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

Comparing Coro/Coro.pm (file contents):
Revision 1.233 by root, Fri Nov 21 06:02:07 2008 UTC vs.
Revision 1.294 by root, Fri May 6 21:15:17 2011 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	Coro - coroutine process abstraction	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
11	print "2\n";	11	print "2\n";
12	cede; # yield back to main	12	cede; # yield back to main
13	print "4\n";	13	print "4\n";
14	};	14	};
15	print "1\n";	15	print "1\n";
16	cede; # yield to coroutine	16	cede; # yield to coro
17	print "3\n";	17	print "3\n";
18	cede; # and again	18	cede; # and again
19		19
20	# use locking	20	# use locking
21	use Coro::Semaphore;	21	use Coro::Semaphore;
…		…
26	$locked = 1;	26	$locked = 1;
27	$lock->up;	27	$lock->up;
28		28
29	=head1 DESCRIPTION	29	=head1 DESCRIPTION
30		30
31	This module collection manages coroutines. Coroutines are similar to	31	For a tutorial-style introduction, please read the L<Coro::Intro>
32	threads but don't (in general) run in parallel at the same time even	32	manpage. This manpage mainly contains reference information.
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		33
39	Unlike a normal perl program, however, coroutines allow you to have	34	This module collection manages continuations in general, most often in
40	multiple running interpreters that share data, which is especially useful	35	the form of cooperative threads (also called coros, or simply "coro"
41	to code pseudo-parallel processes and for event-based programming, such as	36	in the documentation). They are similar to kernel threads but don't (in
42	multiple HTTP-GET requests running concurrently. See L<Coro::AnyEvent> to	37	general) run in parallel at the same time even on SMP machines. The
43	learn more.	38	specific flavor of thread offered by this module also guarantees you that
		39	it will not switch between threads unless necessary, at easily-identified
		40	points in your program, so locking and parallel access are rarely an
		41	issue, making thread programming much safer and easier than using other
		42	thread models.
44		43
45	Coroutines are also useful because Perl has no support for threads (the so	44	Unlike the so-called "Perl threads" (which are not actually real threads
46	called "threads" that perl offers are nothing more than the (bad) process	45	but only the windows process emulation (see section of same name for
47	emulation coming from the Windows platform: On standard operating systems	46	more details) ported to UNIX, and as such act as processes), Coro
48	they serve no purpose whatsoever, except by making your programs slow and	47	provides a full shared address space, which makes communication between
49	making them use a lot of memory. Best disable them when building perl, or	48	threads very easy. And coro threads are fast, too: disabling the Windows
50	aks your software vendor/distributor to do it for you).	49	process emulation code in your perl and using Coro can easily result in
		50	a two to four times speed increase for your programs. A parallel matrix
		51	multiplication benchmark (very communication-intensive) runs over 300
		52	times faster on a single core than perls pseudo-threads on a quad core
		53	using all four cores.
51		54
		55	Coro achieves that by supporting multiple running interpreters that share
		56	data, which is especially useful to code pseudo-parallel processes and
		57	for event-based programming, such as multiple HTTP-GET requests running
		58	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
		59	into an event-based environment.
		60
52	In this module, coroutines are defined as "callchain + lexical variables +	61	In this module, a thread is defined as "callchain + lexical variables +
53	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,	62	some package variables + C stack), that is, a thread has its own callchain,
54	its own set of lexicals and its own set of perls most important global	63	its own set of lexicals and its own set of perls most important global
55	variables (see L<Coro::State> for more configuration).	64	variables (see L<Coro::State> for more configuration and background info).
		65
		66	See also the C<SEE ALSO> section at the end of this document - the Coro
		67	module family is quite large.
		68
		69	=head1 CORO THREAD LIFE CYCLE
		70
		71	During the long and exciting (or not) life of a coro thread, it goes
		72	through a number of states:
		73
		74	=over 4
		75
		76	=item 1. Creation
		77
		78	The first thing in the life of a coro thread is it's creation -
		79	obviously. The typical way to create a thread is to call the C<async
		80	BLOCK> function:
		81
		82	async {
		83	# thread code goes here
		84	};
		85
		86	You can also pass arguments, which are put in C<@_>:
		87
		88	async {
		89	print $_[1]; # prints 2
		90	} 1, 2, 3;
		91
		92	This creates a new coro thread and puts it into the ready queue, meaning
		93	it will run as soon as the CPU is free for it.
		94
		95	C<async> will return a coro object - you can store this for future
		96	reference or ignore it, the thread itself will keep a reference to it's
		97	thread object - threads are alive on their own.
		98
		99	Another way to create a thread is to call the C<new> constructor with a
		100	code-reference:
		101
		102	new Coro sub {
		103	# thread code goes here
		104	}, @optional_arguments;
		105
		106	This is quite similar to calling C<async>, but the important difference is
		107	that the new thread is not put into the ready queue, so the thread will
		108	not run until somebody puts it there. C<async> is, therefore, identical to
		109	this sequence:
		110
		111	my $coro = new Coro sub {
		112	# thread code goes here
		113	};
		114	$coro->ready;
		115	return $coro;
		116
		117	=item 2. Startup
		118
		119	When a new coro thread is created, only a copy of the code reference
		120	and the arguments are stored, no extra memory for stacks and so on is
		121	allocated, keeping the coro thread in a low-memory state.
		122
		123	Only when it actually starts executing will all the resources be finally
		124	allocated.
		125
		126	The optional arguments specified at coro creation are available in C<@_>,
		127	similar to function calls.
		128
		129	=item 3. Running / Blocking
		130
		131	A lot can happen after the coro thread has started running. Quite usually,
		132	it will not run to the end in one go (because you could use a function
		133	instead), but it will give up the CPU regularly because it waits for
		134	external events.
		135
		136	As long as a coro thread runs, it's coro object is available in the global
		137	variable C<$Coro::current>.
		138
		139	The low-level way to give up the CPU is to call the scheduler, which
		140	selects a new coro thread to run:
		141
		142	Coro::schedule;
		143
		144	Since running threads are not in the ready queue, calling the scheduler
		145	without doing anything else will block the coro thread forever - you need
		146	to arrange either for the coro to put woken up (readied) by some other
		147	event or some other thread, or you can put it into the ready queue before
		148	scheduling:
		149
		150	# this is exactly what Coro::cede does
		151	$Coro::current->ready;
		152	Coro::schedule;
		153
		154	All the higher-level synchronisation methods (Coro::Semaphore,
		155	Coro::rouse_*...) are actually implemented via C<< ->ready >> and C<<
		156	Coro::schedule >>.
		157
		158	While the coro thread is running it also might get assigned a C-level
		159	thread, or the C-level thread might be unassigned from it, as the Coro
		160	runtime wishes. A C-level thread needs to be assigned when your perl
		161	thread calls into some C-level function and that function in turn calls
		162	perl and perl then wants to switch coroutines. This happens most often
		163	when you run an event loop and block in the callback, or when perl
		164	itself calls some function such as C<AUTOLOAD> or methods via the C<tie>
		165	mechanism.
