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1	=head1 NAME	1	=head1 NAME
2		2
3	Coro - create and manage simple coroutines	3	Coro - the only real threads in perl
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use Coro;	7	use Coro;
8		8
9	$new = new Coro sub {	9	async {
10	print "in coroutine, switching back\n";	10	# some asynchronous thread of execution
11	$new->transfer($main);	11	print "2\n";
12	print "in coroutine again, switching back\n";	12	cede; # yield back to main
13	$new->transfer($main);	13	print "4\n";
14	};	14	};
15		15	print "1\n";
16	$main = new Coro;	16	cede; # yield to coro
17		17	print "3\n";
18	print "in main, switching to coroutine\n";	18	cede; # and again
19	$main->transfer($new);	19
20	print "back in main, switch to coroutine again\n";	20	# use locking
21	$main->transfer($new);	21	my $lock = new Coro::Semaphore;
22	print "back in main\n";	22	my $locked;
		23
		24	$lock->down;
		25	$locked = 1;
		26	$lock->up;
23		27
24	=head1 DESCRIPTION	28	=head1 DESCRIPTION
25		29
26	This module implements coroutines. Coroutines, similar to continuations,	30	For a tutorial-style introduction, please read the L<Coro::Intro>
27	allow you to run more than one "thread of execution" in parallel. Unlike	31	manpage. This manpage mainly contains reference information.
28	threads this, only voluntary switching is used so locking problems are
29	greatly reduced.
30		32
31	Although this is the "main" module of the Coro family it provides only	33	This module collection manages continuations in general, most often in
32	low-level functionality. See L<Coro::Process> and related modules for a	34	the form of cooperative threads (also called coros, or simply "coro"
33	more useful process abstraction including scheduling.	35	in the documentation). They are similar to kernel threads but don't (in
		36	general) run in parallel at the same time even on SMP machines. The
		37	specific flavor of thread offered by this module also guarantees you that
		38	it will not switch between threads unless necessary, at easily-identified
		39	points in your program, so locking and parallel access are rarely an
		40	issue, making thread programming much safer and easier than using other
		41	thread models.
		42
		43	Unlike the so-called "Perl threads" (which are not actually real threads
		44	but only the windows process emulation (see section of same name for
		45	more details) ported to UNIX, and as such act as processes), Coro
		46	provides a full shared address space, which makes communication between
		47	threads very easy. And coro threads are fast, too: disabling the Windows
		48	process emulation code in your perl and using Coro can easily result in
		49	a two to four times speed increase for your programs. A parallel matrix
		50	multiplication benchmark (very communication-intensive) runs over 300
		51	times faster on a single core than perls pseudo-threads on a quad core
		52	using all four cores.
		53
		54	Coro achieves that by supporting multiple running interpreters that share
		55	data, which is especially useful to code pseudo-parallel processes and
		56	for event-based programming, such as multiple HTTP-GET requests running
		57	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
		58	into an event-based environment.
		59
		60	In this module, a thread is defined as "callchain + lexical variables +
		61	some package variables + C stack), that is, a thread has its own callchain,
		62	its own set of lexicals and its own set of perls most important global
		63	variables (see L<Coro::State> for more configuration and background info).
		64
		65	See also the C<SEE ALSO> section at the end of this document - the Coro
		66	module family is quite large.
		67
		68	=head1 CORO THREAD LIFE CYCLE
		69
		70	During the long and exciting (or not) life of a coro thread, it goes
		71	through a number of states:
34		72
35	=over 4	73	=over 4
36		74
		75	=item 1. Creation
		76
		77	The first thing in the life of a coro thread is it's creation -
		78	obviously. The typical way to create a thread is to call the C<async
		79	BLOCK> function:
		80
		81	async {
		82	# thread code goes here
		83	};
		84
		85	You can also pass arguments, which are put in C<@_>:
		86
		87	async {
		88	print $_[1]; # prints 2
		89	} 1, 2, 3;
		90
		91	This creates a new coro thread and puts it into the ready queue, meaning
		92	it will run as soon as the CPU is free for it.
		93
		94	C<async> will return a Coro object - you can store this for future
		95	reference or ignore it - a thread that is running, ready to run or waiting
		96	for some event is alive on it's own.
		97
		98	Another way to create a thread is to call the C<new> constructor with a
		99	code-reference:
		100
		101	new Coro sub {
		102	# thread code goes here
		103	}, @optional_arguments;
		104
		105	This is quite similar to calling C<async>, but the important difference is
		106	that the new thread is not put into the ready queue, so the thread will
		107	not run until somebody puts it there. C<async> is, therefore, identical to
		108	this sequence:
		109
		110	my $coro = new Coro sub {
		111	# thread code goes here
		112	};
		113	$coro->ready;
		114	return $coro;
		115
		116	=item 2. Startup
		117
		118	When a new coro thread is created, only a copy of the code reference
		119	and the arguments are stored, no extra memory for stacks and so on is
		120	allocated, keeping the coro thread in a low-memory state.
		121
		122	Only when it actually starts executing will all the resources be finally
		123	allocated.
		124
		125	The optional arguments specified at coro creation are available in C<@_>,
		126	similar to function calls.
		127
		128	=item 3. Running / Blocking
		129
		130	A lot can happen after the coro thread has started running. Quite usually,
		131	it will not run to the end in one go (because you could use a function
		132	instead), but it will give up the CPU regularly because it waits for
		133	external events.
		134
		135	As long as a coro thread runs, its Coro object is available in the global
		136	variable C<$Coro::current>.
		137
		138	The low-level way to give up the CPU is to call the scheduler, which
		139	selects a new coro thread to run:
		140
		141	Coro::schedule;
		142
		143	Since running threads are not in the ready queue, calling the scheduler
		144	without doing anything else will block the coro thread forever - you need
		145	to arrange either for the coro to put woken up (readied) by some other
		146	event or some other thread, or you can put it into the ready queue before
		147	scheduling:
		148
		149	# this is exactly what Coro::cede does
		150	$Coro::current->ready;
		151	Coro::schedule;
		152
		153	All the higher-level synchronisation methods (Coro::Semaphore,
		154	Coro::rouse_*...) are actually implemented via C<< ->ready >> and C<<
		155	Coro::schedule >>.
		156
		157	While the coro thread is running it also might get assigned a C-level
		158	thread, or the C-level thread might be unassigned from it, as the Coro
		159	runtime wishes. A C-level thread needs to be assigned when your perl
		160	thread calls into some C-level function and that function in turn calls
		161	perl and perl then wants to switch coroutines. This happens most often
		162	when you run an event loop and block in the callback, or when perl
		163	itself calls some function such as C<AUTOLOAD> or methods via the C<tie>
		164	mechanism.
