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Revision 1.245 by root, Sun Dec 14 19:52:58 2008 UTC vs.
Revision 1.290 by root, Fri Apr 29 05:29:51 2011 UTC

…		…
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;
…		…
29	=head1 DESCRIPTION	29	=head1 DESCRIPTION
30		30
31	For a tutorial-style introduction, please read the L<Coro::Intro>	31	For a tutorial-style introduction, please read the L<Coro::Intro>
32	manpage. This manpage mainly contains reference information.	32	manpage. This manpage mainly contains reference information.
33		33
34	This module collection manages continuations in general, most often	34	This module collection manages continuations in general, most often in
35	in the form of cooperative threads (also called coroutines in the	35	the form of cooperative threads (also called coros, or simply "coro"
36	documentation). They are similar to kernel threads but don't (in general)	36	in the documentation). They are similar to kernel threads but don't (in
37	run in parallel at the same time even on SMP machines. The specific flavor	37	general) run in parallel at the same time even on SMP machines. The
38	of thread offered by this module also guarantees you that it will not	38	specific flavor of thread offered by this module also guarantees you that
39	switch between threads unless necessary, at easily-identified points in	39	it will not switch between threads unless necessary, at easily-identified
40	your program, so locking and parallel access are rarely an issue, making	40	points in your program, so locking and parallel access are rarely an
41	thread programming much safer and easier than using other thread models.	41	issue, making thread programming much safer and easier than using other
		42	thread models.
42		43
43	Unlike the so-called "Perl threads" (which are not actually real threads	44	Unlike the so-called "Perl threads" (which are not actually real threads
44	but only the windows process emulation ported to unix), Coro provides a	45	but only the windows process emulation (see section of same name for
		46	more details) ported to UNIX, and as such act as processes), Coro
45	full shared address space, which makes communication between threads	47	provides a full shared address space, which makes communication between
46	very easy. And threads are fast, too: disabling the Windows process	48	threads very easy. And coro threads are fast, too: disabling the Windows
47	emulation code in your perl and using Coro can easily result in a two to	49	process emulation code in your perl and using Coro can easily result in
48	four times speed increase for your programs.	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.
49		54
50	Coro achieves that by supporting multiple running interpreters that share	55	Coro achieves that by supporting multiple running interpreters that share
51	data, which is especially useful to code pseudo-parallel processes and	56	data, which is especially useful to code pseudo-parallel processes and
52	for event-based programming, such as multiple HTTP-GET requests running	57	for event-based programming, such as multiple HTTP-GET requests running
53	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro	58	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
54	into an event-based environment.	59	into an event-based environment.
55		60
56	In this module, a thread is defined as "callchain + lexical variables +	61	In this module, a thread is defined as "callchain + lexical variables +
57	@_ + $_ + $@ + $/ + C stack), that is, a thread has its own callchain,	62	some package variables + C stack), that is, a thread has its own callchain,
58	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
59	variables (see L<Coro::State> for more configuration and background info).	64	variables (see L<Coro::State> for more configuration and background info).
60		65
61	See also the C<SEE ALSO> section at the end of this document - the Coro	66	See also the C<SEE ALSO> section at the end of this document - the Coro
62	module family is quite large.	67	module family is quite large.
63		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 >> the coro thread from another
		202	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> without
		211	actually exiting, and might leave C libraries and XS modules in a weird
		212	state. Unlike other thread implementations, however, Coro is exceptionally
		213	safe with regards to cancellation, as perl will always be in a consistent
		214	state.
		215
		216	So, cancelling a thread that runs in an XS event loop might not be the
		217	best idea, but any other combination that deals with perl only (cancelling
		218	when a thread is in a C<tie> method or an C<AUTOLOAD> for example) is
		219	safe.
		220
		221	=item 5. Cleanup
		222
		223	Threads will allocate various resources. Most but not all will be returned
		224	when a thread terminates, during clean-up.
		225
		226	Cleanup is quite similar to throwing an uncaught exception: perl will
		227	work it's way up through all subroutine calls and blocks. On it's way, it
		228	will release all C<my> variables, undo all C<local>'s and free any other
		229	resources truly local to the thread.
		230
		231	So, a common way to free resources is to keep them referenced only by my
		232	variables:
		233
		234	async {
		235	my $big_cache = new Cache ...;
		236	};
		237
		238	If there are no other references, then the C<$big_cache> object will be
		239	freed when the thread terminates, regardless of how it does so.
		240
		241	What it does C<NOT> do is unlock any Coro::Semaphores or similar
		242	resources, but that's where the C<guard> methods come in handy:
		243
		244	my $sem = new Coro::Semaphore;
		245
		246	async {
		247	my $lock_guard = $sem->guard;
		248	# if we reutrn, or die or get cancelled, here,
		249	# then the semaphore will be "up"ed.
		250	};
		251
		252	The C<Guard::guard> function comes in handy for any custom cleanup you
		253	might want to do:
		254
		255	async {
		256	my $window = new Gtk2::Window "toplevel";
		257	# The window will not be cleaned up automatically, even when $window
		258	# gets freed, so use a guard to ensure it's destruction
		259	# in case of an error:
		260	my $window_guard = Guard::guard { $window->destroy };
		261
		262	# we are safe here
		263	};
		264
		265	Last not least, C<local> can often be handy, too, e.g. when temporarily
		266	replacing the coro thread description:
		267
		268	sub myfunction {
		269	local $Coro::current->{desc} = "inside myfunction(@_)";
		270
		271	# if we return or die here, the description will be restored
		272	}
		273
		274	=item 6. Viva La Zombie Muerte
		275
		276	Even after a thread has terminated and cleaned up it's resources, the coro
		277	object still is there and stores the return values of the thread. Only in
		278	this state will the coro object be "reference counted" in the normal perl
		279	sense: the thread code keeps a reference to it when it is active, but not
		280	after it has terminated.
		281
		282	The means the coro object gets freed automatically when the thread has
		283	terminated and cleaned up and there arenot other references.