		166
		167	=item 4. Termination
		168
		169	Many threads actually terminate after some time. There are a number of
		170	ways to terminate a coro thread, the simplest is returning from the
		171	top-level code reference:
		172
		173	async {
		174	# after returning from here, the coro thread is terminated
		175	};
		176
		177	async {
		178	return if 0.5 < rand; # terminate a little earlier, maybe
		179	print "got a chance to print this\n";
		180	# or here
		181	};
		182
		183	Any values returned from the coroutine can be recovered using C<< ->join
		184	>>:
		185
		186	my $coro = async {
		187	"hello, world\n" # return a string
		188	};
		189
		190	my $hello_world = $coro->join;
		191
		192	print $hello_world;
		193
		194	Another way to terminate is to call C<< Coro::terminate >>, which at any
		195	subroutine call nesting level:
		196
		197	async {
		198	Coro::terminate "return value 1", "return value 2";
		199	};
		200
		201	And yet another way is to C<< ->cancel >> (or C<< ->safe_cancel >>) the
		202	coro thread from another thread:
		203
		204	my $coro = async {
		205	exit 1;
		206	};
		207
		208	$coro->cancel; # an also accept values for ->join to retrieve
		209
		210	Cancellation I<can> be dangerous - it's a bit like calling C<exit>
		211	without actually exiting, and might leave C libraries and XS modules in
		212	a weird state. Unlike other thread implementations, however, Coro is
		213	exceptionally safe with regards to cancellation, as perl will always be
		214	in a consistent state, and for those cases where you want to do truly
		215	marvellous things with your coro while it is being cancelled, there is
		216	even a 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	=item 5. Cleanup
		224
		225	Threads will allocate various resources. Most but not all will be returned
		226	when a thread terminates, during clean-up.
		227
		228	Cleanup is quite similar to throwing an uncaught exception: perl will
		229	work it's way up through all subroutine calls and blocks. On it's way, it
		230	will release all C<my> variables, undo all C<local>'s and free any other
		231	resources truly local to the thread.
		232
		233	So, a common way to free resources is to keep them referenced only by my
		234	variables:
		235
		236	async {
		237	my $big_cache = new Cache ...;
		238	};
		239
		240	If there are no other references, then the C<$big_cache> object will be
		241	freed when the thread terminates, regardless of how it does so.
		242
		243	What it does C<NOT> do is unlock any Coro::Semaphores or similar
		244	resources, but that's where the C<guard> methods come in handy:
		245
		246	my $sem = new Coro::Semaphore;
		247
		248	async {
		249	my $lock_guard = $sem->guard;
		250	# if we reutrn, or die or get cancelled, here,
		251	# then the semaphore will be "up"ed.
		252	};
		253
		254	The C<Guard::guard> function comes in handy for any custom cleanup you
		255	might want to do:
		256
		257	async {
		258	my $window = new Gtk2::Window "toplevel";
		259	# The window will not be cleaned up automatically, even when $window
		260	# gets freed, so use a guard to ensure it's destruction
		261	# in case of an error:
		262	my $window_guard = Guard::guard { $window->destroy };
		263
		264	# we are safe here
		265	};
		266
		267	Last not least, C<local> can often be handy, too, e.g. when temporarily
		268	replacing the coro thread description:
		269
		270	sub myfunction {
		271	local $Coro::current->{desc} = "inside myfunction(@_)";
		272
		273	# if we return or die here, the description will be restored
		274	}
		275
		276	=item 6. Viva La Zombie Muerte
		277
		278	Even after a thread has terminated and cleaned up it's resources, the coro
		279	object still is there and stores the return values of the thread. Only in
		280	this state will the coro object be "reference counted" in the normal perl
		281	sense: the thread code keeps a reference to it when it is active, but not
		282	after it has terminated.
		283
		284	The means the coro object gets freed automatically when the thread has
		285	terminated and cleaned up and there arenot other references.
		286
		287	If there are, the coro object will stay around, and you can call C<<
		288	->join >> as many times as you wish to retrieve the result values:
		289
		290	async {
		291	print "hi\n";
		292	1
		293	};
		294
		295	# run the async above, and free everything before returning
		296	# from Coro::cede:
		297	Coro::cede;
		298
		299	{
		300	my $coro = async {
		301	print "hi\n";
		302	1
		303	};
		304
		305	# run the async above, and clean up, but do not free the coro
		306	# object:
		307	Coro::cede;
		308
		309	# optionally retrieve the result values
		310	my @results = $coro->join;
		311
		312	# now $coro goes out of scope, and presumably gets freed
		313	};
		314
		315	=back
56		316
57	=cut	317	=cut
58		318
59	package Coro;	319	package Coro;
60		320
61	use strict qw(vars subs);	321	use common::sense;
62	no warnings "uninitialized";	322
		323	use Carp ();
		324
		325	use Guard ();
63		326
64	use Coro::State;	327	use Coro::State;
65		328
66	use base qw(Coro::State Exporter);	329	use base qw(Coro::State Exporter);
67		330
68	our $idle; # idle handler	331	our $idle; # idle handler
69	our $main; # main coroutine	332	our $main; # main coro
70	our $current; # current coroutine	333	our $current; # current coro
71		334
72	our $VERSION = "5.0";	335	our $VERSION = 5.372;
73		336
74	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	337	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
75	our %EXPORT_TAGS = (	338	our %EXPORT_TAGS = (
76	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	339	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
77	);	340	);
78	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	341	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
79		342
		343	=head1 GLOBAL VARIABLES
		344
80	=over 4	345	=over 4
81		346
82	=item $Coro::main	347	=item $Coro::main
83		348
84	This variable stores the coroutine object that represents the main	349	This variable stores the Coro object that represents the main
85	program. While you cna C<ready> it and do most other things you can do to	350	program. While you cna C<ready> it and do most other things you can do to
86	coroutines, it is mainly useful to compare again C<$Coro::current>, to see	351	coro, it is mainly useful to compare again C<$Coro::current>, to see
87	whether you are running in the main program or not.	352	whether you are running in the main program or not.
88		353
89	=cut	354	=cut
90		355
91	# $main is now being initialised by Coro::State	356	# $main is now being initialised by Coro::State
92		357
93	=item $Coro::current	358	=item $Coro::current
94		359
95	The coroutine object representing the current coroutine (the last	360	The Coro object representing the current coro (the last
96	coroutine that the Coro scheduler switched to). The initial value is	361	coro that the Coro scheduler switched to). The initial value is
97	C<$Coro::main> (of course).	362	C<$Coro::main> (of course).
98		363
99	This variable is B<strictly> I<read-only>. You can take copies of the	364	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	365	value stored in it and use it as any other Coro object, but you must
101	not otherwise modify the variable itself.	366	not otherwise modify the variable itself.
102		367
103	=cut	368	=cut
104		369
105	sub current() { $current } # [DEPRECATED]	370	sub current() { $current } # [DEPRECATED]
106		371
107	=item $Coro::idle	372	=item $Coro::idle
108		373
109	This variable is mainly useful to integrate Coro into event loops. It is	374	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	375	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
111	pretty low-level functionality.	376	pretty low-level functionality.
112		377
113	This variable stores a callback that is called whenever the scheduler	378	This variable stores a Coro object that is put into the ready queue when
114	finds no ready coroutines to run. The default implementation prints	379	there are no other ready threads (without invoking any ready hooks).
115	"FATAL: deadlock detected" and exits, because the program has no other way
116	to continue.
117		380
		381	The default implementation dies with "FATAL: deadlock detected.", followed
		382	by a thread listing, because the program has no other way to continue.
