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

Comparing Coro/Coro.pm (file contents):
Revision 1.103 by root, Thu Jan 4 20:14:19 2007 UTC vs.
Revision 1.268 by root, Thu Oct 1 23:16:27 2009 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	Coro - coroutine process abstraction	3	Coro - the only real threads in perl
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use Coro;	7	use Coro;
8		8
9	async {	9	async {
10	# some asynchronous thread of execution	10	# some asynchronous thread of execution
		11	print "2\n";
		12	cede; # yield back to main
		13	print "4\n";
11	};	14	};
12		15	print "1\n";
13	# alternatively create an async coroutine like this:	16	cede; # yield to coro
14		17	print "3\n";
15	sub some_func : Coro {	18	cede; # and again
16	# some more async code	19
17	}	20	# use locking
18		21	use Coro::Semaphore;
19	cede;	22	my $lock = new Coro::Semaphore;
		23	my $locked;
		24
		25	$lock->down;
		26	$locked = 1;
		27	$lock->up;
20		28
21	=head1 DESCRIPTION	29	=head1 DESCRIPTION
22		30
23	This module collection manages coroutines. Coroutines are similar	31	For a tutorial-style introduction, please read the L<Coro::Intro>
24	to threads but don't run in parallel at the same time even on SMP	32	manpage. This manpage mainly contains reference information.
25	machines. The specific flavor of coroutine use din this module also
26	guarentees you that it will not switch between coroutines unless
27	necessary, at easily-identified points in your program, so locking and
28	parallel access are rarely an issue, making coroutine programming much
29	safer than threads programming.
30		33
31	(Perl, however, does not natively support real threads but instead does a	34	This module collection manages continuations in general, most often in
32	very slow and memory-intensive emulation of processes using threads. This	35	the form of cooperative threads (also called coros, or simply "coro"
33	is a performance win on Windows machines, and a loss everywhere else).	36	in the documentation). They are similar to kernel threads but don't (in
		37	general) run in parallel at the same time even on SMP machines. The
		38	specific flavor of thread offered by this module also guarantees you that
		39	it will not switch between threads unless necessary, at easily-identified
		40	points in your program, so locking and parallel access are rarely an
		41	issue, making thread programming much safer and easier than using other
		42	thread models.
34		43
		44	Unlike the so-called "Perl threads" (which are not actually real threads
		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
		47	a full shared address space, which makes communication between threads
		48	very easy. And Coro's threads are fast, too: disabling the Windows
		49	process emulation code in your perl and using Coro can easily result in
		50	a two to four times speed increase for your programs. A parallel matrix
		51	multiplication benchmark runs over 300 times faster on a single core than
		52	perl's pseudo-threads on a quad core using all four cores.
		53
		54	Coro achieves that by supporting multiple running interpreters that share
		55	data, which is especially useful to code pseudo-parallel processes and
		56	for event-based programming, such as multiple HTTP-GET requests running
		57	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
		58	into an event-based environment.
		59
35	In this module, coroutines are defined as "callchain + lexical variables +	60	In this module, a thread is defined as "callchain + lexical variables +
36	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,	61	some package variables + C stack), that is, a thread has its own callchain,
37	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
38	variables.	63	variables (see L<Coro::State> for more configuration and background info).
		64
		65	See also the C<SEE ALSO> section at the end of this document - the Coro
		66	module family is quite large.
39		67
40	=cut	68	=cut
41		69
42	package Coro;	70	package Coro;
43		71
44	use strict;	72	use common::sense;
45	no warnings "uninitialized";	73
		74	use Carp ();
		75
		76	use Guard ();
46		77
47	use Coro::State;	78	use Coro::State;
48		79
49	use base qw(Coro::State Exporter);	80	use base qw(Coro::State Exporter);
50		81
51	our $idle; # idle handler	82	our $idle; # idle handler
52	our $main; # main coroutine	83	our $main; # main coro
53	our $current; # current coroutine	84	our $current; # current coro
54		85
55	our $VERSION = '3.3';	86	our $VERSION = 5.17;
56		87
57	our @EXPORT = qw(async cede schedule terminate current unblock_sub);	88	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
58	our %EXPORT_TAGS = (	89	our %EXPORT_TAGS = (
59	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	90	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
60	);	91	);
61	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	92	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
62		93
63	{	94	=head1 GLOBAL VARIABLES
64	my @async;
65	my $init;
66
67	# this way of handling attributes simply is NOT scalable ;()
68	sub import {
69	no strict 'refs';
70
71	Coro->export_to_level (1, @_);
72
73	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
74	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
75	my ($package, $ref) = (shift, shift);
76	my @attrs;
77	for (@_) {
78	if ($_ eq "Coro") {
79	push @async, $ref;
80	unless ($init++) {
81	eval q{
82	sub INIT {
83	&async(pop @async) while @async;
84	}
85	};
86	}
87	} else {
88	push @attrs, $_;
89	}
90	}
91	return $old ? $old->($package, $ref, @attrs) : @attrs;
92	};
93	}
94
95	}
96		95
97	=over 4	96	=over 4
98		97
99	=item $main	98	=item $Coro::main
100		99
101	This coroutine represents the main program.	100	This variable stores the Coro object that represents the main
		101	program. While you cna C<ready> it and do most other things you can do to
		102	coro, it is mainly useful to compare again C<$Coro::current>, to see
		103	whether you are running in the main program or not.
