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

Comparing Coro/Coro.pm (file contents):
Revision 1.5 by root, Tue Jul 10 01:43:21 2001 UTC vs.
Revision 1.148 by root, Fri Oct 5 20:11:25 2007 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	Coro - create and manage coroutines	3	Coro - coroutine process abstraction
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use Coro;	7	use Coro;
8		8
9	$new = new Coro sub {	9	async {
10	print "in coroutine, switching back\n";	10	# some asynchronous thread of execution
11	$Coro::main->resume;
12	print "in coroutine again, switching back\n";
13	$Coro::main->resume;
14	};	11	};
15		12
16	print "in main, switching to coroutine\n";	13	# alternatively create an async coroutine like this:
17	$new->resume;	14
18	print "back in main, switch to coroutine again\n";	15	sub some_func : Coro {
19	$new->resume;	16	# some more async code
20	print "back in main\n";	17	}
		18
		19	cede;
21		20
22	=head1 DESCRIPTION	21	=head1 DESCRIPTION
23		22
24	This module implements coroutines. Coroutines, similar to continuations,	23	This module collection manages coroutines. Coroutines are similar
25	allow you to run more than one "thread of execution" in parallel. Unlike	24	to threads but don't run in parallel at the same time even on SMP
26	threads this, only voluntary switching is used so locking problems are	25	machines. The specific flavor of coroutine used in this module also
27	greatly reduced.	26	guarantees 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.
28		30
29	Although this is the "main" module of the Coro family it provides only	31	(Perl, however, does not natively support real threads but instead does a
30	low-level functionality. See L<Coro::Process> and related modules for a	32	very slow and memory-intensive emulation of processes using threads. This
31	more useful process abstraction including scheduling.	33	is a performance win on Windows machines, and a loss everywhere else).
		34
		35	In this module, coroutines are defined as "callchain + lexical variables +
		36	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
		37	its own set of lexicals and its own set of perls most important global
		38	variables.
		39
		40	=cut
		41
		42	package Coro;
		43
		44	use strict;
		45	no warnings "uninitialized";
		46
		47	use Coro::State;
		48
		49	use base qw(Coro::State Exporter);
		50
		51	our $idle; # idle handler
		52	our $main; # main coroutine
		53	our $current; # current coroutine
		54
		55	our $VERSION = '4.01';
		56
		57	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
		58	our %EXPORT_TAGS = (
		59	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		60	);
		61	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
		62
		63	{
		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	}
32		96
33	=over 4	97	=over 4
34		98
35	=cut
36
37	package Coro;
38
39	BEGIN {
40	$VERSION = 0.03;
41
42	require XSLoader;
43	XSLoader::load Coro, $VERSION;
44	}
45
46	=item $main	99	=item $main
47		100
48	This coroutine represents the main program.	101	This coroutine represents the main program.
49		102
50	=item $current	103	=cut
51		104
		105	$main = new Coro;
		106
		107	=item $current (or as function: current)
		108
52	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).	109	The current coroutine (the last coroutine switched to). The initial value
		110	is C<$main> (of course).
53		111
54	=cut	112	This variable is B<strictly> I<read-only>. It is provided for performance
		113	reasons. If performance is not essential you are encouraged to use the
		114	C<Coro::current> function instead.
55		115
56	$main = $current = _newprocess {	116	=cut
57	# never being called	117
		118	$main->{desc} = "[main::]";
		119
		120	# maybe some other module used Coro::Specific before...
		121	$main->{_specific} = $current->{_specific}
		122	if $current;
		123
		124	_set_current $main;
		125
		126	sub current() { $current }
		127
		128	=item $idle
		129
		130	A callback that is called whenever the scheduler finds no ready coroutines
		131	to run. The default implementation prints "FATAL: deadlock detected" and
		132	exits, because the program has no other way to continue.
		133
		134	This hook is overwritten by modules such as C<Coro::Timer> and
		135	C<Coro::Event> to wait on an external event that hopefully wake up a
		136	coroutine so the scheduler can run it.