		165
		166	=item 4. Termination
		167
		168	Many threads actually terminate after some time. There are a number of
		169	ways to terminate a coro thread, the simplest is returning from the
		170	top-level code reference:
		171
		172	async {
		173	# after returning from here, the coro thread is terminated
		174	};
		175
		176	async {
		177	return if 0.5 < rand; # terminate a little earlier, maybe
		178	print "got a chance to print this\n";
		179	# or here
		180	};
		181
		182	Any values returned from the coroutine can be recovered using C<< ->join
		183	>>:
		184
		185	my $coro = async {
		186	"hello, world\n" # return a string
		187	};
		188
		189	my $hello_world = $coro->join;
		190
		191	print $hello_world;
		192
		193	Another way to terminate is to call C<< Coro::terminate >>, which at any
		194	subroutine call nesting level:
		195
		196	async {
		197	Coro::terminate "return value 1", "return value 2";
		198	};
		199
		200	Yet another way is to C<< ->cancel >> (or C<< ->safe_cancel >>) the coro
		201	thread from another thread:
		202
		203	my $coro = async {
		204	exit 1;
		205	};
		206
		207	$coro->cancel; # also accepts values for ->join to retrieve
		208
		209	Cancellation I<can> be dangerous - it's a bit like calling C<exit> without
		210	actually exiting, and might leave C libraries and XS modules in a weird
		211	state. Unlike other thread implementations, however, Coro is exceptionally
		212	safe with regards to cancellation, as perl will always be in a consistent
		213	state, and for those cases where you want to do truly marvellous things
		214	with your coro while it is being cancelled - that is, make sure all
		215	cleanup code is executed from the thread being cancelled - there is even a
		216	C<< ->safe_cancel >> method.
		217
		218	So, cancelling a thread that runs in an XS event loop might not be the
		219	best idea, but any other combination that deals with perl only (cancelling
		220	when a thread is in a C<tie> method or an C<AUTOLOAD> for example) is
		221	safe.
		222
		223	Last not least, a coro thread object that isn't referenced is C<<
		224	->cancel >>'ed automatically - just like other objects in Perl. This
		225	is not such a common case, however - a running thread is referencedy by
		226	C<$Coro::current>, a thread ready to run is referenced by the ready queue,
		227	a thread waiting on a lock or semaphore is referenced by being in some
		228	wait list and so on. But a thread that isn't in any of those queues gets
		229	cancelled:
		230
		231	async {
		232	schedule; # cede to other coros, don't go into the ready queue
		233	};
		234
		235	cede;
		236	# now the async above is destroyed, as it is not referenced by anything.
		237
		238	A slightly embellished example might make it clearer:
		239
		240	async {
		241	my $guard = Guard::guard { print "destroyed\n" };
		242	schedule while 1;
		243	};
		244
		245	cede;
		246
		247	Superficially one might not expect any output - since the C<async>
		248	implements an endless loop, the C<$guard> will not be cleaned up. However,
		249	since the thread object returned by C<async> is not stored anywhere, the
		250	thread is initially referenced because it is in the ready queue, when it
		251	runs it is referenced by C<$Coro::current>, but when it calls C<schedule>,
		252	it gets C<cancel>ed causing the guard object to be destroyed (see the next
		253	section), and printing it's message.
		254
		255	If this seems a bit drastic, remember that this only happens when nothing
		256	references the thread anymore, which means there is no way to further
		257	execute it, ever. The only options at this point are leaking the thread,
		258	or cleaning it up, which brings us to...
		259
		260	=item 5. Cleanup
		261
		262	Threads will allocate various resources. Most but not all will be returned
		263	when a thread terminates, during clean-up.
		264
		265	Cleanup is quite similar to throwing an uncaught exception: perl will
		266	work it's way up through all subroutine calls and blocks. On it's way, it
		267	will release all C<my> variables, undo all C<local>'s and free any other
		268	resources truly local to the thread.
		269
		270	So, a common way to free resources is to keep them referenced only by my
		271	variables:
		272
		273	async {
		274	my $big_cache = new Cache ...;
		275	};
		276
		277	If there are no other references, then the C<$big_cache> object will be
		278	freed when the thread terminates, regardless of how it does so.
		279
		280	What it does C<NOT> do is unlock any Coro::Semaphores or similar
		281	resources, but that's where the C<guard> methods come in handy:
		282
		283	my $sem = new Coro::Semaphore;
		284
		285	async {
		286	my $lock_guard = $sem->guard;
		287	# if we return, or die or get cancelled, here,
		288	# then the semaphore will be "up"ed.
		289	};
		290
		291	The C<Guard::guard> function comes in handy for any custom cleanup you
		292	might want to do (but you cannot switch to other coroutines from those
		293	code blocks):
		294
		295	async {
		296	my $window = new Gtk2::Window "toplevel";
		297	# The window will not be cleaned up automatically, even when $window
		298	# gets freed, so use a guard to ensure it's destruction
		299	# in case of an error:
		300	my $window_guard = Guard::guard { $window->destroy };
		301
		302	# we are safe here
		303	};
		304
		305	Last not least, C<local> can often be handy, too, e.g. when temporarily
		306	replacing the coro thread description:
		307
		308	sub myfunction {
		309	local $Coro::current->{desc} = "inside myfunction(@_)";
		310
		311	# if we return or die here, the description will be restored
		312	}
		313
		314	=item 6. Viva La Zombie Muerte
		315
		316	Even after a thread has terminated and cleaned up its resources, the Coro
		317	object still is there and stores the return values of the thread.
		318
		319	When there are no other references, it will simply be cleaned up and
		320	freed.
