[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 1.152 by root, Sun Oct 7 13:53:37 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 $VERSION = '4.1';
		63
		64	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
		65	our %EXPORT_TAGS = (
		66	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		67	);
		68	our @EXPORT_OK = (@{$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	Returns true if at least one coroutine switch has happened.
		315
		316	=item Coro::cede_notself
		317
		318	Works like cede, but is not exported by default and will cede to any
		319	coroutine, regardless of priority, once.
		320
		321	Returns true if at least one coroutine switch has happened.
		322
		323	=item terminate [arg...]
		324
		325	Terminates the current coroutine with the given status values (see L<cancel>).
		326
		327	=item killall
		328
		329	Kills/terminates/cancels all coroutines except the currently running
		330	one. This is useful after a fork, either in the child or the parent, as
		331	usually only one of them should inherit the running coroutines.
		332
		333	=cut
		334
		335	sub terminate {
		336	$current->cancel (@_);
		337	}
		338
		339	sub killall {
		340	for (Coro::State::list) {
		341	$_->cancel
		342	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		343	}
		344	}
		345
		346	=back
		347
		348	# dynamic methods
		349
		350	=head2 COROUTINE METHODS
		351
		352	These are the methods you can call on coroutine objects.
		353
		354	=over 4
		355
		356	=item new Coro \&sub [, @args...]
		357
		358	Create a new coroutine and return it. When the sub returns the coroutine
		359	automatically terminates as if C<terminate> with the returned values were
		360	called. To make the coroutine run you must first put it into the ready queue
		361	by calling the ready method.
		362
		363	See C<async> and C<Coro::State::new> for additional info about the
		364	coroutine environment.
		365
		366	=cut
		367
		368	sub _run_coro {
		369	terminate &{+shift};
		370	}
59		371
60	sub new {	372	sub new {
61	my $class = $_[0];	373	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		374
75	=item $prev->transfer($next)	375	$class->SUPER::new (\&_run_coro, @_)
		376	}
76		377
77	Save the state of the current subroutine in C<$prev> and switch to the	378	=item $success = $coroutine->ready
78	coroutine saved in C<$next>.
79		379
80	The "state" of a subroutine only ever includes scope, i.e. lexical	380	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	381	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	382	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		383
88	The easiest way to do this is to create your own scheduling primitive like this:	384	=item $is_ready = $coroutine->is_ready
89		385
90	sub schedule {	386	Return wether the coroutine is currently the ready queue or not,
91	local ($_, $@, ...);	387
92	$old->transfer($new);	388	=item $coroutine->cancel (arg...)
		389
		390	Terminates the given coroutine and makes it return the given arguments as
		391	status (default: the empty list). Never returns if the coroutine is the
		392	current coroutine.
		393
		394	=cut
		395
		396	sub cancel {
		397	my $self = shift;
		398	$self->{_status} = [@_];
		399
		400	if ($current == $self) {
		401	push @destroy, $self;
		402	$manager->ready;
		403	&schedule while 1;
		404	} else {
		405	$self->_cancel;
93	}	406	}
94
95	=cut
96
97	# I call the _transfer function from a perl function
98	# because that way perl saves all important things on
99	# the stack. Actually, I'd do it from within XS, but
100	# I couldn't get it to work.
101	sub transfer {
102	_transfer($_[0], $_[1]);
103	}	407	}
104		408
105	=item $error, $error_msg, $error_coro	409	=item $coroutine->join
106		410
107	This coroutine will be called on fatal errors. C<$error_msg> and	411	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	412	C<terminate> or C<cancel> functions. C<join> can be called concurrently
109	(NOT an object) respectively. This API might change.	413	from multiple coroutines.
110		414
111	=cut	415	=cut
112		416
113	$error_msg =	417	sub join {
114	$error_coro = undef;	418	my $self = shift;
115		419
116	$error = _newprocess {	420	unless ($self->{_status}) {
117	print STDERR "FATAL: $error_msg\nprogram aborted\n";	421	my $current = $current;
118	exit 50;	422
		423	push @{$self->{_on_destroy}}, sub {
		424	$current->ready;
		425	undef $current;
		426	};
		427
		428	&schedule while $current;
		429	}
		430
		431	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		432	}
		433
		434	=item $coroutine->on_destroy (\&cb)
		435
		436	Registers a callback that is called when this coroutine gets destroyed,
		437	but before it is joined. The callback gets passed the terminate arguments,
		438	if any.
		439
		440	=cut
		441
		442	sub on_destroy {
		443	my ($self, $cb) = @_;
		444
		445	push @{ $self->{_on_destroy} }, $cb;
		446	}
		447
		448	=item $oldprio = $coroutine->prio ($newprio)
		449
		450	Sets (or gets, if the argument is missing) the priority of the
		451	coroutine. Higher priority coroutines get run before lower priority
		452	coroutines. Priorities are small signed integers (currently -4 .. +3),
		453	that you can refer to using PRIO_xxx constants (use the import tag :prio
		454	to get then):
		455
		456	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		457	3 > 1 > 0 > -1 > -3 > -4
		458
		459	# set priority to HIGH
		460	current->prio(PRIO_HIGH);
		461
		462	The idle coroutine ($Coro::idle) always has a lower priority than any
		463	existing coroutine.