		137
		138	Please note that if your callback recursively invokes perl (e.g. for event
		139	handlers), then it must be prepared to be called recursively.
		140
		141	=cut
		142
		143	$idle = sub {
		144	require Carp;
		145	Carp::croak ("FATAL: deadlock detected");
58	};	146	};
59		147
60	=item $error, $error_msg, $error_coro	148	sub _cancel {
		149	my ($self) = @_;
61		150
62	This coroutine will be called on fatal errors. C<$error_msg> and	151	# free coroutine data and mark as destructed
63	C<$error_coro> return the error message and the error-causing coroutine,	152	$self->_destroy
64	respectively.	153	or return;
65		154
66	=cut	155	# call all destruction callbacks
		156	$_->(@{$self->{_status}})
		157	for @{(delete $self->{_on_destroy}) \|\| []};
		158	}
67		159
68	$error_msg =	160	# this coroutine is necessary because a coroutine
69	$error_coro = undef;	161	# cannot destroy itself.
		162	my @destroy;
		163	my $manager;
70		164
71	$error = _newprocess {	165	$manager = new Coro sub {
72	print STDERR "FATAL: $error_msg\nprogram aborted\n";	166	while () {
73	exit 250;	167	(shift @destroy)->_cancel
		168	while @destroy;
		169
		170	&schedule;
		171	}
74	};	172	};
		173	$manager->desc ("[coro manager]");
		174	$manager->prio (PRIO_MAX);
75		175
76	=item $coro = new $coderef [, @args]	176	# static methods. not really.
77		177
78	Create a new coroutine and return it. The first C<resume> call to this	178	=back
79	coroutine will start execution at the given coderef. If it returns it
80	should return a coroutine to switch to. If, after returning, the coroutine
81	is C<resume>d again it starts execution again at the givne coderef.
82		179
		180	=head2 STATIC METHODS
		181
		182	Static methods are actually functions that operate on the current coroutine only.
		183
		184	=over 4
		185
		186	=item async { ... } [@args...]
		187
		188	Create a new asynchronous coroutine and return it's coroutine object
		189	(usually unused). When the sub returns the new coroutine is automatically
		190	terminated.
		191
		192	See the C<Coro::State::new> constructor for info about the coroutine
		193	environment.
		194
		195	Calling C<exit> in a coroutine will do the same as calling exit outside
		196	the coroutine. Likewise, when the coroutine dies, the program will exit,
		197	just as it would in the main program.
		198
		199	# create a new coroutine that just prints its arguments
		200	async {
		201	print "@_\n";
		202	} 1,2,3,4;
		203
83	=cut	204	=cut
		205
		206	sub async(&@) {
		207	my $coro = new Coro @_;
		208	$coro->ready;
		209	$coro
		210	}
		211
		212	=item async_pool { ... } [@args...]
		213
		214	Similar to C<async>, but uses a coroutine pool, so you should not call
		215	terminate or join (although you are allowed to), and you get a coroutine
		216	that might have executed other code already (which can be good or bad :).
		217
		218	Also, the block is executed in an C<eval> context and a warning will be
		219	issued in case of an exception instead of terminating the program, as
		220	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		221	will not work in the expected way, unless you call terminate or cancel,
		222	which somehow defeats the purpose of pooling.
		223
		224	The priority will be reset to C<0> after each job, tracing will be
		225	disabled, the description will be reset and the default output filehandle
		226	gets restored, so you can change alkl these. Otherwise the coroutine will
		227	be re-used "as-is": most notably if you change other per-coroutine global
		228	stuff such as C<$/> you need to revert that change, which is most simply
		229	done by using local as in C< local $/ >.
		230
		231	The pool size is limited to 8 idle coroutines (this can be adjusted by
		232	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
		233	required.
		234
		235	If you are concerned about pooled coroutines growing a lot because a
		236	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		237	{ terminate }> once per second or so to slowly replenish the pool. In
		238	addition to that, when the stacks used by a handler grows larger than 16kb
		239	(adjustable with $Coro::POOL_RSS) it will also exit.
