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

Comparing Coro/Coro.pm (file contents):
Revision 1.192 by root, Sun Jun 15 22:31:33 2008 UTC vs.
Revision 1.268 by root, Thu Oct 1 23:16:27 2009 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	Coro - coroutine process abstraction	3	Coro - the only real threads in perl
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use Coro;	7	use Coro;
8		8
11	print "2\n";	11	print "2\n";
12	cede; # yield back to main	12	cede; # yield back to main
13	print "4\n";	13	print "4\n";
14	};	14	};
15	print "1\n";	15	print "1\n";
16	cede; # yield to coroutine	16	cede; # yield to coro
17	print "3\n";	17	print "3\n";
18	cede; # and again	18	cede; # and again
19		19
20	# use locking	20	# use locking
		21	use Coro::Semaphore;
21	my $lock = new Coro::Semaphore;	22	my $lock = new Coro::Semaphore;
22	my $locked;	23	my $locked;
23		24
24	$lock->down;	25	$lock->down;
25	$locked = 1;	26	$locked = 1;
26	$lock->up;	27	$lock->up;
27		28
28	=head1 DESCRIPTION	29	=head1 DESCRIPTION
29		30
30	This module collection manages coroutines. Coroutines are similar to	31	For a tutorial-style introduction, please read the L<Coro::Intro>
31	threads but don't (in general) run in parallel at the same time even	32	manpage. This manpage mainly contains reference information.
32	on SMP machines. The specific flavor of coroutine used in this module
33	also guarantees you that it will not switch between coroutines unless
34	necessary, at easily-identified points in your program, so locking and
35	parallel access are rarely an issue, making coroutine programming much
36	safer and easier than threads programming.
37		33
38	Unlike a normal perl program, however, coroutines allow you to have	34	This module collection manages continuations in general, most often in
39	multiple running interpreters that share data, which is especially useful	35	the form of cooperative threads (also called coros, or simply "coro"
40	to code pseudo-parallel processes and for event-based programming, such as	36	in the documentation). They are similar to kernel threads but don't (in
41	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
42	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.
43		43
44	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
45	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 more
46	emulation coming from the Windows platform: On standard operating systems	46	details) ported to unix, and as such act as processes), Coro provides
47	they serve no purpose whatsoever, except by making your programs slow and	47	a full shared address space, which makes communication between threads
48	making them use a lot of memory. Best disable them when building perl, or	48	very easy. And Coro's threads are fast, too: disabling the Windows
49	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 runs over 300 times faster on a single core than
		52	perl's pseudo-threads on a quad core using all four cores.
50		53
		54	Coro achieves that by supporting multiple running interpreters that share
		55	data, which is especially useful to code pseudo-parallel processes and
		56	for event-based programming, such as multiple HTTP-GET requests running
		57	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
		58	into an event-based environment.
		59
51	In this module, coroutines are defined as "callchain + lexical variables +	60	In this module, a thread is defined as "callchain + lexical variables +
52	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,	61	some package variables + C stack), that is, a thread has its own callchain,
53	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
54	variables (see L<Coro::State> for more configuration).	63	variables (see L<Coro::State> for more configuration and background info).
		64
		65	See also the C<SEE ALSO> section at the end of this document - the Coro
		66	module family is quite large.
55		67
56	=cut	68	=cut
57		69
58	package Coro;	70	package Coro;
59		71
60	use strict;	72	use common::sense;
61	no warnings "uninitialized";	73
		74	use Carp ();
		75
		76	use Guard ();
62		77
63	use Coro::State;	78	use Coro::State;
64		79
65	use base qw(Coro::State Exporter);	80	use base qw(Coro::State Exporter);
66		81
67	our $idle; # idle handler	82	our $idle; # idle handler
68	our $main; # main coroutine	83	our $main; # main coro
69	our $current; # current coroutine	84	our $current; # current coro
70		85
71	our $VERSION = 4.743;	86	our $VERSION = 5.17;
72		87
73	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	88	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
74	our %EXPORT_TAGS = (	89	our %EXPORT_TAGS = (
75	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	90	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
76	);	91	);
77	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	92	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
78		93
		94	=head1 GLOBAL VARIABLES
		95
79	=over 4	96	=over 4
80		97
81	=item $Coro::main	98	=item $Coro::main
82		99
83	This variable stores the coroutine object that represents the main	100	This variable stores the Coro object that represents the main
84	program. While you cna C<ready> it and do most other things you can do to	101	program. While you cna C<ready> it and do most other things you can do to
85	coroutines, it is mainly useful to compare again C<$Coro::current>, to see	102	coro, it is mainly useful to compare again C<$Coro::current>, to see
86	wether you are running in the main program or not.	103	whether you are running in the main program or not.
87		104
88	=cut	105	=cut
89		106
90	$main = new Coro;	107	# $main is now being initialised by Coro::State
91		108
92	=item $Coro::current	109	=item $Coro::current
93		110
94	The coroutine object representing the current coroutine (the last	111	The Coro object representing the current coro (the last
95	coroutine that the Coro scheduler switched to). The initial value is	112	coro that the Coro scheduler switched to). The initial value is
96	C<$main> (of course).	113	C<$Coro::main> (of course).
97		114
98	This variable is B<strictly> I<read-only>. You can take copies of the	115	This variable is B<strictly> I<read-only>. You can take copies of the
99	value stored in it and use it as any other coroutine object, but you must	116	value stored in it and use it as any other Coro object, but you must
100	not otherwise modify the variable itself.	117	not otherwise modify the variable itself.
101		118
102	=cut	119	=cut
103		120
104	$main->{desc} = "[main::]";
105
106	# maybe some other module used Coro::Specific before...
107	$main->{_specific} = $current->{_specific}
108	if $current;
109
110	_set_current $main;
111
112	sub current() { $current } # [DEPRECATED]	121	sub current() { $current } # [DEPRECATED]
113		122
114	=item $Coro::idle	123	=item $Coro::idle
115		124
116	This variable is mainly useful to integrate Coro into event loops. It is	125	This variable is mainly useful to integrate Coro into event loops. It is
117	usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is	126	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
118	pretty low-level functionality.	127	pretty low-level functionality.
