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

Comparing Coro/Coro.pm (file contents):
Revision 1.11 by root, Sun Jul 15 03:24:18 2001 UTC vs.
Revision 1.224 by root, Wed Nov 19 05:52:42 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
		31	This module collection manages coroutines. Coroutines are similar to
		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.
		38
		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).
		56
23	=cut	57	=cut
24		58
25	package Coro;	59	package Coro;
26		60
		61	use strict qw(vars subs);
		62	no warnings "uninitialized";
		63
27	use Coro::State;	64	use Coro::State;
28		65
29	use base Exporter;	66	use base qw(Coro::State Exporter);
30		67
		68	our $idle; # idle handler
		69	our $main; # main coroutine
		70	our $current; # current coroutine
		71
31	$VERSION = 0.04;	72	our $VERSION = 5.0;
32		73
33	@EXPORT = qw(async yield schedule);	74	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
34	@EXPORT_OK = qw($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));
35		79
36	{	80	=over 4
37	use subs 'async';
38		81
39	my @async;	82	=item $Coro::main
40		83
41	# this way of handling attributes simply is NOT scalable ;()	84	This variable stores the coroutine object that represents the main
42	sub import {	85	program. While you cna C<ready> it and do most other things you can do to
43	Coro->export_to_level(1, @_);	86	coroutines, it is mainly useful to compare again C<$Coro::current>, to see
44	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};	87	whether you are running in the main program or not.
45	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {	88
46	my ($package, $ref) = (shift, shift);	89	=cut
47	my @attrs;	90
48	for (@_) {	91	# $main is now being initialised by Coro::State
49	if ($_ eq "Coro") {	92
50	push @async, $ref;	93	=item $Coro::current
51	} else {	94
52	push @attrs, @_;	95	The coroutine object representing the current coroutine (the last
		96	coroutine that the Coro scheduler switched to). The initial value is
		97	C<$Coro::main> (of course).
		98
		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.
		102
		103	=cut
		104
		105	sub current() { $current } # [DEPRECATED]
		106
		107	=item $Coro::idle
		108
		109	This variable is mainly useful to integrate Coro into event loops. It is
		110	usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is
		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.
		117
		118	This hook is overwritten by modules such as C<Coro::Timer> and
		119	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
		120	coroutine so the scheduler can run it.
		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	$idle = sub {
		136	require Carp;
		137	Carp::croak ("FATAL: deadlock detected");
		138	};
		139
		140	sub _cancel {
		141	my ($self) = @_;
		142
		143	# free coroutine data and mark as destructed
		144	$self->_destroy
		145	or return;
		146
		147	# call all destruction callbacks
		148	$_->(@{$self->{_status}})
		149	for @{ delete $self->{_on_destroy} \|\| [] };
		150	}
		151
		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
		171
		172	=over 4
		173
		174	=item async { ... } [@args...]
		175
		176	Create a new coroutine and return it's coroutine object (usually
		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
		182	terminated.
		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
		196	Example: Create a new coroutine that just prints its arguments.
		197
		198	async {
		199	print "@_\n";
		200	} 1,2,3,4;
		201
		202	=cut
		203
		204	sub async(&@) {
		205	my $coro = new Coro @_;
		206	$coro->ready;
		207	$coro
		208	}
		209
		210	=item async_pool { ... } [@args...]
		211
		212	Similar to C<async>, but uses a coroutine pool, so you should not call
		213	terminate or join on it (although you are allowed to), and you get a
		214	coroutine that might have executed other code already (which can be good
		215	or bad :).
		216
		217	On the plus side, this function is faster than creating (and destroying)
		218	a completly new coroutine, so if you need a lot of generic coroutines in
		219	quick successsion, use C<async_pool>, not C<async>.
		220
		221	The code block is executed in an C<eval> context and a warning will be
		222	issued in case of an exception instead of terminating the program, as
		223	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		224	will not work in the expected way, unless you call terminate or cancel,
		225	which somehow defeats the purpose of pooling (but is fine in the
		226	exceptional case).
