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

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Revision 1.181 by root, Fri May 9 22:04:37 2008 UTC vs.
Revision 1.271 by root, Fri Oct 2 19:55:59 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, such as multiple HTTP-GET requests	36	in the documentation). They are similar to kernel threads but don't (in
41	running concurrently.	37	general) run in parallel at the same time even on SMP machines. The
		38	specific flavor of thread offered by this module also guarantees you that
		39	it will not switch between threads unless necessary, at easily-identified
		40	points in your program, so locking and parallel access are rarely an
		41	issue, making thread programming much safer and easier than using other
		42	thread models.
42		43
43	Coroutines are also useful because Perl has no support for threads (the so	44	Unlike the so-called "Perl threads" (which are not actually real threads
44	called "threads" that perl offers are nothing more than the (bad) process	45	but only the windows process emulation (see section of same name for more
45	emulation coming from the Windows platform: On standard operating systems	46	details) ported to unix, and as such act as processes), Coro provides
46	they serve no purpose whatsoever, except by making your programs slow and	47	a full shared address space, which makes communication between threads
47	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
48	aks your software vendor/distributor to do it for you).	49	process emulation code in your perl and using Coro can easily result in
		50	a two to four times speed increase for your programs. A parallel matrix
		51	multiplication benchmark runs over 300 times faster on a single core than
		52	perl's pseudo-threads on a quad core using all four cores.
49		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
50	In this module, coroutines are defined as "callchain + lexical variables +	60	In this module, a thread is defined as "callchain + lexical variables +
51	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,	61	some package variables + C stack), that is, a thread has its own callchain,
52	its own set of lexicals and its own set of perls most important global	62	its own set of lexicals and its own set of perls most important global
53	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.
54		67
55	=cut	68	=cut
56		69
57	package Coro;	70	package Coro;
58		71
59	use strict;	72	use common::sense;
60	no warnings "uninitialized";	73
		74	use Carp ();
		75
		76	use Guard ();
61		77
62	use Coro::State;	78	use Coro::State;
63		79
64	use base qw(Coro::State Exporter);	80	use base qw(Coro::State Exporter);
65		81
66	our $idle; # idle handler	82	our $idle; # idle handler
67	our $main; # main coroutine	83	our $main; # main coro
68	our $current; # current coroutine	84	our $current; # current coro
69		85
70	our $VERSION = 4.6;	86	our $VERSION = 5.2;
71		87
72	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	88	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
73	our %EXPORT_TAGS = (	89	our %EXPORT_TAGS = (
74	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	90	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
75	);	91	);
76	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	92	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
77		93
		94	=head1 GLOBAL VARIABLES
		95
78	=over 4	96	=over 4
79		97
80	=item $Coro::main	98	=item $Coro::main
81		99
82	This variable stores the coroutine object that represents the main	100	This variable stores the Coro object that represents the main
83	program. While you cna C<ready> it and do most other things you can do to	101	program. While you cna C<ready> it and do most other things you can do to
84	coroutines, it is mainly useful to compare again C<$Coro::current>, to see	102	coro, it is mainly useful to compare again C<$Coro::current>, to see
85	wether you are running in the main program or not.	103	whether you are running in the main program or not.
86		104
87	=cut	105	=cut
88		106
89	$main = new Coro;	107	# $main is now being initialised by Coro::State
90		108
91	=item $Coro::current	109	=item $Coro::current
92		110
93	The coroutine object representing the current coroutine (the last	111	The Coro object representing the current coro (the last
94	coroutine that the Coro scheduler switched to). The initial value is	112	coro that the Coro scheduler switched to). The initial value is
95	C<$main> (of course).	113	C<$Coro::main> (of course).
96		114
97	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
98	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
99	not otherwise modify the variable itself.	117	not otherwise modify the variable itself.
100		118
101	=cut	119	=cut
102		120
103	$main->{desc} = "[main::]";
104
105	# maybe some other module used Coro::Specific before...
106	$main->{_specific} = $current->{_specific}
107	if $current;
108
109	_set_current $main;
110
111	sub current() { $current } # [DEPRECATED]	121	sub current() { $current } # [DEPRECATED]
112		122
113	=item $Coro::idle	123	=item $Coro::idle
114		124
115	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
116	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
117	pretty low-level functionality.	127	pretty low-level functionality.
118		128
119	This variable stores a callback that is called whenever the scheduler	129	This variable stores a Coro object that is put into the ready queue when
120	finds no ready coroutines to run. The default implementation prints	130	there are no other ready threads (without invoking any ready hooks).
121	"FATAL: deadlock detected" and exits, because the program has no other way
122	to continue.
123		131
		132	The default implementation dies with "FATAL: deadlock detected.", followed
		133	by a thread listing, because the program has no other way to continue.
		134
124	This hook is overwritten by modules such as C<Coro::Timer> and	135	This hook is overwritten by modules such as C<Coro::EV> and
125	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a	136	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
126	coroutine so the scheduler can run it.	137	coro so the scheduler can run it.
127		138
128	Note that the callback I<must not>, under any circumstances, block
129	the current coroutine. Normally, this is achieved by having an "idle
130	coroutine" that calls the event loop and then blocks again, and then
131	readying that coroutine in the idle handler.
132
133	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this	139	See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
134	technique.
135		140
136	Please note that if your callback recursively invokes perl (e.g. for event
137	handlers), then it must be prepared to be called recursively itself.
138
139	=cut	141	=cut
140		142
141	$idle = sub {	143	$idle = new Coro sub {
142	require Carp;	144	require Coro::Debug;
143	Carp::croak ("FATAL: deadlock detected");	145	die "FATAL: deadlock detected.\n"
		146	. Coro::Debug::ps_listing ();
144	};	147	};
145		148
146	sub _cancel {
147	my ($self) = @_;
148
149	# free coroutine data and mark as destructed
150	$self->_destroy
151	or return;
152
153	# call all destruction callbacks
154	$_->(@{$self->{_status}})
155	for @{(delete $self->{_on_destroy}) \|\| []};
156	}
157
158	# this coroutine is necessary because a coroutine	149	# this coro is necessary because a coro
159	# cannot destroy itself.	150	# cannot destroy itself.
