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

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Revision 1.181 by root, Fri May 9 22:04:37 2008 UTC vs.
Revision 1.293 by root, Sat Apr 30 05:20:03 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	my $lock = new Coro::Semaphore;	22	my $lock = new Coro::Semaphore;
22	my $locked;	23	my $locked;
23		24
24	$lock->down;	25	$lock->down;
25	$locked = 1;	26	$locked = 1;
26	$lock->up;	27	$lock->up;
27		28
28	=head1 DESCRIPTION	29	=head1 DESCRIPTION
29		30
30	This module collection manages coroutines. Coroutines are similar to	31	For a tutorial-style introduction, please read the L<Coro::Intro>
31	threads but don't (in general) run in parallel at the same time even	32	manpage. This manpage mainly contains reference information.
32	on SMP machines. The specific flavor of coroutine used in this module
33	also guarantees you that it will not switch between coroutines unless
34	necessary, at easily-identified points in your program, so locking and
35	parallel access are rarely an issue, making coroutine programming much
36	safer and easier than threads programming.
37		33
38	Unlike a normal perl program, however, coroutines allow you to have	34	This module collection manages continuations in general, most often in
39	multiple running interpreters that share data, which is especially useful	35	the form of cooperative threads (also called coros, or simply "coro"
40	to code pseudo-parallel processes, such as multiple HTTP-GET requests	36	in the documentation). They are similar to kernel threads but don't (in
41	running concurrently.	37	general) run in parallel at the same time even on SMP machines. The
		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.
42		43
43	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
44	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
45	emulation coming from the Windows platform: On standard operating systems	46	more details) ported to UNIX, and as such act as processes), Coro
46	they serve no purpose whatsoever, except by making your programs slow and	47	provides a full shared address space, which makes communication between
47	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
48	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.
49		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
50	In this module, coroutines are defined as "callchain + lexical variables +	61	In this module, a thread is defined as "callchain + lexical variables +
51	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,	62	some package variables + C stack), that is, a thread has its own callchain,
52	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
53	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 >> 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
54		314
55	=cut	315	=cut
56		316
57	package Coro;	317	package Coro;
58		318
59	use strict;	319	use common::sense;
60	no warnings "uninitialized";	320
		321	use Carp ();
		322
		323	use Guard ();
61		324
62	use Coro::State;	325	use Coro::State;
63		326
64	use base qw(Coro::State Exporter);	327	use base qw(Coro::State Exporter);
65		328
66	our $idle; # idle handler	329	our $idle; # idle handler
67	our $main; # main coroutine	330	our $main; # main coro
68	our $current; # current coroutine	331	our $current; # current coro
69		332
70	our $VERSION = 4.6;	333	our $VERSION = 5.372;
71		334
72	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	335	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
73	our %EXPORT_TAGS = (	336	our %EXPORT_TAGS = (
74	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	337	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
75	);	338	);
76	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	339	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
77		340
		341	=head1 GLOBAL VARIABLES
		342
78	=over 4	343	=over 4
79		344
80	=item $Coro::main	345	=item $Coro::main
81		346
82	This variable stores the coroutine object that represents the main	347	This variable stores the Coro object that represents the main
83	program. While you cna C<ready> it and do most other things you can do to	348	program. While you cna C<ready> it and do most other things you can do to
84	coroutines, it is mainly useful to compare again C<$Coro::current>, to see	349	coro, it is mainly useful to compare again C<$Coro::current>, to see
85	wether you are running in the main program or not.	350	whether you are running in the main program or not.
86		351
87	=cut	352	=cut
88		353
89	$main = new Coro;	354	# $main is now being initialised by Coro::State
90		355
91	=item $Coro::current	356	=item $Coro::current
92		357
93	The coroutine object representing the current coroutine (the last	358	The Coro object representing the current coro (the last
94	coroutine that the Coro scheduler switched to). The initial value is	359	coro that the Coro scheduler switched to). The initial value is
95	C<$main> (of course).	360	C<$Coro::main> (of course).
96		361
97	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
98	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
99	not otherwise modify the variable itself.	364	not otherwise modify the variable itself.
100		365
101	=cut	366	=cut
102		367
103	$main->{desc} = "[main::]";
104
105	# maybe some other module used Coro::Specific before...
106	$main->{_specific} = $current->{_specific}
107	if $current;
108
109	_set_current $main;
110
111	sub current() { $current } # [DEPRECATED]	368	sub current() { $current } # [DEPRECATED]
112		369
113	=item $Coro::idle	370	=item $Coro::idle
114		371
115	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
116	usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is	373	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
117	pretty low-level functionality.	374	pretty low-level functionality.
118		375
119	This variable stores a callback that is called whenever the scheduler	376	This variable stores a Coro object that is put into the ready queue when
120	finds no ready coroutines to run. The default implementation prints	377	there are no other ready threads (without invoking any ready hooks).
121	"FATAL: deadlock detected" and exits, because the program has no other way
122	to continue.
