[ViewVC] Diff of: cvs/cvsroot/Coro/Coro.pm

Comparing cvsroot/Coro/Coro.pm (file contents):
Revision 1.103 by root, Thu Jan 4 20:14:19 2007 UTC vs.
Revision 1.220 by root, Sun Nov 16 11:12:57 2008 UTC

…		…
2		2
3	Coro - coroutine process abstraction	3	Coro - coroutine process abstraction
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";
		12	cede; # yield back to main
		13	print "4\n";
11	};	14	};
12		15	print "1\n";
13	# alternatively create an async coroutine like this:	16	cede; # yield to coroutine
14		17	print "3\n";
15	sub some_func : Coro {	18	cede; # and again
16	# some more async code	19
17	}	20	# use locking
18		21	use Coro::Semaphore;
19	cede;	22	my $lock = new Coro::Semaphore;
		23	my $locked;
		24
		25	$lock->down;
		26	$locked = 1;
		27	$lock->up;
20		28
21	=head1 DESCRIPTION	29	=head1 DESCRIPTION
22		30
23	This module collection manages coroutines. Coroutines are similar	31	This module collection manages coroutines. Coroutines are similar to
24	to threads but don't run in parallel at the same time even on SMP	32	threads but don't (in general) run in parallel at the same time even
25	machines. The specific flavor of coroutine use din this module also	33	on SMP machines. The specific flavor of coroutine used in this module
26	guarentees you that it will not switch between coroutines unless	34	also guarantees you that it will not switch between coroutines unless
27	necessary, at easily-identified points in your program, so locking and	35	necessary, at easily-identified points in your program, so locking and
28	parallel access are rarely an issue, making coroutine programming much	36	parallel access are rarely an issue, making coroutine programming much
29	safer than threads programming.	37	safer and easier than threads programming.
30		38
31	(Perl, however, does not natively support real threads but instead does a	39	Unlike a normal perl program, however, coroutines allow you to have
32	very slow and memory-intensive emulation of processes using threads. This	40	multiple running interpreters that share data, which is especially useful
33	is a performance win on Windows machines, and a loss everywhere else).	41	to code pseudo-parallel processes and for event-based programming, such as
		42	multiple HTTP-GET requests running concurrently. See L<Coro::AnyEvent> to
		43	learn more.
		44
		45	Coroutines are also useful because Perl has no support for threads (the so
		46	called "threads" that perl offers are nothing more than the (bad) process
		47	emulation coming from the Windows platform: On standard operating systems
		48	they serve no purpose whatsoever, except by making your programs slow and
		49	making them use a lot of memory. Best disable them when building perl, or
		50	aks your software vendor/distributor to do it for you).
34		51
35	In this module, coroutines are defined as "callchain + lexical variables +	52	In this module, coroutines are defined as "callchain + lexical variables +
36	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,	53	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
37	its own set of lexicals and its own set of perls most important global	54	its own set of lexicals and its own set of perls most important global
38	variables.	55	variables (see L<Coro::State> for more configuration).