		284
		285	If there are, the coro object will stay around, and you can call C<<
		286	->join >> as many times as you wish to retrieve the result values:
		287
		288	async {
		289	print "hi\n";
		290	1
		291	};
		292
		293	# run the async above, and free everything before returning
		294	# from Coro::cede:
		295	Coro::cede;
		296
		297	{
		298	my $coro = async {
		299	print "hi\n";
		300	1
		301	};
		302
		303	# run the async above, and clean up, but do not free the coro
		304	# object:
		305	Coro::cede;
		306
		307	# optionally retrieve the result values
		308	my @results = $coro->join;
		309
		310	# now $coro goes out of scope, and presumably gets freed
		311	};
		312
		313	=back
		314
64	=cut	315	=cut
65		316
66	package Coro;	317	package Coro;
67		318
68	use strict qw(vars subs);	319	use common::sense;
69	no warnings "uninitialized";	320
		321	use Carp ();
		322
		323	use Guard ();
70		324
71	use Coro::State;	325	use Coro::State;
72		326
73	use base qw(Coro::State Exporter);	327	use base qw(Coro::State Exporter);
74		328
75	our $idle; # idle handler	329	our $idle; # idle handler
76	our $main; # main coroutine	330	our $main; # main coro
77	our $current; # current coroutine	331	our $current; # current coro
78		332
79	our $VERSION = 5.13;	333	our $VERSION = 5.372;
80		334
81	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	335	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
82	our %EXPORT_TAGS = (	336	our %EXPORT_TAGS = (
83	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	337	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
84	);	338	);
85	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	339	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
86		340
…		…
88		342
89	=over 4	343	=over 4
90		344
91	=item $Coro::main	345	=item $Coro::main
92		346
93	This variable stores the coroutine object that represents the main	347	This variable stores the Coro object that represents the main
94	program. While you cna C<ready> it and do most other things you can do to	348	program. While you cna C<ready> it and do most other things you can do to
95	coroutines, it is mainly useful to compare again C<$Coro::current>, to see	349	coro, it is mainly useful to compare again C<$Coro::current>, to see
96	whether you are running in the main program or not.	350	whether you are running in the main program or not.
97		351
98	=cut	352	=cut
99		353
100	# $main is now being initialised by Coro::State	354	# $main is now being initialised by Coro::State
101		355
102	=item $Coro::current	356	=item $Coro::current
103		357
104	The coroutine object representing the current coroutine (the last	358	The Coro object representing the current coro (the last
105	coroutine that the Coro scheduler switched to). The initial value is	359	coro that the Coro scheduler switched to). The initial value is
106	C<$Coro::main> (of course).	360	C<$Coro::main> (of course).
107		361
108	This variable is B<strictly> I<read-only>. You can take copies of the	362	This variable is B<strictly> I<read-only>. You can take copies of the
109	value stored in it and use it as any other coroutine object, but you must	363	value stored in it and use it as any other Coro object, but you must
110	not otherwise modify the variable itself.	364	not otherwise modify the variable itself.
111		365
112	=cut	366	=cut
113		367
114	sub current() { $current } # [DEPRECATED]	368	sub current() { $current } # [DEPRECATED]
…		…
117		371
118	This variable is mainly useful to integrate Coro into event loops. It is	372	This variable is mainly useful to integrate Coro into event loops. It is
119	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is	373	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
120	pretty low-level functionality.	374	pretty low-level functionality.
121		375
122	This variable stores either a coroutine or a callback.	376	This variable stores a Coro object that is put into the ready queue when
		377	there are no other ready threads (without invoking any ready hooks).
123		378
124	If it is a callback, the it is called whenever the scheduler finds no	379	The default implementation dies with "FATAL: deadlock detected.", followed
125	ready coroutines to run. The default implementation prints "FATAL:	380	by a thread listing, because the program has no other way to continue.
126	deadlock detected" and exits, because the program has no other way to
127	continue.
128
129	If it is a coroutine object, then this object will be readied (without
130	invoking any ready hooks, however) when the scheduler finds no other ready
131	coroutines to run.
132		381
133	This hook is overwritten by modules such as C<Coro::EV> and	382	This hook is overwritten by modules such as C<Coro::EV> and
134	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a	383	C<Coro::AnyEvent> to wait on an external event that hopefully wakes up a
135	coroutine so the scheduler can run it.	384	coro so the scheduler can run it.
136		385
137	Note that the callback I<must not>, under any circumstances, block
138	the current coroutine. Normally, this is achieved by having an "idle
139	coroutine" that calls the event loop and then blocks again, and then
140	readying that coroutine in the idle handler, or by simply placing the idle
141	coroutine in this variable.
142
143	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this	386	See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
144	technique.
145		387
146	Please note that if your callback recursively invokes perl (e.g. for event
147	handlers), then it must be prepared to be called recursively itself.
148
149	=cut	388	=cut
150		389
151	$idle = sub {	390	# \|\|= because other modules could have provided their own by now
152	require Carp;	391	$idle \|\|= new Coro sub {
153	Carp::croak ("FATAL: deadlock detected");	392	require Coro::Debug;
		393	die "FATAL: deadlock detected.\n"
		394	. Coro::Debug::ps_listing ();
154	};	395	};
155		396
156	# this coroutine is necessary because a coroutine	397	# this coro is necessary because a coro
157	# cannot destroy itself.	398	# cannot destroy itself.
158	our @destroy;	399	our @destroy;
159	our $manager;	400	our $manager;
160		401
161	$manager = new Coro sub {	402	$manager = new Coro sub {
162	while () {	403	while () {
163	Coro::_cancel shift @destroy	404	Coro::State::cancel shift @destroy
164	while @destroy;	405	while @destroy;
165		406
166	&schedule;	407	&schedule;
167	}	408	}
168	};	409	};
169	$manager->{desc} = "[coro manager]";	410	$manager->{desc} = "[coro manager]";
170	$manager->prio (PRIO_MAX);	411	$manager->prio (PRIO_MAX);
171		412
172	=back	413	=back
173		414
174	=head1 SIMPLE COROUTINE CREATION	415	=head1 SIMPLE CORO CREATION
175		416
176	=over 4	417	=over 4
177		418
178	=item async { ... } [@args...]	419	=item async { ... } [@args...]
179		420
180	Create a new coroutine and return its coroutine object (usually	421	Create a new coro and return its Coro object (usually
181	unused). The coroutine will be put into the ready queue, so	422	unused). The coro will be put into the ready queue, so
182	it will start running automatically on the next scheduler run.	423	it will start running automatically on the next scheduler run.
