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

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Revision 1.226 by root, Wed Nov 19 16:01:32 2008 UTC vs.
Revision 1.286 by root, Sat Feb 19 04:34:59 2011 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	Coro - coroutine process abstraction	3	Coro - the only real threads in perl
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use Coro;	7	use Coro;
8		8
11	print "2\n";	11	print "2\n";
12	cede; # yield back to main	12	cede; # yield back to main
13	print "4\n";	13	print "4\n";
14	};	14	};
15	print "1\n";	15	print "1\n";
16	cede; # yield to coroutine	16	cede; # yield to coro
17	print "3\n";	17	print "3\n";
18	cede; # and again	18	cede; # and again
19		19
20	# use locking	20	# use locking
21	use Coro::Semaphore;	21	use Coro::Semaphore;
…		…
26	$locked = 1;	26	$locked = 1;
27	$lock->up;	27	$lock->up;
28		28
29	=head1 DESCRIPTION	29	=head1 DESCRIPTION
30		30
31	This module collection manages coroutines. Coroutines are similar to	31	For a tutorial-style introduction, please read the L<Coro::Intro>
32	threads but don't (in general) run in parallel at the same time even	32	manpage. This manpage mainly contains reference information.
33	on SMP machines. The specific flavor of coroutine used in this module
34	also guarantees you that it will not switch between coroutines unless
35	necessary, at easily-identified points in your program, so locking and
36	parallel access are rarely an issue, making coroutine programming much
37	safer and easier than threads programming.
38		33
39	Unlike a normal perl program, however, coroutines allow you to have	34	This module collection manages continuations in general, most often in
40	multiple running interpreters that share data, which is especially useful	35	the form of cooperative threads (also called coros, or simply "coro"
41	to code pseudo-parallel processes and for event-based programming, such as	36	in the documentation). They are similar to kernel threads but don't (in
42	multiple HTTP-GET requests running concurrently. See L<Coro::AnyEvent> to	37	general) run in parallel at the same time even on SMP machines. The
43	learn more.	38	specific flavor of thread offered by this module also guarantees you that
		39	it will not switch between threads unless necessary, at easily-identified
		40	points in your program, so locking and parallel access are rarely an
		41	issue, making thread programming much safer and easier than using other
		42	thread models.
44		43
45	Coroutines are also useful because Perl has no support for threads (the so	44	Unlike the so-called "Perl threads" (which are not actually real threads
46	called "threads" that perl offers are nothing more than the (bad) process	45	but only the windows process emulation (see section of same name for
47	emulation coming from the Windows platform: On standard operating systems	46	more details) ported to UNIX, and as such act as processes), Coro
48	they serve no purpose whatsoever, except by making your programs slow and	47	provides a full shared address space, which makes communication between
49	making them use a lot of memory. Best disable them when building perl, or	48	threads very easy. And coro threads are fast, too: disabling the Windows
50	aks your software vendor/distributor to do it for you).	49	process emulation code in your perl and using Coro can easily result in
		50	a two to four times speed increase for your programs. A parallel matrix
		51	multiplication benchmark (very communication-intensive) runs over 300
		52	times faster on a single core than perls pseudo-threads on a quad core
		53	using all four cores.
51		54
		55	Coro achieves that by supporting multiple running interpreters that share
		56	data, which is especially useful to code pseudo-parallel processes and
		57	for event-based programming, such as multiple HTTP-GET requests running
		58	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
		59	into an event-based environment.
		60
52	In this module, coroutines are defined as "callchain + lexical variables +	61	In this module, a thread is defined as "callchain + lexical variables +
53	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,	62	some package variables + C stack), that is, a thread has its own callchain,
54	its own set of lexicals and its own set of perls most important global	63	its own set of lexicals and its own set of perls most important global
55	variables (see L<Coro::State> for more configuration).	64	variables (see L<Coro::State> for more configuration and background info).
		65
		66	See also the C<SEE ALSO> section at the end of this document - the Coro
		67	module family is quite large.
		68
		69	=head1 CORO THREAD LIFE CYCLE
		70
		71	During the long and exciting (or not) life of a coro thread, it goes
		72	through a number of states:
		73
		74	=over 4
		75
		76	=item 1. Creation
		77
		78	The first thing in the life of a coro thread is it's creation -
		79	obviously. The typical way to create a thread is to call the C<async
		80	BLOCK> function:
		81
		82	async {
		83	# thread code goes here
		84	};
		85
		86	You can also pass arguments, which are put in C<@_>:
		87
		88	async {
		89	print $_[1]; # prints 2
		90	} 1, 2, 3;
		91
		92	This creates a new coro thread and puts it into the ready queue, meaning
		93	it will run as soon as the CPU is free for it.