160	my @destroy;	151	our @destroy;
161	my $manager;	152	our $manager;
162		153
163	$manager = new Coro sub {	154	$manager = new Coro sub {
164	while () {	155	while () {
165	(shift @destroy)->_cancel	156	Coro::State::cancel shift @destroy
166	while @destroy;	157	while @destroy;
167		158
168	&schedule;	159	&schedule;
169	}	160	}
170	};	161	};
171	$manager->desc ("[coro manager]");	162	$manager->{desc} = "[coro manager]";
172	$manager->prio (PRIO_MAX);	163	$manager->prio (PRIO_MAX);
173		164
174	=back	165	=back
175		166
176	=head2 SIMPLE COROUTINE CREATION	167	=head1 SIMPLE CORO CREATION
177		168
178	=over 4	169	=over 4
179		170
180	=item async { ... } [@args...]	171	=item async { ... } [@args...]
181		172
182	Create a new coroutine and return it's coroutine object (usually	173	Create a new coro and return its Coro object (usually
183	unused). The coroutine will be put into the ready queue, so	174	unused). The coro will be put into the ready queue, so
184	it will start running automatically on the next scheduler run.	175	it will start running automatically on the next scheduler run.
185		176
186	The first argument is a codeblock/closure that should be executed in the	177	The first argument is a codeblock/closure that should be executed in the
187	coroutine. When it returns argument returns the coroutine is automatically	178	coro. When it returns argument returns the coro is automatically
188	terminated.	179	terminated.
189		180
190	The remaining arguments are passed as arguments to the closure.	181	The remaining arguments are passed as arguments to the closure.
191		182
192	See the C<Coro::State::new> constructor for info about the coroutine	183	See the C<Coro::State::new> constructor for info about the coro
193	environment in which coroutines are executed.	184	environment in which coro are executed.
194		185
195	Calling C<exit> in a coroutine will do the same as calling exit outside	186	Calling C<exit> in a coro will do the same as calling exit outside
196	the coroutine. Likewise, when the coroutine dies, the program will exit,	187	the coro. Likewise, when the coro dies, the program will exit,
197	just as it would in the main program.	188	just as it would in the main program.
198		189
199	If you do not want that, you can provide a default C<die> handler, or	190	If you do not want that, you can provide a default C<die> handler, or
200	simply avoid dieing (by use of C<eval>).	191	simply avoid dieing (by use of C<eval>).
201		192
202	Example: Create a new coroutine that just prints its arguments.	193	Example: Create a new coro that just prints its arguments.
203		194
204	async {	195	async {
205	print "@_\n";	196	print "@_\n";
206	} 1,2,3,4;	197	} 1,2,3,4;
207		198
208	=cut
209
210	sub async(&@) {
211	my $coro = new Coro @_;
212	$coro->ready;
213	$coro
214	}
215
216	=item async_pool { ... } [@args...]	199	=item async_pool { ... } [@args...]
217		200
218	Similar to C<async>, but uses a coroutine pool, so you should not call	201	Similar to C<async>, but uses a coro pool, so you should not call
219	terminate or join on it (although you are allowed to), and you get a	202	terminate or join on it (although you are allowed to), and you get a
220	coroutine that might have executed other code already (which can be good	203	coro that might have executed other code already (which can be good
221	or bad :).	204	or bad :).
222		205
223	On the plus side, this function is faster than creating (and destroying)	206	On the plus side, this function is about twice as fast as creating (and
224	a completely new coroutine, so if you need a lot of generic coroutines in	207	destroying) a completely new coro, so if you need a lot of generic
225	quick successsion, use C<async_pool>, not C<async>.	208	coros in quick successsion, use C<async_pool>, not C<async>.
226		209
227	The code block is executed in an C<eval> context and a warning will be	210	The code block is executed in an C<eval> context and a warning will be
228	issued in case of an exception instead of terminating the program, as	211	issued in case of an exception instead of terminating the program, as
229	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>	212	C<async> does. As the coro is being reused, stuff like C<on_destroy>
230	will not work in the expected way, unless you call terminate or cancel,	213	will not work in the expected way, unless you call terminate or cancel,
231	which somehow defeats the purpose of pooling (but is fine in the	214	which somehow defeats the purpose of pooling (but is fine in the
232	exceptional case).	215	exceptional case).
233		216
234	The priority will be reset to C<0> after each run, tracing will be	217	The priority will be reset to C<0> after each run, tracing will be
235	disabled, the description will be reset and the default output filehandle	218	disabled, the description will be reset and the default output filehandle
236	gets restored, so you can change all these. Otherwise the coroutine will	219	gets restored, so you can change all these. Otherwise the coro will
237	be re-used "as-is": most notably if you change other per-coroutine global	220	be re-used "as-is": most notably if you change other per-coro global
238	stuff such as C<$/> you I<must needs> to revert that change, which is most	221	stuff such as C<$/> you I<must needs> revert that change, which is most
239	simply done by using local as in: C< local $/ >.	222	simply done by using local as in: C<< local $/ >>.
240		223
241	The pool size is limited to C<8> idle coroutines (this can be adjusted by	224	The idle pool size is limited to C<8> idle coros (this can be
242	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as	225	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
243	required.	226	coros as required.