119		128
120	This variable stores a callback that is called whenever the scheduler	129	This variable stores either a Coro object or a callback.
		130
		131	If it is a callback, the it is called whenever the scheduler finds no
121	finds no ready coroutines to run. The default implementation prints	132	ready coros to run. The default implementation prints "FATAL:
122	"FATAL: deadlock detected" and exits, because the program has no other way	133	deadlock detected" and exits, because the program has no other way to
123	to continue.	134	continue.
124		135
		136	If it is a coro object, then this object will be readied (without
		137	invoking any ready hooks, however) when the scheduler finds no other ready
		138	coros to run.
		139
125	This hook is overwritten by modules such as C<Coro::Timer> and	140	This hook is overwritten by modules such as C<Coro::EV> and
126	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a	141	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
127	coroutine so the scheduler can run it.	142	coro so the scheduler can run it.
128		143
129	Note that the callback I<must not>, under any circumstances, block	144	Note that the callback I<must not>, under any circumstances, block
130	the current coroutine. Normally, this is achieved by having an "idle	145	the current coro. Normally, this is achieved by having an "idle
131	coroutine" that calls the event loop and then blocks again, and then	146	coro" that calls the event loop and then blocks again, and then
132	readying that coroutine in the idle handler.	147	readying that coro in the idle handler, or by simply placing the idle
		148	coro in this variable.
133		149
134	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this	150	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
135	technique.	151	technique.
136		152
137	Please note that if your callback recursively invokes perl (e.g. for event	153	Please note that if your callback recursively invokes perl (e.g. for event
138	handlers), then it must be prepared to be called recursively itself.	154	handlers), then it must be prepared to be called recursively itself.
139		155
140	=cut	156	=cut
141		157
142	$idle = sub {	158	$idle = sub {
143	require Carp;	159	warn "oi\n";#d#
144	Carp::croak ("FATAL: deadlock detected");	160	Carp::confess ("FATAL: deadlock detected");
145	};	161	};
146		162
147	sub _cancel {
148	my ($self) = @_;
149
150	# free coroutine data and mark as destructed
151	$self->_destroy
152	or return;
153
154	# call all destruction callbacks
155	$_->(@{$self->{_status}})
156	for @{(delete $self->{_on_destroy}) \|\| []};
157	}
158
159	# this coroutine is necessary because a coroutine	163	# this coro is necessary because a coro
160	# cannot destroy itself.	164	# cannot destroy itself.
161	my @destroy;	165	our @destroy;
162	my $manager;	166	our $manager;
163		167
164	$manager = new Coro sub {	168	$manager = new Coro sub {
165	while () {	169	while () {
166	(shift @destroy)->_cancel	170	Coro::State::cancel shift @destroy
167	while @destroy;	171	while @destroy;
168		172
169	&schedule;	173	&schedule;
170	}	174	}
171	};	175	};
172	$manager->desc ("[coro manager]");	176	$manager->{desc} = "[coro manager]";
173	$manager->prio (PRIO_MAX);	177	$manager->prio (PRIO_MAX);
174		178
175	=back	179	=back
176		180
177	=head2 SIMPLE COROUTINE CREATION	181	=head1 SIMPLE CORO CREATION
178		182
179	=over 4	183	=over 4
180		184
181	=item async { ... } [@args...]	185	=item async { ... } [@args...]
182		186
183	Create a new coroutine and return it's coroutine object (usually	187	Create a new coro and return its Coro object (usually
184	unused). The coroutine will be put into the ready queue, so	188	unused). The coro will be put into the ready queue, so
185	it will start running automatically on the next scheduler run.	189	it will start running automatically on the next scheduler run.
186		190
187	The first argument is a codeblock/closure that should be executed in the	191	The first argument is a codeblock/closure that should be executed in the
188	coroutine. When it returns argument returns the coroutine is automatically	192	coro. When it returns argument returns the coro is automatically
189	terminated.	193	terminated.
190		194
191	The remaining arguments are passed as arguments to the closure.	195	The remaining arguments are passed as arguments to the closure.
192		196
193	See the C<Coro::State::new> constructor for info about the coroutine	197	See the C<Coro::State::new> constructor for info about the coro
194	environment in which coroutines are executed.	198	environment in which coro are executed.
195		199
196	Calling C<exit> in a coroutine will do the same as calling exit outside	200	Calling C<exit> in a coro will do the same as calling exit outside
197	the coroutine. Likewise, when the coroutine dies, the program will exit,	201	the coro. Likewise, when the coro dies, the program will exit,
198	just as it would in the main program.	202	just as it would in the main program.
199		203
200	If you do not want that, you can provide a default C<die> handler, or	204	If you do not want that, you can provide a default C<die> handler, or
201	simply avoid dieing (by use of C<eval>).	205	simply avoid dieing (by use of C<eval>).
202		206
203	Example: Create a new coroutine that just prints its arguments.	207	Example: Create a new coro that just prints its arguments.
204		208
205	async {	209	async {
206	print "@_\n";	210	print "@_\n";
207	} 1,2,3,4;	211	} 1,2,3,4;
208		212
209	=cut
210
211	sub async(&@) {
212	my $coro = new Coro @_;
213	$coro->ready;
214	$coro
215	}
216
217	=item async_pool { ... } [@args...]	213	=item async_pool { ... } [@args...]
218		214
219	Similar to C<async>, but uses a coroutine pool, so you should not call	215	Similar to C<async>, but uses a coro pool, so you should not call
220	terminate or join on it (although you are allowed to), and you get a	216	terminate or join on it (although you are allowed to), and you get a
221	coroutine that might have executed other code already (which can be good	217	coro that might have executed other code already (which can be good
222	or bad :).	218	or bad :).
223		219
224	On the plus side, this function is faster than creating (and destroying)	220	On the plus side, this function is about twice as fast as creating (and
225	a completely new coroutine, so if you need a lot of generic coroutines in	221	destroying) a completely new coro, so if you need a lot of generic
226	quick successsion, use C<async_pool>, not C<async>.	222	coros in quick successsion, use C<async_pool>, not C<async>.