39		56
40	=cut	57	=cut
41		58
42	package Coro;	59	package Coro;
43		60
44	use strict;	61	use strict qw(vars subs);
45	no warnings "uninitialized";	62	no warnings "uninitialized";
46		63
47	use Coro::State;	64	use Coro::State;
48		65
49	use base qw(Coro::State Exporter);	66	use base qw(Coro::State Exporter);
50		67
51	our $idle; # idle handler	68	our $idle; # idle handler
52	our $main; # main coroutine	69	our $main; # main coroutine
53	our $current; # current coroutine	70	our $current; # current coroutine
54		71
55	our $VERSION = '3.3';	72	our $VERSION = 5.0;
56		73
57	our @EXPORT = qw(async cede schedule terminate current unblock_sub);	74	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
58	our %EXPORT_TAGS = (	75	our %EXPORT_TAGS = (
59	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	76	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
60	);	77	);
61	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	78	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
62		79
63	{
64	my @async;
65	my $init;
66
67	# this way of handling attributes simply is NOT scalable ;()
68	sub import {
69	no strict 'refs';
70
71	Coro->export_to_level (1, @_);
72
73	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
74	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
75	my ($package, $ref) = (shift, shift);
76	my @attrs;
77	for (@_) {
78	if ($_ eq "Coro") {
79	push @async, $ref;
80	unless ($init++) {
81	eval q{
82	sub INIT {
83	&async(pop @async) while @async;
84	}
85	};
86	}
87	} else {
88	push @attrs, $_;
89	}
90	}
91	return $old ? $old->($package, $ref, @attrs) : @attrs;
92	};
93	}
94
95	}
96
97	=over 4	80	=over 4
98		81
99	=item $main	82	=item $Coro::main
100		83
101	This coroutine represents the main program.	84	This variable stores the coroutine object that represents the main
		85	program. While you cna C<ready> it and do most other things you can do to
		86	coroutines, it is mainly useful to compare again C<$Coro::current>, to see
		87	whether you are running in the main program or not.
102		88
103	=cut	89	=cut
104		90
105	$main = new Coro;	91	# $main is now being initialised by Coro::State
106		92
107	=item $current (or as function: current)	93	=item $Coro::current
108		94
109	The current coroutine (the last coroutine switched to). The initial value	95	The coroutine object representing the current coroutine (the last
		96	coroutine that the Coro scheduler switched to). The initial value is
110	is C<$main> (of course).	97	C<$Coro::main> (of course).
111		98
112	This variable is B<strictly> I<read-only>. It is provided for performance	99	This variable is B<strictly> I<read-only>. You can take copies of the
113	reasons. If performance is not essentiel you are encouraged to use the	100	value stored in it and use it as any other coroutine object, but you must
114	C<Coro::current> function instead.	101	not otherwise modify the variable itself.
115		102
116	=cut	103	=cut
117		104
118	# maybe some other module used Coro::Specific before...
119	$main->{specific} = $current->{specific}
120	if $current;
121
122	_set_current $main;
123
124	sub current() { $current }	105	sub current() { $current } # [DEPRECATED]
125		106
126	=item $idle	107	=item $Coro::idle
127		108
128	A callback that is called whenever the scheduler finds no ready coroutines	109	This variable is mainly useful to integrate Coro into event loops. It is
129	to run. The default implementation prints "FATAL: deadlock detected" and	110	usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is
130	exits, because the program has no other way to continue.	111	pretty low-level functionality.
		112
		113	This variable stores a callback that is called whenever the scheduler
		114	finds no ready coroutines to run. The default implementation prints
		115	"FATAL: deadlock detected" and exits, because the program has no other way
		116	to continue.
131		117
132	This hook is overwritten by modules such as C<Coro::Timer> and	118	This hook is overwritten by modules such as C<Coro::Timer> and
133	C<Coro::Event> to wait on an external event that hopefully wake up a	119	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
134	coroutine so the scheduler can run it.	120	coroutine so the scheduler can run it.
135		121
		122	Note that the callback I<must not>, under any circumstances, block
		123	the current coroutine. Normally, this is achieved by having an "idle
		124	coroutine" that calls the event loop and then blocks again, and then
		125	readying that coroutine in the idle handler.
		126
		127	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
		128	technique.
		129
136	Please note that if your callback recursively invokes perl (e.g. for event	130	Please note that if your callback recursively invokes perl (e.g. for event
137	handlers), then it must be prepared to be called recursively.	131	handlers), then it must be prepared to be called recursively itself.
138		132
139	=cut	133	=cut
140		134
141	$idle = sub {	135	$idle = sub {
142	require Carp;	136	require Carp;
…		…
149	# free coroutine data and mark as destructed	143	# free coroutine data and mark as destructed
150	$self->_destroy	144	$self->_destroy
151	or return;	145	or return;
152		146
153	# call all destruction callbacks	147	# call all destruction callbacks
154	$_->(@{$self->{status}})	148	$_->(@{$self->{_status}})
155	for @{(delete $self->{destroy_cb}) \|\| []};	149	for @{ delete $self->{_on_destroy} \|\| [] };
156	}	150	}
157		151
158	# this coroutine is necessary because a coroutine	152	# this coroutine is necessary because a coroutine
159	# cannot destroy itself.	153	# cannot destroy itself.