183		424
184	The first argument is a codeblock/closure that should be executed in the	425	The first argument is a codeblock/closure that should be executed in the
185	coroutine. When it returns argument returns the coroutine is automatically	426	coro. When it returns argument returns the coro is automatically
186	terminated.	427	terminated.
187		428
188	The remaining arguments are passed as arguments to the closure.	429	The remaining arguments are passed as arguments to the closure.
189		430
190	See the C<Coro::State::new> constructor for info about the coroutine	431	See the C<Coro::State::new> constructor for info about the coro
191	environment in which coroutines are executed.	432	environment in which coro are executed.
192		433
193	Calling C<exit> in a coroutine will do the same as calling exit outside	434	Calling C<exit> in a coro will do the same as calling exit outside
194	the coroutine. Likewise, when the coroutine dies, the program will exit,	435	the coro. Likewise, when the coro dies, the program will exit,
195	just as it would in the main program.	436	just as it would in the main program.
196		437
197	If you do not want that, you can provide a default C<die> handler, or	438	If you do not want that, you can provide a default C<die> handler, or
198	simply avoid dieing (by use of C<eval>).	439	simply avoid dieing (by use of C<eval>).
199		440
200	Example: Create a new coroutine that just prints its arguments.	441	Example: Create a new coro that just prints its arguments.
201		442
202	async {	443	async {
203	print "@_\n";	444	print "@_\n";
204	} 1,2,3,4;	445	} 1,2,3,4;
205		446
206	=cut
207
208	sub async(&@) {
209	my $coro = new Coro @_;
210	$coro->ready;
211	$coro
212	}
213
214	=item async_pool { ... } [@args...]	447	=item async_pool { ... } [@args...]
215		448
216	Similar to C<async>, but uses a coroutine pool, so you should not call	449	Similar to C<async>, but uses a coro pool, so you should not call
217	terminate or join on it (although you are allowed to), and you get a	450	terminate or join on it (although you are allowed to), and you get a
218	coroutine that might have executed other code already (which can be good	451	coro that might have executed other code already (which can be good
219	or bad :).	452	or bad :).
220		453
221	On the plus side, this function is about twice as fast as creating (and	454	On the plus side, this function is about twice as fast as creating (and
222	destroying) a completely new coroutine, so if you need a lot of generic	455	destroying) a completely new coro, so if you need a lot of generic
223	coroutines in quick successsion, use C<async_pool>, not C<async>.	456	coros in quick successsion, use C<async_pool>, not C<async>.
224		457
225	The code block is executed in an C<eval> context and a warning will be	458	The code block is executed in an C<eval> context and a warning will be
226	issued in case of an exception instead of terminating the program, as	459	issued in case of an exception instead of terminating the program, as
227	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>	460	C<async> does. As the coro is being reused, stuff like C<on_destroy>
228	will not work in the expected way, unless you call terminate or cancel,	461	will not work in the expected way, unless you call terminate or cancel,
229	which somehow defeats the purpose of pooling (but is fine in the	462	which somehow defeats the purpose of pooling (but is fine in the
230	exceptional case).	463	exceptional case).
231		464
232	The priority will be reset to C<0> after each run, tracing will be	465	The priority will be reset to C<0> after each run, tracing will be
233	disabled, the description will be reset and the default output filehandle	466	disabled, the description will be reset and the default output filehandle
234	gets restored, so you can change all these. Otherwise the coroutine will	467	gets restored, so you can change all these. Otherwise the coro will
235	be re-used "as-is": most notably if you change other per-coroutine global	468	be re-used "as-is": most notably if you change other per-coro global
236	stuff such as C<$/> you I<must needs> revert that change, which is most	469	stuff such as C<$/> you I<must needs> revert that change, which is most
237	simply done by using local as in: C<< local $/ >>.	470	simply done by using local as in: C<< local $/ >>.
238		471
239	The idle pool size is limited to C<8> idle coroutines (this can be	472	The idle pool size is limited to C<8> idle coros (this can be
240	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle	473	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
241	coros as required.	474	coros as required.
242		475
243	If you are concerned about pooled coroutines growing a lot because a	476	If you are concerned about pooled coros growing a lot because a
244	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool	477	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
245	{ terminate }> once per second or so to slowly replenish the pool. In	478	{ terminate }> once per second or so to slowly replenish the pool. In
246	addition to that, when the stacks used by a handler grows larger than 32kb	479	addition to that, when the stacks used by a handler grows larger than 32kb
247	(adjustable via $Coro::POOL_RSS) it will also be destroyed.	480	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
248		481
…		…
265	=back	498	=back
266		499
267	=head1 STATIC METHODS	500	=head1 STATIC METHODS
268		501
269	Static methods are actually functions that implicitly operate on the	502	Static methods are actually functions that implicitly operate on the
270	current coroutine.	503	current coro.
271		504
272	=over 4	505	=over 4
273		506
274	=item schedule	507	=item schedule
275		508
276	Calls the scheduler. The scheduler will find the next coroutine that is	509	Calls the scheduler. The scheduler will find the next coro that is
277	to be run from the ready queue and switches to it. The next coroutine	510	to be run from the ready queue and switches to it. The next coro
278	to be run is simply the one with the highest priority that is longest	511	to be run is simply the one with the highest priority that is longest
279	in its ready queue. If there is no coroutine ready, it will clal the	512	in its ready queue. If there is no coro ready, it will call the
280	C<$Coro::idle> hook.	513	C<$Coro::idle> hook.
281		514
282	Please note that the current coroutine will I<not> be put into the ready	515	Please note that the current coro will I<not> be put into the ready
283	queue, so calling this function usually means you will never be called	516	queue, so calling this function usually means you will never be called
284	again unless something else (e.g. an event handler) calls C<< ->ready >>,	517	again unless something else (e.g. an event handler) calls C<< ->ready >>,
285	thus waking you up.	518	thus waking you up.
286		519
287	This makes C<schedule> I<the> generic method to use to block the current	520	This makes C<schedule> I<the> generic method to use to block the current
288	coroutine and wait for events: first you remember the current coroutine in	521	coro and wait for events: first you remember the current coro in
289	a variable, then arrange for some callback of yours to call C<< ->ready	522	a variable, then arrange for some callback of yours to call C<< ->ready
290	>> on that once some event happens, and last you call C<schedule> to put	523	>> on that once some event happens, and last you call C<schedule> to put
291	yourself to sleep. Note that a lot of things can wake your coroutine up,	524	yourself to sleep. Note that a lot of things can wake your coro up,
292	so you need to check whether the event indeed happened, e.g. by storing the	525	so you need to check whether the event indeed happened, e.g. by storing the
293	status in a variable.	526	status in a variable.