227		223
228	The code block is executed in an C<eval> context and a warning will be	224	The code block is executed in an C<eval> context and a warning will be
229	issued in case of an exception instead of terminating the program, as	225	issued in case of an exception instead of terminating the program, as
230	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>	226	C<async> does. As the coro is being reused, stuff like C<on_destroy>
231	will not work in the expected way, unless you call terminate or cancel,	227	will not work in the expected way, unless you call terminate or cancel,
232	which somehow defeats the purpose of pooling (but is fine in the	228	which somehow defeats the purpose of pooling (but is fine in the
233	exceptional case).	229	exceptional case).
234		230
235	The priority will be reset to C<0> after each run, tracing will be	231	The priority will be reset to C<0> after each run, tracing will be
236	disabled, the description will be reset and the default output filehandle	232	disabled, the description will be reset and the default output filehandle
237	gets restored, so you can change all these. Otherwise the coroutine will	233	gets restored, so you can change all these. Otherwise the coro will
238	be re-used "as-is": most notably if you change other per-coroutine global	234	be re-used "as-is": most notably if you change other per-coro global
239	stuff such as C<$/> you I<must needs> to revert that change, which is most	235	stuff such as C<$/> you I<must needs> revert that change, which is most
240	simply done by using local as in: C< local $/ >.	236	simply done by using local as in: C<< local $/ >>.
241		237
242	The pool size is limited to C<8> idle coroutines (this can be adjusted by	238	The idle pool size is limited to C<8> idle coros (this can be
243	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as	239	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
244	required.	240	coros as required.
245		241
246	If you are concerned about pooled coroutines growing a lot because a	242	If you are concerned about pooled coros growing a lot because a
247	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool	243	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
248	{ terminate }> once per second or so to slowly replenish the pool. In	244	{ terminate }> once per second or so to slowly replenish the pool. In
249	addition to that, when the stacks used by a handler grows larger than 16kb	245	addition to that, when the stacks used by a handler grows larger than 32kb
250	(adjustable via $Coro::POOL_RSS) it will also be destroyed.	246	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
251		247
252	=cut	248	=cut
253		249
254	our $POOL_SIZE = 8;	250	our $POOL_SIZE = 8;
255	our $POOL_RSS = 16 * 1024;	251	our $POOL_RSS = 32 * 1024;
256	our @async_pool;	252	our @async_pool;
257		253
258	sub pool_handler {	254	sub pool_handler {
259	my $cb;
260
261	while () {	255	while () {
262	eval {	256	eval {
263	while () {	257	&{&_pool_handler} while 1;
264	_pool_1 $cb;
265	&$cb;
266	_pool_2 $cb;
267	&schedule;
268	}
269	};	258	};
270		259
271	last if $@ eq "\3async_pool terminate\2\n";
272	warn $@ if $@;	260	warn $@ if $@;
273	}	261	}
274	}	262	}
275		263
276	sub async_pool(&@) {
277	# this is also inlined into the unlock_scheduler
278	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
279
280	$coro->{_invoke} = [@_];
281	$coro->ready;
282
283	$coro
284	}
285
286	=back	264	=back
287		265
288	=head2 STATIC METHODS	266	=head1 STATIC METHODS
289		267
290	Static methods are actually functions that operate on the current coroutine.	268	Static methods are actually functions that implicitly operate on the
		269	current coro.
291		270
292	=over 4	271	=over 4
293		272
294	=item schedule	273	=item schedule
295		274
296	Calls the scheduler. The scheduler will find the next coroutine that is	275	Calls the scheduler. The scheduler will find the next coro that is
297	to be run from the ready queue and switches to it. The next coroutine	276	to be run from the ready queue and switches to it. The next coro
298	to be run is simply the one with the highest priority that is longest	277	to be run is simply the one with the highest priority that is longest
299	in its ready queue. If there is no coroutine ready, it will clal the	278	in its ready queue. If there is no coro ready, it will clal the
300	C<$Coro::idle> hook.	279	C<$Coro::idle> hook.
301		280
302	Please note that the current coroutine will I<not> be put into the ready	281	Please note that the current coro will I<not> be put into the ready
303	queue, so calling this function usually means you will never be called	282	queue, so calling this function usually means you will never be called
304	again unless something else (e.g. an event handler) calls C<< ->ready >>,	283	again unless something else (e.g. an event handler) calls C<< ->ready >>,
305	thus waking you up.	284	thus waking you up.
306		285
307	This makes C<schedule> I<the> generic method to use to block the current	286	This makes C<schedule> I<the> generic method to use to block the current
308	coroutine and wait for events: first you remember the current coroutine in	287	coro and wait for events: first you remember the current coro in
309	a variable, then arrange for some callback of yours to call C<< ->ready	288	a variable, then arrange for some callback of yours to call C<< ->ready
310	>> on that once some event happens, and last you call C<schedule> to put	289	>> on that once some event happens, and last you call C<schedule> to put
311	yourself to sleep. Note that a lot of things can wake your coroutine up,	290	yourself to sleep. Note that a lot of things can wake your coro up,
312	so you need to check wether the event indeed happened, e.g. by storing the	291	so you need to check whether the event indeed happened, e.g. by storing the
313	status in a variable.	292	status in a variable.
314		293
315	The canonical way to wait on external events is this:	294	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
316		295
317	{	296	=item cede
318	# remember current coroutine
319	my $current = $Coro::current;
320		297
321	# register a hypothetical event handler	298	"Cede" to other coros. This function puts the current coro into
322	on_event_invoke sub {	299	the ready queue and calls C<schedule>, which has the effect of giving
323	# wake up sleeping coroutine	300	up the current "timeslice" to other coros of the same or higher
324	$current->ready;	301	priority. Once your coro gets its turn again it will automatically be
325	undef $current;	302	resumed.
		303
		304	This function is often called C<yield> in other languages.
		305
		306	=item Coro::cede_notself
		307
		308	Works like cede, but is not exported by default and will cede to I<any>
		309	coro, regardless of priority. This is useful sometimes to ensure
		310	progress is made.
		311
		312	=item terminate [arg...]
