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

Comparing Coro/Coro.pm (file contents):
Revision 1.4 by root, Tue Jul 3 05:05:45 2001 UTC vs.
Revision 1.178 by root, Thu Apr 17 22:33:10 2008 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;	11	print "2\n";
12	print "in coroutine again, switching back\n";	12	cede; # yield back to main
13	$Coro::main->resume;	13	print "4\n";
14	};	14	};
		15	print "1\n";
		16	cede; # yield to coroutine
		17	print "3\n";
		18	cede; # and again
15		19
16	print "in main, switching to coroutine\n";	20	# use locking
17	$new->resume;	21	my $lock = new Coro::Semaphore;
18	print "back in main, switch to coroutine again\n";	22	my $locked;
19	$new->resume;	23
20	print "back in main\n";	24	$lock->down;
		25	$locked = 1;
		26	$lock->up;
21		27
22	=head1 DESCRIPTION	28	=head1 DESCRIPTION
23		29
24	This module implements coroutines. Coroutines, similar to continuations,	30	This module collection manages coroutines. Coroutines are similar
25	allow you to run more than one "thread of execution" in parallel. Unlike	31	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	32	machines. The specific flavor of coroutine used in this module also
27	greatly reduced.	33	guarantees you that it will not switch between coroutines unless
		34	necessary, at easily-identified points in your program, so locking and
		35	parallel access are rarely an issue, making coroutine programming much
		36	safer than threads programming.
28		37
29	Although this is the "main" module of the Coro family it provides only	38	(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	39	very slow and memory-intensive emulation of processes using threads. This
31	more useful process abstraction including scheduling.	40	is a performance win on Windows machines, and a loss everywhere else).
		41
		42	In this module, coroutines are defined as "callchain + lexical variables +
		43	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
		44	its own set of lexicals and its own set of perls most important global
		45	variables (see L<Coro::State> for more configuration).
		46
		47	=cut
		48
		49	package Coro;
		50
		51	use strict;
		52	no warnings "uninitialized";
		53
		54	use Coro::State;
		55
		56	use base qw(Coro::State Exporter);
		57
		58	our $idle; # idle handler
		59	our $main; # main coroutine
		60	our $current; # current coroutine
		61
		62	our $VERSION = '4.51';
		63
		64	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
		65	our %EXPORT_TAGS = (
		66	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		67	);
		68	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
		69
		70	{
		71	my @async;
		72	my $init;
		73
		74	# this way of handling attributes simply is NOT scalable ;()
		75	sub import {
		76	no strict 'refs';
		77
		78	Coro->export_to_level (1, @_);
		79
		80	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
		81	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
		82	my ($package, $ref) = (shift, shift);
		83	my @attrs;
		84	for (@_) {
		85	if ($_ eq "Coro") {
		86	push @async, $ref;
		87	unless ($init++) {
		88	eval q{
		89	sub INIT {
		90	&async(pop @async) while @async;
		91	}
		92	};
		93	}
		94	} else {
		95	push @attrs, $_;
		96	}
		97	}
		98	return $old ? $old->($package, $ref, @attrs) : @attrs;
		99	};
		100	}
		101
		102	}
32		103
33	=over 4	104	=over 4
34		105
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	106	=item $main
47		107
48	This coroutine represents the main program.	108	This coroutine represents the main program.
49		109
50	=item $current	110	=cut
51		111
		112	$main = new Coro;
		113
		114	=item $current (or as function: current)
		115
52	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).	116	The current coroutine (the last coroutine switched to). The initial value
		117	is C<$main> (of course).
53		118
54	=cut	119	This variable is B<strictly> I<read-only>. It is provided for performance
		120	reasons. If performance is not essential you are encouraged to use the
		121	C<Coro::current> function instead.
55		122
56	$main = $current = _newprocess {	123	=cut
57	# never being called	124
		125	$main->{desc} = "[main::]";
		126
		127	# maybe some other module used Coro::Specific before...
		128	$main->{_specific} = $current->{_specific}
		129	if $current;
		130
		131	_set_current $main;
		132
		133	sub current() { $current }
		134
		135	=item $idle
		136
		137	A callback that is called whenever the scheduler finds no ready coroutines
		138	to run. The default implementation prints "FATAL: deadlock detected" and
		139	exits, because the program has no other way to continue.
