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

Comparing Coro/Coro.pm (file contents):
Revision 1.239 by root, Mon Nov 24 07:55:28 2008 UTC vs.
Revision 1.337 by root, Sun Oct 4 13:10:22 2015 UTC

…		…
11	print "2\n";	11	print "2\n";
12	cede; # yield back to main	12	cede; # yield back to main
13	print "4\n";	13	print "4\n";
14	};	14	};
15	print "1\n";	15	print "1\n";
16	cede; # yield to coroutine	16	cede; # yield to coro
17	print "3\n";	17	print "3\n";
18	cede; # and again	18	cede; # and again
19		19
20	# use locking	20	# use locking
21	use Coro::Semaphore;
22	my $lock = new Coro::Semaphore;	21	my $lock = new Coro::Semaphore;
23	my $locked;	22	my $locked;
24		23
25	$lock->down;	24	$lock->down;
26	$locked = 1;	25	$locked = 1;
…		…
29	=head1 DESCRIPTION	28	=head1 DESCRIPTION
30		29
31	For a tutorial-style introduction, please read the L<Coro::Intro>	30	For a tutorial-style introduction, please read the L<Coro::Intro>
32	manpage. This manpage mainly contains reference information.	31	manpage. This manpage mainly contains reference information.
33		32
34	This module collection manages continuations in general, most often	33	This module collection manages continuations in general, most often in
35	in the form of cooperative threads (also called coroutines in the	34	the form of cooperative threads (also called coros, or simply "coro"
36	documentation). They are similar to kernel threads but don't (in general)	35	in the documentation). They are similar to kernel threads but don't (in
37	run in parallel at the same time even on SMP machines. The specific flavor	36	general) run in parallel at the same time even on SMP machines. The
38	of thread offered by this module also guarantees you that it will not	37	specific flavor of thread offered by this module also guarantees you that
39	switch between threads unless necessary, at easily-identified points in	38	it will not switch between threads unless necessary, at easily-identified
40	your program, so locking and parallel access are rarely an issue, making	39	points in your program, so locking and parallel access are rarely an
41	thread programming much safer and easier than using other thread models.	40	issue, making thread programming much safer and easier than using other
		41	thread models.
42		42
43	Unlike the so-called "Perl threads" (which are not actually real threads	43	Unlike the so-called "Perl threads" (which are not actually real threads
44	but only the windows process emulation ported to unix), Coro provides a	44	but only the windows process emulation (see section of same name for
		45	more details) ported to UNIX, and as such act as processes), Coro
45	full shared address space, which makes communication between threads	46	provides a full shared address space, which makes communication between
46	very easy. And threads are fast, too: disabling the Windows process	47	threads very easy. And coro threads are fast, too: disabling the Windows
47	emulation code in your perl and using Coro can easily result in a two to	48	process emulation code in your perl and using Coro can easily result in
48	four times speed increase for your programs.	49	a two to four times speed increase for your programs. A parallel matrix
		50	multiplication benchmark (very communication-intensive) runs over 300
		51	times faster on a single core than perls pseudo-threads on a quad core
		52	using all four cores.
49		53
50	Coro achieves that by supporting multiple running interpreters that share	54	Coro achieves that by supporting multiple running interpreters that share
51	data, which is especially useful to code pseudo-parallel processes and	55	data, which is especially useful to code pseudo-parallel processes and
52	for event-based programming, such as multiple HTTP-GET requests running	56	for event-based programming, such as multiple HTTP-GET requests running
53	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro	57	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
54	into an event-based environment.	58	into an event-based environment.
55		59
56	In this module, a thread is defined as "callchain + lexical variables +	60	In this module, a thread is defined as "callchain + lexical variables +
57	@_ + $_ + $@ + $/ + C stack), that is, a thread has its own callchain,	61	some package variables + C stack), that is, a thread has its own callchain,
58	its own set of lexicals and its own set of perls most important global	62	its own set of lexicals and its own set of perls most important global
59	variables (see L<Coro::State> for more configuration and background info).	63	variables (see L<Coro::State> for more configuration and background info).
60		64
61	See also the C<SEE ALSO> section at the end of this document - the Coro	65	See also the C<SEE ALSO> section at the end of this document - the Coro
62	module family is quite large.	66	module family is quite large.
63		67
		68	=head1 CORO THREAD LIFE CYCLE
		69
		70	During the long and exciting (or not) life of a coro thread, it goes
		71	through a number of states:
		72
		73	=over 4
		74
		75	=item 1. Creation
		76
		77	The first thing in the life of a coro thread is it's creation -
		78	obviously. The typical way to create a thread is to call the C<async
		79	BLOCK> function:
		80
		81	async {
		82	# thread code goes here
		83	};
		84
		85	You can also pass arguments, which are put in C<@_>:
		86
		87	async {
		88	print $_[1]; # prints 2
		89	} 1, 2, 3;
		90
		91	This creates a new coro thread and puts it into the ready queue, meaning
		92	it will run as soon as the CPU is free for it.
		93
		94	C<async> will return a Coro object - you can store this for future
		95	reference or ignore it - a thread that is running, ready to run or waiting
		96	for some event is alive on it's own.
		97
		98	Another way to create a thread is to call the C<new> constructor with a
		99	code-reference:
		100
		101	new Coro sub {
		102	# thread code goes here
		103	}, @optional_arguments;
		104
		105	This is quite similar to calling C<async>, but the important difference is
		106	that the new thread is not put into the ready queue, so the thread will
		107	not run until somebody puts it there. C<async> is, therefore, identical to
		108	this sequence:
		109
		110	my $coro = new Coro sub {
		111	# thread code goes here
		112	};
		113	$coro->ready;
		114	return $coro;
		115
		116	=item 2. Startup
		117
		118	When a new coro thread is created, only a copy of the code reference
		119	and the arguments are stored, no extra memory for stacks and so on is
		120	allocated, keeping the coro thread in a low-memory state.
		121
		122	Only when it actually starts executing will all the resources be finally
		123	allocated.
		124
		125	The optional arguments specified at coro creation are available in C<@_>,
		126	similar to function calls.
		127
		128	=item 3. Running / Blocking
		129
		130	A lot can happen after the coro thread has started running. Quite usually,
		131	it will not run to the end in one go (because you could use a function
		132	instead), but it will give up the CPU regularly because it waits for
		133	external events.
		134
		135	As long as a coro thread runs, its Coro object is available in the global
		136	variable C<$Coro::current>.
		137
		138	The low-level way to give up the CPU is to call the scheduler, which
		139	selects a new coro thread to run:
		140
		141	Coro::schedule;
		142
		143	Since running threads are not in the ready queue, calling the scheduler
		144	without doing anything else will block the coro thread forever - you need
		145	to arrange either for the coro to put woken up (readied) by some other
		146	event or some other thread, or you can put it into the ready queue before
		147	scheduling:
		148
		149	# this is exactly what Coro::cede does
		150	$Coro::current->ready;
		151	Coro::schedule;
		152
		153	All the higher-level synchronisation methods (Coro::Semaphore,
		154	Coro::rouse_*...) are actually implemented via C<< ->ready >> and C<<
		155	Coro::schedule >>.
		156
		157	While the coro thread is running it also might get assigned a C-level
		158	thread, or the C-level thread might be unassigned from it, as the Coro
		159	runtime wishes. A C-level thread needs to be assigned when your perl
		160	thread calls into some C-level function and that function in turn calls
		161	perl and perl then wants to switch coroutines. This happens most often
		162	when you run an event loop and block in the callback, or when perl
		163	itself calls some function such as C<AUTOLOAD> or methods via the C<tie>
		164	mechanism.