294		527
295	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.	528	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
296		529
297	=item cede	530	=item cede
298		531
299	"Cede" to other coroutines. This function puts the current coroutine into	532	"Cede" to other coros. This function puts the current coro into
300	the ready queue and calls C<schedule>, which has the effect of giving	533	the ready queue and calls C<schedule>, which has the effect of giving
301	up the current "timeslice" to other coroutines of the same or higher	534	up the current "timeslice" to other coros of the same or higher
302	priority. Once your coroutine gets its turn again it will automatically be	535	priority. Once your coro gets its turn again it will automatically be
303	resumed.	536	resumed.
304		537
305	This function is often called C<yield> in other languages.	538	This function is often called C<yield> in other languages.
306		539
307	=item Coro::cede_notself	540	=item Coro::cede_notself
308		541
309	Works like cede, but is not exported by default and will cede to I<any>	542	Works like cede, but is not exported by default and will cede to I<any>
310	coroutine, regardless of priority. This is useful sometimes to ensure	543	coro, regardless of priority. This is useful sometimes to ensure
311	progress is made.	544	progress is made.
312		545
313	=item terminate [arg...]	546	=item terminate [arg...]
314		547
315	Terminates the current coroutine with the given status values (see L<cancel>).	548	Terminates the current coro with the given status values (see L<cancel>).
		549
		550	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
		551
		552	These function install enter and leave winders in the current scope. The
		553	enter block will be executed when on_enter is called and whenever the
		554	current coro is re-entered by the scheduler, while the leave block is
		555	executed whenever the current coro is blocked by the scheduler, and
		556	also when the containing scope is exited (by whatever means, be it exit,
		557	die, last etc.).
		558
		559	I<Neither invoking the scheduler, nor exceptions, are allowed within those
		560	BLOCKs>. That means: do not even think about calling C<die> without an
		561	eval, and do not even think of entering the scheduler in any way.
		562
		563	Since both BLOCKs are tied to the current scope, they will automatically
		564	be removed when the current scope exits.
		565
		566	These functions implement the same concept as C<dynamic-wind> in scheme
		567	does, and are useful when you want to localise some resource to a specific
		568	coro.
		569
		570	They slow down thread switching considerably for coros that use them
		571	(about 40% for a BLOCK with a single assignment, so thread switching is
		572	still reasonably fast if the handlers are fast).
		573
		574	These functions are best understood by an example: The following function
		575	will change the current timezone to "Antarctica/South_Pole", which
		576	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
		577	which remember/change the current timezone and restore the previous
		578	value, respectively, the timezone is only changed for the coro that
		579	installed those handlers.
		580
		581	use POSIX qw(tzset);
		582
		583	async {
		584	my $old_tz; # store outside TZ value here
		585
		586	Coro::on_enter {
		587	$old_tz = $ENV{TZ}; # remember the old value
		588
		589	$ENV{TZ} = "Antarctica/South_Pole";
		590	tzset; # enable new value
		591	};
		592
		593	Coro::on_leave {
		594	$ENV{TZ} = $old_tz;
		595	tzset; # restore old value
		596	};
		597
		598	# at this place, the timezone is Antarctica/South_Pole,
		599	# without disturbing the TZ of any other coro.
		600	};
		601
		602	This can be used to localise about any resource (locale, uid, current
		603	working directory etc.) to a block, despite the existance of other
		604	coros.
		605
		606	Another interesting example implements time-sliced multitasking using
		607	interval timers (this could obviously be optimised, but does the job):
		608
		609	# "timeslice" the given block
		610	sub timeslice(&) {
		611	use Time::HiRes ();
		612
		613	Coro::on_enter {
		614	# on entering the thread, we set an VTALRM handler to cede
		615	$SIG{VTALRM} = sub { cede };
		616	# and then start the interval timer
		617	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
		618	};
		619	Coro::on_leave {
		620	# on leaving the thread, we stop the interval timer again
		621	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
		622	};
		623
		624	&{+shift};
		625	}
		626
		627	# use like this:
		628	timeslice {
		629	# The following is an endless loop that would normally
		630	# monopolise the process. Since it runs in a timesliced
		631	# environment, it will regularly cede to other threads.
		632	while () { }
		633	};
		634
316		635
317	=item killall	636	=item killall
318		637
319	Kills/terminates/cancels all coroutines except the currently running	638	Kills/terminates/cancels all coros except the currently running one.
320	one. This can be useful after a fork, either in the child or the parent,
321	as usually only one of them should inherit the running coroutines.
322		639
323	Note that in the implementation, destructors run as normal, making this
324	function not so useful after a fork. Future versions of this function
325	might try to free resources without running any code.
326
327	Note that while this will try to free some of the main programs resources,	640	Note that while this will try to free some of the main interpreter
		641	resources if the calling coro isn't the main coro, but one
328	you cannot free all of them, so if a coroutine that is not the main	642	cannot free all of them, so if a coro that is not the main coro
329	program calls this function, there will be some one-time resource leak.	643	calls this function, there will be some one-time resource leak.
330		644
331	=cut	645	=cut
332		646
333	sub killall {	647	sub killall {
334	for (Coro::State::list) {	648	for (Coro::State::list) {
…		…
337	}	651	}
338	}	652	}
339		653
340	=back	654	=back
341		655
342	=head1 COROUTINE OBJECT METHODS	656	=head1 CORO OBJECT METHODS
343		657
344	These are the methods you can call on coroutine objects (or to create	658	These are the methods you can call on coro objects (or to create
345	them).	659	them).
346		660
347	=over 4	661	=over 4
348		662
349	=item new Coro \&sub [, @args...]	663	=item new Coro \&sub [, @args...]
350		664
351	Create a new coroutine and return it. When the sub returns, the coroutine	665	Create a new coro and return it. When the sub returns, the coro
352	automatically terminates as if C<terminate> with the returned values were	666	automatically terminates as if C<terminate> with the returned values were
353	called. To make the coroutine run you must first put it into the ready	667	called. To make the coro run you must first put it into the ready
354	queue by calling the ready method.	668	queue by calling the ready method.