244		227
245	If you are concerned about pooled coroutines growing a lot because a	228	If you are concerned about pooled coros growing a lot because a
246	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool	229	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
247	{ terminate }> once per second or so to slowly replenish the pool. In	230	{ terminate }> once per second or so to slowly replenish the pool. In
248	addition to that, when the stacks used by a handler grows larger than 16kb	231	addition to that, when the stacks used by a handler grows larger than 32kb
249	(adjustable via $Coro::POOL_RSS) it will also be destroyed.	232	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
250		233
251	=cut	234	=cut
252		235
253	our $POOL_SIZE = 8;	236	our $POOL_SIZE = 8;
254	our $POOL_RSS = 16 * 1024;	237	our $POOL_RSS = 32 * 1024;
255	our @async_pool;	238	our @async_pool;
256		239
257	sub pool_handler {	240	sub pool_handler {
258	my $cb;
259
260	while () {	241	while () {
261	eval {	242	eval {
262	while () {	243	&{&_pool_handler} while 1;
263	_pool_1 $cb;
264	&$cb;
265	_pool_2 $cb;
266	&schedule;
267	}
268	};	244	};
269		245
270	last if $@ eq "\3async_pool terminate\2\n";
271	warn $@ if $@;	246	warn $@ if $@;
272	}	247	}
273	}	248	}
274		249
275	sub async_pool(&@) {
276	# this is also inlined into the unlock_scheduler
277	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
278
279	$coro->{_invoke} = [@_];
280	$coro->ready;
281
282	$coro
283	}
284
285	=back	250	=back
286		251
287	=head2 STATIC METHODS	252	=head1 STATIC METHODS
288		253
289	Static methods are actually functions that operate on the current coroutine.	254	Static methods are actually functions that implicitly operate on the
		255	current coro.
290		256
291	=over 4	257	=over 4
292		258
293	=item schedule	259	=item schedule
294		260
295	Calls the scheduler. The scheduler will find the next coroutine that is	261	Calls the scheduler. The scheduler will find the next coro that is
296	to be run from the ready queue and switches to it. The next coroutine	262	to be run from the ready queue and switches to it. The next coro
297	to be run is simply the one with the highest priority that is longest	263	to be run is simply the one with the highest priority that is longest
298	in its ready queue. If there is no coroutine ready, it will clal the	264	in its ready queue. If there is no coro ready, it will call the
299	C<$Coro::idle> hook.	265	C<$Coro::idle> hook.
300		266
301	Please note that the current coroutine will I<not> be put into the ready	267	Please note that the current coro will I<not> be put into the ready
302	queue, so calling this function usually means you will never be called	268	queue, so calling this function usually means you will never be called
303	again unless something else (e.g. an event handler) calls C<< ->ready >>,	269	again unless something else (e.g. an event handler) calls C<< ->ready >>,
304	thus waking you up.	270	thus waking you up.
305		271
306	This makes C<schedule> I<the> generic method to use to block the current	272	This makes C<schedule> I<the> generic method to use to block the current
307	coroutine and wait for events: first you remember the current coroutine in	273	coro and wait for events: first you remember the current coro in
308	a variable, then arrange for some callback of yours to call C<< ->ready	274	a variable, then arrange for some callback of yours to call C<< ->ready
309	>> on that once some event happens, and last you call C<schedule> to put	275	>> on that once some event happens, and last you call C<schedule> to put
310	yourself to sleep. Note that a lot of things can wake your coroutine up,	276	yourself to sleep. Note that a lot of things can wake your coro up,
311	so you need to check wether the event indeed happened, e.g. by storing the	277	so you need to check whether the event indeed happened, e.g. by storing the
312	status in a variable.	278	status in a variable.
313		279
314	The canonical way to wait on external events is this:	280	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
315		281
316	{	282	=item cede
317	# remember current coroutine
318	my $current = $Coro::current;
319		283
320	# register a hypothetical event handler	284	"Cede" to other coros. This function puts the current coro into
321	on_event_invoke sub {	285	the ready queue and calls C<schedule>, which has the effect of giving
322	# wake up sleeping coroutine	286	up the current "timeslice" to other coros of the same or higher
323	$current->ready;	287	priority. Once your coro gets its turn again it will automatically be
324	undef $current;	288	resumed.
		289
		290	This function is often called C<yield> in other languages.
		291
		292	=item Coro::cede_notself
		293
		294	Works like cede, but is not exported by default and will cede to I<any>
		295	coro, regardless of priority. This is useful sometimes to ensure
		296	progress is made.
		297
		298	=item terminate [arg...]
		299
		300	Terminates the current coro with the given status values (see L<cancel>).
		301
		302	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
		303
		304	These function install enter and leave winders in the current scope. The
		305	enter block will be executed when on_enter is called and whenever the
		306	current coro is re-entered by the scheduler, while the leave block is
		307	executed whenever the current coro is blocked by the scheduler, and
		308	also when the containing scope is exited (by whatever means, be it exit,
		309	die, last etc.).
		310
		311	I<Neither invoking the scheduler, nor exceptions, are allowed within those
		312	BLOCKs>. That means: do not even think about calling C<die> without an
		313	eval, and do not even think of entering the scheduler in any way.
		314
		315	Since both BLOCKs are tied to the current scope, they will automatically
		316	be removed when the current scope exits.
		317
		318	These functions implement the same concept as C<dynamic-wind> in scheme
		319	does, and are useful when you want to localise some resource to a specific
		320	coro.
		321
		322	They slow down thread switching considerably for coros that use them
		323	(about 40% for a BLOCK with a single assignment, so thread switching is
		324	still reasonably fast if the handlers are fast).
		325
		326	These functions are best understood by an example: The following function
		327	will change the current timezone to "Antarctica/South_Pole", which
		328	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
		329	which remember/change the current timezone and restore the previous
		330	value, respectively, the timezone is only changed for the coro that
		331	installed those handlers.
