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

Comparing Coro/Coro.pm (file contents):
Revision 1.186 by root, Sun May 25 01:32:36 2008 UTC vs.
Revision 1.269 by root, Thu Oct 1 23:25:03 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 = '4.72';	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	$idle = sub {
143	require Carp;
144	Carp::croak ("FATAL: deadlock detected");	159	Carp::confess ("FATAL: deadlock detected");
145	};	160	};
146		161
147	sub _cancel {
148	my ($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	162	# this coro is necessary because a coro
160	# cannot destroy itself.	163	# cannot destroy itself.
161	my @destroy;	164	our @destroy;
162	my $manager;	165	our $manager;
163		166
164	$manager = new Coro sub {	167	$manager = new Coro sub {
165	while () {	168	while () {
166	(shift @destroy)->_cancel	169	Coro::State::cancel shift @destroy
167	while @destroy;	170	while @destroy;
168		171
169	&schedule;	172	&schedule;
170	}	173	}
171	};	174	};
172	$manager->desc ("[coro manager]");	175	$manager->{desc} = "[coro manager]";
173	$manager->prio (PRIO_MAX);	176	$manager->prio (PRIO_MAX);
174		177
175	=back	178	=back
176		179
177	=head2 SIMPLE COROUTINE CREATION	180	=head1 SIMPLE CORO CREATION
178		181
179	=over 4	182	=over 4
180		183
181	=item async { ... } [@args...]	184	=item async { ... } [@args...]
182		185
183	Create a new coroutine and return it's coroutine object (usually	186	Create a new coro and return its Coro object (usually
184	unused). The coroutine will be put into the ready queue, so	187	unused). The coro will be put into the ready queue, so
185	it will start running automatically on the next scheduler run.	188	it will start running automatically on the next scheduler run.
186		189
187	The first argument is a codeblock/closure that should be executed in the	190	The first argument is a codeblock/closure that should be executed in the
188	coroutine. When it returns argument returns the coroutine is automatically	191	coro. When it returns argument returns the coro is automatically
189	terminated.	192	terminated.
190		193
191	The remaining arguments are passed as arguments to the closure.	194	The remaining arguments are passed as arguments to the closure.
192		195
193	See the C<Coro::State::new> constructor for info about the coroutine	196	See the C<Coro::State::new> constructor for info about the coro
194	environment in which coroutines are executed.	197	environment in which coro are executed.
195		198
196	Calling C<exit> in a coroutine will do the same as calling exit outside	199	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,	200	the coro. Likewise, when the coro dies, the program will exit,
198	just as it would in the main program.	201	just as it would in the main program.
199		202
200	If you do not want that, you can provide a default C<die> handler, or	203	If you do not want that, you can provide a default C<die> handler, or
201	simply avoid dieing (by use of C<eval>).	204	simply avoid dieing (by use of C<eval>).
202		205
203	Example: Create a new coroutine that just prints its arguments.	206	Example: Create a new coro that just prints its arguments.
204		207
205	async {	208	async {
206	print "@_\n";	209	print "@_\n";
207	} 1,2,3,4;	210	} 1,2,3,4;
208		211
209	=cut
210
211	sub async(&@) {
212	my $coro = new Coro @_;
213	$coro->ready;
214	$coro
215	}
216
217	=item async_pool { ... } [@args...]	212	=item async_pool { ... } [@args...]
218		213
219	Similar to C<async>, but uses a coroutine pool, so you should not call	214	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	215	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	216	coro that might have executed other code already (which can be good
222	or bad :).	217	or bad :).
223		218
224	On the plus side, this function is faster than creating (and destroying)	219	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	220	destroying) a completely new coro, so if you need a lot of generic
226	quick successsion, use C<async_pool>, not C<async>.	221	coros in quick successsion, use C<async_pool>, not C<async>.
227		222
228	The code block is executed in an C<eval> context and a warning will be	223	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	224	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>	225	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,	226	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	227	which somehow defeats the purpose of pooling (but is fine in the
233	exceptional case).	228	exceptional case).
234		229
235	The priority will be reset to C<0> after each run, tracing will be	230	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	231	disabled, the description will be reset and the default output filehandle
237	gets restored, so you can change all these. Otherwise the coroutine will	232	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	233	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	234	stuff such as C<$/> you I<must needs> revert that change, which is most
240	simply done by using local as in: C< local $/ >.	235	simply done by using local as in: C<< local $/ >>.
