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

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Revision 1.237 by root, Sat Nov 22 16:37:11 2008 UTC vs.
Revision 1.283 by root, Sat Feb 5 21:20:47 2011 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	Coro - real threads in perl	3	Coro - the only real threads in perl
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use Coro;	7	use Coro;
8		8
11	print "2\n";	11	print "2\n";
12	cede; # yield back to main	12	cede; # yield back to main
13	print "4\n";	13	print "4\n";
14	};	14	};
15	print "1\n";	15	print "1\n";
16	cede; # yield to coroutine	16	cede; # yield to coro
17	print "3\n";	17	print "3\n";
18	cede; # and again	18	cede; # and again
19		19
20	# use locking	20	# use locking
21	use Coro::Semaphore;	21	use Coro::Semaphore;
…		…
29	=head1 DESCRIPTION	29	=head1 DESCRIPTION
30		30
31	For a tutorial-style introduction, please read the L<Coro::Intro>	31	For a tutorial-style introduction, please read the L<Coro::Intro>
32	manpage. This manpage mainly contains reference information.	32	manpage. This manpage mainly contains reference information.
33		33
34	This module collection manages coroutines, that is, cooperative	34	This module collection manages continuations in general, most often in
35	threads. Coroutines are similar to kernel threads but don't (in general)	35	the form of cooperative threads (also called coros, or simply "coro"
		36	in the documentation). They are similar to kernel threads but don't (in
36	run in parallel at the same time even on SMP machines. The specific flavor	37	general) run in parallel at the same time even on SMP machines. The
37	of coroutine used in this module also guarantees you that it will not	38	specific flavor of thread offered by this module also guarantees you that
38	switch between coroutines unless necessary, at easily-identified points	39	it will not switch between threads unless necessary, at easily-identified
39	in your program, so locking and parallel access are rarely an issue,	40	points in your program, so locking and parallel access are rarely an
40	making coroutine programming much safer and easier than using other thread	41	issue, making thread programming much safer and easier than using other
41	models.	42	thread models.
42		43
43	Unlike the so-called "Perl threads" (which are not actually real threads	44	Unlike the so-called "Perl threads" (which are not actually real threads
44	but only the windows process emulation ported to unix), Coro provides a	45	but only the windows process emulation (see section of same name for more
		46	details) ported to unix, and as such act as processes), Coro provides
45	full shared address space, which makes communication between coroutines	47	a full shared address space, which makes communication between threads
46	very easy. And coroutines are fast, too: disabling the Windows process	48	very easy. And Coro's threads are fast, too: disabling the Windows
47	emulation code in your perl and using Coro can easily result in a two to	49	process emulation code in your perl and using Coro can easily result in
48	four times speed increase for your programs.	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
50	Coro achieves that by supporting multiple running interpreters that share	54	Coro achieves that by supporting multiple running interpreters that share
51	data, which is especially useful to code pseudo-parallel processes and	55	data, which is especially useful to code pseudo-parallel processes and
52	for event-based programming, such as multiple HTTP-GET requests running	56	for event-based programming, such as multiple HTTP-GET requests running
53	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro	57	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
54	into an event-based environment.	58	into an event-based environment.
55		59
56	In this module, a coroutines is defined as "callchain + lexical variables	60	In this module, a thread is defined as "callchain + lexical variables +
57	+ @_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own	61	some package variables + C stack), that is, a thread has its own callchain,
58	callchain, its own set of lexicals and its own set of perls most important	62	its own set of lexicals and its own set of perls most important global
59	global variables (see L<Coro::State> for more configuration and background	63	variables (see L<Coro::State> for more configuration and background info).
60	info).
61		64
62	See also the C<SEE ALSO> section at the end of this document - the Coro	65	See also the C<SEE ALSO> section at the end of this document - the Coro
63	module family is quite large.	66	module family is quite large.
64		67
65	=cut	68	=cut
66		69
67	package Coro;	70	package Coro;
68		71
69	use strict qw(vars subs);	72	use common::sense;
70	no warnings "uninitialized";	73
		74	use Carp ();
		75
		76	use Guard ();
71		77
72	use Coro::State;	78	use Coro::State;
73		79
74	use base qw(Coro::State Exporter);	80	use base qw(Coro::State Exporter);
75		81
76	our $idle; # idle handler	82	our $idle; # idle handler
77	our $main; # main coroutine	83	our $main; # main coro
78	our $current; # current coroutine	84	our $current; # current coro
79		85
80	our $VERSION = "5.0";	86	our $VERSION = 5.25;
81		87
82	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	88	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
83	our %EXPORT_TAGS = (	89	our %EXPORT_TAGS = (
84	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	90	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
85	);	91	);
86	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	92	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
87		93
…		…
89		95
90	=over 4	96	=over 4
91		97
92	=item $Coro::main	98	=item $Coro::main
93		99
94	This variable stores the coroutine object that represents the main	100	This variable stores the Coro object that represents the main
95	program. While you cna C<ready> it and do most other things you can do to	101	program. While you cna C<ready> it and do most other things you can do to
96	coroutines, it is mainly useful to compare again C<$Coro::current>, to see	102	coro, it is mainly useful to compare again C<$Coro::current>, to see
97	whether you are running in the main program or not.	103	whether you are running in the main program or not.
98		104
99	=cut	105	=cut
100		106
101	# $main is now being initialised by Coro::State	107	# $main is now being initialised by Coro::State
102		108
103	=item $Coro::current	109	=item $Coro::current
104		110
105	The coroutine object representing the current coroutine (the last	111	The Coro object representing the current coro (the last
106	coroutine that the Coro scheduler switched to). The initial value is	112	coro that the Coro scheduler switched to). The initial value is
107	C<$Coro::main> (of course).	113	C<$Coro::main> (of course).
108		114
109	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
110	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
111	not otherwise modify the variable itself.	117	not otherwise modify the variable itself.