		165
		166	=item 4. Termination
		167
		168	Many threads actually terminate after some time. There are a number of
		169	ways to terminate a coro thread, the simplest is returning from the
		170	top-level code reference:
		171
		172	async {
		173	# after returning from here, the coro thread is terminated
		174	};
		175
		176	async {
		177	return if 0.5 < rand; # terminate a little earlier, maybe
		178	print "got a chance to print this\n";
		179	# or here
		180	};
		181
		182	Any values returned from the coroutine can be recovered using C<< ->join
		183	>>:
		184
		185	my $coro = async {
		186	"hello, world\n" # return a string
		187	};
		188
		189	my $hello_world = $coro->join;
		190
		191	print $hello_world;
		192
		193	Another way to terminate is to call C<< Coro::terminate >>, which at any
		194	subroutine call nesting level:
		195
		196	async {
		197	Coro::terminate "return value 1", "return value 2";
		198	};
		199
		200	Yet another way is to C<< ->cancel >> (or C<< ->safe_cancel >>) the coro
		201	thread from another thread:
		202
		203	my $coro = async {
		204	exit 1;
		205	};
		206
		207	$coro->cancel; # also accepts values for ->join to retrieve
		208
		209	Cancellation I<can> be dangerous - it's a bit like calling C<exit> without
		210	actually exiting, and might leave C libraries and XS modules in a weird
		211	state. Unlike other thread implementations, however, Coro is exceptionally
		212	safe with regards to cancellation, as perl will always be in a consistent
		213	state, and for those cases where you want to do truly marvellous things
		214	with your coro while it is being cancelled - that is, make sure all
		215	cleanup code is executed from the thread being cancelled - there is even a
		216	C<< ->safe_cancel >> method.
		217
		218	So, cancelling a thread that runs in an XS event loop might not be the
		219	best idea, but any other combination that deals with perl only (cancelling
		220	when a thread is in a C<tie> method or an C<AUTOLOAD> for example) is
		221	safe.
		222
		223	Last not least, a coro thread object that isn't referenced is C<<
		224	->cancel >>'ed automatically - just like other objects in Perl. This
		225	is not such a common case, however - a running thread is referencedy by
		226	C<$Coro::current>, a thread ready to run is referenced by the ready queue,
		227	a thread waiting on a lock or semaphore is referenced by being in some
		228	wait list and so on. But a thread that isn't in any of those queues gets
		229	cancelled:
		230
		231	async {
		232	schedule; # cede to other coros, don't go into the ready queue
		233	};
		234
		235	cede;
		236	# now the async above is destroyed, as it is not referenced by anything.
		237
		238	A slightly embellished example might make it clearer:
		239
		240	async {
		241	my $guard = Guard::guard { print "destroyed\n" };
		242	schedule while 1;
		243	};
		244
		245	cede;
		246
		247	Superficially one might not expect any output - since the C<async>
		248	implements an endless loop, the C<$guard> will not be cleaned up. However,
		249	since the thread object returned by C<async> is not stored anywhere, the
		250	thread is initially referenced because it is in the ready queue, when it
		251	runs it is referenced by C<$Coro::current>, but when it calls C<schedule>,
		252	it gets C<cancel>ed causing the guard object to be destroyed (see the next
		253	section), and printing it's message.
		254
		255	If this seems a bit drastic, remember that this only happens when nothing
		256	references the thread anymore, which means there is no way to further
		257	execute it, ever. The only options at this point are leaking the thread,
		258	or cleaning it up, which brings us to...
		259
		260	=item 5. Cleanup
		261
		262	Threads will allocate various resources. Most but not all will be returned
		263	when a thread terminates, during clean-up.
		264
		265	Cleanup is quite similar to throwing an uncaught exception: perl will
		266	work it's way up through all subroutine calls and blocks. On it's way, it
		267	will release all C<my> variables, undo all C<local>'s and free any other
		268	resources truly local to the thread.
		269
		270	So, a common way to free resources is to keep them referenced only by my
		271	variables:
		272
		273	async {
		274	my $big_cache = new Cache ...;
		275	};
		276
		277	If there are no other references, then the C<$big_cache> object will be
		278	freed when the thread terminates, regardless of how it does so.
		279
		280	What it does C<NOT> do is unlock any Coro::Semaphores or similar
		281	resources, but that's where the C<guard> methods come in handy:
		282
		283	my $sem = new Coro::Semaphore;
		284
		285	async {
		286	my $lock_guard = $sem->guard;
		287	# if we return, or die or get cancelled, here,
		288	# then the semaphore will be "up"ed.
		289	};
		290
		291	The C<Guard::guard> function comes in handy for any custom cleanup you
		292	might want to do (but you cannot switch to other coroutines from those
		293	code blocks):
		294
		295	async {
		296	my $window = new Gtk2::Window "toplevel";
		297	# The window will not be cleaned up automatically, even when $window
		298	# gets freed, so use a guard to ensure it's destruction
		299	# in case of an error:
		300	my $window_guard = Guard::guard { $window->destroy };
		301
		302	# we are safe here
		303	};
		304
		305	Last not least, C<local> can often be handy, too, e.g. when temporarily
		306	replacing the coro thread description:
		307
		308	sub myfunction {
		309	local $Coro::current->{desc} = "inside myfunction(@_)";
		310
		311	# if we return or die here, the description will be restored
		312	}
		313
		314	=item 6. Viva La Zombie Muerte
		315
		316	Even after a thread has terminated and cleaned up its resources, the Coro
		317	object still is there and stores the return values of the thread.
		318
		319	When there are no other references, it will simply be cleaned up and
		320	freed.
		321
		322	If there areany references, the Coro object will stay around, and you
		323	can call C<< ->join >> as many times as you wish to retrieve the result
		324	values:
		325
		326	async {
		327	print "hi\n";
		328	1
		329	};
		330
		331	# run the async above, and free everything before returning
		332	# from Coro::cede:
		333	Coro::cede;
		334
		335	{
		336	my $coro = async {
		337	print "hi\n";
		338	1
		339	};
		340
		341	# run the async above, and clean up, but do not free the coro
		342	# object:
		343	Coro::cede;
		344
		345	# optionally retrieve the result values
		346	my @results = $coro->join;
		347
		348	# now $coro goes out of scope, and presumably gets freed
		349	};
		350
		351	=back
		352
64	=cut	353	=cut
65		354
66	package Coro;	355	package Coro;
67		356
68	use strict qw(vars subs);	357	use common::sense;
69	no warnings "uninitialized";	358
		359	use Carp ();
		360
		361	use Guard ();
70		362
71	use Coro::State;	363	use Coro::State;
72		364
73	use base qw(Coro::State Exporter);	365	use base qw(Coro::State Exporter);
74		366
75	our $idle; # idle handler	367	our $idle; # idle handler
76	our $main; # main coroutine	368	our $main; # main coro
77	our $current; # current coroutine	369	our $current; # current coro
78		370
79	our $VERSION = 5.1;	371	our $VERSION = 6.48;
80		372
81	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	373	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
82	our %EXPORT_TAGS = (	374	our %EXPORT_TAGS = (
83	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	375	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
84	);	376	);
85	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	377	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
86		378
…		…
88		380
89	=over 4	381	=over 4
90		382
91	=item $Coro::main	383	=item $Coro::main
92		384
93	This variable stores the coroutine object that represents the main	385	This variable stores the Coro object that represents the main
94	program. While you cna C<ready> it and do most other things you can do to	386	program. While you can C<ready> it and do most other things you can do to
95	coroutines, it is mainly useful to compare again C<$Coro::current>, to see	387	coro, it is mainly useful to compare again C<$Coro::current>, to see
96	whether you are running in the main program or not.	388	whether you are running in the main program or not.
97		389
98	=cut	390	=cut
99		391
100	# $main is now being initialised by Coro::State	392	# $main is now being initialised by Coro::State
101		393
102	=item $Coro::current	394	=item $Coro::current
103		395
104	The coroutine object representing the current coroutine (the last	396	The Coro object representing the current coro (the last
105	coroutine that the Coro scheduler switched to). The initial value is	397	coro that the Coro scheduler switched to). The initial value is
106	C<$Coro::main> (of course).	398	C<$Coro::main> (of course).
107		399
108	This variable is B<strictly> I<read-only>. You can take copies of the	400	This variable is B<strictly> I<read-only>. You can take copies of the
109	value stored in it and use it as any other coroutine object, but you must	401	value stored in it and use it as any other Coro object, but you must
110	not otherwise modify the variable itself.	402	not otherwise modify the variable itself.