		332
		333	use POSIX qw(tzset);
		334
		335	async {
		336	my $old_tz; # store outside TZ value here
		337
		338	Coro::on_enter {
		339	$old_tz = $ENV{TZ}; # remember the old value
		340
		341	$ENV{TZ} = "Antarctica/South_Pole";
		342	tzset; # enable new value
325	};	343	};
326		344
327	# call schedule until event occurred.	345	Coro::on_leave {
328	# in case we are woken up for other reasons	346	$ENV{TZ} = $old_tz;
329	# (current still defined), loop.	347	tzset; # restore old value
330	Coro::schedule while $current;	348	};
		349
		350	# at this place, the timezone is Antarctica/South_Pole,
		351	# without disturbing the TZ of any other coro.
331	}	352	};
332		353
333	=item cede	354	This can be used to localise about any resource (locale, uid, current
		355	working directory etc.) to a block, despite the existance of other
		356	coros.
334		357
335	"Cede" to other coroutines. This function puts the current coroutine into	358	Another interesting example implements time-sliced multitasking using
336	the ready queue and calls C<schedule>, which has the effect of giving	359	interval timers (this could obviously be optimised, but does the job):
337	up the current "timeslice" to other coroutines of the same or higher
338	priority. Once your coroutine gets its turn again it will automatically be
339	resumed.
340		360
341	This function is often called C<yield> in other languages.	361	# "timeslice" the given block
		362	sub timeslice(&) {
		363	use Time::HiRes ();
342		364
343	=item Coro::cede_notself	365	Coro::on_enter {
		366	# on entering the thread, we set an VTALRM handler to cede
		367	$SIG{VTALRM} = sub { cede };
		368	# and then start the interval timer
		369	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
		370	};
		371	Coro::on_leave {
		372	# on leaving the thread, we stop the interval timer again
		373	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
		374	};
344		375
345	Works like cede, but is not exported by default and will cede to I<any>	376	&{+shift};
346	coroutine, regardless of priority. This is useful sometimes to ensure	377	}
347	progress is made.
348		378
349	=item terminate [arg...]	379	# use like this:
		380	timeslice {
		381	# The following is an endless loop that would normally
		382	# monopolise the process. Since it runs in a timesliced
		383	# environment, it will regularly cede to other threads.
		384	while () { }
		385	};
350		386
351	Terminates the current coroutine with the given status values (see L<cancel>).
352		387
353	=item killall	388	=item killall
354		389
355	Kills/terminates/cancels all coroutines except the currently running	390	Kills/terminates/cancels all coros except the currently running one.
356	one. This is useful after a fork, either in the child or the parent, as
357	usually only one of them should inherit the running coroutines.
358		391
359	Note that while this will try to free some of the main programs resources,	392	Note that while this will try to free some of the main interpreter
		393	resources if the calling coro isn't the main coro, but one
360	you cnanot free all of them, so if a coroutine that is not the main	394	cannot free all of them, so if a coro that is not the main coro
361	program calls this function, there will be some one-time resource leak.	395	calls this function, there will be some one-time resource leak.
362		396
363	=cut	397	=cut
364
365	sub terminate {
366	$current->cancel (@_);
367	}
368		398
369	sub killall {	399	sub killall {
370	for (Coro::State::list) {	400	for (Coro::State::list) {
371	$_->cancel	401	$_->cancel
372	if $_ != $current && UNIVERSAL::isa $_, "Coro";	402	if $_ != $current && UNIVERSAL::isa $_, "Coro";
373	}	403	}
374	}	404	}
375		405
376	=back	406	=back
377		407
378	=head2 COROUTINE METHODS	408	=head1 CORO OBJECT METHODS
379		409
380	These are the methods you can call on coroutine objects (or to create	410	These are the methods you can call on coro objects (or to create
381	them).	411	them).
382		412
383	=over 4	413	=over 4
384		414
385	=item new Coro \&sub [, @args...]	415	=item new Coro \&sub [, @args...]
386		416
387	Create a new coroutine and return it. When the sub returns, the coroutine	417	Create a new coro and return it. When the sub returns, the coro
388	automatically terminates as if C<terminate> with the returned values were	418	automatically terminates as if C<terminate> with the returned values were
389	called. To make the coroutine run you must first put it into the ready	419	called. To make the coro run you must first put it into the ready
390	queue by calling the ready method.	420	queue by calling the ready method.
391		421
392	See C<async> and C<Coro::State::new> for additional info about the	422	See C<async> and C<Coro::State::new> for additional info about the
393	coroutine environment.	423	coro environment.
394		424
395	=cut	425	=cut
396		426
397	sub _run_coro {	427	sub _coro_run {
398	terminate &{+shift};	428	terminate &{+shift};
399	}	429	}
400		430
401	sub new {
402	my $class = shift;
403
404	$class->SUPER::new (\&_run_coro, @_)
405	}
406
407	=item $success = $coroutine->ready	431	=item $success = $coro->ready
408		432
409	Put the given coroutine into the end of its ready queue (there is one	433	Put the given coro into the end of its ready queue (there is one
410	queue for each priority) and return true. If the coroutine is already in	434	queue for each priority) and return true. If the coro is already in
411	the ready queue, do nothing and return false.	435	the ready queue, do nothing and return false.
412		436
413	This ensures that the scheduler will resume this coroutine automatically	437	This ensures that the scheduler will resume this coro automatically
414	once all the coroutines of higher priority and all coroutines of the same	438	once all the coro of higher priority and all coro of the same
415	priority that were put into the ready queue earlier have been resumed.	439	priority that were put into the ready queue earlier have been resumed.
416		440
		441	=item $coro->suspend
		442
		443	Suspends the specified coro. A suspended coro works just like any other
		444	coro, except that the scheduler will not select a suspended coro for
		445	execution.
		446
		447	Suspending a coro can be useful when you want to keep the coro from
		448	running, but you don't want to destroy it, or when you want to temporarily
		449	freeze a coro (e.g. for debugging) to resume it later.