		383
118	This hook is overwritten by modules such as C<Coro::Timer> and	384	This hook is overwritten by modules such as C<Coro::EV> and
119	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a	385	C<Coro::AnyEvent> to wait on an external event that hopefully wakes up a
120	coroutine so the scheduler can run it.	386	coro so the scheduler can run it.
121		387
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	388	See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
128	technique.
129		389
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	390	=cut
134		391
135	$idle = sub {	392	# \|\|= because other modules could have provided their own by now
136	require Carp;	393	$idle \|\|= new Coro sub {
137	Carp::croak ("FATAL: deadlock detected");	394	require Coro::Debug;
		395	die "FATAL: deadlock detected.\n"
		396	. Coro::Debug::ps_listing ();
138	};	397	};
139		398
140	# this coroutine is necessary because a coroutine	399	# this coro is necessary because a coro
141	# cannot destroy itself.	400	# cannot destroy itself.
142	our @destroy;	401	our @destroy;
143	our $manager;	402	our $manager;
144		403
145	$manager = new Coro sub {	404	$manager = new Coro sub {
146	while () {	405	while () {
147	Coro::_cancel shift @destroy	406	_destroy shift @destroy
148	while @destroy;	407	while @destroy;
149		408
150	&schedule;	409	&schedule;
151	}	410	}
152	};	411	};
153	$manager->{desc} = "[coro manager]";	412	$manager->{desc} = "[coro manager]";
154	$manager->prio (PRIO_MAX);	413	$manager->prio (PRIO_MAX);
155		414
156	=back	415	=back
157		416
158	=head2 SIMPLE COROUTINE CREATION	417	=head1 SIMPLE CORO CREATION
159		418
160	=over 4	419	=over 4
161		420
162	=item async { ... } [@args...]	421	=item async { ... } [@args...]
163		422
164	Create a new coroutine and return it's coroutine object (usually	423	Create a new coro and return its Coro object (usually
165	unused). The coroutine will be put into the ready queue, so	424	unused). The coro will be put into the ready queue, so
166	it will start running automatically on the next scheduler run.	425	it will start running automatically on the next scheduler run.
167		426
168	The first argument is a codeblock/closure that should be executed in the	427	The first argument is a codeblock/closure that should be executed in the
169	coroutine. When it returns argument returns the coroutine is automatically	428	coro. When it returns argument returns the coro is automatically
170	terminated.	429	terminated.
171		430
172	The remaining arguments are passed as arguments to the closure.	431	The remaining arguments are passed as arguments to the closure.
173		432
174	See the C<Coro::State::new> constructor for info about the coroutine	433	See the C<Coro::State::new> constructor for info about the coro
175	environment in which coroutines are executed.	434	environment in which coro are executed.
176		435
177	Calling C<exit> in a coroutine will do the same as calling exit outside	436	Calling C<exit> in a coro will do the same as calling exit outside
178	the coroutine. Likewise, when the coroutine dies, the program will exit,	437	the coro. Likewise, when the coro dies, the program will exit,
179	just as it would in the main program.	438	just as it would in the main program.
180		439
181	If you do not want that, you can provide a default C<die> handler, or	440	If you do not want that, you can provide a default C<die> handler, or
182	simply avoid dieing (by use of C<eval>).	441	simply avoid dieing (by use of C<eval>).
183		442
184	Example: Create a new coroutine that just prints its arguments.	443	Example: Create a new coro that just prints its arguments.
185		444
186	async {	445	async {
187	print "@_\n";	446	print "@_\n";
188	} 1,2,3,4;	447	} 1,2,3,4;
189		448
190	=cut
191
192	sub async(&@) {
193	my $coro = new Coro @_;
194	$coro->ready;
195	$coro
196	}
197
198	=item async_pool { ... } [@args...]	449	=item async_pool { ... } [@args...]
199		450
200	Similar to C<async>, but uses a coroutine pool, so you should not call	451	Similar to C<async>, but uses a coro pool, so you should not call
201	terminate or join on it (although you are allowed to), and you get a	452	terminate or join on it (although you are allowed to), and you get a
202	coroutine that might have executed other code already (which can be good	453	coro that might have executed other code already (which can be good
203	or bad :).	454	or bad :).
204		455
205	On the plus side, this function is about twice as fast as creating (and	456	On the plus side, this function is about twice as fast as creating (and
206	destroying) a completely new coroutine, so if you need a lot of generic	457	destroying) a completely new coro, so if you need a lot of generic
207	coroutines in quick successsion, use C<async_pool>, not C<async>.	458	coros in quick successsion, use C<async_pool>, not C<async>.
208		459
209	The code block is executed in an C<eval> context and a warning will be	460	The code block is executed in an C<eval> context and a warning will be
210	issued in case of an exception instead of terminating the program, as	461	issued in case of an exception instead of terminating the program, as
211	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>	462	C<async> does. As the coro is being reused, stuff like C<on_destroy>
212	will not work in the expected way, unless you call terminate or cancel,	463	will not work in the expected way, unless you call terminate or cancel,
213	which somehow defeats the purpose of pooling (but is fine in the	464	which somehow defeats the purpose of pooling (but is fine in the
214	exceptional case).	465	exceptional case).
215		466
216	The priority will be reset to C<0> after each run, tracing will be	467	The priority will be reset to C<0> after each run, tracing will be
217	disabled, the description will be reset and the default output filehandle	468	disabled, the description will be reset and the default output filehandle
218	gets restored, so you can change all these. Otherwise the coroutine will	469	gets restored, so you can change all these. Otherwise the coro will
219	be re-used "as-is": most notably if you change other per-coroutine global	470	be re-used "as-is": most notably if you change other per-coro global
220	stuff such as C<$/> you I<must needs> revert that change, which is most	471	stuff such as C<$/> you I<must needs> revert that change, which is most
221	simply done by using local as in: C<< local $/ >>.	472	simply done by using local as in: C<< local $/ >>.
222		473
223	The idle pool size is limited to C<8> idle coroutines (this can be	474	The idle pool size is limited to C<8> idle coros (this can be
224	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle	475	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
225	coros as required.	476	coros as required.
226		477
227	If you are concerned about pooled coroutines growing a lot because a	478	If you are concerned about pooled coros growing a lot because a
228	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool	479	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
229	{ terminate }> once per second or so to slowly replenish the pool. In	480	{ terminate }> once per second or so to slowly replenish the pool. In
230	addition to that, when the stacks used by a handler grows larger than 32kb	481	addition to that, when the stacks used by a handler grows larger than 32kb
231	(adjustable via $Coro::POOL_RSS) it will also be destroyed.	482	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
232		483
…		…
246	}	497	}
247	}	498	}
248		499
249	=back	500	=back
250		501
251	=head2 STATIC METHODS	502	=head1 STATIC METHODS
252		503
253	Static methods are actually functions that operate on the current coroutine.	504	Static methods are actually functions that implicitly operate on the
		505	current coro.