123		378
		379	The default implementation dies with "FATAL: deadlock detected.", followed
		380	by a thread listing, because the program has no other way to continue.
		381
124	This hook is overwritten by modules such as C<Coro::Timer> and	382	This hook is overwritten by modules such as C<Coro::EV> and
125	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
126	coroutine so the scheduler can run it.	384	coro so the scheduler can run it.
127		385
128	Note that the callback I<must not>, under any circumstances, block
129	the current coroutine. Normally, this is achieved by having an "idle
130	coroutine" that calls the event loop and then blocks again, and then
131	readying that coroutine in the idle handler.
132
133	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.
134	technique.
135		387
136	Please note that if your callback recursively invokes perl (e.g. for event
137	handlers), then it must be prepared to be called recursively itself.
138
139	=cut	388	=cut
140		389
141	$idle = sub {	390	# \|\|= because other modules could have provided their own by now
142	require Carp;	391	$idle \|\|= new Coro sub {
143	Carp::croak ("FATAL: deadlock detected");	392	require Coro::Debug;
		393	die "FATAL: deadlock detected.\n"
		394	. Coro::Debug::ps_listing ();
144	};	395	};
145		396
146	sub _cancel {
147	my ($self) = @_;
148
149	# free coroutine data and mark as destructed
150	$self->_destroy
151	or return;
152
153	# call all destruction callbacks
154	$_->(@{$self->{_status}})
155	for @{(delete $self->{_on_destroy}) \|\| []};
156	}
157
158	# this coroutine is necessary because a coroutine	397	# this coro is necessary because a coro
159	# cannot destroy itself.	398	# cannot destroy itself.
160	my @destroy;	399	our @destroy;
161	my $manager;	400	our $manager;
162		401
163	$manager = new Coro sub {	402	$manager = new Coro sub {
164	while () {	403	while () {
165	(shift @destroy)->_cancel	404	_destroy shift @destroy
166	while @destroy;	405	while @destroy;
167		406
168	&schedule;	407	&schedule;
169	}	408	}
170	};	409	};
171	$manager->desc ("[coro manager]");	410	$manager->{desc} = "[coro manager]";
172	$manager->prio (PRIO_MAX);	411	$manager->prio (PRIO_MAX);
173		412
174	=back	413	=back
175		414
176	=head2 SIMPLE COROUTINE CREATION	415	=head1 SIMPLE CORO CREATION
177		416
178	=over 4	417	=over 4
179		418
180	=item async { ... } [@args...]	419	=item async { ... } [@args...]
181		420
182	Create a new coroutine and return it's coroutine object (usually	421	Create a new coro and return its Coro object (usually
183	unused). The coroutine will be put into the ready queue, so	422	unused). The coro will be put into the ready queue, so
184	it will start running automatically on the next scheduler run.	423	it will start running automatically on the next scheduler run.
185		424
186	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
187	coroutine. When it returns argument returns the coroutine is automatically	426	coro. When it returns argument returns the coro is automatically
188	terminated.	427	terminated.
189		428
190	The remaining arguments are passed as arguments to the closure.	429	The remaining arguments are passed as arguments to the closure.
191		430
192	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
193	environment in which coroutines are executed.	432	environment in which coro are executed.
194		433
195	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
196	the coroutine. Likewise, when the coroutine dies, the program will exit,	435	the coro. Likewise, when the coro dies, the program will exit,
197	just as it would in the main program.	436	just as it would in the main program.
198		437
199	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
200	simply avoid dieing (by use of C<eval>).	439	simply avoid dieing (by use of C<eval>).
201		440
202	Example: Create a new coroutine that just prints its arguments.	441	Example: Create a new coro that just prints its arguments.
203		442
204	async {	443	async {
205	print "@_\n";	444	print "@_\n";
206	} 1,2,3,4;	445	} 1,2,3,4;
207		446
208	=cut
209
210	sub async(&@) {
211	my $coro = new Coro @_;
212	$coro->ready;
213	$coro
214	}
215
216	=item async_pool { ... } [@args...]	447	=item async_pool { ... } [@args...]
217		448
218	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
219	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
220	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
221	or bad :).	452	or bad :).
222		453
223	On the plus side, this function is faster than creating (and destroying)	454	On the plus side, this function is about twice as fast as creating (and
224	a completely new coroutine, so if you need a lot of generic coroutines in	455	destroying) a completely new coro, so if you need a lot of generic
225	quick successsion, use C<async_pool>, not C<async>.	456	coros in quick successsion, use C<async_pool>, not C<async>.
226		457
227	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
228	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
229	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>
230	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,
231	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
232	exceptional case).	463	exceptional case).
233		464
234	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
235	disabled, the description will be reset and the default output filehandle	466	disabled, the description will be reset and the default output filehandle
236	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
237	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
238	stuff such as C<$/> you I<must needs> to revert that change, which is most	469	stuff such as C<$/> you I<must needs> revert that change, which is most
239	simply done by using local as in: C< local $/ >.	470	simply done by using local as in: C<< local $/ >>.