		321
		322	If there areany references, the Coro object will stay around, and you
		323	can call C<< ->join >> as many times as you wish to retrieve the result
		324	values:
		325
		326	async {
		327	print "hi\n";
		328	1
		329	};
		330
		331	# run the async above, and free everything before returning
		332	# from Coro::cede:
		333	Coro::cede;
		334
		335	{
		336	my $coro = async {
		337	print "hi\n";
		338	1
		339	};
		340
		341	# run the async above, and clean up, but do not free the coro
		342	# object:
		343	Coro::cede;
		344
		345	# optionally retrieve the result values
		346	my @results = $coro->join;
		347
		348	# now $coro goes out of scope, and presumably gets freed
		349	};
		350
		351	=back
		352
37	=cut	353	=cut
38		354
39	package Coro;	355	package Coro;
40		356
41	BEGIN {	357	use common::sense;
42	$VERSION = 0.03;
43		358
44	require XSLoader;	359	use Carp ();
45	XSLoader::load Coro, $VERSION;	360
		361	use Guard ();
		362
		363	use Coro::State;
		364
		365	use base qw(Coro::State Exporter);
		366
		367	our $idle; # idle handler
		368	our $main; # main coro
		369	our $current; # current coro
		370
		371	our $VERSION = 6.48;
		372
		373	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
		374	our %EXPORT_TAGS = (
		375	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		376	);
		377	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
		378
		379	=head1 GLOBAL VARIABLES
		380
		381	=over 4
		382
		383	=item $Coro::main
		384
		385	This variable stores the Coro object that represents the main
		386	program. While you can C<ready> it and do most other things you can do to
		387	coro, it is mainly useful to compare again C<$Coro::current>, to see
		388	whether you are running in the main program or not.
		389
		390	=cut
		391
		392	# $main is now being initialised by Coro::State
		393
		394	=item $Coro::current
		395
		396	The Coro object representing the current coro (the last
		397	coro that the Coro scheduler switched to). The initial value is
		398	C<$Coro::main> (of course).
		399
		400	This variable is B<strictly> I<read-only>. You can take copies of the
		401	value stored in it and use it as any other Coro object, but you must
		402	not otherwise modify the variable itself.
		403
		404	=cut
		405
		406	sub current() { $current } # [DEPRECATED]
		407
		408	=item $Coro::idle
		409
		410	This variable is mainly useful to integrate Coro into event loops. It is
		411	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
		412	pretty low-level functionality.
		413
		414	This variable stores a Coro object that is put into the ready queue when
		415	there are no other ready threads (without invoking any ready hooks).
		416
		417	The default implementation dies with "FATAL: deadlock detected.", followed
		418	by a thread listing, because the program has no other way to continue.
		419
		420	This hook is overwritten by modules such as C<Coro::EV> and
		421	C<Coro::AnyEvent> to wait on an external event that hopefully wakes up a
		422	coro so the scheduler can run it.
		423
		424	See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
		425
		426	=cut
		427
		428	# ||= because other modules could have provided their own by now
		429	$idle ||= new Coro sub {
		430	require Coro::Debug;
		431	die "FATAL: deadlock detected.\n"
		432	. Coro::Debug::ps_listing ();
		433	};
		434
		435	# this coro is necessary because a coro
		436	# cannot destroy itself.
		437	our @destroy;
		438	our $manager;
		439
		440	$manager = new Coro sub {
		441	while () {
		442	_destroy shift @destroy
		443	while @destroy;
		444
		445	&schedule;
		446	}
		447	};
		448	$manager->{desc} = "[coro manager]";
		449	$manager->prio (PRIO_MAX);
		450
		451	=back
		452
		453	=head1 SIMPLE CORO CREATION
		454
		455	=over 4
		456
		457	=item async { ... } [@args...]
		458
		459	Create a new coro and return its Coro object (usually
		460	unused). The coro will be put into the ready queue, so
		461	it will start running automatically on the next scheduler run.
		462
		463	The first argument is a codeblock/closure that should be executed in the
		464	coro. When it returns argument returns the coro is automatically
		465	terminated.
		466
		467	The remaining arguments are passed as arguments to the closure.
		468
		469	See the C<Coro::State::new> constructor for info about the coro
		470	environment in which coro are executed.
		471
		472	Calling C<exit> in a coro will do the same as calling exit outside
		473	the coro. Likewise, when the coro dies, the program will exit,
		474	just as it would in the main program.
		475
		476	If you do not want that, you can provide a default C<die> handler, or
		477	simply avoid dieing (by use of C<eval>).
		478
		479	Example: Create a new coro that just prints its arguments.
		480
		481	async {
		482	print "@_\n";
		483	} 1,2,3,4;
		484
		485	=item async_pool { ... } [@args...]
		486
		487	Similar to C<async>, but uses a coro pool, so you should not call
		488	terminate or join on it (although you are allowed to), and you get a
		489	coro that might have executed other code already (which can be good
		490	or bad :).
		491
		492	On the plus side, this function is about twice as fast as creating (and
		493	destroying) a completely new coro, so if you need a lot of generic
		494	coros in quick successsion, use C<async_pool>, not C<async>.
		495
		496	The code block is executed in an C<eval> context and a warning will be
		497	issued in case of an exception instead of terminating the program, as
		498	C<async> does. As the coro is being reused, stuff like C<on_destroy>
		499	will not work in the expected way, unless you call terminate or cancel,
		500	which somehow defeats the purpose of pooling (but is fine in the
		501	exceptional case).
		502
		503	The priority will be reset to C<0> after each run, tracing will be
		504	disabled, the description will be reset and the default output filehandle
		505	gets restored, so you can change all these. Otherwise the coro will
		506	be re-used "as-is": most notably if you change other per-coro global
		507	stuff such as C<$/> you I<must needs> revert that change, which is most
		508	simply done by using local as in: C<< local $/ >>.
		509
		510	The idle pool size is limited to C<8> idle coros (this can be
		511	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
		512	coros as required.
