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

Comparing Coro/Coro.pm (file contents):
Revision 1.14 by root, Tue Jul 17 02:21:56 2001 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 process 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	yield;	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 to	31	This module collection manages coroutines. Coroutines are similar to
24	Threads but don't run in parallel.	32	threads but don't (in general) run in parallel at the same time even
		33	on SMP machines. The specific flavor of coroutine used in this module
		34	also guarantees you that it will not switch between coroutines unless
		35	necessary, at easily-identified points in your program, so locking and
		36	parallel access are rarely an issue, making coroutine programming much
		37	safer and easier than threads programming.
25		38
26	This module is still experimental, see the BUGS section below.	39	Unlike a normal perl program, however, coroutines allow you to have
		40	multiple running interpreters that share data, which is especially useful
		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).
		51
		52	In this module, coroutines are defined as "callchain + lexical variables +
		53	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
		54	its own set of lexicals and its own set of perls most important global
		55	variables (see L<Coro::State> for more configuration).
27		56
28	=cut	57	=cut
29		58
30	package Coro;	59	package Coro;
31		60
		61	use strict qw(vars subs);
		62	no warnings "uninitialized";
		63
32	use Coro::State;	64	use Coro::State;
33		65
34	use base Exporter;	66	use base qw(Coro::State Exporter);
35		67
		68	our $idle; # idle handler
		69	our $main; # main coroutine
		70	our $current; # current coroutine
		71
36	$VERSION = 0.05;	72	our $VERSION = 5.0;
37		73
38	@EXPORT = qw(async yield schedule terminate);	74	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
39	@EXPORT_OK = qw($current);	75	our %EXPORT_TAGS = (
		76	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		77	);
		78	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
40		79
41	{	80	=over 4
42	use subs 'async';
43		81
44	my @async;
45
46	# this way of handling attributes simply is NOT scalable ;()
47	sub import {
48	Coro->export_to_level(1, @_);
49	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
50	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
51	my ($package, $ref) = (shift, shift);
52	my @attrs;
53	for (@_) {
54	if ($_ eq "Coro") {
55	push @async, $ref;
56	} else {
57	push @attrs, @_;
58	}
59	}
60	return $old ? $old->($package, $name, @attrs) : @attrs;
61	};
62	}
63
64	sub INIT {
65	async pop @async while @async;
66	}
67	}
68
69	=item $main	82	=item $Coro::main
70		83
71	This coroutine represents the main program.	84	This variable stores the coroutine object that represents the main
		85	program. While you cna C<ready> it and do most other things you can do to
		86	coroutines, it is mainly useful to compare again C<$Coro::current>, to see
		87	whether you are running in the main program or not.
72		88
73	=cut	89	=cut
74		90
75	our $main = new Coro;	91	# $main is now being initialised by Coro::State
76		92
77	=item $current	93	=item $Coro::current
78		94
79	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).	95	The coroutine object representing the current coroutine (the last
		96	coroutine that the Coro scheduler switched to). The initial value is
		97	C<$Coro::main> (of course).
80		98
81	=cut	99	This variable is B<strictly> I<read-only>. You can take copies of the
		100	value stored in it and use it as any other coroutine object, but you must
		101	not otherwise modify the variable itself.
82		102
83	# maybe some other module used Coro::Specific before...	103	=cut
84	if ($current) {
85	$main->{specific} = $current->{specific};
86	}
87		104
88	our $current = $main;	105	sub current() { $current } # [DEPRECATED]
89		106
90	=item $idle	107	=item $Coro::idle
91		108
92	The coroutine to switch to when no other coroutine is running. The default	109	This variable is mainly useful to integrate Coro into event loops. It is
93	implementation prints "FATAL: deadlock detected" and exits.	110	usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is
		111	pretty low-level functionality.
94		112
95	=cut	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.
96		117
97	# should be done using priorities :(	118	This hook is overwritten by modules such as C<Coro::Timer> and
98	our $idle = new Coro sub {	119	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
99	print STDERR "FATAL: deadlock detected\n";	120	coroutine so the scheduler can run it.