254		506
255	=over 4	507	=over 4
256		508
257	=item schedule	509	=item schedule
258		510
259	Calls the scheduler. The scheduler will find the next coroutine that is	511	Calls the scheduler. The scheduler will find the next coro that is
260	to be run from the ready queue and switches to it. The next coroutine	512	to be run from the ready queue and switches to it. The next coro
261	to be run is simply the one with the highest priority that is longest	513	to be run is simply the one with the highest priority that is longest
262	in its ready queue. If there is no coroutine ready, it will clal the	514	in its ready queue. If there is no coro ready, it will call the
263	C<$Coro::idle> hook.	515	C<$Coro::idle> hook.
264		516
265	Please note that the current coroutine will I<not> be put into the ready	517	Please note that the current coro will I<not> be put into the ready
266	queue, so calling this function usually means you will never be called	518	queue, so calling this function usually means you will never be called
267	again unless something else (e.g. an event handler) calls C<< ->ready >>,	519	again unless something else (e.g. an event handler) calls C<< ->ready >>,
268	thus waking you up.	520	thus waking you up.
269		521
270	This makes C<schedule> I<the> generic method to use to block the current	522	This makes C<schedule> I<the> generic method to use to block the current
271	coroutine and wait for events: first you remember the current coroutine in	523	coro and wait for events: first you remember the current coro in
272	a variable, then arrange for some callback of yours to call C<< ->ready	524	a variable, then arrange for some callback of yours to call C<< ->ready
273	>> on that once some event happens, and last you call C<schedule> to put	525	>> on that once some event happens, and last you call C<schedule> to put
274	yourself to sleep. Note that a lot of things can wake your coroutine up,	526	yourself to sleep. Note that a lot of things can wake your coro up,
275	so you need to check whether the event indeed happened, e.g. by storing the	527	so you need to check whether the event indeed happened, e.g. by storing the
276	status in a variable.	528	status in a variable.
277		529
278	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.	530	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
279		531
280	=item cede	532	=item cede
281		533
282	"Cede" to other coroutines. This function puts the current coroutine into	534	"Cede" to other coros. This function puts the current coro into
283	the ready queue and calls C<schedule>, which has the effect of giving	535	the ready queue and calls C<schedule>, which has the effect of giving
284	up the current "timeslice" to other coroutines of the same or higher	536	up the current "timeslice" to other coros of the same or higher
285	priority. Once your coroutine gets its turn again it will automatically be	537	priority. Once your coro gets its turn again it will automatically be
286	resumed.	538	resumed.
287		539
288	This function is often called C<yield> in other languages.	540	This function is often called C<yield> in other languages.
289		541
290	=item Coro::cede_notself	542	=item Coro::cede_notself
291		543
292	Works like cede, but is not exported by default and will cede to I<any>	544	Works like cede, but is not exported by default and will cede to I<any>
293	coroutine, regardless of priority. This is useful sometimes to ensure	545	coro, regardless of priority. This is useful sometimes to ensure
294	progress is made.	546	progress is made.
295		547
296	=item terminate [arg...]	548	=item terminate [arg...]
297		549
298	Terminates the current coroutine with the given status values (see L<cancel>).	550	Terminates the current coro with the given status values (see
		551	L<cancel>). The values will not be copied, but referenced directly.
		552
		553	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
		554
		555	These function install enter and leave winders in the current scope. The
		556	enter block will be executed when on_enter is called and whenever the
		557	current coro is re-entered by the scheduler, while the leave block is
		558	executed whenever the current coro is blocked by the scheduler, and
		559	also when the containing scope is exited (by whatever means, be it exit,
		560	die, last etc.).
		561
		562	I<Neither invoking the scheduler, nor exceptions, are allowed within those
		563	BLOCKs>. That means: do not even think about calling C<die> without an
		564	eval, and do not even think of entering the scheduler in any way.
		565
		566	Since both BLOCKs are tied to the current scope, they will automatically
		567	be removed when the current scope exits.
		568
		569	These functions implement the same concept as C<dynamic-wind> in scheme
		570	does, and are useful when you want to localise some resource to a specific
		571	coro.
		572
		573	They slow down thread switching considerably for coros that use them
		574	(about 40% for a BLOCK with a single assignment, so thread switching is
		575	still reasonably fast if the handlers are fast).
		576
		577	These functions are best understood by an example: The following function
		578	will change the current timezone to "Antarctica/South_Pole", which
		579	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
		580	which remember/change the current timezone and restore the previous
		581	value, respectively, the timezone is only changed for the coro that
		582	installed those handlers.
		583
		584	use POSIX qw(tzset);
		585
		586	async {
		587	my $old_tz; # store outside TZ value here
		588
		589	Coro::on_enter {
		590	$old_tz = $ENV{TZ}; # remember the old value
		591
		592	$ENV{TZ} = "Antarctica/South_Pole";
		593	tzset; # enable new value
		594	};
		595
		596	Coro::on_leave {
		597	$ENV{TZ} = $old_tz;
		598	tzset; # restore old value
		599	};
		600
		601	# at this place, the timezone is Antarctica/South_Pole,
		602	# without disturbing the TZ of any other coro.
		603	};
		604
		605	This can be used to localise about any resource (locale, uid, current
		606	working directory etc.) to a block, despite the existance of other
		607	coros.
		608
		609	Another interesting example implements time-sliced multitasking using
		610	interval timers (this could obviously be optimised, but does the job):
		611
		612	# "timeslice" the given block
		613	sub timeslice(&) {
		614	use Time::HiRes ();
		615
		616	Coro::on_enter {
		617	# on entering the thread, we set an VTALRM handler to cede
		618	$SIG{VTALRM} = sub { cede };
		619	# and then start the interval timer
		620	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
		621	};
		622	Coro::on_leave {
		623	# on leaving the thread, we stop the interval timer again
		624	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
		625	};
		626
		627	&{+shift};
		628	}
		629
		630	# use like this:
		631	timeslice {
		632	# The following is an endless loop that would normally
		633	# monopolise the process. Since it runs in a timesliced
		634	# environment, it will regularly cede to other threads.
		635	while () { }
		636	};
		637
299		638
300	=item killall	639	=item killall
301		640
302	Kills/terminates/cancels all coroutines except the currently running	641	Kills/terminates/cancels all coros except the currently running one.
303	one. This is useful after a fork, either in the child or the parent, as
304	usually only one of them should inherit the running coroutines.
305		642
306	Note that while this will try to free some of the main programs resources,	643	Note that while this will try to free some of the main interpreter
		644	resources if the calling coro isn't the main coro, but one
307	you cannot free all of them, so if a coroutine that is not the main	645	cannot free all of them, so if a coro that is not the main coro
308	program calls this function, there will be some one-time resource leak.	646	calls this function, there will be some one-time resource leak.
309		647
310	=cut	648	=cut
311		649
312	sub killall {	650	sub killall {
313	for (Coro::State::list) {	651	for (Coro::State::list) {
…		…
316	}	654	}
317	}	655	}
318		656
319	=back	657	=back
320		658
321	=head2 COROUTINE METHODS	659	=head1 CORO OBJECT METHODS
322		660
323	These are the methods you can call on coroutine objects (or to create	661	These are the methods you can call on coro objects (or to create
324	them).	662	them).
325		663
326	=over 4	664	=over 4
327		665
328	=item new Coro \&sub [, @args...]	666	=item new Coro \&sub [, @args...]
329		667
330	Create a new coroutine and return it. When the sub returns, the coroutine	668	Create a new coro and return it. When the sub returns, the coro
331	automatically terminates as if C<terminate> with the returned values were	669	automatically terminates as if C<terminate> with the returned values were
332	called. To make the coroutine run you must first put it into the ready	670	called. To make the coro run you must first put it into the ready
333	queue by calling the ready method.	671	queue by calling the ready method.
