[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 1.223 by root, Tue Nov 18 10:44:07 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<$throw> is specified and defined, it will be thrown as an exception
		441	inside the coroutine at the next convenient point in time. Otherwise
		442	clears the exception object.
		443
		444	Coro will check for the exception each time a schedule-like-function
		445	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		446	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		447	detect this case and return early in case an exception is pending.
		448
		449	The exception object will be thrown "as is" with the specified scalar in
		450	C<$@>, i.e. if it is a string, no line number or newline will be appended
		451	(unlike with C<die>).
		452
		453	This can be used as a softer means than C<cancel> to ask a coroutine to
		454	end itself, although there is no guarantee that the exception will lead to
		455	termination, and if the exception isn't caught it might well end the whole
		456	program.
		457
		458	You might also think of C<throw> as being the moral equivalent of
		459	C<kill>ing a coroutine with a signal (in this case, a scalar).
		460
		461	=item $coroutine->join
		462
		463	Wait until the coroutine terminates and return any values given to the
		464	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		465	from multiple coroutines, and all will be resumed and given the status
		466	return once the C<$coroutine> terminates.
		467
		468	=cut
		469
		470	sub join {
		471	my $self = shift;
		472
		473	unless ($self->{_status}) {
		474	my $current = $current;
		475
		476	push @{$self->{_on_destroy}}, sub {
		477	$current->ready;
		478	undef $current;
		479	};
		480
		481	&schedule while $current;
		482	}
		483
		484	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		485	}
		486
		487	=item $coroutine->on_destroy (\&cb)
		488
		489	Registers a callback that is called when this coroutine gets destroyed,
		490	but before it is joined. The callback gets passed the terminate arguments,
		491	if any, and I<must not> die, under any circumstances.
		492
		493	=cut
		494
		495	sub on_destroy {
		496	my ($self, $cb) = @_;
		497
		498	push @{ $self->{_on_destroy} }, $cb;
		499	}
		500
		501	=item $oldprio = $coroutine->prio ($newprio)
		502
		503	Sets (or gets, if the argument is missing) the priority of the
		504	coroutine. Higher priority coroutines get run before lower priority
		505	coroutines. Priorities are small signed integers (currently -4 .. +3),
		506	that you can refer to using PRIO_xxx constants (use the import tag :prio
		507	to get then):
		508
		509	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		510	3 > 1 > 0 > -1 > -3 > -4
		511
		512	# set priority to HIGH
		513	current->prio(PRIO_HIGH);
		514
		515	The idle coroutine ($Coro::idle) always has a lower priority than any
		516	existing coroutine.
		517
		518	Changing the priority of the current coroutine will take effect immediately,
		519	but changing the priority of coroutines in the ready queue (but not
		520	running) will only take effect after the next schedule (of that
		521	coroutine). This is a bug that will be fixed in some future version.
		522
		523	=item $newprio = $coroutine->nice ($change)
		524
		525	Similar to C<prio>, but subtract the given value from the priority (i.e.
		526	higher values mean lower priority, just as in unix).
		527
		528	=item $olddesc = $coroutine->desc ($newdesc)
		529
		530	Sets (or gets in case the argument is missing) the description for this
		531	coroutine. This is just a free-form string you can associate with a
		532	coroutine.
		533
		534	This method simply sets the C<< $coroutine->{desc} >> member to the given
		535	string. You can modify this member directly if you wish.
		536
		537	=cut
		538
		539	sub desc {
		540	my $old = $_[0]{desc};
		541	$_[0]{desc} = $_[1] if @_ > 1;
		542	$old;
218	}	543	}
219		544
220	=back	545	=back
221		546
		547	=head2 GLOBAL FUNCTIONS
		548
		549	=over 4
		550
		551	=item Coro::nready
		552
		553	Returns the number of coroutines that are currently in the ready state,
		554	i.e. that can be switched to by calling C<schedule> directory or
		555	indirectly. The value C<0> means that the only runnable coroutine is the
		556	currently running one, so C<cede> would have no effect, and C<schedule>
		557	would cause a deadlock unless there is an idle handler that wakes up some
		558	coroutines.
		559
		560	=item my $guard = Coro::guard { ... }
		561
		562	This creates and returns a guard object. Nothing happens until the object
		563	gets destroyed, in which case the codeblock given as argument will be
		564	executed. This is useful to free locks or other resources in case of a
		565	runtime error or when the coroutine gets canceled, as in both cases the
		566	guard block will be executed. The guard object supports only one method,
		567	C<< ->cancel >>, which will keep the codeblock from being executed.
		568
		569	Example: set some flag and clear it again when the coroutine gets canceled
		570	or the function returns:
		571
		572	sub do_something {
		573	my $guard = Coro::guard { $busy = 0 };
		574	$busy = 1;
		575
		576	# do something that requires $busy to be true
		577	}
		578
		579	=cut
		580
		581	sub guard(&) {
		582	bless \(my $cb = $_[0]), "Coro::guard"
		583	}
		584
		585	sub Coro::guard::cancel {
		586	${$_[0]} = sub { };
		587	}
		588
		589	sub Coro::guard::DESTROY {
		590	${$_[0]}->();
		591	}
		592
		593
		594	=item unblock_sub { ... }
		595
		596	This utility function takes a BLOCK or code reference and "unblocks" it,
		597	returning a new coderef. Unblocking means that calling the new coderef
		598	will return immediately without blocking, returning nothing, while the
		599	original code ref will be called (with parameters) from within another
		600	coroutine.