240		471
241	The pool size is limited to C<8> idle coroutines (this can be adjusted by	472	The idle pool size is limited to C<8> idle coros (this can be
242	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as	473	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
243	required.	474	coros as required.
244		475
245	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
246	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
247	{ 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
248	addition to that, when the stacks used by a handler grows larger than 16kb	479	addition to that, when the stacks used by a handler grows larger than 32kb
249	(adjustable via $Coro::POOL_RSS) it will also be destroyed.	480	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
250		481
251	=cut	482	=cut
252		483
253	our $POOL_SIZE = 8;	484	our $POOL_SIZE = 8;
254	our $POOL_RSS = 16 * 1024;	485	our $POOL_RSS = 32 * 1024;
255	our @async_pool;	486	our @async_pool;
256		487
257	sub pool_handler {	488	sub pool_handler {
258	my $cb;
259
260	while () {	489	while () {
261	eval {	490	eval {
262	while () {	491	&{&_pool_handler} while 1;
263	_pool_1 $cb;
264	&$cb;
265	_pool_2 $cb;
266	&schedule;
267	}
268	};	492	};
269		493
270	last if $@ eq "\3async_pool terminate\2\n";
271	warn $@ if $@;	494	warn $@ if $@;
272	}	495	}
273	}	496	}
274		497
275	sub async_pool(&@) {
276	# this is also inlined into the unlock_scheduler
277	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
278
279	$coro->{_invoke} = [@_];
280	$coro->ready;
281
282	$coro
283	}
284
285	=back	498	=back
286		499
287	=head2 STATIC METHODS	500	=head1 STATIC METHODS
288		501
289	Static methods are actually functions that operate on the current coroutine.	502	Static methods are actually functions that implicitly operate on the
		503	current coro.
290		504
291	=over 4	505	=over 4
292		506
293	=item schedule	507	=item schedule
294		508
295	Calls the scheduler. The scheduler will find the next coroutine that is	509	Calls the scheduler. The scheduler will find the next coro that is
296	to be run from the ready queue and switches to it. The next coroutine	510	to be run from the ready queue and switches to it. The next coro
297	to be run is simply the one with the highest priority that is longest	511	to be run is simply the one with the highest priority that is longest
298	in its ready queue. If there is no coroutine ready, it will clal the	512	in its ready queue. If there is no coro ready, it will call the
299	C<$Coro::idle> hook.	513	C<$Coro::idle> hook.
300		514
301	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
302	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
303	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 >>,
304	thus waking you up.	518	thus waking you up.
305		519
306	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
307	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
308	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
309	>> 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
310	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,
311	so you need to check wether 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
312	status in a variable.	526	status in a variable.
313		527
314	The canonical way to wait on external events is this:	528	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
315		529
316	{	530	=item cede
317	# remember current coroutine
318	my $current = $Coro::current;
319		531
320	# register a hypothetical event handler	532	"Cede" to other coros. This function puts the current coro into
321	on_event_invoke sub {	533	the ready queue and calls C<schedule>, which has the effect of giving
322	# wake up sleeping coroutine	534	up the current "timeslice" to other coros of the same or higher
323	$current->ready;	535	priority. Once your coro gets its turn again it will automatically be
324	undef $current;	536	resumed.
		537
		538	This function is often called C<yield> in other languages.
		539
		540	=item Coro::cede_notself
		541
		542	Works like cede, but is not exported by default and will cede to I<any>
		543	coro, regardless of priority. This is useful sometimes to ensure
		544	progress is made.
		545
		546	=item terminate [arg...]
		547
		548	Terminates the current coro with the given status values (see
		549	L<cancel>). The values will not be copied, but referenced directly.
		550
		551	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
		552
		553	These function install enter and leave winders in the current scope. The
		554	enter block will be executed when on_enter is called and whenever the
		555	current coro is re-entered by the scheduler, while the leave block is
		556	executed whenever the current coro is blocked by the scheduler, and
		557	also when the containing scope is exited (by whatever means, be it exit,
		558	die, last etc.).
		559
		560	I<Neither invoking the scheduler, nor exceptions, are allowed within those
		561	BLOCKs>. That means: do not even think about calling C<die> without an
		562	eval, and do not even think of entering the scheduler in any way.
		563
		564	Since both BLOCKs are tied to the current scope, they will automatically
		565	be removed when the current scope exits.
		566
		567	These functions implement the same concept as C<dynamic-wind> in scheme
		568	does, and are useful when you want to localise some resource to a specific
		569	coro.
		570
		571	They slow down thread switching considerably for coros that use them
		572	(about 40% for a BLOCK with a single assignment, so thread switching is
		573	still reasonably fast if the handlers are fast).
		574
		575	These functions are best understood by an example: The following function
		576	will change the current timezone to "Antarctica/South_Pole", which
		577	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
		578	which remember/change the current timezone and restore the previous
		579	value, respectively, the timezone is only changed for the coro that
		580	installed those handlers.