334		672
335	See C<async> and C<Coro::State::new> for additional info about the	673	See C<async> and C<Coro::State::new> for additional info about the
336	coroutine environment.	674	coro environment.
337		675
338	=cut	676	=cut
339		677
340	sub _terminate {	678	sub _coro_run {
341	terminate &{+shift};	679	terminate &{+shift};
342	}	680	}
343		681
344	=item $success = $coroutine->ready	682	=item $success = $coro->ready
345		683
346	Put the given coroutine into the end of its ready queue (there is one	684	Put the given coro into the end of its ready queue (there is one
347	queue for each priority) and return true. If the coroutine is already in	685	queue for each priority) and return true. If the coro is already in
348	the ready queue, do nothing and return false.	686	the ready queue, do nothing and return false.
349		687
350	This ensures that the scheduler will resume this coroutine automatically	688	This ensures that the scheduler will resume this coro automatically
351	once all the coroutines of higher priority and all coroutines of the same	689	once all the coro of higher priority and all coro of the same
352	priority that were put into the ready queue earlier have been resumed.	690	priority that were put into the ready queue earlier have been resumed.
353		691
		692	=item $coro->suspend
		693
		694	Suspends the specified coro. A suspended coro works just like any other
		695	coro, except that the scheduler will not select a suspended coro for
		696	execution.
		697
		698	Suspending a coro can be useful when you want to keep the coro from
		699	running, but you don't want to destroy it, or when you want to temporarily
		700	freeze a coro (e.g. for debugging) to resume it later.
		701
		702	A scenario for the former would be to suspend all (other) coros after a
		703	fork and keep them alive, so their destructors aren't called, but new
		704	coros can be created.
		705
		706	=item $coro->resume
		707
		708	If the specified coro was suspended, it will be resumed. Note that when
		709	the coro was in the ready queue when it was suspended, it might have been
		710	unreadied by the scheduler, so an activation might have been lost.
		711
		712	To avoid this, it is best to put a suspended coro into the ready queue
		713	unconditionally, as every synchronisation mechanism must protect itself
		714	against spurious wakeups, and the one in the Coro family certainly do
		715	that.
		716
354	=item $is_ready = $coroutine->is_ready	717	=item $is_ready = $coro->is_ready
355		718
356	Return whether the coroutine is currently the ready queue or not,	719	Returns true iff the Coro object is in the ready queue. Unless the Coro
		720	object gets destroyed, it will eventually be scheduled by the scheduler.
357		721
		722	=item $is_running = $coro->is_running
		723
		724	Returns true iff the Coro object is currently running. Only one Coro object
		725	can ever be in the running state (but it currently is possible to have
		726	multiple running Coro::States).
		727
		728	=item $is_suspended = $coro->is_suspended
		729
		730	Returns true iff this Coro object has been suspended. Suspended Coros will
		731	not ever be scheduled.
		732
358	=item $coroutine->cancel (arg...)	733	=item $coro->cancel (arg...)
359		734
360	Terminates the given coroutine and makes it return the given arguments as	735	Terminates the given Coro thread and makes it return the given arguments as
361	status (default: the empty list). Never returns if the coroutine is the	736	status (default: an empty list). Never returns if the Coro is the
362	current coroutine.	737	current Coro.
363		738
364	=cut	739	This is a rather brutal way to free a coro, with some limitations - if
		740	the thread is inside a C callback that doesn't expect to be canceled,
		741	bad things can happen, or if the cancelled thread insists on running
		742	complicated cleanup handlers that rely on it'S thread context, things will
		743	not work.
365		744
366	sub cancel {	745	Sometimes it is safer to C<< ->throw >> an exception, or use C<<
367	my $self = shift;	746	->safe_cancel >>.
368		747
369	if ($current == $self) {	748	The arguments are not copied, but instead will be referenced directly
370	terminate @_;	749	(e.g. if you pass C<$var> and after the call change that variable, then
371	} else {	750	you might change the return values passed to e.g. C<join>, so don't do
372	$self->{_status} = [@_];	751	that).
373	$self->_cancel;	752
		753	The resources of the Coro are usually freed (or destructed) before this
		754	call returns, but this can be delayed for an indefinite amount of time, as
		755	in some cases the manager thread has to run first to actually destruct the
		756	Coro object.
		757
		758	=item $coro->safe_cancel ($arg...)
		759
		760	Works mostly like C<< ->cancel >>, but is inherently "safer", and
		761	consequently, can fail with an exception in cases the thread is not in a
		762	cancellable state.
		763
		764	This method works a bit like throwing an exception that cannot be caught
		765	- specifically, it will clean up the thread from within itself, so all
		766	cleanup handlers (e.g. C<guard> blocks) are run with full thread context
		767	and can block if they wish.
		768
		769	A thread is safe-cancellable if it either hasn't been run yet, or
		770	it has no C context attached and is inside an SLF function.
		771
		772	The latter two basically mean that the thread isn't currently inside a
		773	perl callback called from some C function (usually XS modules) and isn't
		774	currently inside some C function itself.
		775
		776	This call always returns true when it could cancel the thread, or croaks
		777	with an error otherwise, so you can write things like this:
		778
		779	if (! eval { $coro->safe_cancel }) {
		780	warn "unable to cancel thread: $@";
374	}	781	}
375	}
376		782
377	=item $coroutine->schedule_to	783	=item $coro->schedule_to
378		784
379	Puts the current coroutine to sleep (like C<Coro::schedule>), but instead	785	Puts the current coro to sleep (like C<Coro::schedule>), but instead
380	of continuing with the next coro from the ready queue, always switch to	786	of continuing with the next coro from the ready queue, always switch to
381	the given coroutine object (regardless of priority etc.). The readyness	787	the given coro object (regardless of priority etc.). The readyness
382	state of that coroutine isn't changed.	788	state of that coro isn't changed.
383		789
384	This is an advanced method for special cases - I'd love to hear about any	790	This is an advanced method for special cases - I'd love to hear about any
385	uses for this one.	791	uses for this one.
386		792
387	=item $coroutine->cede_to	793	=item $coro->cede_to
388		794
389	Like C<schedule_to>, but puts the current coroutine into the ready	795	Like C<schedule_to>, but puts the current coro into the ready
390	queue. This has the effect of temporarily switching to the given	796	queue. This has the effect of temporarily switching to the given
391	coroutine, and continuing some time later.	797	coro, and continuing some time later.
392		798
393	This is an advanced method for special cases - I'd love to hear about any	799	This is an advanced method for special cases - I'd love to hear about any
394	uses for this one.	800	uses for this one.
395		801
396	=item $coroutine->throw ([$scalar])	802	=item $coro->throw ([$scalar])
397		803
398	If C<$throw> is specified and defined, it will be thrown as an exception	804	If C<$throw> is specified and defined, it will be thrown as an exception
399	inside the coroutine at the next convenient point in time. Otherwise	805	inside the coro at the next convenient point in time. Otherwise
400	clears the exception object.	806	clears the exception object.