		313
		314	Terminates the current coro with the given status values (see L<cancel>).
		315
		316	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
		317
		318	These function install enter and leave winders in the current scope. The
		319	enter block will be executed when on_enter is called and whenever the
		320	current coro is re-entered by the scheduler, while the leave block is
		321	executed whenever the current coro is blocked by the scheduler, and
		322	also when the containing scope is exited (by whatever means, be it exit,
		323	die, last etc.).
		324
		325	I<Neither invoking the scheduler, nor exceptions, are allowed within those
		326	BLOCKs>. That means: do not even think about calling C<die> without an
		327	eval, and do not even think of entering the scheduler in any way.
		328
		329	Since both BLOCKs are tied to the current scope, they will automatically
		330	be removed when the current scope exits.
		331
		332	These functions implement the same concept as C<dynamic-wind> in scheme
		333	does, and are useful when you want to localise some resource to a specific
		334	coro.
		335
		336	They slow down thread switching considerably for coros that use them
		337	(about 40% for a BLOCK with a single assignment, so thread switching is
		338	still reasonably fast if the handlers are fast).
		339
		340	These functions are best understood by an example: The following function
		341	will change the current timezone to "Antarctica/South_Pole", which
		342	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
		343	which remember/change the current timezone and restore the previous
		344	value, respectively, the timezone is only changed for the coro that
		345	installed those handlers.
		346
		347	use POSIX qw(tzset);
		348
		349	async {
		350	my $old_tz; # store outside TZ value here
		351
		352	Coro::on_enter {
		353	$old_tz = $ENV{TZ}; # remember the old value
		354
		355	$ENV{TZ} = "Antarctica/South_Pole";
		356	tzset; # enable new value
326	};	357	};
327		358
328	# call schedule until event occurred.	359	Coro::on_leave {
329	# in case we are woken up for other reasons	360	$ENV{TZ} = $old_tz;
330	# (current still defined), loop.	361	tzset; # restore old value
331	Coro::schedule while $current;	362	};
		363
		364	# at this place, the timezone is Antarctica/South_Pole,
		365	# without disturbing the TZ of any other coro.
332	}	366	};
333		367
334	=item cede	368	This can be used to localise about any resource (locale, uid, current
		369	working directory etc.) to a block, despite the existance of other
		370	coros.
335		371
336	"Cede" to other coroutines. This function puts the current coroutine into	372	Another interesting example implements time-sliced multitasking using
337	the ready queue and calls C<schedule>, which has the effect of giving	373	interval timers (this could obviously be optimised, but does the job):
338	up the current "timeslice" to other coroutines of the same or higher
339	priority. Once your coroutine gets its turn again it will automatically be
340	resumed.
341		374
342	This function is often called C<yield> in other languages.	375	# "timeslice" the given block
		376	sub timeslice(&) {
		377	use Time::HiRes ();
343		378
344	=item Coro::cede_notself	379	Coro::on_enter {
		380	# on entering the thread, we set an VTALRM handler to cede
		381	$SIG{VTALRM} = sub { cede };
		382	# and then start the interval timer
		383	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
		384	};
		385	Coro::on_leave {
		386	# on leaving the thread, we stop the interval timer again
		387	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
		388	};
345		389
346	Works like cede, but is not exported by default and will cede to I<any>	390	&{+shift};
347	coroutine, regardless of priority. This is useful sometimes to ensure	391	}
348	progress is made.
349		392
350	=item terminate [arg...]	393	# use like this:
		394	timeslice {
		395	# The following is an endless loop that would normally
		396	# monopolise the process. Since it runs in a timesliced
		397	# environment, it will regularly cede to other threads.
		398	while () { }
		399	};
351		400
352	Terminates the current coroutine with the given status values (see L<cancel>).
353		401
354	=item killall	402	=item killall
355		403
356	Kills/terminates/cancels all coroutines except the currently running	404	Kills/terminates/cancels all coros except the currently running one.
357	one. This is useful after a fork, either in the child or the parent, as
358	usually only one of them should inherit the running coroutines.
359		405
360	Note that while this will try to free some of the main programs resources,	406	Note that while this will try to free some of the main interpreter
		407	resources if the calling coro isn't the main coro, but one
361	you cnanot free all of them, so if a coroutine that is not the main	408	cannot free all of them, so if a coro that is not the main coro
362	program calls this function, there will be some one-time resource leak.	409	calls this function, there will be some one-time resource leak.
363		410
364	=cut	411	=cut
365
366	sub terminate {
367	$current->cancel (@_);
368	}
369		412
370	sub killall {	413	sub killall {
371	for (Coro::State::list) {	414	for (Coro::State::list) {
372	$_->cancel	415	$_->cancel
373	if $_ != $current && UNIVERSAL::isa $_, "Coro";	416	if $_ != $current && UNIVERSAL::isa $_, "Coro";
374	}	417	}
375	}	418	}
376		419
377	=back	420	=back
378		421
379	=head2 COROUTINE METHODS	422	=head1 CORO OBJECT METHODS
380		423
381	These are the methods you can call on coroutine objects (or to create	424	These are the methods you can call on coro objects (or to create
382	them).	425	them).
383		426
384	=over 4	427	=over 4
385		428
386	=item new Coro \&sub [, @args...]	429	=item new Coro \&sub [, @args...]
387		430
388	Create a new coroutine and return it. When the sub returns, the coroutine	431	Create a new coro and return it. When the sub returns, the coro
389	automatically terminates as if C<terminate> with the returned values were	432	automatically terminates as if C<terminate> with the returned values were
390	called. To make the coroutine run you must first put it into the ready	433	called. To make the coro run you must first put it into the ready
391	queue by calling the ready method.	434	queue by calling the ready method.
392		435
393	See C<async> and C<Coro::State::new> for additional info about the	436	See C<async> and C<Coro::State::new> for additional info about the
394	coroutine environment.	437	coro environment.
395		438
396	=cut	439	=cut
397		440
398	sub _run_coro {	441	sub _coro_run {
399	terminate &{+shift};	442	terminate &{+shift};
400	}	443	}
401		444
402	sub new {
403	my $class = shift;
404
405	$class->SUPER::new (\&_run_coro, @_)
406	}
407
408	=item $success = $coroutine->ready	445	=item $success = $coro->ready
409		446
410	Put the given coroutine into the end of its ready queue (there is one	447	Put the given coro into the end of its ready queue (there is one
411	queue for each priority) and return true. If the coroutine is already in	448	queue for each priority) and return true. If the coro is already in
412	the ready queue, do nothing and return false.	449	the ready queue, do nothing and return false.