		513
		514	If you are concerned about pooled coros growing a lot because a
		515	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		516	{ terminate }> once per second or so to slowly replenish the pool. In
		517	addition to that, when the stacks used by a handler grows larger than 32kb
		518	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
		519
		520	=cut
		521
		522	our $POOL_SIZE = 8;
		523	our $POOL_RSS = 32 * 1024;
		524	our @async_pool;
		525
		526	sub pool_handler {
		527	while () {
		528	eval {
		529	&{&_pool_handler} while 1;
		530	};
		531
		532	warn $@ if $@;
		533	}
46	}	534	}
47		535
48	=item $coro = new [$coderef [, @args]]	536	=back
49		537
50	Create a new coroutine and return it. The first C<transfer> call to this	538	=head1 STATIC METHODS
51	coroutine will start execution at the given coderef. If, the subroutine
52	returns it will be executed again.
53		539
54	If the coderef is omitted this function will create a new "empty"	540	Static methods are actually functions that implicitly operate on the
55	coroutine, i.e. a coroutine that cannot be transfered to but can be used	541	current coro.
56	to save the current coroutine in.	542
		543	=over 4
		544
		545	=item schedule
		546
		547	Calls the scheduler. The scheduler will find the next coro that is
		548	to be run from the ready queue and switches to it. The next coro
		549	to be run is simply the one with the highest priority that is longest
		550	in its ready queue. If there is no coro ready, it will call the
		551	C<$Coro::idle> hook.
		552
		553	Please note that the current coro will I<not> be put into the ready
		554	queue, so calling this function usually means you will never be called
		555	again unless something else (e.g. an event handler) calls C<< ->ready >>,
		556	thus waking you up.
		557
		558	This makes C<schedule> I<the> generic method to use to block the current
		559	coro and wait for events: first you remember the current coro in
		560	a variable, then arrange for some callback of yours to call C<< ->ready
		561	>> on that once some event happens, and last you call C<schedule> to put
		562	yourself to sleep. Note that a lot of things can wake your coro up,
		563	so you need to check whether the event indeed happened, e.g. by storing the
		564	status in a variable.
		565
		566	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
		567
		568	=item cede
		569
		570	"Cede" to other coros. This function puts the current coro into
		571	the ready queue and calls C<schedule>, which has the effect of giving
		572	up the current "timeslice" to other coros of the same or higher
		573	priority. Once your coro gets its turn again it will automatically be
		574	resumed.
		575
		576	This function is often called C<yield> in other languages.
		577
		578	=item Coro::cede_notself
		579
		580	Works like cede, but is not exported by default and will cede to I<any>
		581	coro, regardless of priority. This is useful sometimes to ensure
		582	progress is made.
		583
		584	=item terminate [arg...]
		585
		586	Terminates the current coro with the given status values (see
		587	L<cancel>). The values will not be copied, but referenced directly.
		588
		589	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
		590
		591	These function install enter and leave winders in the current scope. The
		592	enter block will be executed when on_enter is called and whenever the
		593	current coro is re-entered by the scheduler, while the leave block is
		594	executed whenever the current coro is blocked by the scheduler, and
		595	also when the containing scope is exited (by whatever means, be it exit,
		596	die, last etc.).
		597
		598	I<Neither invoking the scheduler, nor exceptions, are allowed within those
		599	BLOCKs>. That means: do not even think about calling C<die> without an
		600	eval, and do not even think of entering the scheduler in any way.
		601
		602	Since both BLOCKs are tied to the current scope, they will automatically
		603	be removed when the current scope exits.
		604
		605	These functions implement the same concept as C<dynamic-wind> in scheme
		606	does, and are useful when you want to localise some resource to a specific
		607	coro.
		608
		609	They slow down thread switching considerably for coros that use them
		610	(about 40% for a BLOCK with a single assignment, so thread switching is
		611	still reasonably fast if the handlers are fast).
		612
		613	These functions are best understood by an example: The following function
		614	will change the current timezone to "Antarctica/South_Pole", which
		615	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
		616	which remember/change the current timezone and restore the previous
		617	value, respectively, the timezone is only changed for the coro that
		618	installed those handlers.
		619
		620	use POSIX qw(tzset);
		621
		622	async {
		623	my $old_tz; # store outside TZ value here
		624
		625	Coro::on_enter {
		626	$old_tz = $ENV{TZ}; # remember the old value
		627
		628	$ENV{TZ} = "Antarctica/South_Pole";
		629	tzset; # enable new value
		630	};
		631
		632	Coro::on_leave {
		633	$ENV{TZ} = $old_tz;
		634	tzset; # restore old value
		635	};
		636
		637	# at this place, the timezone is Antarctica/South_Pole,
		638	# without disturbing the TZ of any other coro.
		639	};
		640
		641	This can be used to localise about any resource (locale, uid, current
		642	working directory etc.) to a block, despite the existance of other
		643	coros.
		644
		645	Another interesting example implements time-sliced multitasking using
		646	interval timers (this could obviously be optimised, but does the job):
		647
		648	# "timeslice" the given block
		649	sub timeslice(&) {
		650	use Time::HiRes ();
		651
		652	Coro::on_enter {
		653	# on entering the thread, we set an VTALRM handler to cede
		654	$SIG{VTALRM} = sub { cede };
		655	# and then start the interval timer
		656	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
		657	};
		658	Coro::on_leave {
		659	# on leaving the thread, we stop the interval timer again
		660	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
		661	};
		662
		663	&{+shift};
		664	}
		665
		666	# use like this:
		667	timeslice {
		668	# The following is an endless loop that would normally
		669	# monopolise the process. Since it runs in a timesliced
		670	# environment, it will regularly cede to other threads.
		671	while () { }
		672	};
		673
		674
		675	=item killall
		676
		677	Kills/terminates/cancels all coros except the currently running one.
		678
		679	Note that while this will try to free some of the main interpreter
		680	resources if the calling coro isn't the main coro, but one
		681	cannot free all of them, so if a coro that is not the main coro
		682	calls this function, there will be some one-time resource leak.
57		683
58	=cut	684	=cut
59		685
60	sub new {	686	sub killall {
61	my $class = $_[0];	687	for (Coro::State::list) {
62	my $proc = $_[1] || sub { die "tried to transfer to an empty coroutine" };	688	$_->cancel
63	bless _newprocess {	689	if $_ != $current && UNIVERSAL::isa $_, "Coro";
64	do {	690	}
65	eval { &$proc };
66	if ($@) {
67	$error_msg = $@;
68	$error_coro = _newprocess { };
69	&transfer($error_coro, $error);
70	}
71	} while (1);
72	}, $class;
73	}	691	}
74		692
75	=item $prev->transfer($next)	693	=back
76		694
77	Save the state of the current subroutine in $prev and switch to the	695	=head1 CORO OBJECT METHODS
78	coroutine saved in $next.	696
		697	These are the methods you can call on coro objects (or to create
		698	them).