		94
		95	C<async> will return a coro object - you can store this for future
		96	reference or ignore it, the thread itself will keep a reference to it's
		97	thread object - threads are alive on their own.
		98
		99	Another way to create a thread is to call the C<new> constructor with a
		100	code-reference:
		101
		102	new Coro sub {
		103	# thread code goes here
		104	}, @optional_arguments;
		105
		106	This is quite similar to calling C<async>, but the important difference is
		107	that the new thread is not put into the ready queue, so the thread will
		108	not run until somebody puts it there. C<async> is, therefore, identical to
		109	this sequence:
		110
		111	my $coro = new Coro sub {
		112	# thread code goes here
		113	};
		114	$coro->ready;
		115	return $coro;
		116
		117	=item 2. Startup
		118
		119	When a new coro thread is created, only a copy of the code reference
		120	and the arguments are stored, no extra memory for stacks and so on is
		121	allocated, keeping the coro thread in a low-memory state.
		122
		123	Only when it actually starts executing will all the resources be finally
		124	allocated.
		125
		126	The optional arguments specified at coro creation are available in C<@_>,
		127	similar to function calls.
		128
		129	=item 3. Running / Blocking
		130
		131	A lot can happen after the coro thread has started running. Quite usually,
		132	it will not run to the end in one go (because you could use a function
		133	instead), but it will give up the CPU regularly because it waits for
		134	external events.
		135
		136	As long as a coro thread runs, it's coro object is available in the global
		137	variable C<$Coro::current>.
		138
		139	The low-level way to give up the CPU is to call the scheduler, which
		140	selects a new coro thread to run:
		141
		142	Coro::schedule;
		143
		144	Since running threads are not in the ready queue, calling the scheduler
		145	without doing anything else will block the coro thread forever - you need
		146	to arrange either for the coro to put woken up (readied) by some other
		147	event or some other thread, or you can put it into the ready queue before
		148	scheduling:
		149
		150	# this is exactly what Coro::cede does
		151	$Coro::current->ready;
		152	Coro::schedule;
		153
		154	All the higher-level synchronisation methods (Coro::Semaphore,
		155	Coro::rouse_*...) are actually implemented via C<< ->ready >> and C<<
		156	Coro::schedule >>.
		157
		158	While the coro thread is running it also might get assigned a C-level
		159	thread, or the C-level thread might be unassigned from it, as the Coro
		160	runtime wishes. A C-level thread needs to be assigned when your perl
		161	thread calls into some C-level function and that function in turn calls
		162	perl and perl then wants to switch coroutines. This happens most often
		163	when you run an event loop and block in the callback, or when perl
		164	itself calls some function such as C<AUTOLOAD> or methods via the C<tie>
		165	mechanism.
		166
		167	=item 4. Termination
		168
		169	Many threads actually terminate after some time. There are a number of
		170	ways to terminate a coro thread, the simplest is returning from the
		171	top-level code reference:
		172
		173	async {
		174	# after returning from here, the coro thread is terminated
		175	};
		176
		177	async {
		178	return if 0.5 < rand; # terminate a little earlier, maybe
		179	print "got a chance to print this\n";
		180	# or here
		181	};
		182
		183	Any values returned from the coroutine can be recovered using C<< ->join
		184	>>:
		185
		186	my $coro = async {
		187	"hello, world\n" # return a string
		188	};
		189
		190	my $hello_world = $coro->join;
		191
		192	print $hello_world;
		193
		194	Another way to terminate is to call C<< Coro::terminate >>, which at any
		195	subroutine call nesting level:
		196
		197	async {
		198	Coro::terminate "return value 1", "return value 2";
		199	};
		200
		201	And yet another way is to C<< ->cancel >> 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
56		314
57	=cut	315	=cut
58		316
59	package Coro;	317	package Coro;
60		318
61	use strict qw(vars subs);	319	use common::sense;
62	no warnings "uninitialized";	320
		321	use Carp ();
		322
		323	use Guard ();
63		324
64	use Coro::State;	325	use Coro::State;
65		326
66	use base qw(Coro::State Exporter);	327	use base qw(Coro::State Exporter);
67		328
68	our $idle; # idle handler	329	our $idle; # idle handler
69	our $main; # main coroutine	330	our $main; # main coro
70	our $current; # current coroutine	331	our $current; # current coro
71		332
72	our $VERSION = 5.0;	333	our $VERSION = 5.26;
73		334
74	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	335	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
75	our %EXPORT_TAGS = (	336	our %EXPORT_TAGS = (
76	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	337	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
77	);	338	);
78	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	339	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
79		340
		341	=head1 GLOBAL VARIABLES
		342
80	=over 4	343	=over 4
81		344
82	=item $Coro::main	345	=item $Coro::main
83		346
84	This variable stores the coroutine object that represents the main	347	This variable stores the Coro object that represents the main
85	program. While you cna C<ready> it and do most other things you can do to	348	program. While you cna C<ready> it and do most other things you can do to
86	coroutines, it is mainly useful to compare again C<$Coro::current>, to see	349	coro, it is mainly useful to compare again C<$Coro::current>, to see
87	whether you are running in the main program or not.	350	whether you are running in the main program or not.
