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

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Revision 1.4 by root, Tue Jul 3 05:05:45 2001 UTC vs.
Revision 1.141 by root, Tue Oct 2 10:38:17 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 $VERSION = '3.8';
		56
		57	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
		58	our %EXPORT_TAGS = (
		59	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		60	);
		61	our @EXPORT_OK = (@{$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 = 0.01;
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->{destroy_cb}) \|\| []};
		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	Calling C<exit> in a coroutine will do the same as calling exit outside
		193	the coroutine. Likewise, when the coroutine dies, the program will exit,
		194	just as it would in the main program.
		195
		196	# create a new coroutine that just prints its arguments
		197	async {
		198	print "@_\n";
		199	} 1,2,3,4;
		200
83	=cut	201	=cut
		202
		203	sub async(&@) {
		204	my $coro = new Coro @_;
		205	$coro->ready;
		206	$coro
		207	}
		208
		209	=item async_pool { ... } [@args...]
		210
		211	Similar to C<async>, but uses a coroutine pool, so you should not call
		212	terminate or join (although you are allowed to), and you get a coroutine
		213	that might have executed other code already (which can be good or bad :).
		214
		215	Also, the block is executed in an C<eval> context and a warning will be
		216	issued in case of an exception instead of terminating the program, as
		217	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		218	will not work in the expected way, unless you call terminate or cancel,
		219	which somehow defeats the purpose of pooling.
		220
		221	The priority will be reset to C<0> after each job, otherwise the coroutine
		222	will be re-used "as-is".
		223
		224	The pool size is limited to 8 idle coroutines (this can be adjusted by
		225	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
		226	required.
		227
		228	If you are concerned about pooled coroutines growing a lot because a
		229	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		230	{ terminate }> once per second or so to slowly replenish the pool. In
		231	addition to that, when the stacks used by a handler grows larger than 16kb
		232	(adjustable with $Coro::POOL_RSS) it will also exit.
		233
		234	=cut
		235
		236	our $POOL_SIZE = 8;
		237	our $POOL_RSS = 16 * 1024;
		238	our @async_pool;
		239
		240	sub pool_handler {
		241	my $cb;
		242
		243	while () {
		244	eval {
		245	while () {
		246	_pool_1 $cb;
		247	&$cb;
		248	_pool_2 $cb;
		249	&schedule;
		250	}
		251	};
		252
		253	last if $@ eq "\3terminate\2\n";
		254	warn $@ if $@;
		255	}
		256	}
		257
		258	sub async_pool(&@) {
		259	# this is also inlined into the unlock_scheduler
		260	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		261
		262	$coro->{_invoke} = [@_];
		263	$coro->ready;
		264
		265	$coro
		266	}
		267
		268	=item schedule
		269
		270	Calls the scheduler. Please note that the current coroutine will not be put
		271	into the ready queue, so calling this function usually means you will
		272	never be called again unless something else (e.g. an event handler) calls
		273	ready.
		274
		275	The canonical way to wait on external events is this:
		276
		277	{
		278	# remember current coroutine
		279	my $current = $Coro::current;
		280
		281	# register a hypothetical event handler
		282	on_event_invoke sub {
		283	# wake up sleeping coroutine
		284	$current->ready;
		285	undef $current;
		286	};
		287
		288	# call schedule until event occurred.
		289	# in case we are woken up for other reasons
		290	# (current still defined), loop.
		291	Coro::schedule while $current;
		292	}
		293
		294	=item cede
		295
		296	"Cede" to other coroutines. This function puts the current coroutine into the
		297	ready queue and calls C<schedule>, which has the effect of giving up the
		298	current "timeslice" to other coroutines of the same or higher priority.
		299
		300	Returns true if at least one coroutine switch has happened.
		301
		302	=item Coro::cede_notself
		303
		304	Works like cede, but is not exported by default and will cede to any
		305	coroutine, regardless of priority, once.
		306
		307	Returns true if at least one coroutine switch has happened.
		308
		309	=item terminate [arg...]
		310
		311	Terminates the current coroutine with the given status values (see L<cancel>).
		312
		313	=item killall
		314
		315	Kills/terminates/cancels all coroutines except the currently running
		316	one. This is useful after a fork, either in the child or the parent, as
		317	usually only one of them should inherit the running coroutines.
		318
		319	=cut
		320
		321	sub terminate {
		322	$current->cancel (@_);
		323	}
		324
		325	sub killall {
		326	for (Coro::State::list) {
		327	$_->cancel
		328	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		329	}
		330	}
		331
		332	=back
		333
		334	# dynamic methods
		335
		336	=head2 COROUTINE METHODS
		337
		338	These are the methods you can call on coroutine objects.
		339
		340	=over 4
		341
		342	=item new Coro \&sub [, @args...]