		581
		582	use POSIX qw(tzset);
		583
		584	async {
		585	my $old_tz; # store outside TZ value here
		586
		587	Coro::on_enter {
		588	$old_tz = $ENV{TZ}; # remember the old value
		589
		590	$ENV{TZ} = "Antarctica/South_Pole";
		591	tzset; # enable new value
325	};	592	};
326		593
327	# call schedule until event occurred.	594	Coro::on_leave {
328	# in case we are woken up for other reasons	595	$ENV{TZ} = $old_tz;
329	# (current still defined), loop.	596	tzset; # restore old value
330	Coro::schedule while $current;	597	};
		598
		599	# at this place, the timezone is Antarctica/South_Pole,
		600	# without disturbing the TZ of any other coro.
331	}	601	};
332		602
333	=item cede	603	This can be used to localise about any resource (locale, uid, current
		604	working directory etc.) to a block, despite the existance of other
		605	coros.
334		606
335	"Cede" to other coroutines. This function puts the current coroutine into	607	Another interesting example implements time-sliced multitasking using
336	the ready queue and calls C<schedule>, which has the effect of giving	608	interval timers (this could obviously be optimised, but does the job):
337	up the current "timeslice" to other coroutines of the same or higher
338	priority. Once your coroutine gets its turn again it will automatically be
339	resumed.
340		609
341	This function is often called C<yield> in other languages.	610	# "timeslice" the given block
		611	sub timeslice(&) {
		612	use Time::HiRes ();
342		613
343	=item Coro::cede_notself	614	Coro::on_enter {
		615	# on entering the thread, we set an VTALRM handler to cede
		616	$SIG{VTALRM} = sub { cede };
		617	# and then start the interval timer
		618	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
		619	};
		620	Coro::on_leave {
		621	# on leaving the thread, we stop the interval timer again
		622	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
		623	};
344		624
345	Works like cede, but is not exported by default and will cede to I<any>	625	&{+shift};
346	coroutine, regardless of priority. This is useful sometimes to ensure	626	}
347	progress is made.
348		627
349	=item terminate [arg...]	628	# use like this:
		629	timeslice {
		630	# The following is an endless loop that would normally
		631	# monopolise the process. Since it runs in a timesliced
		632	# environment, it will regularly cede to other threads.
		633	while () { }
		634	};
350		635
351	Terminates the current coroutine with the given status values (see L<cancel>).
352		636
353	=item killall	637	=item killall
354		638
355	Kills/terminates/cancels all coroutines except the currently running	639	Kills/terminates/cancels all coros except the currently running one.
356	one. This is useful after a fork, either in the child or the parent, as
357	usually only one of them should inherit the running coroutines.
358		640
359	Note that while this will try to free some of the main programs resources,	641	Note that while this will try to free some of the main interpreter
		642	resources if the calling coro isn't the main coro, but one
360	you cnanot free all of them, so if a coroutine that is not the main	643	cannot free all of them, so if a coro that is not the main coro
361	program calls this function, there will be some one-time resource leak.	644	calls this function, there will be some one-time resource leak.
362		645
363	=cut	646	=cut
364
365	sub terminate {
366	$current->cancel (@_);
367	}
368		647
369	sub killall {	648	sub killall {
370	for (Coro::State::list) {	649	for (Coro::State::list) {
371	$_->cancel	650	$_->cancel
372	if $_ != $current && UNIVERSAL::isa $_, "Coro";	651	if $_ != $current && UNIVERSAL::isa $_, "Coro";
373	}	652	}
374	}	653	}
375		654
376	=back	655	=back
377		656
378	=head2 COROUTINE METHODS	657	=head1 CORO OBJECT METHODS
379		658
380	These are the methods you can call on coroutine objects (or to create	659	These are the methods you can call on coro objects (or to create
381	them).	660	them).
382		661
383	=over 4	662	=over 4
384		663
385	=item new Coro \&sub [, @args...]	664	=item new Coro \&sub [, @args...]
386		665
387	Create a new coroutine and return it. When the sub returns, the coroutine	666	Create a new coro and return it. When the sub returns, the coro
388	automatically terminates as if C<terminate> with the returned values were	667	automatically terminates as if C<terminate> with the returned values were
389	called. To make the coroutine run you must first put it into the ready	668	called. To make the coro run you must first put it into the ready
390	queue by calling the ready method.	669	queue by calling the ready method.
391		670
392	See C<async> and C<Coro::State::new> for additional info about the	671	See C<async> and C<Coro::State::new> for additional info about the
393	coroutine environment.	672	coro environment.