88		351
89	=cut	352	=cut
90		353
91	# $main is now being initialised by Coro::State	354	# $main is now being initialised by Coro::State
92		355
93	=item $Coro::current	356	=item $Coro::current
94		357
95	The coroutine object representing the current coroutine (the last	358	The Coro object representing the current coro (the last
96	coroutine that the Coro scheduler switched to). The initial value is	359	coro that the Coro scheduler switched to). The initial value is
97	C<$Coro::main> (of course).	360	C<$Coro::main> (of course).
98		361
99	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
100	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
101	not otherwise modify the variable itself.	364	not otherwise modify the variable itself.
102		365
103	=cut	366	=cut
104		367
105	sub current() { $current } # [DEPRECATED]	368	sub current() { $current } # [DEPRECATED]
106		369
107	=item $Coro::idle	370	=item $Coro::idle
108		371
109	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
110	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
111	pretty low-level functionality.	374	pretty low-level functionality.
112		375
113	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
114	finds no ready coroutines to run. The default implementation prints	377	there are no other ready threads (without invoking any ready hooks).
115	"FATAL: deadlock detected" and exits, because the program has no other way
116	to continue.
117		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
118	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
119	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
120	coroutine so the scheduler can run it.	384	coro so the scheduler can run it.
121		385
122	Note that the callback I<must not>, under any circumstances, block
123	the current coroutine. Normally, this is achieved by having an "idle
124	coroutine" that calls the event loop and then blocks again, and then
125	readying that coroutine in the idle handler.
126
127	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this	386	See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
128	technique.
129		387
130	Please note that if your callback recursively invokes perl (e.g. for event
131	handlers), then it must be prepared to be called recursively itself.
132
133	=cut	388	=cut
134		389
135	$idle = sub {	390	# \|\|= because other modules could have provided their own by now
136	require Carp;	391	$idle \|\|= new Coro sub {
137	Carp::croak ("FATAL: deadlock detected");	392	require Coro::Debug;
		393	die "FATAL: deadlock detected.\n"
		394	. Coro::Debug::ps_listing ();
138	};	395	};
139		396
140	sub _cancel {
141	my ($self) = @_;
142
143	# free coroutine data and mark as destructed
144	$self->_destroy
145	or return;
146
147	# call all destruction callbacks
148	$_->(@{$self->{_status}})
149	for @{ delete $self->{_on_destroy} \|\| [] };
150	}
151
152	# this coroutine is necessary because a coroutine	397	# this coro is necessary because a coro
153	# cannot destroy itself.	398	# cannot destroy itself.
154	our @destroy;	399	our @destroy;
155	our $manager;	400	our $manager;
156		401
157	$manager = new Coro sub {	402	$manager = new Coro sub {
158	while () {	403	while () {
159	(shift @destroy)->_cancel	404	Coro::State::cancel shift @destroy
160	while @destroy;	405	while @destroy;
161		406
162	&schedule;	407	&schedule;
163	}	408	}
164	};	409	};
165	$manager->{desc} = "[coro manager]";	410	$manager->{desc} = "[coro manager]";
166	$manager->prio (PRIO_MAX);	411	$manager->prio (PRIO_MAX);
167		412
168	=back	413	=back
169		414
170	=head2 SIMPLE COROUTINE CREATION	415	=head1 SIMPLE CORO CREATION
171		416
172	=over 4	417	=over 4
173		418
174	=item async { ... } [@args...]	419	=item async { ... } [@args...]