355		669
356	See C<async> and C<Coro::State::new> for additional info about the	670	See C<async> and C<Coro::State::new> for additional info about the
357	coroutine environment.	671	coro environment.
358		672
359	=cut	673	=cut
360		674
361	sub _coro_run {	675	sub _coro_run {
362	terminate &{+shift};	676	terminate &{+shift};
363	}	677	}
364		678
365	=item $success = $coroutine->ready	679	=item $success = $coro->ready
366		680
367	Put the given coroutine into the end of its ready queue (there is one	681	Put the given coro into the end of its ready queue (there is one
368	queue for each priority) and return true. If the coroutine is already in	682	queue for each priority) and return true. If the coro is already in
369	the ready queue, do nothing and return false.	683	the ready queue, do nothing and return false.
370		684
371	This ensures that the scheduler will resume this coroutine automatically	685	This ensures that the scheduler will resume this coro automatically
372	once all the coroutines of higher priority and all coroutines of the same	686	once all the coro of higher priority and all coro of the same
373	priority that were put into the ready queue earlier have been resumed.	687	priority that were put into the ready queue earlier have been resumed.
374		688
		689	=item $coro->suspend
		690
		691	Suspends the specified coro. A suspended coro works just like any other
		692	coro, except that the scheduler will not select a suspended coro for
		693	execution.
		694
		695	Suspending a coro can be useful when you want to keep the coro from
		696	running, but you don't want to destroy it, or when you want to temporarily
		697	freeze a coro (e.g. for debugging) to resume it later.
		698
		699	A scenario for the former would be to suspend all (other) coros after a
		700	fork and keep them alive, so their destructors aren't called, but new
		701	coros can be created.
		702
		703	=item $coro->resume
		704
		705	If the specified coro was suspended, it will be resumed. Note that when
		706	the coro was in the ready queue when it was suspended, it might have been
		707	unreadied by the scheduler, so an activation might have been lost.
		708
		709	To avoid this, it is best to put a suspended coro into the ready queue
		710	unconditionally, as every synchronisation mechanism must protect itself
		711	against spurious wakeups, and the one in the Coro family certainly do
		712	that.
		713
375	=item $is_ready = $coroutine->is_ready	714	=item $is_ready = $coro->is_ready
376		715
377	Return whether the coroutine is currently the ready queue or not,	716	Returns true iff the Coro object is in the ready queue. Unless the Coro
		717	object gets destroyed, it will eventually be scheduled by the scheduler.
378		718
		719	=item $is_running = $coro->is_running
		720
		721	Returns true iff the Coro object is currently running. Only one Coro object
		722	can ever be in the running state (but it currently is possible to have
		723	multiple running Coro::States).
		724
		725	=item $is_suspended = $coro->is_suspended
		726
		727	Returns true iff this Coro object has been suspended. Suspended Coros will
		728	not ever be scheduled.
		729
379	=item $coroutine->cancel (arg...)	730	=item $coro->cancel (arg...)
380		731
381	Terminates the given coroutine and makes it return the given arguments as	732	Terminates the given Coro and makes it return the given arguments as
382	status (default: the empty list). Never returns if the coroutine is the	733	status (default: an empty list). Never returns if the Coro is the
383	current coroutine.	734	current Coro.
384		735
385	=cut	736	=cut
386		737
387	sub cancel {	738	sub cancel {
388	my $self = shift;	739	my $self = shift;
389		740
390	if ($current == $self) {	741	if ($current == $self) {
391	terminate @_;	742	terminate @_;
392	} else {	743	} else {
393	$self->{_status} = [@_];	744	$self->{_status} = [@_];
394	$self->_cancel;	745	Coro::State::cancel $self;
395	}	746	}
396	}	747	}
397		748
398	=item $coroutine->schedule_to	749	=item $coro->schedule_to
399		750
400	Puts the current coroutine to sleep (like C<Coro::schedule>), but instead	751	Puts the current coro to sleep (like C<Coro::schedule>), but instead
401	of continuing with the next coro from the ready queue, always switch to	752	of continuing with the next coro from the ready queue, always switch to
402	the given coroutine object (regardless of priority etc.). The readyness	753	the given coro object (regardless of priority etc.). The readyness
403	state of that coroutine isn't changed.	754	state of that coro isn't changed.
404		755
405	This is an advanced method for special cases - I'd love to hear about any	756	This is an advanced method for special cases - I'd love to hear about any
406	uses for this one.	757	uses for this one.
407		758
408	=item $coroutine->cede_to	759	=item $coro->cede_to
409		760
410	Like C<schedule_to>, but puts the current coroutine into the ready	761	Like C<schedule_to>, but puts the current coro into the ready
411	queue. This has the effect of temporarily switching to the given	762	queue. This has the effect of temporarily switching to the given
412	coroutine, and continuing some time later.	763	coro, and continuing some time later.
413		764
414	This is an advanced method for special cases - I'd love to hear about any	765	This is an advanced method for special cases - I'd love to hear about any
415	uses for this one.	766	uses for this one.
416		767
417	=item $coroutine->throw ([$scalar])	768	=item $coro->throw ([$scalar])
418		769
419	If C<$throw> is specified and defined, it will be thrown as an exception	770	If C<$throw> is specified and defined, it will be thrown as an exception
420	inside the coroutine at the next convenient point in time. Otherwise	771	inside the coro at the next convenient point in time. Otherwise
421	clears the exception object.	772	clears the exception object.
422		773
423	Coro will check for the exception each time a schedule-like-function	774	Coro will check for the exception each time a schedule-like-function
424	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down	775	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
425	>>, C<< Coro::Handle->readable >> and so on. Most of these functions	776	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
…		…
427		778
428	The exception object will be thrown "as is" with the specified scalar in	779	The exception object will be thrown "as is" with the specified scalar in
429	C<$@>, i.e. if it is a string, no line number or newline will be appended	780	C<$@>, i.e. if it is a string, no line number or newline will be appended
430	(unlike with C<die>).	781	(unlike with C<die>).
431		782
432	This can be used as a softer means than C<cancel> to ask a coroutine to	783	This can be used as a softer means than C<cancel> to ask a coro to
433	end itself, although there is no guarantee that the exception will lead to	784	end itself, although there is no guarantee that the exception will lead to
434	termination, and if the exception isn't caught it might well end the whole	785	termination, and if the exception isn't caught it might well end the whole
435	program.	786	program.