111		403
112	=cut	404	=cut
113		405
114	sub current() { $current } # [DEPRECATED]	406	sub current() { $current } # [DEPRECATED]
…		…
117		409
118	This variable is mainly useful to integrate Coro into event loops. It is	410	This variable is mainly useful to integrate Coro into event loops. It is
119	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is	411	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
120	pretty low-level functionality.	412	pretty low-level functionality.
121		413
122	This variable stores either a coroutine or a callback.	414	This variable stores a Coro object that is put into the ready queue when
		415	there are no other ready threads (without invoking any ready hooks).
123		416
124	If it is a callback, the it is called whenever the scheduler finds no	417	The default implementation dies with "FATAL: deadlock detected.", followed
125	ready coroutines to run. The default implementation prints "FATAL:	418	by a thread listing, because the program has no other way to continue.
126	deadlock detected" and exits, because the program has no other way to
127	continue.
128
129	If it is a coroutine object, then this object will be readied (without
130	invoking any ready hooks, however) when the scheduler finds no other ready
131	coroutines to run.
132		419
133	This hook is overwritten by modules such as C<Coro::EV> and	420	This hook is overwritten by modules such as C<Coro::EV> and
134	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a	421	C<Coro::AnyEvent> to wait on an external event that hopefully wakes up a
135	coroutine so the scheduler can run it.	422	coro so the scheduler can run it.
136		423
137	Note that the callback I<must not>, under any circumstances, block
138	the current coroutine. Normally, this is achieved by having an "idle
139	coroutine" that calls the event loop and then blocks again, and then
140	readying that coroutine in the idle handler, or by simply placing the idle
141	coroutine in this variable.
142
143	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this	424	See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
144	technique.
145
146	Please note that if your callback recursively invokes perl (e.g. for event
147	handlers), then it must be prepared to be called recursively itself.
148		425
149	=cut	426	=cut
150		427
151	$idle = sub {	428	# \|\|= because other modules could have provided their own by now
152	require Carp;	429	$idle \|\|= new Coro sub {
153	Carp::croak ("FATAL: deadlock detected");	430	require Coro::Debug;
		431	die "FATAL: deadlock detected.\n"
		432	. Coro::Debug::ps_listing ();
154	};	433	};
155		434
156	# this coroutine is necessary because a coroutine	435	# this coro is necessary because a coro
157	# cannot destroy itself.	436	# cannot destroy itself.
158	our @destroy;	437	our @destroy;
159	our $manager;	438	our $manager;
160		439
161	$manager = new Coro sub {	440	$manager = new Coro sub {
162	while () {	441	while () {
163	Coro::_cancel shift @destroy	442	_destroy shift @destroy
164	while @destroy;	443	while @destroy;
165		444
166	&schedule;	445	&schedule;
167	}	446	}
168	};	447	};
169	$manager->{desc} = "[coro manager]";	448	$manager->{desc} = "[coro manager]";
170	$manager->prio (PRIO_MAX);	449	$manager->prio (PRIO_MAX);
171		450
172	=back	451	=back
173		452
174	=head1 SIMPLE COROUTINE CREATION	453	=head1 SIMPLE CORO CREATION
175		454
176	=over 4	455	=over 4
177		456
178	=item async { ... } [@args...]	457	=item async { ... } [@args...]
179		458
180	Create a new coroutine and return it's coroutine object (usually	459	Create a new coro and return its Coro object (usually
181	unused). The coroutine will be put into the ready queue, so	460	unused). The coro will be put into the ready queue, so
182	it will start running automatically on the next scheduler run.	461	it will start running automatically on the next scheduler run.
183		462
184	The first argument is a codeblock/closure that should be executed in the	463	The first argument is a codeblock/closure that should be executed in the
185	coroutine. When it returns argument returns the coroutine is automatically	464	coro. When it returns argument returns the coro is automatically
186	terminated.	465	terminated.
187		466
188	The remaining arguments are passed as arguments to the closure.	467	The remaining arguments are passed as arguments to the closure.
189		468
190	See the C<Coro::State::new> constructor for info about the coroutine	469	See the C<Coro::State::new> constructor for info about the coro
191	environment in which coroutines are executed.	470	environment in which coro are executed.
192		471
193	Calling C<exit> in a coroutine will do the same as calling exit outside	472	Calling C<exit> in a coro will do the same as calling exit outside
194	the coroutine. Likewise, when the coroutine dies, the program will exit,	473	the coro. Likewise, when the coro dies, the program will exit,
195	just as it would in the main program.	474	just as it would in the main program.
196		475
197	If you do not want that, you can provide a default C<die> handler, or	476	If you do not want that, you can provide a default C<die> handler, or
198	simply avoid dieing (by use of C<eval>).	477	simply avoid dieing (by use of C<eval>).
199		478
200	Example: Create a new coroutine that just prints its arguments.	479	Example: Create a new coro that just prints its arguments.
201		480
202	async {	481	async {
203	print "@_\n";	482	print "@_\n";
204	} 1,2,3,4;	483	} 1,2,3,4;
205		484
206	=cut
207
208	sub async(&@) {
209	my $coro = new Coro @_;
210	$coro->ready;
211	$coro
212	}
213
214	=item async_pool { ... } [@args...]	485	=item async_pool { ... } [@args...]
215		486
216	Similar to C<async>, but uses a coroutine pool, so you should not call	487	Similar to C<async>, but uses a coro pool, so you should not call
217	terminate or join on it (although you are allowed to), and you get a	488	terminate or join on it (although you are allowed to), and you get a
218	coroutine that might have executed other code already (which can be good	489	coro that might have executed other code already (which can be good
219	or bad :).	490	or bad :).
220		491
221	On the plus side, this function is about twice as fast as creating (and	492	On the plus side, this function is about twice as fast as creating (and
222	destroying) a completely new coroutine, so if you need a lot of generic	493	destroying) a completely new coro, so if you need a lot of generic
223	coroutines in quick successsion, use C<async_pool>, not C<async>.	494	coros in quick successsion, use C<async_pool>, not C<async>.
224		495
225	The code block is executed in an C<eval> context and a warning will be	496	The code block is executed in an C<eval> context and a warning will be
226	issued in case of an exception instead of terminating the program, as	497	issued in case of an exception instead of terminating the program, as
227	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>	498	C<async> does. As the coro is being reused, stuff like C<on_destroy>
228	will not work in the expected way, unless you call terminate or cancel,	499	will not work in the expected way, unless you call terminate or cancel,
229	which somehow defeats the purpose of pooling (but is fine in the	500	which somehow defeats the purpose of pooling (but is fine in the
230	exceptional case).	501	exceptional case).
231		502
232	The priority will be reset to C<0> after each run, tracing will be	503	The priority will be reset to C<0> after each run, tracing will be
233	disabled, the description will be reset and the default output filehandle	504	disabled, the description will be reset and the default output filehandle
234	gets restored, so you can change all these. Otherwise the coroutine will	505	gets restored, so you can change all these. Otherwise the coro will
235	be re-used "as-is": most notably if you change other per-coroutine global	506	be re-used "as-is": most notably if you change other per-coro global
236	stuff such as C<$/> you I<must needs> revert that change, which is most	507	stuff such as C<$/> you I<must needs> revert that change, which is most
237	simply done by using local as in: C<< local $/ >>.	508	simply done by using local as in: C<< local $/ >>.
238		509
239	The idle pool size is limited to C<8> idle coroutines (this can be	510	The idle pool size is limited to C<8> idle coros (this can be
240	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle	511	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
241	coros as required.	512	coros as required.
242		513
243	If you are concerned about pooled coroutines growing a lot because a	514	If you are concerned about pooled coros growing a lot because a
244	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool	515	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
245	{ terminate }> once per second or so to slowly replenish the pool. In	516	{ terminate }> once per second or so to slowly replenish the pool. In
246	addition to that, when the stacks used by a handler grows larger than 32kb	517	addition to that, when the stacks used by a handler grows larger than 32kb
247	(adjustable via $Coro::POOL_RSS) it will also be destroyed.	518	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
248		519
…		…
265	=back	536	=back
266		537
267	=head1 STATIC METHODS	538	=head1 STATIC METHODS
268		539
269	Static methods are actually functions that implicitly operate on the	540	Static methods are actually functions that implicitly operate on the
270	current coroutine.	541	current coro.