241		236
242	The pool size is limited to C<8> idle coroutines (this can be adjusted by	237	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	238	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
244	required.	239	coros as required.
245		240
246	If you are concerned about pooled coroutines growing a lot because a	241	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	242	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	243	{ 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	244	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.	245	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
251		246
252	=cut	247	=cut
253		248
254	our $POOL_SIZE = 8;	249	our $POOL_SIZE = 8;
255	our $POOL_RSS = 16 * 1024;	250	our $POOL_RSS = 32 * 1024;
256	our @async_pool;	251	our @async_pool;
257		252
258	sub pool_handler {	253	sub pool_handler {
259	my $cb;
260
261	while () {	254	while () {
262	eval {	255	eval {
263	while () {	256	&{&_pool_handler} while 1;
264	_pool_1 $cb;
265	&$cb;
266	_pool_2 $cb;
267	&schedule;
268	}
269	};	257	};
270		258
271	last if $@ eq "\3async_pool terminate\2\n";
272	warn $@ if $@;	259	warn $@ if $@;
273	}	260	}
274	}	261	}
275		262
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	$coro
284	}
285
286	=back	263	=back
287		264
288	=head2 STATIC METHODS	265	=head1 STATIC METHODS
289		266
290	Static methods are actually functions that operate on the current coroutine.	267	Static methods are actually functions that implicitly operate on the
		268	current coro.
291		269
292	=over 4	270	=over 4
293		271
294	=item schedule	272	=item schedule
295		273
296	Calls the scheduler. The scheduler will find the next coroutine that is	274	Calls the scheduler. The scheduler will find the next coro that is
297	to be run from the ready queue and switches to it. The next coroutine	275	to be run from the ready queue and switches to it. The next coro
298	to be run is simply the one with the highest priority that is longest	276	to be run is simply the one with the highest priority that is longest
299	in its ready queue. If there is no coroutine ready, it will clal the	277	in its ready queue. If there is no coro ready, it will clal the
300	C<$Coro::idle> hook.	278	C<$Coro::idle> hook.
301		279
302	Please note that the current coroutine will I<not> be put into the ready	280	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	281	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 >>,	282	again unless something else (e.g. an event handler) calls C<< ->ready >>,
305	thus waking you up.	283	thus waking you up.
306		284
307	This makes C<schedule> I<the> generic method to use to block the current	285	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	286	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	287	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	288	>> 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,	289	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	290	so you need to check whether the event indeed happened, e.g. by storing the
313	status in a variable.	291	status in a variable.
314		292
315	The canonical way to wait on external events is this:	293	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
316		294
317	{	295	=item cede
318	# remember current coroutine
319	my $current = $Coro::current;
320		296
321	# register a hypothetical event handler	297	"Cede" to other coros. This function puts the current coro into
322	on_event_invoke sub {	298	the ready queue and calls C<schedule>, which has the effect of giving
323	# wake up sleeping coroutine	299	up the current "timeslice" to other coros of the same or higher
324	$current->ready;	300	priority. Once your coro gets its turn again it will automatically be
325	undef $current;	301	resumed.
		302
		303	This function is often called C<yield> in other languages.
		304
		305	=item Coro::cede_notself
		306
		307	Works like cede, but is not exported by default and will cede to I<any>
		308	coro, regardless of priority. This is useful sometimes to ensure
		309	progress is made.
		310
		311	=item terminate [arg...]
		312
		313	Terminates the current coro with the given status values (see L<cancel>).
		314
		315	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
		316
		317	These function install enter and leave winders in the current scope. The
		318	enter block will be executed when on_enter is called and whenever the
		319	current coro is re-entered by the scheduler, while the leave block is
		320	executed whenever the current coro is blocked by the scheduler, and
		321	also when the containing scope is exited (by whatever means, be it exit,
		322	die, last etc.).
		323
		324	I<Neither invoking the scheduler, nor exceptions, are allowed within those
		325	BLOCKs>. That means: do not even think about calling C<die> without an
		326	eval, and do not even think of entering the scheduler in any way.
		327
		328	Since both BLOCKs are tied to the current scope, they will automatically
		329	be removed when the current scope exits.
