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

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Revision 1.244 by root, Sat Dec 13 22:08:13 2008 UTC vs.
Revision 1.274 by root, Sat Dec 12 01:30:26 2009 UTC

…		…
11	print "2\n";	11	print "2\n";
12	cede; # yield back to main	12	cede; # yield back to main
13	print "4\n";	13	print "4\n";
14	};	14	};
15	print "1\n";	15	print "1\n";
16	cede; # yield to coroutine	16	cede; # yield to coro
17	print "3\n";	17	print "3\n";
18	cede; # and again	18	cede; # and again
19		19
20	# use locking	20	# use locking
21	use Coro::Semaphore;	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 continuations in general, most often	34	This module collection manages continuations in general, most often in
35	in the form of cooperative threads (also called coroutines in the	35	the form of cooperative threads (also called coros, or simply "coro"
36	documentation). They are similar to kernel threads but don't (in general)	36	in the documentation). They are similar to kernel threads but don't (in
37	run in parallel at the same time even on SMP machines. The specific flavor	37	general) run in parallel at the same time even on SMP machines. The
38	of thread offered by this module also guarantees you that it will not	38	specific flavor of thread offered by this module also guarantees you that
39	switch between threads unless necessary, at easily-identified points in	39	it will not switch between threads unless necessary, at easily-identified
40	your program, so locking and parallel access are rarely an issue, making	40	points in your program, so locking and parallel access are rarely an
41	thread programming much safer and easier than using other thread models.	41	issue, making thread programming much safer and easier than using other
		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 threads	47	a full shared address space, which makes communication between threads
46	very easy. And threads 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 thread is defined as "callchain + lexical variables +	60	In this module, a thread is defined as "callchain + lexical variables +
57	@_ + $_ + $@ + $/ + C stack), that is, a thread has its own callchain,	61	some package variables + C stack), that is, a thread has its own callchain,
58	its own set of lexicals and its own set of perls most important global	62	its own set of lexicals and its own set of perls most important global
59	variables (see L<Coro::State> for more configuration and background info).	63	variables (see L<Coro::State> for more configuration and background info).
60		64
61	See also the C<SEE ALSO> section at the end of this document - the Coro	65	See also the C<SEE ALSO> section at the end of this document - the Coro
62	module family is quite large.	66	module family is quite large.
63		67
64	=cut	68	=cut
65		69
66	package Coro;	70	package Coro;
67		71
68	use strict qw(vars subs);	72	use common::sense;
69	no warnings "uninitialized";	73
		74	use Carp ();
		75
		76	use Guard ();
70		77
71	use Coro::State;	78	use Coro::State;
72		79
73	use base qw(Coro::State Exporter);	80	use base qw(Coro::State Exporter);
74		81
75	our $idle; # idle handler	82	our $idle; # idle handler
76	our $main; # main coroutine	83	our $main; # main coro
77	our $current; # current coroutine	84	our $current; # current coro
78		85
79	our $VERSION = 5.13;	86	our $VERSION = 5.21;
80		87
81	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	88	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
82	our %EXPORT_TAGS = (	89	our %EXPORT_TAGS = (
83	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	90	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
84	);	91	);
85	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	92	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
86		93
…		…
88		95
89	=over 4	96	=over 4
90		97
91	=item $Coro::main	98	=item $Coro::main
92		99
93	This variable stores the coroutine object that represents the main	100	This variable stores the Coro object that represents the main
94	program. While you cna C<ready> it and do most other things you can do to	101	program. While you cna C<ready> it and do most other things you can do to
95	coroutines, it is mainly useful to compare again C<$Coro::current>, to see	102	coro, it is mainly useful to compare again C<$Coro::current>, to see
96	whether you are running in the main program or not.	103	whether you are running in the main program or not.
97		104
98	=cut	105	=cut
99		106
100	# $main is now being initialised by Coro::State	107	# $main is now being initialised by Coro::State
101		108
102	=item $Coro::current	109	=item $Coro::current
103		110
104	The coroutine object representing the current coroutine (the last	111	The Coro object representing the current coro (the last
105	coroutine that the Coro scheduler switched to). The initial value is	112	coro that the Coro scheduler switched to). The initial value is
106	C<$Coro::main> (of course).	113	C<$Coro::main> (of course).
107		114
108	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
109	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
110	not otherwise modify the variable itself.	117	not otherwise modify the variable itself.