		240
		241	=cut
		242
		243	our $POOL_SIZE = 8;
		244	our $POOL_RSS = 16 * 1024;
		245	our @async_pool;
		246
		247	sub pool_handler {
		248	my $cb;
		249
		250	while () {
		251	eval {
		252	while () {
		253	_pool_1 $cb;
		254	&$cb;
		255	_pool_2 $cb;
		256	&schedule;
		257	}
		258	};
		259
		260	last if $@ eq "\3terminate\2\n";
		261	warn $@ if $@;
		262	}
		263	}
		264
		265	sub async_pool(&@) {
		266	# this is also inlined into the unlock_scheduler
		267	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		268
		269	$coro->{_invoke} = [@_];
		270	$coro->ready;
		271
		272	$coro
		273	}
		274
		275	=item schedule
		276
		277	Calls the scheduler. Please note that the current coroutine will not be put
		278	into the ready queue, so calling this function usually means you will
		279	never be called again unless something else (e.g. an event handler) calls
		280	ready.
		281
		282	The canonical way to wait on external events is this:
		283
		284	{
		285	# remember current coroutine
		286	my $current = $Coro::current;
		287
		288	# register a hypothetical event handler
		289	on_event_invoke sub {
		290	# wake up sleeping coroutine
		291	$current->ready;
		292	undef $current;
		293	};
		294
		295	# call schedule until event occurred.
		296	# in case we are woken up for other reasons
		297	# (current still defined), loop.
		298	Coro::schedule while $current;
		299	}
		300
		301	=item cede
		302
		303	"Cede" to other coroutines. This function puts the current coroutine into the
		304	ready queue and calls C<schedule>, which has the effect of giving up the
		305	current "timeslice" to other coroutines of the same or higher priority.
		306
		307	Returns true if at least one coroutine switch has happened.
		308
		309	=item Coro::cede_notself
		310
		311	Works like cede, but is not exported by default and will cede to any
		312	coroutine, regardless of priority, once.
		313
		314	Returns true if at least one coroutine switch has happened.
		315
		316	=item terminate [arg...]
		317
		318	Terminates the current coroutine with the given status values (see L<cancel>).
		319
		320	=item killall
		321
		322	Kills/terminates/cancels all coroutines except the currently running
		323	one. This is useful after a fork, either in the child or the parent, as
		324	usually only one of them should inherit the running coroutines.
		325
		326	=cut
		327
		328	sub terminate {
		329	$current->cancel (@_);
		330	}
		331
		332	sub killall {
		333	for (Coro::State::list) {
		334	$_->cancel
		335	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		336	}
		337	}
		338
		339	=back
		340
		341	# dynamic methods
		342
		343	=head2 COROUTINE METHODS
		344
		345	These are the methods you can call on coroutine objects.
		346
		347	=over 4
		348
		349	=item new Coro \&sub [, @args...]
		350
		351	Create a new coroutine and return it. When the sub returns the coroutine
		352	automatically terminates as if C<terminate> with the returned values were
		353	called. To make the coroutine run you must first put it into the ready queue
		354	by calling the ready method.
		355
		356	See C<async> and C<Coro::State::new> for additional info about the
		357	coroutine environment.
		358
		359	=cut
		360
		361	sub _run_coro {
		362	terminate &{+shift};
		363	}
84		364
85	sub new {	365	sub new {
86	my $class = $_[0];	366	my $class = shift;
87	my $proc = $_[1];	367
88	bless _newprocess {	368	$class->SUPER::new (\&_run_coro, @_)
89	do {	369	}
90	eval { &$proc->resume };	370
91	if ($@) {	371	=item $success = $coroutine->ready
92	($error_msg, $error_coro) = ($@, $current);	372
93	$error->resume;	373	Put the given coroutine into the ready queue (according to it's priority)
		374	and return true. If the coroutine is already in the ready queue, do nothing
		375	and return false.
		376
		377	=item $is_ready = $coroutine->is_ready
		378
		379	Return wether the coroutine is currently the ready queue or not,
		380
		381	=item $coroutine->cancel (arg...)