102		104
103	=cut	105	=cut
104		106
105	$main = new Coro;	107	# $main is now being initialised by Coro::State
106		108
107	=item $current (or as function: current)	109	=item $Coro::current
108		110
109	The current coroutine (the last coroutine switched to). The initial value	111	The Coro object representing the current coro (the last
		112	coro that the Coro scheduler switched to). The initial value is
110	is C<$main> (of course).	113	C<$Coro::main> (of course).
111		114
112	This variable is B<strictly> I<read-only>. It is provided for performance	115	This variable is B<strictly> I<read-only>. You can take copies of the
113	reasons. If performance is not essentiel you are encouraged to use the	116	value stored in it and use it as any other Coro object, but you must
114	C<Coro::current> function instead.	117	not otherwise modify the variable itself.
115		118
116	=cut	119	=cut
117		120
118	# maybe some other module used Coro::Specific before...
119	$main->{specific} = $current->{specific}
120	if $current;
121
122	_set_current $main;
123
124	sub current() { $current }	121	sub current() { $current } # [DEPRECATED]
125		122
126	=item $idle	123	=item $Coro::idle
127		124
		125	This variable is mainly useful to integrate Coro into event loops. It is
		126	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
		127	pretty low-level functionality.
		128
		129	This variable stores either a Coro object or a callback.
		130
128	A callback that is called whenever the scheduler finds no ready coroutines	131	If it is a callback, the it is called whenever the scheduler finds no
129	to run. The default implementation prints "FATAL: deadlock detected" and	132	ready coros to run. The default implementation prints "FATAL:
130	exits, because the program has no other way to continue.	133	deadlock detected" and exits, because the program has no other way to
		134	continue.
131		135
		136	If it is a coro object, then this object will be readied (without
		137	invoking any ready hooks, however) when the scheduler finds no other ready
		138	coros to run.
		139
132	This hook is overwritten by modules such as C<Coro::Timer> and	140	This hook is overwritten by modules such as C<Coro::EV> and
133	C<Coro::Event> to wait on an external event that hopefully wake up a	141	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
134	coroutine so the scheduler can run it.	142	coro so the scheduler can run it.
		143
		144	Note that the callback I<must not>, under any circumstances, block
		145	the current coro. Normally, this is achieved by having an "idle
		146	coro" that calls the event loop and then blocks again, and then
		147	readying that coro in the idle handler, or by simply placing the idle
		148	coro in this variable.
		149
		150	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
		151	technique.
135		152
136	Please note that if your callback recursively invokes perl (e.g. for event	153	Please note that if your callback recursively invokes perl (e.g. for event
137	handlers), then it must be prepared to be called recursively.	154	handlers), then it must be prepared to be called recursively itself.
138		155
139	=cut	156	=cut
140		157
141	$idle = sub {	158	$idle = sub {
142	require Carp;	159	warn "oi\n";#d#
143	Carp::croak ("FATAL: deadlock detected");	160	Carp::confess ("FATAL: deadlock detected");
144	};	161	};
145		162
146	sub _cancel {
147	my ($self) = @_;
148
149	# free coroutine data and mark as destructed
150	$self->_destroy
151	or return;
152
153	# call all destruction callbacks
154	$_->(@{$self->{status}})
155	for @{(delete $self->{destroy_cb}) \|\| []};
156	}
157
158	# this coroutine is necessary because a coroutine	163	# this coro is necessary because a coro
159	# cannot destroy itself.	164	# cannot destroy itself.
160	my @destroy;	165	our @destroy;
161	my $manager;	166	our $manager;
162		167
163	$manager = new Coro sub {	168	$manager = new Coro sub {
164	while () {	169	while () {
165	(shift @destroy)->_cancel	170	Coro::State::cancel shift @destroy
166	while @destroy;	171	while @destroy;
167		172
168	&schedule;	173	&schedule;
169	}	174	}
170	};	175	};
171		176	$manager->{desc} = "[coro manager]";
172	$manager->prio (PRIO_MAX);	177	$manager->prio (PRIO_MAX);
173		178
174	# static methods. not really.
175
176	=back	179	=back
177		180
178	=head2 STATIC METHODS	181	=head1 SIMPLE CORO CREATION
179
180	Static methods are actually functions that operate on the current coroutine only.
181		182
182	=over 4	183	=over 4
183		184
184	=item async { ... } [@args...]	185	=item async { ... } [@args...]
185		186
186	Create a new asynchronous coroutine and return it's coroutine object	187	Create a new coro and return its Coro object (usually
187	(usually unused). When the sub returns the new coroutine is automatically	188	unused). The coro will be put into the ready queue, so
		189	it will start running automatically on the next scheduler run.
		190
		191	The first argument is a codeblock/closure that should be executed in the
		192	coro. When it returns argument returns the coro is automatically
188	terminated.	193	terminated.
189		194
190	Calling C<exit> in a coroutine will not work correctly, so do not do that.	195	The remaining arguments are passed as arguments to the closure.
191		196
192	When the coroutine dies, the program will exit, just as in the main	197	See the C<Coro::State::new> constructor for info about the coro
193	program.	198	environment in which coro are executed.
194		199
		200	Calling C<exit> in a coro will do the same as calling exit outside
		201	the coro. Likewise, when the coro dies, the program will exit,
		202	just as it would in the main program.
		203
		204	If you do not want that, you can provide a default C<die> handler, or
		205	simply avoid dieing (by use of C<eval>).
		206
195	# create a new coroutine that just prints its arguments	207	Example: Create a new coro that just prints its arguments.
		208
196	async {	209	async {
197	print "@_\n";	210	print "@_\n";
198	} 1,2,3,4;	211	} 1,2,3,4;
199		212
200	=cut	213	=item async_pool { ... } [@args...]