436		787
437	You might also think of C<throw> as being the moral equivalent of	788	You might also think of C<throw> as being the moral equivalent of
438	C<kill>ing a coroutine with a signal (in this case, a scalar).	789	C<kill>ing a coro with a signal (in this case, a scalar).
439		790
440	=item $coroutine->join	791	=item $coro->join
441		792
442	Wait until the coroutine terminates and return any values given to the	793	Wait until the coro terminates and return any values given to the
443	C<terminate> or C<cancel> functions. C<join> can be called concurrently	794	C<terminate> or C<cancel> functions. C<join> can be called concurrently
444	from multiple coroutines, and all will be resumed and given the status	795	from multiple coro, and all will be resumed and given the status
445	return once the C<$coroutine> terminates.	796	return once the C<$coro> terminates.
446		797
447	=cut	798	=cut
448		799
449	sub join {	800	sub join {
450	my $self = shift;	801	my $self = shift;
…		…
461	}	812	}
462		813
463	wantarray ? @{$self->{_status}} : $self->{_status}[0];	814	wantarray ? @{$self->{_status}} : $self->{_status}[0];
464	}	815	}
465		816
466	=item $coroutine->on_destroy (\&cb)	817	=item $coro->on_destroy (\&cb)
467		818
468	Registers a callback that is called when this coroutine gets destroyed,	819	Registers a callback that is called when this coro thread gets destroyed,
469	but before it is joined. The callback gets passed the terminate arguments,	820	but before it is joined. The callback gets passed the terminate arguments,
470	if any, and I<must not> die, under any circumstances.	821	if any, and I<must not> die, under any circumstances.
471		822
		823	There can be any number of C<on_destroy> callbacks per coro.
		824
472	=cut	825	=cut
473		826
474	sub on_destroy {	827	sub on_destroy {
475	my ($self, $cb) = @_;	828	my ($self, $cb) = @_;
476		829
477	push @{ $self->{_on_destroy} }, $cb;	830	push @{ $self->{_on_destroy} }, $cb;
478	}	831	}
479		832
480	=item $oldprio = $coroutine->prio ($newprio)	833	=item $oldprio = $coro->prio ($newprio)
481		834
482	Sets (or gets, if the argument is missing) the priority of the	835	Sets (or gets, if the argument is missing) the priority of the
483	coroutine. Higher priority coroutines get run before lower priority	836	coro thread. Higher priority coro get run before lower priority
484	coroutines. Priorities are small signed integers (currently -4 .. +3),	837	coros. Priorities are small signed integers (currently -4 .. +3),
485	that you can refer to using PRIO_xxx constants (use the import tag :prio	838	that you can refer to using PRIO_xxx constants (use the import tag :prio
486	to get then):	839	to get then):
487		840
488	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	841	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
489	3 > 1 > 0 > -1 > -3 > -4	842	3 > 1 > 0 > -1 > -3 > -4
490		843
491	# set priority to HIGH	844	# set priority to HIGH
492	current->prio(PRIO_HIGH);	845	current->prio (PRIO_HIGH);
493		846
494	The idle coroutine ($Coro::idle) always has a lower priority than any	847	The idle coro thread ($Coro::idle) always has a lower priority than any
495	existing coroutine.	848	existing coro.
496		849
497	Changing the priority of the current coroutine will take effect immediately,	850	Changing the priority of the current coro will take effect immediately,
498	but changing the priority of coroutines in the ready queue (but not	851	but changing the priority of a coro in the ready queue (but not running)
499	running) will only take effect after the next schedule (of that	852	will only take effect after the next schedule (of that coro). This is a
500	coroutine). This is a bug that will be fixed in some future version.	853	bug that will be fixed in some future version.
501		854
502	=item $newprio = $coroutine->nice ($change)	855	=item $newprio = $coro->nice ($change)
503		856
504	Similar to C<prio>, but subtract the given value from the priority (i.e.	857	Similar to C<prio>, but subtract the given value from the priority (i.e.
505	higher values mean lower priority, just as in unix).	858	higher values mean lower priority, just as in UNIX's nice command).
506		859
507	=item $olddesc = $coroutine->desc ($newdesc)	860	=item $olddesc = $coro->desc ($newdesc)
508		861
509	Sets (or gets in case the argument is missing) the description for this	862	Sets (or gets in case the argument is missing) the description for this
510	coroutine. This is just a free-form string you can associate with a	863	coro thread. This is just a free-form string you can associate with a
511	coroutine.	864	coro.
512		865
513	This method simply sets the C<< $coroutine->{desc} >> member to the given	866	This method simply sets the C<< $coro->{desc} >> member to the given
514	string. You can modify this member directly if you wish.	867	string. You can modify this member directly if you wish, and in fact, this
		868	is often preferred to indicate major processing states that cna then be
		869	seen for example in a L<Coro::Debug> session:
		870
		871	sub my_long_function {
		872	local $Coro::current->{desc} = "now in my_long_function";
		873	...
		874	$Coro::current->{desc} = "my_long_function: phase 1";
		875	...
		876	$Coro::current->{desc} = "my_long_function: phase 2";
		877	...
		878	}
515		879
516	=cut	880	=cut
517		881
518	sub desc {	882	sub desc {
519	my $old = $_[0]{desc};	883	my $old = $_[0]{desc};
…		…
532		896
533	=over 4	897	=over 4
534		898
535	=item Coro::nready	899	=item Coro::nready
536		900
537	Returns the number of coroutines that are currently in the ready state,	901	Returns the number of coro that are currently in the ready state,
538	i.e. that can be switched to by calling C<schedule> directory or	902	i.e. that can be switched to by calling C<schedule> directory or
539	indirectly. The value C<0> means that the only runnable coroutine is the	903	indirectly. The value C<0> means that the only runnable coro is the
540	currently running one, so C<cede> would have no effect, and C<schedule>	904	currently running one, so C<cede> would have no effect, and C<schedule>
541	would cause a deadlock unless there is an idle handler that wakes up some	905	would cause a deadlock unless there is an idle handler that wakes up some
542	coroutines.	906	coro.