		330
		331	These functions implement the same concept as C<dynamic-wind> in scheme
		332	does, and are useful when you want to localise some resource to a specific
		333	coro.
		334
		335	They slow down thread switching considerably for coros that use them
		336	(about 40% for a BLOCK with a single assignment, so thread switching is
		337	still reasonably fast if the handlers are fast).
		338
		339	These functions are best understood by an example: The following function
		340	will change the current timezone to "Antarctica/South_Pole", which
		341	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
		342	which remember/change the current timezone and restore the previous
		343	value, respectively, the timezone is only changed for the coro that
		344	installed those handlers.
		345
		346	use POSIX qw(tzset);
		347
		348	async {
		349	my $old_tz; # store outside TZ value here
		350
		351	Coro::on_enter {
		352	$old_tz = $ENV{TZ}; # remember the old value
		353
		354	$ENV{TZ} = "Antarctica/South_Pole";
		355	tzset; # enable new value
326	};	356	};
327		357
328	# call schedule until event occurred.	358	Coro::on_leave {
329	# in case we are woken up for other reasons	359	$ENV{TZ} = $old_tz;
330	# (current still defined), loop.	360	tzset; # restore old value
331	Coro::schedule while $current;	361	};
		362
		363	# at this place, the timezone is Antarctica/South_Pole,
		364	# without disturbing the TZ of any other coro.
332	}	365	};
333		366
334	=item cede	367	This can be used to localise about any resource (locale, uid, current
		368	working directory etc.) to a block, despite the existance of other
		369	coros.
335		370
336	"Cede" to other coroutines. This function puts the current coroutine into	371	Another interesting example implements time-sliced multitasking using
337	the ready queue and calls C<schedule>, which has the effect of giving	372	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		373
342	This function is often called C<yield> in other languages.	374	# "timeslice" the given block
		375	sub timeslice(&) {
		376	use Time::HiRes ();
343		377
344	=item Coro::cede_notself	378	Coro::on_enter {
		379	# on entering the thread, we set an VTALRM handler to cede
		380	$SIG{VTALRM} = sub { cede };
		381	# and then start the interval timer
		382	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
		383	};
		384	Coro::on_leave {
		385	# on leaving the thread, we stop the interval timer again
		386	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
		387	};
345		388
346	Works like cede, but is not exported by default and will cede to I<any>	389	&{+shift};
347	coroutine, regardless of priority. This is useful sometimes to ensure	390	}
348	progress is made.
349		391
350	=item terminate [arg...]	392	# use like this:
		393	timeslice {
		394	# The following is an endless loop that would normally
		395	# monopolise the process. Since it runs in a timesliced
		396	# environment, it will regularly cede to other threads.
		397	while () { }
		398	};
351		399
352	Terminates the current coroutine with the given status values (see L<cancel>).
353		400
354	=item killall	401	=item killall
355		402
356	Kills/terminates/cancels all coroutines except the currently running	403	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		404
360	Note that while this will try to free some of the main programs resources,	405	Note that while this will try to free some of the main interpreter
		406	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	407	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.	408	calls this function, there will be some one-time resource leak.
363		409
364	=cut	410	=cut
365
366	sub terminate {
367	$current->cancel (@_);
368	}
369		411
370	sub killall {	412	sub killall {
371	for (Coro::State::list) {	413	for (Coro::State::list) {
372	$_->cancel	414	$_->cancel
373	if $_ != $current && UNIVERSAL::isa $_, "Coro";	415	if $_ != $current && UNIVERSAL::isa $_, "Coro";
374	}	416	}
375	}	417	}
376		418
377	=back	419	=back
378		420
379	=head2 COROUTINE METHODS	421	=head1 CORO OBJECT METHODS
380		422
381	These are the methods you can call on coroutine objects (or to create	423	These are the methods you can call on coro objects (or to create
382	them).	424	them).
383		425
384	=over 4	426	=over 4
385		427
386	=item new Coro \&sub [, @args...]	428	=item new Coro \&sub [, @args...]
387		429
388	Create a new coroutine and return it. When the sub returns, the coroutine	430	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	431	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	432	called. To make the coro run you must first put it into the ready
391	queue by calling the ready method.	433	queue by calling the ready method.
392		434
393	See C<async> and C<Coro::State::new> for additional info about the	435	See C<async> and C<Coro::State::new> for additional info about the
394	coroutine environment.	436	coro environment.