160	my @destroy;	154	my @destroy;
…		…
166	while @destroy;	160	while @destroy;
167		161
168	&schedule;	162	&schedule;
169	}	163	}
170	};	164	};
171		165	$manager->{desc} = "[coro manager]";
172	$manager->prio (PRIO_MAX);	166	$manager->prio (PRIO_MAX);
173		167
174	# static methods. not really.
175
176	=back	168	=back
177		169
178	=head2 STATIC METHODS	170	=head2 SIMPLE COROUTINE CREATION
179
180	Static methods are actually functions that operate on the current coroutine only.
181		171
182	=over 4	172	=over 4
183		173
184	=item async { ... } [@args...]	174	=item async { ... } [@args...]
185		175
186	Create a new asynchronous coroutine and return it's coroutine object	176	Create a new coroutine and return it's coroutine object (usually
187	(usually unused). When the sub returns the new coroutine is automatically	177	unused). The coroutine will be put into the ready queue, so
		178	it will start running automatically on the next scheduler run.
		179
		180	The first argument is a codeblock/closure that should be executed in the
		181	coroutine. When it returns argument returns the coroutine is automatically
188	terminated.	182	terminated.
189		183
190	Calling C<exit> in a coroutine will not work correctly, so do not do that.	184	The remaining arguments are passed as arguments to the closure.
191		185
192	When the coroutine dies, the program will exit, just as in the main	186	See the C<Coro::State::new> constructor for info about the coroutine
193	program.	187	environment in which coroutines are executed.
194		188
		189	Calling C<exit> in a coroutine will do the same as calling exit outside
		190	the coroutine. Likewise, when the coroutine dies, the program will exit,
		191	just as it would in the main program.
		192
		193	If you do not want that, you can provide a default C<die> handler, or
		194	simply avoid dieing (by use of C<eval>).
		195
195	# create a new coroutine that just prints its arguments	196	Example: Create a new coroutine that just prints its arguments.
		197
196	async {	198	async {
197	print "@_\n";	199	print "@_\n";
198	} 1,2,3,4;	200	} 1,2,3,4;
199		201
200	=cut	202	=cut
201		203
202	sub async(&@) {	204	sub async(&@) {
203	my $pid = new Coro @_;	205	my $coro = new Coro @_;
204	$pid->ready;	206	$coro->ready;
205	$pid	207	$coro
206	}	208	}
		209
		210	=item async_pool { ... } [@args...]
		211
		212	Similar to C<async>, but uses a coroutine pool, so you should not call
		213	terminate or join on it (although you are allowed to), and you get a
		214	coroutine that might have executed other code already (which can be good
		215	or bad :).
		216
		217	On the plus side, this function is faster than creating (and destroying)
		218	a completly new coroutine, so if you need a lot of generic coroutines in
		219	quick successsion, use C<async_pool>, not C<async>.
		220
		221	The code block is executed in an C<eval> context and a warning will be
		222	issued in case of an exception instead of terminating the program, as
		223	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		224	will not work in the expected way, unless you call terminate or cancel,
		225	which somehow defeats the purpose of pooling (but is fine in the
		226	exceptional case).
		227
		228	The priority will be reset to C<0> after each run, tracing will be
		229	disabled, the description will be reset and the default output filehandle
		230	gets restored, so you can change all these. Otherwise the coroutine will
		231	be re-used "as-is": most notably if you change other per-coroutine global
		232	stuff such as C<$/> you I<must needs> revert that change, which is most
		233	simply done by using local as in: C<< local $/ >>.
		234
		235	The idle pool size is limited to C<8> idle coroutines (this can be
		236	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
		237	coros as required.