413		450
414	This ensures that the scheduler will resume this coroutine automatically	451	This ensures that the scheduler will resume this coro automatically
415	once all the coroutines of higher priority and all coroutines of the same	452	once all the coro of higher priority and all coro of the same
416	priority that were put into the ready queue earlier have been resumed.	453	priority that were put into the ready queue earlier have been resumed.
417		454
		455	=item $coro->suspend
		456
		457	Suspends the specified coro. A suspended coro works just like any other
		458	coro, except that the scheduler will not select a suspended coro for
		459	execution.
		460
		461	Suspending a coro can be useful when you want to keep the coro from
		462	running, but you don't want to destroy it, or when you want to temporarily
		463	freeze a coro (e.g. for debugging) to resume it later.
		464
		465	A scenario for the former would be to suspend all (other) coros after a
		466	fork and keep them alive, so their destructors aren't called, but new
		467	coros can be created.
		468
		469	=item $coro->resume
		470
		471	If the specified coro was suspended, it will be resumed. Note that when
		472	the coro was in the ready queue when it was suspended, it might have been
		473	unreadied by the scheduler, so an activation might have been lost.
		474
		475	To avoid this, it is best to put a suspended coro into the ready queue
		476	unconditionally, as every synchronisation mechanism must protect itself
		477	against spurious wakeups, and the one in the Coro family certainly do
		478	that.
		479
418	=item $is_ready = $coroutine->is_ready	480	=item $is_ready = $coro->is_ready
419		481
420	Return wether the coroutine is currently the ready queue or not,	482	Returns true iff the Coro object is in the ready queue. Unless the Coro
		483	object gets destroyed, it will eventually be scheduled by the scheduler.
421		484
		485	=item $is_running = $coro->is_running
		486
		487	Returns true iff the Coro object is currently running. Only one Coro object
		488	can ever be in the running state (but it currently is possible to have
		489	multiple running Coro::States).
		490
		491	=item $is_suspended = $coro->is_suspended
		492
		493	Returns true iff this Coro object has been suspended. Suspended Coros will
		494	not ever be scheduled.
		495
422	=item $coroutine->cancel (arg...)	496	=item $coro->cancel (arg...)
423		497
424	Terminates the given coroutine and makes it return the given arguments as	498	Terminates the given Coro and makes it return the given arguments as
425	status (default: the empty list). Never returns if the coroutine is the	499	status (default: the empty list). Never returns if the Coro is the
426	current coroutine.	500	current Coro.
427		501
428	=cut	502	=cut
429		503
430	sub cancel {	504	sub cancel {
431	my $self = shift;	505	my $self = shift;
432	$self->{_status} = [@_];
433		506
434	if ($current == $self) {	507	if ($current == $self) {
435	push @destroy, $self;	508	terminate @_;
436	$manager->ready;
437	&schedule while 1;
438	} else {	509	} else {
439	$self->_cancel;	510	$self->{_status} = [@_];
		511	Coro::State::cancel $self;
440	}	512	}
441	}	513	}
442		514
		515	=item $coro->schedule_to
		516
		517	Puts the current coro to sleep (like C<Coro::schedule>), but instead
		518	of continuing with the next coro from the ready queue, always switch to
		519	the given coro object (regardless of priority etc.). The readyness
		520	state of that coro isn't changed.
		521
		522	This is an advanced method for special cases - I'd love to hear about any
		523	uses for this one.
		524
		525	=item $coro->cede_to
		526
		527	Like C<schedule_to>, but puts the current coro into the ready
		528	queue. This has the effect of temporarily switching to the given
		529	coro, and continuing some time later.
		530
		531	This is an advanced method for special cases - I'd love to hear about any
		532	uses for this one.
		533
		534	=item $coro->throw ([$scalar])
		535
		536	If C<$throw> is specified and defined, it will be thrown as an exception
		537	inside the coro at the next convenient point in time. Otherwise
		538	clears the exception object.
		539
		540	Coro will check for the exception each time a schedule-like-function
		541	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		542	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		543	detect this case and return early in case an exception is pending.
		544
		545	The exception object will be thrown "as is" with the specified scalar in
		546	C<$@>, i.e. if it is a string, no line number or newline will be appended
		547	(unlike with C<die>).
		548
		549	This can be used as a softer means than C<cancel> to ask a coro to
		550	end itself, although there is no guarantee that the exception will lead to
		551	termination, and if the exception isn't caught it might well end the whole
		552	program.
		553
		554	You might also think of C<throw> as being the moral equivalent of
		555	C<kill>ing a coro with a signal (in this case, a scalar).
		556
443	=item $coroutine->join	557	=item $coro->join
444		558
445	Wait until the coroutine terminates and return any values given to the	559	Wait until the coro terminates and return any values given to the
446	C<terminate> or C<cancel> functions. C<join> can be called concurrently	560	C<terminate> or C<cancel> functions. C<join> can be called concurrently
447	from multiple coroutines, and all will be resumed and given the status	561	from multiple coro, and all will be resumed and given the status
448	return once the C<$coroutine> terminates.	562	return once the C<$coro> terminates.
449		563
450	=cut	564	=cut
451		565
452	sub join {	566	sub join {
453	my $self = shift;	567	my $self = shift;
…		…
464	}	578	}
465		579
466	wantarray ? @{$self->{_status}} : $self->{_status}[0];	580	wantarray ? @{$self->{_status}} : $self->{_status}[0];
467	}	581	}
468		582
469	=item $coroutine->on_destroy (\&cb)	583	=item $coro->on_destroy (\&cb)
470		584
471	Registers a callback that is called when this coroutine gets destroyed,	585	Registers a callback that is called when this coro gets destroyed,
472	but before it is joined. The callback gets passed the terminate arguments,	586	but before it is joined. The callback gets passed the terminate arguments,
473	if any, and I<must not> die, under any circumstances.	587	if any, and I<must not> die, under any circumstances.