		343
		344	Create a new coroutine and return it. When the sub returns the coroutine
		345	automatically terminates as if C<terminate> with the returned values were
		346	called. To make the coroutine run you must first put it into the ready queue
		347	by calling the ready method.
		348
		349	See C<async> for additional discussion.
		350
		351	=cut
		352
		353	sub _run_coro {
		354	terminate &{+shift};
		355	}
84		356
85	sub new {	357	sub new {
86	my $class = $_[0];	358	my $class = shift;
87	my $proc = $_[1];	359
88	bless _newprocess {	360	$class->SUPER::new (\&_run_coro, @_)
89	do {	361	}
90	eval { &$proc->resume };	362
91	if ($@) {	363	=item $success = $coroutine->ready
92	($error_msg, $error_coro) = ($@, $current);	364
93	$error->resume;	365	Put the given coroutine into the ready queue (according to it's priority)
		366	and return true. If the coroutine is already in the ready queue, do nothing
		367	and return false.
		368
		369	=item $is_ready = $coroutine->is_ready
		370
		371	Return wether the coroutine is currently the ready queue or not,
		372
		373	=item $coroutine->cancel (arg...)
		374
		375	Terminates the given coroutine and makes it return the given arguments as
		376	status (default: the empty list). Never returns if the coroutine is the
		377	current coroutine.
		378
		379	=cut
		380
		381	sub cancel {
		382	my $self = shift;
		383	$self->{status} = [@_];
		384
		385	if ($current == $self) {
		386	push @destroy, $self;
		387	$manager->ready;
		388	&schedule while 1;
		389	} else {
		390	$self->_cancel;
		391	}
		392	}
		393
		394	=item $coroutine->join
		395
		396	Wait until the coroutine terminates and return any values given to the
		397	C<terminate> or C<cancel> functions. C<join> can be called multiple times
		398	from multiple coroutine.
		399
		400	=cut
		401
		402	sub join {
		403	my $self = shift;
		404
		405	unless ($self->{status}) {
		406	my $current = $current;
		407
		408	push @{$self->{destroy_cb}}, sub {
		409	$current->ready;
		410	undef $current;
		411	};
		412
		413	&schedule while $current;
		414	}
		415
		416	wantarray ? @{$self->{status}} : $self->{status}[0];
		417	}
		418
		419	=item $coroutine->on_destroy (\&cb)
		420
		421	Registers a callback that is called when this coroutine gets destroyed,
		422	but before it is joined. The callback gets passed the terminate arguments,
		423	if any.
		424
		425	=cut
		426
		427	sub on_destroy {
		428	my ($self, $cb) = @_;
		429
		430	push @{ $self->{destroy_cb} }, $cb;
		431	}
		432
		433	=item $oldprio = $coroutine->prio ($newprio)
		434
		435	Sets (or gets, if the argument is missing) the priority of the
		436	coroutine. Higher priority coroutines get run before lower priority
		437	coroutines. Priorities are small signed integers (currently -4 .. +3),
		438	that you can refer to using PRIO_xxx constants (use the import tag :prio
		439	to get then):
		440
		441	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		442	3 > 1 > 0 > -1 > -3 > -4
		443
		444	# set priority to HIGH
		445	current->prio(PRIO_HIGH);
		446
		447	The idle coroutine ($Coro::idle) always has a lower priority than any
		448	existing coroutine.
		449
		450	Changing the priority of the current coroutine will take effect immediately,
		451	but changing the priority of coroutines in the ready queue (but not
		452	running) will only take effect after the next schedule (of that
		453	coroutine). This is a bug that will be fixed in some future version.
		454
		455	=item $newprio = $coroutine->nice ($change)
		456
		457	Similar to C<prio>, but subtract the given value from the priority (i.e.
		458	higher values mean lower priority, just as in unix).
		459
		460	=item $olddesc = $coroutine->desc ($newdesc)
		461
		462	Sets (or gets in case the argument is missing) the description for this
		463	coroutine. This is just a free-form string you can associate with a coroutine.
		464
		465	=cut
		466
		467	sub desc {
		468	my $old = $_[0]{desc};
		469	$_[0]{desc} = $_[1] if @_ > 1;
		470	$old;
		471	}
		472
		473	=back
		474
		475	=head2 GLOBAL FUNCTIONS
		476
		477	=over 4
		478
		479	=item Coro::nready
		480
		481	Returns the number of coroutines that are currently in the ready state,
		482	i.e. that can be switched to. The value C<0> means that the only runnable
		483	coroutine is the currently running one, so C<cede> would have no effect,
		484	and C<schedule> would cause a deadlock unless there is an idle handler
		485	that wakes up some coroutines.