201		214
202	sub async(&@) {	215	Similar to C<async>, but uses a coro pool, so you should not call
203	my $pid = new Coro @_;	216	terminate or join on it (although you are allowed to), and you get a
204	$pid->ready;	217	coro that might have executed other code already (which can be good
205	$pid	218	or bad :).
		219
		220	On the plus side, this function is about twice as fast as creating (and
		221	destroying) a completely new coro, so if you need a lot of generic
		222	coros in quick successsion, use C<async_pool>, not C<async>.
		223
		224	The code block is executed in an C<eval> context and a warning will be
		225	issued in case of an exception instead of terminating the program, as
		226	C<async> does. As the coro is being reused, stuff like C<on_destroy>
		227	will not work in the expected way, unless you call terminate or cancel,
		228	which somehow defeats the purpose of pooling (but is fine in the
		229	exceptional case).
		230
		231	The priority will be reset to C<0> after each run, tracing will be
		232	disabled, the description will be reset and the default output filehandle
		233	gets restored, so you can change all these. Otherwise the coro will
		234	be re-used "as-is": most notably if you change other per-coro global
		235	stuff such as C<$/> you I<must needs> revert that change, which is most
		236	simply done by using local as in: C<< local $/ >>.
		237
		238	The idle pool size is limited to C<8> idle coros (this can be
		239	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
		240	coros as required.
		241
		242	If you are concerned about pooled coros growing a lot because a
		243	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		244	{ terminate }> once per second or so to slowly replenish the pool. In
		245	addition to that, when the stacks used by a handler grows larger than 32kb
		246	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
		247
		248	=cut
		249
		250	our $POOL_SIZE = 8;
		251	our $POOL_RSS = 32 * 1024;
		252	our @async_pool;
		253
		254	sub pool_handler {
		255	while () {
		256	eval {
		257	&{&_pool_handler} while 1;
		258	};
		259
		260	warn $@ if $@;
		261	}
206	}	262	}
207		263
		264	=back
		265
		266	=head1 STATIC METHODS
		267
		268	Static methods are actually functions that implicitly operate on the
		269	current coro.
		270
		271	=over 4
		272
208	=item schedule	273	=item schedule
209		274
210	Calls the scheduler. Please note that the current coroutine will not be put	275	Calls the scheduler. The scheduler will find the next coro that is
		276	to be run from the ready queue and switches to it. The next coro
		277	to be run is simply the one with the highest priority that is longest
		278	in its ready queue. If there is no coro ready, it will clal the
		279	C<$Coro::idle> hook.
		280
		281	Please note that the current coro will I<not> be put into the ready
211	into the ready queue, so calling this function usually means you will	282	queue, so calling this function usually means you will never be called
212	never be called again unless something else (e.g. an event handler) calls	283	again unless something else (e.g. an event handler) calls C<< ->ready >>,
213	ready.	284	thus waking you up.
214		285
215	The canonical way to wait on external events is this:	286	This makes C<schedule> I<the> generic method to use to block the current
		287	coro and wait for events: first you remember the current coro in
		288	a variable, then arrange for some callback of yours to call C<< ->ready
		289	>> on that once some event happens, and last you call C<schedule> to put
		290	yourself to sleep. Note that a lot of things can wake your coro up,
		291	so you need to check whether the event indeed happened, e.g. by storing the
		292	status in a variable.
216		293
		294	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
		295
		296	=item cede
		297
		298	"Cede" to other coros. This function puts the current coro into
		299	the ready queue and calls C<schedule>, which has the effect of giving
		300	up the current "timeslice" to other coros of the same or higher
		301	priority. Once your coro gets its turn again it will automatically be
		302	resumed.
		303
		304	This function is often called C<yield> in other languages.
		305
		306	=item Coro::cede_notself
		307
		308	Works like cede, but is not exported by default and will cede to I<any>
		309	coro, regardless of priority. This is useful sometimes to ensure
		310	progress is made.
		311
		312	=item terminate [arg...]
		313
		314	Terminates the current coro with the given status values (see L<cancel>).
		315
		316	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
		317
		318	These function install enter and leave winders in the current scope. The
		319	enter block will be executed when on_enter is called and whenever the
		320	current coro is re-entered by the scheduler, while the leave block is
		321	executed whenever the current coro is blocked by the scheduler, and
		322	also when the containing scope is exited (by whatever means, be it exit,
		323	die, last etc.).
		324
		325	I<Neither invoking the scheduler, nor exceptions, are allowed within those
		326	BLOCKs>. That means: do not even think about calling C<die> without an
		327	eval, and do not even think of entering the scheduler in any way.
		328
		329	Since both BLOCKs are tied to the current scope, they will automatically
		330	be removed when the current scope exits.
		331
		332	These functions implement the same concept as C<dynamic-wind> in scheme
		333	does, and are useful when you want to localise some resource to a specific
		334	coro.
		335
		336	They slow down thread switching considerably for coros that use them
		337	(about 40% for a BLOCK with a single assignment, so thread switching is
		338	still reasonably fast if the handlers are fast).
		339
		340	These functions are best understood by an example: The following function
		341	will change the current timezone to "Antarctica/South_Pole", which
		342	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
		343	which remember/change the current timezone and restore the previous
		344	value, respectively, the timezone is only changed for the coro that
		345	installed those handlers.
		346
		347	use POSIX qw(tzset);
		348
		349	async {
		350	my $old_tz; # store outside TZ value here
		351
		352	Coro::on_enter {
		353	$old_tz = $ENV{TZ}; # remember the old value
		354
		355	$ENV{TZ} = "Antarctica/South_Pole";
		356	tzset; # enable new value
		357	};
		358
		359	Coro::on_leave {
		360	$ENV{TZ} = $old_tz;
		361	tzset; # restore old value
		362	};
		363
		364	# at this place, the timezone is Antarctica/South_Pole,
		365	# without disturbing the TZ of any other coro.
