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

Comparing Coro/Coro.pm (file contents):
Revision 1.7 by root, Fri Jul 13 13:05:38 2001 UTC vs.
Revision 1.145 by root, Wed Oct 3 16:03:17 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 $VERSION = '4.0';
		56
		57	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
		58	our %EXPORT_TAGS = (
		59	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		60	);
		61	our @EXPORT_OK = (@{$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->{_on_destroy}) \|\| []};
		158	}
57		159
		160	# this coroutine is necessary because a coroutine
		161	# cannot destroy itself.
		162	my @destroy;
		163	my $manager;
		164
		165	$manager = new Coro sub {
		166	while () {
		167	(shift @destroy)->_cancel
		168	while @destroy;
		169
		170	&schedule;
		171	}
		172	};
		173	$manager->desc ("[coro manager]");
		174	$manager->prio (PRIO_MAX);
		175
		176	# static methods. not really.
		177
		178	=back
		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
58	=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, otherwise the coroutine
		225	will be re-used "as-is".
		226
		227	The pool size is limited to 8 idle coroutines (this can be adjusted by
		228	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
		229	required.
		230
		231	If you are concerned about pooled coroutines growing a lot because a
		232	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		233	{ terminate }> once per second or so to slowly replenish the pool. In
		234	addition to that, when the stacks used by a handler grows larger than 16kb
		235	(adjustable with $Coro::POOL_RSS) it will also exit.
		236
		237	=cut
		238
		239	our $POOL_SIZE = 8;
		240	our $POOL_RSS = 16 * 1024;
		241	our @async_pool;
		242
		243	sub pool_handler {
		244	my $cb;
		245
		246	while () {
		247	eval {
		248	while () {
		249	_pool_1 $cb;
		250	&$cb;
		251	_pool_2 $cb;
		252	&schedule;
		253	}
		254	};
		255
		256	last if $@ eq "\3terminate\2\n";
		257	warn $@ if $@;
		258	}
		259	}
		260
		261	sub async_pool(&@) {
		262	# this is also inlined into the unlock_scheduler
		263	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		264
		265	$coro->{_invoke} = [@_];
		266	$coro->ready;
		267
		268	$coro
		269	}
		270
		271	=item schedule
		272
		273	Calls the scheduler. Please note that the current coroutine will not be put
		274	into the ready queue, so calling this function usually means you will
		275	never be called again unless something else (e.g. an event handler) calls
		276	ready.
		277
		278	The canonical way to wait on external events is this:
		279
		280	{
		281	# remember current coroutine
		282	my $current = $Coro::current;
		283
		284	# register a hypothetical event handler
		285	on_event_invoke sub {
		286	# wake up sleeping coroutine
		287	$current->ready;
		288	undef $current;
		289	};
		290
		291	# call schedule until event occurred.
		292	# in case we are woken up for other reasons
		293	# (current still defined), loop.
		294	Coro::schedule while $current;
		295	}
		296
		297	=item cede
		298
		299	"Cede" to other coroutines. This function puts the current coroutine into the
		300	ready queue and calls C<schedule>, which has the effect of giving up the
		301	current "timeslice" to other coroutines of the same or higher priority.
		302
		303	Returns true if at least one coroutine switch has happened.
		304
		305	=item Coro::cede_notself
		306
		307	Works like cede, but is not exported by default and will cede to any
		308	coroutine, regardless of priority, once.
		309
		310	Returns true if at least one coroutine switch has happened.
		311
		312	=item terminate [arg...]
		313
		314	Terminates the current coroutine with the given status values (see L<cancel>).
		315
		316	=item killall
		317
		318	Kills/terminates/cancels all coroutines except the currently running
		319	one. This is useful after a fork, either in the child or the parent, as
		320	usually only one of them should inherit the running coroutines.
		321
		322	=cut
		323
		324	sub terminate {
		325	$current->cancel (@_);
		326	}
		327
		328	sub killall {
		329	for (Coro::State::list) {
		330	$_->cancel
		331	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		332	}
		333	}
		334
		335	=back
		336
		337	# dynamic methods
		338
		339	=head2 COROUTINE METHODS
		340
		341	These are the methods you can call on coroutine objects.
		342
		343	=over 4
		344
		345	=item new Coro \&sub [, @args...]
		346
		347	Create a new coroutine and return it. When the sub returns the coroutine
		348	automatically terminates as if C<terminate> with the returned values were
		349	called. To make the coroutine run you must first put it into the ready queue
		350	by calling the ready method.
		351
		352	See C<async> and C<Coro::State::new> for additional info about the
		353	coroutine environment.