		238
		239	If you are concerned about pooled coroutines growing a lot because a
		240	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		241	{ terminate }> once per second or so to slowly replenish the pool. In
		242	addition to that, when the stacks used by a handler grows larger than 16kb
		243	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
		244
		245	=cut
		246
		247	our $POOL_SIZE = 8;
		248	our $POOL_RSS = 16 * 1024;
		249	our @async_pool;
		250
		251	sub pool_handler {
		252	my $cb;
		253
		254	while () {
		255	eval {
		256	while () {
		257	_pool_1 $cb;
		258	&$cb;
		259	_pool_2 $cb;
		260	&schedule;
		261	}
		262	};
		263
		264	if ($@) {
		265	last if $@ eq "\3async_pool terminate\2\n";
		266	warn $@;
		267	}
		268	}
		269	}
		270
		271	sub async_pool(&@) {
		272	# this is also inlined into the unblock_scheduler
		273	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		274
		275	$coro->{_invoke} = [@_];
		276	$coro->ready;
		277
		278	$coro
		279	}
		280
		281	=back
		282
		283	=head2 STATIC METHODS
		284
		285	Static methods are actually functions that operate on the current coroutine.
		286
		287	=over 4
207		288
208	=item schedule	289	=item schedule
209		290
210	Calls the scheduler. Please note that the current coroutine will not be put	291	Calls the scheduler. The scheduler will find the next coroutine that is
		292	to be run from the ready queue and switches to it. The next coroutine
		293	to be run is simply the one with the highest priority that is longest
		294	in its ready queue. If there is no coroutine ready, it will clal the
		295	C<$Coro::idle> hook.
		296
		297	Please note that the current coroutine will I<not> be put into the ready
211	into the ready queue, so calling this function usually means you will	298	queue, so calling this function usually means you will never be called
212	never be called again unless something else (e.g. an event handler) calls	299	again unless something else (e.g. an event handler) calls C<< ->ready >>,
213	ready.	300	thus waking you up.
		301
		302	This makes C<schedule> I<the> generic method to use to block the current
		303	coroutine and wait for events: first you remember the current coroutine in
		304	a variable, then arrange for some callback of yours to call C<< ->ready
		305	>> on that once some event happens, and last you call C<schedule> to put
		306	yourself to sleep. Note that a lot of things can wake your coroutine up,
		307	so you need to check whether the event indeed happened, e.g. by storing the
		308	status in a variable.
214		309
215	The canonical way to wait on external events is this:	310	The canonical way to wait on external events is this:
216		311
217	{	312	{
218	# remember current coroutine	313	# remember current coroutine
…		…
223	# wake up sleeping coroutine	318	# wake up sleeping coroutine
224	$current->ready;	319	$current->ready;
225	undef $current;	320	undef $current;
226	};	321	};
227		322
228	# call schedule until event occured.	323	# call schedule until event occurred.
229	# in case we are woken up for other reasons	324	# in case we are woken up for other reasons
230	# (current still defined), loop.	325	# (current still defined), loop.
231	Coro::schedule while $current;	326	Coro::schedule while $current;
232	}	327	}
233		328
234	=item cede	329	=item cede
235		330
236	"Cede" to other coroutines. This function puts the current coroutine into the	331	"Cede" to other coroutines. This function puts the current coroutine into
237	ready queue and calls C<schedule>, which has the effect of giving up the	332	the ready queue and calls C<schedule>, which has the effect of giving
238	current "timeslice" to other coroutines of the same or higher priority.	333	up the current "timeslice" to other coroutines of the same or higher
		334	priority. Once your coroutine gets its turn again it will automatically be
		335	resumed.
		336
		337	This function is often called C<yield> in other languages.
239		338
240	=item Coro::cede_notself	339	=item Coro::cede_notself
241		340
242	Works like cede, but is not exported by default and will cede to any	341	Works like cede, but is not exported by default and will cede to I<any>
243	coroutine, regardless of priority, once.	342	coroutine, regardless of priority. This is useful sometimes to ensure
		343	progress is made.