		227
		228	The priority will be reset to C<0> after each run, tracing will be
		229	disabled, the description will be reset and the default output filehandle
		230	gets restored, so you can change all these. Otherwise the coroutine will
		231	be re-used "as-is": most notably if you change other per-coroutine global
		232	stuff such as C<$/> 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 $cb;
53	}	258	&$cb;
		259	_pool_2 $cb;
		260	&schedule;
54	}	261	}
55	return $old ? $old->($package, $name, @attrs) : @attrs;
56	};	262	};
57	}
58		263
59	sub INIT {	264	if ($@) {
60	async pop @async while @async;	265	last if $@ eq "\3async_pool terminate\2\n";
		266	warn $@;
		267	}
61	}	268	}
62	}	269	}
63		270
64	=item $main	271	sub async_pool(&@) {
		272	# this is also inlined into the unblock_scheduler
		273	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
65		274
66	This coroutine represents the main program.	275	$coro->{_invoke} = [@_];
		276	$coro->ready;
67		277
68	=cut	278	$coro
69
70	our $main = new Coro;
71
72	=item $current
73
74	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).
75
76	=cut
77
78	# maybe some other module used Coro::Specific before...
79	if ($current) {
80	$main->{specific} = $current->{specific};
81	}	279	}
82		280
83	our $current = $main;	281	=back
84
85	=item $idle
86
87	The coroutine to switch to when no other coroutine is running. The default
88	implementation prints "FATAL: deadlock detected" and exits.
89
90	=cut
91
92	# should be done using priorities :(
93	our $idle = new Coro sub {
94	print STDERR "FATAL: deadlock detected\n";
95	exit(51);
96	};
97
98	# we really need priorities...
99	my @ready = (); # the ready queue. hehe, rather broken ;)
100
101	# static methods. not really.
102		282
103	=head2 STATIC METHODS	283	=head2 STATIC METHODS
104		284
105	Static methods are actually functions that operate on the current process only.	285	Static methods are actually functions that operate on the current coroutine.
106		286
107	=over 4	287	=over 4
108		288
109	=item async { ... };
110
111	Create a new asynchronous process and return it's process object
112	(usually unused). When the sub returns the new process is automatically
113	terminated.
114
115	=cut
116
117	sub async(&) {
118	my $pid = new Coro $_[0];
119	$pid->ready;
120	$pid;
121	}
122
123	=item schedule	289	=item schedule
124		290
125	Calls the scheduler. Please note that the current process will not be put	291	Calls the scheduler. The scheduler will find the next coroutine that is
		292	to be run from the ready queue and switches to it. The next coroutine
		293	to be run is simply the one with the highest priority that is longest
		294	in its ready queue. If there is no coroutine ready, it will clal the
		295	C<$Coro::idle> hook.
		296
		297	Please note that the current coroutine will I<not> be put into the ready
126	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
127	never be called again.	299	again unless something else (e.g. an event handler) calls C<< ->ready >>,
		300	thus waking you up.
128		301
129	=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.
130		309
131	my $prev;	310	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
132		311
133	sub schedule {
134	# should be done using priorities :(
135	($prev, $current) = ($current, shift @ready \|\| $idle);
136	Coro::State::transfer($prev, $current);
137	}
138
139	=item yield	312	=item cede
140		313
141	Yield to other processes. This function puts the current process into the	314	"Cede" to other coroutines. This function puts the current coroutine into
142	ready queue and calls C<schedule>.	315	the ready queue and calls C<schedule>, which has the effect of giving
		316	up the current "timeslice" to other coroutines of the same or higher
		317	priority. Once your coroutine gets its turn again it will automatically be
		318	resumed.
143		319
144	=cut	320	This function is often called C<yield> in other languages.
145		321
146	sub yield {	322	=item Coro::cede_notself
147	$current->ready;
148	&schedule;
149	}
150		323
		324	Works like cede, but is not exported by default and will cede to I<any>
		325	coroutine, regardless of priority. This is useful sometimes to ensure
		326	progress is made.