		486
		487	=item my $guard = Coro::guard { ... }
		488
		489	This creates and returns a guard object. Nothing happens until the object
		490	gets destroyed, in which case the codeblock given as argument will be
		491	executed. This is useful to free locks or other resources in case of a
		492	runtime error or when the coroutine gets canceled, as in both cases the
		493	guard block will be executed. The guard object supports only one method,
		494	C<< ->cancel >>, which will keep the codeblock from being executed.
		495
		496	Example: set some flag and clear it again when the coroutine gets canceled
		497	or the function returns:
		498
		499	sub do_something {
		500	my $guard = Coro::guard { $busy = 0 };
		501	$busy = 1;
		502
		503	# do something that requires $busy to be true
		504	}
		505
		506	=cut
		507
		508	sub guard(&) {
		509	bless \(my $cb = $_[0]), "Coro::guard"
		510	}
		511
		512	sub Coro::guard::cancel {
		513	${$_[0]} = sub { };
		514	}
		515
		516	sub Coro::guard::DESTROY {
		517	${$_[0]}->();
		518	}
		519
		520
		521	=item unblock_sub { ... }
		522
		523	This utility function takes a BLOCK or code reference and "unblocks" it,
		524	returning the new coderef. This means that the new coderef will return
		525	immediately without blocking, returning nothing, while the original code
		526	ref will be called (with parameters) from within its own coroutine.
		527
		528	The reason this function exists is that many event libraries (such as the
		529	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		530	of thread-safety). This means you must not block within event callbacks,
		531	otherwise you might suffer from crashes or worse.
		532
		533	This function allows your callbacks to block by executing them in another
		534	coroutine where it is safe to block. One example where blocking is handy
		535	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		536	disk.
		537
		538	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		539	creating event callbacks that want to block.
		540
		541	=cut
		542
		543	our @unblock_queue;
		544
		545	# we create a special coro because we want to cede,
		546	# to reduce pressure on the coro pool (because most callbacks
		547	# return immediately and can be reused) and because we cannot cede
		548	# inside an event callback.
		549	our $unblock_scheduler = new Coro sub {
		550	while () {
		551	while (my $cb = pop @unblock_queue) {
		552	# this is an inlined copy of async_pool
		553	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		554
		555	$coro->{_invoke} = $cb;
		556	$coro->ready;
		557	cede; # for short-lived callbacks, this reduces pressure on the coro pool
94	}	558	}
95	} while (1);	559	schedule; # sleep well
96	}, $class;	560	}
97	}	561	};
		562	$unblock_scheduler->desc ("[unblock_sub scheduler]");
98		563
99	=item $coro->resume	564	sub unblock_sub(&) {
		565	my $cb = shift;
100		566
101	Resume execution at the given coroutine.	567	sub {
102		568	unshift @unblock_queue, [$cb, @_];
103	=cut	569	$unblock_scheduler->ready;
104		570	}
105	my $prev;
106
107	sub resume {
108	$prev = $current; $current = $_[0];
109	_transfer($prev, $current);
110	}	571	}
		572
		573	=back
		574
		575	=cut
111		576
112	1;	577	1;
113		578
114	=back	579	=head1 BUGS/LIMITATIONS
115		580
116	=head1 BUGS	581	- you must make very sure that no coro is still active on global
		582	destruction. very bad things might happen otherwise (usually segfaults).
117		583
118	This module has not yet been extensively tested.	584	- this module is not thread-safe. You should only ever use this module
		585	from the same thread (this requirement might be loosened in the future
		586	to allow per-thread schedulers, but Coro::State does not yet allow
		587	this).
119		588
120	=head1 SEE ALSO	589	=head1 SEE ALSO
121		590
122	L<Coro::Process>, L<Coro::Signal>.	591	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
		592
		593	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		594
		595	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
		596
		597	Embedding: L<Coro:MakeMaker>
123		598
124	=head1 AUTHOR	599	=head1 AUTHOR
125		600
126	Marc Lehmann <pcg@goof.com>	601	Marc Lehmann <schmorp@schmorp.de>
127	http://www.goof.com/pcg/marc/	602	http://home.schmorp.de/
128		603
129	=cut	604	=cut
130		605

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Comparing Coro/Coro.pm (file contents): Revision 1.4 by root, Tue Jul 3 05:05:45 2001 UTC vs. Revision 1.141 by root, Tue Oct 2 10:38:17 2007 UTC

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Comparing Coro/Coro.pm (file contents):
Revision 1.4 by root, Tue Jul 3 05:05:45 2001 UTC vs.
Revision 1.141 by root, Tue Oct 2 10:38:17 2007 UTC