395		437
396	=cut	438	=cut
397		439
398	sub _run_coro {	440	sub _coro_run {
399	terminate &{+shift};	441	terminate &{+shift};
400	}	442	}
401		443
402	sub new {
403	my $class = shift;
404
405	$class->SUPER::new (\&_run_coro, @_)
406	}
407
408	=item $success = $coroutine->ready	444	=item $success = $coro->ready
409		445
410	Put the given coroutine into the end of its ready queue (there is one	446	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	447	queue for each priority) and return true. If the coro is already in
412	the ready queue, do nothing and return false.	448	the ready queue, do nothing and return false.
413		449
414	This ensures that the scheduler will resume this coroutine automatically	450	This ensures that the scheduler will resume this coro automatically
415	once all the coroutines of higher priority and all coroutines of the same	451	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.	452	priority that were put into the ready queue earlier have been resumed.
417		453
		454	=item $coro->suspend
		455
		456	Suspends the specified coro. A suspended coro works just like any other
		457	coro, except that the scheduler will not select a suspended coro for
		458	execution.
		459
		460	Suspending a coro can be useful when you want to keep the coro from
		461	running, but you don't want to destroy it, or when you want to temporarily
		462	freeze a coro (e.g. for debugging) to resume it later.
		463
		464	A scenario for the former would be to suspend all (other) coros after a
		465	fork and keep them alive, so their destructors aren't called, but new
		466	coros can be created.
		467
		468	=item $coro->resume
		469
		470	If the specified coro was suspended, it will be resumed. Note that when
		471	the coro was in the ready queue when it was suspended, it might have been
		472	unreadied by the scheduler, so an activation might have been lost.
		473
		474	To avoid this, it is best to put a suspended coro into the ready queue
		475	unconditionally, as every synchronisation mechanism must protect itself
		476	against spurious wakeups, and the one in the Coro family certainly do
		477	that.
		478
418	=item $is_ready = $coroutine->is_ready	479	=item $is_ready = $coro->is_ready
419		480
420	Return wether the coroutine is currently the ready queue or not,	481	Returns true iff the Coro object is in the ready queue. Unless the Coro
		482	object gets destroyed, it will eventually be scheduled by the scheduler.
421		483
		484	=item $is_running = $coro->is_running
		485
		486	Returns true iff the Coro object is currently running. Only one Coro object
		487	can ever be in the running state (but it currently is possible to have
		488	multiple running Coro::States).
		489
		490	=item $is_suspended = $coro->is_suspended
		491
		492	Returns true iff this Coro object has been suspended. Suspended Coros will
		493	not ever be scheduled.
		494
422	=item $coroutine->cancel (arg...)	495	=item $coro->cancel (arg...)
423		496
424	Terminates the given coroutine and makes it return the given arguments as	497	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	498	status (default: the empty list). Never returns if the Coro is the
426	current coroutine.	499	current Coro.
427		500
428	=cut	501	=cut
429		502
430	sub cancel {	503	sub cancel {
431	my $self = shift;	504	my $self = shift;
432	$self->{_status} = [@_];
433		505
434	if ($current == $self) {	506	if ($current == $self) {
435	push @destroy, $self;	507	terminate @_;
436	$manager->ready;
437	&schedule while 1;
438	} else {	508	} else {
439	$self->_cancel;	509	$self->{_status} = [@_];
		510	Coro::State::cancel $self;
440	}	511	}
441	}	512	}
442		513
		514	=item $coro->schedule_to
		515
		516	Puts the current coro to sleep (like C<Coro::schedule>), but instead
		517	of continuing with the next coro from the ready queue, always switch to
		518	the given coro object (regardless of priority etc.). The readyness
		519	state of that coro isn't changed.
		520
		521	This is an advanced method for special cases - I'd love to hear about any
		522	uses for this one.
		523
		524	=item $coro->cede_to
		525
		526	Like C<schedule_to>, but puts the current coro into the ready
		527	queue. This has the effect of temporarily switching to the given
		528	coro, and continuing some time later.
		529
		530	This is an advanced method for special cases - I'd love to hear about any
		531	uses for this one.
		532
		533	=item $coro->throw ([$scalar])
		534
		535	If C<$throw> is specified and defined, it will be thrown as an exception
		536	inside the coro at the next convenient point in time. Otherwise
		537	clears the exception object.