100	exit(51);	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
		130	Please note that if your callback recursively invokes perl (e.g. for event
		131	handlers), then it must be prepared to be called recursively itself.
		132
		133	=cut
		134
		135	$idle = sub {
		136	require Carp;
		137	Carp::croak ("FATAL: deadlock detected");
101	};	138	};
102		139
103	# we really need priorities...	140	sub _cancel {
104	## my @ready; #d#	141	my ($self) = @_;
105	our @ready = (); # the ready queue. hehe, rather broken ;)
106		142
107	# static methods. not really.	143	# free coroutine data and mark as destructed
		144	$self->_destroy
		145	or return;
108		146
109	=head2 STATIC METHODS	147	# call all destruction callbacks
		148	$_->(@{$self->{_status}})
		149	for @{ delete $self->{_on_destroy} \|\| [] };
		150	}
110		151
111	Static methods are actually functions that operate on the current process only.	152	# this coroutine is necessary because a coroutine
		153	# cannot destroy itself.
		154	my @destroy;
		155	my $manager;
		156
		157	$manager = new Coro sub {
		158	while () {
		159	(shift @destroy)->_cancel
		160	while @destroy;
		161
		162	&schedule;
		163	}
		164	};
		165	$manager->{desc} = "[coro manager]";
		166	$manager->prio (PRIO_MAX);
		167
		168	=back
		169
		170	=head2 SIMPLE COROUTINE CREATION
112		171
113	=over 4	172	=over 4
114		173
115	=item async { ... } [@args...]	174	=item async { ... } [@args...]
116		175
117	Create a new asynchronous process and return it's process object	176	Create a new coroutine and return it's coroutine object (usually
118	(usually unused). When the sub returns the new process 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
119	terminated.	182	terminated.
120		183
		184	The remaining arguments are passed as arguments to the closure.
		185
		186	See the C<Coro::State::new> constructor for info about the coroutine
		187	environment in which coroutines are executed.
		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
121	# create a new coroutine that just prints its arguments	196	Example: Create a new coroutine that just prints its arguments.
		197
122	async {	198	async {
123	print "@_\n";	199	print "@_\n";
124	} 1,2,3,4;	200	} 1,2,3,4;
125		201
126	The coderef you submit MUST NOT be a closure that refers to variables
127	in an outer scope. This does NOT work. Pass arguments into it instead.
128
129	=cut	202	=cut
130		203
131	sub async(&@) {	204	sub async(&@) {
132	my $pid = new Coro @_;	205	my $coro = new Coro @_;
133	$pid->ready;	206	$coro->ready;
134	$pid;	207	$coro
135	}	208	}
		209
		210	=item async_pool { ... } [@args...]
		211
		212	Similar to C<async>, but uses a coroutine pool, so you should not call
		213	terminate or join on it (although you are allowed to), and you get a
		214	coroutine that might have executed other code already (which can be good
		215	or bad :).
		216
		217	On the plus side, this function is faster than creating (and destroying)
		218	a completly new coroutine, so if you need a lot of generic coroutines in
		219	quick successsion, use C<async_pool>, not C<async>.
		220
		221	The code block is executed in an C<eval> context and a warning will be
		222	issued in case of an exception instead of terminating the program, as
		223	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		224	will not work in the expected way, unless you call terminate or cancel,
		225	which somehow defeats the purpose of pooling (but is fine in the
		226	exceptional case).