175		420
176	Create a new coroutine and return it's coroutine object (usually	421	Create a new coro and return its Coro object (usually
177	unused). The coroutine will be put into the ready queue, so	422	unused). The coro will be put into the ready queue, so
178	it will start running automatically on the next scheduler run.	423	it will start running automatically on the next scheduler run.
179		424
180	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
181	coroutine. When it returns argument returns the coroutine is automatically	426	coro. When it returns argument returns the coro is automatically
182	terminated.	427	terminated.
183		428
184	The remaining arguments are passed as arguments to the closure.	429	The remaining arguments are passed as arguments to the closure.
185		430
186	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
187	environment in which coroutines are executed.	432	environment in which coro are executed.
188		433
189	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
190	the coroutine. Likewise, when the coroutine dies, the program will exit,	435	the coro. Likewise, when the coro dies, the program will exit,
191	just as it would in the main program.	436	just as it would in the main program.
192		437
193	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
194	simply avoid dieing (by use of C<eval>).	439	simply avoid dieing (by use of C<eval>).
195		440
196	Example: Create a new coroutine that just prints its arguments.	441	Example: Create a new coro that just prints its arguments.
197		442
198	async {	443	async {
199	print "@_\n";	444	print "@_\n";
200	} 1,2,3,4;	445	} 1,2,3,4;
201		446
202	=cut
203
204	sub async(&@) {
205	my $coro = new Coro @_;
206	$coro->ready;
207	$coro
208	}
209
210	=item async_pool { ... } [@args...]	447	=item async_pool { ... } [@args...]
211		448
212	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
213	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
214	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
215	or bad :).	452	or bad :).
216		453
217	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
218	a completly 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
219	quick successsion, use C<async_pool>, not C<async>.	456	coros in quick successsion, use C<async_pool>, not C<async>.
220		457
221	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
222	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
223	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>
224	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,
225	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
226	exceptional case).	463	exceptional case).
227		464
228	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
229	disabled, the description will be reset and the default output filehandle	466	disabled, the description will be reset and the default output filehandle
230	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
231	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
232	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
233	simply done by using local as in: C<< local $/ >>.	470	simply done by using local as in: C<< local $/ >>.
234		471
235	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
236	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
237	coros as required.	474	coros as required.
238		475
239	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
240	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
241	{ 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
242	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
243	(adjustable via $Coro::POOL_RSS) it will also be destroyed.	480	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
244		481
245	=cut	482	=cut
246		483
247	our $POOL_SIZE = 8;	484	our $POOL_SIZE = 8;
248	our $POOL_RSS = 16 * 1024;	485	our $POOL_RSS = 32 * 1024;
249	our @async_pool;	486	our @async_pool;
250		487
251	sub pool_handler {	488	sub pool_handler {
252	my $cb;
253
254	while () {	489	while () {
255	eval {	490	eval {
256	while () {	491	&{&_pool_handler} while 1;
257	_pool_1 $cb;
258	&$cb;
259	_pool_2 $cb;
260	&schedule;
261	}
262	};	492	};
263		493
264	if ($@) {
265	last if $@ eq "\3async_pool terminate\2\n";
266	warn $@;	494	warn $@ if $@;
267	}
268	}	495	}
269	}	496	}
270		497
271	sub async_pool(&@) {
272	# this is also inlined into the unblock_scheduler
273	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
274
275	$coro->{_invoke} = [@_];
276	$coro->ready;
277
278	$coro
279	}
280
281	=back	498	=back
282		499
283	=head2 STATIC METHODS	500	=head1 STATIC METHODS
284		501
285	Static methods are actually functions that operate on the current coroutine.	502	Static methods are actually functions that implicitly operate on the
		503	current coro.
286		504
287	=over 4	505	=over 4
288		506
289	=item schedule	507	=item schedule
290		508
291	Calls the scheduler. The scheduler will find the next coroutine that is	509	Calls the scheduler. The scheduler will find the next coro that is
292	to be run from the ready queue and switches to it. The next coroutine	510	to be run from the ready queue and switches to it. The next coro
293	to be run is simply the one with the highest priority that is longest	511	to be run is simply the one with the highest priority that is longest
294	in its ready queue. If there is no coroutine ready, it will clal the	512	in its ready queue. If there is no coro ready, it will call the
295	C<$Coro::idle> hook.	513	C<$Coro::idle> hook.
296		514
297	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
298	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
299	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 >>,
300	thus waking you up.	518	thus waking you up.
301		519
302	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
303	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
304	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
305	>> 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
306	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,
307	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
308	status in a variable.	526	status in a variable.
309		527
310	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.