		366	};
		367
		368	This can be used to localise about any resource (locale, uid, current
		369	working directory etc.) to a block, despite the existance of other
		370	coros.
		371
		372	Another interesting example implements time-sliced multitasking using
		373	interval timers (this could obviously be optimised, but does the job):
		374
		375	# "timeslice" the given block
		376	sub timeslice(&) {
		377	use Time::HiRes ();
		378
		379	Coro::on_enter {
		380	# on entering the thread, we set an VTALRM handler to cede
		381	$SIG{VTALRM} = sub { cede };
		382	# and then start the interval timer
		383	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
		384	};
		385	Coro::on_leave {
		386	# on leaving the thread, we stop the interval timer again
		387	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
		388	};
		389
		390	&{+shift};
		391	}
		392
		393	# use like this:
		394	timeslice {
		395	# The following is an endless loop that would normally
		396	# monopolise the process. Since it runs in a timesliced
		397	# environment, it will regularly cede to other threads.
		398	while () { }
		399	};
		400
		401
		402	=item killall
		403
		404	Kills/terminates/cancels all coros except the currently running one.
		405
		406	Note that while this will try to free some of the main interpreter
		407	resources if the calling coro isn't the main coro, but one
		408	cannot free all of them, so if a coro that is not the main coro
		409	calls this function, there will be some one-time resource leak.
		410
		411	=cut
		412
		413	sub killall {
		414	for (Coro::State::list) {
		415	$_->cancel
		416	if $_ != $current && UNIVERSAL::isa $_, "Coro";
217	{	417	}
218	# remember current coroutine	418	}
		419
		420	=back
		421
		422	=head1 CORO OBJECT METHODS
		423
		424	These are the methods you can call on coro objects (or to create
		425	them).
		426
		427	=over 4
		428
		429	=item new Coro \&sub [, @args...]
		430
		431	Create a new coro and return it. When the sub returns, the coro
		432	automatically terminates as if C<terminate> with the returned values were
		433	called. To make the coro run you must first put it into the ready
		434	queue by calling the ready method.
		435
		436	See C<async> and C<Coro::State::new> for additional info about the
		437	coro environment.
		438
		439	=cut
		440
		441	sub _coro_run {
		442	terminate &{+shift};
		443	}
		444
		445	=item $success = $coro->ready
		446
		447	Put the given coro into the end of its ready queue (there is one
		448	queue for each priority) and return true. If the coro is already in
		449	the ready queue, do nothing and return false.
		450
		451	This ensures that the scheduler will resume this coro automatically
		452	once all the coro of higher priority and all coro of the same
		453	priority that were put into the ready queue earlier have been resumed.
		454
		455	=item $coro->suspend
		456
		457	Suspends the specified coro. A suspended coro works just like any other
		458	coro, except that the scheduler will not select a suspended coro for
		459	execution.
		460
		461	Suspending a coro can be useful when you want to keep the coro from
		462	running, but you don't want to destroy it, or when you want to temporarily
		463	freeze a coro (e.g. for debugging) to resume it later.
		464
		465	A scenario for the former would be to suspend all (other) coros after a
		466	fork and keep them alive, so their destructors aren't called, but new
		467	coros can be created.
		468
		469	=item $coro->resume
		470
		471	If the specified coro was suspended, it will be resumed. Note that when
		472	the coro was in the ready queue when it was suspended, it might have been
		473	unreadied by the scheduler, so an activation might have been lost.
		474
		475	To avoid this, it is best to put a suspended coro into the ready queue
		476	unconditionally, as every synchronisation mechanism must protect itself
		477	against spurious wakeups, and the one in the Coro family certainly do
		478	that.
		479
		480	=item $is_ready = $coro->is_ready
		481
		482	Returns true iff the Coro object is in the ready queue. Unless the Coro
		483	object gets destroyed, it will eventually be scheduled by the scheduler.
		484
		485	=item $is_running = $coro->is_running
		486
		487	Returns true iff the Coro object is currently running. Only one Coro object
		488	can ever be in the running state (but it currently is possible to have
		489	multiple running Coro::States).
		490
		491	=item $is_suspended = $coro->is_suspended
		492
		493	Returns true iff this Coro object has been suspended. Suspended Coros will
		494	not ever be scheduled.
		495
		496	=item $coro->cancel (arg...)
		497
		498	Terminates the given Coro and makes it return the given arguments as
		499	status (default: the empty list). Never returns if the Coro is the
		500	current Coro.
		501
		502	=cut
		503
		504	sub cancel {
		505	my $self = shift;
		506
		507	if ($current == $self) {
		508	terminate @_;
		509	} else {
		510	$self->{_status} = [@_];
		511	Coro::State::cancel $self;
		512	}
		513	}
		514
		515	=item $coro->schedule_to
		516
		517	Puts the current coro to sleep (like C<Coro::schedule>), but instead
		518	of continuing with the next coro from the ready queue, always switch to
		519	the given coro object (regardless of priority etc.). The readyness
		520	state of that coro isn't changed.
		521
		522	This is an advanced method for special cases - I'd love to hear about any
		523	uses for this one.
		524
		525	=item $coro->cede_to
		526
		527	Like C<schedule_to>, but puts the current coro into the ready
		528	queue. This has the effect of temporarily switching to the given
		529	coro, and continuing some time later.
		530
		531	This is an advanced method for special cases - I'd love to hear about any
		532	uses for this one.