271		542
272	=over 4	543	=over 4
273		544
274	=item schedule	545	=item schedule
275		546
276	Calls the scheduler. The scheduler will find the next coroutine that is	547	Calls the scheduler. The scheduler will find the next coro that is
277	to be run from the ready queue and switches to it. The next coroutine	548	to be run from the ready queue and switches to it. The next coro
278	to be run is simply the one with the highest priority that is longest	549	to be run is simply the one with the highest priority that is longest
279	in its ready queue. If there is no coroutine ready, it will clal the	550	in its ready queue. If there is no coro ready, it will call the
280	C<$Coro::idle> hook.	551	C<$Coro::idle> hook.
281		552
282	Please note that the current coroutine will I<not> be put into the ready	553	Please note that the current coro will I<not> be put into the ready
283	queue, so calling this function usually means you will never be called	554	queue, so calling this function usually means you will never be called
284	again unless something else (e.g. an event handler) calls C<< ->ready >>,	555	again unless something else (e.g. an event handler) calls C<< ->ready >>,
285	thus waking you up.	556	thus waking you up.
286		557
287	This makes C<schedule> I<the> generic method to use to block the current	558	This makes C<schedule> I<the> generic method to use to block the current
288	coroutine and wait for events: first you remember the current coroutine in	559	coro and wait for events: first you remember the current coro in
289	a variable, then arrange for some callback of yours to call C<< ->ready	560	a variable, then arrange for some callback of yours to call C<< ->ready
290	>> on that once some event happens, and last you call C<schedule> to put	561	>> on that once some event happens, and last you call C<schedule> to put
291	yourself to sleep. Note that a lot of things can wake your coroutine up,	562	yourself to sleep. Note that a lot of things can wake your coro up,
292	so you need to check whether the event indeed happened, e.g. by storing the	563	so you need to check whether the event indeed happened, e.g. by storing the
293	status in a variable.	564	status in a variable.
294		565
295	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.	566	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
296		567
297	=item cede	568	=item cede
298		569
299	"Cede" to other coroutines. This function puts the current coroutine into	570	"Cede" to other coros. This function puts the current coro into
300	the ready queue and calls C<schedule>, which has the effect of giving	571	the ready queue and calls C<schedule>, which has the effect of giving
301	up the current "timeslice" to other coroutines of the same or higher	572	up the current "timeslice" to other coros of the same or higher
302	priority. Once your coroutine gets its turn again it will automatically be	573	priority. Once your coro gets its turn again it will automatically be
303	resumed.	574	resumed.
304		575
305	This function is often called C<yield> in other languages.	576	This function is often called C<yield> in other languages.
306		577
307	=item Coro::cede_notself	578	=item Coro::cede_notself
308		579
309	Works like cede, but is not exported by default and will cede to I<any>	580	Works like cede, but is not exported by default and will cede to I<any>
310	coroutine, regardless of priority. This is useful sometimes to ensure	581	coro, regardless of priority. This is useful sometimes to ensure
311	progress is made.	582	progress is made.
312		583
313	=item terminate [arg...]	584	=item terminate [arg...]
314		585
315	Terminates the current coroutine with the given status values (see L<cancel>).	586	Terminates the current coro with the given status values (see
		587	L<cancel>). The values will not be copied, but referenced directly.
		588
		589	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
		590
		591	These function install enter and leave winders in the current scope. The
		592	enter block will be executed when on_enter is called and whenever the
		593	current coro is re-entered by the scheduler, while the leave block is
		594	executed whenever the current coro is blocked by the scheduler, and
		595	also when the containing scope is exited (by whatever means, be it exit,
		596	die, last etc.).
		597
		598	I<Neither invoking the scheduler, nor exceptions, are allowed within those
		599	BLOCKs>. That means: do not even think about calling C<die> without an
		600	eval, and do not even think of entering the scheduler in any way.
		601
		602	Since both BLOCKs are tied to the current scope, they will automatically
		603	be removed when the current scope exits.
		604
		605	These functions implement the same concept as C<dynamic-wind> in scheme
		606	does, and are useful when you want to localise some resource to a specific
		607	coro.
		608
		609	They slow down thread switching considerably for coros that use them
		610	(about 40% for a BLOCK with a single assignment, so thread switching is
		611	still reasonably fast if the handlers are fast).
		612
		613	These functions are best understood by an example: The following function
		614	will change the current timezone to "Antarctica/South_Pole", which
		615	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
		616	which remember/change the current timezone and restore the previous
		617	value, respectively, the timezone is only changed for the coro that
		618	installed those handlers.
		619
		620	use POSIX qw(tzset);
		621
		622	async {
		623	my $old_tz; # store outside TZ value here
		624
		625	Coro::on_enter {
		626	$old_tz = $ENV{TZ}; # remember the old value
		627
		628	$ENV{TZ} = "Antarctica/South_Pole";
		629	tzset; # enable new value
		630	};
		631
		632	Coro::on_leave {
		633	$ENV{TZ} = $old_tz;
		634	tzset; # restore old value
		635	};
		636
		637	# at this place, the timezone is Antarctica/South_Pole,
		638	# without disturbing the TZ of any other coro.
		639	};
		640
		641	This can be used to localise about any resource (locale, uid, current
		642	working directory etc.) to a block, despite the existance of other
		643	coros.
		644
		645	Another interesting example implements time-sliced multitasking using
		646	interval timers (this could obviously be optimised, but does the job):
		647
		648	# "timeslice" the given block
		649	sub timeslice(&) {
		650	use Time::HiRes ();
		651
		652	Coro::on_enter {
		653	# on entering the thread, we set an VTALRM handler to cede
		654	$SIG{VTALRM} = sub { cede };
		655	# and then start the interval timer
		656	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
		657	};
		658	Coro::on_leave {
		659	# on leaving the thread, we stop the interval timer again
		660	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
		661	};
		662
		663	&{+shift};
		664	}
		665
		666	# use like this:
		667	timeslice {
		668	# The following is an endless loop that would normally
		669	# monopolise the process. Since it runs in a timesliced
		670	# environment, it will regularly cede to other threads.
		671	while () { }
		672	};
		673
316		674
317	=item killall	675	=item killall
318		676
319	Kills/terminates/cancels all coroutines except the currently running	677	Kills/terminates/cancels all coros except the currently running one.
320	one. This is useful after a fork, either in the child or the parent, as
321	usually only one of them should inherit the running coroutines.
322		678
323	Note that while this will try to free some of the main programs resources,	679	Note that while this will try to free some of the main interpreter
		680	resources if the calling coro isn't the main coro, but one
324	you cannot free all of them, so if a coroutine that is not the main	681	cannot free all of them, so if a coro that is not the main coro
325	program calls this function, there will be some one-time resource leak.	682	calls this function, there will be some one-time resource leak.
326		683
327	=cut	684	=cut
328		685
329	sub killall {	686	sub killall {
330	for (Coro::State::list) {	687	for (Coro::State::list) {
…		…
333	}	690	}
334	}	691	}
335		692
336	=back	693	=back
337		694
338	=head1 COROUTINE OBJECT METHODS	695	=head1 CORO OBJECT METHODS
339		696
340	These are the methods you can call on coroutine objects (or to create	697	These are the methods you can call on coro objects (or to create
341	them).	698	them).
342		699
343	=over 4	700	=over 4
344		701
345	=item new Coro \&sub [, @args...]	702	=item new Coro \&sub [, @args...]
346		703
347	Create a new coroutine and return it. When the sub returns, the coroutine	704	Create a new coro and return it. When the sub returns, the coro
348	automatically terminates as if C<terminate> with the returned values were	705	automatically terminates as if C<terminate> with the returned values were
349	called. To make the coroutine run you must first put it into the ready	706	called. To make the coro run you must first put it into the ready
350	queue by calling the ready method.	707	queue by calling the ready method.
351		708
352	See C<async> and C<Coro::State::new> for additional info about the	709	See C<async> and C<Coro::State::new> for additional info about the
353	coroutine environment.	710	coro environment.