		699
		700	=over 4
		701
		702	=item new Coro \&sub [, @args...]
		703
		704	Create a new coro and return it. When the sub returns, the coro
		705	automatically terminates as if C<terminate> with the returned values were
		706	called. To make the coro run you must first put it into the ready
		707	queue by calling the ready method.
		708
		709	See C<async> and C<Coro::State::new> for additional info about the
		710	coro environment.
79		711
80	=cut	712	=cut
81		713
82	# I call the _transfer function from a perl function	714	sub _coro_run {
83	# because that way perl saves all important things on	715	terminate &{+shift};
84	# the stack.	716	}
		717
		718	=item $success = $coro->ready
		719
		720	Put the given coro into the end of its ready queue (there is one
		721	queue for each priority) and return true. If the coro is already in
		722	the ready queue, do nothing and return false.
		723
		724	This ensures that the scheduler will resume this coro automatically
		725	once all the coro of higher priority and all coro of the same
		726	priority that were put into the ready queue earlier have been resumed.
		727
		728	=item $coro->suspend
		729
		730	Suspends the specified coro. A suspended coro works just like any other
		731	coro, except that the scheduler will not select a suspended coro for
		732	execution.
		733
		734	Suspending a coro can be useful when you want to keep the coro from
		735	running, but you don't want to destroy it, or when you want to temporarily
		736	freeze a coro (e.g. for debugging) to resume it later.
		737
		738	A scenario for the former would be to suspend all (other) coros after a
		739	fork and keep them alive, so their destructors aren't called, but new
		740	coros can be created.
		741
		742	=item $coro->resume
		743
		744	If the specified coro was suspended, it will be resumed. Note that when
		745	the coro was in the ready queue when it was suspended, it might have been
		746	unreadied by the scheduler, so an activation might have been lost.
		747
		748	To avoid this, it is best to put a suspended coro into the ready queue
		749	unconditionally, as every synchronisation mechanism must protect itself
		750	against spurious wakeups, and the one in the Coro family certainly do
		751	that.
		752
		753	=item $state->is_new
		754
		755	Returns true iff this Coro object is "new", i.e. has never been run
		756	yet. Those states basically consist of only the code reference to call and
		757	the arguments, but consumes very little other resources. New states will
		758	automatically get assigned a perl interpreter when they are transfered to.
		759
		760	=item $state->is_zombie
		761
		762	Returns true iff the Coro object has been cancelled, i.e.
		763	it's resources freed because they were C<cancel>'ed, C<terminate>'d,
		764	C<safe_cancel>'ed or simply went out of scope.
		765
		766	The name "zombie" stems from UNIX culture, where a process that has
		767	exited and only stores and exit status and no other resources is called a
		768	"zombie".
		769
		770	=item $is_ready = $coro->is_ready
		771
		772	Returns true iff the Coro object is in the ready queue. Unless the Coro
		773	object gets destroyed, it will eventually be scheduled by the scheduler.
		774
		775	=item $is_running = $coro->is_running
		776
		777	Returns true iff the Coro object is currently running. Only one Coro object
		778	can ever be in the running state (but it currently is possible to have
		779	multiple running Coro::States).
		780
		781	=item $is_suspended = $coro->is_suspended
		782
		783	Returns true iff this Coro object has been suspended. Suspended Coros will
		784	not ever be scheduled.
		785
		786	=item $coro->cancel (arg...)
		787
		788	Terminates the given Coro thread and makes it return the given arguments as
		789	status (default: an empty list). Never returns if the Coro is the
		790	current Coro.
		791
		792	This is a rather brutal way to free a coro, with some limitations - if
		793	the thread is inside a C callback that doesn't expect to be canceled,
		794	bad things can happen, or if the cancelled thread insists on running
		795	complicated cleanup handlers that rely on its thread context, things will
		796	not work.
		797
		798	Any cleanup code being run (e.g. from C<guard> blocks, destructors and so
		799	on) will be run without a thread context, and is not allowed to switch
		800	to other threads. A common mistake is to call C<< ->cancel >> from a
		801	destructor called by die'ing inside the thread to be cancelled for
		802	example.
		803
		804	On the plus side, C<< ->cancel >> will always clean up the thread, no
		805	matter what. If your cleanup code is complex or you want to avoid
		806	cancelling a C-thread that doesn't know how to clean up itself, it can be
		807	better to C<< ->throw >> an exception, or use C<< ->safe_cancel >>.
		808
		809	The arguments to C<< ->cancel >> are not copied, but instead will
		810	be referenced directly (e.g. if you pass C<$var> and after the call
		811	change that variable, then you might change the return values passed to
		812	e.g. C<join>, so don't do that).
		813
		814	The resources of the Coro are usually freed (or destructed) before this
		815	call returns, but this can be delayed for an indefinite amount of time, as
		816	in some cases the manager thread has to run first to actually destruct the
		817	Coro object.
		818
		819	=item $coro->safe_cancel ($arg...)
		820
		821	Works mostly like C<< ->cancel >>, but is inherently "safer", and
		822	consequently, can fail with an exception in cases the thread is not in a
		823	cancellable state. Essentially, C<< ->safe_cancel >> is a C<< ->cancel >>
		824	with extra checks before canceling.
		825
		826	It works a bit like throwing an exception that cannot be caught -
		827	specifically, it will clean up the thread from within itself, so all
		828	cleanup handlers (e.g. C<guard> blocks) are run with full thread
		829	context and can block if they wish. The downside is that there is no
		830	guarantee that the thread can be cancelled when you call this method, and
		831	therefore, it might fail. It is also considerably slower than C<cancel> or
		832	C<terminate>.
		833
		834	A thread is in a safe-cancellable state if it either hasn't been run yet,
		835	or it has no C context attached and is inside an SLF function.