		538
		539	Coro will check for the exception each time a schedule-like-function
		540	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		541	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		542	detect this case and return early in case an exception is pending.
		543
		544	The exception object will be thrown "as is" with the specified scalar in
		545	C<$@>, i.e. if it is a string, no line number or newline will be appended
		546	(unlike with C<die>).
		547
		548	This can be used as a softer means than C<cancel> to ask a coro to
		549	end itself, although there is no guarantee that the exception will lead to
		550	termination, and if the exception isn't caught it might well end the whole
		551	program.
		552
		553	You might also think of C<throw> as being the moral equivalent of
		554	C<kill>ing a coro with a signal (in this case, a scalar).
		555
443	=item $coroutine->join	556	=item $coro->join
444		557
445	Wait until the coroutine terminates and return any values given to the	558	Wait until the coro terminates and return any values given to the
446	C<terminate> or C<cancel> functions. C<join> can be called concurrently	559	C<terminate> or C<cancel> functions. C<join> can be called concurrently
447	from multiple coroutines, and all will be resumed and given the status	560	from multiple coro, and all will be resumed and given the status
448	return once the C<$coroutine> terminates.	561	return once the C<$coro> terminates.
449		562
450	=cut	563	=cut
451		564
452	sub join {	565	sub join {
453	my $self = shift;	566	my $self = shift;
…		…
464	}	577	}
465		578
466	wantarray ? @{$self->{_status}} : $self->{_status}[0];	579	wantarray ? @{$self->{_status}} : $self->{_status}[0];
467	}	580	}
468		581
469	=item $coroutine->on_destroy (\&cb)	582	=item $coro->on_destroy (\&cb)
470		583
471	Registers a callback that is called when this coroutine gets destroyed,	584	Registers a callback that is called when this coro gets destroyed,
472	but before it is joined. The callback gets passed the terminate arguments,	585	but before it is joined. The callback gets passed the terminate arguments,
473	if any, and I<must not> die, under any circumstances.	586	if any, and I<must not> die, under any circumstances.
474		587
475	=cut	588	=cut
476		589
…		…
478	my ($self, $cb) = @_;	591	my ($self, $cb) = @_;
479		592
480	push @{ $self->{_on_destroy} }, $cb;	593	push @{ $self->{_on_destroy} }, $cb;
481	}	594	}
482		595
483	=item $oldprio = $coroutine->prio ($newprio)	596	=item $oldprio = $coro->prio ($newprio)
484		597
485	Sets (or gets, if the argument is missing) the priority of the	598	Sets (or gets, if the argument is missing) the priority of the
486	coroutine. Higher priority coroutines get run before lower priority	599	coro. Higher priority coro get run before lower priority
487	coroutines. Priorities are small signed integers (currently -4 .. +3),	600	coro. Priorities are small signed integers (currently -4 .. +3),
488	that you can refer to using PRIO_xxx constants (use the import tag :prio	601	that you can refer to using PRIO_xxx constants (use the import tag :prio
489	to get then):	602	to get then):
490		603
491	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	604	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
492	3 > 1 > 0 > -1 > -3 > -4	605	3 > 1 > 0 > -1 > -3 > -4
493		606
494	# set priority to HIGH	607	# set priority to HIGH
495	current->prio(PRIO_HIGH);	608	current->prio (PRIO_HIGH);
496		609
497	The idle coroutine ($Coro::idle) always has a lower priority than any	610	The idle coro ($Coro::idle) always has a lower priority than any
498	existing coroutine.	611	existing coro.
499		612
500	Changing the priority of the current coroutine will take effect immediately,	613	Changing the priority of the current coro will take effect immediately,
501	but changing the priority of coroutines in the ready queue (but not	614	but changing the priority of coro in the ready queue (but not
502	running) will only take effect after the next schedule (of that	615	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.	616	coro). This is a bug that will be fixed in some future version.
504		617
505	=item $newprio = $coroutine->nice ($change)	618	=item $newprio = $coro->nice ($change)
506		619
507	Similar to C<prio>, but subtract the given value from the priority (i.e.	620	Similar to C<prio>, but subtract the given value from the priority (i.e.
508	higher values mean lower priority, just as in unix).	621	higher values mean lower priority, just as in unix).