		382
		383	Terminates the given coroutine and makes it return the given arguments as
		384	status (default: the empty list). Never returns if the coroutine is the
		385	current coroutine.
		386
		387	=cut
		388
		389	sub cancel {
		390	my $self = shift;
		391	$self->{_status} = [@_];
		392
		393	if ($current == $self) {
		394	push @destroy, $self;
		395	$manager->ready;
		396	&schedule while 1;
		397	} else {
		398	$self->_cancel;
		399	}
		400	}
		401
		402	=item $coroutine->join
		403
		404	Wait until the coroutine terminates and return any values given to the
		405	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		406	from multiple coroutines.
		407
		408	=cut
		409
		410	sub join {
		411	my $self = shift;
		412
		413	unless ($self->{_status}) {
		414	my $current = $current;
		415
		416	push @{$self->{_on_destroy}}, sub {
		417	$current->ready;
		418	undef $current;
		419	};
		420
		421	&schedule while $current;
		422	}
		423
		424	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		425	}
		426
		427	=item $coroutine->on_destroy (\&cb)
		428
		429	Registers a callback that is called when this coroutine gets destroyed,
		430	but before it is joined. The callback gets passed the terminate arguments,
		431	if any.
		432
		433	=cut
		434
		435	sub on_destroy {
		436	my ($self, $cb) = @_;
		437
		438	push @{ $self->{_on_destroy} }, $cb;
		439	}
		440
		441	=item $oldprio = $coroutine->prio ($newprio)
		442
		443	Sets (or gets, if the argument is missing) the priority of the
		444	coroutine. Higher priority coroutines get run before lower priority
		445	coroutines. Priorities are small signed integers (currently -4 .. +3),
		446	that you can refer to using PRIO_xxx constants (use the import tag :prio
		447	to get then):
		448
		449	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		450	3 > 1 > 0 > -1 > -3 > -4
		451
		452	# set priority to HIGH
		453	current->prio(PRIO_HIGH);
		454
		455	The idle coroutine ($Coro::idle) always has a lower priority than any
		456	existing coroutine.
		457
		458	Changing the priority of the current coroutine will take effect immediately,
		459	but changing the priority of coroutines in the ready queue (but not
		460	running) will only take effect after the next schedule (of that
		461	coroutine). This is a bug that will be fixed in some future version.
		462
		463	=item $newprio = $coroutine->nice ($change)
		464
		465	Similar to C<prio>, but subtract the given value from the priority (i.e.
		466	higher values mean lower priority, just as in unix).
		467
		468	=item $olddesc = $coroutine->desc ($newdesc)
		469
		470	Sets (or gets in case the argument is missing) the description for this
		471	coroutine. This is just a free-form string you can associate with a coroutine.
		472
		473	This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
		474	can modify this member directly if you wish.
		475
		476	=cut
		477
		478	sub desc {
		479	my $old = $_[0]{desc};
		480	$_[0]{desc} = $_[1] if @_ > 1;
		481	$old;
		482	}
		483
		484	=back
		485
		486	=head2 GLOBAL FUNCTIONS
		487
		488	=over 4
		489
		490	=item Coro::nready
		491
		492	Returns the number of coroutines that are currently in the ready state,
		493	i.e. that can be switched to. The value C<0> means that the only runnable
		494	coroutine is the currently running one, so C<cede> would have no effect,
		495	and C<schedule> would cause a deadlock unless there is an idle handler
		496	that wakes up some coroutines.
