[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 1.163 by root, Mon Dec 17 06:36:24 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);	11	print "2\n";
12	print "in coroutine again, switching back\n";	12	cede; # yield back to main
13	$new->transfer($main);	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	$main = new Coro;	20	# use locking
		21	my $lock = new Coro::Semaphore;
		22	my $locked;
17		23
18	print "in main, switching to coroutine\n";	24	$lock->down;
19	$main->transfer($new);	25	$locked = 1;
20	print "back in main, switch to coroutine again\n";	26	$lock->up;
21	$main->transfer($new);
22	print "back in main\n";
23		27
24	=head1 DESCRIPTION	28	=head1 DESCRIPTION
25		29
26	This module implements coroutines. Coroutines, similar to continuations,	30	This module collection manages coroutines. Coroutines are similar
27	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
28	threads this, only voluntary switching is used so locking problems are	32	machines. The specific flavor of coroutine used in this module also
29	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.
30		37
31	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
32	low-level functionality. See L<Coro::Process> and related modules for a	39	very slow and memory-intensive emulation of processes using threads. This
33	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 $VERSION = '4.32';
		63
		64	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
		65	our %EXPORT_TAGS = (
		66	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		67	);
		68	our @EXPORT_OK = (@{$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	}
34		103
35	=over 4	104	=over 4
36		105
37	=cut	106	=item $main
38		107
39	package Coro;	108	This coroutine represents the main program.
40		109
41	BEGIN {	110	=cut
42	$VERSION = 0.03;
43		111
		112	$main = new Coro;
		113
		114	=item $current (or as function: current)
		115
		116	The current coroutine (the last coroutine switched to). The initial value
		117	is C<$main> (of course).
		118
		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.
		122
		123	=cut
		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 {
44	require XSLoader;	151	require Carp;
45	XSLoader::load Coro, $VERSION;	152	Carp::croak ("FATAL: deadlock detected");
46	}	153	};
47		154
48	=item $coro = new [$coderef [, @args]]	155	sub _cancel {
		156	my ($self) = @_;
49		157
50	Create a new coroutine and return it. The first C<transfer> call to this	158	# free coroutine data and mark as destructed
51	coroutine will start execution at the given coderef. If, the subroutine	159	$self->_destroy
52	returns it will be executed again.	160	or return;
53		161
54	If the coderef is omitted this function will create a new "empty"	162	# call all destruction callbacks
55	coroutine, i.e. a coroutine that cannot be transfered to but can be used	163	$_->(@{$self->{_status}})
56	to save the current coroutine in.	164	for @{(delete $self->{_on_destroy}) \|\| []};
		165	}
57		166
		167	# this coroutine is necessary because a coroutine
		168	# cannot destroy itself.
		169	my @destroy;
		170	my $manager;
		171
		172	$manager = new Coro sub {
		173	while () {
		174	(shift @destroy)->_cancel
		175	while @destroy;
		176
		177	&schedule;
		178	}
		179	};
		180	$manager->desc ("[coro manager]");
		181	$manager->prio (PRIO_MAX);
		182
		183	# static methods. not really.
		184
		185	=back
		186
		187	=head2 STATIC METHODS
		188
		189	Static methods are actually functions that operate on the current coroutine only.
		190
		191	=over 4
		192
		193	=item async { ... } [@args...]
		194
		195	Create a new asynchronous coroutine and return it's coroutine object
		196	(usually unused). When the sub returns the new coroutine is automatically
		197	terminated.
		198
		199	See the C<Coro::State::new> constructor for info about the coroutine
		200	environment in which coroutines run.
		201
		202	Calling C<exit> in a coroutine will do the same as calling exit outside
		203	the coroutine. Likewise, when the coroutine dies, the program will exit,
		204	just as it would in the main program.
		205
		206	# create a new coroutine that just prints its arguments
		207	async {
		208	print "@_\n";
		209	} 1,2,3,4;
		210
58	=cut	211	=cut
		212
		213	sub async(&@) {
		214	my $coro = new Coro @_;
		215	$coro->ready;
		216	$coro
		217	}
		218
		219	=item async_pool { ... } [@args...]
		220
		221	Similar to C<async>, but uses a coroutine pool, so you should not call
		222	terminate or join (although you are allowed to), and you get a coroutine
		223	that might have executed other code already (which can be good or bad :).
		224
		225	Also, the block is executed in an C<eval> context and a warning will be
		226	issued in case of an exception instead of terminating the program, as
		227	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		228	will not work in the expected way, unless you call terminate or cancel,
		229	which somehow defeats the purpose of pooling.