354		711
355	=cut	712	=cut
356		713
357	sub _terminate {	714	sub _coro_run {
358	terminate &{+shift};	715	terminate &{+shift};
359	}	716	}
360		717
361	=item $success = $coroutine->ready	718	=item $success = $coro->ready
362		719
363	Put the given coroutine into the end of its ready queue (there is one	720	Put the given coro into the end of its ready queue (there is one
364	queue for each priority) and return true. If the coroutine is already in	721	queue for each priority) and return true. If the coro is already in
365	the ready queue, do nothing and return false.	722	the ready queue, do nothing and return false.
366		723
367	This ensures that the scheduler will resume this coroutine automatically	724	This ensures that the scheduler will resume this coro automatically
368	once all the coroutines of higher priority and all coroutines of the same	725	once all the coro of higher priority and all coro of the same
369	priority that were put into the ready queue earlier have been resumed.	726	priority that were put into the ready queue earlier have been resumed.
370		727
		728	=item $coro->suspend
		729
		730	Suspends the specified coro. A suspended coro works just like any other
		731	coro, except that the scheduler will not select a suspended coro for
		732	execution.
		733
		734	Suspending a coro can be useful when you want to keep the coro from
		735	running, but you don't want to destroy it, or when you want to temporarily
		736	freeze a coro (e.g. for debugging) to resume it later.
		737
		738	A scenario for the former would be to suspend all (other) coros after a
		739	fork and keep them alive, so their destructors aren't called, but new
		740	coros can be created.
		741
		742	=item $coro->resume
		743
		744	If the specified coro was suspended, it will be resumed. Note that when
		745	the coro was in the ready queue when it was suspended, it might have been
		746	unreadied by the scheduler, so an activation might have been lost.
		747
		748	To avoid this, it is best to put a suspended coro into the ready queue
		749	unconditionally, as every synchronisation mechanism must protect itself
		750	against spurious wakeups, and the one in the Coro family certainly do
		751	that.
		752
		753	=item $state->is_new
		754
		755	Returns true iff this Coro object is "new", i.e. has never been run
		756	yet. Those states basically consist of only the code reference to call and
		757	the arguments, but consumes very little other resources. New states will
		758	automatically get assigned a perl interpreter when they are transfered to.
		759
		760	=item $state->is_zombie
		761
		762	Returns true iff the Coro object has been cancelled, i.e.
		763	it's resources freed because they were C<cancel>'ed, C<terminate>'d,
		764	C<safe_cancel>'ed or simply went out of scope.
		765
		766	The name "zombie" stems from UNIX culture, where a process that has
		767	exited and only stores and exit status and no other resources is called a
		768	"zombie".
		769
371	=item $is_ready = $coroutine->is_ready	770	=item $is_ready = $coro->is_ready
372		771
373	Return whether the coroutine is currently the ready queue or not,	772	Returns true iff the Coro object is in the ready queue. Unless the Coro
		773	object gets destroyed, it will eventually be scheduled by the scheduler.
374		774
		775	=item $is_running = $coro->is_running
		776
		777	Returns true iff the Coro object is currently running. Only one Coro object
		778	can ever be in the running state (but it currently is possible to have
		779	multiple running Coro::States).
		780
		781	=item $is_suspended = $coro->is_suspended
		782
		783	Returns true iff this Coro object has been suspended. Suspended Coros will
		784	not ever be scheduled.
		785
375	=item $coroutine->cancel (arg...)	786	=item $coro->cancel (arg...)
376		787
377	Terminates the given coroutine and makes it return the given arguments as	788	Terminates the given Coro thread and makes it return the given arguments as
378	status (default: the empty list). Never returns if the coroutine is the	789	status (default: an empty list). Never returns if the Coro is the
379	current coroutine.	790	current Coro.
380		791
381	=cut	792	This is a rather brutal way to free a coro, with some limitations - if
		793	the thread is inside a C callback that doesn't expect to be canceled,
		794	bad things can happen, or if the cancelled thread insists on running
		795	complicated cleanup handlers that rely on its thread context, things will
		796	not work.
382		797
383	sub cancel {	798	Any cleanup code being run (e.g. from C<guard> blocks, destructors and so
384	my $self = shift;	799	on) will be run without a thread context, and is not allowed to switch
		800	to other threads. A common mistake is to call C<< ->cancel >> from a
		801	destructor called by die'ing inside the thread to be cancelled for
		802	example.
385		803
386	if ($current == $self) {	804	On the plus side, C<< ->cancel >> will always clean up the thread, no
387	terminate @_;	805	matter what. If your cleanup code is complex or you want to avoid
388	} else {	806	cancelling a C-thread that doesn't know how to clean up itself, it can be
389	$self->{_status} = [@_];	807	better to C<< ->throw >> an exception, or use C<< ->safe_cancel >>.
390	$self->_cancel;	808
		809	The arguments to C<< ->cancel >> are not copied, but instead will
		810	be referenced directly (e.g. if you pass C<$var> and after the call
		811	change that variable, then you might change the return values passed to
		812	e.g. C<join>, so don't do that).
		813
		814	The resources of the Coro are usually freed (or destructed) before this
		815	call returns, but this can be delayed for an indefinite amount of time, as
		816	in some cases the manager thread has to run first to actually destruct the
		817	Coro object.
		818
		819	=item $coro->safe_cancel ($arg...)
		820
		821	Works mostly like C<< ->cancel >>, but is inherently "safer", and
		822	consequently, can fail with an exception in cases the thread is not in a
		823	cancellable state. Essentially, C<< ->safe_cancel >> is a C<< ->cancel >>
		824	with extra checks before canceling.
		825
		826	It works a bit like throwing an exception that cannot be caught -
		827	specifically, it will clean up the thread from within itself, so all
		828	cleanup handlers (e.g. C<guard> blocks) are run with full thread
		829	context and can block if they wish. The downside is that there is no
		830	guarantee that the thread can be cancelled when you call this method, and
		831	therefore, it might fail. It is also considerably slower than C<cancel> or
		832	C<terminate>.
		833
		834	A thread is in a safe-cancellable state if it either hasn't been run yet,
		835	or it has no C context attached and is inside an SLF function.
		836
		837	The latter two basically mean that the thread isn't currently inside a
		838	perl callback called from some C function (usually via some XS modules)
		839	and isn't currently executing inside some C function itself (via Coro's XS
		840	API).
		841
		842	This call returns true when it could cancel the thread, or croaks with an
		843	error otherwise (i.e. it either returns true or doesn't return at all).
		844
		845	Why the weird interface? Well, there are two common models on how and
		846	when to cancel things. In the first, you have the expectation that your
		847	coro thread can be cancelled when you want to cancel it - if the thread
		848	isn't cancellable, this would be a bug somewhere, so C<< ->safe_cancel >>
		849	croaks to notify of the bug.
		850
		851	In the second model you sometimes want to ask nicely to cancel a thread,
		852	but if it's not a good time, well, then don't cancel. This can be done
		853	relatively easy like this:
		854
		855	if (! eval { $coro->safe_cancel }) {
		856	warn "unable to cancel thread: $@";
391	}	857	}
392	}
393		858
		859	However, what you never should do is first try to cancel "safely" and
		860	if that fails, cancel the "hard" way with C<< ->cancel >>. That makes
		861	no sense: either you rely on being able to execute cleanup code in your
		862	thread context, or you don't. If you do, then C<< ->safe_cancel >> is the
		863	only way, and if you don't, then C<< ->cancel >> is always faster and more
		864	direct.
		865
394	=item $coroutine->schedule_to	866	=item $coro->schedule_to
395		867
396	Puts the current coroutine to sleep (like C<Coro::schedule>), but instead	868	Puts the current coro to sleep (like C<Coro::schedule>), but instead
397	of continuing with the next coro from the ready queue, always switch to	869	of continuing with the next coro from the ready queue, always switch to
398	the given coroutine object (regardless of priority etc.). The readyness	870	the given coro object (regardless of priority etc.). The readyness
399	state of that coroutine isn't changed.	871	state of that coro isn't changed.
400		872
401	This is an advanced method for special cases - I'd love to hear about any	873	This is an advanced method for special cases - I'd love to hear about any
402	uses for this one.	874	uses for this one.