		327
151	=item terminate	328	=item terminate [arg...]
152		329
153	Terminates the current process.	330	Terminates the current coroutine with the given status values (see L<cancel>).
		331
		332	=item killall
		333
		334	Kills/terminates/cancels all coroutines except the currently running
		335	one. This is useful after a fork, either in the child or the parent, as
		336	usually only one of them should inherit the running coroutines.
		337
		338	Note that while this will try to free some of the main programs resources,
		339	you cannot free all of them, so if a coroutine that is not the main
		340	program calls this function, there will be some one-time resource leak.
154		341
155	=cut	342	=cut
156		343
157	sub terminate {	344	sub terminate {
158	&schedule;	345	$current->cancel (@_);
		346	}
		347
		348	sub killall {
		349	for (Coro::State::list) {
		350	$_->cancel
		351	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		352	}
159	}	353	}
160		354
161	=back	355	=back
162		356
163	# dynamic methods
164
165	=head2 PROCESS METHODS	357	=head2 COROUTINE METHODS
166		358
167	These are the methods you can call on process objects.	359	These are the methods you can call on coroutine objects (or to create
		360	them).
168		361
169	=over 4	362	=over 4
170		363
171	=item new Coro \⊂	364	=item new Coro \&sub [, @args...]
172		365
173	Create a new process and return it. When the sub returns the process	366	Create a new coroutine and return it. When the sub returns, the coroutine
174	automatically terminates. To start the process you must first put it into	367	automatically terminates as if C<terminate> with the returned values were
		368	called. To make the coroutine run you must first put it into the ready
175	the ready queue by calling the ready method.	369	queue by calling the ready method.
176		370
		371	See C<async> and C<Coro::State::new> for additional info about the
		372	coroutine environment.
		373
177	=cut	374	=cut
		375
		376	sub _run_coro {
		377	terminate &{+shift};
		378	}
178		379
179	sub new {	380	sub new {
180	my $class = shift;	381	my $class = shift;
		382
		383	$class->SUPER::new (\&_run_coro, @_)
		384	}
		385
		386	=item $success = $coroutine->ready
		387
		388	Put the given coroutine into the end of its ready queue (there is one
		389	queue for each priority) and return true. If the coroutine is already in
		390	the ready queue, do nothing and return false.
		391
		392	This ensures that the scheduler will resume this coroutine automatically
		393	once all the coroutines of higher priority and all coroutines of the same
		394	priority that were put into the ready queue earlier have been resumed.
		395
		396	=item $is_ready = $coroutine->is_ready
		397
		398	Return whether the coroutine is currently the ready queue or not,
		399
		400	=item $coroutine->cancel (arg...)
		401
		402	Terminates the given coroutine and makes it return the given arguments as
		403	status (default: the empty list). Never returns if the coroutine is the
		404	current coroutine.
		405
		406	=cut
		407
		408	sub cancel {
		409	my $self = shift;
		410	$self->{_status} = [@_];
		411
		412	if ($current == $self) {
		413	push @destroy, $self;
		414	$manager->ready;
		415	&schedule while 1;
		416	} else {
		417	$self->_cancel;
		418	}
		419	}
		420
		421	=item $coroutine->throw ([$scalar])
		422
		423	If C<$throw> is specified and defined, it will be thrown as an exception
		424	inside the coroutine at the next convenient point in time. Otherwise
		425	clears the exception object.
		426
		427	Coro will check for the exception each time a schedule-like-function
		428	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		429	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		430	detect this case and return early in case an exception is pending.
		431
		432	The exception object will be thrown "as is" with the specified scalar in
		433	C<$@>, i.e. if it is a string, no line number or newline will be appended
		434	(unlike with C<die>).
		435
		436	This can be used as a softer means than C<cancel> to ask a coroutine to
		437	end itself, although there is no guarantee that the exception will lead to
		438	termination, and if the exception isn't caught it might well end the whole
		439	program.