311		529
312	=item cede	530	=item cede
313		531
314	"Cede" to other coroutines. This function puts the current coroutine into	532	"Cede" to other coros. This function puts the current coro into
315	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
316	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
317	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
318	resumed.	536	resumed.
319		537
320	This function is often called C<yield> in other languages.	538	This function is often called C<yield> in other languages.
321		539
322	=item Coro::cede_notself	540	=item Coro::cede_notself
323		541
324	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>
325	coroutine, regardless of priority. This is useful sometimes to ensure	543	coro, regardless of priority. This is useful sometimes to ensure
326	progress is made.	544	progress is made.
327		545
328	=item terminate [arg...]	546	=item terminate [arg...]
329		547
330	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
331		635
332	=item killall	636	=item killall
333		637
334	Kills/terminates/cancels all coroutines except the currently running	638	Kills/terminates/cancels all coros except the currently running one.
335	one. This is useful after a fork, either in the child or the parent, as
336	usually only one of them should inherit the running coroutines.
337		639
338	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
339	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
340	program calls this function, there will be some one-time resource leak.	643	calls this function, there will be some one-time resource leak.
341		644
342	=cut	645	=cut
343
344	sub terminate {
345	$current->{_status} = [@_];
346	push @destroy, $current;
347	$manager->ready;
348	do { &schedule } while 1;
349	}
350		646
351	sub killall {	647	sub killall {
352	for (Coro::State::list) {	648	for (Coro::State::list) {
353	$_->cancel	649	$_->cancel
354	if $_ != $current && UNIVERSAL::isa $_, "Coro";	650	if $_ != $current && UNIVERSAL::isa $_, "Coro";
355	}	651	}
356	}	652	}
357		653
358	=back	654	=back
359		655
360	=head2 COROUTINE METHODS	656	=head1 CORO OBJECT METHODS
361		657
362	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
363	them).	659	them).
364		660
365	=over 4	661	=over 4
366		662
367	=item new Coro \&sub [, @args...]	663	=item new Coro \&sub [, @args...]
368		664
369	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
370	automatically terminates as if C<terminate> with the returned values were	666	automatically terminates as if C<terminate> with the returned values were
371	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
372	queue by calling the ready method.	668	queue by calling the ready method.
373		669
374	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
375	coroutine environment.	671	coro environment.
376		672
377	=cut	673	=cut
378		674
379	sub _terminate {	675	sub _coro_run {
380	terminate &{+shift};	676	terminate &{+shift};
381	}	677	}
382		678
383	=item $success = $coroutine->ready	679	=item $success = $coro->ready
384		680
385	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
386	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
387	the ready queue, do nothing and return false.	683	the ready queue, do nothing and return false.
388		684
389	This ensures that the scheduler will resume this coroutine automatically	685	This ensures that the scheduler will resume this coro automatically
390	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
391	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.
392		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
393	=item $is_ready = $coroutine->is_ready	714	=item $is_ready = $coro->is_ready
394		715
395	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.
396		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
397	=item $coroutine->cancel (arg...)	730	=item $coro->cancel (arg...)
398		731
399	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
400	status (default: the empty list). Never returns if the coroutine is the	733	status (default: the empty list). Never returns if the Coro is the
401	current coroutine.	734	current Coro.
402		735
403	=cut	736	=cut
404		737
405	sub cancel {	738	sub cancel {
406	my $self = shift;	739	my $self = shift;
407		740
408	if ($current == $self) {	741	if ($current == $self) {
409	terminate @_;	742	terminate @_;
410	} else {	743	} else {
411	$self->{_status} = [@_];	744	$self->{_status} = [@_];
412	$self->_cancel;	745	Coro::State::cancel $self;
413	}	746	}
414	}	747	}
415		748
		749	=item $coro->schedule_to
		750
		751	Puts the current coro to sleep (like C<Coro::schedule>), but instead
		752	of continuing with the next coro from the ready queue, always switch to
		753	the given coro object (regardless of priority etc.). The readyness
		754	state of that coro isn't changed.
		755
		756	This is an advanced method for special cases - I'd love to hear about any
		757	uses for this one.
		758
		759	=item $coro->cede_to
		760
		761	Like C<schedule_to>, but puts the current coro into the ready
		762	queue. This has the effect of temporarily switching to the given
		763	coro, and continuing some time later.
		764
		765	This is an advanced method for special cases - I'd love to hear about any
		766	uses for this one.