		140
		141	This hook is overwritten by modules such as C<Coro::Timer> and
		142	C<Coro::Event> to wait on an external event that hopefully wake up a
		143	coroutine so the scheduler can run it.
		144
		145	Please note that if your callback recursively invokes perl (e.g. for event
		146	handlers), then it must be prepared to be called recursively itself.
		147
		148	=cut
		149
		150	$idle = sub {
		151	require Carp;
		152	Carp::croak ("FATAL: deadlock detected");
58	};	153	};
59		154
60	=item $error, $error_msg, $error_coro	155	sub _cancel {
		156	my ($self) = @_;
61		157
62	This coroutine will be called on fatal errors. C<$error_msg> and	158	# free coroutine data and mark as destructed
63	C<$error_coro> return the error message and the error-causing coroutine,	159	$self->_destroy
64	respectively.	160	or return;
65		161
66	=cut	162	# call all destruction callbacks
		163	$_->(@{$self->{_status}})
		164	for @{(delete $self->{_on_destroy}) \|\| []};
		165	}
67		166
68	$error_msg =	167	# this coroutine is necessary because a coroutine
69	$error_coro = undef;	168	# cannot destroy itself.
		169	my @destroy;
		170	my $manager;
70		171
71	$error = _newprocess {	172	$manager = new Coro sub {
72	print STDERR "FATAL: $error_msg\nprogram aborted\n";	173	while () {
73	exit 250;	174	(shift @destroy)->_cancel
		175	while @destroy;
		176
		177	&schedule;
		178	}
74	};	179	};
		180	$manager->desc ("[coro manager]");
		181	$manager->prio (PRIO_MAX);
75		182
76	=item $coro = new $coderef [, @args]	183	=back
77		184
78	Create a new coroutine and return it. The first C<resume> call to this	185	=head2 STATIC METHODS
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		186
		187	Static methods are actually functions that operate on the current coroutine only.
		188
		189	=over 4
		190
		191	=item async { ... } [@args...]
		192
		193	Create a new asynchronous coroutine and return it's coroutine object
		194	(usually unused). When the sub returns the new coroutine is automatically
		195	terminated.
		196
		197	See the C<Coro::State::new> constructor for info about the coroutine
		198	environment in which coroutines run.
		199
		200	Calling C<exit> in a coroutine will do the same as calling exit outside
		201	the coroutine. Likewise, when the coroutine dies, the program will exit,
		202	just as it would in the main program.
		203
		204	# create a new coroutine that just prints its arguments
		205	async {
		206	print "@_\n";
		207	} 1,2,3,4;
		208
83	=cut	209	=cut
		210
		211	sub async(&@) {
		212	my $coro = new Coro @_;
		213	$coro->ready;
		214	$coro
		215	}
		216
		217	=item async_pool { ... } [@args...]
		218
		219	Similar to C<async>, but uses a coroutine pool, so you should not call
		220	terminate or join (although you are allowed to), and you get a coroutine
		221	that might have executed other code already (which can be good or bad :).
		222
		223	Also, the block is executed in an C<eval> context and a warning will be
		224	issued in case of an exception instead of terminating the program, as
		225	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		226	will not work in the expected way, unless you call terminate or cancel,
		227	which somehow defeats the purpose of pooling.
		228
		229	The priority will be reset to C<0> after each job, tracing will be
		230	disabled, the description will be reset and the default output filehandle
		231	gets restored, so you can change alkl these. Otherwise the coroutine will
		232	be re-used "as-is": most notably if you change other per-coroutine global
		233	stuff such as C<$/> you need to revert that change, which is most simply
		234	done by using local as in C< local $/ >.
		235
		236	The pool size is limited to 8 idle coroutines (this can be adjusted by
		237	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
		238	required.
		239
		240	If you are concerned about pooled coroutines growing a lot because a
		241	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		242	{ terminate }> once per second or so to slowly replenish the pool. In
		243	addition to that, when the stacks used by a handler grows larger than 16kb
		244	(adjustable with $Coro::POOL_RSS) it will also exit.