		227
		228	The priority will be reset to C<0> after each run, tracing will be
		229	disabled, the description will be reset and the default output filehandle
		230	gets restored, so you can change all these. Otherwise the coroutine will
		231	be re-used "as-is": most notably if you change other per-coroutine global
		232	stuff such as C<$/> 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	$coro
		279	}
		280
		281	=back
		282
		283	=head2 STATIC METHODS
		284
		285	Static methods are actually functions that operate on the current coroutine.
		286
		287	=over 4
136		288
137	=item schedule	289	=item schedule
138		290
139	Calls the scheduler. Please note that the current process will not be put	291	Calls the scheduler. The scheduler will find the next coroutine that is
		292	to be run from the ready queue and switches to it. The next coroutine
		293	to be run is simply the one with the highest priority that is longest
		294	in its ready queue. If there is no coroutine ready, it will clal the
		295	C<$Coro::idle> hook.
		296
		297	Please note that the current coroutine will I<not> be put into the ready
140	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
141	never be called again.	299	again unless something else (e.g. an event handler) calls C<< ->ready >>,
		300	thus waking you up.
142		301
143	=cut	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.
144		309
145	my $prev;	310	The canonical way to wait on external events is this:
146		311
147	sub schedule {	312	{
148	# should be done using priorities :(	313	# remember current coroutine
149	($prev, $current) = ($current, shift @ready \|\| $idle);	314	my $current = $Coro::current;
150	Coro::State::transfer($prev, $current);
151	}
152		315
153	=item yield	316	# register a hypothetical event handler
154		317	on_event_invoke sub {
155	Yield to other processes. This function puts the current process into the	318	# wake up sleeping coroutine
156	ready queue and calls C<schedule>.
157
158	=cut
159
160	sub yield {
161	$current->ready;	319	$current->ready;
162	&schedule;	320	undef $current;
163	}	321	};
164		322
		323	# call schedule until event occurred.
		324	# in case we are woken up for other reasons
		325	# (current still defined), loop.
		326	Coro::schedule while $current;
		327	}
		328
		329	=item cede
		330
		331	"Cede" to other coroutines. This function puts the current coroutine into
		332	the ready queue and calls C<schedule>, which has the effect of giving
		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.
		338
		339	=item Coro::cede_notself
		340
		341	Works like cede, but is not exported by default and will cede to I<any>
		342	coroutine, regardless of priority. This is useful sometimes to ensure
		343	progress is made.
		344
165	=item terminate	345	=item terminate [arg...]
166		346
167	Terminates the current process.	347	Terminates the current coroutine with the given status values (see L<cancel>).
168		348
169	Future versions of this function will allow result arguments.	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.
170		358
171	=cut	359	=cut
172		360
173	sub terminate {	361	sub terminate {
174	$current->{_results} = [@_];	362	$current->cancel (@_);
175	&schedule;	363	}
		364
		365	sub killall {
		366	for (Coro::State::list) {
		367	$_->cancel
		368	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		369	}
176	}	370	}
177		371
178	=back	372	=back
179		373
180	# dynamic methods
181
182	=head2 PROCESS METHODS	374	=head2 COROUTINE METHODS
183		375
184	These are the methods you can call on process objects.	376	These are the methods you can call on coroutine objects (or to create
		377	them).
185		378
186	=over 4	379	=over 4
187		380
188	=item new Coro \&sub [, @args...]	381	=item new Coro \&sub [, @args...]
189		382
190	Create a new process and return it. When the sub returns the process	383	Create a new coroutine and return it. When the sub returns, the coroutine
191	automatically terminates. To start the process you must first put it into	384	automatically terminates as if C<terminate> with the returned values were
		385	called. To make the coroutine run you must first put it into the ready
192	the ready queue by calling the ready method.	386	queue by calling the ready method.
193		387
194	The coderef you submit MUST NOT be a closure that refers to variables	388	See C<async> and C<Coro::State::new> for additional info about the
195	in an outer scope. This does NOT work. Pass arguments into it instead.	389	coroutine environment.
196		390
197	=cut	391	=cut
198		392
199	sub _newcoro {	393	sub _run_coro {
200	terminate &{+shift};	394	terminate &{+shift};
201	}	395	}
202		396
203	sub new {	397	sub new {
204	my $class = shift;	398	my $class = shift;
205	bless {
206	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
207	}, $class;
208	}
209		399
210	=item $process->ready	400	$class->SUPER::new (\&_run_coro, @_)
		401	}
211		402
212	Put the current process into the ready queue.	403	=item $success = $coroutine->ready
213		404
214	=cut	405	Put the given coroutine into the end of its ready queue (there is one
		406	queue for each priority) and return true. If the coroutine is already in
		407	the ready queue, do nothing and return false.