		450
		451	A scenario for the former would be to suspend all (other) coros after a
		452	fork and keep them alive, so their destructors aren't called, but new
		453	coros can be created.
		454
		455	=item $coro->resume
		456
		457	If the specified coro was suspended, it will be resumed. Note that when
		458	the coro was in the ready queue when it was suspended, it might have been
		459	unreadied by the scheduler, so an activation might have been lost.
		460
		461	To avoid this, it is best to put a suspended coro into the ready queue
		462	unconditionally, as every synchronisation mechanism must protect itself
		463	against spurious wakeups, and the one in the Coro family certainly do
		464	that.
		465
417	=item $is_ready = $coroutine->is_ready	466	=item $is_ready = $coro->is_ready
418		467
419	Return wether the coroutine is currently the ready queue or not,	468	Returns true iff the Coro object is in the ready queue. Unless the Coro
		469	object gets destroyed, it will eventually be scheduled by the scheduler.
420		470
		471	=item $is_running = $coro->is_running
		472
		473	Returns true iff the Coro object is currently running. Only one Coro object
		474	can ever be in the running state (but it currently is possible to have
		475	multiple running Coro::States).
		476
		477	=item $is_suspended = $coro->is_suspended
		478
		479	Returns true iff this Coro object has been suspended. Suspended Coros will
		480	not ever be scheduled.
		481
421	=item $coroutine->cancel (arg...)	482	=item $coro->cancel (arg...)
422		483
423	Terminates the given coroutine and makes it return the given arguments as	484	Terminates the given Coro and makes it return the given arguments as
424	status (default: the empty list). Never returns if the coroutine is the	485	status (default: the empty list). Never returns if the Coro is the
425	current coroutine.	486	current Coro.
426		487
427	=cut	488	=cut
428		489
429	sub cancel {	490	sub cancel {
430	my $self = shift;	491	my $self = shift;
431	$self->{_status} = [@_];
432		492
433	if ($current == $self) {	493	if ($current == $self) {
434	push @destroy, $self;	494	terminate @_;
435	$manager->ready;
436	&schedule while 1;
437	} else {	495	} else {
438	$self->_cancel;	496	$self->{_status} = [@_];
		497	Coro::State::cancel $self;
439	}	498	}
440	}	499	}
441		500
		501	=item $coro->schedule_to
		502
		503	Puts the current coro to sleep (like C<Coro::schedule>), but instead
		504	of continuing with the next coro from the ready queue, always switch to
		505	the given coro object (regardless of priority etc.). The readyness
		506	state of that coro isn't changed.
		507
		508	This is an advanced method for special cases - I'd love to hear about any
		509	uses for this one.
		510
		511	=item $coro->cede_to
		512
		513	Like C<schedule_to>, but puts the current coro into the ready
		514	queue. This has the effect of temporarily switching to the given
		515	coro, and continuing some time later.
		516
		517	This is an advanced method for special cases - I'd love to hear about any
		518	uses for this one.
		519
		520	=item $coro->throw ([$scalar])
		521
		522	If C<$throw> is specified and defined, it will be thrown as an exception
		523	inside the coro at the next convenient point in time. Otherwise
		524	clears the exception object.
		525
		526	Coro will check for the exception each time a schedule-like-function
		527	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		528	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		529	detect this case and return early in case an exception is pending.
		530
		531	The exception object will be thrown "as is" with the specified scalar in
		532	C<$@>, i.e. if it is a string, no line number or newline will be appended
		533	(unlike with C<die>).
		534
		535	This can be used as a softer means than C<cancel> to ask a coro to
		536	end itself, although there is no guarantee that the exception will lead to
		537	termination, and if the exception isn't caught it might well end the whole
		538	program.
		539
		540	You might also think of C<throw> as being the moral equivalent of
		541	C<kill>ing a coro with a signal (in this case, a scalar).
		542
442	=item $coroutine->join	543	=item $coro->join
443		544
444	Wait until the coroutine terminates and return any values given to the	545	Wait until the coro terminates and return any values given to the
445	C<terminate> or C<cancel> functions. C<join> can be called concurrently	546	C<terminate> or C<cancel> functions. C<join> can be called concurrently
446	from multiple coroutines, and all will be resumed and given the status	547	from multiple coro, and all will be resumed and given the status
447	return once the C<$coroutine> terminates.	548	return once the C<$coro> terminates.
448		549
449	=cut	550	=cut
450		551
451	sub join {	552	sub join {
452	my $self = shift;	553	my $self = shift;
…		…
463	}	564	}
464		565
465	wantarray ? @{$self->{_status}} : $self->{_status}[0];	566	wantarray ? @{$self->{_status}} : $self->{_status}[0];
466	}	567	}
467		568
468	=item $coroutine->on_destroy (\&cb)	569	=item $coro->on_destroy (\&cb)
469		570
470	Registers a callback that is called when this coroutine gets destroyed,	571	Registers a callback that is called when this coro gets destroyed,
471	but before it is joined. The callback gets passed the terminate arguments,	572	but before it is joined. The callback gets passed the terminate arguments,
472	if any, and I<must not> die, under any circumstances.	573	if any, and I<must not> die, under any circumstances.