		767
416	=item $coroutine->throw ([$scalar])	768	=item $coro->throw ([$scalar])
417		769
418	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
419	inside the coroutine at the next convenient point in time. Otherwise	771	inside the coro at the next convenient point in time. Otherwise
420	clears the exception object.	772	clears the exception object.
421		773
422	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
423	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
424	>>, C<< Coro::Handle->readable >> and so on. Most of these functions	776	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
…		…
426		778
427	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
428	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
429	(unlike with C<die>).	781	(unlike with C<die>).
430		782
431	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
432	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
433	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
434	program.	786	program.
435		787
436	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
437	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).
438		790
439	=item $coroutine->join	791	=item $coro->join
440		792
441	Wait until the coroutine terminates and return any values given to the	793	Wait until the coro terminates and return any values given to the
442	C<terminate> or C<cancel> functions. C<join> can be called concurrently	794	C<terminate> or C<cancel> functions. C<join> can be called concurrently
443	from multiple coroutines, and all will be resumed and given the status	795	from multiple coro, and all will be resumed and given the status
444	return once the C<$coroutine> terminates.	796	return once the C<$coro> terminates.
445		797
446	=cut	798	=cut
447		799
448	sub join {	800	sub join {
449	my $self = shift;	801	my $self = shift;
…		…
460	}	812	}
461		813
462	wantarray ? @{$self->{_status}} : $self->{_status}[0];	814	wantarray ? @{$self->{_status}} : $self->{_status}[0];
463	}	815	}
464		816
465	=item $coroutine->on_destroy (\&cb)	817	=item $coro->on_destroy (\&cb)
466		818
467	Registers a callback that is called when this coroutine gets destroyed,	819	Registers a callback that is called when this coro thread gets destroyed,
468	but before it is joined. The callback gets passed the terminate arguments,	820	but before it is joined. The callback gets passed the terminate arguments,
469	if any, and I<must not> die, under any circumstances.	821	if any, and I<must not> die, under any circumstances.
470		822
		823	There can be any number of C<on_destroy> callbacks per coro.
		824
471	=cut	825	=cut
472		826
473	sub on_destroy {	827	sub on_destroy {
474	my ($self, $cb) = @_;	828	my ($self, $cb) = @_;
475		829
476	push @{ $self->{_on_destroy} }, $cb;	830	push @{ $self->{_on_destroy} }, $cb;
477	}	831	}
478		832
479	=item $oldprio = $coroutine->prio ($newprio)	833	=item $oldprio = $coro->prio ($newprio)
480		834
481	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
482	coroutine. Higher priority coroutines get run before lower priority	836	coro thread. Higher priority coro get run before lower priority
483	coroutines. Priorities are small signed integers (currently -4 .. +3),	837	coros. Priorities are small signed integers (currently -4 .. +3),
484	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
485	to get then):	839	to get then):
486		840
487	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
488	3 > 1 > 0 > -1 > -3 > -4	842	3 > 1 > 0 > -1 > -3 > -4
489		843
490	# set priority to HIGH	844	# set priority to HIGH
491	current->prio(PRIO_HIGH);	845	current->prio (PRIO_HIGH);
492		846
493	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
494	existing coroutine.	848	existing coro.
495		849
496	Changing the priority of the current coroutine will take effect immediately,	850	Changing the priority of the current coro will take effect immediately,
497	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)
498	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
499	coroutine). This is a bug that will be fixed in some future version.	853	bug that will be fixed in some future version.
500		854
501	=item $newprio = $coroutine->nice ($change)	855	=item $newprio = $coro->nice ($change)
502		856
503	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.
504	higher values mean lower priority, just as in unix).	858	higher values mean lower priority, just as in UNIX's nice command).
505		859
506	=item $olddesc = $coroutine->desc ($newdesc)	860	=item $olddesc = $coro->desc ($newdesc)
507		861
508	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
509	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
510	coroutine.	864	coro.
511		865
512	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
513	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	}
514		879
515	=cut	880	=cut
516		881
517	sub desc {	882	sub desc {
518	my $old = $_[0]{desc};	883	my $old = $_[0]{desc};
519	$_[0]{desc} = $_[1] if @_ > 1;	884	$_[0]{desc} = $_[1] if @_ > 1;
520	$old;	885	$old;
521	}	886	}
522		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
523	=back	893	=back
524		894
525	=head2 GLOBAL FUNCTIONS	895	=head1 GLOBAL FUNCTIONS
526		896
527	=over 4	897	=over 4
528		898
529	=item Coro::nready	899	=item Coro::nready
530		900
531	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,
532	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
533	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
534	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>
535	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
536	coroutines.	906	coro.