403		875
404	=item $coroutine->cede_to	876	=item $coro->cede_to
405		877
406	Like C<schedule_to>, but puts the current coroutine into the ready	878	Like C<schedule_to>, but puts the current coro into the ready
407	queue. This has the effect of temporarily switching to the given	879	queue. This has the effect of temporarily switching to the given
408	coroutine, and continuing some time later.	880	coro, and continuing some time later.
409		881
410	This is an advanced method for special cases - I'd love to hear about any	882	This is an advanced method for special cases - I'd love to hear about any
411	uses for this one.	883	uses for this one.
412		884
413	=item $coroutine->throw ([$scalar])	885	=item $coro->throw ([$scalar])
414		886
415	If C<$throw> is specified and defined, it will be thrown as an exception	887	If C<$throw> is specified and defined, it will be thrown as an exception
416	inside the coroutine at the next convenient point in time. Otherwise	888	inside the coro at the next convenient point in time. Otherwise
417	clears the exception object.	889	clears the exception object.
418		890
419	Coro will check for the exception each time a schedule-like-function	891	Coro will check for the exception each time a schedule-like-function
420	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down	892	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
421	>>, C<< Coro::Handle->readable >> and so on. Most of these functions	893	>>, C<< Coro::Handle->readable >> and so on. Most of those functions (all
422	detect this case and return early in case an exception is pending.	894	that are part of Coro itself) detect this case and return early in case an
		895	exception is pending.
423		896
424	The exception object will be thrown "as is" with the specified scalar in	897	The exception object will be thrown "as is" with the specified scalar in
425	C<$@>, i.e. if it is a string, no line number or newline will be appended	898	C<$@>, i.e. if it is a string, no line number or newline will be appended
426	(unlike with C<die>).	899	(unlike with C<die>).
427		900
428	This can be used as a softer means than C<cancel> to ask a coroutine to	901	This can be used as a softer means than either C<cancel> or C<safe_cancel
429	end itself, although there is no guarantee that the exception will lead to	902	>to ask a coro to end itself, although there is no guarantee that the
430	termination, and if the exception isn't caught it might well end the whole	903	exception will lead to termination, and if the exception isn't caught it
431	program.	904	might well end the whole program.
432		905
433	You might also think of C<throw> as being the moral equivalent of	906	You might also think of C<throw> as being the moral equivalent of
434	C<kill>ing a coroutine with a signal (in this case, a scalar).	907	C<kill>ing a coro with a signal (in this case, a scalar).
435		908
436	=item $coroutine->join	909	=item $coro->join
437		910
438	Wait until the coroutine terminates and return any values given to the	911	Wait until the coro terminates and return any values given to the
439	C<terminate> or C<cancel> functions. C<join> can be called concurrently	912	C<terminate> or C<cancel> functions. C<join> can be called concurrently
440	from multiple coroutines, and all will be resumed and given the status	913	from multiple threads, and all will be resumed and given the status
441	return once the C<$coroutine> terminates.	914	return once the C<$coro> terminates.
442		915
443	=cut
444
445	sub join {
446	my $self = shift;
447
448	unless ($self->{_status}) {
449	my $current = $current;
450
451	push @{$self->{_on_destroy}}, sub {
452	$current->ready;
453	undef $current;
454	};
455
456	&schedule while $current;
457	}
458
459	wantarray ? @{$self->{_status}} : $self->{_status}[0];
460	}
461
462	=item $coroutine->on_destroy (\&cb)	916	=item $coro->on_destroy (\&cb)
463		917
464	Registers a callback that is called when this coroutine gets destroyed,	918	Registers a callback that is called when this coro thread gets destroyed,
465	but before it is joined. The callback gets passed the terminate arguments,	919	that is, after it's resources have been freed but before it is joined. The
		920	callback gets passed the terminate/cancel arguments, if any, and I<must
466	if any, and I<must not> die, under any circumstances.	921	not> die, under any circumstances.
467		922
468	=cut	923	There can be any number of C<on_destroy> callbacks per coro, and there is
		924	currently no way to remove a callback once added.
469		925
470	sub on_destroy {
471	my ($self, $cb) = @_;
472
473	push @{ $self->{_on_destroy} }, $cb;
474	}
475
476	=item $oldprio = $coroutine->prio ($newprio)	926	=item $oldprio = $coro->prio ($newprio)
477		927
478	Sets (or gets, if the argument is missing) the priority of the	928	Sets (or gets, if the argument is missing) the priority of the
479	coroutine. Higher priority coroutines get run before lower priority	929	coro thread. Higher priority coro get run before lower priority
480	coroutines. Priorities are small signed integers (currently -4 .. +3),	930	coros. Priorities are small signed integers (currently -4 .. +3),
481	that you can refer to using PRIO_xxx constants (use the import tag :prio	931	that you can refer to using PRIO_xxx constants (use the import tag :prio
482	to get then):	932	to get then):
483		933
484	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	934	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
485	3 > 1 > 0 > -1 > -3 > -4	935	3 > 1 > 0 > -1 > -3 > -4
486		936
487	# set priority to HIGH	937	# set priority to HIGH
488	current->prio(PRIO_HIGH);	938	current->prio (PRIO_HIGH);
489		939
490	The idle coroutine ($Coro::idle) always has a lower priority than any	940	The idle coro thread ($Coro::idle) always has a lower priority than any
491	existing coroutine.	941	existing coro.
492		942
493	Changing the priority of the current coroutine will take effect immediately,	943	Changing the priority of the current coro will take effect immediately,
494	but changing the priority of coroutines in the ready queue (but not	944	but changing the priority of a coro in the ready queue (but not running)
495	running) will only take effect after the next schedule (of that	945	will only take effect after the next schedule (of that coro). This is a
496	coroutine). This is a bug that will be fixed in some future version.	946	bug that will be fixed in some future version.
497		947
498	=item $newprio = $coroutine->nice ($change)	948	=item $newprio = $coro->nice ($change)
499		949
500	Similar to C<prio>, but subtract the given value from the priority (i.e.	950	Similar to C<prio>, but subtract the given value from the priority (i.e.
501	higher values mean lower priority, just as in unix).	951	higher values mean lower priority, just as in UNIX's nice command).
502		952
503	=item $olddesc = $coroutine->desc ($newdesc)	953	=item $olddesc = $coro->desc ($newdesc)
504		954
505	Sets (or gets in case the argument is missing) the description for this	955	Sets (or gets in case the argument is missing) the description for this
506	coroutine. This is just a free-form string you can associate with a	956	coro thread. This is just a free-form string you can associate with a
507	coroutine.	957	coro.
508		958
509	This method simply sets the C<< $coroutine->{desc} >> member to the given	959	This method simply sets the C<< $coro->{desc} >> member to the given
510	string. You can modify this member directly if you wish.	960	string. You can modify this member directly if you wish, and in fact, this
		961	is often preferred to indicate major processing states that can then be
		962	seen for example in a L<Coro::Debug> session:
		963
		964	sub my_long_function {
		965	local $Coro::current->{desc} = "now in my_long_function";
		966	...
		967	$Coro::current->{desc} = "my_long_function: phase 1";
		968	...
		969	$Coro::current->{desc} = "my_long_function: phase 2";
		970	...
		971	}
511		972
512	=cut	973	=cut
513		974
514	sub desc {	975	sub desc {
515	my $old = $_[0]{desc};	976	my $old = $_[0]{desc};
…		…
528		989
529	=over 4	990	=over 4
530		991
531	=item Coro::nready	992	=item Coro::nready
532		993
533	Returns the number of coroutines that are currently in the ready state,	994	Returns the number of coro that are currently in the ready state,
534	i.e. that can be switched to by calling C<schedule> directory or	995	i.e. that can be switched to by calling C<schedule> directory or
535	indirectly. The value C<0> means that the only runnable coroutine is the	996	indirectly. The value C<0> means that the only runnable coro is the
536	currently running one, so C<cede> would have no effect, and C<schedule>	997	currently running one, so C<cede> would have no effect, and C<schedule>
537	would cause a deadlock unless there is an idle handler that wakes up some	998	would cause a deadlock unless there is an idle handler that wakes up some
538	coroutines.	999	coro.