		836
		837	The latter two basically mean that the thread isn't currently inside a
		838	perl callback called from some C function (usually via some XS modules)
		839	and isn't currently executing inside some C function itself (via Coro's XS
		840	API).
		841
		842	This call returns true when it could cancel the thread, or croaks with an
		843	error otherwise (i.e. it either returns true or doesn't return at all).
		844
		845	Why the weird interface? Well, there are two common models on how and
		846	when to cancel things. In the first, you have the expectation that your
		847	coro thread can be cancelled when you want to cancel it - if the thread
		848	isn't cancellable, this would be a bug somewhere, so C<< ->safe_cancel >>
		849	croaks to notify of the bug.
		850
		851	In the second model you sometimes want to ask nicely to cancel a thread,
		852	but if it's not a good time, well, then don't cancel. This can be done
		853	relatively easy like this:
		854
		855	if (! eval { $coro->safe_cancel }) {
		856	warn "unable to cancel thread: $@";
		857	}
		858
		859	However, what you never should do is first try to cancel "safely" and
		860	if that fails, cancel the "hard" way with C<< ->cancel >>. That makes
		861	no sense: either you rely on being able to execute cleanup code in your
		862	thread context, or you don't. If you do, then C<< ->safe_cancel >> is the
		863	only way, and if you don't, then C<< ->cancel >> is always faster and more
		864	direct.
		865
		866	=item $coro->schedule_to
		867
		868	Puts the current coro to sleep (like C<Coro::schedule>), but instead
		869	of continuing with the next coro from the ready queue, always switch to
		870	the given coro object (regardless of priority etc.). The readyness
		871	state of that coro isn't changed.
		872
		873	This is an advanced method for special cases - I'd love to hear about any
		874	uses for this one.
		875
		876	=item $coro->cede_to
		877
		878	Like C<schedule_to>, but puts the current coro into the ready
		879	queue. This has the effect of temporarily switching to the given
		880	coro, and continuing some time later.
		881
		882	This is an advanced method for special cases - I'd love to hear about any
		883	uses for this one.
		884
		885	=item $coro->throw ([$scalar])
		886
		887	If C<$throw> is specified and defined, it will be thrown as an exception
		888	inside the coro at the next convenient point in time. Otherwise
		889	clears the exception object.
		890
		891	Coro will check for the exception each time a schedule-like-function
		892	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		893	>>, C<< Coro::Handle->readable >> and so on. Most of those functions (all
		894	that are part of Coro itself) detect this case and return early in case an
		895	exception is pending.
		896
		897	The exception object will be thrown "as is" with the specified scalar in
		898	C<$@>, i.e. if it is a string, no line number or newline will be appended
		899	(unlike with C<die>).
		900
		901	This can be used as a softer means than either C<cancel> or C<safe_cancel
		902	>to ask a coro to end itself, although there is no guarantee that the
		903	exception will lead to termination, and if the exception isn't caught it
		904	might well end the whole program.
		905
		906	You might also think of C<throw> as being the moral equivalent of
		907	C<kill>ing a coro with a signal (in this case, a scalar).
		908
		909	=item $coro->join
		910
		911	Wait until the coro terminates and return any values given to the
		912	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		913	from multiple threads, and all will be resumed and given the status
		914	return once the C<$coro> terminates.
		915
		916	=item $coro->on_destroy (\&cb)
		917
		918	Registers a callback that is called when this coro thread gets destroyed,
		919	that is, after it's resources have been freed but before it is joined. The
		920	callback gets passed the terminate/cancel arguments, if any, and I<must
		921	not> die, under any circumstances.
		922
		923	There can be any number of C<on_destroy> callbacks per coro, and there is
		924	currently no way to remove a callback once added.
		925
		926	=item $oldprio = $coro->prio ($newprio)
		927
		928	Sets (or gets, if the argument is missing) the priority of the
		929	coro thread. Higher priority coro get run before lower priority
		930	coros. Priorities are small signed integers (currently -4 .. +3),
		931	that you can refer to using PRIO_xxx constants (use the import tag :prio
		932	to get then):
		933
		934	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		935	3 > 1 > 0 > -1 > -3 > -4
		936
		937	# set priority to HIGH
		938	current->prio (PRIO_HIGH);
		939
		940	The idle coro thread ($Coro::idle) always has a lower priority than any
		941	existing coro.
		942
		943	Changing the priority of the current coro will take effect immediately,
		944	but changing the priority of a coro in the ready queue (but not running)
		945	will only take effect after the next schedule (of that coro). This is a
		946	bug that will be fixed in some future version.
		947
		948	=item $newprio = $coro->nice ($change)
		949
		950	Similar to C<prio>, but subtract the given value from the priority (i.e.
		951	higher values mean lower priority, just as in UNIX's nice command).
		952
		953	=item $olddesc = $coro->desc ($newdesc)
		954
		955	Sets (or gets in case the argument is missing) the description for this
		956	coro thread. This is just a free-form string you can associate with a
		957	coro.
		958
		959	This method simply sets the C<< $coro->{desc} >> member to the given
		960	string. You can modify this member directly if you wish, and in fact, this
		961	is often preferred to indicate major processing states that can then be
		962	seen for example in a L<Coro::Debug> session:
		963
		964	sub my_long_function {
		965	local $Coro::current->{desc} = "now in my_long_function";
		966	...
		967	$Coro::current->{desc} = "my_long_function: phase 1";
		968	...
		969	$Coro::current->{desc} = "my_long_function: phase 2";
		970	...
		971	}
		972
		973	=cut
		974
		975	sub desc {
		976	my $old = $_[0]{desc};
		977	$_[0]{desc} = $_[1] if @_ > 1;
		978	$old;
		979	}
		980
85	sub transfer {	981	sub transfer {
86	_transfer($_[0], $_[1]);	982	require Carp;
		983	Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
87	}	984	}
88		985
89	=item $error, $error_msg, $error_coro	986	=back
90		987
91	This coroutine will be called on fatal errors. C<$error_msg> and	988	=head1 GLOBAL FUNCTIONS
92	C<$error_coro> return the error message and the error-causing coroutine	989
93	(NOT an object) respectively. This API might change.	990	=over 4
		991
		992	=item Coro::nready
		993
		994	Returns the number of coro that are currently in the ready state,
		995	i.e. that can be switched to by calling C<schedule> directory or
		996	indirectly. The value C<0> means that the only runnable coro is the
		997	currently running one, so C<cede> would have no effect, and C<schedule>
		998	would cause a deadlock unless there is an idle handler that wakes up some
		999	coro.