537		907
538	=item my $guard = Coro::guard { ... }	908	=item my $guard = Coro::guard { ... }
539		909
540	This creates and returns a guard object. Nothing happens until the object	910	This function still exists, but is deprecated. Please use the
541	gets destroyed, in which case the codeblock given as argument will be	911	C<Guard::guard> function instead.
542	executed. This is useful to free locks or other resources in case of a
543	runtime error or when the coroutine gets canceled, as in both cases the
544	guard block will be executed. The guard object supports only one method,
545	C<< ->cancel >>, which will keep the codeblock from being executed.
546		912
547	Example: set some flag and clear it again when the coroutine gets canceled
548	or the function returns:
549
550	sub do_something {
551	my $guard = Coro::guard { $busy = 0 };
552	$busy = 1;
553
554	# do something that requires $busy to be true
555	}
556
557	=cut	913	=cut
558		914
559	sub guard(&) {	915	BEGIN { *guard = \&Guard::guard }
560	bless \(my $cb = $_[0]), "Coro::guard"
561	}
562
563	sub Coro::guard::cancel {
564	${$_[0]} = sub { };
565	}
566
567	sub Coro::guard::DESTROY {
568	${$_[0]}->();
569	}
570
571		916
572	=item unblock_sub { ... }	917	=item unblock_sub { ... }
573		918
574	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,
575	returning a new coderef. Unblocking means that calling the new coderef	920	returning a new coderef. Unblocking means that calling the new coderef
576	will return immediately without blocking, returning nothing, while the	921	will return immediately without blocking, returning nothing, while the
577	original code ref will be called (with parameters) from within another	922	original code ref will be called (with parameters) from within another
578	coroutine.	923	coro.
579		924
580	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
581	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
582	of thread-safety). This means you must not block within event callbacks,	927	of reentrancy). This means you must not block within event callbacks,
583	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
584	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.
585		935
586	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
587	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
588	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
589	disk, for example.	939	disk, for example.
590		940
591	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
592	creating event callbacks that want to block.	942	creating event callbacks that want to block.
593		943
594	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
595	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
596	there is no reason to use C<unblock_sub>.	946	no reason to use C<unblock_sub>.
597		947
598	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
599	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
600	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
601	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
…		…
610	# return immediately and can be reused) and because we cannot cede	960	# return immediately and can be reused) and because we cannot cede
611	# inside an event callback.	961	# inside an event callback.
612	our $unblock_scheduler = new Coro sub {	962	our $unblock_scheduler = new Coro sub {
613	while () {	963	while () {
614	while (my $cb = pop @unblock_queue) {	964	while (my $cb = pop @unblock_queue) {
615	# this is an inlined copy of async_pool	965	&async_pool (@$cb);
616	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
617		966
618	$coro->{_invoke} = $cb;
619	$coro->ready;
620	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;
621	}	971	}
622	schedule; # sleep well	972	schedule; # sleep well
623	}	973	}
624	};	974	};
625	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";	975	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
…		…
631	unshift @unblock_queue, [$cb, @_];	981	unshift @unblock_queue, [$cb, @_];
632	$unblock_scheduler->ready;	982	$unblock_scheduler->ready;
633	}	983	}
634	}	984	}
635		985
636	=item $cb = Coro::rouse_cb	986	=item $cb = rouse_cb
637		987
638	Create and return a "rouse callback". That's a code reference that, when	988	Create and return a "rouse callback". That's a code reference that,
639	called, will save its arguments and notify the owner coroutine of the	989	when called, will remember a copy of its arguments and notify the owner
640	callback.	990	coro of the callback.
641		991
642	See the next function.	992	See the next function.
643		993
644	=item @args = Coro::rouse_wait [$cb]	994	=item @args = rouse_wait [$cb]
645		995
646	Wait for the specified rouse callback (or the last one tht was created in	996	Wait for the specified rouse callback (or the last one that was created in
647	this coroutine).	997	this coro).
648		998
649	As soon as the callback is invoked (or when the calback was invoked before	999	As soon as the callback is invoked (or when the callback was invoked
650	C<rouse_wait>), it will return a copy of the arguments originally passed	1000	before C<rouse_wait>), it will return the arguments originally passed to
651	to the rouse callback.	1001	the rouse callback. In scalar context, that means you get the I<last>
		1002	argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
		1003	statement at the end.
652		1004
653	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.