474		588
475	=cut	589	=cut
476		590
…		…
478	my ($self, $cb) = @_;	592	my ($self, $cb) = @_;
479		593
480	push @{ $self->{_on_destroy} }, $cb;	594	push @{ $self->{_on_destroy} }, $cb;
481	}	595	}
482		596
483	=item $oldprio = $coroutine->prio ($newprio)	597	=item $oldprio = $coro->prio ($newprio)
484		598
485	Sets (or gets, if the argument is missing) the priority of the	599	Sets (or gets, if the argument is missing) the priority of the
486	coroutine. Higher priority coroutines get run before lower priority	600	coro. Higher priority coro get run before lower priority
487	coroutines. Priorities are small signed integers (currently -4 .. +3),	601	coro. Priorities are small signed integers (currently -4 .. +3),
488	that you can refer to using PRIO_xxx constants (use the import tag :prio	602	that you can refer to using PRIO_xxx constants (use the import tag :prio
489	to get then):	603	to get then):
490		604
491	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	605	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
492	3 > 1 > 0 > -1 > -3 > -4	606	3 > 1 > 0 > -1 > -3 > -4
493		607
494	# set priority to HIGH	608	# set priority to HIGH
495	current->prio(PRIO_HIGH);	609	current->prio (PRIO_HIGH);
496		610
497	The idle coroutine ($Coro::idle) always has a lower priority than any	611	The idle coro ($Coro::idle) always has a lower priority than any
498	existing coroutine.	612	existing coro.
499		613
500	Changing the priority of the current coroutine will take effect immediately,	614	Changing the priority of the current coro will take effect immediately,
501	but changing the priority of coroutines in the ready queue (but not	615	but changing the priority of coro in the ready queue (but not
502	running) will only take effect after the next schedule (of that	616	running) will only take effect after the next schedule (of that
503	coroutine). This is a bug that will be fixed in some future version.	617	coro). This is a bug that will be fixed in some future version.
504		618
505	=item $newprio = $coroutine->nice ($change)	619	=item $newprio = $coro->nice ($change)
506		620
507	Similar to C<prio>, but subtract the given value from the priority (i.e.	621	Similar to C<prio>, but subtract the given value from the priority (i.e.
508	higher values mean lower priority, just as in unix).	622	higher values mean lower priority, just as in unix).
509		623
510	=item $olddesc = $coroutine->desc ($newdesc)	624	=item $olddesc = $coro->desc ($newdesc)
511		625
512	Sets (or gets in case the argument is missing) the description for this	626	Sets (or gets in case the argument is missing) the description for this
513	coroutine. This is just a free-form string you can associate with a coroutine.	627	coro. This is just a free-form string you can associate with a
		628	coro.
514		629
515	This method simply sets the C<< $coroutine->{desc} >> member to the given string. You	630	This method simply sets the C<< $coro->{desc} >> member to the given
516	can modify this member directly if you wish.	631	string. You can modify this member directly if you wish.
517
518	=item $coroutine->throw ([$scalar])
519
520	If C<$throw> is specified and defined, it will be thrown as an exception
521	inside the coroutine at the next convinient point in time (usually after
522	it gains control at the next schedule/transfer/cede). Otherwise clears the
523	exception object.
524
525	The exception object will be thrown "as is" with the specified scalar in
526	C<$@>, i.e. if it is a string, no line number or newline will be appended
527	(unlike with C<die>).
528
529	This can be used as a softer means than C<cancel> to ask a coroutine to
530	end itself, although there is no guarentee that the exception will lead to
531	termination, and if the exception isn't caught it might well end the whole
532	program.
533		632
534	=cut	633	=cut
535		634
536	sub desc {	635	sub desc {
537	my $old = $_[0]{desc};	636	my $old = $_[0]{desc};
538	$_[0]{desc} = $_[1] if @_ > 1;	637	$_[0]{desc} = $_[1] if @_ > 1;
539	$old;	638	$old;
540	}	639	}
541		640
		641	sub transfer {
		642	require Carp;
		643	Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
		644	}
		645
542	=back	646	=back
543		647
544	=head2 GLOBAL FUNCTIONS	648	=head1 GLOBAL FUNCTIONS
545		649
546	=over 4	650	=over 4
547		651
548	=item Coro::nready	652	=item Coro::nready
549		653
550	Returns the number of coroutines that are currently in the ready state,	654	Returns the number of coro that are currently in the ready state,
551	i.e. that can be switched to by calling C<schedule> directory or	655	i.e. that can be switched to by calling C<schedule> directory or
552	indirectly. The value C<0> means that the only runnable coroutine is the	656	indirectly. The value C<0> means that the only runnable coro is the
553	currently running one, so C<cede> would have no effect, and C<schedule>	657	currently running one, so C<cede> would have no effect, and C<schedule>
554	would cause a deadlock unless there is an idle handler that wakes up some	658	would cause a deadlock unless there is an idle handler that wakes up some
555	coroutines.	659	coro.
556		660
557	=item my $guard = Coro::guard { ... }	661	=item my $guard = Coro::guard { ... }
558		662
559	This creates and returns a guard object. Nothing happens until the object	663	This function still exists, but is deprecated. Please use the
560	gets destroyed, in which case the codeblock given as argument will be	664	C<Guard::guard> function instead.
561	executed. This is useful to free locks or other resources in case of a
562	runtime error or when the coroutine gets canceled, as in both cases the
563	guard block will be executed. The guard object supports only one method,
564	C<< ->cancel >>, which will keep the codeblock from being executed.
565		665
566	Example: set some flag and clear it again when the coroutine gets canceled
567	or the function returns:
568
569	sub do_something {
570	my $guard = Coro::guard { $busy = 0 };
571	$busy = 1;
572
573	# do something that requires $busy to be true
574	}
575
576	=cut	666	=cut
577		667
578	sub guard(&) {	668	BEGIN { *guard = \&Guard::guard }
579	bless \(my $cb = $_[0]), "Coro::guard"
580	}
581
582	sub Coro::guard::cancel {
583	${$_[0]} = sub { };
584	}
585
586	sub Coro::guard::DESTROY {
587	${$_[0]}->();
588	}
589
590		669
591	=item unblock_sub { ... }	670	=item unblock_sub { ... }
592		671
593	This utility function takes a BLOCK or code reference and "unblocks" it,	672	This utility function takes a BLOCK or code reference and "unblocks" it,
594	returning a new coderef. Unblocking means that calling the new coderef	673	returning a new coderef. Unblocking means that calling the new coderef
595	will return immediately without blocking, returning nothing, while the	674	will return immediately without blocking, returning nothing, while the
596	original code ref will be called (with parameters) from within another	675	original code ref will be called (with parameters) from within another
597	coroutine.	676	coro.