		230
		231	The priority will be reset to C<0> after each job, tracing will be
		232	disabled, the description will be reset and the default output filehandle
		233	gets restored, so you can change alkl these. Otherwise the coroutine will
		234	be re-used "as-is": most notably if you change other per-coroutine global
		235	stuff such as C<$/> you need to revert that change, which is most simply
		236	done by using local as in C< local $/ >.
		237
		238	The pool size is limited to 8 idle coroutines (this can be adjusted by
		239	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
		240	required.
		241
		242	If you are concerned about pooled coroutines growing a lot because a
		243	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		244	{ terminate }> once per second or so to slowly replenish the pool. In
		245	addition to that, when the stacks used by a handler grows larger than 16kb
		246	(adjustable with $Coro::POOL_RSS) it will also exit.
		247
		248	=cut
		249
		250	our $POOL_SIZE = 8;
		251	our $POOL_RSS = 16 * 1024;
		252	our @async_pool;
		253
		254	sub pool_handler {
		255	my $cb;
		256
		257	while () {
		258	eval {
		259	while () {
		260	_pool_1 $cb;
		261	&$cb;
		262	_pool_2 $cb;
		263	&schedule;
		264	}
		265	};
		266
		267	last if $@ eq "\3async_pool terminate\2\n";
		268	warn $@ if $@;
		269	}
		270	}
		271
		272	sub async_pool(&@) {
		273	# this is also inlined into the unlock_scheduler
		274	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		275
		276	$coro->{_invoke} = [@_];
		277	$coro->ready;
		278
		279	$coro
		280	}
		281
		282	=item schedule
		283
		284	Calls the scheduler. Please note that the current coroutine will not be put
		285	into the ready queue, so calling this function usually means you will
		286	never be called again unless something else (e.g. an event handler) calls
		287	ready.
		288
		289	The canonical way to wait on external events is this:
		290
		291	{
		292	# remember current coroutine
		293	my $current = $Coro::current;
		294
		295	# register a hypothetical event handler
		296	on_event_invoke sub {
		297	# wake up sleeping coroutine
		298	$current->ready;
		299	undef $current;
		300	};
		301
		302	# call schedule until event occurred.
		303	# in case we are woken up for other reasons
		304	# (current still defined), loop.
		305	Coro::schedule while $current;
		306	}
		307
		308	=item cede
		309
		310	"Cede" to other coroutines. This function puts the current coroutine into the
		311	ready queue and calls C<schedule>, which has the effect of giving up the
		312	current "timeslice" to other coroutines of the same or higher priority.
		313
		314	=item Coro::cede_notself
		315
		316	Works like cede, but is not exported by default and will cede to any
		317	coroutine, regardless of priority, once.
		318
		319	=item terminate [arg...]
		320
		321	Terminates the current coroutine with the given status values (see L<cancel>).
		322
		323	=item killall
		324
		325	Kills/terminates/cancels all coroutines except the currently running
		326	one. This is useful after a fork, either in the child or the parent, as
		327	usually only one of them should inherit the running coroutines.
		328
		329	=cut
		330
		331	sub terminate {
		332	$current->cancel (@_);
		333	}
		334
		335	sub killall {
		336	for (Coro::State::list) {
		337	$_->cancel
		338	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		339	}
		340	}
		341
		342	=back
		343
		344	# dynamic methods
		345
		346	=head2 COROUTINE METHODS
		347
		348	These are the methods you can call on coroutine objects.
		349
		350	=over 4
		351
		352	=item new Coro \&sub [, @args...]
		353
		354	Create a new coroutine and return it. When the sub returns the coroutine
		355	automatically terminates as if C<terminate> with the returned values were
		356	called. To make the coroutine run you must first put it into the ready queue
		357	by calling the ready method.
		358
		359	See C<async> and C<Coro::State::new> for additional info about the
		360	coroutine environment.
		361
		362	=cut
		363
		364	sub _run_coro {
		365	terminate &{+shift};
		366	}
59		367
60	sub new {	368	sub new {
61	my $class = $_[0];	369	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		370
75	=item $prev->transfer($next)	371	$class->SUPER::new (\&_run_coro, @_)
		372	}
76		373
77	Save the state of the current subroutine in C<$prev> and switch to the	374	=item $success = $coroutine->ready
78	coroutine saved in C<$next>.
79		375
80	The "state" of a subroutine only ever includes scope, i.e. lexical	376	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	377	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	378	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		379
88	The easiest way to do this is to create your own scheduling primitive like this:	380	=item $is_ready = $coroutine->is_ready
89		381
90	sub schedule {	382	Return wether the coroutine is currently the ready queue or not,
91	local ($_, $@, ...);	383
92	$old->transfer($new);	384	=item $coroutine->cancel (arg...)