509		622
510	=item $olddesc = $coroutine->desc ($newdesc)	623	=item $olddesc = $coro->desc ($newdesc)
511		624
512	Sets (or gets in case the argument is missing) the description for this	625	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.	626	coro. This is just a free-form string you can associate with a
		627	coro.
514		628
515	This method simply sets the C<< $coroutine->{desc} >> member to the given string. You	629	This method simply sets the C<< $coro->{desc} >> member to the given
516	can modify this member directly if you wish.	630	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		631
534	=cut	632	=cut
535		633
536	sub desc {	634	sub desc {
537	my $old = $_[0]{desc};	635	my $old = $_[0]{desc};
538	$_[0]{desc} = $_[1] if @_ > 1;	636	$_[0]{desc} = $_[1] if @_ > 1;
539	$old;	637	$old;
540	}	638	}
541		639
		640	sub transfer {
		641	require Carp;
		642	Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
		643	}
		644
542	=back	645	=back
543		646
544	=head2 GLOBAL FUNCTIONS	647	=head1 GLOBAL FUNCTIONS
545		648
546	=over 4	649	=over 4
547		650
548	=item Coro::nready	651	=item Coro::nready
549		652
550	Returns the number of coroutines that are currently in the ready state,	653	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	654	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	655	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>	656	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	657	would cause a deadlock unless there is an idle handler that wakes up some
555	coroutines.	658	coro.
556		659
557	=item my $guard = Coro::guard { ... }	660	=item my $guard = Coro::guard { ... }
558		661
559	This creates and returns a guard object. Nothing happens until the object	662	This function still exists, but is deprecated. Please use the
560	gets destroyed, in which case the codeblock given as argument will be	663	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		664
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	665	=cut
577		666
578	sub guard(&) {	667	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		668
591	=item unblock_sub { ... }	669	=item unblock_sub { ... }
592		670
593	This utility function takes a BLOCK or code reference and "unblocks" it,	671	This utility function takes a BLOCK or code reference and "unblocks" it,
594	returning a new coderef. Unblocking means that calling the new coderef	672	returning a new coderef. Unblocking means that calling the new coderef
595	will return immediately without blocking, returning nothing, while the	673	will return immediately without blocking, returning nothing, while the
596	original code ref will be called (with parameters) from within another	674	original code ref will be called (with parameters) from within another
597	coroutine.	675	coro.
598		676
599	The reason this function exists is that many event libraries (such as the	677	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	678	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,	679	of reentrancy). This means you must not block within event callbacks,
602	otherwise you might suffer from crashes or worse. The only event library	680	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>.	681	currently known that is safe to use without C<unblock_sub> is L<EV>.
604		682
605	This function allows your callbacks to block by executing them in another	683	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	684	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	685	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
608	disk, for example.	686	disk, for example.
609		687
610	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	688	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
611	creating event callbacks that want to block.	689	creating event callbacks that want to block.
612		690
613	If your handler does not plan to block (e.g. simply sends a message to	691	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),	692	another coro, or puts some other coro into the ready queue), there is
615	there is no reason to use C<unblock_sub>.	693	no reason to use C<unblock_sub>.
616		694
617	Note that you also need to use C<unblock_sub> for any other callbacks that	695	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	696	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	697	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	698	provides callbacks that are the result of some event callback, then you
…		…
629	# return immediately and can be reused) and because we cannot cede	707	# return immediately and can be reused) and because we cannot cede
630	# inside an event callback.	708	# inside an event callback.
631	our $unblock_scheduler = new Coro sub {	709	our $unblock_scheduler = new Coro sub {
632	while () {	710	while () {
633	while (my $cb = pop @unblock_queue) {	711	while (my $cb = pop @unblock_queue) {
634	# this is an inlined copy of async_pool	712	&async_pool (@$cb);
635	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
636		713
637	$coro->{_invoke} = $cb;
638	$coro->ready;
639	cede; # for short-lived callbacks, this reduces pressure on the coro pool	714	# for short-lived callbacks, this reduces pressure on the coro pool
		715	# as the chance is very high that the async_poll coro will be back
		716	# in the idle state when cede returns
		717	cede;
640	}	718	}
641	schedule; # sleep well	719	schedule; # sleep well
642	}	720	}
643	};	721	};
644	$unblock_scheduler->desc ("[unblock_sub scheduler]");	722	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
645		723
646	sub unblock_sub(&) {	724	sub unblock_sub(&) {
647	my $cb = shift;	725	my $cb = shift;
648		726
649	sub {	727	sub {
650	unshift @unblock_queue, [$cb, @_];	728	unshift @unblock_queue, [$cb, @_];
651	$unblock_scheduler->ready;	729	$unblock_scheduler->ready;
652	}	730	}
653	}	731	}
654		732
		733	=item $cb = Coro::rouse_cb
		734
		735	Create and return a "rouse callback". That's a code reference that,
		736	when called, will remember a copy of its arguments and notify the owner
		737	coro of the callback.