401		807
402	Coro will check for the exception each time a schedule-like-function	808	Coro will check for the exception each time a schedule-like-function
403	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down	809	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
404	>>, C<< Coro::Handle->readable >> and so on. Most of these functions	810	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
…		…
406		812
407	The exception object will be thrown "as is" with the specified scalar in	813	The exception object will be thrown "as is" with the specified scalar in
408	C<$@>, i.e. if it is a string, no line number or newline will be appended	814	C<$@>, i.e. if it is a string, no line number or newline will be appended
409	(unlike with C<die>).	815	(unlike with C<die>).
410		816
411	This can be used as a softer means than C<cancel> to ask a coroutine to	817	This can be used as a softer means than C<cancel> to ask a coro to
412	end itself, although there is no guarantee that the exception will lead to	818	end itself, although there is no guarantee that the exception will lead to
413	termination, and if the exception isn't caught it might well end the whole	819	termination, and if the exception isn't caught it might well end the whole
414	program.	820	program.
415		821
416	You might also think of C<throw> as being the moral equivalent of	822	You might also think of C<throw> as being the moral equivalent of
417	C<kill>ing a coroutine with a signal (in this case, a scalar).	823	C<kill>ing a coro with a signal (in this case, a scalar).
418		824
419	=item $coroutine->join	825	=item $coro->join
420		826
421	Wait until the coroutine terminates and return any values given to the	827	Wait until the coro terminates and return any values given to the
422	C<terminate> or C<cancel> functions. C<join> can be called concurrently	828	C<terminate> or C<cancel> functions. C<join> can be called concurrently
423	from multiple coroutines, and all will be resumed and given the status	829	from multiple threads, and all will be resumed and given the status
424	return once the C<$coroutine> terminates.	830	return once the C<$coro> terminates.
425		831
426	=cut	832	=cut
427		833
428	sub join {	834	sub join {
429	my $self = shift;	835	my $self = shift;
…		…
440	}	846	}
441		847
442	wantarray ? @{$self->{_status}} : $self->{_status}[0];	848	wantarray ? @{$self->{_status}} : $self->{_status}[0];
443	}	849	}
444		850
445	=item $coroutine->on_destroy (\&cb)	851	=item $coro->on_destroy (\&cb)
446		852
447	Registers a callback that is called when this coroutine gets destroyed,	853	Registers a callback that is called when this coro thread gets destroyed,
448	but before it is joined. The callback gets passed the terminate arguments,	854	that is, after it's resources have been freed but before it is joined. The
		855	callback gets passed the terminate/cancel arguments, if any, and I<must
449	if any, and I<must not> die, under any circumstances.	856	not> die, under any circumstances.
		857
		858	There can be any number of C<on_destroy> callbacks per coro, and there is
		859	no way currently to remove a callback once added.
450		860
451	=cut	861	=cut
452		862
453	sub on_destroy {	863	sub on_destroy {
454	my ($self, $cb) = @_;	864	my ($self, $cb) = @_;
455		865
456	push @{ $self->{_on_destroy} }, $cb;	866	push @{ $self->{_on_destroy} }, $cb;
457	}	867	}
458		868
459	=item $oldprio = $coroutine->prio ($newprio)	869	=item $oldprio = $coro->prio ($newprio)
460		870
461	Sets (or gets, if the argument is missing) the priority of the	871	Sets (or gets, if the argument is missing) the priority of the
462	coroutine. Higher priority coroutines get run before lower priority	872	coro thread. Higher priority coro get run before lower priority
463	coroutines. Priorities are small signed integers (currently -4 .. +3),	873	coros. Priorities are small signed integers (currently -4 .. +3),
464	that you can refer to using PRIO_xxx constants (use the import tag :prio	874	that you can refer to using PRIO_xxx constants (use the import tag :prio
465	to get then):	875	to get then):
466		876
467	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	877	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
468	3 > 1 > 0 > -1 > -3 > -4	878	3 > 1 > 0 > -1 > -3 > -4
469		879
470	# set priority to HIGH	880	# set priority to HIGH
471	current->prio(PRIO_HIGH);	881	current->prio (PRIO_HIGH);
472		882
473	The idle coroutine ($Coro::idle) always has a lower priority than any	883	The idle coro thread ($Coro::idle) always has a lower priority than any
474	existing coroutine.	884	existing coro.
475		885
476	Changing the priority of the current coroutine will take effect immediately,	886	Changing the priority of the current coro will take effect immediately,
477	but changing the priority of coroutines in the ready queue (but not	887	but changing the priority of a coro in the ready queue (but not running)
478	running) will only take effect after the next schedule (of that	888	will only take effect after the next schedule (of that coro). This is a
479	coroutine). This is a bug that will be fixed in some future version.	889	bug that will be fixed in some future version.
480		890
481	=item $newprio = $coroutine->nice ($change)	891	=item $newprio = $coro->nice ($change)
482		892
483	Similar to C<prio>, but subtract the given value from the priority (i.e.	893	Similar to C<prio>, but subtract the given value from the priority (i.e.
484	higher values mean lower priority, just as in unix).	894	higher values mean lower priority, just as in UNIX's nice command).
485		895
486	=item $olddesc = $coroutine->desc ($newdesc)	896	=item $olddesc = $coro->desc ($newdesc)
487		897
488	Sets (or gets in case the argument is missing) the description for this	898	Sets (or gets in case the argument is missing) the description for this
489	coroutine. This is just a free-form string you can associate with a	899	coro thread. This is just a free-form string you can associate with a
490	coroutine.	900	coro.
491		901
492	This method simply sets the C<< $coroutine->{desc} >> member to the given	902	This method simply sets the C<< $coro->{desc} >> member to the given
493	string. You can modify this member directly if you wish.	903	string. You can modify this member directly if you wish, and in fact, this
		904	is often preferred to indicate major processing states that cna then be
		905	seen for example in a L<Coro::Debug> session:
		906
		907	sub my_long_function {
		908	local $Coro::current->{desc} = "now in my_long_function";
		909	...
		910	$Coro::current->{desc} = "my_long_function: phase 1";
		911	...
		912	$Coro::current->{desc} = "my_long_function: phase 2";
		913	...
		914	}
494		915
495	=cut	916	=cut
496		917
497	sub desc {	918	sub desc {
498	my $old = $_[0]{desc};	919	my $old = $_[0]{desc};
…		…
505	Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");	926	Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
506	}	927	}
507		928
508	=back	929	=back
509		930
510	=head2 GLOBAL FUNCTIONS	931	=head1 GLOBAL FUNCTIONS
511		932
512	=over 4	933	=over 4
513		934
514	=item Coro::nready	935	=item Coro::nready
515		936
516	Returns the number of coroutines that are currently in the ready state,	937	Returns the number of coro that are currently in the ready state,
517	i.e. that can be switched to by calling C<schedule> directory or	938	i.e. that can be switched to by calling C<schedule> directory or
518	indirectly. The value C<0> means that the only runnable coroutine is the	939	indirectly. The value C<0> means that the only runnable coro is the
519	currently running one, so C<cede> would have no effect, and C<schedule>	940	currently running one, so C<cede> would have no effect, and C<schedule>
520	would cause a deadlock unless there is an idle handler that wakes up some	941	would cause a deadlock unless there is an idle handler that wakes up some
521	coroutines.	942	coro.
522		943
523	=item my $guard = Coro::guard { ... }	944	=item my $guard = Coro::guard { ... }
524		945
525	This creates and returns a guard object. Nothing happens until the object	946	This function still exists, but is deprecated. Please use the
526	gets destroyed, in which case the codeblock given as argument will be	947	C<Guard::guard> function instead.