		1000
		1001	=item my $guard = Coro::guard { ... }
		1002
		1003	This function still exists, but is deprecated. Please use the
		1004	C<Guard::guard> function instead.
94		1005
95	=cut	1006	=cut
96		1007
97	$error_msg =	1008	BEGIN { *guard = \&Guard::guard }
98	$error_coro = undef;
99		1009
100	$error = _newprocess {	1010	=item unblock_sub { ... }
101	print STDERR "FATAL: $error_msg\nprogram aborted\n";	1011
102	exit 50;	1012	This utility function takes a BLOCK or code reference and "unblocks" it,
		1013	returning a new coderef. Unblocking means that calling the new coderef
		1014	will return immediately without blocking, returning nothing, while the
		1015	original code ref will be called (with parameters) from within another
		1016	coro.
		1017
		1018	The reason this function exists is that many event libraries (such as
		1019	the venerable L<Event|Event> module) are not thread-safe (a weaker form
		1020	of reentrancy). This means you must not block within event callbacks,
		1021	otherwise you might suffer from crashes or worse. The only event library
		1022	currently known that is safe to use without C<unblock_sub> is L<EV> (but
		1023	you might still run into deadlocks if all event loops are blocked).
		1024
		1025	Coro will try to catch you when you block in the event loop
		1026	("FATAL: $Coro::idle blocked itself"), but this is just best effort and
		1027	only works when you do not run your own event loop.
		1028
		1029	This function allows your callbacks to block by executing them in another
		1030	coro where it is safe to block. One example where blocking is handy
		1031	is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
		1032	disk, for example.
		1033
		1034	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		1035	creating event callbacks that want to block.
		1036
		1037	If your handler does not plan to block (e.g. simply sends a message to
		1038	another coro, or puts some other coro into the ready queue), there is
		1039	no reason to use C<unblock_sub>.
		1040
		1041	Note that you also need to use C<unblock_sub> for any other callbacks that
		1042	are indirectly executed by any C-based event loop. For example, when you
		1043	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		1044	provides callbacks that are the result of some event callback, then you
		1045	must not block either, or use C<unblock_sub>.
		1046
		1047	=cut
		1048
		1049	our @unblock_queue;
		1050
		1051	# we create a special coro because we want to cede,
		1052	# to reduce pressure on the coro pool (because most callbacks
		1053	# return immediately and can be reused) and because we cannot cede
		1054	# inside an event callback.
		1055	our $unblock_scheduler = new Coro sub {
		1056	while () {
		1057	while (my $cb = pop @unblock_queue) {
		1058	&async_pool (@$cb);
		1059
		1060	# for short-lived callbacks, this reduces pressure on the coro pool
		1061	# as the chance is very high that the async_poll coro will be back
		1062	# in the idle state when cede returns
		1063	cede;
		1064	}
		1065	schedule; # sleep well
		1066	}
103	};	1067	};
		1068	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
		1069
		1070	sub unblock_sub(&) {
		1071	my $cb = shift;
		1072
		1073	sub {
		1074	unshift @unblock_queue, [$cb, @_];
		1075	$unblock_scheduler->ready;
		1076	}
		1077	}
		1078
		1079	=item $cb = rouse_cb
		1080
		1081	Create and return a "rouse callback". That's a code reference that,
		1082	when called, will remember a copy of its arguments and notify the owner
		1083	coro of the callback.
		1084
		1085	See the next function.
		1086
		1087	=item @args = rouse_wait [$cb]
		1088
		1089	Wait for the specified rouse callback (or the last one that was created in
		1090	this coro).
		1091
		1092	As soon as the callback is invoked (or when the callback was invoked
		1093	before C<rouse_wait>), it will return the arguments originally passed to
		1094	the rouse callback. In scalar context, that means you get the I<last>
		1095	argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
		1096	statement at the end.
		1097
		1098	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		1099
		1100	=back
		1101
		1102	=cut
		1103
		1104	for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) {
		1105	my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"};
		1106
		1107	*{"Coro::$module\::new"} = sub {
		1108	require "Coro/$module.pm";
		1109
		1110	# some modules have their new predefined in State.xs, some don't
		1111	*{"Coro::$module\::new"} = $old
		1112	if $old;
		1113
		1114	goto &{"Coro::$module\::new"};
		1115	};
		1116	}
104		1117
105	1;	1118	1;
106		1119
		1120	=head1 HOW TO WAIT FOR A CALLBACK
		1121
		1122	It is very common for a coro to wait for some callback to be
		1123	called. This occurs naturally when you use coro in an otherwise
		1124	event-based program, or when you use event-based libraries.
		1125
		1126	These typically register a callback for some event, and call that callback
		1127	when the event occured. In a coro, however, you typically want to
		1128	just wait for the event, simplyifying things.
		1129
		1130	For example C<< AnyEvent->child >> registers a callback to be called when
		1131	a specific child has exited:
		1132
		1133	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		1134
		1135	But from within a coro, you often just want to write this:
		1136
		1137	my $status = wait_for_child $pid;
		1138
		1139	Coro offers two functions specifically designed to make this easy,
		1140	C<rouse_cb> and C<rouse_wait>.
		1141
		1142	The first function, C<rouse_cb>, generates and returns a callback that,
		1143	when invoked, will save its arguments and notify the coro that
		1144	created the callback.
		1145
		1146	The second function, C<rouse_wait>, waits for the callback to be called
		1147	(by calling C<schedule> to go to sleep) and returns the arguments
		1148	originally passed to the callback.