		245
		246	=cut
		247
		248	our $POOL_SIZE = 8;
		249	our $POOL_RSS = 16 * 1024;
		250	our @async_pool;
		251
		252	sub pool_handler {
		253	my $cb;
		254
		255	while () {
		256	eval {
		257	while () {
		258	_pool_1 $cb;
		259	&$cb;
		260	_pool_2 $cb;
		261	&schedule;
		262	}
		263	};
		264
		265	last if $@ eq "\3async_pool terminate\2\n";
		266	warn $@ if $@;
		267	}
		268	}
		269
		270	sub async_pool(&@) {
		271	# this is also inlined into the unlock_scheduler
		272	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		273
		274	$coro->{_invoke} = [@_];
		275	$coro->ready;
		276
		277	$coro
		278	}
		279
		280	=item schedule
		281
		282	Calls the scheduler. Please note that the current coroutine will not be put
		283	into the ready queue, so calling this function usually means you will
		284	never be called again unless something else (e.g. an event handler) calls
		285	ready.
		286
		287	The canonical way to wait on external events is this:
		288
		289	{
		290	# remember current coroutine
		291	my $current = $Coro::current;
		292
		293	# register a hypothetical event handler
		294	on_event_invoke sub {
		295	# wake up sleeping coroutine
		296	$current->ready;
		297	undef $current;
		298	};
		299
		300	# call schedule until event occurred.
		301	# in case we are woken up for other reasons
		302	# (current still defined), loop.
		303	Coro::schedule while $current;
		304	}
		305
		306	=item cede
		307
		308	"Cede" to other coroutines. This function puts the current coroutine into the
		309	ready queue and calls C<schedule>, which has the effect of giving up the
		310	current "timeslice" to other coroutines of the same or higher priority.
		311
		312	=item Coro::cede_notself
		313
		314	Works like cede, but is not exported by default and will cede to any
		315	coroutine, regardless of priority, once.
		316
		317	=item terminate [arg...]
		318
		319	Terminates the current coroutine with the given status values (see L<cancel>).
		320
		321	=item killall
		322
		323	Kills/terminates/cancels all coroutines except the currently running
		324	one. This is useful after a fork, either in the child or the parent, as
		325	usually only one of them should inherit the running coroutines.
		326
		327	=cut
		328
		329	sub terminate {
		330	$current->cancel (@_);
		331	}
		332
		333	sub killall {
		334	for (Coro::State::list) {
		335	$_->cancel
		336	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		337	}
		338	}
		339
		340	=back
		341
		342	=head2 COROUTINE METHODS
		343
		344	These are the methods you can call on coroutine objects.
		345
		346	=over 4
		347
		348	=item new Coro \&sub [, @args...]
		349
		350	Create a new coroutine and return it. When the sub returns the coroutine
		351	automatically terminates as if C<terminate> with the returned values were
		352	called. To make the coroutine run you must first put it into the ready queue
		353	by calling the ready method.
		354
		355	See C<async> and C<Coro::State::new> for additional info about the
		356	coroutine environment.
		357
		358	=cut
		359
		360	sub _run_coro {
		361	terminate &{+shift};
		362	}
84		363
85	sub new {	364	sub new {
86	my $class = $_[0];	365	my $class = shift;
87	my $proc = $_[1];	366
88	bless _newprocess {	367	$class->SUPER::new (\&_run_coro, @_)
89	do {	368	}
90	eval { &$proc->resume };	369
91	if ($@) {	370	=item $success = $coroutine->ready
92	($error_msg, $error_coro) = ($@, $current);	371
93	$error->resume;	372	Put the given coroutine into the ready queue (according to it's priority)
		373	and return true. If the coroutine is already in the ready queue, do nothing
		374	and return false.
		375
		376	=item $is_ready = $coroutine->is_ready
		377
		378	Return wether the coroutine is currently the ready queue or not,
		379
		380	=item $coroutine->cancel (arg...)
		381
		382	Terminates the given coroutine and makes it return the given arguments as
		383	status (default: the empty list). Never returns if the coroutine is the
		384	current coroutine.