		533
		534	=item $coro->throw ([$scalar])
		535
		536	If C<$throw> is specified and defined, it will be thrown as an exception
		537	inside the coro at the next convenient point in time. Otherwise
		538	clears the exception object.
		539
		540	Coro will check for the exception each time a schedule-like-function
		541	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		542	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		543	detect this case and return early in case an exception is pending.
		544
		545	The exception object will be thrown "as is" with the specified scalar in
		546	C<$@>, i.e. if it is a string, no line number or newline will be appended
		547	(unlike with C<die>).
		548
		549	This can be used as a softer means than C<cancel> to ask a coro to
		550	end itself, although there is no guarantee that the exception will lead to
		551	termination, and if the exception isn't caught it might well end the whole
		552	program.
		553
		554	You might also think of C<throw> as being the moral equivalent of
		555	C<kill>ing a coro with a signal (in this case, a scalar).
		556
		557	=item $coro->join
		558
		559	Wait until the coro terminates and return any values given to the
		560	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		561	from multiple coro, and all will be resumed and given the status
		562	return once the C<$coro> terminates.
		563
		564	=cut
		565
		566	sub join {
		567	my $self = shift;
		568
		569	unless ($self->{_status}) {
219	my $current = $Coro::current;	570	my $current = $current;
220		571
221	# register a hypothetical event handler	572	push @{$self->{_on_destroy}}, sub {
222	on_event_invoke sub {
223	# wake up sleeping coroutine
224	$current->ready;	573	$current->ready;
225	undef $current;	574	undef $current;
226	};	575	};
227		576
228	# call schedule until event occured.
229	# in case we are woken up for other reasons
230	# (current still defined), loop.
231	Coro::schedule while $current;
232	}
233
234	=item cede
235
236	"Cede" to other coroutines. This function puts the current coroutine into the
237	ready queue and calls C<schedule>, which has the effect of giving up the
238	current "timeslice" to other coroutines of the same or higher priority.
239
240	=item Coro::cede_notself
241
242	Works like cede, but is not exported by default and will cede to any
243	coroutine, regardless of priority, once.
244
245	=item terminate [arg...]
246
247	Terminates the current coroutine with the given status values (see L<cancel>).
248
249	=cut
250
251	sub terminate {
252	$current->cancel (@_);
253	}
254
255	=back
256
257	# dynamic methods
258
259	=head2 COROUTINE METHODS
260
261	These are the methods you can call on coroutine objects.
262
263	=over 4
264
265	=item new Coro \&sub [, @args...]
266
267	Create a new coroutine and return it. When the sub returns the coroutine
268	automatically terminates as if C<terminate> with the returned values were
269	called. To make the coroutine run you must first put it into the ready queue
270	by calling the ready method.
271
272	Calling C<exit> in a coroutine will not work correctly, so do not do that.
273
274	=cut
275
276	sub _run_coro {
277	terminate &{+shift};
278	}
279
280	sub new {
281	my $class = shift;
282
283	$class->SUPER::new (\&_run_coro, @_)
284	}
285
286	=item $success = $coroutine->ready
287
288	Put the given coroutine into the ready queue (according to it's priority)
289	and return true. If the coroutine is already in the ready queue, do nothing
290	and return false.
291
292	=item $is_ready = $coroutine->is_ready
293
294	Return wether the coroutine is currently the ready queue or not,
295
296	=item $coroutine->cancel (arg...)
297
298	Terminates the given coroutine and makes it return the given arguments as
299	status (default: the empty list). Never returns if the coroutine is the
300	current coroutine.
301
302	=cut
303
304	sub cancel {
305	my $self = shift;
306	$self->{status} = [@_];
307
308	if ($current == $self) {
309	push @destroy, $self;
310	$manager->ready;
311	&schedule while 1;
312	} else {
313	$self->_cancel;
314	}
315	}
316
317	=item $coroutine->join
318
319	Wait until the coroutine terminates and return any values given to the
320	C<terminate> or C<cancel> functions. C<join> can be called multiple times
321	from multiple coroutine.
322
323	=cut
324
325	sub join {
326	my $self = shift;
327
328	unless ($self->{status}) {
329	my $current = $current;
330
331	push @{$self->{destroy_cb}}, sub {
332	$current->ready;
333	undef $current;
334	};
335
336	&schedule while $current;	577	&schedule while $current;
337	}	578	}
338		579
339	wantarray ? @{$self->{status}} : $self->{status}[0];	580	wantarray ? @{$self->{_status}} : $self->{_status}[0];
340	}	581	}
341		582
342	=item $coroutine->on_destroy (\&cb)	583	=item $coro->on_destroy (\&cb)
343		584
344	Registers a callback that is called when this coroutine gets destroyed,	585	Registers a callback that is called when this coro gets destroyed,
345	but before it is joined. The callback gets passed the terminate arguments,	586	but before it is joined. The callback gets passed the terminate arguments,
346	if any.	587	if any, and I<must not> die, under any circumstances.