111		118
112	=cut	119	=cut
113		120
114	sub current() { $current } # [DEPRECATED]	121	sub current() { $current } # [DEPRECATED]
…		…
117		124
118	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
119	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is	126	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
120	pretty low-level functionality.	127	pretty low-level functionality.
121		128
122	This variable stores either a coroutine or a callback.	129	This variable stores a Coro object that is put into the ready queue when
		130	there are no other ready threads (without invoking any ready hooks).
123		131
124	If it is a callback, the it is called whenever the scheduler finds no	132	The default implementation dies with "FATAL: deadlock detected.", followed
125	ready coroutines to run. The default implementation prints "FATAL:	133	by a thread listing, because the program has no other way to continue.
126	deadlock detected" and exits, because the program has no other way to
127	continue.
128
129	If it is a coroutine object, then this object will be readied (without
130	invoking any ready hooks, however) when the scheduler finds no other ready
131	coroutines to run.
132		134
133	This hook is overwritten by modules such as C<Coro::EV> and	135	This hook is overwritten by modules such as C<Coro::EV> and
134	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a	136	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
135	coroutine so the scheduler can run it.	137	coro so the scheduler can run it.
136		138
137	Note that the callback I<must not>, under any circumstances, block
138	the current coroutine. Normally, this is achieved by having an "idle
139	coroutine" that calls the event loop and then blocks again, and then
140	readying that coroutine in the idle handler, or by simply placing the idle
141	coroutine in this variable.
142
143	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this	139	See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
144	technique.
145		140
146	Please note that if your callback recursively invokes perl (e.g. for event
147	handlers), then it must be prepared to be called recursively itself.
148
149	=cut	141	=cut
150		142
151	$idle = sub {	143	$idle = new Coro sub {
152	require Carp;	144	require Coro::Debug;
153	Carp::croak ("FATAL: deadlock detected");	145	die "FATAL: deadlock detected.\n"
		146	. Coro::Debug::ps_listing ();
154	};	147	};
155		148
156	# this coroutine is necessary because a coroutine	149	# this coro is necessary because a coro
157	# cannot destroy itself.	150	# cannot destroy itself.
158	our @destroy;	151	our @destroy;
159	our $manager;	152	our $manager;
160		153
161	$manager = new Coro sub {	154	$manager = new Coro sub {
162	while () {	155	while () {
163	Coro::_cancel shift @destroy	156	Coro::State::cancel shift @destroy
164	while @destroy;	157	while @destroy;
165		158
166	&schedule;	159	&schedule;
167	}	160	}
168	};	161	};
169	$manager->{desc} = "[coro manager]";	162	$manager->{desc} = "[coro manager]";
170	$manager->prio (PRIO_MAX);	163	$manager->prio (PRIO_MAX);
171		164
172	=back	165	=back
173		166
174	=head1 SIMPLE COROUTINE CREATION	167	=head1 SIMPLE CORO CREATION
175		168
176	=over 4	169	=over 4
177		170
178	=item async { ... } [@args...]	171	=item async { ... } [@args...]
179		172
180	Create a new coroutine and return its coroutine object (usually	173	Create a new coro and return its Coro object (usually
181	unused). The coroutine will be put into the ready queue, so	174	unused). The coro will be put into the ready queue, so
182	it will start running automatically on the next scheduler run.	175	it will start running automatically on the next scheduler run.
183		176
184	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
185	coroutine. When it returns argument returns the coroutine is automatically	178	coro. When it returns argument returns the coro is automatically
186	terminated.	179	terminated.
187		180
188	The remaining arguments are passed as arguments to the closure.	181	The remaining arguments are passed as arguments to the closure.
189		182
190	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
191	environment in which coroutines are executed.	184	environment in which coro are executed.
192		185
193	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
194	the coroutine. Likewise, when the coroutine dies, the program will exit,	187	the coro. Likewise, when the coro dies, the program will exit,
195	just as it would in the main program.	188	just as it would in the main program.
196		189
197	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
198	simply avoid dieing (by use of C<eval>).	191	simply avoid dieing (by use of C<eval>).
199		192
200	Example: Create a new coroutine that just prints its arguments.	193	Example: Create a new coro that just prints its arguments.
201		194
202	async {	195	async {
203	print "@_\n";	196	print "@_\n";
204	} 1,2,3,4;	197	} 1,2,3,4;
205		198
206	=cut
207
208	sub async(&@) {
209	my $coro = new Coro @_;
210	$coro->ready;
211	$coro
212	}
213
214	=item async_pool { ... } [@args...]	199	=item async_pool { ... } [@args...]