		385
		386	=cut
		387
		388	sub cancel {
		389	my $self = shift;
		390	$self->{_status} = [@_];
		391
		392	if ($current == $self) {
		393	push @destroy, $self;
		394	$manager->ready;
		395	&schedule while 1;
		396	} else {
		397	$self->_cancel;
		398	}
		399	}
		400
		401	=item $coroutine->join
		402
		403	Wait until the coroutine terminates and return any values given to the
		404	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		405	from multiple coroutines.
		406
		407	=cut
		408
		409	sub join {
		410	my $self = shift;
		411
		412	unless ($self->{_status}) {
		413	my $current = $current;
		414
		415	push @{$self->{_on_destroy}}, sub {
		416	$current->ready;
		417	undef $current;
		418	};
		419
		420	&schedule while $current;
		421	}
		422
		423	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		424	}
		425
		426	=item $coroutine->on_destroy (\&cb)
		427
		428	Registers a callback that is called when this coroutine gets destroyed,
		429	but before it is joined. The callback gets passed the terminate arguments,
		430	if any.
		431
		432	=cut
		433
		434	sub on_destroy {
		435	my ($self, $cb) = @_;
		436
		437	push @{ $self->{_on_destroy} }, $cb;
		438	}
		439
		440	=item $oldprio = $coroutine->prio ($newprio)
		441
		442	Sets (or gets, if the argument is missing) the priority of the
		443	coroutine. Higher priority coroutines get run before lower priority
		444	coroutines. Priorities are small signed integers (currently -4 .. +3),
		445	that you can refer to using PRIO_xxx constants (use the import tag :prio
		446	to get then):
		447
		448	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		449	3 > 1 > 0 > -1 > -3 > -4
		450
		451	# set priority to HIGH
		452	current->prio(PRIO_HIGH);
		453
		454	The idle coroutine ($Coro::idle) always has a lower priority than any
		455	existing coroutine.
		456
		457	Changing the priority of the current coroutine will take effect immediately,
		458	but changing the priority of coroutines in the ready queue (but not
		459	running) will only take effect after the next schedule (of that
		460	coroutine). This is a bug that will be fixed in some future version.
		461
		462	=item $newprio = $coroutine->nice ($change)
		463
		464	Similar to C<prio>, but subtract the given value from the priority (i.e.
		465	higher values mean lower priority, just as in unix).
		466
		467	=item $olddesc = $coroutine->desc ($newdesc)
		468
		469	Sets (or gets in case the argument is missing) the description for this
		470	coroutine. This is just a free-form string you can associate with a coroutine.
		471
		472	This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
		473	can modify this member directly if you wish.
		474
		475	=item $coroutine->throw ([$scalar])
		476
		477	If C<$throw> is specified and defined, it will be thrown as an exception
		478	inside the coroutine at the next convinient point in time (usually after
		479	it gains control at the next schedule/transfer/cede). Otherwise clears the
		480	exception object.
		481
		482	The exception object will be thrown "as is" with the specified scalar in
		483	C<$@>, i.e. if it is a string, no line number or newline will be appended
		484	(unlike with C<die>).
		485
		486	This can be used as a softer means than C<cancel> to ask a coroutine to
		487	end itself, although there is no guarentee that the exception will lead to
		488	termination, and if the exception isn't caught it might well end the whole
		489	program.
		490
		491	=cut
		492
		493	sub desc {
		494	my $old = $_[0]{desc};
		495	$_[0]{desc} = $_[1] if @_ > 1;
		496	$old;
		497	}
		498
		499	=back
		500
		501	=head2 GLOBAL FUNCTIONS
		502
		503	=over 4
		504
		505	=item Coro::nready
		506
		507	Returns the number of coroutines that are currently in the ready state,
		508	i.e. that can be switched to. The value C<0> means that the only runnable
		509	coroutine is the currently running one, so C<cede> would have no effect,
		510	and C<schedule> would cause a deadlock unless there is an idle handler
		511	that wakes up some coroutines.