347		588
348	=cut	589	=cut
349		590
350	sub on_destroy {	591	sub on_destroy {
351	my ($self, $cb) = @_;	592	my ($self, $cb) = @_;
352		593
353	push @{ $self->{destroy_cb} }, $cb;	594	push @{ $self->{_on_destroy} }, $cb;
354	}	595	}
355		596
356	=item $oldprio = $coroutine->prio ($newprio)	597	=item $oldprio = $coro->prio ($newprio)
357		598
358	Sets (or gets, if the argument is missing) the priority of the	599	Sets (or gets, if the argument is missing) the priority of the
359	coroutine. Higher priority coroutines get run before lower priority	600	coro. Higher priority coro get run before lower priority
360	coroutines. Priorities are small signed integers (currently -4 .. +3),	601	coro. Priorities are small signed integers (currently -4 .. +3),
361	that you can refer to using PRIO_xxx constants (use the import tag :prio	602	that you can refer to using PRIO_xxx constants (use the import tag :prio
362	to get then):	603	to get then):
363		604
364	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	605	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
365	3 > 1 > 0 > -1 > -3 > -4	606	3 > 1 > 0 > -1 > -3 > -4
366		607
367	# set priority to HIGH	608	# set priority to HIGH
368	current->prio(PRIO_HIGH);	609	current->prio (PRIO_HIGH);
369		610
370	The idle coroutine ($Coro::idle) always has a lower priority than any	611	The idle coro ($Coro::idle) always has a lower priority than any
371	existing coroutine.	612	existing coro.
372		613
373	Changing the priority of the current coroutine will take effect immediately,	614	Changing the priority of the current coro will take effect immediately,
374	but changing the priority of coroutines in the ready queue (but not	615	but changing the priority of coro in the ready queue (but not
375	running) will only take effect after the next schedule (of that	616	running) will only take effect after the next schedule (of that
376	coroutine). This is a bug that will be fixed in some future version.	617	coro). This is a bug that will be fixed in some future version.
377		618
378	=item $newprio = $coroutine->nice ($change)	619	=item $newprio = $coro->nice ($change)
379		620
380	Similar to C<prio>, but subtract the given value from the priority (i.e.	621	Similar to C<prio>, but subtract the given value from the priority (i.e.
381	higher values mean lower priority, just as in unix).	622	higher values mean lower priority, just as in unix).
382		623
383	=item $olddesc = $coroutine->desc ($newdesc)	624	=item $olddesc = $coro->desc ($newdesc)
384		625
385	Sets (or gets in case the argument is missing) the description for this	626	Sets (or gets in case the argument is missing) the description for this
386	coroutine. This is just a free-form string you can associate with a coroutine.	627	coro. This is just a free-form string you can associate with a
		628	coro.
		629
		630	This method simply sets the C<< $coro->{desc} >> member to the given
		631	string. You can modify this member directly if you wish.
387		632
388	=cut	633	=cut
389		634
390	sub desc {	635	sub desc {
391	my $old = $_[0]{desc};	636	my $old = $_[0]{desc};
392	$_[0]{desc} = $_[1] if @_ > 1;	637	$_[0]{desc} = $_[1] if @_ > 1;
393	$old;	638	$old;
394	}	639	}
395		640
		641	sub transfer {
		642	require Carp;
		643	Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
		644	}
		645
396	=back	646	=back
397		647
398	=head2 GLOBAL FUNCTIONS	648	=head1 GLOBAL FUNCTIONS
399		649
400	=over 4	650	=over 4
401		651
402	=item Coro::nready	652	=item Coro::nready
403		653
404	Returns the number of coroutines that are currently in the ready state,	654	Returns the number of coro that are currently in the ready state,
405	i.e. that can be swicthed to. The value C<0> means that the only runnable	655	i.e. that can be switched to by calling C<schedule> directory or
		656	indirectly. The value C<0> means that the only runnable coro is the
406	coroutine is the currently running one, so C<cede> would have no effect,	657	currently running one, so C<cede> would have no effect, and C<schedule>
407	and C<schedule> would cause a deadlock unless there is an idle handler	658	would cause a deadlock unless there is an idle handler that wakes up some
408	that wakes up some coroutines.	659	coro.
409		660
410	=item my $guard = Coro::guard { ... }	661	=item my $guard = Coro::guard { ... }
411		662
412	This creates and returns a guard object. Nothing happens until the objetc	663	This function still exists, but is deprecated. Please use the
413	gets destroyed, in which case the codeblock given as argument will be	664	C<Guard::guard> function instead.
414	executed. This is useful to free locks or other resources in case of a
415	runtime error or when the coroutine gets canceled, as in both cases the
416	guard block will be executed. The guard object supports only one method,
417	C<< ->cancel >>, which will keep the codeblock from being executed.
418		665
419	Example: set some flag and clear it again when the coroutine gets canceled
420	or the function returns:
421
422	sub do_something {
423	my $guard = Coro::guard { $busy = 0 };
424	$busy = 1;
425
426	# do something that requires $busy to be true
427	}
428
429	=cut	666	=cut
430		667
431	sub guard(&) {	668	BEGIN { *guard = \&Guard::guard }
432	bless \(my $cb = $_[0]), "Coro::guard"
433	}
434
435	sub Coro::guard::cancel {
436	${$_[0]} = sub { };
437	}
438
439	sub Coro::guard::DESTROY {
440	${$_[0]}->();
441	}
442
443		669
444	=item unblock_sub { ... }	670	=item unblock_sub { ... }
445		671
446	This utility function takes a BLOCK or code reference and "unblocks" it,	672	This utility function takes a BLOCK or code reference and "unblocks" it,
447	returning the new coderef. This means that the new coderef will return	673	returning a new coderef. Unblocking means that calling the new coderef
448	immediately without blocking, returning nothing, while the original code	674	will return immediately without blocking, returning nothing, while the
449	ref will be called (with parameters) from within its own coroutine.	675	original code ref will be called (with parameters) from within another
		676	coro.