215		200
216	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
217	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
218	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
219	or bad :).	204	or bad :).
220		205
221	On the plus side, this function is about twice as fast as creating (and	206	On the plus side, this function is about twice as fast as creating (and
222	destroying) a completely new coroutine, so if you need a lot of generic	207	destroying) a completely new coro, so if you need a lot of generic
223	coroutines in quick successsion, use C<async_pool>, not C<async>.	208	coros in quick successsion, use C<async_pool>, not C<async>.
224		209
225	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
226	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
227	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>
228	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,
229	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
230	exceptional case).	215	exceptional case).
231		216
232	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
233	disabled, the description will be reset and the default output filehandle	218	disabled, the description will be reset and the default output filehandle
234	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
235	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
236	stuff such as C<$/> you I<must needs> revert that change, which is most	221	stuff such as C<$/> you I<must needs> revert that change, which is most
237	simply done by using local as in: C<< local $/ >>.	222	simply done by using local as in: C<< local $/ >>.
238		223
239	The idle pool size is limited to C<8> idle coroutines (this can be	224	The idle pool size is limited to C<8> idle coros (this can be
240	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle	225	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
241	coros as required.	226	coros as required.
242		227
243	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
244	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
245	{ 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
246	addition to that, when the stacks used by a handler grows larger than 32kb	231	addition to that, when the stacks used by a handler grows larger than 32kb
247	(adjustable via $Coro::POOL_RSS) it will also be destroyed.	232	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
248		233
…		…
265	=back	250	=back
266		251
267	=head1 STATIC METHODS	252	=head1 STATIC METHODS
268		253
269	Static methods are actually functions that implicitly operate on the	254	Static methods are actually functions that implicitly operate on the
270	current coroutine.	255	current coro.
271		256
272	=over 4	257	=over 4
273		258
274	=item schedule	259	=item schedule
275		260
276	Calls the scheduler. The scheduler will find the next coroutine that is	261	Calls the scheduler. The scheduler will find the next coro that is
277	to be run from the ready queue and switches to it. The next coroutine	262	to be run from the ready queue and switches to it. The next coro
278	to be run is simply the one with the highest priority that is longest	263	to be run is simply the one with the highest priority that is longest
279	in its ready queue. If there is no coroutine ready, it will clal the	264	in its ready queue. If there is no coro ready, it will call the
280	C<$Coro::idle> hook.	265	C<$Coro::idle> hook.
281		266
282	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
283	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
284	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 >>,
285	thus waking you up.	270	thus waking you up.
286		271
287	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
288	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
289	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
290	>> 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
291	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,
292	so you need to check whether 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
293	status in a variable.	278	status in a variable.
294		279
295	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.	280	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
296		281
297	=item cede	282	=item cede
298		283
299	"Cede" to other coroutines. This function puts the current coroutine into	284	"Cede" to other coros. This function puts the current coro into
300	the ready queue and calls C<schedule>, which has the effect of giving	285	the ready queue and calls C<schedule>, which has the effect of giving
301	up the current "timeslice" to other coroutines of the same or higher	286	up the current "timeslice" to other coros of the same or higher
302	priority. Once your coroutine gets its turn again it will automatically be	287	priority. Once your coro gets its turn again it will automatically be
303	resumed.	288	resumed.
304		289
305	This function is often called C<yield> in other languages.	290	This function is often called C<yield> in other languages.
306		291
307	=item Coro::cede_notself	292	=item Coro::cede_notself
308		293
309	Works like cede, but is not exported by default and will cede to I<any>	294	Works like cede, but is not exported by default and will cede to I<any>
310	coroutine, regardless of priority. This is useful sometimes to ensure	295	coro, regardless of priority. This is useful sometimes to ensure
311	progress is made.	296	progress is made.
312		297
313	=item terminate [arg...]	298	=item terminate [arg...]
314		299
315	Terminates the current coroutine with the given status values (see L<cancel>).	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
		343	};
		344
		345	Coro::on_leave {
		346	$ENV{TZ} = $old_tz;
		347	tzset; # restore old value
		348	};
		349
		350	# at this place, the timezone is Antarctica/South_Pole,
		351	# without disturbing the TZ of any other coro.
		352	};
		353
		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.