		512
		513	=item my $guard = Coro::guard { ... }
		514
		515	This creates and returns a guard object. Nothing happens until the object
		516	gets destroyed, in which case the codeblock given as argument will be
		517	executed. This is useful to free locks or other resources in case of a
		518	runtime error or when the coroutine gets canceled, as in both cases the
		519	guard block will be executed. The guard object supports only one method,
		520	C<< ->cancel >>, which will keep the codeblock from being executed.
		521
		522	Example: set some flag and clear it again when the coroutine gets canceled
		523	or the function returns:
		524
		525	sub do_something {
		526	my $guard = Coro::guard { $busy = 0 };
		527	$busy = 1;
		528
		529	# do something that requires $busy to be true
		530	}
		531
		532	=cut
		533
		534	sub guard(&) {
		535	bless \(my $cb = $_[0]), "Coro::guard"
		536	}
		537
		538	sub Coro::guard::cancel {
		539	${$_[0]} = sub { };
		540	}
		541
		542	sub Coro::guard::DESTROY {
		543	${$_[0]}->();
		544	}
		545
		546
		547	=item unblock_sub { ... }
		548
		549	This utility function takes a BLOCK or code reference and "unblocks" it,
		550	returning the new coderef. This means that the new coderef will return
		551	immediately without blocking, returning nothing, while the original code
		552	ref will be called (with parameters) from within its own coroutine.
		553
		554	The reason this function exists is that many event libraries (such as the
		555	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		556	of thread-safety). This means you must not block within event callbacks,
		557	otherwise you might suffer from crashes or worse.
		558
		559	This function allows your callbacks to block by executing them in another
		560	coroutine where it is safe to block. One example where blocking is handy
		561	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		562	disk.
		563
		564	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		565	creating event callbacks that want to block.
		566
		567	=cut
		568
		569	our @unblock_queue;
		570
		571	# we create a special coro because we want to cede,
		572	# to reduce pressure on the coro pool (because most callbacks
		573	# return immediately and can be reused) and because we cannot cede
		574	# inside an event callback.
		575	our $unblock_scheduler = new Coro sub {
		576	while () {
		577	while (my $cb = pop @unblock_queue) {
		578	# this is an inlined copy of async_pool
		579	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		580
		581	$coro->{_invoke} = $cb;
		582	$coro->ready;
		583	cede; # for short-lived callbacks, this reduces pressure on the coro pool
94	}	584	}
95	} while (1);	585	schedule; # sleep well
96	}, $class;	586	}
97	}	587	};
		588	$unblock_scheduler->desc ("[unblock_sub scheduler]");
98		589
99	=item $coro->resume	590	sub unblock_sub(&) {
		591	my $cb = shift;
100		592
101	Resume execution at the given coroutine.	593	sub {
102		594	unshift @unblock_queue, [$cb, @_];
103	=cut	595	$unblock_scheduler->ready;
104		596	}
105	my $prev;
106
107	sub resume {
108	$prev = $current; $current = $_[0];
109	_transfer($prev, $current);
110	}	597	}
		598
		599	=back
		600
		601	=cut
111		602
112	1;	603	1;
113		604
114	=back	605	=head1 BUGS/LIMITATIONS
115		606
116	=head1 BUGS	607	- you must make very sure that no coro is still active on global
		608	destruction. very bad things might happen otherwise (usually segfaults).
117		609
118	This module has not yet been extensively tested.	610	- this module is not thread-safe. You should only ever use this module
		611	from the same thread (this requirement might be loosened in the future
		612	to allow per-thread schedulers, but Coro::State does not yet allow
		613	this).
119		614
120	=head1 SEE ALSO	615	=head1 SEE ALSO
121		616
122	L<Coro::Process>, L<Coro::Signal>.	617	Lower level Configuration, Coroutine Environment: L<Coro::State>.
		618
		619	Debugging: L<Coro::Debug>.
		620
		621	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
		622
		623	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		624
		625	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>.
		626
		627	Compatibility: L<Coro::LWP>, L<Coro::Storable>, L<Coro::Select>.
		628
		629	Embedding: L<Coro::MakeMaker>.
123		630
124	=head1 AUTHOR	631	=head1 AUTHOR
125		632
126	Marc Lehmann <pcg@goof.com>	633	Marc Lehmann <schmorp@schmorp.de>
127	http://www.goof.com/pcg/marc/	634	http://home.schmorp.de/
128		635
129	=cut	636	=cut
130		637

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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 1.178 by root, Thu Apr 17 22:33:10 2008 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 1.178 by root, Thu Apr 17 22:33:10 2008 UTC