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

Comparing Coro/Coro.pm (file contents):
Revision 1.6 by root, Tue Jul 10 21:19:47 2001 UTC vs.
Revision 1.137 by root, Wed Sep 26 19:26:48 2007 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	Coro - create and manage simple 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	$new->transfer($main);
12	print "in coroutine again, switching back\n";
13	$new->transfer($main);
14	};	11	};
15		12
16	$main = new Coro;	13	# alternatively create an async coroutine like this:
17		14
18	print "in main, switching to coroutine\n";	15	sub some_func : Coro {
19	$main->transfer($new);	16	# some more async code
20	print "back in main, switch to coroutine again\n";	17	}
21	$main->transfer($new);	18
22	print "back in main\n";	19	cede;
23		20
24	=head1 DESCRIPTION	21	=head1 DESCRIPTION
25		22
26	This module implements coroutines. Coroutines, similar to continuations,	23	This module collection manages coroutines. Coroutines are similar
27	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
28	threads this, only voluntary switching is used so locking problems are	25	machines. The specific flavor of coroutine used in this module also
29	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.
30		30
31	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
32	low-level functionality. See L<Coro::Process> and related modules for a	32	very slow and memory-intensive emulation of processes using threads. This
33	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 $VERSION = '3.7';
		56
		57	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
		58	our %EXPORT_TAGS = (
		59	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		60	);
		61	our @EXPORT_OK = (@{$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	}
34		96
35	=over 4	97	=over 4
36		98
37	=cut	99	=item $main
38		100
39	package Coro;	101	This coroutine represents the main program.
40		102
41	BEGIN {	103	=cut
42	$VERSION = 0.03;
43		104
		105	$main = new Coro;
		106
		107	=item $current (or as function: current)
		108
		109	The current coroutine (the last coroutine switched to). The initial value
		110	is C<$main> (of course).
		111
		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.
		115
		116	=cut
		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 {
44	require XSLoader;	144	require Carp;
45	XSLoader::load Coro, $VERSION;	145	Carp::croak ("FATAL: deadlock detected");
46	}	146	};
47		147
48	=item $coro = new [$coderef [, @args]]	148	sub _cancel {
		149	my ($self) = @_;
49		150
50	Create a new coroutine and return it. The first C<transfer> call to this	151	# free coroutine data and mark as destructed
51	coroutine will start execution at the given coderef. If, the subroutine	152	$self->_destroy
52	returns it will be executed again.	153	or return;
53		154
54	If the coderef is omitted this function will create a new "empty"	155	# call all destruction callbacks
55	coroutine, i.e. a coroutine that cannot be transfered to but can be used	156	$_->(@{$self->{status}})
56	to save the current coroutine in.	157	for @{(delete $self->{destroy_cb}) \|\| []};
		158	}
57		159
		160	sub _do_trace {
		161	$current->{_trace_cb}->();
		162	}
		163
		164	# this coroutine is necessary because a coroutine
		165	# cannot destroy itself.
		166	my @destroy;
		167	my $manager;
		168
		169	$manager = new Coro sub {
		170	while () {
		171	(shift @destroy)->_cancel
		172	while @destroy;
		173
		174	&schedule;
		175	}
		176	};
		177	$manager->desc ("[coro manager]");
		178	$manager->prio (PRIO_MAX);
		179
		180	# static methods. not really.
		181
		182	=back
		183
		184	=head2 STATIC METHODS
		185
		186	Static methods are actually functions that operate on the current coroutine only.
		187
		188	=over 4
		189
		190	=item async { ... } [@args...]
		191
		192	Create a new asynchronous coroutine and return it's coroutine object
		193	(usually unused). When the sub returns the new coroutine is automatically
		194	terminated.
		195
		196	Calling C<exit> in a coroutine will do the same as calling exit outside
		197	the coroutine. Likewise, when the coroutine dies, the program will exit,
		198	just as it would in the main program.
		199
		200	# create a new coroutine that just prints its arguments
		201	async {
		202	print "@_\n";
		203	} 1,2,3,4;
		204
58	=cut	205	=cut
		206
		207	sub async(&@) {
		208	my $coro = new Coro @_;
		209	$coro->ready;
		210	$coro
		211	}
		212
		213	=item async_pool { ... } [@args...]
		214
		215	Similar to C<async>, but uses a coroutine pool, so you should not call
		216	terminate or join (although you are allowed to), and you get a coroutine
		217	that might have executed other code already (which can be good or bad :).