		357
		358	Another interesting example implements time-sliced multitasking using
		359	interval timers (this could obviously be optimised, but does the job):
		360
		361	# "timeslice" the given block
		362	sub timeslice(&) {
		363	use Time::HiRes ();
		364
		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	};
		375
		376	&{+shift};
		377	}
		378
		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	};
		386
316		387
317	=item killall	388	=item killall
318		389
319	Kills/terminates/cancels all coroutines except the currently running	390	Kills/terminates/cancels all coros except the currently running one.
320	one. This is useful after a fork, either in the child or the parent, as
321	usually only one of them should inherit the running coroutines.
322		391
323	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
324	you cannot 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
325	program calls this function, there will be some one-time resource leak.	395	calls this function, there will be some one-time resource leak.
326		396
327	=cut	397	=cut
328		398
329	sub killall {	399	sub killall {
330	for (Coro::State::list) {	400	for (Coro::State::list) {
…		…
333	}	403	}
334	}	404	}
335		405
336	=back	406	=back
337		407
338	=head1 COROUTINE OBJECT METHODS	408	=head1 CORO OBJECT METHODS
339		409
340	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
341	them).	411	them).
342		412
343	=over 4	413	=over 4
344		414
345	=item new Coro \&sub [, @args...]	415	=item new Coro \&sub [, @args...]
346		416
347	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
348	automatically terminates as if C<terminate> with the returned values were	418	automatically terminates as if C<terminate> with the returned values were
349	called. To make the coroutine run you must first put it into the ready	419	called. To make the coro run you must first put it into the ready
350	queue by calling the ready method.	420	queue by calling the ready method.
351		421
352	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
353	coroutine environment.	423	coro environment.
354		424
355	=cut	425	=cut
356		426
357	sub _coro_run {	427	sub _coro_run {
358	terminate &{+shift};	428	terminate &{+shift};
359	}	429	}
360		430
361	=item $success = $coroutine->ready	431	=item $success = $coro->ready
362		432
363	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
364	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
365	the ready queue, do nothing and return false.	435	the ready queue, do nothing and return false.
366		436
367	This ensures that the scheduler will resume this coroutine automatically	437	This ensures that the scheduler will resume this coro automatically
368	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
369	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.
370		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
371	=item $is_ready = $coroutine->is_ready	466	=item $is_ready = $coro->is_ready
372		467
373	Return whether 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.
374		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
375	=item $coroutine->cancel (arg...)	482	=item $coro->cancel (arg...)
376		483
377	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
378	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
379	current coroutine.	486	current Coro.
380		487
381	=cut	488	=cut
382		489
383	sub cancel {	490	sub cancel {
384	my $self = shift;	491	my $self = shift;
385		492
386	if ($current == $self) {	493	if ($current == $self) {
387	terminate @_;	494	terminate @_;
388	} else {	495	} else {
389	$self->{_status} = [@_];	496	$self->{_status} = [@_];
390	$self->_cancel;	497	Coro::State::cancel $self;
391	}	498	}
392	}	499	}
393		500
394	=item $coroutine->schedule_to	501	=item $coro->schedule_to
395		502
396	Puts the current coroutine to sleep (like C<Coro::schedule>), but instead	503	Puts the current coro to sleep (like C<Coro::schedule>), but instead
397	of continuing with the next coro from the ready queue, always switch to	504	of continuing with the next coro from the ready queue, always switch to
398	the given coroutine object (regardless of priority etc.). The readyness	505	the given coro object (regardless of priority etc.). The readyness
399	state of that coroutine isn't changed.	506	state of that coro isn't changed.
400		507
401	This is an advanced method for special cases - I'd love to hear about any	508	This is an advanced method for special cases - I'd love to hear about any
402	uses for this one.	509	uses for this one.
403		510
404	=item $coroutine->cede_to	511	=item $coro->cede_to
405		512
406	Like C<schedule_to>, but puts the current coroutine into the ready	513	Like C<schedule_to>, but puts the current coro into the ready
407	queue. This has the effect of temporarily switching to the given	514	queue. This has the effect of temporarily switching to the given
408	coroutine, and continuing some time later.	515	coro, and continuing some time later.
409		516
410	This is an advanced method for special cases - I'd love to hear about any	517	This is an advanced method for special cases - I'd love to hear about any
411	uses for this one.	518	uses for this one.