473		574
474	=cut	575	=cut
475		576
…		…
477	my ($self, $cb) = @_;	578	my ($self, $cb) = @_;
478		579
479	push @{ $self->{_on_destroy} }, $cb;	580	push @{ $self->{_on_destroy} }, $cb;
480	}	581	}
481		582
482	=item $oldprio = $coroutine->prio ($newprio)	583	=item $oldprio = $coro->prio ($newprio)
483		584
484	Sets (or gets, if the argument is missing) the priority of the	585	Sets (or gets, if the argument is missing) the priority of the
485	coroutine. Higher priority coroutines get run before lower priority	586	coro. Higher priority coro get run before lower priority
486	coroutines. Priorities are small signed integers (currently -4 .. +3),	587	coro. Priorities are small signed integers (currently -4 .. +3),
487	that you can refer to using PRIO_xxx constants (use the import tag :prio	588	that you can refer to using PRIO_xxx constants (use the import tag :prio
488	to get then):	589	to get then):
489		590
490	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	591	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
491	3 > 1 > 0 > -1 > -3 > -4	592	3 > 1 > 0 > -1 > -3 > -4
492		593
493	# set priority to HIGH	594	# set priority to HIGH
494	current->prio(PRIO_HIGH);	595	current->prio (PRIO_HIGH);
495		596
496	The idle coroutine ($Coro::idle) always has a lower priority than any	597	The idle coro ($Coro::idle) always has a lower priority than any
497	existing coroutine.	598	existing coro.
498		599
499	Changing the priority of the current coroutine will take effect immediately,	600	Changing the priority of the current coro will take effect immediately,
500	but changing the priority of coroutines in the ready queue (but not	601	but changing the priority of coro in the ready queue (but not
501	running) will only take effect after the next schedule (of that	602	running) will only take effect after the next schedule (of that
502	coroutine). This is a bug that will be fixed in some future version.	603	coro). This is a bug that will be fixed in some future version.
503		604
504	=item $newprio = $coroutine->nice ($change)	605	=item $newprio = $coro->nice ($change)
505		606
506	Similar to C<prio>, but subtract the given value from the priority (i.e.	607	Similar to C<prio>, but subtract the given value from the priority (i.e.
507	higher values mean lower priority, just as in unix).	608	higher values mean lower priority, just as in unix).
508		609
509	=item $olddesc = $coroutine->desc ($newdesc)	610	=item $olddesc = $coro->desc ($newdesc)
510		611
511	Sets (or gets in case the argument is missing) the description for this	612	Sets (or gets in case the argument is missing) the description for this
512	coroutine. This is just a free-form string you can associate with a coroutine.	613	coro. This is just a free-form string you can associate with a
		614	coro.
513		615
514	This method simply sets the C<< $coroutine->{desc} >> member to the given string. You	616	This method simply sets the C<< $coro->{desc} >> member to the given
515	can modify this member directly if you wish.	617	string. You can modify this member directly if you wish.
516
517	=item $coroutine->throw ([$scalar])
518
519	If C<$throw> is specified and defined, it will be thrown as an exception
520	inside the coroutine at the next convinient point in time (usually after
521	it gains control at the next schedule/transfer/cede). Otherwise clears the
522	exception object.
523
524	The exception object will be thrown "as is" with the specified scalar in
525	C<$@>, i.e. if it is a string, no line number or newline will be appended
526	(unlike with C<die>).
527
528	This can be used as a softer means than C<cancel> to ask a coroutine to
529	end itself, although there is no guarentee that the exception will lead to
530	termination, and if the exception isn't caught it might well end the whole
531	program.
532		618
533	=cut	619	=cut
534		620
535	sub desc {	621	sub desc {
536	my $old = $_[0]{desc};	622	my $old = $_[0]{desc};
537	$_[0]{desc} = $_[1] if @_ > 1;	623	$_[0]{desc} = $_[1] if @_ > 1;
538	$old;	624	$old;
539	}	625	}
540		626
		627	sub transfer {
		628	require Carp;
		629	Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
		630	}
		631
541	=back	632	=back
542		633
543	=head2 GLOBAL FUNCTIONS	634	=head1 GLOBAL FUNCTIONS
544		635
545	=over 4	636	=over 4
546		637
547	=item Coro::nready	638	=item Coro::nready
548		639
549	Returns the number of coroutines that are currently in the ready state,	640	Returns the number of coro that are currently in the ready state,
550	i.e. that can be switched to by calling C<schedule> directory or	641	i.e. that can be switched to by calling C<schedule> directory or
551	indirectly. The value C<0> means that the only runnable coroutine is the	642	indirectly. The value C<0> means that the only runnable coro is the
552	currently running one, so C<cede> would have no effect, and C<schedule>	643	currently running one, so C<cede> would have no effect, and C<schedule>
553	would cause a deadlock unless there is an idle handler that wakes up some	644	would cause a deadlock unless there is an idle handler that wakes up some
554	coroutines.	645	coro.
555		646
556	=item my $guard = Coro::guard { ... }	647	=item my $guard = Coro::guard { ... }
557		648
558	This creates and returns a guard object. Nothing happens until the object	649	This function still exists, but is deprecated. Please use the
559	gets destroyed, in which case the codeblock given as argument will be	650	C<Guard::guard> function instead.
560	executed. This is useful to free locks or other resources in case of a
561	runtime error or when the coroutine gets canceled, as in both cases the
562	guard block will be executed. The guard object supports only one method,
563	C<< ->cancel >>, which will keep the codeblock from being executed.
564		651
565	Example: set some flag and clear it again when the coroutine gets canceled
566	or the function returns:
567
568	sub do_something {
569	my $guard = Coro::guard { $busy = 0 };
570	$busy = 1;
571
572	# do something that requires $busy to be true
573	}
574
575	=cut	652	=cut
576		653
577	sub guard(&) {	654	BEGIN { *guard = \&Guard::guard }
578	bless \(my $cb = $_[0]), "Coro::guard"
579	}
580
581	sub Coro::guard::cancel {
582	${$_[0]} = sub { };
583	}
584
585	sub Coro::guard::DESTROY {
586	${$_[0]}->();
587	}
588
589		655
590	=item unblock_sub { ... }	656	=item unblock_sub { ... }
591		657
592	This utility function takes a BLOCK or code reference and "unblocks" it,	658	This utility function takes a BLOCK or code reference and "unblocks" it,
593	returning a new coderef. Unblocking means that calling the new coderef	659	returning a new coderef. Unblocking means that calling the new coderef
594	will return immediately without blocking, returning nothing, while the	660	will return immediately without blocking, returning nothing, while the
595	original code ref will be called (with parameters) from within another	661	original code ref will be called (with parameters) from within another
596	coroutine.	662	coro.