215		408
216	sub ready {	409	This ensures that the scheduler will resume this coroutine automatically
217	push @ready, $_[0];	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.
		412
		413	=item $is_ready = $coroutine->is_ready
		414
		415	Return whether the coroutine is currently the ready queue or not,
		416
		417	=item $coroutine->cancel (arg...)
		418
		419	Terminates the given coroutine and makes it return the given arguments as
		420	status (default: the empty list). Never returns if the coroutine is the
		421	current coroutine.
		422
		423	=cut
		424
		425	sub cancel {
		426	my $self = shift;
		427	$self->{_status} = [@_];
		428
		429	if ($current == $self) {
		430	push @destroy, $self;
		431	$manager->ready;
		432	&schedule while 1;
		433	} else {
		434	$self->_cancel;
		435	}
		436	}
		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
		457	=item $coroutine->join
		458
		459	Wait until the coroutine terminates and return any values given to the
		460	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		461	from multiple coroutines, and all will be resumed and given the status
		462	return once the C<$coroutine> terminates.
		463
		464	=cut
		465
		466	sub join {
		467	my $self = shift;
		468
		469	unless ($self->{_status}) {
		470	my $current = $current;
		471
		472	push @{$self->{_on_destroy}}, sub {
		473	$current->ready;
		474	undef $current;
		475	};
		476
		477	&schedule while $current;
		478	}
		479
		480	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		481	}
		482
		483	=item $coroutine->on_destroy (\&cb)
		484
		485	Registers a callback that is called when this coroutine gets destroyed,
		486	but before it is joined. The callback gets passed the terminate arguments,
		487	if any, and I<must not> die, under any circumstances.
		488
		489	=cut
		490
		491	sub on_destroy {
		492	my ($self, $cb) = @_;
		493
		494	push @{ $self->{_on_destroy} }, $cb;
		495	}
		496
		497	=item $oldprio = $coroutine->prio ($newprio)
		498
		499	Sets (or gets, if the argument is missing) the priority of the
		500	coroutine. Higher priority coroutines get run before lower priority
		501	coroutines. Priorities are small signed integers (currently -4 .. +3),
		502	that you can refer to using PRIO_xxx constants (use the import tag :prio
		503	to get then):
		504
		505	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		506	3 > 1 > 0 > -1 > -3 > -4
		507
		508	# set priority to HIGH
		509	current->prio(PRIO_HIGH);
		510
		511	The idle coroutine ($Coro::idle) always has a lower priority than any
		512	existing coroutine.
		513
		514	Changing the priority of the current coroutine will take effect immediately,
		515	but changing the priority of coroutines in the ready queue (but not
		516	running) will only take effect after the next schedule (of that
		517	coroutine). This is a bug that will be fixed in some future version.
		518
		519	=item $newprio = $coroutine->nice ($change)
		520
		521	Similar to C<prio>, but subtract the given value from the priority (i.e.
		522	higher values mean lower priority, just as in unix).
		523
		524	=item $olddesc = $coroutine->desc ($newdesc)
		525
		526	Sets (or gets in case the argument is missing) the description for this
		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.
		532
		533	=cut
		534
		535	sub desc {
		536	my $old = $_[0]{desc};
		537	$_[0]{desc} = $_[1] if @_ > 1;
		538	$old;
218	}	539	}
219		540
220	=back	541	=back
221		542
		543	=head2 GLOBAL FUNCTIONS
		544
		545	=over 4
		546
		547	=item Coro::nready
		548
		549	Returns the number of coroutines that are currently in the ready state,
		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
		552	currently running one, so C<cede> would have no effect, and C<schedule>
		553	would cause a deadlock unless there is an idle handler that wakes up some
		554	coroutines.