244		344
245	=item terminate [arg...]	345	=item terminate [arg...]
246		346
247	Terminates the current coroutine with the given status values (see L<cancel>).	347	Terminates the current coroutine with the given status values (see L<cancel>).
		348
		349	=item killall
		350
		351	Kills/terminates/cancels all coroutines except the currently running
		352	one. This is useful after a fork, either in the child or the parent, as
		353	usually only one of them should inherit the running coroutines.
		354
		355	Note that while this will try to free some of the main programs resources,
		356	you cannot free all of them, so if a coroutine that is not the main
		357	program calls this function, there will be some one-time resource leak.
248		358
249	=cut	359	=cut
250		360
251	sub terminate {	361	sub terminate {
252	$current->cancel (@_);	362	$current->cancel (@_);
253	}	363	}
254		364
		365	sub killall {
		366	for (Coro::State::list) {
		367	$_->cancel
		368	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		369	}
		370	}
		371
255	=back	372	=back
256		373
257	# dynamic methods
258
259	=head2 COROUTINE METHODS	374	=head2 COROUTINE METHODS
260		375
261	These are the methods you can call on coroutine objects.	376	These are the methods you can call on coroutine objects (or to create
		377	them).
262		378
263	=over 4	379	=over 4
264		380
265	=item new Coro \&sub [, @args...]	381	=item new Coro \&sub [, @args...]
266		382
267	Create a new coroutine and return it. When the sub returns the coroutine	383	Create a new coroutine and return it. When the sub returns, the coroutine
268	automatically terminates as if C<terminate> with the returned values were	384	automatically terminates as if C<terminate> with the returned values were
269	called. To make the coroutine run you must first put it into the ready queue	385	called. To make the coroutine run you must first put it into the ready
270	by calling the ready method.	386	queue by calling the ready method.
271		387
272	Calling C<exit> in a coroutine will not work correctly, so do not do that.	388	See C<async> and C<Coro::State::new> for additional info about the
		389	coroutine environment.
273		390
274	=cut	391	=cut
275		392
276	sub _run_coro {	393	sub _run_coro {
277	terminate &{+shift};	394	terminate &{+shift};
…		…
283	$class->SUPER::new (\&_run_coro, @_)	400	$class->SUPER::new (\&_run_coro, @_)
284	}	401	}
285		402
286	=item $success = $coroutine->ready	403	=item $success = $coroutine->ready
287		404
288	Put the given coroutine into the ready queue (according to it's priority)	405	Put the given coroutine into the end of its ready queue (there is one
289	and return true. If the coroutine is already in the ready queue, do nothing	406	queue for each priority) and return true. If the coroutine is already in
290	and return false.	407	the ready queue, do nothing and return false.
		408
		409	This ensures that the scheduler will resume this coroutine automatically
		410	once all the coroutines of higher priority and all coroutines of the same
		411	priority that were put into the ready queue earlier have been resumed.
291		412
292	=item $is_ready = $coroutine->is_ready	413	=item $is_ready = $coroutine->is_ready
293		414
294	Return wether the coroutine is currently the ready queue or not,	415	Return whether the coroutine is currently the ready queue or not,
295		416
296	=item $coroutine->cancel (arg...)	417	=item $coroutine->cancel (arg...)
297		418
298	Terminates the given coroutine and makes it return the given arguments as	419	Terminates the given coroutine and makes it return the given arguments as
299	status (default: the empty list). Never returns if the coroutine is the	420	status (default: the empty list). Never returns if the coroutine is the
…		…
301		422
302	=cut	423	=cut
303		424
304	sub cancel {	425	sub cancel {
305	my $self = shift;	426	my $self = shift;
306	$self->{status} = [@_];	427	$self->{_status} = [@_];
307		428
308	if ($current == $self) {	429	if ($current == $self) {
309	push @destroy, $self;	430	push @destroy, $self;
310	$manager->ready;	431	$manager->ready;
311	&schedule while 1;	432	&schedule while 1;
312	} else {	433	} else {
313	$self->_cancel;	434	$self->_cancel;
314	}	435	}
315	}	436	}
316		437
		438	=item $coroutine->throw ([$scalar])
		439
		440	If C<$throw> is specified and defined, it will be thrown as an exception
		441	inside the coroutine at the next convenient point in time (usually after
		442	it gains control at the next schedule/transfer/cede). Otherwise clears the
		443	exception object.