		385
		386	Terminates the given coroutine and makes it return the given arguments as
		387	status (default: the empty list). Never returns if the coroutine is the
		388	current coroutine.
		389
		390	=cut
		391
		392	sub cancel {
		393	my $self = shift;
		394	$self->{_status} = [@_];
		395
		396	if ($current == $self) {
		397	push @destroy, $self;
		398	$manager->ready;
		399	&schedule while 1;
		400	} else {
		401	$self->_cancel;
93	}	402	}
94
95	=cut
96
97	# I call the _transfer function from a perl function
98	# because that way perl saves all important things on
99	# the stack. Actually, I'd do it from within XS, but
100	# I couldn't get it to work.
101	sub transfer {
102	_transfer($_[0], $_[1]);
103	}	403	}
104		404
105	=item $error, $error_msg, $error_coro	405	=item $coroutine->join
106		406
107	This coroutine will be called on fatal errors. C<$error_msg> and	407	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	408	C<terminate> or C<cancel> functions. C<join> can be called concurrently
109	(NOT an object) respectively. This API might change.	409	from multiple coroutines.
110		410
111	=cut	411	=cut
112		412
113	$error_msg =	413	sub join {
114	$error_coro = undef;	414	my $self = shift;
115		415
116	$error = _newprocess {	416	unless ($self->{_status}) {
117	print STDERR "FATAL: $error_msg\nprogram aborted\n";	417	my $current = $current;
118	exit 50;	418
		419	push @{$self->{_on_destroy}}, sub {
		420	$current->ready;
		421	undef $current;
		422	};
		423
		424	&schedule while $current;
		425	}
		426
		427	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		428	}
		429
		430	=item $coroutine->on_destroy (\&cb)
		431
		432	Registers a callback that is called when this coroutine gets destroyed,
		433	but before it is joined. The callback gets passed the terminate arguments,
		434	if any.
		435
		436	=cut
		437
		438	sub on_destroy {
		439	my ($self, $cb) = @_;
		440
		441	push @{ $self->{_on_destroy} }, $cb;
		442	}
		443
		444	=item $oldprio = $coroutine->prio ($newprio)
		445
		446	Sets (or gets, if the argument is missing) the priority of the
		447	coroutine. Higher priority coroutines get run before lower priority
		448	coroutines. Priorities are small signed integers (currently -4 .. +3),
		449	that you can refer to using PRIO_xxx constants (use the import tag :prio
		450	to get then):
		451
		452	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		453	3 > 1 > 0 > -1 > -3 > -4
		454
		455	# set priority to HIGH
		456	current->prio(PRIO_HIGH);
		457
		458	The idle coroutine ($Coro::idle) always has a lower priority than any
		459	existing coroutine.
		460
		461	Changing the priority of the current coroutine will take effect immediately,
		462	but changing the priority of coroutines in the ready queue (but not
		463	running) will only take effect after the next schedule (of that
		464	coroutine). This is a bug that will be fixed in some future version.
		465
		466	=item $newprio = $coroutine->nice ($change)
		467
		468	Similar to C<prio>, but subtract the given value from the priority (i.e.
		469	higher values mean lower priority, just as in unix).
		470
		471	=item $olddesc = $coroutine->desc ($newdesc)
		472
		473	Sets (or gets in case the argument is missing) the description for this
		474	coroutine. This is just a free-form string you can associate with a coroutine.
		475
		476	This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
		477	can modify this member directly if you wish.
		478
		479	=item $coroutine->throw ([$scalar])
		480
		481	If C<$throw> is specified and defined, it will be thrown as an exception
		482	inside the coroutine at the next convinient point in time (usually after
		483	it gains control at the next schedule/transfer/cede). Otherwise clears the
		484	exception object.
		485
		486	The exception object will be thrown "as is" with the specified scalar in
		487	C<$@>, i.e. if it is a string, no line number or newline will be appended
		488	(unlike with C<die>).
		489
		490	This can be used as a softer means than C<cancel> to ask a coroutine to
		491	end itself, although there is no guarentee that the exception will lead to
		492	termination, and if the exception isn't caught it might well end the whole
		493	program.
		494
		495	=cut
		496
		497	sub desc {
		498	my $old = $_[0]{desc};
		499	$_[0]{desc} = $_[1] if @_ > 1;
		500	$old;
		501	}
		502
		503	=back
		504
		505	=head2 GLOBAL FUNCTIONS
		506
		507	=over 4
		508
		509	=item Coro::nready
		510
		511	Returns the number of coroutines that are currently in the ready state,
		512	i.e. that can be switched to. The value C<0> means that the only runnable
		513	coroutine is the currently running one, so C<cede> would have no effect,
		514	and C<schedule> would cause a deadlock unless there is an idle handler
		515	that wakes up some coroutines.