112		118
113	=cut	119	=cut
114		120
115	sub current() { $current } # [DEPRECATED]	121	sub current() { $current } # [DEPRECATED]
116		122
117	=item $Coro::idle	123	=item $Coro::idle
118		124
119	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
120	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
121	pretty low-level functionality.	127	pretty low-level functionality.
122		128
123	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
124	finds no ready coroutines to run. The default implementation prints	130	there are no other ready threads (without invoking any ready hooks).
125	"FATAL: deadlock detected" and exits, because the program has no other way
126	to continue.
127		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
128	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
129	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
130	coroutine so the scheduler can run it.	137	coro so the scheduler can run it.
131		138
132	Note that the callback I<must not>, under any circumstances, block
133	the current coroutine. Normally, this is achieved by having an "idle
134	coroutine" that calls the event loop and then blocks again, and then
135	readying that coroutine in the idle handler.
136
137	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.
138	technique.
139		140
140	Please note that if your callback recursively invokes perl (e.g. for event
141	handlers), then it must be prepared to be called recursively itself.
142
143	=cut	141	=cut
144		142
145	$idle = sub {	143	# \|\|= because other modules could have provided their own by now
146	require Carp;	144	$idle \|\|= new Coro sub {
147	Carp::croak ("FATAL: deadlock detected");	145	require Coro::Debug;
		146	die "FATAL: deadlock detected.\n"
		147	. Coro::Debug::ps_listing ();
148	};	148	};
149		149
150	# this coroutine is necessary because a coroutine	150	# this coro is necessary because a coro
151	# cannot destroy itself.	151	# cannot destroy itself.
152	our @destroy;	152	our @destroy;
153	our $manager;	153	our $manager;
154		154
155	$manager = new Coro sub {	155	$manager = new Coro sub {
156	while () {	156	while () {
157	Coro::_cancel shift @destroy	157	Coro::State::cancel shift @destroy
158	while @destroy;	158	while @destroy;
159		159
160	&schedule;	160	&schedule;
161	}	161	}
162	};	162	};
163	$manager->{desc} = "[coro manager]";	163	$manager->{desc} = "[coro manager]";
164	$manager->prio (PRIO_MAX);	164	$manager->prio (PRIO_MAX);
165		165
166	=back	166	=back
167		167
168	=head1 SIMPLE COROUTINE CREATION	168	=head1 SIMPLE CORO CREATION
169		169
170	=over 4	170	=over 4
171		171
172	=item async { ... } [@args...]	172	=item async { ... } [@args...]
173		173
174	Create a new coroutine and return it's coroutine object (usually	174	Create a new coro and return its Coro object (usually
175	unused). The coroutine will be put into the ready queue, so	175	unused). The coro will be put into the ready queue, so
176	it will start running automatically on the next scheduler run.	176	it will start running automatically on the next scheduler run.
177		177
178	The first argument is a codeblock/closure that should be executed in the	178	The first argument is a codeblock/closure that should be executed in the
179	coroutine. When it returns argument returns the coroutine is automatically	179	coro. When it returns argument returns the coro is automatically
180	terminated.	180	terminated.
181		181
182	The remaining arguments are passed as arguments to the closure.	182	The remaining arguments are passed as arguments to the closure.
183		183
184	See the C<Coro::State::new> constructor for info about the coroutine	184	See the C<Coro::State::new> constructor for info about the coro
185	environment in which coroutines are executed.	185	environment in which coro are executed.
186		186
187	Calling C<exit> in a coroutine will do the same as calling exit outside	187	Calling C<exit> in a coro will do the same as calling exit outside
188	the coroutine. Likewise, when the coroutine dies, the program will exit,	188	the coro. Likewise, when the coro dies, the program will exit,
189	just as it would in the main program.	189	just as it would in the main program.
190		190
191	If you do not want that, you can provide a default C<die> handler, or	191	If you do not want that, you can provide a default C<die> handler, or
192	simply avoid dieing (by use of C<eval>).	192	simply avoid dieing (by use of C<eval>).
193		193
194	Example: Create a new coroutine that just prints its arguments.	194	Example: Create a new coro that just prints its arguments.
195		195
196	async {	196	async {
197	print "@_\n";	197	print "@_\n";
198	} 1,2,3,4;	198	} 1,2,3,4;
199		199
200	=cut
201
202	sub async(&@) {
203	my $coro = new Coro @_;
204	$coro->ready;
205	$coro
206	}
207
208	=item async_pool { ... } [@args...]	200	=item async_pool { ... } [@args...]
209		201
210	Similar to C<async>, but uses a coroutine pool, so you should not call	202	Similar to C<async>, but uses a coro pool, so you should not call
211	terminate or join on it (although you are allowed to), and you get a	203	terminate or join on it (although you are allowed to), and you get a
212	coroutine that might have executed other code already (which can be good	204	coro that might have executed other code already (which can be good
213	or bad :).	205	or bad :).
214		206
215	On the plus side, this function is about twice as fast as creating (and	207	On the plus side, this function is about twice as fast as creating (and
216	destroying) a completely new coroutine, so if you need a lot of generic	208	destroying) a completely new coro, so if you need a lot of generic
217	coroutines in quick successsion, use C<async_pool>, not C<async>.	209	coros in quick successsion, use C<async_pool>, not C<async>.
218		210
219	The code block is executed in an C<eval> context and a warning will be	211	The code block is executed in an C<eval> context and a warning will be
220	issued in case of an exception instead of terminating the program, as	212	issued in case of an exception instead of terminating the program, as
221	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>	213	C<async> does. As the coro is being reused, stuff like C<on_destroy>
222	will not work in the expected way, unless you call terminate or cancel,	214	will not work in the expected way, unless you call terminate or cancel,
223	which somehow defeats the purpose of pooling (but is fine in the	215	which somehow defeats the purpose of pooling (but is fine in the
224	exceptional case).	216	exceptional case).