450		677
451	The reason this fucntion exists is that many event libraries (such as the	678	The reason this function exists is that many event libraries (such as the
452	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form	679	venerable L<Event\|Event> module) are not thread-safe (a weaker form
453	of thread-safety). This means you must not block within event callbacks,	680	of reentrancy). This means you must not block within event callbacks,
454	otherwise you might suffer from crashes or worse.	681	otherwise you might suffer from crashes or worse. The only event library
		682	currently known that is safe to use without C<unblock_sub> is L<EV>.
455		683
456	This function allows your callbacks to block by executing them in another	684	This function allows your callbacks to block by executing them in another
457	coroutine where it is safe to block. One example where blocking is handy	685	coro where it is safe to block. One example where blocking is handy
458	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	686	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
459	disk.	687	disk, for example.
460		688
461	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	689	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
462	creating event callbacks that want to block.	690	creating event callbacks that want to block.
463		691
464	=cut	692	If your handler does not plan to block (e.g. simply sends a message to
		693	another coro, or puts some other coro into the ready queue), there is
		694	no reason to use C<unblock_sub>.
465		695
466	our @unblock_pool;	696	Note that you also need to use C<unblock_sub> for any other callbacks that
		697	are indirectly executed by any C-based event loop. For example, when you
		698	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		699	provides callbacks that are the result of some event callback, then you
		700	must not block either, or use C<unblock_sub>.
		701
		702	=cut
		703
467	our @unblock_queue;	704	our @unblock_queue;
468	our $UNBLOCK_POOL_SIZE = 2;
469		705
470	sub unblock_handler_ {	706	# we create a special coro because we want to cede,
471	while () {	707	# to reduce pressure on the coro pool (because most callbacks
472	my ($cb, @arg) = @{ delete $Coro::current->{arg} };	708	# return immediately and can be reused) and because we cannot cede
473	$cb->(@arg);	709	# inside an event callback.
474
475	last if @unblock_pool >= $UNBLOCK_POOL_SIZE;
476	push @unblock_pool, $Coro::current;
477	schedule;
478	}
479	}
480
481	our $unblock_scheduler = async {	710	our $unblock_scheduler = new Coro sub {
482	while () {	711	while () {
483	while (my $cb = pop @unblock_queue) {	712	while (my $cb = pop @unblock_queue) {
484	my $handler = (pop @unblock_pool or new Coro \&unblock_handler_);	713	&async_pool (@$cb);
485	$handler->{arg} = $cb;	714
486	$handler->ready;	715	# for short-lived callbacks, this reduces pressure on the coro pool
		716	# as the chance is very high that the async_poll coro will be back
		717	# in the idle state when cede returns
487	cede;	718	cede;
488	}	719	}
489		720	schedule; # sleep well
490	schedule;
491	}	721	}
492	};	722	};
		723	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
493		724
494	sub unblock_sub(&) {	725	sub unblock_sub(&) {
495	my $cb = shift;	726	my $cb = shift;
496		727
497	sub {	728	sub {
498	push @unblock_queue, [$cb, @_];	729	unshift @unblock_queue, [$cb, @_];
499	$unblock_scheduler->ready;	730	$unblock_scheduler->ready;
500	}	731	}
501	}	732	}
502		733
		734	=item $cb = Coro::rouse_cb
		735
		736	Create and return a "rouse callback". That's a code reference that,
		737	when called, will remember a copy of its arguments and notify the owner
		738	coro of the callback.
		739
		740	See the next function.
		741
		742	=item @args = Coro::rouse_wait [$cb]
		743
		744	Wait for the specified rouse callback (or the last one that was created in
		745	this coro).
		746
		747	As soon as the callback is invoked (or when the callback was invoked
		748	before C<rouse_wait>), it will return the arguments originally passed to
		749	the rouse callback. In scalar context, that means you get the I<last>
		750	argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
		751	statement at the end.
		752
		753	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		754
503	=back	755	=back
504		756
505	=cut	757	=cut
506		758
507	1;	759	1;
508		760
		761	=head1 HOW TO WAIT FOR A CALLBACK
		762
		763	It is very common for a coro to wait for some callback to be
		764	called. This occurs naturally when you use coro in an otherwise
		765	event-based program, or when you use event-based libraries.
		766
		767	These typically register a callback for some event, and call that callback
		768	when the event occured. In a coro, however, you typically want to
		769	just wait for the event, simplyifying things.
		770
		771	For example C<< AnyEvent->child >> registers a callback to be called when
		772	a specific child has exited:
		773
		774	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		775
		776	But from within a coro, you often just want to write this:
		777
		778	my $status = wait_for_child $pid;
		779
		780	Coro offers two functions specifically designed to make this easy,
		781	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		782
		783	The first function, C<rouse_cb>, generates and returns a callback that,
		784	when invoked, will save its arguments and notify the coro that
		785	created the callback.
		786
		787	The second function, C<rouse_wait>, waits for the callback to be called
		788	(by calling C<schedule> to go to sleep) and returns the arguments
		789	originally passed to the callback.
		790
		791	Using these functions, it becomes easy to write the C<wait_for_child>
		792	function mentioned above:
		793
		794	sub wait_for_child($) {
		795	my ($pid) = @_;
		796
		797	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		798
		799	my ($rpid, $rstatus) = Coro::rouse_wait;
		800	$rstatus
		801	}
		802
		803	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		804	you can roll your own, using C<schedule>:
		805
		806	sub wait_for_child($) {
		807	my ($pid) = @_;
		808
		809	# store the current coro in $current,
		810	# and provide result variables for the closure passed to ->child
		811	my $current = $Coro::current;
		812	my ($done, $rstatus);
		813
		814	# pass a closure to ->child
		815	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		816	$rstatus = $_[1]; # remember rstatus
		817	$done = 1; # mark $rstatus as valud
		818	});
		819
		820	# wait until the closure has been called
		821	schedule while !$done;
		822
		823	$rstatus
		824	}
		825
		826
509	=head1 BUGS/LIMITATIONS	827	=head1 BUGS/LIMITATIONS
510		828
511	- you must make very sure that no coro is still active on global	829	=over 4
512	destruction. very bad things might happen otherwise (usually segfaults).