527	executed. This is useful to free locks or other resources in case of a
528	runtime error or when the coroutine gets canceled, as in both cases the
529	guard block will be executed. The guard object supports only one method,
530	C<< ->cancel >>, which will keep the codeblock from being executed.
531		948
532	Example: set some flag and clear it again when the coroutine gets canceled
533	or the function returns:
534
535	sub do_something {
536	my $guard = Coro::guard { $busy = 0 };
537	$busy = 1;
538
539	# do something that requires $busy to be true
540	}
541
542	=cut	949	=cut
543		950
544	sub guard(&) {	951	BEGIN { *guard = \&Guard::guard }
545	bless \(my $cb = $_[0]), "Coro::guard"
546	}
547
548	sub Coro::guard::cancel {
549	${$_[0]} = sub { };
550	}
551
552	sub Coro::guard::DESTROY {
553	${$_[0]}->();
554	}
555
556		952
557	=item unblock_sub { ... }	953	=item unblock_sub { ... }
558		954
559	This utility function takes a BLOCK or code reference and "unblocks" it,	955	This utility function takes a BLOCK or code reference and "unblocks" it,
560	returning a new coderef. Unblocking means that calling the new coderef	956	returning a new coderef. Unblocking means that calling the new coderef
561	will return immediately without blocking, returning nothing, while the	957	will return immediately without blocking, returning nothing, while the
562	original code ref will be called (with parameters) from within another	958	original code ref will be called (with parameters) from within another
563	coroutine.	959	coro.
564		960
565	The reason this function exists is that many event libraries (such as the	961	The reason this function exists is that many event libraries (such as
566	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form	962	the venerable L<Event\|Event> module) are not thread-safe (a weaker form
567	of thread-safety). This means you must not block within event callbacks,	963	of reentrancy). This means you must not block within event callbacks,
568	otherwise you might suffer from crashes or worse. The only event library	964	otherwise you might suffer from crashes or worse. The only event library
569	currently known that is safe to use without C<unblock_sub> is L<EV>.	965	currently known that is safe to use without C<unblock_sub> is L<EV> (but
		966	you might still run into deadlocks if all event loops are blocked).
		967
		968	Coro will try to catch you when you block in the event loop
		969	("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and
		970	only works when you do not run your own event loop.
570		971
571	This function allows your callbacks to block by executing them in another	972	This function allows your callbacks to block by executing them in another
572	coroutine where it is safe to block. One example where blocking is handy	973	coro where it is safe to block. One example where blocking is handy
573	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	974	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
574	disk, for example.	975	disk, for example.
575		976
576	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	977	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
577	creating event callbacks that want to block.	978	creating event callbacks that want to block.
578		979
579	If your handler does not plan to block (e.g. simply sends a message to	980	If your handler does not plan to block (e.g. simply sends a message to
580	another coroutine, or puts some other coroutine into the ready queue),	981	another coro, or puts some other coro into the ready queue), there is
581	there is no reason to use C<unblock_sub>.	982	no reason to use C<unblock_sub>.
582		983
583	Note that you also need to use C<unblock_sub> for any other callbacks that	984	Note that you also need to use C<unblock_sub> for any other callbacks that
584	are indirectly executed by any C-based event loop. For example, when you	985	are indirectly executed by any C-based event loop. For example, when you
585	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it	986	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
586	provides callbacks that are the result of some event callback, then you	987	provides callbacks that are the result of some event callback, then you
…		…
616	unshift @unblock_queue, [$cb, @_];	1017	unshift @unblock_queue, [$cb, @_];
617	$unblock_scheduler->ready;	1018	$unblock_scheduler->ready;
618	}	1019	}
619	}	1020	}
620		1021
621	=item $cb = Coro::rouse_cb	1022	=item $cb = rouse_cb
622		1023
623	Create and return a "rouse callback". That's a code reference that, when	1024	Create and return a "rouse callback". That's a code reference that,
624	called, will save its arguments and notify the owner coroutine of the	1025	when called, will remember a copy of its arguments and notify the owner
625	callback.	1026	coro of the callback.
626		1027
627	See the next function.	1028	See the next function.
628		1029
629	=item @args = Coro::rouse_wait [$cb]	1030	=item @args = rouse_wait [$cb]
630		1031
631	Wait for the specified rouse callback (or the last one tht was created in	1032	Wait for the specified rouse callback (or the last one that was created in
632	this coroutine).	1033	this coro).
633		1034
634	As soon as the callback is invoked (or when the calback was invoked before	1035	As soon as the callback is invoked (or when the callback was invoked
635	C<rouse_wait>), it will return a copy of the arguments originally passed	1036	before C<rouse_wait>), it will return the arguments originally passed to
636	to the rouse callback.	1037	the rouse callback. In scalar context, that means you get the I<last>
		1038	argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
		1039	statement at the end.
637		1040
638	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.	1041	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
639		1042
640	=back	1043	=back
641		1044
642	=cut	1045	=cut
643		1046
		1047	for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) {
		1048	my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"};
		1049
		1050	*{"Coro::$module\::new"} = sub {
		1051	require "Coro/$module.pm";
		1052
		1053	# some modules have their new predefined in State.xs, some don't
		1054	*{"Coro::$module\::new"} = $old
		1055	if $old;
		1056
		1057	goto &{"Coro::$module\::new"};
		1058	};
		1059	}
		1060
644	1;	1061	1;
645		1062
646	=head1 HOW TO WAIT FOR A CALLBACK	1063	=head1 HOW TO WAIT FOR A CALLBACK
647		1064
648	It is very common for a coroutine to wait for some callback to be	1065	It is very common for a coro to wait for some callback to be
649	called. This occurs naturally when you use coroutines in an otherwise	1066	called. This occurs naturally when you use coro in an otherwise
650	event-based program, or when you use event-based libraries.	1067	event-based program, or when you use event-based libraries.
651		1068
652	These typically register a callback for some event, and call that callback	1069	These typically register a callback for some event, and call that callback
653	when the event occured. In a coroutine, however, you typically want to	1070	when the event occured. In a coro, however, you typically want to
654	just wait for the event, simplyifying things.	1071	just wait for the event, simplyifying things.
655		1072
656	For example C<< AnyEvent->child >> registers a callback to be called when	1073	For example C<< AnyEvent->child >> registers a callback to be called when
657	a specific child has exited:	1074	a specific child has exited:
658		1075
659	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });	1076	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
660		1077
661	But from withina coroutine, you often just want to write this:	1078	But from within a coro, you often just want to write this:
662		1079
663	my $status = wait_for_child $pid;	1080	my $status = wait_for_child $pid;
664		1081
665	Coro offers two functions specifically designed to make this easy,	1082	Coro offers two functions specifically designed to make this easy,
666	C<Coro::rouse_cb> and C<Coro::rouse_wait>.	1083	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
667		1084
668	The first function, C<rouse_cb>, generates and returns a callback that,	1085	The first function, C<rouse_cb>, generates and returns a callback that,
669	when invoked, will save it's arguments and notify the coroutine that	1086	when invoked, will save its arguments and notify the coro that
670	created the callback.	1087	created the callback.