412		519
413	=item $coroutine->throw ([$scalar])	520	=item $coro->throw ([$scalar])
414		521
415	If C<$throw> is specified and defined, it will be thrown as an exception	522	If C<$throw> is specified and defined, it will be thrown as an exception
416	inside the coroutine at the next convenient point in time. Otherwise	523	inside the coro at the next convenient point in time. Otherwise
417	clears the exception object.	524	clears the exception object.
418		525
419	Coro will check for the exception each time a schedule-like-function	526	Coro will check for the exception each time a schedule-like-function
420	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down	527	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
421	>>, C<< Coro::Handle->readable >> and so on. Most of these functions	528	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
…		…
423		530
424	The exception object will be thrown "as is" with the specified scalar in	531	The exception object will be thrown "as is" with the specified scalar in
425	C<$@>, i.e. if it is a string, no line number or newline will be appended	532	C<$@>, i.e. if it is a string, no line number or newline will be appended
426	(unlike with C<die>).	533	(unlike with C<die>).
427		534
428	This can be used as a softer means than C<cancel> to ask a coroutine to	535	This can be used as a softer means than C<cancel> to ask a coro to
429	end itself, although there is no guarantee that the exception will lead to	536	end itself, although there is no guarantee that the exception will lead to
430	termination, and if the exception isn't caught it might well end the whole	537	termination, and if the exception isn't caught it might well end the whole
431	program.	538	program.
432		539
433	You might also think of C<throw> as being the moral equivalent of	540	You might also think of C<throw> as being the moral equivalent of
434	C<kill>ing a coroutine with a signal (in this case, a scalar).	541	C<kill>ing a coro with a signal (in this case, a scalar).
435		542
436	=item $coroutine->join	543	=item $coro->join
437		544
438	Wait until the coroutine terminates and return any values given to the	545	Wait until the coro terminates and return any values given to the
439	C<terminate> or C<cancel> functions. C<join> can be called concurrently	546	C<terminate> or C<cancel> functions. C<join> can be called concurrently
440	from multiple coroutines, and all will be resumed and given the status	547	from multiple coro, and all will be resumed and given the status
441	return once the C<$coroutine> terminates.	548	return once the C<$coro> terminates.
442		549
443	=cut	550	=cut
444		551
445	sub join {	552	sub join {
446	my $self = shift;	553	my $self = shift;
…		…
457	}	564	}
458		565
459	wantarray ? @{$self->{_status}} : $self->{_status}[0];	566	wantarray ? @{$self->{_status}} : $self->{_status}[0];
460	}	567	}
461		568
462	=item $coroutine->on_destroy (\&cb)	569	=item $coro->on_destroy (\&cb)
463		570
464	Registers a callback that is called when this coroutine gets destroyed,	571	Registers a callback that is called when this coro gets destroyed,
465	but before it is joined. The callback gets passed the terminate arguments,	572	but before it is joined. The callback gets passed the terminate arguments,
466	if any, and I<must not> die, under any circumstances.	573	if any, and I<must not> die, under any circumstances.
467		574
468	=cut	575	=cut
469		576
…		…
471	my ($self, $cb) = @_;	578	my ($self, $cb) = @_;
472		579
473	push @{ $self->{_on_destroy} }, $cb;	580	push @{ $self->{_on_destroy} }, $cb;
474	}	581	}
475		582
476	=item $oldprio = $coroutine->prio ($newprio)	583	=item $oldprio = $coro->prio ($newprio)
477		584
478	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
479	coroutine. Higher priority coroutines get run before lower priority	586	coro. Higher priority coro get run before lower priority
480	coroutines. Priorities are small signed integers (currently -4 .. +3),	587	coro. Priorities are small signed integers (currently -4 .. +3),
481	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
482	to get then):	589	to get then):
483		590
484	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
485	3 > 1 > 0 > -1 > -3 > -4	592	3 > 1 > 0 > -1 > -3 > -4
486		593
487	# set priority to HIGH	594	# set priority to HIGH
488	current->prio(PRIO_HIGH);	595	current->prio (PRIO_HIGH);
489		596
490	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
491	existing coroutine.	598	existing coro.
492		599
493	Changing the priority of the current coroutine will take effect immediately,	600	Changing the priority of the current coro will take effect immediately,
494	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
495	running) will only take effect after the next schedule (of that	602	running) will only take effect after the next schedule (of that
496	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.