225		217
226	The priority will be reset to C<0> after each run, tracing will be	218	The priority will be reset to C<0> after each run, tracing will be
227	disabled, the description will be reset and the default output filehandle	219	disabled, the description will be reset and the default output filehandle
228	gets restored, so you can change all these. Otherwise the coroutine will	220	gets restored, so you can change all these. Otherwise the coro will
229	be re-used "as-is": most notably if you change other per-coroutine global	221	be re-used "as-is": most notably if you change other per-coro global
230	stuff such as C<$/> you I<must needs> revert that change, which is most	222	stuff such as C<$/> you I<must needs> revert that change, which is most
231	simply done by using local as in: C<< local $/ >>.	223	simply done by using local as in: C<< local $/ >>.
232		224
233	The idle pool size is limited to C<8> idle coroutines (this can be	225	The idle pool size is limited to C<8> idle coros (this can be
234	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle	226	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
235	coros as required.	227	coros as required.
236		228
237	If you are concerned about pooled coroutines growing a lot because a	229	If you are concerned about pooled coros growing a lot because a
238	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool	230	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
239	{ terminate }> once per second or so to slowly replenish the pool. In	231	{ terminate }> once per second or so to slowly replenish the pool. In
240	addition to that, when the stacks used by a handler grows larger than 32kb	232	addition to that, when the stacks used by a handler grows larger than 32kb
241	(adjustable via $Coro::POOL_RSS) it will also be destroyed.	233	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
242		234
…		…
259	=back	251	=back
260		252
261	=head1 STATIC METHODS	253	=head1 STATIC METHODS
262		254
263	Static methods are actually functions that implicitly operate on the	255	Static methods are actually functions that implicitly operate on the
264	current coroutine.	256	current coro.
265		257
266	=over 4	258	=over 4
267		259
268	=item schedule	260	=item schedule
269		261
270	Calls the scheduler. The scheduler will find the next coroutine that is	262	Calls the scheduler. The scheduler will find the next coro that is
271	to be run from the ready queue and switches to it. The next coroutine	263	to be run from the ready queue and switches to it. The next coro
272	to be run is simply the one with the highest priority that is longest	264	to be run is simply the one with the highest priority that is longest
273	in its ready queue. If there is no coroutine ready, it will clal the	265	in its ready queue. If there is no coro ready, it will call the
274	C<$Coro::idle> hook.	266	C<$Coro::idle> hook.
275		267
276	Please note that the current coroutine will I<not> be put into the ready	268	Please note that the current coro will I<not> be put into the ready
277	queue, so calling this function usually means you will never be called	269	queue, so calling this function usually means you will never be called
278	again unless something else (e.g. an event handler) calls C<< ->ready >>,	270	again unless something else (e.g. an event handler) calls C<< ->ready >>,
279	thus waking you up.	271	thus waking you up.
280		272
281	This makes C<schedule> I<the> generic method to use to block the current	273	This makes C<schedule> I<the> generic method to use to block the current
282	coroutine and wait for events: first you remember the current coroutine in	274	coro and wait for events: first you remember the current coro in
283	a variable, then arrange for some callback of yours to call C<< ->ready	275	a variable, then arrange for some callback of yours to call C<< ->ready
284	>> on that once some event happens, and last you call C<schedule> to put	276	>> on that once some event happens, and last you call C<schedule> to put
285	yourself to sleep. Note that a lot of things can wake your coroutine up,	277	yourself to sleep. Note that a lot of things can wake your coro up,
286	so you need to check whether the event indeed happened, e.g. by storing the	278	so you need to check whether the event indeed happened, e.g. by storing the
287	status in a variable.	279	status in a variable.
288		280
289	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.	281	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
290		282
291	=item cede	283	=item cede
292		284
293	"Cede" to other coroutines. This function puts the current coroutine into	285	"Cede" to other coros. This function puts the current coro into
294	the ready queue and calls C<schedule>, which has the effect of giving	286	the ready queue and calls C<schedule>, which has the effect of giving
295	up the current "timeslice" to other coroutines of the same or higher	287	up the current "timeslice" to other coros of the same or higher
296	priority. Once your coroutine gets its turn again it will automatically be	288	priority. Once your coro gets its turn again it will automatically be
297	resumed.	289	resumed.
298		290
299	This function is often called C<yield> in other languages.	291	This function is often called C<yield> in other languages.
300		292
301	=item Coro::cede_notself	293	=item Coro::cede_notself
302		294
303	Works like cede, but is not exported by default and will cede to I<any>	295	Works like cede, but is not exported by default and will cede to I<any>
304	coroutine, regardless of priority. This is useful sometimes to ensure	296	coro, regardless of priority. This is useful sometimes to ensure
305	progress is made.	297	progress is made.
306		298
307	=item terminate [arg...]	299	=item terminate [arg...]
308		300
309	Terminates the current coroutine with the given status values (see L<cancel>).	301	Terminates the current coro with the given status values (see L<cancel>).
		302
		303	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
		304
		305	These function install enter and leave winders in the current scope. The
		306	enter block will be executed when on_enter is called and whenever the
		307	current coro is re-entered by the scheduler, while the leave block is
		308	executed whenever the current coro is blocked by the scheduler, and
		309	also when the containing scope is exited (by whatever means, be it exit,
		310	die, last etc.).
		311
		312	I<Neither invoking the scheduler, nor exceptions, are allowed within those
		313	BLOCKs>. That means: do not even think about calling C<die> without an
		314	eval, and do not even think of entering the scheduler in any way.
		315
		316	Since both BLOCKs are tied to the current scope, they will automatically
		317	be removed when the current scope exits.
		318
		319	These functions implement the same concept as C<dynamic-wind> in scheme
		320	does, and are useful when you want to localise some resource to a specific
		321	coro.
		322
		323	They slow down thread switching considerably for coros that use them
		324	(about 40% for a BLOCK with a single assignment, so thread switching is
		325	still reasonably fast if the handlers are fast).
		326
		327	These functions are best understood by an example: The following function
		328	will change the current timezone to "Antarctica/South_Pole", which
		329	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
		330	which remember/change the current timezone and restore the previous
		331	value, respectively, the timezone is only changed for the coro that
		332	installed those handlers.