		354
		355	=cut
		356
		357	sub _run_coro {
		358	terminate &{+shift};
		359	}
59		360
60	sub new {	361	sub new {
61	my $class = $_[0];	362	my $class = shift;
62	my $proc = $_[1] \|\| sub { die "tried to transfer to an empty coroutine" };
63	bless _newprocess {
64	do {
65	eval { &$proc };
66	if ($@) {
67	$error_msg = $@;
68	$error_coro = _newprocess { };
69	&transfer($error_coro, $error);
70	}
71	} while (1);
72	}, $class;
73	}
74		363
75	=item $prev->transfer($next)	364	$class->SUPER::new (\&_run_coro, @_)
		365	}
76		366
77	Save the state of the current subroutine in C<$prev> and switch to the	367	=item $success = $coroutine->ready
78	coroutine saved in C<$next>.
79		368
80	The "state" of a subroutine only ever includes scope, i.e. lexical	369	Put the given coroutine into the ready queue (according to it's priority)
81	variables and the current execution state. It does not save/restore any	370	and return true. If the coroutine is already in the ready queue, do nothing
82	global variables such as C<$_> or C<$@> or any other special or non	371	and return false.
83	special variables. So remember that every function call that might call
84	C<transfer> (such as C<Coro::Channel::put>) might clobber any global
85	and/or special variables. Yes, this is by design ;) You cna always create
86	your own process abstraction model that saves these variables.
87		372
88	The easiest way to do this is to create your own scheduling primitive like this:	373	=item $is_ready = $coroutine->is_ready
89		374
90	sub schedule {	375	Return wether the coroutine is currently the ready queue or not,
91	local ($_, $@, ...);	376
92	$old->transfer($new);	377	=item $coroutine->cancel (arg...)
		378
		379	Terminates the given coroutine and makes it return the given arguments as
		380	status (default: the empty list). Never returns if the coroutine is the
		381	current coroutine.
		382
		383	=cut
		384
		385	sub cancel {
		386	my $self = shift;
		387	$self->{_status} = [@_];
		388
		389	if ($current == $self) {
		390	push @destroy, $self;
		391	$manager->ready;
		392	&schedule while 1;
		393	} else {
		394	$self->_cancel;
93	}	395	}
94
95	=cut
96
97	# I call the _transfer function from a perl function
98	# because that way perl saves all important things on
99	# the stack. Actually, I'd do it from within XS, but
100	# I couldn't get it to work.
101	sub transfer {
102	_transfer($_[0], $_[1]);
103	}	396	}
104		397
105	=item $error, $error_msg, $error_coro	398	=item $coroutine->join
106		399
107	This coroutine will be called on fatal errors. C<$error_msg> and	400	Wait until the coroutine terminates and return any values given to the
108	C<$error_coro> return the error message and the error-causing coroutine	401	C<terminate> or C<cancel> functions. C<join> can be called concurrently
109	(NOT an object) respectively. This API might change.	402	from multiple coroutines.
110		403
111	=cut	404	=cut
112		405
113	$error_msg =	406	sub join {
114	$error_coro = undef;	407	my $self = shift;
115		408
116	$error = _newprocess {	409	unless ($self->{_status}) {
117	print STDERR "FATAL: $error_msg\nprogram aborted\n";	410	my $current = $current;
118	exit 50;	411
		412	push @{$self->{_on_destroy}}, sub {
		413	$current->ready;
		414	undef $current;
		415	};
		416
		417	&schedule while $current;
		418	}
		419
		420	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		421	}
		422
		423	=item $coroutine->on_destroy (\&cb)
		424
		425	Registers a callback that is called when this coroutine gets destroyed,
		426	but before it is joined. The callback gets passed the terminate arguments,
		427	if any.
		428
		429	=cut
		430
		431	sub on_destroy {
		432	my ($self, $cb) = @_;
		433
		434	push @{ $self->{_on_destroy} }, $cb;
		435	}
		436
		437	=item $oldprio = $coroutine->prio ($newprio)
		438
		439	Sets (or gets, if the argument is missing) the priority of the
		440	coroutine. Higher priority coroutines get run before lower priority
		441	coroutines. Priorities are small signed integers (currently -4 .. +3),
		442	that you can refer to using PRIO_xxx constants (use the import tag :prio
		443	to get then):
		444
		445	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		446	3 > 1 > 0 > -1 > -3 > -4
		447
		448	# set priority to HIGH
		449	current->prio(PRIO_HIGH);
		450
		451	The idle coroutine ($Coro::idle) always has a lower priority than any
		452	existing coroutine.
		453
		454	Changing the priority of the current coroutine will take effect immediately,
		455	but changing the priority of coroutines in the ready queue (but not
		456	running) will only take effect after the next schedule (of that
		457	coroutine). This is a bug that will be fixed in some future version.
		458
		459	=item $newprio = $coroutine->nice ($change)
		460
		461	Similar to C<prio>, but subtract the given value from the priority (i.e.
		462	higher values mean lower priority, just as in unix).
		463
		464	=item $olddesc = $coroutine->desc ($newdesc)
		465
		466	Sets (or gets in case the argument is missing) the description for this
		467	coroutine. This is just a free-form string you can associate with a coroutine.
		468
		469	This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
		470	can modify this member directly if you wish.