		440
		441	You might also think of C<throw> as being the moral equivalent of
		442	C<kill>ing a coroutine with a signal (in this case, a scalar).
		443
		444	=item $coroutine->join
		445
		446	Wait until the coroutine terminates and return any values given to the
		447	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		448	from multiple coroutines, and all will be resumed and given the status
		449	return once the C<$coroutine> terminates.
		450
		451	=cut
		452
		453	sub join {
		454	my $self = shift;
		455
		456	unless ($self->{_status}) {
		457	my $current = $current;
		458
		459	push @{$self->{_on_destroy}}, sub {
		460	$current->ready;
		461	undef $current;
		462	};
		463
		464	&schedule while $current;
		465	}
		466
		467	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		468	}
		469
		470	=item $coroutine->on_destroy (\&cb)
		471
		472	Registers a callback that is called when this coroutine gets destroyed,
		473	but before it is joined. The callback gets passed the terminate arguments,
		474	if any, and I<must not> die, under any circumstances.
		475
		476	=cut
		477
		478	sub on_destroy {
		479	my ($self, $cb) = @_;
		480
		481	push @{ $self->{_on_destroy} }, $cb;
		482	}
		483
		484	=item $oldprio = $coroutine->prio ($newprio)
		485
		486	Sets (or gets, if the argument is missing) the priority of the
		487	coroutine. Higher priority coroutines get run before lower priority
		488	coroutines. Priorities are small signed integers (currently -4 .. +3),
		489	that you can refer to using PRIO_xxx constants (use the import tag :prio
		490	to get then):
		491
		492	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		493	3 > 1 > 0 > -1 > -3 > -4
		494
		495	# set priority to HIGH
		496	current->prio(PRIO_HIGH);
		497
		498	The idle coroutine ($Coro::idle) always has a lower priority than any
		499	existing coroutine.
		500
		501	Changing the priority of the current coroutine will take effect immediately,
		502	but changing the priority of coroutines in the ready queue (but not
		503	running) will only take effect after the next schedule (of that
		504	coroutine). This is a bug that will be fixed in some future version.
		505
		506	=item $newprio = $coroutine->nice ($change)
		507
		508	Similar to C<prio>, but subtract the given value from the priority (i.e.
		509	higher values mean lower priority, just as in unix).
		510
		511	=item $olddesc = $coroutine->desc ($newdesc)
		512
		513	Sets (or gets in case the argument is missing) the description for this
		514	coroutine. This is just a free-form string you can associate with a
		515	coroutine.
		516
		517	This method simply sets the C<< $coroutine->{desc} >> member to the given
		518	string. You can modify this member directly if you wish.
		519
		520	=cut
		521
		522	sub desc {
181	my $proc = $_[0];	523	my $old = $_[0]{desc};
182	bless {	524	$_[0]{desc} = $_[1] if @_ > 1;
183	_coro_state => new Coro::State ($proc ? sub { &$proc; &terminate } : $proc),	525	$old;
184	}, $class;
185	}
186
187	=item $process->ready
188
189	Put the current process into the ready queue.
190
191	=cut
192
193	sub ready {
194	push @ready, $_[0];
195	}	526	}
196		527
197	=back	528	=back
198		529
		530	=head2 GLOBAL FUNCTIONS
		531
		532	=over 4
		533
		534	=item Coro::nready
		535
		536	Returns the number of coroutines that are currently in the ready state,
		537	i.e. that can be switched to by calling C<schedule> directory or
		538	indirectly. The value C<0> means that the only runnable coroutine is the
		539	currently running one, so C<cede> would have no effect, and C<schedule>
		540	would cause a deadlock unless there is an idle handler that wakes up some
		541	coroutines.