		516
		517	=item my $guard = Coro::guard { ... }
		518
		519	This creates and returns a guard object. Nothing happens until the object
		520	gets destroyed, in which case the codeblock given as argument will be
		521	executed. This is useful to free locks or other resources in case of a
		522	runtime error or when the coroutine gets canceled, as in both cases the
		523	guard block will be executed. The guard object supports only one method,
		524	C<< ->cancel >>, which will keep the codeblock from being executed.
		525
		526	Example: set some flag and clear it again when the coroutine gets canceled
		527	or the function returns:
		528
		529	sub do_something {
		530	my $guard = Coro::guard { $busy = 0 };
		531	$busy = 1;
		532
		533	# do something that requires $busy to be true
		534	}
		535
		536	=cut
		537
		538	sub guard(&) {
		539	bless \(my $cb = $_[0]), "Coro::guard"
		540	}
		541
		542	sub Coro::guard::cancel {
		543	${$_[0]} = sub { };
		544	}
		545
		546	sub Coro::guard::DESTROY {
		547	${$_[0]}->();
		548	}
		549
		550
		551	=item unblock_sub { ... }
		552
		553	This utility function takes a BLOCK or code reference and "unblocks" it,
		554	returning the new coderef. This means that the new coderef will return
		555	immediately without blocking, returning nothing, while the original code
		556	ref will be called (with parameters) from within its own coroutine.
		557
		558	The reason this function exists is that many event libraries (such as the
		559	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		560	of thread-safety). This means you must not block within event callbacks,
		561	otherwise you might suffer from crashes or worse.
		562
		563	This function allows your callbacks to block by executing them in another
		564	coroutine where it is safe to block. One example where blocking is handy
		565	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		566	disk.
		567
		568	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		569	creating event callbacks that want to block.
		570
		571	=cut
		572
		573	our @unblock_queue;
		574
		575	# we create a special coro because we want to cede,
		576	# to reduce pressure on the coro pool (because most callbacks
		577	# return immediately and can be reused) and because we cannot cede
		578	# inside an event callback.
		579	our $unblock_scheduler = new Coro sub {
		580	while () {
		581	while (my $cb = pop @unblock_queue) {
		582	# this is an inlined copy of async_pool
		583	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		584
		585	$coro->{_invoke} = $cb;
		586	$coro->ready;
		587	cede; # for short-lived callbacks, this reduces pressure on the coro pool
		588	}
		589	schedule; # sleep well
		590	}
119	};	591	};
		592	$unblock_scheduler->desc ("[unblock_sub scheduler]");
		593
		594	sub unblock_sub(&) {
		595	my $cb = shift;
		596
		597	sub {
		598	unshift @unblock_queue, [$cb, @_];
		599	$unblock_scheduler->ready;
		600	}
		601	}
		602
		603	=back
		604
		605	=cut
120		606
121	1;	607	1;
122		608
123	=back	609	=head1 BUGS/LIMITATIONS
124		610
125	=head1 BUGS	611	- you must make very sure that no coro is still active on global
		612	destruction. very bad things might happen otherwise (usually segfaults).
126		613
127	This module has not yet been extensively tested.	614	- this module is not thread-safe. You should only ever use this module
		615	from the same thread (this requirement might be loosened in the future
		616	to allow per-thread schedulers, but Coro::State does not yet allow
		617	this).
128		618
129	=head1 SEE ALSO	619	=head1 SEE ALSO
130		620
131	L<Coro::Process>, L<Coro::Signal>.	621	Lower level Configuration, Coroutine Environment: L<Coro::State>.
		622
		623	Debugging: L<Coro::Debug>.
		624
		625	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
		626
		627	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		628
		629	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>.
		630
		631	Compatibility: L<Coro::LWP>, L<Coro::Storable>, L<Coro::Select>.
		632
		633	Embedding: L<Coro::MakeMaker>.
132		634
133	=head1 AUTHOR	635	=head1 AUTHOR
134		636
135	Marc Lehmann <pcg@goof.com>	637	Marc Lehmann <schmorp@schmorp.de>
136	http://www.goof.com/pcg/marc/	638	http://home.schmorp.de/
137		639
138	=cut	640	=cut
139		641

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing Coro/Coro.pm (file contents): Revision 1.7 by root, Fri Jul 13 13:05:38 2001 UTC vs. Revision 1.163 by root, Mon Dec 17 06:36:24 2007 UTC

Diff Legend

Comparing Coro/Coro.pm (file contents):
Revision 1.7 by root, Fri Jul 13 13:05:38 2001 UTC vs.
Revision 1.163 by root, Mon Dec 17 06:36:24 2007 UTC