543		907
544	=item my $guard = Coro::guard { ... }	908	=item my $guard = Coro::guard { ... }
545		909
546	This function still exists, but is deprecated. Please use the	910	This function still exists, but is deprecated. Please use the
547	C<Guard::guard> function instead.	911	C<Guard::guard> function instead.
…		…
554		918
555	This utility function takes a BLOCK or code reference and "unblocks" it,	919	This utility function takes a BLOCK or code reference and "unblocks" it,
556	returning a new coderef. Unblocking means that calling the new coderef	920	returning a new coderef. Unblocking means that calling the new coderef
557	will return immediately without blocking, returning nothing, while the	921	will return immediately without blocking, returning nothing, while the
558	original code ref will be called (with parameters) from within another	922	original code ref will be called (with parameters) from within another
559	coroutine.	923	coro.
560		924
561	The reason this function exists is that many event libraries (such as the	925	The reason this function exists is that many event libraries (such as
562	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form	926	the venerable L<Event\|Event> module) are not thread-safe (a weaker form
563	of reentrancy). This means you must not block within event callbacks,	927	of reentrancy). This means you must not block within event callbacks,
564	otherwise you might suffer from crashes or worse. The only event library	928	otherwise you might suffer from crashes or worse. The only event library
565	currently known that is safe to use without C<unblock_sub> is L<EV>.	929	currently known that is safe to use without C<unblock_sub> is L<EV> (but
		930	you might still run into deadlocks if all event loops are blocked).
		931
		932	Coro will try to catch you when you block in the event loop
		933	("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and
		934	only works when you do not run your own event loop.
566		935
567	This function allows your callbacks to block by executing them in another	936	This function allows your callbacks to block by executing them in another
568	coroutine where it is safe to block. One example where blocking is handy	937	coro where it is safe to block. One example where blocking is handy
569	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	938	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
570	disk, for example.	939	disk, for example.
571		940
572	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	941	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
573	creating event callbacks that want to block.	942	creating event callbacks that want to block.
574		943
575	If your handler does not plan to block (e.g. simply sends a message to	944	If your handler does not plan to block (e.g. simply sends a message to
576	another coroutine, or puts some other coroutine into the ready queue),	945	another coro, or puts some other coro into the ready queue), there is
577	there is no reason to use C<unblock_sub>.	946	no reason to use C<unblock_sub>.
578		947
579	Note that you also need to use C<unblock_sub> for any other callbacks that	948	Note that you also need to use C<unblock_sub> for any other callbacks that
580	are indirectly executed by any C-based event loop. For example, when you	949	are indirectly executed by any C-based event loop. For example, when you
581	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it	950	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
582	provides callbacks that are the result of some event callback, then you	951	provides callbacks that are the result of some event callback, then you
…		…
612	unshift @unblock_queue, [$cb, @_];	981	unshift @unblock_queue, [$cb, @_];
613	$unblock_scheduler->ready;	982	$unblock_scheduler->ready;
614	}	983	}
615	}	984	}
616		985
617	=item $cb = Coro::rouse_cb	986	=item $cb = rouse_cb
618		987
619	Create and return a "rouse callback". That's a code reference that,	988	Create and return a "rouse callback". That's a code reference that,
620	when called, will remember a copy of its arguments and notify the owner	989	when called, will remember a copy of its arguments and notify the owner
621	coroutine of the callback.	990	coro of the callback.
622		991
623	See the next function.	992	See the next function.
624		993
625	=item @args = Coro::rouse_wait [$cb]	994	=item @args = rouse_wait [$cb]
626		995
627	Wait for the specified rouse callback (or the last one that was created in	996	Wait for the specified rouse callback (or the last one that was created in
628	this coroutine).	997	this coro).
629		998
630	As soon as the callback is invoked (or when the callback was invoked	999	As soon as the callback is invoked (or when the callback was invoked
631	before C<rouse_wait>), it will return the arguments originally passed to	1000	before C<rouse_wait>), it will return the arguments originally passed to
632	the rouse callback.	1001	the rouse callback. In scalar context, that means you get the I<last>
		1002	argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
		1003	statement at the end.
633		1004
634	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.	1005	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
635		1006
636	=back	1007	=back
637		1008
638	=cut	1009	=cut
639		1010
		1011	for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) {
		1012	my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"};
		1013
		1014	*{"Coro::$module\::new"} = sub {
		1015	require "Coro/$module.pm";
		1016
		1017	# some modules have their new predefined in State.xs, some don't
		1018	*{"Coro::$module\::new"} = $old
		1019	if $old;
		1020
		1021	goto &{"Coro::$module\::new"};
		1022	};
		1023	}
		1024
640	1;	1025	1;
641		1026
642	=head1 HOW TO WAIT FOR A CALLBACK	1027	=head1 HOW TO WAIT FOR A CALLBACK
643		1028
644	It is very common for a coroutine to wait for some callback to be	1029	It is very common for a coro to wait for some callback to be
645	called. This occurs naturally when you use coroutines in an otherwise	1030	called. This occurs naturally when you use coro in an otherwise
646	event-based program, or when you use event-based libraries.	1031	event-based program, or when you use event-based libraries.
647		1032
648	These typically register a callback for some event, and call that callback	1033	These typically register a callback for some event, and call that callback
649	when the event occured. In a coroutine, however, you typically want to	1034	when the event occured. In a coro, however, you typically want to
650	just wait for the event, simplyifying things.	1035	just wait for the event, simplyifying things.
651		1036
652	For example C<< AnyEvent->child >> registers a callback to be called when	1037	For example C<< AnyEvent->child >> registers a callback to be called when
653	a specific child has exited:	1038	a specific child has exited:
654		1039
655	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });	1040	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
656		1041
657	But from withina coroutine, you often just want to write this:	1042	But from within a coro, you often just want to write this:
658		1043
659	my $status = wait_for_child $pid;	1044	my $status = wait_for_child $pid;
660		1045
661	Coro offers two functions specifically designed to make this easy,	1046	Coro offers two functions specifically designed to make this easy,
662	C<Coro::rouse_cb> and C<Coro::rouse_wait>.	1047	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
663		1048
664	The first function, C<rouse_cb>, generates and returns a callback that,	1049	The first function, C<rouse_cb>, generates and returns a callback that,
665	when invoked, will save its arguments and notify the coroutine that	1050	when invoked, will save its arguments and notify the coro that
666	created the callback.	1051	created the callback.