		542
		543	=item my $guard = Coro::guard { ... }
		544
		545	This creates and returns a guard object. Nothing happens until the object
		546	gets destroyed, in which case the codeblock given as argument will be
		547	executed. This is useful to free locks or other resources in case of a
		548	runtime error or when the coroutine gets canceled, as in both cases the
		549	guard block will be executed. The guard object supports only one method,
		550	C<< ->cancel >>, which will keep the codeblock from being executed.
		551
		552	Example: set some flag and clear it again when the coroutine gets canceled
		553	or the function returns:
		554
		555	sub do_something {
		556	my $guard = Coro::guard { $busy = 0 };
		557	$busy = 1;
		558
		559	# do something that requires $busy to be true
		560	}
		561
		562	=cut
		563
		564	sub guard(&) {
		565	bless \(my $cb = $_[0]), "Coro::guard"
		566	}
		567
		568	sub Coro::guard::cancel {
		569	${$_[0]} = sub { };
		570	}
		571
		572	sub Coro::guard::DESTROY {
		573	${$_[0]}->();
		574	}
		575
		576
		577	=item unblock_sub { ... }
		578
		579	This utility function takes a BLOCK or code reference and "unblocks" it,
		580	returning a new coderef. Unblocking means that calling the new coderef
		581	will return immediately without blocking, returning nothing, while the
		582	original code ref will be called (with parameters) from within another
		583	coroutine.
		584
		585	The reason this function exists is that many event libraries (such as the
		586	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		587	of thread-safety). This means you must not block within event callbacks,
		588	otherwise you might suffer from crashes or worse. The only event library
		589	currently known that is safe to use without C<unblock_sub> is L<EV>.
		590
		591	This function allows your callbacks to block by executing them in another
		592	coroutine where it is safe to block. One example where blocking is handy
		593	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		594	disk, for example.
		595
		596	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		597	creating event callbacks that want to block.
		598
		599	If your handler does not plan to block (e.g. simply sends a message to
		600	another coroutine, or puts some other coroutine into the ready queue),
		601	there is no reason to use C<unblock_sub>.
		602
		603	Note that you also need to use C<unblock_sub> for any other callbacks that
		604	are indirectly executed by any C-based event loop. For example, when you
		605	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		606	provides callbacks that are the result of some event callback, then you
		607	must not block either, or use C<unblock_sub>.
		608
		609	=cut
		610
		611	our @unblock_queue;
		612
		613	# we create a special coro because we want to cede,
		614	# to reduce pressure on the coro pool (because most callbacks
		615	# return immediately and can be reused) and because we cannot cede
		616	# inside an event callback.
		617	our $unblock_scheduler = new Coro sub {
		618	while () {
		619	while (my $cb = pop @unblock_queue) {
		620	# this is an inlined copy of async_pool
		621	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		622
		623	$coro->{_invoke} = $cb;
		624	$coro->ready;
		625	cede; # for short-lived callbacks, this reduces pressure on the coro pool
		626	}
		627	schedule; # sleep well
		628	}
		629	};
		630	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
		631
		632	sub unblock_sub(&) {
		633	my $cb = shift;
		634
		635	sub {
		636	unshift @unblock_queue, [$cb, @_];
		637	$unblock_scheduler->ready;
		638	}
		639	}
		640
		641	=item $cb = Coro::rouse_cb
		642
		643	Create and return a "rouse callback". That's a code reference that, when
		644	called, will save its arguments and notify the owner coroutine of the
		645	callback.
		646
		647	See the next function.
		648
		649	=item @args = Coro::rouse_wait [$cb]
		650
		651	Wait for the specified rouse callback (or the last one tht was created in
		652	this coroutine).
		653
		654	As soon as the callback is invoked (or when the calback was invoked before
		655	C<rouse_wait>), it will return a copy of the arguments originally passed
		656	to the rouse callback.
		657
		658	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		659
		660	=back
		661
199	=cut	662	=cut
200		663
201	1;	664	1;
202		665
		666	=head1 HOW TO WAIT FOR A CALLBACK
		667
		668	It is very common for a coroutine to wait for some callback to be
		669	called. This occurs naturally when you use coroutines in an otherwise
		670	event-based program, or when you use event-based libraries.