513		830
		831	=item fork with pthread backend
		832
		833	When Coro is compiled using the pthread backend (which isn't recommended
		834	but required on many BSDs as their libcs are completely broken), then
		835	coro will not survive a fork. There is no known workaround except to
		836	fix your libc and use a saner backend.
		837
		838	=item perl process emulation ("threads")
		839
514	- this module is not thread-safe. You should only ever use this module	840	This module is not perl-pseudo-thread-safe. You should only ever use this
515	from the same thread (this requirement might be losened in the future	841	module from the first thread (this requirement might be removed in the
516	to allow per-thread schedulers, but Coro::State does not yet allow	842	future to allow per-thread schedulers, but Coro::State does not yet allow
517	this).	843	this). I recommend disabling thread support and using processes, as having
		844	the windows process emulation enabled under unix roughly halves perl
		845	performance, even when not used.
		846
		847	=item coro switching is not signal safe
		848
		849	You must not switch to another coro from within a signal handler
		850	(only relevant with %SIG - most event libraries provide safe signals).
		851
		852	That means you I<MUST NOT> call any function that might "block" the
		853	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		854	anything that calls those. Everything else, including calling C<ready>,
		855	works.
		856
		857	=back
		858
		859
		860	=head1 WINDOWS PROCESS EMULATION
		861
		862	A great many people seem to be confused about ithreads (for example, Chip
		863	Salzenberg called me unintelligent, incapable, stupid and gullible,
		864	while in the same mail making rather confused statements about perl
		865	ithreads (for example, that memory or files would be shared), showing his
		866	lack of understanding of this area - if it is hard to understand for Chip,
		867	it is probably not obvious to everybody).
		868
		869	What follows is an ultra-condensed version of my talk about threads in
		870	scripting languages given onthe perl workshop 2009:
		871
		872	The so-called "ithreads" were originally implemented for two reasons:
		873	first, to (badly) emulate unix processes on native win32 perls, and
		874	secondly, to replace the older, real thread model ("5.005-threads").
		875
		876	It does that by using threads instead of OS processes. The difference
		877	between processes and threads is that threads share memory (and other
		878	state, such as files) between threads within a single process, while
		879	processes do not share anything (at least not semantically). That
		880	means that modifications done by one thread are seen by others, while
		881	modifications by one process are not seen by other processes.
		882
		883	The "ithreads" work exactly like that: when creating a new ithreads
		884	process, all state is copied (memory is copied physically, files and code
		885	is copied logically). Afterwards, it isolates all modifications. On UNIX,
		886	the same behaviour can be achieved by using operating system processes,
		887	except that UNIX typically uses hardware built into the system to do this
		888	efficiently, while the windows process emulation emulates this hardware in
		889	software (rather efficiently, but of course it is still much slower than
		890	dedicated hardware).
		891
		892	As mentioned before, loading code, modifying code, modifying data
		893	structures and so on is only visible in the ithreads process doing the
		894	modification, not in other ithread processes within the same OS process.
		895
		896	This is why "ithreads" do not implement threads for perl at all, only
		897	processes. What makes it so bad is that on non-windows platforms, you can
		898	actually take advantage of custom hardware for this purpose (as evidenced
		899	by the forks module, which gives you the (i-) threads API, just much
		900	faster).
		901
		902	Sharing data is in the i-threads model is done by transfering data
		903	structures between threads using copying semantics, which is very slow -
		904	shared data simply does not exist. Benchmarks using i-threads which are
		905	communication-intensive show extremely bad behaviour with i-threads (in
		906	fact, so bad that Coro, which cannot take direct advantage of multiple
		907	CPUs, is often orders of magnitude faster because it shares data using
		908	real threads, refer to my talk for details).
		909
		910	As summary, i-threads use threads to implement processes, while
		911	the compatible forks module uses processes to emulate, uhm,
		912	processes. I-threads slow down every perl program when enabled, and
		913	outside of windows, serve no (or little) practical purpose, but
		914	disadvantages every single-threaded Perl program.
		915
		916	This is the reason that I try to avoid the name "ithreads", as it is
		917	misleading as it implies that it implements some kind of thread model for
		918	perl, and prefer the name "windows process emulation", which describes the
		919	actual use and behaviour of it much better.
518		920
519	=head1 SEE ALSO	921	=head1 SEE ALSO
520		922
		923	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		924
		925	Debugging: L<Coro::Debug>.
		926
521	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.	927	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
522		928
523	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.	929	Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
		930	L<Coro::SemaphoreSet>, L<Coro::RWLock>.
524		931
525	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.	932	I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
526		933
527	Embedding: L<Coro:MakeMaker>	934	Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
		935	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
		936	L<Coro::Select>.
		937
		938	XS API: L<Coro::MakeMaker>.
		939
		940	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
528		941
529	=head1 AUTHOR	942	=head1 AUTHOR
530		943
531	Marc Lehmann <schmorp@schmorp.de>	944	Marc Lehmann <schmorp@schmorp.de>
532	http://home.schmorp.de/	945	http://home.schmorp.de/

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Revision 1.103 by root, Thu Jan 4 20:14:19 2007 UTC vs.
Revision 1.268 by root, Thu Oct 1 23:16:27 2009 UTC