		555
		556	=item my $guard = Coro::guard { ... }
		557
		558	This creates and returns a guard object. Nothing happens until the object
		559	gets destroyed, in which case the codeblock given as argument will be
		560	executed. This is useful to free locks or other resources in case of a
		561	runtime error or when the coroutine gets canceled, as in both cases the
		562	guard block will be executed. The guard object supports only one method,
		563	C<< ->cancel >>, which will keep the codeblock from being executed.
		564
		565	Example: set some flag and clear it again when the coroutine gets canceled
		566	or the function returns:
		567
		568	sub do_something {
		569	my $guard = Coro::guard { $busy = 0 };
		570	$busy = 1;
		571
		572	# do something that requires $busy to be true
		573	}
		574
		575	=cut
		576
		577	sub guard(&) {
		578	bless \(my $cb = $_[0]), "Coro::guard"
		579	}
		580
		581	sub Coro::guard::cancel {
		582	${$_[0]} = sub { };
		583	}
		584
		585	sub Coro::guard::DESTROY {
		586	${$_[0]}->();
		587	}
		588
		589
		590	=item unblock_sub { ... }
		591
		592	This utility function takes a BLOCK or code reference and "unblocks" it,
		593	returning a new coderef. Unblocking means that calling the new coderef
		594	will return immediately without blocking, returning nothing, while the
		595	original code ref will be called (with parameters) from within another
		596	coroutine.
		597
		598	The reason this function exists is that many event libraries (such as the
		599	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		600	of thread-safety). This means you must not block within event callbacks,
		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>.
		603
		604	This function allows your callbacks to block by executing them in another
		605	coroutine where it is safe to block. One example where blocking is handy
		606	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		607	disk, for example.
		608
		609	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		610	creating event callbacks that want to block.
		611
		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>.
		615
		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
		624	our @unblock_queue;
		625
		626	# we create a special coro because we want to cede,
		627	# to reduce pressure on the coro pool (because most callbacks
		628	# return immediately and can be reused) and because we cannot cede
		629	# inside an event callback.
		630	our $unblock_scheduler = new Coro sub {
		631	while () {
		632	while (my $cb = pop @unblock_queue) {
		633	# this is an inlined copy of async_pool
		634	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		635
		636	$coro->{_invoke} = $cb;
		637	$coro->ready;
		638	cede; # for short-lived callbacks, this reduces pressure on the coro pool
		639	}
		640	schedule; # sleep well
		641	}
		642	};
		643	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
		644
		645	sub unblock_sub(&) {
		646	my $cb = shift;
		647
		648	sub {
		649	unshift @unblock_queue, [$cb, @_];
		650	$unblock_scheduler->ready;
		651	}
		652	}
		653
		654	=back
		655
222	=cut	656	=cut
223		657
224	1;	658	1;
225		659
226	=head1 BUGS	660	=head1 BUGS/LIMITATIONS
227		661
228	- could be faster, especially when the core would introduce special	662	=over 4
229	support for coroutines (like it does for threads).	663
230	- there is still a memleak on coroutine termination that I could not	664	=item fork with pthread backend
231	identify. Could be as small as a single SV.	665
232	- this module is not well-tested.	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
		673	This module is not perl-pseudo-thread-safe. You should only ever use this
		674	module from the same thread (this requirement might be removed in the
		675	future to allow per-thread schedulers, but Coro::State does not yet allow
		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
233		692
234	=head1 SEE ALSO	693	=head1 SEE ALSO
235		694
236	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,	695	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
237	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>.	696
		697	Debugging: L<Coro::Debug>.
		698
		699	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
		700
		701	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		702
		703	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
		704
		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>.
238		710
239	=head1 AUTHOR	711	=head1 AUTHOR
240		712
241	Marc Lehmann <pcg@goof.com>	713	Marc Lehmann <schmorp@schmorp.de>
242	http://www.goof.com/pcg/marc/	714	http://home.schmorp.de/
243		715
244	=cut	716	=cut
245		717

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