598		677
599	The reason this function exists is that many event libraries (such as the	678	The reason this function exists is that many event libraries (such as the
600	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form	679	venerable L<Event\|Event> module) are not thread-safe (a weaker form
601	of thread-safety). This means you must not block within event callbacks,	680	of reentrancy). This means you must not block within event callbacks,
602	otherwise you might suffer from crashes or worse. The only event library	681	otherwise you might suffer from crashes or worse. The only event library
603	currently known that is safe to use without C<unblock_sub> is L<EV>.	682	currently known that is safe to use without C<unblock_sub> is L<EV>.
604		683
605	This function allows your callbacks to block by executing them in another	684	This function allows your callbacks to block by executing them in another
606	coroutine where it is safe to block. One example where blocking is handy	685	coro where it is safe to block. One example where blocking is handy
607	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	686	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
608	disk, for example.	687	disk, for example.
609		688
610	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	689	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
611	creating event callbacks that want to block.	690	creating event callbacks that want to block.
612		691
613	If your handler does not plan to block (e.g. simply sends a message to	692	If your handler does not plan to block (e.g. simply sends a message to
614	another coroutine, or puts some other coroutine into the ready queue),	693	another coro, or puts some other coro into the ready queue), there is
615	there is no reason to use C<unblock_sub>.	694	no reason to use C<unblock_sub>.
616		695
617	Note that you also need to use C<unblock_sub> for any other callbacks that	696	Note that you also need to use C<unblock_sub> for any other callbacks that
618	are indirectly executed by any C-based event loop. For example, when you	697	are indirectly executed by any C-based event loop. For example, when you
619	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it	698	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
620	provides callbacks that are the result of some event callback, then you	699	provides callbacks that are the result of some event callback, then you
…		…
629	# return immediately and can be reused) and because we cannot cede	708	# return immediately and can be reused) and because we cannot cede
630	# inside an event callback.	709	# inside an event callback.
631	our $unblock_scheduler = new Coro sub {	710	our $unblock_scheduler = new Coro sub {
632	while () {	711	while () {
633	while (my $cb = pop @unblock_queue) {	712	while (my $cb = pop @unblock_queue) {
634	# this is an inlined copy of async_pool	713	&async_pool (@$cb);
635	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
636		714
637	$coro->{_invoke} = $cb;
638	$coro->ready;
639	cede; # for short-lived callbacks, this reduces pressure on the coro pool	715	# for short-lived callbacks, this reduces pressure on the coro pool
		716	# as the chance is very high that the async_poll coro will be back
		717	# in the idle state when cede returns
		718	cede;
640	}	719	}
641	schedule; # sleep well	720	schedule; # sleep well
642	}	721	}
643	};	722	};
644	$unblock_scheduler->desc ("[unblock_sub scheduler]");	723	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
645		724
646	sub unblock_sub(&) {	725	sub unblock_sub(&) {
647	my $cb = shift;	726	my $cb = shift;
648		727
649	sub {	728	sub {
650	unshift @unblock_queue, [$cb, @_];	729	unshift @unblock_queue, [$cb, @_];
651	$unblock_scheduler->ready;	730	$unblock_scheduler->ready;
652	}	731	}
653	}	732	}
654		733
		734	=item $cb = Coro::rouse_cb
		735
		736	Create and return a "rouse callback". That's a code reference that,
		737	when called, will remember a copy of its arguments and notify the owner
		738	coro of the callback.
		739
		740	See the next function.
		741
		742	=item @args = Coro::rouse_wait [$cb]
		743
		744	Wait for the specified rouse callback (or the last one that was created in
		745	this coro).
		746
		747	As soon as the callback is invoked (or when the callback was invoked
		748	before C<rouse_wait>), it will return the arguments originally passed to
		749	the rouse callback. In scalar context, that means you get the I<last>
		750	argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
		751	statement at the end.
		752
		753	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		754
655	=back	755	=back
656		756
657	=cut	757	=cut
658		758
659	1;	759	1;
660		760
		761	=head1 HOW TO WAIT FOR A CALLBACK
		762
		763	It is very common for a coro to wait for some callback to be
		764	called. This occurs naturally when you use coro in an otherwise
		765	event-based program, or when you use event-based libraries.
		766
		767	These typically register a callback for some event, and call that callback
		768	when the event occured. In a coro, however, you typically want to
		769	just wait for the event, simplyifying things.
		770
		771	For example C<< AnyEvent->child >> registers a callback to be called when
		772	a specific child has exited:
		773
		774	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		775
		776	But from within a coro, you often just want to write this:
		777
		778	my $status = wait_for_child $pid;
		779
		780	Coro offers two functions specifically designed to make this easy,
		781	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		782
		783	The first function, C<rouse_cb>, generates and returns a callback that,
		784	when invoked, will save its arguments and notify the coro that
		785	created the callback.
		786
		787	The second function, C<rouse_wait>, waits for the callback to be called
		788	(by calling C<schedule> to go to sleep) and returns the arguments
		789	originally passed to the callback.