394		673
395	=cut	674	=cut
396		675
397	sub _run_coro {	676	sub _coro_run {
398	terminate &{+shift};	677	terminate &{+shift};
399	}	678	}
400		679
401	sub new {
402	my $class = shift;
403
404	$class->SUPER::new (\&_run_coro, @_)
405	}
406
407	=item $success = $coroutine->ready	680	=item $success = $coro->ready
408		681
409	Put the given coroutine into the end of its ready queue (there is one	682	Put the given coro into the end of its ready queue (there is one
410	queue for each priority) and return true. If the coroutine is already in	683	queue for each priority) and return true. If the coro is already in
411	the ready queue, do nothing and return false.	684	the ready queue, do nothing and return false.
412		685
413	This ensures that the scheduler will resume this coroutine automatically	686	This ensures that the scheduler will resume this coro automatically
414	once all the coroutines of higher priority and all coroutines of the same	687	once all the coro of higher priority and all coro of the same
415	priority that were put into the ready queue earlier have been resumed.	688	priority that were put into the ready queue earlier have been resumed.
416		689
		690	=item $coro->suspend
		691
		692	Suspends the specified coro. A suspended coro works just like any other
		693	coro, except that the scheduler will not select a suspended coro for
		694	execution.
		695
		696	Suspending a coro can be useful when you want to keep the coro from
		697	running, but you don't want to destroy it, or when you want to temporarily
		698	freeze a coro (e.g. for debugging) to resume it later.
		699
		700	A scenario for the former would be to suspend all (other) coros after a
		701	fork and keep them alive, so their destructors aren't called, but new
		702	coros can be created.
		703
		704	=item $coro->resume
		705
		706	If the specified coro was suspended, it will be resumed. Note that when
		707	the coro was in the ready queue when it was suspended, it might have been
		708	unreadied by the scheduler, so an activation might have been lost.
		709
		710	To avoid this, it is best to put a suspended coro into the ready queue
		711	unconditionally, as every synchronisation mechanism must protect itself
		712	against spurious wakeups, and the one in the Coro family certainly do
		713	that.
		714
417	=item $is_ready = $coroutine->is_ready	715	=item $is_ready = $coro->is_ready
418		716
419	Return wether the coroutine is currently the ready queue or not,	717	Returns true iff the Coro object is in the ready queue. Unless the Coro
		718	object gets destroyed, it will eventually be scheduled by the scheduler.
420		719
		720	=item $is_running = $coro->is_running
		721
		722	Returns true iff the Coro object is currently running. Only one Coro object
		723	can ever be in the running state (but it currently is possible to have
		724	multiple running Coro::States).
		725
		726	=item $is_suspended = $coro->is_suspended
		727
		728	Returns true iff this Coro object has been suspended. Suspended Coros will
		729	not ever be scheduled.
		730
421	=item $coroutine->cancel (arg...)	731	=item $coro->cancel (arg...)
422		732
423	Terminates the given coroutine and makes it return the given arguments as	733	Terminates the given Coro object and makes it return the given arguments as
424	status (default: the empty list). Never returns if the coroutine is the	734	status (default: an empty list). Never returns if the Coro is the
425	current coroutine.	735	current Coro.
426		736
427	=cut	737	The arguments are not copied, but instead will be referenced directly
		738	(e.g. if you pass C<$var> and after the call change that variable, then
		739	you might change the return values passed to e.g. C<join>, so don't do
		740	that).
428		741
429	sub cancel {	742	The resources of the Coro are usually freed (or destructed) before this
430	my $self = shift;	743	call returns, but this can be delayed for an indefinite amount of time, as
431	$self->{_status} = [@_];	744	in some cases the manager thread has to run first to actually destruct the
		745	Coro object.
432		746
433	if ($current == $self) {	747	=item $coro->schedule_to
434	push @destroy, $self;
435	$manager->ready;
436	&schedule while 1;
437	} else {
438	$self->_cancel;
439	}
440	}
441		748
		749	Puts the current coro to sleep (like C<Coro::schedule>), but instead
		750	of continuing with the next coro from the ready queue, always switch to
		751	the given coro object (regardless of priority etc.). The readyness
		752	state of that coro isn't changed.
		753
		754	This is an advanced method for special cases - I'd love to hear about any
		755	uses for this one.
		756
		757	=item $coro->cede_to
		758
		759	Like C<schedule_to>, but puts the current coro into the ready
		760	queue. This has the effect of temporarily switching to the given
		761	coro, and continuing some time later.
		762
		763	This is an advanced method for special cases - I'd love to hear about any
		764	uses for this one.
		765
		766	=item $coro->throw ([$scalar])
		767
		768	If C<$throw> is specified and defined, it will be thrown as an exception
		769	inside the coro at the next convenient point in time. Otherwise
		770	clears the exception object.
		771
		772	Coro will check for the exception each time a schedule-like-function
		773	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		774	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		775	detect this case and return early in case an exception is pending.
		776
		777	The exception object will be thrown "as is" with the specified scalar in
		778	C<$@>, i.e. if it is a string, no line number or newline will be appended
		779	(unlike with C<die>).
		780
		781	This can be used as a softer means than C<cancel> to ask a coro to
		782	end itself, although there is no guarantee that the exception will lead to
		783	termination, and if the exception isn't caught it might well end the whole
		784	program.