539		1000
540	=item my $guard = Coro::guard { ... }	1001	=item my $guard = Coro::guard { ... }
541		1002
542	This creates and returns a guard object. Nothing happens until the object	1003	This function still exists, but is deprecated. Please use the
543	gets destroyed, in which case the codeblock given as argument will be	1004	C<Guard::guard> function instead.
544	executed. This is useful to free locks or other resources in case of a
545	runtime error or when the coroutine gets canceled, as in both cases the
546	guard block will be executed. The guard object supports only one method,
547	C<< ->cancel >>, which will keep the codeblock from being executed.
548
549	Example: set some flag and clear it again when the coroutine gets canceled
550	or the function returns:
551
552	sub do_something {
553	my $guard = Coro::guard { $busy = 0 };
554	$busy = 1;
555
556	# do something that requires $busy to be true
557	}
558		1005
559	=cut	1006	=cut
560		1007
561	sub guard(&) {	1008	BEGIN { *guard = \&Guard::guard }
562	bless \(my $cb = $_[0]), "Coro::guard"
563	}
564
565	sub Coro::guard::cancel {
566	${$_[0]} = sub { };
567	}
568
569	sub Coro::guard::DESTROY {
570	${$_[0]}->();
571	}
572
573		1009
574	=item unblock_sub { ... }	1010	=item unblock_sub { ... }
575		1011
576	This utility function takes a BLOCK or code reference and "unblocks" it,	1012	This utility function takes a BLOCK or code reference and "unblocks" it,
577	returning a new coderef. Unblocking means that calling the new coderef	1013	returning a new coderef. Unblocking means that calling the new coderef
578	will return immediately without blocking, returning nothing, while the	1014	will return immediately without blocking, returning nothing, while the
579	original code ref will be called (with parameters) from within another	1015	original code ref will be called (with parameters) from within another
580	coroutine.	1016	coro.
581		1017
582	The reason this function exists is that many event libraries (such as the	1018	The reason this function exists is that many event libraries (such as
583	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form	1019	the venerable L<Event\|Event> module) are not thread-safe (a weaker form
584	of reentrancy). This means you must not block within event callbacks,	1020	of reentrancy). This means you must not block within event callbacks,
585	otherwise you might suffer from crashes or worse. The only event library	1021	otherwise you might suffer from crashes or worse. The only event library
586	currently known that is safe to use without C<unblock_sub> is L<EV>.	1022	currently known that is safe to use without C<unblock_sub> is L<EV> (but
		1023	you might still run into deadlocks if all event loops are blocked).
		1024
		1025	Coro will try to catch you when you block in the event loop
		1026	("FATAL: $Coro::idle blocked itself"), but this is just best effort and
		1027	only works when you do not run your own event loop.
587		1028
588	This function allows your callbacks to block by executing them in another	1029	This function allows your callbacks to block by executing them in another
589	coroutine where it is safe to block. One example where blocking is handy	1030	coro where it is safe to block. One example where blocking is handy
590	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	1031	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
591	disk, for example.	1032	disk, for example.
592		1033
593	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	1034	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
594	creating event callbacks that want to block.	1035	creating event callbacks that want to block.
595		1036
596	If your handler does not plan to block (e.g. simply sends a message to	1037	If your handler does not plan to block (e.g. simply sends a message to
597	another coroutine, or puts some other coroutine into the ready queue),	1038	another coro, or puts some other coro into the ready queue), there is
598	there is no reason to use C<unblock_sub>.	1039	no reason to use C<unblock_sub>.
599		1040
600	Note that you also need to use C<unblock_sub> for any other callbacks that	1041	Note that you also need to use C<unblock_sub> for any other callbacks that
601	are indirectly executed by any C-based event loop. For example, when you	1042	are indirectly executed by any C-based event loop. For example, when you
602	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it	1043	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
603	provides callbacks that are the result of some event callback, then you	1044	provides callbacks that are the result of some event callback, then you
…		…
633	unshift @unblock_queue, [$cb, @_];	1074	unshift @unblock_queue, [$cb, @_];
634	$unblock_scheduler->ready;	1075	$unblock_scheduler->ready;
635	}	1076	}
636	}	1077	}
637		1078
638	=item $cb = Coro::rouse_cb	1079	=item $cb = rouse_cb
639		1080
640	Create and return a "rouse callback". That's a code reference that,	1081	Create and return a "rouse callback". That's a code reference that,
641	when called, will remember a copy of its arguments and notify the owner	1082	when called, will remember a copy of its arguments and notify the owner
642	coroutine of the callback.	1083	coro of the callback.
643		1084
644	See the next function.	1085	See the next function.
645		1086
646	=item @args = Coro::rouse_wait [$cb]	1087	=item @args = rouse_wait [$cb]
647		1088
648	Wait for the specified rouse callback (or the last one that was created in	1089	Wait for the specified rouse callback (or the last one that was created in
649	this coroutine).	1090	this coro).
650		1091
651	As soon as the callback is invoked (or when the callback was invoked	1092	As soon as the callback is invoked (or when the callback was invoked
652	before C<rouse_wait>), it will return the arguments originally passed to	1093	before C<rouse_wait>), it will return the arguments originally passed to
653	the rouse callback.	1094	the rouse callback. In scalar context, that means you get the I<last>
		1095	argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
		1096	statement at the end.
654		1097
655	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.	1098	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
656		1099
657	=back	1100	=back
658		1101
659	=cut	1102	=cut
660		1103
		1104	for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) {
		1105	my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"};
		1106
		1107	*{"Coro::$module\::new"} = sub {
		1108	require "Coro/$module.pm";
		1109
		1110	# some modules have their new predefined in State.xs, some don't
		1111	*{"Coro::$module\::new"} = $old
		1112	if $old;
		1113
		1114	goto &{"Coro::$module\::new"};
		1115	};
		1116	}
		1117
661	1;	1118	1;
662		1119
663	=head1 HOW TO WAIT FOR A CALLBACK	1120	=head1 HOW TO WAIT FOR A CALLBACK
664		1121
665	It is very common for a coroutine to wait for some callback to be	1122	It is very common for a coro to wait for some callback to be
666	called. This occurs naturally when you use coroutines in an otherwise	1123	called. This occurs naturally when you use coro in an otherwise
667	event-based program, or when you use event-based libraries.	1124	event-based program, or when you use event-based libraries.
668		1125
669	These typically register a callback for some event, and call that callback	1126	These typically register a callback for some event, and call that callback
670	when the event occured. In a coroutine, however, you typically want to	1127	when the event occured. In a coro, however, you typically want to
671	just wait for the event, simplyifying things.	1128	just wait for the event, simplyifying things.
672		1129
673	For example C<< AnyEvent->child >> registers a callback to be called when	1130	For example C<< AnyEvent->child >> registers a callback to be called when
674	a specific child has exited:	1131	a specific child has exited:
675		1132
676	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });	1133	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
677		1134
678	But from withina coroutine, you often just want to write this:	1135	But from within a coro, you often just want to write this:
679		1136
680	my $status = wait_for_child $pid;	1137	my $status = wait_for_child $pid;
681		1138
682	Coro offers two functions specifically designed to make this easy,	1139	Coro offers two functions specifically designed to make this easy,
683	C<Coro::rouse_cb> and C<Coro::rouse_wait>.	1140	C<rouse_cb> and C<rouse_wait>.
684		1141
685	The first function, C<rouse_cb>, generates and returns a callback that,	1142	The first function, C<rouse_cb>, generates and returns a callback that,
686	when invoked, will save it's arguments and notify the coroutine that	1143	when invoked, will save its arguments and notify the coro that
687	created the callback.	1144	created the callback.
688		1145
689	The second function, C<rouse_wait>, waits for the callback to be called	1146	The second function, C<rouse_wait>, waits for the callback to be called
690	(by calling C<schedule> to go to sleep) and returns the arguments	1147	(by calling C<schedule> to go to sleep) and returns the arguments
691	originally passed to the callback.	1148	originally passed to the callback.