		738
		739	See the next function.
		740
		741	=item @args = Coro::rouse_wait [$cb]
		742
		743	Wait for the specified rouse callback (or the last one that was created in
		744	this coro).
		745
		746	As soon as the callback is invoked (or when the callback was invoked
		747	before C<rouse_wait>), it will return the arguments originally passed to
		748	the rouse callback. In scalar context, that means you get the I<last>
		749	argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
		750	statement at the end.
		751
		752	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		753
655	=back	754	=back
656		755
657	=cut	756	=cut
658		757
659	1;	758	1;
660		759
		760	=head1 HOW TO WAIT FOR A CALLBACK
		761
		762	It is very common for a coro to wait for some callback to be
		763	called. This occurs naturally when you use coro in an otherwise
		764	event-based program, or when you use event-based libraries.
		765
		766	These typically register a callback for some event, and call that callback
		767	when the event occured. In a coro, however, you typically want to
		768	just wait for the event, simplyifying things.
		769
		770	For example C<< AnyEvent->child >> registers a callback to be called when
		771	a specific child has exited:
		772
		773	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		774
		775	But from within a coro, you often just want to write this:
		776
		777	my $status = wait_for_child $pid;
		778
		779	Coro offers two functions specifically designed to make this easy,
		780	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		781
		782	The first function, C<rouse_cb>, generates and returns a callback that,
		783	when invoked, will save its arguments and notify the coro that
		784	created the callback.
		785
		786	The second function, C<rouse_wait>, waits for the callback to be called
		787	(by calling C<schedule> to go to sleep) and returns the arguments
		788	originally passed to the callback.
		789
		790	Using these functions, it becomes easy to write the C<wait_for_child>
		791	function mentioned above:
		792
		793	sub wait_for_child($) {
		794	my ($pid) = @_;
		795
		796	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		797
		798	my ($rpid, $rstatus) = Coro::rouse_wait;
		799	$rstatus
		800	}
		801
		802	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		803	you can roll your own, using C<schedule>:
		804
		805	sub wait_for_child($) {
		806	my ($pid) = @_;
		807
		808	# store the current coro in $current,
		809	# and provide result variables for the closure passed to ->child
		810	my $current = $Coro::current;
		811	my ($done, $rstatus);
		812
		813	# pass a closure to ->child
		814	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		815	$rstatus = $_[1]; # remember rstatus
		816	$done = 1; # mark $rstatus as valud
		817	});
		818
		819	# wait until the closure has been called
		820	schedule while !$done;
		821
		822	$rstatus
		823	}
		824
		825
661	=head1 BUGS/LIMITATIONS	826	=head1 BUGS/LIMITATIONS
662		827
		828	=over 4
		829
		830	=item fork with pthread backend
		831
		832	When Coro is compiled using the pthread backend (which isn't recommended
		833	but required on many BSDs as their libcs are completely broken), then
		834	coro will not survive a fork. There is no known workaround except to
		835	fix your libc and use a saner backend.
		836
		837	=item perl process emulation ("threads")
		838
663	This module is not perl-pseudo-thread-safe. You should only ever use this	839	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	840	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	841	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	842	this). I recommend disabling thread support and using processes, as having
667	is much faster and uses less memory.	843	the windows process emulation enabled under unix roughly halves perl
		844	performance, even when not used.
		845
		846	=item coro switching is not signal safe
		847
		848	You must not switch to another coro from within a signal handler
		849	(only relevant with %SIG - most event libraries provide safe signals).
		850
		851	That means you I<MUST NOT> call any function that might "block" the
		852	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		853	anything that calls those. Everything else, including calling C<ready>,
		854	works.