		444
		445	The exception object will be thrown "as is" with the specified scalar in
		446	C<$@>, i.e. if it is a string, no line number or newline will be appended
		447	(unlike with C<die>).
		448
		449	This can be used as a softer means than C<cancel> to ask a coroutine to
		450	end itself, although there is no guarantee that the exception will lead to
		451	termination, and if the exception isn't caught it might well end the whole
		452	program.
		453
		454	You might also think of C<throw> as being the moral equivalent of
		455	C<kill>ing a coroutine with a signal (in this case, a scalar).
		456
317	=item $coroutine->join	457	=item $coroutine->join
318		458
319	Wait until the coroutine terminates and return any values given to the	459	Wait until the coroutine terminates and return any values given to the
320	C<terminate> or C<cancel> functions. C<join> can be called multiple times	460	C<terminate> or C<cancel> functions. C<join> can be called concurrently
321	from multiple coroutine.	461	from multiple coroutines, and all will be resumed and given the status
		462	return once the C<$coroutine> terminates.
322		463
323	=cut	464	=cut
324		465
325	sub join {	466	sub join {
326	my $self = shift;	467	my $self = shift;
327		468
328	unless ($self->{status}) {	469	unless ($self->{_status}) {
329	my $current = $current;	470	my $current = $current;
330		471
331	push @{$self->{destroy_cb}}, sub {	472	push @{$self->{_on_destroy}}, sub {
332	$current->ready;	473	$current->ready;
333	undef $current;	474	undef $current;
334	};	475	};
335		476
336	&schedule while $current;	477	&schedule while $current;
337	}	478	}
338		479
339	wantarray ? @{$self->{status}} : $self->{status}[0];	480	wantarray ? @{$self->{_status}} : $self->{_status}[0];
340	}	481	}
341		482
342	=item $coroutine->on_destroy (\&cb)	483	=item $coroutine->on_destroy (\&cb)
343		484
344	Registers a callback that is called when this coroutine gets destroyed,	485	Registers a callback that is called when this coroutine gets destroyed,
345	but before it is joined. The callback gets passed the terminate arguments,	486	but before it is joined. The callback gets passed the terminate arguments,
346	if any.	487	if any, and I<must not> die, under any circumstances.
347		488
348	=cut	489	=cut
349		490
350	sub on_destroy {	491	sub on_destroy {
351	my ($self, $cb) = @_;	492	my ($self, $cb) = @_;
352		493
353	push @{ $self->{destroy_cb} }, $cb;	494	push @{ $self->{_on_destroy} }, $cb;
354	}	495	}
355		496
356	=item $oldprio = $coroutine->prio ($newprio)	497	=item $oldprio = $coroutine->prio ($newprio)
357		498
358	Sets (or gets, if the argument is missing) the priority of the	499	Sets (or gets, if the argument is missing) the priority of the
…		…
381	higher values mean lower priority, just as in unix).	522	higher values mean lower priority, just as in unix).
382		523
383	=item $olddesc = $coroutine->desc ($newdesc)	524	=item $olddesc = $coroutine->desc ($newdesc)
384		525
385	Sets (or gets in case the argument is missing) the description for this	526	Sets (or gets in case the argument is missing) the description for this
386	coroutine. This is just a free-form string you can associate with a coroutine.	527	coroutine. This is just a free-form string you can associate with a
		528	coroutine.
		529
		530	This method simply sets the C<< $coroutine->{desc} >> member to the given
		531	string. You can modify this member directly if you wish.