		1149
		1150	Using these functions, it becomes easy to write the C<wait_for_child>
		1151	function mentioned above:
		1152
		1153	sub wait_for_child($) {
		1154	my ($pid) = @_;
		1155
		1156	my $watcher = AnyEvent->child (pid => $pid, cb => rouse_cb);
		1157
		1158	my ($rpid, $rstatus) = rouse_wait;
		1159	$rstatus
		1160	}
		1161
		1162	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		1163	you can roll your own, using C<schedule> and C<ready>:
		1164
		1165	sub wait_for_child($) {
		1166	my ($pid) = @_;
		1167
		1168	# store the current coro in $current,
		1169	# and provide result variables for the closure passed to ->child
		1170	my $current = $Coro::current;
		1171	my ($done, $rstatus);
		1172
		1173	# pass a closure to ->child
		1174	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		1175	$rstatus = $_[1]; # remember rstatus
		1176	$done = 1; # mark $rstatus as valid
		1177	$current->ready; # wake up the waiting thread
		1178	});
		1179
		1180	# wait until the closure has been called
		1181	schedule while !$done;
		1182
		1183	$rstatus
		1184	}
		1185
		1186
		1187	=head1 BUGS/LIMITATIONS
		1188
		1189	=over 4
		1190
		1191	=item fork with pthread backend
		1192
		1193	When Coro is compiled using the pthread backend (which isn't recommended
		1194	but required on many BSDs as their libcs are completely broken), then
		1195	coro will not survive a fork. There is no known workaround except to
		1196	fix your libc and use a saner backend.
		1197
		1198	=item perl process emulation ("threads")
		1199
		1200	This module is not perl-pseudo-thread-safe. You should only ever use this
		1201	module from the first thread (this requirement might be removed in the
		1202	future to allow per-thread schedulers, but Coro::State does not yet allow
		1203	this). I recommend disabling thread support and using processes, as having
		1204	the windows process emulation enabled under unix roughly halves perl
		1205	performance, even when not used.
		1206
		1207	Attempts to use threads created in another emulated process will crash
		1208	("cleanly", with a null pointer exception).
		1209
		1210	=item coro switching is not signal safe
		1211
		1212	You must not switch to another coro from within a signal handler (only
		1213	relevant with %SIG - most event libraries provide safe signals), I<unless>
		1214	you are sure you are not interrupting a Coro function.
		1215
		1216	That means you I<MUST NOT> call any function that might "block" the
		1217	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		1218	anything that calls those. Everything else, including calling C<ready>,
		1219	works.
		1220
107	=back	1221	=back
108		1222
109	=head1 BUGS
110		1223
111	This module has not yet been extensively tested.	1224	=head1 WINDOWS PROCESS EMULATION
		1225
		1226	A great many people seem to be confused about ithreads (for example, Chip
		1227	Salzenberg called me unintelligent, incapable, stupid and gullible,
		1228	while in the same mail making rather confused statements about perl
		1229	ithreads (for example, that memory or files would be shared), showing his
		1230	lack of understanding of this area - if it is hard to understand for Chip,
		1231	it is probably not obvious to everybody).
		1232
		1233	What follows is an ultra-condensed version of my talk about threads in
		1234	scripting languages given on the perl workshop 2009:
		1235
		1236	The so-called "ithreads" were originally implemented for two reasons:
		1237	first, to (badly) emulate unix processes on native win32 perls, and
		1238	secondly, to replace the older, real thread model ("5.005-threads").
		1239
		1240	It does that by using threads instead of OS processes. The difference
		1241	between processes and threads is that threads share memory (and other
		1242	state, such as files) between threads within a single process, while
		1243	processes do not share anything (at least not semantically). That
		1244	means that modifications done by one thread are seen by others, while
		1245	modifications by one process are not seen by other processes.
		1246
		1247	The "ithreads" work exactly like that: when creating a new ithreads
		1248	process, all state is copied (memory is copied physically, files and code
		1249	is copied logically). Afterwards, it isolates all modifications. On UNIX,
		1250	the same behaviour can be achieved by using operating system processes,
		1251	except that UNIX typically uses hardware built into the system to do this
		1252	efficiently, while the windows process emulation emulates this hardware in
		1253	software (rather efficiently, but of course it is still much slower than
		1254	dedicated hardware).
		1255
		1256	As mentioned before, loading code, modifying code, modifying data
		1257	structures and so on is only visible in the ithreads process doing the
		1258	modification, not in other ithread processes within the same OS process.
		1259
		1260	This is why "ithreads" do not implement threads for perl at all, only
		1261	processes. What makes it so bad is that on non-windows platforms, you can
		1262	actually take advantage of custom hardware for this purpose (as evidenced
		1263	by the forks module, which gives you the (i-) threads API, just much
		1264	faster).
		1265
		1266	Sharing data is in the i-threads model is done by transfering data
		1267	structures between threads using copying semantics, which is very slow -
		1268	shared data simply does not exist. Benchmarks using i-threads which are
		1269	communication-intensive show extremely bad behaviour with i-threads (in
		1270	fact, so bad that Coro, which cannot take direct advantage of multiple
		1271	CPUs, is often orders of magnitude faster because it shares data using
		1272	real threads, refer to my talk for details).
		1273
		1274	As summary, i-threads *use* threads to implement processes, while
		1275	the compatible forks module *uses* processes to emulate, uhm,
		1276	processes. I-threads slow down every perl program when enabled, and
		1277	outside of windows, serve no (or little) practical purpose, but
		1278	disadvantages every single-threaded Perl program.
		1279
		1280	This is the reason that I try to avoid the name "ithreads", as it is
		1281	misleading as it implies that it implements some kind of thread model for
		1282	perl, and prefer the name "windows process emulation", which describes the
		1283	actual use and behaviour of it much better.
112		1284
113	=head1 SEE ALSO	1285	=head1 SEE ALSO
114		1286
115	L<Coro::Process>, L<Coro::Signal>.	1287	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
116		1288
117	=head1 AUTHOR	1289	Debugging: L<Coro::Debug>.
118		1290
119	Marc Lehmann <pcg@goof.com>	1291	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
120	http://www.goof.com/pcg/marc/	1292
		1293	Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
		1294	L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		1295
		1296	I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
		1297
		1298	Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
		1299	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
		1300	L<Coro::Select>.
		1301
		1302	XS API: L<Coro::MakeMaker>.
		1303
		1304	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
		1305
		1306	=head1 AUTHOR/SUPPORT/CONTACT
		1307
		1308	Marc A. Lehmann <schmorp@schmorp.de>
		1309	http://software.schmorp.de/pkg/Coro.html
121		1310
122	=cut	1311	=cut
123		1312

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