497		604
498	=item $newprio = $coroutine->nice ($change)	605	=item $newprio = $coro->nice ($change)
499		606
500	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.
501	higher values mean lower priority, just as in unix).	608	higher values mean lower priority, just as in unix).
502		609
503	=item $olddesc = $coroutine->desc ($newdesc)	610	=item $olddesc = $coro->desc ($newdesc)
504		611
505	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
506	coroutine. This is just a free-form string you can associate with a	613	coro. This is just a free-form string you can associate with a
507	coroutine.	614	coro.
508		615
509	This method simply sets the C<< $coroutine->{desc} >> member to the given	616	This method simply sets the C<< $coro->{desc} >> member to the given
510	string. You can modify this member directly if you wish.	617	string. You can modify this member directly if you wish.
511		618
512	=cut	619	=cut
513		620
514	sub desc {	621	sub desc {
…		…
528		635
529	=over 4	636	=over 4
530		637
531	=item Coro::nready	638	=item Coro::nready
532		639
533	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,
534	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
535	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
536	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>
537	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
538	coroutines.	645	coro.
539		646
540	=item my $guard = Coro::guard { ... }	647	=item my $guard = Coro::guard { ... }
541		648
542	This function still exists, but is deprecated. Please use the	649	This function still exists, but is deprecated. Please use the
543	C<Guard::guard> function instead.	650	C<Guard::guard> function instead.
…		…
550		657
551	This utility function takes a BLOCK or code reference and "unblocks" it,	658	This utility function takes a BLOCK or code reference and "unblocks" it,
552	returning a new coderef. Unblocking means that calling the new coderef	659	returning a new coderef. Unblocking means that calling the new coderef
553	will return immediately without blocking, returning nothing, while the	660	will return immediately without blocking, returning nothing, while the
554	original code ref will be called (with parameters) from within another	661	original code ref will be called (with parameters) from within another
555	coroutine.	662	coro.
556		663
557	The reason this function exists is that many event libraries (such as the	664	The reason this function exists is that many event libraries (such as the
558	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form	665	venerable L<Event\|Event> module) are not thread-safe (a weaker form
559	of reentrancy). This means you must not block within event callbacks,	666	of reentrancy). This means you must not block within event callbacks,
560	otherwise you might suffer from crashes or worse. The only event library	667	otherwise you might suffer from crashes or worse. The only event library
561	currently known that is safe to use without C<unblock_sub> is L<EV>.	668	currently known that is safe to use without C<unblock_sub> is L<EV>.
562		669
		670	Coro will try to catch you when you block in the event loop
		671	("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and
		672	only works when you do not run your own event loop.
		673
563	This function allows your callbacks to block by executing them in another	674	This function allows your callbacks to block by executing them in another
564	coroutine where it is safe to block. One example where blocking is handy	675	coro where it is safe to block. One example where blocking is handy
565	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	676	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
566	disk, for example.	677	disk, for example.
567		678
568	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	679	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
569	creating event callbacks that want to block.	680	creating event callbacks that want to block.
570		681
571	If your handler does not plan to block (e.g. simply sends a message to	682	If your handler does not plan to block (e.g. simply sends a message to
572	another coroutine, or puts some other coroutine into the ready queue),	683	another coro, or puts some other coro into the ready queue), there is
573	there is no reason to use C<unblock_sub>.	684	no reason to use C<unblock_sub>.
574		685
575	Note that you also need to use C<unblock_sub> for any other callbacks that	686	Note that you also need to use C<unblock_sub> for any other callbacks that
576	are indirectly executed by any C-based event loop. For example, when you	687	are indirectly executed by any C-based event loop. For example, when you
577	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it	688	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
578	provides callbacks that are the result of some event callback, then you	689	provides callbacks that are the result of some event callback, then you
…		…
608	unshift @unblock_queue, [$cb, @_];	719	unshift @unblock_queue, [$cb, @_];
609	$unblock_scheduler->ready;	720	$unblock_scheduler->ready;
610	}	721	}
611	}	722	}
612		723
613	=item $cb = Coro::rouse_cb	724	=item $cb = rouse_cb
614		725
615	Create and return a "rouse callback". That's a code reference that,	726	Create and return a "rouse callback". That's a code reference that,
616	when called, will remember a copy of its arguments and notify the owner	727	when called, will remember a copy of its arguments and notify the owner
617	coroutine of the callback.	728	coro of the callback.