		333
		334	use POSIX qw(tzset);
		335
		336	async {
		337	my $old_tz; # store outside TZ value here
		338
		339	Coro::on_enter {
		340	$old_tz = $ENV{TZ}; # remember the old value
		341
		342	$ENV{TZ} = "Antarctica/South_Pole";
		343	tzset; # enable new value
		344	};
		345
		346	Coro::on_leave {
		347	$ENV{TZ} = $old_tz;
		348	tzset; # restore old value
		349	};
		350
		351	# at this place, the timezone is Antarctica/South_Pole,
		352	# without disturbing the TZ of any other coro.
		353	};
		354
		355	This can be used to localise about any resource (locale, uid, current
		356	working directory etc.) to a block, despite the existance of other
		357	coros.
		358
		359	Another interesting example implements time-sliced multitasking using
		360	interval timers (this could obviously be optimised, but does the job):
		361
		362	# "timeslice" the given block
		363	sub timeslice(&) {
		364	use Time::HiRes ();
		365
		366	Coro::on_enter {
		367	# on entering the thread, we set an VTALRM handler to cede
		368	$SIG{VTALRM} = sub { cede };
		369	# and then start the interval timer
		370	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
		371	};
		372	Coro::on_leave {
		373	# on leaving the thread, we stop the interval timer again
		374	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
		375	};
		376
		377	&{+shift};
		378	}
		379
		380	# use like this:
		381	timeslice {
		382	# The following is an endless loop that would normally
		383	# monopolise the process. Since it runs in a timesliced
		384	# environment, it will regularly cede to other threads.
		385	while () { }
		386	};
		387
310		388
311	=item killall	389	=item killall
312		390
313	Kills/terminates/cancels all coroutines except the currently running	391	Kills/terminates/cancels all coros except the currently running one.
314	one. This is useful after a fork, either in the child or the parent, as
315	usually only one of them should inherit the running coroutines.
316		392
317	Note that while this will try to free some of the main programs resources,	393	Note that while this will try to free some of the main interpreter
		394	resources if the calling coro isn't the main coro, but one
318	you cannot free all of them, so if a coroutine that is not the main	395	cannot free all of them, so if a coro that is not the main coro
319	program calls this function, there will be some one-time resource leak.	396	calls this function, there will be some one-time resource leak.
320		397
321	=cut	398	=cut
322		399
323	sub killall {	400	sub killall {
324	for (Coro::State::list) {	401	for (Coro::State::list) {
…		…
327	}	404	}
328	}	405	}
329		406
330	=back	407	=back
331		408
332	=head1 COROUTINE OBJECT METHODS	409	=head1 CORO OBJECT METHODS
333		410
334	These are the methods you can call on coroutine objects (or to create	411	These are the methods you can call on coro objects (or to create
335	them).	412	them).
336		413
337	=over 4	414	=over 4
338		415
339	=item new Coro \&sub [, @args...]	416	=item new Coro \&sub [, @args...]
340		417
341	Create a new coroutine and return it. When the sub returns, the coroutine	418	Create a new coro and return it. When the sub returns, the coro
342	automatically terminates as if C<terminate> with the returned values were	419	automatically terminates as if C<terminate> with the returned values were
343	called. To make the coroutine run you must first put it into the ready	420	called. To make the coro run you must first put it into the ready
344	queue by calling the ready method.	421	queue by calling the ready method.
345		422
346	See C<async> and C<Coro::State::new> for additional info about the	423	See C<async> and C<Coro::State::new> for additional info about the
347	coroutine environment.	424	coro environment.
348		425
349	=cut	426	=cut
350		427
351	sub _terminate {	428	sub _coro_run {
352	terminate &{+shift};	429	terminate &{+shift};
353	}	430	}
354		431
355	=item $success = $coroutine->ready	432	=item $success = $coro->ready
356		433
357	Put the given coroutine into the end of its ready queue (there is one	434	Put the given coro into the end of its ready queue (there is one
358	queue for each priority) and return true. If the coroutine is already in	435	queue for each priority) and return true. If the coro is already in
359	the ready queue, do nothing and return false.	436	the ready queue, do nothing and return false.
360		437
361	This ensures that the scheduler will resume this coroutine automatically	438	This ensures that the scheduler will resume this coro automatically
362	once all the coroutines of higher priority and all coroutines of the same	439	once all the coro of higher priority and all coro of the same
363	priority that were put into the ready queue earlier have been resumed.	440	priority that were put into the ready queue earlier have been resumed.
364		441
		442	=item $coro->suspend
		443
		444	Suspends the specified coro. A suspended coro works just like any other
		445	coro, except that the scheduler will not select a suspended coro for
		446	execution.
		447
		448	Suspending a coro can be useful when you want to keep the coro from
		449	running, but you don't want to destroy it, or when you want to temporarily
		450	freeze a coro (e.g. for debugging) to resume it later.
		451
		452	A scenario for the former would be to suspend all (other) coros after a
		453	fork and keep them alive, so their destructors aren't called, but new
		454	coros can be created.
		455
		456	=item $coro->resume
		457
		458	If the specified coro was suspended, it will be resumed. Note that when
		459	the coro was in the ready queue when it was suspended, it might have been
		460	unreadied by the scheduler, so an activation might have been lost.
		461
		462	To avoid this, it is best to put a suspended coro into the ready queue
		463	unconditionally, as every synchronisation mechanism must protect itself
		464	against spurious wakeups, and the one in the Coro family certainly do
		465	that.
		466
365	=item $is_ready = $coroutine->is_ready	467	=item $is_ready = $coro->is_ready
366		468
367	Return whether the coroutine is currently the ready queue or not,	469	Returns true iff the Coro object is in the ready queue. Unless the Coro
		470	object gets destroyed, it will eventually be scheduled by the scheduler.
368		471
		472	=item $is_running = $coro->is_running
		473
		474	Returns true iff the Coro object is currently running. Only one Coro object
		475	can ever be in the running state (but it currently is possible to have
		476	multiple running Coro::States).
		477
		478	=item $is_suspended = $coro->is_suspended
		479
		480	Returns true iff this Coro object has been suspended. Suspended Coros will
		481	not ever be scheduled.