387		532
388	=cut	533	=cut
389		534
390	sub desc {	535	sub desc {
391	my $old = $_[0]{desc};	536	my $old = $_[0]{desc};
…		…
400	=over 4	545	=over 4
401		546
402	=item Coro::nready	547	=item Coro::nready
403		548
404	Returns the number of coroutines that are currently in the ready state,	549	Returns the number of coroutines that are currently in the ready state,
405	i.e. that can be swicthed to. The value C<0> means that the only runnable	550	i.e. that can be switched to by calling C<schedule> directory or
		551	indirectly. The value C<0> means that the only runnable coroutine is the
406	coroutine is the currently running one, so C<cede> would have no effect,	552	currently running one, so C<cede> would have no effect, and C<schedule>
407	and C<schedule> would cause a deadlock unless there is an idle handler	553	would cause a deadlock unless there is an idle handler that wakes up some
408	that wakes up some coroutines.	554	coroutines.
409		555
410	=item my $guard = Coro::guard { ... }	556	=item my $guard = Coro::guard { ... }
411		557
412	This creates and returns a guard object. Nothing happens until the objetc	558	This creates and returns a guard object. Nothing happens until the object
413	gets destroyed, in which case the codeblock given as argument will be	559	gets destroyed, in which case the codeblock given as argument will be
414	executed. This is useful to free locks or other resources in case of a	560	executed. This is useful to free locks or other resources in case of a
415	runtime error or when the coroutine gets canceled, as in both cases the	561	runtime error or when the coroutine gets canceled, as in both cases the
416	guard block will be executed. The guard object supports only one method,	562	guard block will be executed. The guard object supports only one method,
417	C<< ->cancel >>, which will keep the codeblock from being executed.	563	C<< ->cancel >>, which will keep the codeblock from being executed.
…		…
442		588
443		589
444	=item unblock_sub { ... }	590	=item unblock_sub { ... }
445		591
446	This utility function takes a BLOCK or code reference and "unblocks" it,	592	This utility function takes a BLOCK or code reference and "unblocks" it,
447	returning the new coderef. This means that the new coderef will return	593	returning a new coderef. Unblocking means that calling the new coderef
448	immediately without blocking, returning nothing, while the original code	594	will return immediately without blocking, returning nothing, while the
449	ref will be called (with parameters) from within its own coroutine.	595	original code ref will be called (with parameters) from within another
		596	coroutine.
450		597
451	The reason this fucntion exists is that many event libraries (such as the	598	The reason this function exists is that many event libraries (such as the
452	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form	599	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
453	of thread-safety). This means you must not block within event callbacks,	600	of thread-safety). This means you must not block within event callbacks,
454	otherwise you might suffer from crashes or worse.	601	otherwise you might suffer from crashes or worse. The only event library
		602	currently known that is safe to use without C<unblock_sub> is L<EV>.
455		603
456	This function allows your callbacks to block by executing them in another	604	This function allows your callbacks to block by executing them in another
457	coroutine where it is safe to block. One example where blocking is handy	605	coroutine where it is safe to block. One example where blocking is handy
458	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	606	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
459	disk.	607	disk, for example.
460		608
461	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	609	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
462	creating event callbacks that want to block.	610	creating event callbacks that want to block.
463		611
464	=cut	612	If your handler does not plan to block (e.g. simply sends a message to
		613	another coroutine, or puts some other coroutine into the ready queue),
		614	there is no reason to use C<unblock_sub>.
465		615
466	our @unblock_pool;	616	Note that you also need to use C<unblock_sub> for any other callbacks that
		617	are indirectly executed by any C-based event loop. For example, when you
		618	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		619	provides callbacks that are the result of some event callback, then you
		620	must not block either, or use C<unblock_sub>.
		621
		622	=cut
		623
467	our @unblock_queue;	624	our @unblock_queue;
468	our $UNBLOCK_POOL_SIZE = 2;
469		625
470	sub unblock_handler_ {	626	# we create a special coro because we want to cede,
471	while () {	627	# to reduce pressure on the coro pool (because most callbacks
472	my ($cb, @arg) = @{ delete $Coro::current->{arg} };	628	# return immediately and can be reused) and because we cannot cede
473	$cb->(@arg);	629	# inside an event callback.
