @unblock_queue, [$cb, @_]; 715 unshift @unblock_queue, [$cb, @_];
599 $unblock_scheduler->ready; 716 $unblock_scheduler->ready;
600 } 717 }
601} 718}
602 719
720=item $cb = rouse_cb
721
722Create and return a "rouse callback". That's a code reference that,
723when called, will remember a copy of its arguments and notify the owner
724coro of the callback.
725
726See the next function.
727
728=item @args = rouse_wait [$cb]
729
730Wait for the specified rouse callback (or the last one that was created in
731this coro).
732
733As soon as the callback is invoked (or when the callback was invoked
734before C<rouse_wait>), it will return the arguments originally passed to
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.
738
739See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
740
603=back 741=back
604 742
605=cut 743=cut
606 744
6071; 7451;
608 746
747=head1 HOW TO WAIT FOR A CALLBACK
748
749It is very common for a coro to wait for some callback to be
750called. This occurs naturally when you use coro in an otherwise
751event-based program, or when you use event-based libraries.
752
753These typically register a callback for some event, and call that callback
754when the event occured. In a coro, however, you typically want to
755just wait for the event, simplyifying things.
756
757For example C<< AnyEvent->child >> registers a callback to be called when
758a specific child has exited:
759
760 my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
761
762But from within a coro, you often just want to write this:
763
764 my $status = wait_for_child $pid;
765
766Coro offers two functions specifically designed to make this easy,
767C<Coro::rouse_cb> and C<Coro::rouse_wait>.
768
769The first function, C<rouse_cb>, generates and returns a callback that,
770when invoked, will save its arguments and notify the coro that
771created the callback.
772
773The second function, C<rouse_wait>, waits for the callback to be called
774(by calling C<schedule> to go to sleep) and returns the arguments
775originally passed to the callback.
776
777Using these functions, it becomes easy to write the C<wait_for_child>
778function mentioned above:
779
780 sub wait_for_child($) {
781 my ($pid) = @_;
782
783 my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
784
785 my ($rpid, $rstatus) = Coro::rouse_wait;
786 $rstatus
787 }
788
789In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
790you can roll your own, using C<schedule>:
791
792 sub wait_for_child($) {
793 my ($pid) = @_;
794
795 # store the current coro in $current,
796 # and provide result variables for the closure passed to ->child
797 my $current = $Coro::current;
798 my ($done, $rstatus);
799
800 # pass a closure to ->child
801 my $watcher = AnyEvent->child (pid => $pid, cb => sub {
802 $rstatus = $_[1]; # remember rstatus
803 $done = 1; # mark $rstatus as valud
804 });
805
806 # wait until the closure has been called
807 schedule while !$done;
808
809 $rstatus
810 }
811
812
609=head1 BUGS/LIMITATIONS 813=head1 BUGS/LIMITATIONS
610 814
611 - you must make very sure that no coro is still active on global 815=over 4
612 destruction. very bad things might happen otherwise (usually segfaults).
613 816
817=item fork with pthread backend
818
819When Coro is compiled using the pthread backend (which isn't recommended
820but required on many BSDs as their libcs are completely broken), then
821coro will not survive a fork. There is no known workaround except to
822fix your libc and use a saner backend.
823
824=item perl process emulation ("threads")
825
614 - this module is not thread-safe. You should only ever use this module 826This module is not perl-pseudo-thread-safe. You should only ever use this
615 from the same thread (this requirement might be loosened in the future 827module from the first thread (this requirement might be removed in the
616 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
617 this). 829this). I recommend disabling thread support and using processes, as having
830the windows process emulation enabled under unix roughly halves perl
831performance, even when not used.
832
833=item coro switching is not signal safe
834
835You must not switch to another coro from within a signal handler (only
836relevant with %SIG - most event libraries provide safe signals), I<unless>
837you are sure you are not interrupting a Coro function.
838
839That means you I<MUST NOT> call any function that might "block" the
840current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
841anything that calls those. Everything else, including calling C<ready>,
842works.
843
844=back
845
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.
618 907
619=head1 SEE ALSO 908=head1 SEE ALSO
620 909
621Lower level Configuration, Coroutine Environment: L<Coro::State>. 910Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
622 911
623Debugging: L<Coro::Debug>. 912Debugging: L<Coro::Debug>.
624 913
625Support/Utility: L<Coro::Specific>, L<Coro::Util>. 914Support/Utility: L<Coro::Specific>, L<Coro::Util>.
626 915
627Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. 916Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
917L<Coro::SemaphoreSet>, L<Coro::RWLock>.
628 918
629Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>. 919I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
630 920
631Compatibility: L<Coro::LWP>, L<Coro::Storable>, L<Coro::Select>. 921Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
922a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
923L<Coro::Select>.
632 924
633Embedding: L<Coro:MakeMaker>. 925XS API: L<Coro::MakeMaker>.
926
927Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
634 928
635=head1 AUTHOR 929=head1 AUTHOR
636 930
637 Marc Lehmann <schmorp@schmorp.de> 931 Marc Lehmann <schmorp@schmorp.de>
638 http://home.schmorp.de/ 932 http://home.schmorp.de/

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