618		729
619	See the next function.	730	See the next function.
620		731
621	=item @args = Coro::rouse_wait [$cb]	732	=item @args = rouse_wait [$cb]
622		733
623	Wait for the specified rouse callback (or the last one that was created in	734	Wait for the specified rouse callback (or the last one that was created in
624	this coroutine).	735	this coro).
625		736
626	As soon as the callback is invoked (or when the callback was invoked	737	As soon as the callback is invoked (or when the callback was invoked
627	before C<rouse_wait>), it will return the arguments originally passed to	738	before C<rouse_wait>), it will return the arguments originally passed to
628	the rouse callback.	739	the rouse callback. In scalar context, that means you get the I<last>
		740	argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
		741	statement at the end.
629		742
630	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.	743	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
631		744
632	=back	745	=back
633		746
…		…
635		748
636	1;	749	1;
637		750
638	=head1 HOW TO WAIT FOR A CALLBACK	751	=head1 HOW TO WAIT FOR A CALLBACK
639		752
640	It is very common for a coroutine to wait for some callback to be	753	It is very common for a coro to wait for some callback to be
641	called. This occurs naturally when you use coroutines in an otherwise	754	called. This occurs naturally when you use coro in an otherwise
642	event-based program, or when you use event-based libraries.	755	event-based program, or when you use event-based libraries.
643		756
644	These typically register a callback for some event, and call that callback	757	These typically register a callback for some event, and call that callback
645	when the event occured. In a coroutine, however, you typically want to	758	when the event occured. In a coro, however, you typically want to
646	just wait for the event, simplyifying things.	759	just wait for the event, simplyifying things.
647		760
648	For example C<< AnyEvent->child >> registers a callback to be called when	761	For example C<< AnyEvent->child >> registers a callback to be called when
649	a specific child has exited:	762	a specific child has exited:
650		763
651	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });	764	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
652		765
653	But from withina coroutine, you often just want to write this:	766	But from within a coro, you often just want to write this:
654		767
655	my $status = wait_for_child $pid;	768	my $status = wait_for_child $pid;
656		769
657	Coro offers two functions specifically designed to make this easy,	770	Coro offers two functions specifically designed to make this easy,
658	C<Coro::rouse_cb> and C<Coro::rouse_wait>.	771	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
659		772
660	The first function, C<rouse_cb>, generates and returns a callback that,	773	The first function, C<rouse_cb>, generates and returns a callback that,
661	when invoked, will save its arguments and notify the coroutine that	774	when invoked, will save its arguments and notify the coro that
662	created the callback.	775	created the callback.
663		776
664	The second function, C<rouse_wait>, waits for the callback to be called	777	The second function, C<rouse_wait>, waits for the callback to be called
665	(by calling C<schedule> to go to sleep) and returns the arguments	778	(by calling C<schedule> to go to sleep) and returns the arguments
666	originally passed to the callback.	779	originally passed to the callback.
…		…
681	you can roll your own, using C<schedule>:	794	you can roll your own, using C<schedule>:
682		795
683	sub wait_for_child($) {	796	sub wait_for_child($) {
684	my ($pid) = @_;	797	my ($pid) = @_;
685		798
686	# store the current coroutine in $current,	799	# store the current coro in $current,
687	# and provide result variables for the closure passed to ->child	800	# and provide result variables for the closure passed to ->child
688	my $current = $Coro::current;	801	my $current = $Coro::current;
689	my ($done, $rstatus);	802	my ($done, $rstatus);
690		803
691	# pass a closure to ->child	804	# pass a closure to ->child
…		…
707		820
708	=item fork with pthread backend	821	=item fork with pthread backend
709		822
710	When Coro is compiled using the pthread backend (which isn't recommended	823	When Coro is compiled using the pthread backend (which isn't recommended
711	but required on many BSDs as their libcs are completely broken), then	824	but required on many BSDs as their libcs are completely broken), then
712	coroutines will not survive a fork. There is no known workaround except to	825	coro will not survive a fork. There is no known workaround except to
713	fix your libc and use a saner backend.	826	fix your libc and use a saner backend.