474
475	last if @unblock_pool >= $UNBLOCK_POOL_SIZE;
476	push @unblock_pool, $Coro::current;
477	schedule;
478	}
479	}
480
481	our $unblock_scheduler = async {	630	our $unblock_scheduler = new Coro sub {
482	while () {	631	while () {
483	while (my $cb = pop @unblock_queue) {	632	while (my $cb = pop @unblock_queue) {
484	my $handler = (pop @unblock_pool or new Coro \&unblock_handler_);	633	# this is an inlined copy of async_pool
485	$handler->{arg} = $cb;	634	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		635
		636	$coro->{_invoke} = $cb;
486	$handler->ready;	637	$coro->ready;
487	cede;	638	cede; # for short-lived callbacks, this reduces pressure on the coro pool
488	}	639	}
489		640	schedule; # sleep well
490	schedule;
491	}	641	}
492	};	642	};
		643	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
493		644
494	sub unblock_sub(&) {	645	sub unblock_sub(&) {
495	my $cb = shift;	646	my $cb = shift;
496		647
497	sub {	648	sub {
498	push @unblock_queue, [$cb, @_];	649	unshift @unblock_queue, [$cb, @_];
499	$unblock_scheduler->ready;	650	$unblock_scheduler->ready;
500	}	651	}
501	}	652	}
502		653
503	=back	654	=back
…		…
506		657
507	1;	658	1;
508		659
509	=head1 BUGS/LIMITATIONS	660	=head1 BUGS/LIMITATIONS
510		661
511	- you must make very sure that no coro is still active on global	662	=over 4
512	destruction. very bad things might happen otherwise (usually segfaults).
513		663
		664	=item fork with pthread backend
		665
		666	When Coro is compiled using the pthread backend (which isn't recommended
		667	but required on many BSDs as their libcs are completely broken), then
		668	coroutines will not survive a fork. There is no known workaround except to
		669	fix your libc and use a saner backend.
		670
		671	=item perl process emulation ("threads")
		672
514	- this module is not thread-safe. You should only ever use this module	673	This module is not perl-pseudo-thread-safe. You should only ever use this
515	from the same thread (this requirement might be losened in the future	674	module from the same thread (this requirement might be removed in the
516	to allow per-thread schedulers, but Coro::State does not yet allow	675	future to allow per-thread schedulers, but Coro::State does not yet allow
517	this).	676	this). I recommend disabling thread support and using processes, as having
		677	the windows process emulation enabled under unix roughly halves perl
		678	performance, even when not used.
		679
		680	=item coroutine switching not signal safe
		681
		682	You must not switch to another coroutine from within a signal handler
		683	(only relevant with %SIG - most event libraries provide safe signals).
		684
		685	That means you I<MUST NOT> call any fucntion that might "block" the
		686	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		687	anything that calls those. Everything else, including calling C<ready>,
		688	works.
		689
		690	=back
		691
518		692
519	=head1 SEE ALSO	693	=head1 SEE ALSO
520		694
		695	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		696
		697	Debugging: L<Coro::Debug>.
		698
521	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.	699	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
522		700
523	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.	701	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
524		702
525	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.	703	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
526		704
527	Embedding: L<Coro:MakeMaker>	705	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.
		706
		707	XS API: L<Coro::MakeMaker>.
		708
		709	Low level Configuration, Coroutine Environment: L<Coro::State>.
528		710
529	=head1 AUTHOR	711	=head1 AUTHOR
530		712
531	Marc Lehmann <schmorp@schmorp.de>	713	Marc Lehmann <schmorp@schmorp.de>
532	http://home.schmorp.de/	714	http://home.schmorp.de/

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Revision 1.220 by root, Sun Nov 16 11:12:57 2008 UTC