		855
		856	=back
		857
		858
		859	=head1 WINDOWS PROCESS EMULATION
		860
		861	A great many people seem to be confused about ithreads (for example, Chip
		862	Salzenberg called me unintelligent, incapable, stupid and gullible,
		863	while in the same mail making rather confused statements about perl
		864	ithreads (for example, that memory or files would be shared), showing his
		865	lack of understanding of this area - if it is hard to understand for Chip,
		866	it is probably not obvious to everybody).
		867
		868	What follows is an ultra-condensed version of my talk about threads in
		869	scripting languages given onthe perl workshop 2009:
		870
		871	The so-called "ithreads" were originally implemented for two reasons:
		872	first, to (badly) emulate unix processes on native win32 perls, and
		873	secondly, to replace the older, real thread model ("5.005-threads").
		874
		875	It does that by using threads instead of OS processes. The difference
		876	between processes and threads is that threads share memory (and other
		877	state, such as files) between threads within a single process, while
		878	processes do not share anything (at least not semantically). That
		879	means that modifications done by one thread are seen by others, while
		880	modifications by one process are not seen by other processes.
		881
		882	The "ithreads" work exactly like that: when creating a new ithreads
		883	process, all state is copied (memory is copied physically, files and code
		884	is copied logically). Afterwards, it isolates all modifications. On UNIX,
		885	the same behaviour can be achieved by using operating system processes,
		886	except that UNIX typically uses hardware built into the system to do this
		887	efficiently, while the windows process emulation emulates this hardware in
		888	software (rather efficiently, but of course it is still much slower than
		889	dedicated hardware).
		890
		891	As mentioned before, loading code, modifying code, modifying data
		892	structures and so on is only visible in the ithreads process doing the
		893	modification, not in other ithread processes within the same OS process.
		894
		895	This is why "ithreads" do not implement threads for perl at all, only
		896	processes. What makes it so bad is that on non-windows platforms, you can
		897	actually take advantage of custom hardware for this purpose (as evidenced
		898	by the forks module, which gives you the (i-) threads API, just much
		899	faster).
		900
		901	Sharing data is in the i-threads model is done by transfering data
		902	structures between threads using copying semantics, which is very slow -
		903	shared data simply does not exist. Benchmarks using i-threads which are
		904	communication-intensive show extremely bad behaviour with i-threads (in
		905	fact, so bad that Coro, which cannot take direct advantage of multiple
		906	CPUs, is often orders of magnitude faster because it shares data using
		907	real threads, refer to my talk for details).
		908
		909	As summary, i-threads use threads to implement processes, while
		910	the compatible forks module uses processes to emulate, uhm,
		911	processes. I-threads slow down every perl program when enabled, and
		912	outside of windows, serve no (or little) practical purpose, but
		913	disadvantages every single-threaded Perl program.
		914
		915	This is the reason that I try to avoid the name "ithreads", as it is
		916	misleading as it implies that it implements some kind of thread model for
		917	perl, and prefer the name "windows process emulation", which describes the
		918	actual use and behaviour of it much better.
668		919
669	=head1 SEE ALSO	920	=head1 SEE ALSO
670		921
671	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.	922	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
672		923
673	Debugging: L<Coro::Debug>.	924	Debugging: L<Coro::Debug>.
674		925
675	Support/Utility: L<Coro::Specific>, L<Coro::Util>.	926	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
676		927
677	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.	928	Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
		929	L<Coro::SemaphoreSet>, L<Coro::RWLock>.
678		930
679	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.	931	I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
680		932
681	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.	933	Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
		934	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
		935	L<Coro::Select>.
682		936
683	XS API: L<Coro::MakeMaker>.	937	XS API: L<Coro::MakeMaker>.
684		938
685	Low level Configuration, Coroutine Environment: L<Coro::State>.	939	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
686		940
687	=head1 AUTHOR	941	=head1 AUTHOR
688		942
689	Marc Lehmann <schmorp@schmorp.de>	943	Marc Lehmann <schmorp@schmorp.de>
690	http://home.schmorp.de/	944	http://home.schmorp.de/

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Comparing Coro/Coro.pm (file contents):
Revision 1.186 by root, Sun May 25 01:32:36 2008 UTC vs.
Revision 1.269 by root, Thu Oct 1 23:25:03 2009 UTC