671		1088
672	The second function, C<rouse_wait>, waits for the callback to be called	1089	The second function, C<rouse_wait>, waits for the callback to be called
673	(by calling C<schedule> to go to sleep) and returns the arguments	1090	(by calling C<schedule> to go to sleep) and returns the arguments
674	originally passed to the callback.	1091	originally passed to the callback.
…		…
689	you can roll your own, using C<schedule>:	1106	you can roll your own, using C<schedule>:
690		1107
691	sub wait_for_child($) {	1108	sub wait_for_child($) {
692	my ($pid) = @_;	1109	my ($pid) = @_;
693		1110
694	# store the current coroutine in $current,	1111	# store the current coro in $current,
695	# and provide result variables for the closure passed to ->child	1112	# and provide result variables for the closure passed to ->child
696	my $current = $Coro::current;	1113	my $current = $Coro::current;
697	my ($done, $rstatus);	1114	my ($done, $rstatus);
698		1115
699	# pass a closure to ->child	1116	# pass a closure to ->child
…		…
715		1132
716	=item fork with pthread backend	1133	=item fork with pthread backend
717		1134
718	When Coro is compiled using the pthread backend (which isn't recommended	1135	When Coro is compiled using the pthread backend (which isn't recommended
719	but required on many BSDs as their libcs are completely broken), then	1136	but required on many BSDs as their libcs are completely broken), then
720	coroutines will not survive a fork. There is no known workaround except to	1137	coro will not survive a fork. There is no known workaround except to
721	fix your libc and use a saner backend.	1138	fix your libc and use a saner backend.
722		1139
723	=item perl process emulation ("threads")	1140	=item perl process emulation ("threads")
724		1141
725	This module is not perl-pseudo-thread-safe. You should only ever use this	1142	This module is not perl-pseudo-thread-safe. You should only ever use this
726	module from the same thread (this requirement might be removed in the	1143	module from the first thread (this requirement might be removed in the
727	future to allow per-thread schedulers, but Coro::State does not yet allow	1144	future to allow per-thread schedulers, but Coro::State does not yet allow
728	this). I recommend disabling thread support and using processes, as having	1145	this). I recommend disabling thread support and using processes, as having
729	the windows process emulation enabled under unix roughly halves perl	1146	the windows process emulation enabled under unix roughly halves perl
730	performance, even when not used.	1147	performance, even when not used.
731		1148
732	=item coroutine switching not signal safe	1149	=item coro switching is not signal safe
733		1150
734	You must not switch to another coroutine from within a signal handler	1151	You must not switch to another coro from within a signal handler (only
735	(only relevant with %SIG - most event libraries provide safe signals).	1152	relevant with %SIG - most event libraries provide safe signals), I<unless>
		1153	you are sure you are not interrupting a Coro function.
736		1154
737	That means you I<MUST NOT> call any function that might "block" the	1155	That means you I<MUST NOT> call any function that might "block" the
738	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or	1156	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
739	anything that calls those. Everything else, including calling C<ready>,	1157	anything that calls those. Everything else, including calling C<ready>,
740	works.	1158	works.
741		1159
742	=back	1160	=back
743		1161
744		1162
		1163	=head1 WINDOWS PROCESS EMULATION
		1164
		1165	A great many people seem to be confused about ithreads (for example, Chip
		1166	Salzenberg called me unintelligent, incapable, stupid and gullible,
		1167	while in the same mail making rather confused statements about perl
		1168	ithreads (for example, that memory or files would be shared), showing his
		1169	lack of understanding of this area - if it is hard to understand for Chip,
		1170	it is probably not obvious to everybody).
		1171
		1172	What follows is an ultra-condensed version of my talk about threads in
		1173	scripting languages given on the perl workshop 2009:
		1174
		1175	The so-called "ithreads" were originally implemented for two reasons:
		1176	first, to (badly) emulate unix processes on native win32 perls, and
		1177	secondly, to replace the older, real thread model ("5.005-threads").
		1178
		1179	It does that by using threads instead of OS processes. The difference
		1180	between processes and threads is that threads share memory (and other
		1181	state, such as files) between threads within a single process, while
		1182	processes do not share anything (at least not semantically). That
		1183	means that modifications done by one thread are seen by others, while
		1184	modifications by one process are not seen by other processes.
		1185
		1186	The "ithreads" work exactly like that: when creating a new ithreads
		1187	process, all state is copied (memory is copied physically, files and code
		1188	is copied logically). Afterwards, it isolates all modifications. On UNIX,
		1189	the same behaviour can be achieved by using operating system processes,
		1190	except that UNIX typically uses hardware built into the system to do this
		1191	efficiently, while the windows process emulation emulates this hardware in
		1192	software (rather efficiently, but of course it is still much slower than
		1193	dedicated hardware).
		1194
		1195	As mentioned before, loading code, modifying code, modifying data
		1196	structures and so on is only visible in the ithreads process doing the
		1197	modification, not in other ithread processes within the same OS process.
		1198
		1199	This is why "ithreads" do not implement threads for perl at all, only
		1200	processes. What makes it so bad is that on non-windows platforms, you can
		1201	actually take advantage of custom hardware for this purpose (as evidenced
		1202	by the forks module, which gives you the (i-) threads API, just much
		1203	faster).
		1204
		1205	Sharing data is in the i-threads model is done by transfering data
		1206	structures between threads using copying semantics, which is very slow -
		1207	shared data simply does not exist. Benchmarks using i-threads which are
		1208	communication-intensive show extremely bad behaviour with i-threads (in
		1209	fact, so bad that Coro, which cannot take direct advantage of multiple
		1210	CPUs, is often orders of magnitude faster because it shares data using
		1211	real threads, refer to my talk for details).
		1212
		1213	As summary, i-threads use threads to implement processes, while
		1214	the compatible forks module uses processes to emulate, uhm,
		1215	processes. I-threads slow down every perl program when enabled, and
		1216	outside of windows, serve no (or little) practical purpose, but
		1217	disadvantages every single-threaded Perl program.
		1218
		1219	This is the reason that I try to avoid the name "ithreads", as it is
		1220	misleading as it implies that it implements some kind of thread model for
		1221	perl, and prefer the name "windows process emulation", which describes the
		1222	actual use and behaviour of it much better.
		1223
745	=head1 SEE ALSO	1224	=head1 SEE ALSO
746		1225
747	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.	1226	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
748		1227
749	Debugging: L<Coro::Debug>.	1228	Debugging: L<Coro::Debug>.
750		1229
751	Support/Utility: L<Coro::Specific>, L<Coro::Util>.	1230	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
752		1231
753	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.	1232	Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
		1233	L<Coro::SemaphoreSet>, L<Coro::RWLock>.
754		1234
755	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.	1235	I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
756		1236
757	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.	1237	Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
		1238	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
		1239	L<Coro::Select>.
758		1240
759	XS API: L<Coro::MakeMaker>.	1241	XS API: L<Coro::MakeMaker>.
760		1242
761	Low level Configuration, Coroutine Environment: L<Coro::State>.	1243	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
762		1244
763	=head1 AUTHOR	1245	=head1 AUTHOR
764		1246
765	Marc Lehmann <schmorp@schmorp.de>	1247	Marc Lehmann <schmorp@schmorp.de>
766	http://home.schmorp.de/	1248	http://home.schmorp.de/

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Revision 1.233 by root, Fri Nov 21 06:02:07 2008 UTC vs.
Revision 1.294 by root, Fri May 6 21:15:17 2011 UTC