		218
		219	Also, the block is executed in an C<eval> context and a warning will be
		220	issued in case of an exception instead of terminating the program, as
		221	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		222	will not work in the expected way, unless you call terminate or cancel,
		223	which somehow defeats the purpose of pooling.
		224
		225	The priority will be reset to C<0> after each job, otherwise the coroutine
		226	will be re-used "as-is".
		227
		228	The pool size is limited to 8 idle coroutines (this can be adjusted by
		229	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
		230	required.
		231
		232	If you are concerned about pooled coroutines growing a lot because a
		233	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		234	{ terminate }> once per second or so to slowly replenish the pool. In
		235	addition to that, when the stacks used by a handler grows larger than 16kb
		236	(adjustable with $Coro::POOL_RSS) it will also exit.
		237
		238	=cut
		239
		240	our $POOL_SIZE = 8;
		241	our $POOL_RSS = 16 * 1024;
		242	our @async_pool;
		243
		244	sub pool_handler {
		245	my $cb;
		246
		247	while () {
		248	eval {
		249	while () {
		250	_pool_1 $cb;
		251	&$cb;
		252	_pool_2 $cb;
		253	&schedule;
		254	}
		255	};
		256
		257	last if $@ eq "\3terminate\2\n";
		258	warn $@ if $@;
		259	}
		260	}
		261
		262	sub async_pool(&@) {
		263	# this is also inlined into the unlock_scheduler
		264	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		265
		266	$coro->{_invoke} = [@_];
		267	$coro->ready;
		268
		269	$coro
		270	}
		271
		272	=item schedule
		273
		274	Calls the scheduler. Please note that the current coroutine will not be put
		275	into the ready queue, so calling this function usually means you will
		276	never be called again unless something else (e.g. an event handler) calls
		277	ready.
		278
		279	The canonical way to wait on external events is this:
		280
		281	{
		282	# remember current coroutine
		283	my $current = $Coro::current;
		284
		285	# register a hypothetical event handler
		286	on_event_invoke sub {
		287	# wake up sleeping coroutine
		288	$current->ready;
		289	undef $current;
		290	};
		291
		292	# call schedule until event occurred.
		293	# in case we are woken up for other reasons
		294	# (current still defined), loop.
		295	Coro::schedule while $current;
		296	}
		297
		298	=item cede
		299
		300	"Cede" to other coroutines. This function puts the current coroutine into the
		301	ready queue and calls C<schedule>, which has the effect of giving up the
		302	current "timeslice" to other coroutines of the same or higher priority.
		303
		304	Returns true if at least one coroutine switch has happened.
		305
		306	=item Coro::cede_notself
		307
		308	Works like cede, but is not exported by default and will cede to any
		309	coroutine, regardless of priority, once.
		310
		311	Returns true if at least one coroutine switch has happened.
		312
		313	=item terminate [arg...]
		314
		315	Terminates the current coroutine with the given status values (see L<cancel>).
		316
		317	=cut
		318
		319	sub terminate {
		320	$current->cancel (@_);
		321	}
		322
		323	=back
		324
		325	# dynamic methods
		326
		327	=head2 COROUTINE METHODS
		328
		329	These are the methods you can call on coroutine objects.
		330
		331	=over 4
		332
		333	=item new Coro \&sub [, @args...]
		334
		335	Create a new coroutine and return it. When the sub returns the coroutine
		336	automatically terminates as if C<terminate> with the returned values were
		337	called. To make the coroutine run you must first put it into the ready queue
		338	by calling the ready method.
		339
		340	See C<async> for additional discussion.
		341
		342	=cut
		343
		344	sub _run_coro {
		345	terminate &{+shift};
		346	}
59		347
60	sub new {	348	sub new {
61	my $class = $_[0];	349	my $class = shift;
62	my $proc = $_[1] \|\| sub { die "tried to transfer to an empty coroutine" };	350
63	bless _newprocess {	351	$class->SUPER::new (\&_run_coro, @_)
64	do {	352	}
65	eval { &$proc };	353
66	if ($@) {	354	=item $success = $coroutine->ready
67	$error_msg = $@;	355
68	$error_coro = _newprocess { };	356	Put the given coroutine into the ready queue (according to it's priority)
69	&transfer($error_coro, $error);	357	and return true. If the coroutine is already in the ready queue, do nothing
		358	and return false.