		601
		602	The reason this function exists is that many event libraries (such as the
		603	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		604	of thread-safety). This means you must not block within event callbacks,
		605	otherwise you might suffer from crashes or worse. The only event library
		606	currently known that is safe to use without C<unblock_sub> is L<EV>.
		607
		608	This function allows your callbacks to block by executing them in another
		609	coroutine where it is safe to block. One example where blocking is handy
		610	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		611	disk, for example.
		612
		613	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		614	creating event callbacks that want to block.
		615
		616	If your handler does not plan to block (e.g. simply sends a message to
		617	another coroutine, or puts some other coroutine into the ready queue),
		618	there is no reason to use C<unblock_sub>.
		619
		620	Note that you also need to use C<unblock_sub> for any other callbacks that
		621	are indirectly executed by any C-based event loop. For example, when you
		622	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		623	provides callbacks that are the result of some event callback, then you
		624	must not block either, or use C<unblock_sub>.
		625
		626	=cut
		627
		628	our @unblock_queue;
		629
		630	# we create a special coro because we want to cede,
		631	# to reduce pressure on the coro pool (because most callbacks
		632	# return immediately and can be reused) and because we cannot cede
		633	# inside an event callback.
		634	our $unblock_scheduler = new Coro sub {
		635	while () {
		636	while (my $cb = pop @unblock_queue) {
		637	# this is an inlined copy of async_pool
		638	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		639
		640	$coro->{_invoke} = $cb;
		641	$coro->ready;
		642	cede; # for short-lived callbacks, this reduces pressure on the coro pool
		643	}
		644	schedule; # sleep well
		645	}
		646	};
		647	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
		648
		649	sub unblock_sub(&) {
		650	my $cb = shift;
		651
		652	sub {
		653	unshift @unblock_queue, [$cb, @_];
		654	$unblock_scheduler->ready;
		655	}
		656	}
		657
		658	=back
		659
222	=cut	660	=cut
223		661
224	1;	662	1;
225		663
226	=head1 BUGS	664	=head1 BUGS/LIMITATIONS
227		665
228	- could be faster, especially when the core would introduce special	666	=over 4
229	support for coroutines (like it does for threads).	667
230	- there is still a memleak on coroutine termination that I could not	668	=item fork with pthread backend
231	identify. Could be as small as a single SV.	669
232	- this module is not well-tested.	670	When Coro is compiled using the pthread backend (which isn't recommended
		671	but required on many BSDs as their libcs are completely broken), then
		672	coroutines will not survive a fork. There is no known workaround except to
		673	fix your libc and use a saner backend.
		674
		675	=item perl process emulation ("threads")
		676
		677	This module is not perl-pseudo-thread-safe. You should only ever use this
		678	module from the same thread (this requirement might be removed in the
		679	future to allow per-thread schedulers, but Coro::State does not yet allow
		680	this). I recommend disabling thread support and using processes, as having
		681	the windows process emulation enabled under unix roughly halves perl
		682	performance, even when not used.
		683
		684	=item coroutine switching not signal safe
		685
		686	You must not switch to another coroutine from within a signal handler
		687	(only relevant with %SIG - most event libraries provide safe signals).
		688
		689	That means you I<MUST NOT> call any function that might "block" the
		690	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		691	anything that calls those. Everything else, including calling C<ready>,
		692	works.
		693
		694	=back
		695
233		696
234	=head1 SEE ALSO	697	=head1 SEE ALSO
235		698
236	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,	699	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
237	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>.	700
		701	Debugging: L<Coro::Debug>.
		702
		703	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
		704
		705	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		706
		707	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
		708
		709	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.
		710
		711	XS API: L<Coro::MakeMaker>.
		712
		713	Low level Configuration, Coroutine Environment: L<Coro::State>.
238		714
239	=head1 AUTHOR	715	=head1 AUTHOR
240		716
241	Marc Lehmann <pcg@goof.com>	717	Marc Lehmann <schmorp@schmorp.de>
242	http://www.goof.com/pcg/marc/	718	http://home.schmorp.de/
243		719
244	=cut	720	=cut
245		721

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Revision 1.223 by root, Tue Nov 18 10:44:07 2008 UTC