714		827
715	=item perl process emulation ("threads")	828	=item perl process emulation ("threads")
716		829
717	This module is not perl-pseudo-thread-safe. You should only ever use this	830	This module is not perl-pseudo-thread-safe. You should only ever use this
…		…
719	future to allow per-thread schedulers, but Coro::State does not yet allow	832	future to allow per-thread schedulers, but Coro::State does not yet allow
720	this). I recommend disabling thread support and using processes, as having	833	this). I recommend disabling thread support and using processes, as having
721	the windows process emulation enabled under unix roughly halves perl	834	the windows process emulation enabled under unix roughly halves perl
722	performance, even when not used.	835	performance, even when not used.
723		836
724	=item coroutine switching not signal safe	837	=item coro switching is not signal safe
725		838
726	You must not switch to another coroutine from within a signal handler	839	You must not switch to another coro from within a signal handler (only
727	(only relevant with %SIG - most event libraries provide safe signals).	840	relevant with %SIG - most event libraries provide safe signals), I<unless>
		841	you are sure you are not interrupting a Coro function.
728		842
729	That means you I<MUST NOT> call any function that might "block" the	843	That means you I<MUST NOT> call any function that might "block" the
730	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or	844	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
731	anything that calls those. Everything else, including calling C<ready>,	845	anything that calls those. Everything else, including calling C<ready>,
732	works.	846	works.
733		847
734	=back	848	=back
735		849
		850
		851	=head1 WINDOWS PROCESS EMULATION
		852
		853	A great many people seem to be confused about ithreads (for example, Chip
		854	Salzenberg called me unintelligent, incapable, stupid and gullible,
		855	while in the same mail making rather confused statements about perl
		856	ithreads (for example, that memory or files would be shared), showing his
		857	lack of understanding of this area - if it is hard to understand for Chip,
		858	it is probably not obvious to everybody).
		859
		860	What follows is an ultra-condensed version of my talk about threads in
		861	scripting languages given onthe perl workshop 2009:
		862
		863	The so-called "ithreads" were originally implemented for two reasons:
		864	first, to (badly) emulate unix processes on native win32 perls, and
		865	secondly, to replace the older, real thread model ("5.005-threads").
		866
		867	It does that by using threads instead of OS processes. The difference
		868	between processes and threads is that threads share memory (and other
		869	state, such as files) between threads within a single process, while
		870	processes do not share anything (at least not semantically). That
		871	means that modifications done by one thread are seen by others, while
		872	modifications by one process are not seen by other processes.
		873
		874	The "ithreads" work exactly like that: when creating a new ithreads
		875	process, all state is copied (memory is copied physically, files and code
		876	is copied logically). Afterwards, it isolates all modifications. On UNIX,
		877	the same behaviour can be achieved by using operating system processes,
		878	except that UNIX typically uses hardware built into the system to do this
		879	efficiently, while the windows process emulation emulates this hardware in
		880	software (rather efficiently, but of course it is still much slower than
		881	dedicated hardware).
		882
		883	As mentioned before, loading code, modifying code, modifying data
		884	structures and so on is only visible in the ithreads process doing the
		885	modification, not in other ithread processes within the same OS process.
		886
		887	This is why "ithreads" do not implement threads for perl at all, only
		888	processes. What makes it so bad is that on non-windows platforms, you can
		889	actually take advantage of custom hardware for this purpose (as evidenced
		890	by the forks module, which gives you the (i-) threads API, just much
		891	faster).
		892
		893	Sharing data is in the i-threads model is done by transfering data
		894	structures between threads using copying semantics, which is very slow -
		895	shared data simply does not exist. Benchmarks using i-threads which are
		896	communication-intensive show extremely bad behaviour with i-threads (in
		897	fact, so bad that Coro, which cannot take direct advantage of multiple
		898	CPUs, is often orders of magnitude faster because it shares data using
		899	real threads, refer to my talk for details).
		900
		901	As summary, i-threads use threads to implement processes, while
		902	the compatible forks module uses processes to emulate, uhm,
		903	processes. I-threads slow down every perl program when enabled, and
		904	outside of windows, serve no (or little) practical purpose, but
		905	disadvantages every single-threaded Perl program.
		906
		907	This is the reason that I try to avoid the name "ithreads", as it is
		908	misleading as it implies that it implements some kind of thread model for
		909	perl, and prefer the name "windows process emulation", which describes the
		910	actual use and behaviour of it much better.
736		911
737	=head1 SEE ALSO	912	=head1 SEE ALSO
738		913
739	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.	914	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
740		915

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Revision 1.244 by root, Sat Dec 13 22:08:13 2008 UTC vs.
Revision 1.274 by root, Sat Dec 12 01:30:26 2009 UTC