654		1006
655	=back	1007	=back
656		1008
657	=cut	1009	=cut
658		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
659	1;	1025	1;
660		1026
661	=head1 HOW TO WAIT FOR A CALLBACK	1027	=head1 HOW TO WAIT FOR A CALLBACK
662		1028
663	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
664	called. This occurs naturally when you use coroutines in an otherwise	1030	called. This occurs naturally when you use coro in an otherwise
665	event-based program, or when you use event-based libraries.	1031	event-based program, or when you use event-based libraries.
666		1032
667	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
668	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
669	just wait for the event, simplyifying things.	1035	just wait for the event, simplyifying things.
670		1036
671	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
672	a specific child has exited:	1038	a specific child has exited:
673		1039
674	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });	1040	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
675		1041
676	But from withina coroutine, you often just want to write this:	1042	But from within a coro, you often just want to write this:
677		1043
678	my $status = wait_for_child $pid;	1044	my $status = wait_for_child $pid;
679		1045
680	Coro offers two functions specifically designed to make this easy,	1046	Coro offers two functions specifically designed to make this easy,
681	C<Coro::rouse_cb> and C<Coro::rouse_wait>.	1047	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
682		1048
683	The first function, C<rouse_cb>, generates and returns a callback that,	1049	The first function, C<rouse_cb>, generates and returns a callback that,
684	when invoked, will save it's arguments and notify the coroutine that	1050	when invoked, will save its arguments and notify the coro that
685	created the callback.	1051	created the callback.
686		1052
687	The second function, C<rouse_wait>, waits for the callback to be called	1053	The second function, C<rouse_wait>, waits for the callback to be called
688	(by calling C<schedule> to go to sleep) and returns the arguments	1054	(by calling C<schedule> to go to sleep) and returns the arguments
689	originally passed to the callback.	1055	originally passed to the callback.
…		…
704	you can roll your own, using C<schedule>:	1070	you can roll your own, using C<schedule>:
705		1071
706	sub wait_for_child($) {	1072	sub wait_for_child($) {
707	my ($pid) = @_;	1073	my ($pid) = @_;
708		1074
709	# store the current coroutine in $current,	1075	# store the current coro in $current,
710	# and provide result variables for the closure passed to ->child	1076	# and provide result variables for the closure passed to ->child
711	my $current = $Coro::current;	1077	my $current = $Coro::current;
712	my ($done, $rstatus);	1078	my ($done, $rstatus);
713		1079
714	# pass a closure to ->child	1080	# pass a closure to ->child
…		…
730		1096
731	=item fork with pthread backend	1097	=item fork with pthread backend
732		1098
733	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
734	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
735	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
736	fix your libc and use a saner backend.	1102	fix your libc and use a saner backend.
737		1103
738	=item perl process emulation ("threads")	1104	=item perl process emulation ("threads")
739		1105
740	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
741	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
742	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
743	this). I recommend disabling thread support and using processes, as having	1109	this). I recommend disabling thread support and using processes, as having
744	the windows process emulation enabled under unix roughly halves perl	1110	the windows process emulation enabled under unix roughly halves perl
745	performance, even when not used.	1111	performance, even when not used.
746		1112
747	=item coroutine switching not signal safe	1113	=item coro switching is not signal safe
748		1114
749	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
750	(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.
751		1118
752	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
753	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or	1120	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
754	anything that calls those. Everything else, including calling C<ready>,	1121	anything that calls those. Everything else, including calling C<ready>,
755	works.	1122	works.
756		1123
757	=back	1124	=back
758		1125
759		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.
		1187
760	=head1 SEE ALSO	1188	=head1 SEE ALSO
761		1189
762	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>.
763		1191
764	Debugging: L<Coro::Debug>.	1192	Debugging: L<Coro::Debug>.
765		1193
766	Support/Utility: L<Coro::Specific>, L<Coro::Util>.	1194	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
767		1195
768	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>.
769		1198
770	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>.
771		1200
772	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>.
773		1204
774	XS API: L<Coro::MakeMaker>.	1205	XS API: L<Coro::MakeMaker>.
775		1206
776	Low level Configuration, Coroutine Environment: L<Coro::State>.	1207	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
777		1208
778	=head1 AUTHOR	1209	=head1 AUTHOR
779		1210
780	Marc Lehmann <schmorp@schmorp.de>	1211	Marc Lehmann <schmorp@schmorp.de>
781	http://home.schmorp.de/	1212	http://home.schmorp.de/

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Revision 1.286 by root, Sat Feb 19 04:34:59 2011 UTC