		482
369	=item $coroutine->cancel (arg...)	483	=item $coro->cancel (arg...)
370		484
371	Terminates the given coroutine and makes it return the given arguments as	485	Terminates the given Coro and makes it return the given arguments as
372	status (default: the empty list). Never returns if the coroutine is the	486	status (default: the empty list). Never returns if the Coro is the
373	current coroutine.	487	current Coro.
374		488
375	=cut	489	=cut
376		490
377	sub cancel {	491	sub cancel {
378	my $self = shift;	492	my $self = shift;
379		493
380	if ($current == $self) {	494	if ($current == $self) {
381	terminate @_;	495	terminate @_;
382	} else {	496	} else {
383	$self->{_status} = [@_];	497	$self->{_status} = [@_];
384	$self->_cancel;	498	Coro::State::cancel $self;
385	}	499	}
386	}	500	}
387		501
388	=item $coroutine->schedule_to	502	=item $coro->schedule_to
389		503
390	Puts the current coroutine to sleep (like C<Coro::schedule>), but instead	504	Puts the current coro to sleep (like C<Coro::schedule>), but instead
391	of continuing with the next coro from the ready queue, always switch to	505	of continuing with the next coro from the ready queue, always switch to
392	the given coroutine object (regardless of priority etc.). The readyness	506	the given coro object (regardless of priority etc.). The readyness
393	state of that coroutine isn't changed.	507	state of that coro isn't changed.
394		508
395	This is an advanced method for special cases - I'd love to hear about any	509	This is an advanced method for special cases - I'd love to hear about any
396	uses for this one.	510	uses for this one.
397		511
398	=item $coroutine->cede_to	512	=item $coro->cede_to
399		513
400	Like C<schedule_to>, but puts the current coroutine into the ready	514	Like C<schedule_to>, but puts the current coro into the ready
401	queue. This has the effect of temporarily switching to the given	515	queue. This has the effect of temporarily switching to the given
402	coroutine, and continuing some time later.	516	coro, and continuing some time later.
403		517
404	This is an advanced method for special cases - I'd love to hear about any	518	This is an advanced method for special cases - I'd love to hear about any
405	uses for this one.	519	uses for this one.
406		520
407	=item $coroutine->throw ([$scalar])	521	=item $coro->throw ([$scalar])
408		522
409	If C<$throw> is specified and defined, it will be thrown as an exception	523	If C<$throw> is specified and defined, it will be thrown as an exception
410	inside the coroutine at the next convenient point in time. Otherwise	524	inside the coro at the next convenient point in time. Otherwise
411	clears the exception object.	525	clears the exception object.
412		526
413	Coro will check for the exception each time a schedule-like-function	527	Coro will check for the exception each time a schedule-like-function
414	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down	528	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
415	>>, C<< Coro::Handle->readable >> and so on. Most of these functions	529	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
…		…
417		531
418	The exception object will be thrown "as is" with the specified scalar in	532	The exception object will be thrown "as is" with the specified scalar in
419	C<$@>, i.e. if it is a string, no line number or newline will be appended	533	C<$@>, i.e. if it is a string, no line number or newline will be appended
420	(unlike with C<die>).	534	(unlike with C<die>).
421		535
422	This can be used as a softer means than C<cancel> to ask a coroutine to	536	This can be used as a softer means than C<cancel> to ask a coro to
423	end itself, although there is no guarantee that the exception will lead to	537	end itself, although there is no guarantee that the exception will lead to
424	termination, and if the exception isn't caught it might well end the whole	538	termination, and if the exception isn't caught it might well end the whole
425	program.	539	program.
426		540
427	You might also think of C<throw> as being the moral equivalent of	541	You might also think of C<throw> as being the moral equivalent of
428	C<kill>ing a coroutine with a signal (in this case, a scalar).	542	C<kill>ing a coro with a signal (in this case, a scalar).
429		543
430	=item $coroutine->join	544	=item $coro->join
431		545
432	Wait until the coroutine terminates and return any values given to the	546	Wait until the coro terminates and return any values given to the
433	C<terminate> or C<cancel> functions. C<join> can be called concurrently	547	C<terminate> or C<cancel> functions. C<join> can be called concurrently
434	from multiple coroutines, and all will be resumed and given the status	548	from multiple coro, and all will be resumed and given the status
435	return once the C<$coroutine> terminates.	549	return once the C<$coro> terminates.
436		550
437	=cut	551	=cut
438		552
439	sub join {	553	sub join {
440	my $self = shift;	554	my $self = shift;
…		…
451	}	565	}
452		566
453	wantarray ? @{$self->{_status}} : $self->{_status}[0];	567	wantarray ? @{$self->{_status}} : $self->{_status}[0];
454	}	568	}
455		569
456	=item $coroutine->on_destroy (\&cb)	570	=item $coro->on_destroy (\&cb)
457		571
458	Registers a callback that is called when this coroutine gets destroyed,	572	Registers a callback that is called when this coro gets destroyed,
459	but before it is joined. The callback gets passed the terminate arguments,	573	but before it is joined. The callback gets passed the terminate arguments,
460	if any, and I<must not> die, under any circumstances.	574	if any, and I<must not> die, under any circumstances.
461		575
462	=cut	576	=cut
463		577
…		…
465	my ($self, $cb) = @_;	579	my ($self, $cb) = @_;
466		580
467	push @{ $self->{_on_destroy} }, $cb;	581	push @{ $self->{_on_destroy} }, $cb;
468	}	582	}
469		583
470	=item $oldprio = $coroutine->prio ($newprio)	584	=item $oldprio = $coro->prio ($newprio)
471		585
472	Sets (or gets, if the argument is missing) the priority of the	586	Sets (or gets, if the argument is missing) the priority of the
473	coroutine. Higher priority coroutines get run before lower priority	587	coro. Higher priority coro get run before lower priority
474	coroutines. Priorities are small signed integers (currently -4 .. +3),	588	coro. Priorities are small signed integers (currently -4 .. +3),
475	that you can refer to using PRIO_xxx constants (use the import tag :prio	589	that you can refer to using PRIO_xxx constants (use the import tag :prio
476	to get then):	590	to get then):
477		591
478	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	592	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
479	3 > 1 > 0 > -1 > -3 > -4	593	3 > 1 > 0 > -1 > -3 > -4
480		594
481	# set priority to HIGH	595	# set priority to HIGH
482	current->prio(PRIO_HIGH);	596	current->prio (PRIO_HIGH);
483		597
484	The idle coroutine ($Coro::idle) always has a lower priority than any	598	The idle coro ($Coro::idle) always has a lower priority than any
485	existing coroutine.	599	existing coro.