…		…
694	function mentioned above:	1151	function mentioned above:
695		1152
696	sub wait_for_child($) {	1153	sub wait_for_child($) {
697	my ($pid) = @_;	1154	my ($pid) = @_;
698		1155
699	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);	1156	my $watcher = AnyEvent->child (pid => $pid, cb => rouse_cb);
700		1157
701	my ($rpid, $rstatus) = Coro::rouse_wait;	1158	my ($rpid, $rstatus) = rouse_wait;
702	$rstatus	1159	$rstatus
703	}	1160	}
704		1161
705	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,	1162	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
706	you can roll your own, using C<schedule>:	1163	you can roll your own, using C<schedule> and C<ready>:
707		1164
708	sub wait_for_child($) {	1165	sub wait_for_child($) {
709	my ($pid) = @_;	1166	my ($pid) = @_;
710		1167
711	# store the current coroutine in $current,	1168	# store the current coro in $current,
712	# and provide result variables for the closure passed to ->child	1169	# and provide result variables for the closure passed to ->child
713	my $current = $Coro::current;	1170	my $current = $Coro::current;
714	my ($done, $rstatus);	1171	my ($done, $rstatus);
715		1172
716	# pass a closure to ->child	1173	# pass a closure to ->child
717	my $watcher = AnyEvent->child (pid => $pid, cb => sub {	1174	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
718	$rstatus = $_[1]; # remember rstatus	1175	$rstatus = $_[1]; # remember rstatus
719	$done = 1; # mark $rstatus as valud	1176	$done = 1; # mark $rstatus as valid
		1177	$current->ready; # wake up the waiting thread
720	});	1178	});
721		1179
722	# wait until the closure has been called	1180	# wait until the closure has been called
723	schedule while !$done;	1181	schedule while !$done;
724		1182
…		…
732		1190
733	=item fork with pthread backend	1191	=item fork with pthread backend
734		1192
735	When Coro is compiled using the pthread backend (which isn't recommended	1193	When Coro is compiled using the pthread backend (which isn't recommended
736	but required on many BSDs as their libcs are completely broken), then	1194	but required on many BSDs as their libcs are completely broken), then
737	coroutines will not survive a fork. There is no known workaround except to	1195	coro will not survive a fork. There is no known workaround except to
738	fix your libc and use a saner backend.	1196	fix your libc and use a saner backend.
739		1197
740	=item perl process emulation ("threads")	1198	=item perl process emulation ("threads")
741		1199
742	This module is not perl-pseudo-thread-safe. You should only ever use this	1200	This module is not perl-pseudo-thread-safe. You should only ever use this
…		…
744	future to allow per-thread schedulers, but Coro::State does not yet allow	1202	future to allow per-thread schedulers, but Coro::State does not yet allow
745	this). I recommend disabling thread support and using processes, as having	1203	this). I recommend disabling thread support and using processes, as having
746	the windows process emulation enabled under unix roughly halves perl	1204	the windows process emulation enabled under unix roughly halves perl
747	performance, even when not used.	1205	performance, even when not used.
748		1206
		1207	Attempts to use threads created in another emulated process will crash
		1208	("cleanly", with a null pointer exception).
		1209
749	=item coroutine switching not signal safe	1210	=item coro switching is not signal safe
750		1211
751	You must not switch to another coroutine from within a signal handler	1212	You must not switch to another coro from within a signal handler (only
752	(only relevant with %SIG - most event libraries provide safe signals).	1213	relevant with %SIG - most event libraries provide safe signals), I<unless>
		1214	you are sure you are not interrupting a Coro function.
753		1215
754	That means you I<MUST NOT> call any function that might "block" the	1216	That means you I<MUST NOT> call any function that might "block" the
755	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or	1217	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
756	anything that calls those. Everything else, including calling C<ready>,	1218	anything that calls those. Everything else, including calling C<ready>,
757	works.	1219	works.
758		1220
759	=back	1221	=back
760		1222
		1223
		1224	=head1 WINDOWS PROCESS EMULATION
		1225
		1226	A great many people seem to be confused about ithreads (for example, Chip
		1227	Salzenberg called me unintelligent, incapable, stupid and gullible,
		1228	while in the same mail making rather confused statements about perl
		1229	ithreads (for example, that memory or files would be shared), showing his
		1230	lack of understanding of this area - if it is hard to understand for Chip,
		1231	it is probably not obvious to everybody).
		1232
		1233	What follows is an ultra-condensed version of my talk about threads in
		1234	scripting languages given on the perl workshop 2009:
		1235
		1236	The so-called "ithreads" were originally implemented for two reasons:
		1237	first, to (badly) emulate unix processes on native win32 perls, and
		1238	secondly, to replace the older, real thread model ("5.005-threads").
		1239
		1240	It does that by using threads instead of OS processes. The difference
		1241	between processes and threads is that threads share memory (and other
		1242	state, such as files) between threads within a single process, while
		1243	processes do not share anything (at least not semantically). That
		1244	means that modifications done by one thread are seen by others, while
		1245	modifications by one process are not seen by other processes.
		1246
		1247	The "ithreads" work exactly like that: when creating a new ithreads
		1248	process, all state is copied (memory is copied physically, files and code
		1249	is copied logically). Afterwards, it isolates all modifications. On UNIX,
		1250	the same behaviour can be achieved by using operating system processes,
		1251	except that UNIX typically uses hardware built into the system to do this
		1252	efficiently, while the windows process emulation emulates this hardware in
		1253	software (rather efficiently, but of course it is still much slower than
		1254	dedicated hardware).
		1255
		1256	As mentioned before, loading code, modifying code, modifying data
		1257	structures and so on is only visible in the ithreads process doing the
		1258	modification, not in other ithread processes within the same OS process.
		1259
		1260	This is why "ithreads" do not implement threads for perl at all, only
		1261	processes. What makes it so bad is that on non-windows platforms, you can
		1262	actually take advantage of custom hardware for this purpose (as evidenced
		1263	by the forks module, which gives you the (i-) threads API, just much
		1264	faster).
		1265
		1266	Sharing data is in the i-threads model is done by transfering data
		1267	structures between threads using copying semantics, which is very slow -
		1268	shared data simply does not exist. Benchmarks using i-threads which are
		1269	communication-intensive show extremely bad behaviour with i-threads (in
		1270	fact, so bad that Coro, which cannot take direct advantage of multiple
		1271	CPUs, is often orders of magnitude faster because it shares data using
		1272	real threads, refer to my talk for details).
		1273
		1274	As summary, i-threads use threads to implement processes, while
		1275	the compatible forks module uses processes to emulate, uhm,
		1276	processes. I-threads slow down every perl program when enabled, and
		1277	outside of windows, serve no (or little) practical purpose, but
		1278	disadvantages every single-threaded Perl program.
		1279
		1280	This is the reason that I try to avoid the name "ithreads", as it is
		1281	misleading as it implies that it implements some kind of thread model for
		1282	perl, and prefer the name "windows process emulation", which describes the
		1283	actual use and behaviour of it much better.
761		1284
762	=head1 SEE ALSO	1285	=head1 SEE ALSO
763		1286
764	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.	1287	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
765		1288
…		…
778		1301
779	XS API: L<Coro::MakeMaker>.	1302	XS API: L<Coro::MakeMaker>.
780		1303
781	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.	1304	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
782		1305
783	=head1 AUTHOR	1306	=head1 AUTHOR/SUPPORT/CONTACT
784		1307
785	Marc Lehmann <schmorp@schmorp.de>	1308	Marc A. Lehmann <schmorp@schmorp.de>
786	http://home.schmorp.de/	1309	http://software.schmorp.de/pkg/Coro.html
787		1310
788	=cut	1311	=cut
789		1312

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Comparing Coro/Coro.pm (file contents): Revision 1.239 by root, Mon Nov 24 07:55:28 2008 UTC vs. Revision 1.337 by root, Sun Oct 4 13:10:22 2015 UTC

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Comparing Coro/Coro.pm (file contents):
Revision 1.239 by root, Mon Nov 24 07:55:28 2008 UTC vs.
Revision 1.337 by root, Sun Oct 4 13:10:22 2015 UTC