597		663
598	The reason this function exists is that many event libraries (such as the	664	The reason this function exists is that many event libraries (such as the
599	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form	665	venerable L<Event\|Event> module) are not thread-safe (a weaker form
600	of thread-safety). This means you must not block within event callbacks,	666	of reentrancy). This means you must not block within event callbacks,
601	otherwise you might suffer from crashes or worse. The only event library	667	otherwise you might suffer from crashes or worse. The only event library
602	currently known that is safe to use without C<unblock_sub> is L<EV>.	668	currently known that is safe to use without C<unblock_sub> is L<EV>.
603		669
604	This function allows your callbacks to block by executing them in another	670	This function allows your callbacks to block by executing them in another
605	coroutine where it is safe to block. One example where blocking is handy	671	coro where it is safe to block. One example where blocking is handy
606	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	672	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
607	disk, for example.	673	disk, for example.
608		674
609	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	675	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
610	creating event callbacks that want to block.	676	creating event callbacks that want to block.
611		677
612	If your handler does not plan to block (e.g. simply sends a message to	678	If your handler does not plan to block (e.g. simply sends a message to
613	another coroutine, or puts some other coroutine into the ready queue),	679	another coro, or puts some other coro into the ready queue), there is
614	there is no reason to use C<unblock_sub>.	680	no reason to use C<unblock_sub>.
		681
		682	Note that you also need to use C<unblock_sub> for any other callbacks that
		683	are indirectly executed by any C-based event loop. For example, when you
		684	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		685	provides callbacks that are the result of some event callback, then you
		686	must not block either, or use C<unblock_sub>.
615		687
616	=cut	688	=cut
617		689
618	our @unblock_queue;	690	our @unblock_queue;
619		691
…		…
622	# return immediately and can be reused) and because we cannot cede	694	# return immediately and can be reused) and because we cannot cede
623	# inside an event callback.	695	# inside an event callback.
624	our $unblock_scheduler = new Coro sub {	696	our $unblock_scheduler = new Coro sub {
625	while () {	697	while () {
626	while (my $cb = pop @unblock_queue) {	698	while (my $cb = pop @unblock_queue) {
627	# this is an inlined copy of async_pool	699	&async_pool (@$cb);
628	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
629		700
630	$coro->{_invoke} = $cb;
631	$coro->ready;
632	cede; # for short-lived callbacks, this reduces pressure on the coro pool	701	# for short-lived callbacks, this reduces pressure on the coro pool
		702	# as the chance is very high that the async_poll coro will be back
		703	# in the idle state when cede returns
		704	cede;
633	}	705	}
634	schedule; # sleep well	706	schedule; # sleep well
635	}	707	}
636	};	708	};
637	$unblock_scheduler->desc ("[unblock_sub scheduler]");	709	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
638		710
639	sub unblock_sub(&) {	711	sub unblock_sub(&) {
640	my $cb = shift;	712	my $cb = shift;
641		713
642	sub {	714	sub {
643	unshift @unblock_queue, [$cb, @_];	715	unshift @unblock_queue, [$cb, @_];
644	$unblock_scheduler->ready;	716	$unblock_scheduler->ready;
645	}	717	}
646	}	718	}
647		719
		720	=item $cb = rouse_cb
		721
		722	Create and return a "rouse callback". That's a code reference that,
		723	when called, will remember a copy of its arguments and notify the owner
		724	coro of the callback.
		725
		726	See the next function.
		727
		728	=item @args = rouse_wait [$cb]
		729
		730	Wait for the specified rouse callback (or the last one that was created in
		731	this coro).
		732
		733	As soon as the callback is invoked (or when the callback was invoked
		734	before C<rouse_wait>), it will return the arguments originally passed to
		735	the rouse callback. In scalar context, that means you get the I<last>
		736	argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
		737	statement at the end.
		738
		739	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		740
648	=back	741	=back
649		742
650	=cut	743	=cut
651		744
652	1;	745	1;
653		746
		747	=head1 HOW TO WAIT FOR A CALLBACK
		748
		749	It is very common for a coro to wait for some callback to be
		750	called. This occurs naturally when you use coro in an otherwise
		751	event-based program, or when you use event-based libraries.
		752
		753	These typically register a callback for some event, and call that callback
		754	when the event occured. In a coro, however, you typically want to
		755	just wait for the event, simplyifying things.
		756
		757	For example C<< AnyEvent->child >> registers a callback to be called when
		758	a specific child has exited:
		759
		760	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		761
		762	But from within a coro, you often just want to write this:
		763
		764	my $status = wait_for_child $pid;
		765
		766	Coro offers two functions specifically designed to make this easy,
		767	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		768
		769	The first function, C<rouse_cb>, generates and returns a callback that,
		770	when invoked, will save its arguments and notify the coro that
		771	created the callback.
		772
		773	The second function, C<rouse_wait>, waits for the callback to be called
		774	(by calling C<schedule> to go to sleep) and returns the arguments
		775	originally passed to the callback.