		471
		472	=cut
		473
		474	sub desc {
		475	my $old = $_[0]{desc};
		476	$_[0]{desc} = $_[1] if @_ > 1;
		477	$old;
		478	}
		479
		480	=back
		481
		482	=head2 GLOBAL FUNCTIONS
		483
		484	=over 4
		485
		486	=item Coro::nready
		487
		488	Returns the number of coroutines that are currently in the ready state,
		489	i.e. that can be switched to. The value C<0> means that the only runnable
		490	coroutine is the currently running one, so C<cede> would have no effect,
		491	and C<schedule> would cause a deadlock unless there is an idle handler
		492	that wakes up some coroutines.
		493
		494	=item my $guard = Coro::guard { ... }
		495
		496	This creates and returns a guard object. Nothing happens until the object
		497	gets destroyed, in which case the codeblock given as argument will be
		498	executed. This is useful to free locks or other resources in case of a
		499	runtime error or when the coroutine gets canceled, as in both cases the
		500	guard block will be executed. The guard object supports only one method,
		501	C<< ->cancel >>, which will keep the codeblock from being executed.
		502
		503	Example: set some flag and clear it again when the coroutine gets canceled
		504	or the function returns:
		505
		506	sub do_something {
		507	my $guard = Coro::guard { $busy = 0 };
		508	$busy = 1;
		509
		510	# do something that requires $busy to be true
		511	}
		512
		513	=cut
		514
		515	sub guard(&) {
		516	bless \(my $cb = $_[0]), "Coro::guard"
		517	}
		518
		519	sub Coro::guard::cancel {
		520	${$_[0]} = sub { };
		521	}
		522
		523	sub Coro::guard::DESTROY {
		524	${$_[0]}->();
		525	}
		526
		527
		528	=item unblock_sub { ... }
		529
		530	This utility function takes a BLOCK or code reference and "unblocks" it,
		531	returning the new coderef. This means that the new coderef will return
		532	immediately without blocking, returning nothing, while the original code
		533	ref will be called (with parameters) from within its own coroutine.
		534
		535	The reason this function exists is that many event libraries (such as the
		536	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		537	of thread-safety). This means you must not block within event callbacks,
		538	otherwise you might suffer from crashes or worse.
		539
		540	This function allows your callbacks to block by executing them in another
		541	coroutine where it is safe to block. One example where blocking is handy
		542	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		543	disk.
		544
		545	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		546	creating event callbacks that want to block.
		547
		548	=cut
		549
		550	our @unblock_queue;
		551
		552	# we create a special coro because we want to cede,
		553	# to reduce pressure on the coro pool (because most callbacks
		554	# return immediately and can be reused) and because we cannot cede
		555	# inside an event callback.
		556	our $unblock_scheduler = new Coro sub {
		557	while () {
		558	while (my $cb = pop @unblock_queue) {
		559	# this is an inlined copy of async_pool
		560	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		561
		562	$coro->{_invoke} = $cb;
		563	$coro->ready;
		564	cede; # for short-lived callbacks, this reduces pressure on the coro pool
		565	}
		566	schedule; # sleep well
		567	}
119	};	568	};
		569	$unblock_scheduler->desc ("[unblock_sub scheduler]");
		570
		571	sub unblock_sub(&) {
		572	my $cb = shift;
		573
		574	sub {
		575	unshift @unblock_queue, [$cb, @_];
		576	$unblock_scheduler->ready;
		577	}
		578	}
		579
		580	=back
		581
		582	=cut
120		583
121	1;	584	1;
122		585
123	=back	586	=head1 BUGS/LIMITATIONS
124		587
125	=head1 BUGS	588	- you must make very sure that no coro is still active on global
		589	destruction. very bad things might happen otherwise (usually segfaults).
126		590
127	This module has not yet been extensively tested.	591	- this module is not thread-safe. You should only ever use this module
		592	from the same thread (this requirement might be loosened in the future
		593	to allow per-thread schedulers, but Coro::State does not yet allow
		594	this).
128		595
129	=head1 SEE ALSO	596	=head1 SEE ALSO
130		597
131	L<Coro::Process>, L<Coro::Signal>.	598	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
		599
		600	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		601
		602	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
		603
		604	Embedding: L<Coro:MakeMaker>
132		605
133	=head1 AUTHOR	606	=head1 AUTHOR
134		607
135	Marc Lehmann <pcg@goof.com>	608	Marc Lehmann <schmorp@schmorp.de>
136	http://www.goof.com/pcg/marc/	609	http://home.schmorp.de/
137		610
138	=cut	611	=cut
139		612

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Comparing Coro/Coro.pm (file contents): Revision 1.7 by root, Fri Jul 13 13:05:38 2001 UTC vs. Revision 1.145 by root, Wed Oct 3 16:03:17 2007 UTC

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Comparing Coro/Coro.pm (file contents):
Revision 1.7 by root, Fri Jul 13 13:05:38 2001 UTC vs.
Revision 1.145 by root, Wed Oct 3 16:03:17 2007 UTC