667		1052
668	The second function, C<rouse_wait>, waits for the callback to be called	1053	The second function, C<rouse_wait>, waits for the callback to be called
669	(by calling C<schedule> to go to sleep) and returns the arguments	1054	(by calling C<schedule> to go to sleep) and returns the arguments
670	originally passed to the callback.	1055	originally passed to the callback.
…		…
685	you can roll your own, using C<schedule>:	1070	you can roll your own, using C<schedule>:
686		1071
687	sub wait_for_child($) {	1072	sub wait_for_child($) {
688	my ($pid) = @_;	1073	my ($pid) = @_;
689		1074
690	# store the current coroutine in $current,	1075	# store the current coro in $current,
691	# and provide result variables for the closure passed to ->child	1076	# and provide result variables for the closure passed to ->child
692	my $current = $Coro::current;	1077	my $current = $Coro::current;
693	my ($done, $rstatus);	1078	my ($done, $rstatus);
694		1079
695	# pass a closure to ->child	1080	# pass a closure to ->child
…		…
711		1096
712	=item fork with pthread backend	1097	=item fork with pthread backend
713		1098
714	When Coro is compiled using the pthread backend (which isn't recommended	1099	When Coro is compiled using the pthread backend (which isn't recommended
715	but required on many BSDs as their libcs are completely broken), then	1100	but required on many BSDs as their libcs are completely broken), then
716	coroutines will not survive a fork. There is no known workaround except to	1101	coro will not survive a fork. There is no known workaround except to
717	fix your libc and use a saner backend.	1102	fix your libc and use a saner backend.
718		1103
719	=item perl process emulation ("threads")	1104	=item perl process emulation ("threads")
720		1105
721	This module is not perl-pseudo-thread-safe. You should only ever use this	1106	This module is not perl-pseudo-thread-safe. You should only ever use this
…		…
723	future to allow per-thread schedulers, but Coro::State does not yet allow	1108	future to allow per-thread schedulers, but Coro::State does not yet allow
724	this). I recommend disabling thread support and using processes, as having	1109	this). I recommend disabling thread support and using processes, as having
725	the windows process emulation enabled under unix roughly halves perl	1110	the windows process emulation enabled under unix roughly halves perl
726	performance, even when not used.	1111	performance, even when not used.
727		1112
728	=item coroutine switching not signal safe	1113	=item coro switching is not signal safe
729		1114
730	You must not switch to another coroutine from within a signal handler	1115	You must not switch to another coro from within a signal handler (only
731	(only relevant with %SIG - most event libraries provide safe signals).	1116	relevant with %SIG - most event libraries provide safe signals), I<unless>
		1117	you are sure you are not interrupting a Coro function.
732		1118
733	That means you I<MUST NOT> call any function that might "block" the	1119	That means you I<MUST NOT> call any function that might "block" the
734	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or	1120	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
735	anything that calls those. Everything else, including calling C<ready>,	1121	anything that calls those. Everything else, including calling C<ready>,
736	works.	1122	works.
737		1123
738	=back	1124	=back
739		1125
		1126
		1127	=head1 WINDOWS PROCESS EMULATION
		1128
		1129	A great many people seem to be confused about ithreads (for example, Chip
		1130	Salzenberg called me unintelligent, incapable, stupid and gullible,
		1131	while in the same mail making rather confused statements about perl
		1132	ithreads (for example, that memory or files would be shared), showing his
		1133	lack of understanding of this area - if it is hard to understand for Chip,
		1134	it is probably not obvious to everybody).
		1135
		1136	What follows is an ultra-condensed version of my talk about threads in
		1137	scripting languages given on the perl workshop 2009:
		1138
		1139	The so-called "ithreads" were originally implemented for two reasons:
		1140	first, to (badly) emulate unix processes on native win32 perls, and
		1141	secondly, to replace the older, real thread model ("5.005-threads").
		1142
		1143	It does that by using threads instead of OS processes. The difference
		1144	between processes and threads is that threads share memory (and other
		1145	state, such as files) between threads within a single process, while
		1146	processes do not share anything (at least not semantically). That
		1147	means that modifications done by one thread are seen by others, while
		1148	modifications by one process are not seen by other processes.
		1149
		1150	The "ithreads" work exactly like that: when creating a new ithreads
		1151	process, all state is copied (memory is copied physically, files and code
		1152	is copied logically). Afterwards, it isolates all modifications. On UNIX,
		1153	the same behaviour can be achieved by using operating system processes,
		1154	except that UNIX typically uses hardware built into the system to do this
		1155	efficiently, while the windows process emulation emulates this hardware in
		1156	software (rather efficiently, but of course it is still much slower than
		1157	dedicated hardware).
		1158
		1159	As mentioned before, loading code, modifying code, modifying data
		1160	structures and so on is only visible in the ithreads process doing the
		1161	modification, not in other ithread processes within the same OS process.
		1162
		1163	This is why "ithreads" do not implement threads for perl at all, only
		1164	processes. What makes it so bad is that on non-windows platforms, you can
		1165	actually take advantage of custom hardware for this purpose (as evidenced
		1166	by the forks module, which gives you the (i-) threads API, just much
		1167	faster).
		1168
		1169	Sharing data is in the i-threads model is done by transfering data
		1170	structures between threads using copying semantics, which is very slow -
		1171	shared data simply does not exist. Benchmarks using i-threads which are
		1172	communication-intensive show extremely bad behaviour with i-threads (in
		1173	fact, so bad that Coro, which cannot take direct advantage of multiple
		1174	CPUs, is often orders of magnitude faster because it shares data using
		1175	real threads, refer to my talk for details).
		1176
		1177	As summary, i-threads use threads to implement processes, while
		1178	the compatible forks module uses processes to emulate, uhm,
		1179	processes. I-threads slow down every perl program when enabled, and
		1180	outside of windows, serve no (or little) practical purpose, but
		1181	disadvantages every single-threaded Perl program.
		1182
		1183	This is the reason that I try to avoid the name "ithreads", as it is
		1184	misleading as it implies that it implements some kind of thread model for
		1185	perl, and prefer the name "windows process emulation", which describes the
		1186	actual use and behaviour of it much better.
740		1187
741	=head1 SEE ALSO	1188	=head1 SEE ALSO
742		1189
743	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.	1190	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
744		1191

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Revision 1.290 by root, Fri Apr 29 05:29:51 2011 UTC