		359
		360	=item $is_ready = $coroutine->is_ready
		361
		362	Return wether the coroutine is currently the ready queue or not,
		363
		364	=item $coroutine->cancel (arg...)
		365
		366	Terminates the given coroutine and makes it return the given arguments as
		367	status (default: the empty list). Never returns if the coroutine is the
		368	current coroutine.
		369
		370	=cut
		371
		372	sub cancel {
		373	my $self = shift;
		374	$self->{status} = [@_];
		375
		376	if ($current == $self) {
		377	push @destroy, $self;
		378	$manager->ready;
		379	&schedule while 1;
		380	} else {
		381	$self->_cancel;
		382	}
		383	}
		384
		385	=item $coroutine->join
		386
		387	Wait until the coroutine terminates and return any values given to the
		388	C<terminate> or C<cancel> functions. C<join> can be called multiple times
		389	from multiple coroutine.
		390
		391	=cut
		392
		393	sub join {
		394	my $self = shift;
		395
		396	unless ($self->{status}) {
		397	my $current = $current;
		398
		399	push @{$self->{destroy_cb}}, sub {
		400	$current->ready;
		401	undef $current;
		402	};
		403
		404	&schedule while $current;
		405	}
		406
		407	wantarray ? @{$self->{status}} : $self->{status}[0];
		408	}
		409
		410	=item $coroutine->on_destroy (\&cb)
		411
		412	Registers a callback that is called when this coroutine gets destroyed,
		413	but before it is joined. The callback gets passed the terminate arguments,
		414	if any.
		415
		416	=cut
		417
		418	sub on_destroy {
		419	my ($self, $cb) = @_;
		420
		421	push @{ $self->{destroy_cb} }, $cb;
		422	}
		423
		424	=item $oldprio = $coroutine->prio ($newprio)
		425
		426	Sets (or gets, if the argument is missing) the priority of the
		427	coroutine. Higher priority coroutines get run before lower priority
		428	coroutines. Priorities are small signed integers (currently -4 .. +3),
		429	that you can refer to using PRIO_xxx constants (use the import tag :prio
		430	to get then):
		431
		432	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		433	3 > 1 > 0 > -1 > -3 > -4
		434
		435	# set priority to HIGH
		436	current->prio(PRIO_HIGH);
		437
		438	The idle coroutine ($Coro::idle) always has a lower priority than any
		439	existing coroutine.
		440
		441	Changing the priority of the current coroutine will take effect immediately,
		442	but changing the priority of coroutines in the ready queue (but not
		443	running) will only take effect after the next schedule (of that
		444	coroutine). This is a bug that will be fixed in some future version.
		445
		446	=item $newprio = $coroutine->nice ($change)
		447
		448	Similar to C<prio>, but subtract the given value from the priority (i.e.
		449	higher values mean lower priority, just as in unix).
		450
		451	=item $olddesc = $coroutine->desc ($newdesc)
		452
		453	Sets (or gets in case the argument is missing) the description for this
		454	coroutine. This is just a free-form string you can associate with a coroutine.
		455
		456	=cut
		457
		458	sub desc {
		459	my $old = $_[0]{desc};
		460	$_[0]{desc} = $_[1] if @_ > 1;
		461	$old;
		462	}
		463
		464	=back
		465
		466	=head2 GLOBAL FUNCTIONS
		467
		468	=over 4
		469
		470	=item Coro::nready
		471
		472	Returns the number of coroutines that are currently in the ready state,
		473	i.e. that can be switched to. The value C<0> means that the only runnable
		474	coroutine is the currently running one, so C<cede> would have no effect,
		475	and C<schedule> would cause a deadlock unless there is an idle handler
		476	that wakes up some coroutines.
		477
		478	=item my $guard = Coro::guard { ... }
		479
		480	This creates and returns a guard object. Nothing happens until the object
		481	gets destroyed, in which case the codeblock given as argument will be
		482	executed. This is useful to free locks or other resources in case of a
		483	runtime error or when the coroutine gets canceled, as in both cases the
		484	guard block will be executed. The guard object supports only one method,
		485	C<< ->cancel >>, which will keep the codeblock from being executed.
		486
		487	Example: set some flag and clear it again when the coroutine gets canceled
		488	or the function returns:
		489
		490	sub do_something {
		491	my $guard = Coro::guard { $busy = 0 };
		492	$busy = 1;
		493
		494	# do something that requires $busy to be true
		495	}
		496
		497	=cut
		498
		499	sub guard(&) {
		500	bless \(my $cb = $_[0]), "Coro::guard"
		501	}
		502
		503	sub Coro::guard::cancel {
		504	${$_[0]} = sub { };
		505	}
		506
		507	sub Coro::guard::DESTROY {
		508	${$_[0]}->();
		509	}
		510
		511
		512	=item unblock_sub { ... }
		513
		514	This utility function takes a BLOCK or code reference and "unblocks" it,
		515	returning the new coderef. This means that the new coderef will return
		516	immediately without blocking, returning nothing, while the original code
		517	ref will be called (with parameters) from within its own coroutine.