		776
		777	Using these functions, it becomes easy to write the C<wait_for_child>
		778	function mentioned above:
		779
		780	sub wait_for_child($) {
		781	my ($pid) = @_;
		782
		783	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		784
		785	my ($rpid, $rstatus) = Coro::rouse_wait;
		786	$rstatus
		787	}
		788
		789	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		790	you can roll your own, using C<schedule>:
		791
		792	sub wait_for_child($) {
		793	my ($pid) = @_;
		794
		795	# store the current coro in $current,
		796	# and provide result variables for the closure passed to ->child
		797	my $current = $Coro::current;
		798	my ($done, $rstatus);
		799
		800	# pass a closure to ->child
		801	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		802	$rstatus = $_[1]; # remember rstatus
		803	$done = 1; # mark $rstatus as valud
		804	});
		805
		806	# wait until the closure has been called
		807	schedule while !$done;
		808
		809	$rstatus
		810	}
		811
		812
654	=head1 BUGS/LIMITATIONS	813	=head1 BUGS/LIMITATIONS
655		814
		815	=over 4
		816
		817	=item fork with pthread backend
		818
		819	When Coro is compiled using the pthread backend (which isn't recommended
		820	but required on many BSDs as their libcs are completely broken), then
		821	coro will not survive a fork. There is no known workaround except to
		822	fix your libc and use a saner backend.
		823
		824	=item perl process emulation ("threads")
		825
656	This module is not perl-pseudo-thread-safe. You should only ever use this	826	This module is not perl-pseudo-thread-safe. You should only ever use this
657	module from the same thread (this requirement might be removed in the	827	module from the first thread (this requirement might be removed in the
658	future to allow per-thread schedulers, but Coro::State does not yet allow	828	future to allow per-thread schedulers, but Coro::State does not yet allow
659	this). I recommend disabling thread support and using processes, as this	829	this). I recommend disabling thread support and using processes, as having
660	is much faster and uses less memory.	830	the windows process emulation enabled under unix roughly halves perl
		831	performance, even when not used.
		832
		833	=item coro switching is not signal safe
		834
		835	You must not switch to another coro from within a signal handler
		836	(only relevant with %SIG - most event libraries provide safe signals).
		837
		838	That means you I<MUST NOT> call any function that might "block" the
		839	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		840	anything that calls those. Everything else, including calling C<ready>,
		841	works.
		842
		843	=back
		844
		845
		846	=head1 WINDOWS PROCESS EMULATION
		847
		848	A great many people seem to be confused about ithreads (for example, Chip
		849	Salzenberg called me unintelligent, incapable, stupid and gullible,
		850	while in the same mail making rather confused statements about perl
		851	ithreads (for example, that memory or files would be shared), showing his
		852	lack of understanding of this area - if it is hard to understand for Chip,
		853	it is probably not obvious to everybody).
		854
		855	What follows is an ultra-condensed version of my talk about threads in
		856	scripting languages given onthe perl workshop 2009:
		857
		858	The so-called "ithreads" were originally implemented for two reasons:
		859	first, to (badly) emulate unix processes on native win32 perls, and
		860	secondly, to replace the older, real thread model ("5.005-threads").
		861
		862	It does that by using threads instead of OS processes. The difference
		863	between processes and threads is that threads share memory (and other
		864	state, such as files) between threads within a single process, while
		865	processes do not share anything (at least not semantically). That
		866	means that modifications done by one thread are seen by others, while
		867	modifications by one process are not seen by other processes.
		868
		869	The "ithreads" work exactly like that: when creating a new ithreads
		870	process, all state is copied (memory is copied physically, files and code
		871	is copied logically). Afterwards, it isolates all modifications. On UNIX,
		872	the same behaviour can be achieved by using operating system processes,
		873	except that UNIX typically uses hardware built into the system to do this
		874	efficiently, while the windows process emulation emulates this hardware in
		875	software (rather efficiently, but of course it is still much slower than
		876	dedicated hardware).
		877
		878	As mentioned before, loading code, modifying code, modifying data
		879	structures and so on is only visible in the ithreads process doing the
		880	modification, not in other ithread processes within the same OS process.
		881
		882	This is why "ithreads" do not implement threads for perl at all, only
		883	processes. What makes it so bad is that on non-windows platforms, you can
		884	actually take advantage of custom hardware for this purpose (as evidenced
		885	by the forks module, which gives you the (i-) threads API, just much
		886	faster).
		887
		888	Sharing data is in the i-threads model is done by transfering data
		889	structures between threads using copying semantics, which is very slow -
		890	shared data simply does not exist. Benchmarks using i-threads which are
		891	communication-intensive show extremely bad behaviour with i-threads (in
		892	fact, so bad that Coro, which cannot take direct advantage of multiple
		893	CPUs, is often orders of magnitude faster because it shares data using
		894	real threads, refer to my talk for details).
		895
		896	As summary, i-threads use threads to implement processes, while
		897	the compatible forks module uses processes to emulate, uhm,
		898	processes. I-threads slow down every perl program when enabled, and
		899	outside of windows, serve no (or little) practical purpose, but
		900	disadvantages every single-threaded Perl program.
		901
		902	This is the reason that I try to avoid the name "ithreads", as it is
		903	misleading as it implies that it implements some kind of thread model for
		904	perl, and prefer the name "windows process emulation", which describes the
		905	actual use and behaviour of it much better.
661		906
662	=head1 SEE ALSO	907	=head1 SEE ALSO
663		908
664	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.	909	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
665		910
666	Debugging: L<Coro::Debug>.	911	Debugging: L<Coro::Debug>.
667		912
668	Support/Utility: L<Coro::Specific>, L<Coro::Util>.	913	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
669		914
670	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.	915	Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
		916	L<Coro::SemaphoreSet>, L<Coro::RWLock>.
671		917
672	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.	918	I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
673		919
674	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.	920	Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
		921	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
		922	L<Coro::Select>.
675		923
676	XS API: L<Coro::MakeMaker>.	924	XS API: L<Coro::MakeMaker>.
677		925
678	Low level Configuration, Coroutine Environment: L<Coro::State>.	926	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
679		927
680	=head1 AUTHOR	928	=head1 AUTHOR
681		929
682	Marc Lehmann <schmorp@schmorp.de>	930	Marc Lehmann <schmorp@schmorp.de>
683	http://home.schmorp.de/	931	http://home.schmorp.de/

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Revision 1.271 by root, Fri Oct 2 19:55:59 2009 UTC