		785
		786	You might also think of C<throw> as being the moral equivalent of
		787	C<kill>ing a coro with a signal (in this case, a scalar).
		788
442	=item $coroutine->join	789	=item $coro->join
443		790
444	Wait until the coroutine terminates and return any values given to the	791	Wait until the coro terminates and return any values given to the
445	C<terminate> or C<cancel> functions. C<join> can be called concurrently	792	C<terminate> or C<cancel> functions. C<join> can be called concurrently
446	from multiple coroutines, and all will be resumed and given the status	793	from multiple threads, and all will be resumed and given the status
447	return once the C<$coroutine> terminates.	794	return once the C<$coro> terminates.
448		795
449	=cut	796	=cut
450		797
451	sub join {	798	sub join {
452	my $self = shift;	799	my $self = shift;
…		…
463	}	810	}
464		811
465	wantarray ? @{$self->{_status}} : $self->{_status}[0];	812	wantarray ? @{$self->{_status}} : $self->{_status}[0];
466	}	813	}
467		814
468	=item $coroutine->on_destroy (\&cb)	815	=item $coro->on_destroy (\&cb)
469		816
470	Registers a callback that is called when this coroutine gets destroyed,	817	Registers a callback that is called when this coro thread gets destroyed,
471	but before it is joined. The callback gets passed the terminate arguments,	818	that is, after it's resources have been freed but before it is joined. The
		819	callback gets passed the terminate/cancel arguments, if any, and I<must
472	if any, and I<must not> die, under any circumstances.	820	not> die, under any circumstances.
		821
		822	There can be any number of C<on_destroy> callbacks per coro, and there is
		823	no way currently to remove a callback once added.
473		824
474	=cut	825	=cut
475		826
476	sub on_destroy {	827	sub on_destroy {
477	my ($self, $cb) = @_;	828	my ($self, $cb) = @_;
478		829
479	push @{ $self->{_on_destroy} }, $cb;	830	push @{ $self->{_on_destroy} }, $cb;
480	}	831	}
481		832
482	=item $oldprio = $coroutine->prio ($newprio)	833	=item $oldprio = $coro->prio ($newprio)
483		834
484	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
485	coroutine. Higher priority coroutines get run before lower priority	836	coro thread. Higher priority coro get run before lower priority
486	coroutines. Priorities are small signed integers (currently -4 .. +3),	837	coros. Priorities are small signed integers (currently -4 .. +3),
487	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
488	to get then):	839	to get then):
489		840
490	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
491	3 > 1 > 0 > -1 > -3 > -4	842	3 > 1 > 0 > -1 > -3 > -4
492		843
493	# set priority to HIGH	844	# set priority to HIGH
494	current->prio(PRIO_HIGH);	845	current->prio (PRIO_HIGH);
495		846
496	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
497	existing coroutine.	848	existing coro.
498		849
499	Changing the priority of the current coroutine will take effect immediately,	850	Changing the priority of the current coro will take effect immediately,
500	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)
501	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
502	coroutine). This is a bug that will be fixed in some future version.	853	bug that will be fixed in some future version.
503		854
504	=item $newprio = $coroutine->nice ($change)	855	=item $newprio = $coro->nice ($change)
505		856
506	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.
507	higher values mean lower priority, just as in unix).	858	higher values mean lower priority, just as in UNIX's nice command).
508		859
509	=item $olddesc = $coroutine->desc ($newdesc)	860	=item $olddesc = $coro->desc ($newdesc)
510		861
511	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
512	coroutine. This is just a free-form string you can associate with a coroutine.	863	coro thread. This is just a free-form string you can associate with a
		864	coro.
513		865
514	This method simply sets the C<< $coroutine->{desc} >> member to the given string. You	866	This method simply sets the C<< $coro->{desc} >> member to the given
515	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:
516		870
517	=item $coroutine->throw ([$scalar])	871	sub my_long_function {
518		872	local $Coro::current->{desc} = "now in my_long_function";
519	If C<$throw> is specified and defined, it will be thrown as an exception	873	...
520	inside the coroutine at the next convinient point in time (usually after	874	$Coro::current->{desc} = "my_long_function: phase 1";
521	it gains control at the next schedule/transfer/cede). Otherwise clears the	875	...
522	exception object.	876	$Coro::current->{desc} = "my_long_function: phase 2";
523		877	...
524	The exception object will be thrown "as is" with the specified scalar in	878	}
525	C<$@>, i.e. if it is a string, no line number or newline will be appended
526	(unlike with C<die>).
527
528	This can be used as a softer means than C<cancel> to ask a coroutine to
529	end itself, although there is no guarentee that the exception will lead to
530	termination, and if the exception isn't caught it might well end the whole
531	program.