		518
		519	The reason this function exists is that many event libraries (such as the
		520	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		521	of thread-safety). This means you must not block within event callbacks,
		522	otherwise you might suffer from crashes or worse.
		523
		524	This function allows your callbacks to block by executing them in another
		525	coroutine where it is safe to block. One example where blocking is handy
		526	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		527	disk.
		528
		529	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		530	creating event callbacks that want to block.
		531
		532	=cut
		533
		534	our @unblock_queue;
		535
		536	# we create a special coro because we want to cede,
		537	# to reduce pressure on the coro pool (because most callbacks
		538	# return immediately and can be reused) and because we cannot cede
		539	# inside an event callback.
		540	our $unblock_scheduler = new Coro sub {
		541	while () {
		542	while (my $cb = pop @unblock_queue) {
		543	# this is an inlined copy of async_pool
		544	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		545
		546	$coro->{_invoke} = $cb;
		547	$coro->ready;
		548	cede; # for short-lived callbacks, this reduces pressure on the coro pool
70	}	549	}
71	} while (1);	550	schedule; # sleep well
72	}, $class;	551	}
73	}
74
75	=item $prev->transfer($next)
76
77	Save the state of the current subroutine in $prev and switch to the
78	coroutine saved in $next.
79
80	=cut
81
82	# I call the _transfer function from a perl function
83	# because that way perl saves all important things on
84	# the stack.
85	sub transfer {
86	_transfer($_[0], $_[1]);
87	}
88
89	=item $error, $error_msg, $error_coro
90
91	This coroutine will be called on fatal errors. C<$error_msg> and
92	C<$error_coro> return the error message and the error-causing coroutine
93	(NOT an object) respectively. This API might change.
94
95	=cut
96
97	$error_msg =
98	$error_coro = undef;
99
100	$error = _newprocess {
101	print STDERR "FATAL: $error_msg\nprogram aborted\n";
102	exit 50;
103	};	552	};
		553	$unblock_scheduler->desc ("[unblock_sub scheduler]");
		554
		555	sub unblock_sub(&) {
		556	my $cb = shift;
		557
		558	sub {
		559	unshift @unblock_queue, [$cb, @_];
		560	$unblock_scheduler->ready;
		561	}
		562	}
		563
		564	=back
		565
		566	=cut
104		567
105	1;	568	1;
106		569
107	=back	570	=head1 BUGS/LIMITATIONS
108		571
109	=head1 BUGS	572	- you must make very sure that no coro is still active on global
		573	destruction. very bad things might happen otherwise (usually segfaults).
110		574
111	This module has not yet been extensively tested.	575	- this module is not thread-safe. You should only ever use this module
		576	from the same thread (this requirement might be loosened in the future
		577	to allow per-thread schedulers, but Coro::State does not yet allow
		578	this).
112		579
113	=head1 SEE ALSO	580	=head1 SEE ALSO
114		581
115	L<Coro::Process>, L<Coro::Signal>.	582	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
		583
		584	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		585
		586	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
		587
		588	Embedding: L<Coro:MakeMaker>
116		589
117	=head1 AUTHOR	590	=head1 AUTHOR
118		591
119	Marc Lehmann <pcg@goof.com>	592	Marc Lehmann <schmorp@schmorp.de>
120	http://www.goof.com/pcg/marc/	593	http://home.schmorp.de/
121		594
122	=cut	595	=cut
123		596

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Comparing Coro/Coro.pm (file contents): Revision 1.6 by root, Tue Jul 10 21:19:47 2001 UTC vs. Revision 1.137 by root, Wed Sep 26 19:26:48 2007 UTC

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Comparing Coro/Coro.pm (file contents):
Revision 1.6 by root, Tue Jul 10 21:19:47 2001 UTC vs.
Revision 1.137 by root, Wed Sep 26 19:26:48 2007 UTC