		790
		791	Using these functions, it becomes easy to write the C<wait_for_child>
		792	function mentioned above:
		793
		794	sub wait_for_child($) {
		795	my ($pid) = @_;
		796
		797	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		798
		799	my ($rpid, $rstatus) = Coro::rouse_wait;
		800	$rstatus
		801	}
		802
		803	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		804	you can roll your own, using C<schedule>:
		805
		806	sub wait_for_child($) {
		807	my ($pid) = @_;
		808
		809	# store the current coro in $current,
		810	# and provide result variables for the closure passed to ->child
		811	my $current = $Coro::current;
		812	my ($done, $rstatus);
		813
		814	# pass a closure to ->child
		815	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		816	$rstatus = $_[1]; # remember rstatus
		817	$done = 1; # mark $rstatus as valud
		818	});
		819
		820	# wait until the closure has been called
		821	schedule while !$done;
		822
		823	$rstatus
		824	}
		825
		826
661	=head1 BUGS/LIMITATIONS	827	=head1 BUGS/LIMITATIONS
662		828
		829	=over 4
		830
		831	=item fork with pthread backend
		832
		833	When Coro is compiled using the pthread backend (which isn't recommended
		834	but required on many BSDs as their libcs are completely broken), then
		835	coro will not survive a fork. There is no known workaround except to
		836	fix your libc and use a saner backend.
		837
		838	=item perl process emulation ("threads")
		839
663	This module is not perl-pseudo-thread-safe. You should only ever use this	840	This module is not perl-pseudo-thread-safe. You should only ever use this
664	module from the same thread (this requirement might be removed in the	841	module from the first thread (this requirement might be removed in the
665	future to allow per-thread schedulers, but Coro::State does not yet allow	842	future to allow per-thread schedulers, but Coro::State does not yet allow
666	this). I recommend disabling thread support and using processes, as this	843	this). I recommend disabling thread support and using processes, as having
667	is much faster and uses less memory.	844	the windows process emulation enabled under unix roughly halves perl
		845	performance, even when not used.
		846
		847	=item coro switching is not signal safe
		848
		849	You must not switch to another coro from within a signal handler
		850	(only relevant with %SIG - most event libraries provide safe signals).
		851
		852	That means you I<MUST NOT> call any function that might "block" the
		853	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		854	anything that calls those. Everything else, including calling C<ready>,
		855	works.
		856
		857	=back
		858
		859
		860	=head1 WINDOWS PROCESS EMULATION
		861
		862	A great many people seem to be confused about ithreads (for example, Chip
		863	Salzenberg called me unintelligent, incapable, stupid and gullible,
		864	while in the same mail making rather confused statements about perl
		865	ithreads (for example, that memory or files would be shared), showing his
		866	lack of understanding of this area - if it is hard to understand for Chip,
		867	it is probably not obvious to everybody).
		868
		869	What follows is an ultra-condensed version of my talk about threads in
		870	scripting languages given onthe perl workshop 2009:
		871
		872	The so-called "ithreads" were originally implemented for two reasons:
		873	first, to (badly) emulate unix processes on native win32 perls, and
		874	secondly, to replace the older, real thread model ("5.005-threads").
		875
		876	It does that by using threads instead of OS processes. The difference
		877	between processes and threads is that threads share memory (and other
		878	state, such as files) between threads within a single process, while
		879	processes do not share anything (at least not semantically). That
		880	means that modifications done by one thread are seen by others, while
		881	modifications by one process are not seen by other processes.
		882
		883	The "ithreads" work exactly like that: when creating a new ithreads
		884	process, all state is copied (memory is copied physically, files and code
		885	is copied logically). Afterwards, it isolates all modifications. On UNIX,
		886	the same behaviour can be achieved by using operating system processes,
		887	except that UNIX typically uses hardware built into the system to do this
		888	efficiently, while the windows process emulation emulates this hardware in
		889	software (rather efficiently, but of course it is still much slower than
		890	dedicated hardware).
		891
		892	As mentioned before, loading code, modifying code, modifying data
		893	structures and so on is only visible in the ithreads process doing the
		894	modification, not in other ithread processes within the same OS process.
		895
		896	This is why "ithreads" do not implement threads for perl at all, only
		897	processes. What makes it so bad is that on non-windows platforms, you can
		898	actually take advantage of custom hardware for this purpose (as evidenced
		899	by the forks module, which gives you the (i-) threads API, just much
		900	faster).
		901
		902	Sharing data is in the i-threads model is done by transfering data
		903	structures between threads using copying semantics, which is very slow -
		904	shared data simply does not exist. Benchmarks using i-threads which are
		905	communication-intensive show extremely bad behaviour with i-threads (in
		906	fact, so bad that Coro, which cannot take direct advantage of multiple
		907	CPUs, is often orders of magnitude faster because it shares data using
		908	real threads, refer to my talk for details).
		909
		910	As summary, i-threads use threads to implement processes, while
		911	the compatible forks module uses processes to emulate, uhm,
		912	processes. I-threads slow down every perl program when enabled, and
		913	outside of windows, serve no (or little) practical purpose, but
		914	disadvantages every single-threaded Perl program.
		915
		916	This is the reason that I try to avoid the name "ithreads", as it is
		917	misleading as it implies that it implements some kind of thread model for
		918	perl, and prefer the name "windows process emulation", which describes the
		919	actual use and behaviour of it much better.
668		920
669	=head1 SEE ALSO	921	=head1 SEE ALSO
670		922
671	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.	923	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
672		924
673	Debugging: L<Coro::Debug>.	925	Debugging: L<Coro::Debug>.
674		926
675	Support/Utility: L<Coro::Specific>, L<Coro::Util>.	927	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
676		928
677	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.	929	Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
		930	L<Coro::SemaphoreSet>, L<Coro::RWLock>.
678		931
679	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.	932	I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
680		933
681	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.	934	Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
		935	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
		936	L<Coro::Select>.
682		937
683	XS API: L<Coro::MakeMaker>.	938	XS API: L<Coro::MakeMaker>.
684		939
685	Low level Configuration, Coroutine Environment: L<Coro::State>.	940	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
686		941
687	=head1 AUTHOR	942	=head1 AUTHOR
688		943
689	Marc Lehmann <schmorp@schmorp.de>	944	Marc Lehmann <schmorp@schmorp.de>
690	http://home.schmorp.de/	945	http://home.schmorp.de/

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Comparing Coro/Coro.pm (file contents):
Revision 1.192 by root, Sun Jun 15 22:31:33 2008 UTC vs.
Revision 1.268 by root, Thu Oct 1 23:16:27 2009 UTC