532		879
533	=cut	880	=cut
534		881
535	sub desc {	882	sub desc {
536	my $old = $_[0]{desc};	883	my $old = $_[0]{desc};
537	$_[0]{desc} = $_[1] if @_ > 1;	884	$_[0]{desc} = $_[1] if @_ > 1;
538	$old;	885	$old;
539	}	886	}
540		887
		888	sub transfer {
		889	require Carp;
		890	Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
		891	}
		892
541	=back	893	=back
542		894
543	=head2 GLOBAL FUNCTIONS	895	=head1 GLOBAL FUNCTIONS
544		896
545	=over 4	897	=over 4
546		898
547	=item Coro::nready	899	=item Coro::nready
548		900
549	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,
550	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
551	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
552	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>
553	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
554	coroutines.	906	coro.
555		907
556	=item my $guard = Coro::guard { ... }	908	=item my $guard = Coro::guard { ... }
557		909
558	This creates and returns a guard object. Nothing happens until the object	910	This function still exists, but is deprecated. Please use the
559	gets destroyed, in which case the codeblock given as argument will be	911	C<Guard::guard> function instead.
560	executed. This is useful to free locks or other resources in case of a
561	runtime error or when the coroutine gets canceled, as in both cases the
562	guard block will be executed. The guard object supports only one method,
563	C<< ->cancel >>, which will keep the codeblock from being executed.
564		912
565	Example: set some flag and clear it again when the coroutine gets canceled
566	or the function returns:
567
568	sub do_something {
569	my $guard = Coro::guard { $busy = 0 };
570	$busy = 1;
571
572	# do something that requires $busy to be true
573	}
574
575	=cut	913	=cut
576		914
577	sub guard(&) {	915	BEGIN { *guard = \&Guard::guard }
578	bless \(my $cb = $_[0]), "Coro::guard"
579	}
580
581	sub Coro::guard::cancel {
582	${$_[0]} = sub { };
583	}
584
585	sub Coro::guard::DESTROY {
586	${$_[0]}->();
587	}
588
589		916
590	=item unblock_sub { ... }	917	=item unblock_sub { ... }
591		918
592	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,
593	returning a new coderef. Unblocking means that calling the new coderef	920	returning a new coderef. Unblocking means that calling the new coderef
594	will return immediately without blocking, returning nothing, while the	921	will return immediately without blocking, returning nothing, while the
595	original code ref will be called (with parameters) from within another	922	original code ref will be called (with parameters) from within another
596	coroutine.	923	coro.
597		924
598	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
599	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
600	of thread-safety). This means you must not block within event callbacks,	927	of reentrancy). This means you must not block within event callbacks,
601	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
602	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.
603		935
604	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
605	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
606	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
607	disk, for example.	939	disk, for example.
608		940
609	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
610	creating event callbacks that want to block.	942	creating event callbacks that want to block.
611		943
612	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
613	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
614	there is no reason to use C<unblock_sub>.	946	no reason to use C<unblock_sub>.
		947
		948	Note that you also need to use C<unblock_sub> for any other callbacks that
		949	are indirectly executed by any C-based event loop. For example, when you
		950	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		951	provides callbacks that are the result of some event callback, then you
		952	must not block either, or use C<unblock_sub>.
615		953
616	=cut	954	=cut
617		955
618	our @unblock_queue;	956	our @unblock_queue;
619		957
…		…
622	# return immediately and can be reused) and because we cannot cede	960	# return immediately and can be reused) and because we cannot cede
623	# inside an event callback.	961	# inside an event callback.
624	our $unblock_scheduler = new Coro sub {	962	our $unblock_scheduler = new Coro sub {
625	while () {	963	while () {
626	while (my $cb = pop @unblock_queue) {	964	while (my $cb = pop @unblock_queue) {
627	# this is an inlined copy of async_pool	965	&async_pool (@$cb);
628	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
629		966
630	$coro->{_invoke} = $cb;
631	$coro->ready;
632	cede; # for short-lived callbacks, this reduces pressure on the coro pool	967	# for short-lived callbacks, this reduces pressure on the coro pool
		968	# as the chance is very high that the async_poll coro will be back
		969	# in the idle state when cede returns
		970	cede;
633	}	971	}
634	schedule; # sleep well	972	schedule; # sleep well
635	}	973	}
636	};	974	};
637	$unblock_scheduler->desc ("[unblock_sub scheduler]");	975	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
638		976
639	sub unblock_sub(&) {	977	sub unblock_sub(&) {
640	my $cb = shift;	978	my $cb = shift;
641		979
642	sub {	980	sub {
643	unshift @unblock_queue, [$cb, @_];	981	unshift @unblock_queue, [$cb, @_];
644	$unblock_scheduler->ready;	982	$unblock_scheduler->ready;
645	}	983	}
646	}	984	}
647		985
		986	=item $cb = rouse_cb
		987
		988	Create and return a "rouse callback". That's a code reference that,
		989	when called, will remember a copy of its arguments and notify the owner
		990	coro of the callback.
		991
		992	See the next function.
		993
		994	=item @args = rouse_wait [$cb]
		995
		996	Wait for the specified rouse callback (or the last one that was created in
		997	this coro).