486		600
487	Changing the priority of the current coroutine will take effect immediately,	601	Changing the priority of the current coro will take effect immediately,
488	but changing the priority of coroutines in the ready queue (but not	602	but changing the priority of coro in the ready queue (but not
489	running) will only take effect after the next schedule (of that	603	running) will only take effect after the next schedule (of that
490	coroutine). This is a bug that will be fixed in some future version.	604	coro). This is a bug that will be fixed in some future version.
491		605
492	=item $newprio = $coroutine->nice ($change)	606	=item $newprio = $coro->nice ($change)
493		607
494	Similar to C<prio>, but subtract the given value from the priority (i.e.	608	Similar to C<prio>, but subtract the given value from the priority (i.e.
495	higher values mean lower priority, just as in unix).	609	higher values mean lower priority, just as in unix).
496		610
497	=item $olddesc = $coroutine->desc ($newdesc)	611	=item $olddesc = $coro->desc ($newdesc)
498		612
499	Sets (or gets in case the argument is missing) the description for this	613	Sets (or gets in case the argument is missing) the description for this
500	coroutine. This is just a free-form string you can associate with a	614	coro. This is just a free-form string you can associate with a
501	coroutine.	615	coro.
502		616
503	This method simply sets the C<< $coroutine->{desc} >> member to the given	617	This method simply sets the C<< $coro->{desc} >> member to the given
504	string. You can modify this member directly if you wish.	618	string. You can modify this member directly if you wish, and in fact, this
		619	is often preferred to indicate major processing states that cna then be
		620	seen for example in a L<Coro::Debug> session:
		621
		622	sub my_long_function {
		623	local $Coro::current->{desc} = "now in my_long_function";
		624	...
		625	$Coro::current->{desc} = "my_long_function: phase 1";
		626	...
		627	$Coro::current->{desc} = "my_long_function: phase 2";
		628	...
		629	}
505		630
506	=cut	631	=cut
507		632
508	sub desc {	633	sub desc {
509	my $old = $_[0]{desc};	634	my $old = $_[0]{desc};
…		…
522		647
523	=over 4	648	=over 4
524		649
525	=item Coro::nready	650	=item Coro::nready
526		651
527	Returns the number of coroutines that are currently in the ready state,	652	Returns the number of coro that are currently in the ready state,
528	i.e. that can be switched to by calling C<schedule> directory or	653	i.e. that can be switched to by calling C<schedule> directory or
529	indirectly. The value C<0> means that the only runnable coroutine is the	654	indirectly. The value C<0> means that the only runnable coro is the
530	currently running one, so C<cede> would have no effect, and C<schedule>	655	currently running one, so C<cede> would have no effect, and C<schedule>
531	would cause a deadlock unless there is an idle handler that wakes up some	656	would cause a deadlock unless there is an idle handler that wakes up some
532	coroutines.	657	coro.
533		658
534	=item my $guard = Coro::guard { ... }	659	=item my $guard = Coro::guard { ... }
535		660
536	This creates and returns a guard object. Nothing happens until the object	661	This function still exists, but is deprecated. Please use the
537	gets destroyed, in which case the codeblock given as argument will be	662	C<Guard::guard> function instead.
538	executed. This is useful to free locks or other resources in case of a
539	runtime error or when the coroutine gets canceled, as in both cases the
540	guard block will be executed. The guard object supports only one method,
541	C<< ->cancel >>, which will keep the codeblock from being executed.
542		663
543	Example: set some flag and clear it again when the coroutine gets canceled
544	or the function returns:
545
546	sub do_something {
547	my $guard = Coro::guard { $busy = 0 };
548	$busy = 1;
549
550	# do something that requires $busy to be true
551	}
552
553	=cut	664	=cut
554		665
555	sub guard(&) {	666	BEGIN { *guard = \&Guard::guard }
556	bless \(my $cb = $_[0]), "Coro::guard"
557	}
558
559	sub Coro::guard::cancel {
560	${$_[0]} = sub { };
561	}
562
563	sub Coro::guard::DESTROY {
564	${$_[0]}->();
565	}
566
567		667
568	=item unblock_sub { ... }	668	=item unblock_sub { ... }
569		669
570	This utility function takes a BLOCK or code reference and "unblocks" it,	670	This utility function takes a BLOCK or code reference and "unblocks" it,
571	returning a new coderef. Unblocking means that calling the new coderef	671	returning a new coderef. Unblocking means that calling the new coderef
572	will return immediately without blocking, returning nothing, while the	672	will return immediately without blocking, returning nothing, while the
573	original code ref will be called (with parameters) from within another	673	original code ref will be called (with parameters) from within another
574	coroutine.	674	coro.
575		675
576	The reason this function exists is that many event libraries (such as the	676	The reason this function exists is that many event libraries (such as
577	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form	677	the venerable L<Event\|Event> module) are not thread-safe (a weaker form
578	of thread-safety). This means you must not block within event callbacks,	678	of reentrancy). This means you must not block within event callbacks,
579	otherwise you might suffer from crashes or worse. The only event library	679	otherwise you might suffer from crashes or worse. The only event library
580	currently known that is safe to use without C<unblock_sub> is L<EV>.	680	currently known that is safe to use without C<unblock_sub> is L<EV> (but
		681	you might still run into deadlocks if all event loops are blocked).