		671
		672	These typically register a callback for some event, and call that callback
		673	when the event occured. In a coroutine, however, you typically want to
		674	just wait for the event, simplyifying things.
		675
		676	For example C<< AnyEvent->child >> registers a callback to be called when
		677	a specific child has exited:
		678
		679	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		680
		681	But from withina coroutine, you often just want to write this:
		682
		683	my $status = wait_for_child $pid;
		684
		685	Coro offers two functions specifically designed to make this easy,
		686	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		687
		688	The first function, C<rouse_cb>, generates and returns a callback that,
		689	when invoked, will save it's arguments and notify the coroutine that
		690	created the callback.
		691
		692	The second function, C<rouse_wait>, waits for the callback to be called
		693	(by calling C<schedule> to go to sleep) and returns the arguments
		694	originally passed to the callback.
		695
		696	Using these functions, it becomes easy to write the C<wait_for_child>
		697	function mentioned above:
		698
		699	sub wait_for_child($) {
		700	my ($pid) = @_;
		701
		702	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		703
		704	my ($rpid, $rstatus) = Coro::rouse_wait;
		705	$rstatus
		706	}
		707
		708	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		709	you can roll your own, using C<schedule>:
		710
		711	sub wait_for_child($) {
		712	my ($pid) = @_;
		713
		714	# store the current coroutine in $current,
		715	# and provide result variables for the closure passed to ->child
		716	my $current = $Coro::current;
		717	my ($done, $rstatus);
		718
		719	# pass a closure to ->child
		720	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		721	$rstatus = $_[1]; # remember rstatus
		722	$done = 1; # mark $rstatus as valud
		723	});
		724
		725	# wait until the closure has been called
		726	schedule while !$done;
		727
		728	$rstatus
		729	}
		730
		731
		732	=head1 BUGS/LIMITATIONS
		733
		734	=over 4
		735
		736	=item fork with pthread backend
		737
		738	When Coro is compiled using the pthread backend (which isn't recommended
		739	but required on many BSDs as their libcs are completely broken), then
		740	coroutines will not survive a fork. There is no known workaround except to
		741	fix your libc and use a saner backend.
		742
		743	=item perl process emulation ("threads")
		744
		745	This module is not perl-pseudo-thread-safe. You should only ever use this
		746	module from the same thread (this requirement might be removed in the
		747	future to allow per-thread schedulers, but Coro::State does not yet allow
		748	this). I recommend disabling thread support and using processes, as having
		749	the windows process emulation enabled under unix roughly halves perl
		750	performance, even when not used.
		751
		752	=item coroutine switching not signal safe
		753
		754	You must not switch to another coroutine from within a signal handler
		755	(only relevant with %SIG - most event libraries provide safe signals).
		756
		757	That means you I<MUST NOT> call any function that might "block" the
		758	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		759	anything that calls those. Everything else, including calling C<ready>,
		760	works.
		761
		762	=back
		763
		764
203	=head1 SEE ALSO	765	=head1 SEE ALSO
204		766
205	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,	767	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
206	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>.	768
		769	Debugging: L<Coro::Debug>.
		770
		771	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
		772
		773	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		774
		775	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
		776
		777	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.
		778
		779	XS API: L<Coro::MakeMaker>.
		780
		781	Low level Configuration, Coroutine Environment: L<Coro::State>.
207		782
208	=head1 AUTHOR	783	=head1 AUTHOR
209		784
210	Marc Lehmann <pcg@goof.com>	785	Marc Lehmann <schmorp@schmorp.de>
211	http://www.goof.com/pcg/marc/	786	http://home.schmorp.de/
212		787
213	=cut	788	=cut
214		789

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Comparing Coro/Coro.pm (file contents):
Revision 1.11 by root, Sun Jul 15 03:24:18 2001 UTC vs.
Revision 1.224 by root, Wed Nov 19 05:52:42 2008 UTC