		998
		999	As soon as the callback is invoked (or when the callback was invoked
		1000	before C<rouse_wait>), it will return the arguments originally passed to
		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.
		1004
		1005	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		1006
648	=back	1007	=back
649		1008
650	=cut	1009	=cut
651		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
652	1;	1025	1;
653		1026
		1027	=head1 HOW TO WAIT FOR A CALLBACK
		1028
		1029	It is very common for a coro to wait for some callback to be
		1030	called. This occurs naturally when you use coro in an otherwise
		1031	event-based program, or when you use event-based libraries.
		1032
		1033	These typically register a callback for some event, and call that callback
		1034	when the event occured. In a coro, however, you typically want to
		1035	just wait for the event, simplyifying things.
		1036
		1037	For example C<< AnyEvent->child >> registers a callback to be called when
		1038	a specific child has exited:
		1039
		1040	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		1041
		1042	But from within a coro, you often just want to write this:
		1043
		1044	my $status = wait_for_child $pid;
		1045
		1046	Coro offers two functions specifically designed to make this easy,
		1047	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		1048
		1049	The first function, C<rouse_cb>, generates and returns a callback that,
		1050	when invoked, will save its arguments and notify the coro that
		1051	created the callback.
		1052
		1053	The second function, C<rouse_wait>, waits for the callback to be called
		1054	(by calling C<schedule> to go to sleep) and returns the arguments
		1055	originally passed to the callback.
		1056
		1057	Using these functions, it becomes easy to write the C<wait_for_child>
		1058	function mentioned above:
		1059
		1060	sub wait_for_child($) {
		1061	my ($pid) = @_;
		1062
		1063	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		1064
		1065	my ($rpid, $rstatus) = Coro::rouse_wait;
		1066	$rstatus
		1067	}
		1068
		1069	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		1070	you can roll your own, using C<schedule>:
		1071
		1072	sub wait_for_child($) {
		1073	my ($pid) = @_;
		1074
		1075	# store the current coro in $current,
		1076	# and provide result variables for the closure passed to ->child
		1077	my $current = $Coro::current;
		1078	my ($done, $rstatus);
		1079
		1080	# pass a closure to ->child
		1081	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		1082	$rstatus = $_[1]; # remember rstatus
		1083	$done = 1; # mark $rstatus as valud
		1084	});
		1085
		1086	# wait until the closure has been called
		1087	schedule while !$done;
		1088
		1089	$rstatus
		1090	}
		1091
		1092
654	=head1 BUGS/LIMITATIONS	1093	=head1 BUGS/LIMITATIONS
655		1094
		1095	=over 4
		1096
		1097	=item fork with pthread backend
		1098
		1099	When Coro is compiled using the pthread backend (which isn't recommended
		1100	but required on many BSDs as their libcs are completely broken), then
		1101	coro will not survive a fork. There is no known workaround except to
		1102	fix your libc and use a saner backend.
		1103
		1104	=item perl process emulation ("threads")
		1105
656	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
657	module from the same thread (this requirement might be removed in the	1107	module from the first thread (this requirement might be removed in the
658	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
659	this). I recommend disabling thread support and using processes, as this	1109	this). I recommend disabling thread support and using processes, as having
660	is much faster and uses less memory.	1110	the windows process emulation enabled under unix roughly halves perl
		1111	performance, even when not used.
		1112
		1113	=item coro switching is not signal safe
		1114
		1115	You must not switch to another coro from within a signal handler (only
		1116	relevant with %SIG - most event libraries provide safe signals), I<unless>
		1117	you are sure you are not interrupting a Coro function.
		1118
		1119	That means you I<MUST NOT> call any function that might "block" the
		1120	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		1121	anything that calls those. Everything else, including calling C<ready>,
		1122	works.
		1123
		1124	=back
		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.
661		1187
662	=head1 SEE ALSO	1188	=head1 SEE ALSO
663		1189
664	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>.
665		1191
666	Debugging: L<Coro::Debug>.	1192	Debugging: L<Coro::Debug>.
667		1193
668	Support/Utility: L<Coro::Specific>, L<Coro::Util>.	1194	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
669		1195
670	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.	1196	Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
		1197	L<Coro::SemaphoreSet>, L<Coro::RWLock>.
671		1198
672	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.	1199	I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
673		1200
674	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.	1201	Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
		1202	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
		1203	L<Coro::Select>.
675		1204
676	XS API: L<Coro::MakeMaker>.	1205	XS API: L<Coro::MakeMaker>.
677		1206
678	Low level Configuration, Coroutine Environment: L<Coro::State>.	1207	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
679		1208
680	=head1 AUTHOR	1209	=head1 AUTHOR
681		1210
682	Marc Lehmann <schmorp@schmorp.de>	1211	Marc Lehmann <schmorp@schmorp.de>
683	http://home.schmorp.de/	1212	http://home.schmorp.de/

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Revision 1.293 by root, Sat Apr 30 05:20:03 2011 UTC