		682
		683	Coro will try to catch you when you block in the event loop
		684	("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and
		685	only works when you do not run your own event loop.
581		686
582	This function allows your callbacks to block by executing them in another	687	This function allows your callbacks to block by executing them in another
583	coroutine where it is safe to block. One example where blocking is handy	688	coro where it is safe to block. One example where blocking is handy
584	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	689	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
585	disk, for example.	690	disk, for example.
586		691
587	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	692	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
588	creating event callbacks that want to block.	693	creating event callbacks that want to block.
589		694
590	If your handler does not plan to block (e.g. simply sends a message to	695	If your handler does not plan to block (e.g. simply sends a message to
591	another coroutine, or puts some other coroutine into the ready queue),	696	another coro, or puts some other coro into the ready queue), there is
592	there is no reason to use C<unblock_sub>.	697	no reason to use C<unblock_sub>.
593		698
594	Note that you also need to use C<unblock_sub> for any other callbacks that	699	Note that you also need to use C<unblock_sub> for any other callbacks that
595	are indirectly executed by any C-based event loop. For example, when you	700	are indirectly executed by any C-based event loop. For example, when you
596	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it	701	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
597	provides callbacks that are the result of some event callback, then you	702	provides callbacks that are the result of some event callback, then you
…		…
627	unshift @unblock_queue, [$cb, @_];	732	unshift @unblock_queue, [$cb, @_];
628	$unblock_scheduler->ready;	733	$unblock_scheduler->ready;
629	}	734	}
630	}	735	}
631		736
632	=item $cb = Coro::rouse_cb	737	=item $cb = rouse_cb
633		738
634	Create and return a "rouse callback". That's a code reference that, when	739	Create and return a "rouse callback". That's a code reference that,
635	called, will save its arguments and notify the owner coroutine of the	740	when called, will remember a copy of its arguments and notify the owner
636	callback.	741	coro of the callback.
637		742
638	See the next function.	743	See the next function.
639		744
640	=item @args = Coro::rouse_wait [$cb]	745	=item @args = rouse_wait [$cb]
641		746
642	Wait for the specified rouse callback (or the last one tht was created in	747	Wait for the specified rouse callback (or the last one that was created in
643	this coroutine).	748	this coro).
644		749
645	As soon as the callback is invoked (or when the calback was invoked before	750	As soon as the callback is invoked (or when the callback was invoked
646	C<rouse_wait>), it will return a copy of the arguments originally passed	751	before C<rouse_wait>), it will return the arguments originally passed to
647	to the rouse callback.	752	the rouse callback. In scalar context, that means you get the I<last>
		753	argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
		754	statement at the end.
648		755
649	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.	756	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
650		757
651	=back	758	=back
652		759
653	=cut	760	=cut
654		761
		762	for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) {
		763	my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"};
		764
		765	*{"Coro::$module\::new"} = sub {
		766	require "Coro/$module.pm";
		767
		768	# some modules have their new predefined in State.xs, some don't
		769	*{"Coro::$module\::new"} = $old
		770	if $old;
		771
		772	goto &{"Coro::$module\::new"};
		773	};
		774	}
		775
655	1;	776	1;
656		777
657	=head1 HOW TO WAIT FOR A CALLBACK	778	=head1 HOW TO WAIT FOR A CALLBACK
658		779
659	It is very common for a coroutine to wait for some callback to be	780	It is very common for a coro to wait for some callback to be
660	called. This occurs naturally when you use coroutines in an otherwise	781	called. This occurs naturally when you use coro in an otherwise
661	event-based program, or when you use event-based libraries.	782	event-based program, or when you use event-based libraries.
662		783
663	These typically register a callback for some event, and call that callback	784	These typically register a callback for some event, and call that callback
664	when the event occured. In a coroutine, however, you typically want to	785	when the event occured. In a coro, however, you typically want to
665	just wait for the event, simplyifying things.	786	just wait for the event, simplyifying things.
666		787
667	For example C<< AnyEvent->child >> registers a callback to be called when	788	For example C<< AnyEvent->child >> registers a callback to be called when
668	a specific child has exited:	789	a specific child has exited:
669		790
670	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });	791	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
671		792
672	But from withina coroutine, you often just want to write this:	793	But from within a coro, you often just want to write this:
673		794
674	my $status = wait_for_child $pid;	795	my $status = wait_for_child $pid;
675		796
676	Coro offers two functions specifically designed to make this easy,	797	Coro offers two functions specifically designed to make this easy,
677	C<Coro::rouse_cb> and C<Coro::rouse_wait>.	798	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
678		799
679	The first function, C<rouse_cb>, generates and returns a callback that,	800	The first function, C<rouse_cb>, generates and returns a callback that,
680	when invoked, will save it's arguments and notify the coroutine that	801	when invoked, will save its arguments and notify the coro that
681	created the callback.	802	created the callback.
682		803
683	The second function, C<rouse_wait>, waits for the callback to be called	804	The second function, C<rouse_wait>, waits for the callback to be called
684	(by calling C<schedule> to go to sleep) and returns the arguments	805	(by calling C<schedule> to go to sleep) and returns the arguments
685	originally passed to the callback.	806	originally passed to the callback.
…		…
700	you can roll your own, using C<schedule>:	821	you can roll your own, using C<schedule>:
701		822
702	sub wait_for_child($) {	823	sub wait_for_child($) {
703	my ($pid) = @_;	824	my ($pid) = @_;
704		825
705	# store the current coroutine in $current,	826	# store the current coro in $current,
706	# and provide result variables for the closure passed to ->child	827	# and provide result variables for the closure passed to ->child
707	my $current = $Coro::current;	828	my $current = $Coro::current;
708	my ($done, $rstatus);	829	my ($done, $rstatus);
709		830
710	# pass a closure to ->child	831	# pass a closure to ->child
…		…
726		847
727	=item fork with pthread backend	848	=item fork with pthread backend
728		849
729	When Coro is compiled using the pthread backend (which isn't recommended	850	When Coro is compiled using the pthread backend (which isn't recommended
730	but required on many BSDs as their libcs are completely broken), then	851	but required on many BSDs as their libcs are completely broken), then
731	coroutines will not survive a fork. There is no known workaround except to	852	coro will not survive a fork. There is no known workaround except to
732	fix your libc and use a saner backend.	853	fix your libc and use a saner backend.