		497
		498	=item my $guard = Coro::guard { ... }
		499
		500	This creates and returns a guard object. Nothing happens until the object
		501	gets destroyed, in which case the codeblock given as argument will be
		502	executed. This is useful to free locks or other resources in case of a
		503	runtime error or when the coroutine gets canceled, as in both cases the
		504	guard block will be executed. The guard object supports only one method,
		505	C<< ->cancel >>, which will keep the codeblock from being executed.
		506
		507	Example: set some flag and clear it again when the coroutine gets canceled
		508	or the function returns:
		509
		510	sub do_something {
		511	my $guard = Coro::guard { $busy = 0 };
		512	$busy = 1;
		513
		514	# do something that requires $busy to be true
		515	}
		516
		517	=cut
		518
		519	sub guard(&) {
		520	bless \(my $cb = $_[0]), "Coro::guard"
		521	}
		522
		523	sub Coro::guard::cancel {
		524	${$_[0]} = sub { };
		525	}
		526
		527	sub Coro::guard::DESTROY {
		528	${$_[0]}->();
		529	}
		530
		531
		532	=item unblock_sub { ... }
		533
		534	This utility function takes a BLOCK or code reference and "unblocks" it,
		535	returning the new coderef. This means that the new coderef will return
		536	immediately without blocking, returning nothing, while the original code
		537	ref will be called (with parameters) from within its own coroutine.
		538
		539	The reason this function exists is that many event libraries (such as the
		540	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		541	of thread-safety). This means you must not block within event callbacks,
		542	otherwise you might suffer from crashes or worse.
		543
		544	This function allows your callbacks to block by executing them in another
		545	coroutine where it is safe to block. One example where blocking is handy
		546	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		547	disk.
		548
		549	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		550	creating event callbacks that want to block.
		551
		552	=cut
		553
		554	our @unblock_queue;
		555
		556	# we create a special coro because we want to cede,
		557	# to reduce pressure on the coro pool (because most callbacks
		558	# return immediately and can be reused) and because we cannot cede
		559	# inside an event callback.
		560	our $unblock_scheduler = new Coro sub {
		561	while () {
		562	while (my $cb = pop @unblock_queue) {
		563	# this is an inlined copy of async_pool
		564	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		565
		566	$coro->{_invoke} = $cb;
		567	$coro->ready;
		568	cede; # for short-lived callbacks, this reduces pressure on the coro pool
94	}	569	}
95	} while (1);	570	schedule; # sleep well
96	}, $class;	571	}
97	}	572	};
		573	$unblock_scheduler->desc ("[unblock_sub scheduler]");
98		574
99	=item $coro->resume	575	sub unblock_sub(&) {
		576	my $cb = shift;
100		577
101	Resume execution at the given coroutine.	578	sub {
102		579	unshift @unblock_queue, [$cb, @_];
103	=cut	580	$unblock_scheduler->ready;
104		581	}
105	my $prev;
106
107	# I call the _transfer function from a pelr function
108	# because that way perl saves all important things on
109	# the stack.
110	sub resume {
111	$prev = $current; $current = $_[0];
112	_transfer($prev, $current);
113	}	582	}
		583
		584	=back
		585
		586	=cut
114		587
115	1;	588	1;
116		589
117	=back	590	=head1 BUGS/LIMITATIONS
118		591
119	=head1 BUGS	592	- you must make very sure that no coro is still active on global
		593	destruction. very bad things might happen otherwise (usually segfaults).
120		594
121	This module has not yet been extensively tested.	595	- this module is not thread-safe. You should only ever use this module
		596	from the same thread (this requirement might be loosened in the future
		597	to allow per-thread schedulers, but Coro::State does not yet allow
		598	this).
122		599
123	=head1 SEE ALSO	600	=head1 SEE ALSO
124		601
125	L<Coro::Process>, L<Coro::Signal>.	602	Support/Utility: L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
		603
		604	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		605
		606	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
		607
		608	Embedding: L<Coro:MakeMaker>
126		609
127	=head1 AUTHOR	610	=head1 AUTHOR
128		611
129	Marc Lehmann <pcg@goof.com>	612	Marc Lehmann <schmorp@schmorp.de>
130	http://www.goof.com/pcg/marc/	613	http://home.schmorp.de/
131		614
132	=cut	615	=cut
133		616

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Comparing Coro/Coro.pm (file contents): Revision 1.5 by root, Tue Jul 10 01:43:21 2001 UTC vs. Revision 1.148 by root, Fri Oct 5 20:11:25 2007 UTC

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Comparing Coro/Coro.pm (file contents):
Revision 1.5 by root, Tue Jul 10 01:43:21 2001 UTC vs.
Revision 1.148 by root, Fri Oct 5 20:11:25 2007 UTC