733		854
734	=item perl process emulation ("threads")	855	=item perl process emulation ("threads")
735		856
736	This module is not perl-pseudo-thread-safe. You should only ever use this	857	This module is not perl-pseudo-thread-safe. You should only ever use this
737	module from the same thread (this requirement might be removed in the	858	module from the first thread (this requirement might be removed in the
738	future to allow per-thread schedulers, but Coro::State does not yet allow	859	future to allow per-thread schedulers, but Coro::State does not yet allow
739	this). I recommend disabling thread support and using processes, as having	860	this). I recommend disabling thread support and using processes, as having
740	the windows process emulation enabled under unix roughly halves perl	861	the windows process emulation enabled under unix roughly halves perl
741	performance, even when not used.	862	performance, even when not used.
742		863
743	=item coroutine switching not signal safe	864	=item coro switching is not signal safe
744		865
745	You must not switch to another coroutine from within a signal handler	866	You must not switch to another coro from within a signal handler (only
746	(only relevant with %SIG - most event libraries provide safe signals).	867	relevant with %SIG - most event libraries provide safe signals), I<unless>
		868	you are sure you are not interrupting a Coro function.
747		869
748	That means you I<MUST NOT> call any function that might "block" the	870	That means you I<MUST NOT> call any function that might "block" the
749	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or	871	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
750	anything that calls those. Everything else, including calling C<ready>,	872	anything that calls those. Everything else, including calling C<ready>,
751	works.	873	works.
752		874
753	=back	875	=back
754		876
755		877
		878	=head1 WINDOWS PROCESS EMULATION
		879
		880	A great many people seem to be confused about ithreads (for example, Chip
		881	Salzenberg called me unintelligent, incapable, stupid and gullible,
		882	while in the same mail making rather confused statements about perl
		883	ithreads (for example, that memory or files would be shared), showing his
		884	lack of understanding of this area - if it is hard to understand for Chip,
		885	it is probably not obvious to everybody).
		886
		887	What follows is an ultra-condensed version of my talk about threads in
		888	scripting languages given on the perl workshop 2009:
		889
		890	The so-called "ithreads" were originally implemented for two reasons:
		891	first, to (badly) emulate unix processes on native win32 perls, and
		892	secondly, to replace the older, real thread model ("5.005-threads").
		893
		894	It does that by using threads instead of OS processes. The difference
		895	between processes and threads is that threads share memory (and other
		896	state, such as files) between threads within a single process, while
		897	processes do not share anything (at least not semantically). That
		898	means that modifications done by one thread are seen by others, while
		899	modifications by one process are not seen by other processes.
		900
		901	The "ithreads" work exactly like that: when creating a new ithreads
		902	process, all state is copied (memory is copied physically, files and code
		903	is copied logically). Afterwards, it isolates all modifications. On UNIX,
		904	the same behaviour can be achieved by using operating system processes,
		905	except that UNIX typically uses hardware built into the system to do this
		906	efficiently, while the windows process emulation emulates this hardware in
		907	software (rather efficiently, but of course it is still much slower than
		908	dedicated hardware).
		909
		910	As mentioned before, loading code, modifying code, modifying data
		911	structures and so on is only visible in the ithreads process doing the
		912	modification, not in other ithread processes within the same OS process.
		913
		914	This is why "ithreads" do not implement threads for perl at all, only
		915	processes. What makes it so bad is that on non-windows platforms, you can
		916	actually take advantage of custom hardware for this purpose (as evidenced
		917	by the forks module, which gives you the (i-) threads API, just much
		918	faster).
		919
		920	Sharing data is in the i-threads model is done by transfering data
		921	structures between threads using copying semantics, which is very slow -
		922	shared data simply does not exist. Benchmarks using i-threads which are
		923	communication-intensive show extremely bad behaviour with i-threads (in
		924	fact, so bad that Coro, which cannot take direct advantage of multiple
		925	CPUs, is often orders of magnitude faster because it shares data using
		926	real threads, refer to my talk for details).
		927
		928	As summary, i-threads use threads to implement processes, while
		929	the compatible forks module uses processes to emulate, uhm,
		930	processes. I-threads slow down every perl program when enabled, and
		931	outside of windows, serve no (or little) practical purpose, but
		932	disadvantages every single-threaded Perl program.
		933
		934	This is the reason that I try to avoid the name "ithreads", as it is
		935	misleading as it implies that it implements some kind of thread model for
		936	perl, and prefer the name "windows process emulation", which describes the
		937	actual use and behaviour of it much better.
		938
756	=head1 SEE ALSO	939	=head1 SEE ALSO
757		940
758	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.	941	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
759		942
760	Debugging: L<Coro::Debug>.	943	Debugging: L<Coro::Debug>.
761		944
762	Support/Utility: L<Coro::Specific>, L<Coro::Util>.	945	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
763		946
764	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,	947	Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
765	L<Coro::SemaphoreSet>, L<Coro::RWLock>.	948	L<Coro::SemaphoreSet>, L<Coro::RWLock>.
766		949
767	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.	950	I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
768		951
769	Compatibility: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for	952	Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
770	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,	953	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
771	L<Coro::Select>.	954	L<Coro::Select>.
772		955
773	XS API: L<Coro::MakeMaker>.	956	XS API: L<Coro::MakeMaker>.
774		957
775	Low level Configuration, Coroutine Environment: L<Coro::State>.	958	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
776		959
777	=head1 AUTHOR	960	=head1 AUTHOR
778		961
779	Marc Lehmann <schmorp@schmorp.de>	962	Marc Lehmann <schmorp@schmorp.de>
780	http://home.schmorp.de/	963	http://home.schmorp.de/

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Revision 1.283 by root, Sat Feb 5 21:20:47 2011 UTC