		464
		465	Changing the priority of the current coroutine will take effect immediately,
		466	but changing the priority of coroutines in the ready queue (but not
		467	running) will only take effect after the next schedule (of that
		468	coroutine). This is a bug that will be fixed in some future version.
		469
		470	=item $newprio = $coroutine->nice ($change)
		471
		472	Similar to C<prio>, but subtract the given value from the priority (i.e.
		473	higher values mean lower priority, just as in unix).
		474
		475	=item $olddesc = $coroutine->desc ($newdesc)
		476
		477	Sets (or gets in case the argument is missing) the description for this
		478	coroutine. This is just a free-form string you can associate with a coroutine.
		479
		480	This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
		481	can modify this member directly if you wish.
		482
		483	=item $coroutine->throw ([$scalar])
		484
		485	If C<$throw> is specified and defined, it will be thrown as an exception
		486	inside the coroutine at the next convinient point in time (usually after
		487	it gains control at the next schedule/transfer/cede). Otherwise clears the
		488	exception object.
		489
		490	The exception object will be thrown "as is" with the specified scalar in
		491	C<$@>, i.e. if it is a string, no line number or newline will be appended
		492	(unlike with C<die>).
		493
		494	This can be used as a softer means than C<cancel> to ask a coroutine to
		495	end itself, although there is no guarentee that the exception will lead to
		496	termination, and if the exception isn't caught it might well end the whole
		497	program.
		498
		499	=cut
		500
		501	sub desc {
		502	my $old = $_[0]{desc};
		503	$_[0]{desc} = $_[1] if @_ > 1;
		504	$old;
		505	}
		506
		507	=back
		508
		509	=head2 GLOBAL FUNCTIONS
		510
		511	=over 4
		512
		513	=item Coro::nready
		514
		515	Returns the number of coroutines that are currently in the ready state,
		516	i.e. that can be switched to. The value C<0> means that the only runnable
		517	coroutine is the currently running one, so C<cede> would have no effect,
		518	and C<schedule> would cause a deadlock unless there is an idle handler
		519	that wakes up some coroutines.
		520
		521	=item my $guard = Coro::guard { ... }
		522
		523	This creates and returns a guard object. Nothing happens until the object
		524	gets destroyed, in which case the codeblock given as argument will be
		525	executed. This is useful to free locks or other resources in case of a
		526	runtime error or when the coroutine gets canceled, as in both cases the
		527	guard block will be executed. The guard object supports only one method,
		528	C<< ->cancel >>, which will keep the codeblock from being executed.
		529
		530	Example: set some flag and clear it again when the coroutine gets canceled
		531	or the function returns:
		532
		533	sub do_something {
		534	my $guard = Coro::guard { $busy = 0 };
		535	$busy = 1;
		536
		537	# do something that requires $busy to be true
		538	}
		539
		540	=cut
		541
		542	sub guard(&) {
		543	bless \(my $cb = $_[0]), "Coro::guard"
		544	}
		545
		546	sub Coro::guard::cancel {
		547	${$_[0]} = sub { };
		548	}
		549
		550	sub Coro::guard::DESTROY {
		551	${$_[0]}->();
		552	}
		553
		554
		555	=item unblock_sub { ... }
		556
		557	This utility function takes a BLOCK or code reference and "unblocks" it,
		558	returning the new coderef. This means that the new coderef will return
		559	immediately without blocking, returning nothing, while the original code
		560	ref will be called (with parameters) from within its own coroutine.
		561
		562	The reason this function exists is that many event libraries (such as the
		563	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		564	of thread-safety). This means you must not block within event callbacks,
		565	otherwise you might suffer from crashes or worse.
		566
		567	This function allows your callbacks to block by executing them in another
		568	coroutine where it is safe to block. One example where blocking is handy
		569	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		570	disk.
		571
		572	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		573	creating event callbacks that want to block.
		574
		575	=cut
		576
		577	our @unblock_queue;
		578
		579	# we create a special coro because we want to cede,
		580	# to reduce pressure on the coro pool (because most callbacks
		581	# return immediately and can be reused) and because we cannot cede
		582	# inside an event callback.
		583	our $unblock_scheduler = new Coro sub {
		584	while () {
		585	while (my $cb = pop @unblock_queue) {
		586	# this is an inlined copy of async_pool
		587	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		588
		589	$coro->{_invoke} = $cb;
		590	$coro->ready;
		591	cede; # for short-lived callbacks, this reduces pressure on the coro pool
		592	}
		593	schedule; # sleep well
		594	}
119	};	595	};
		596	$unblock_scheduler->desc ("[unblock_sub scheduler]");
		597
		598	sub unblock_sub(&) {
		599	my $cb = shift;
		600
		601	sub {
		602	unshift @unblock_queue, [$cb, @_];
		603	$unblock_scheduler->ready;
		604	}
		605	}
		606
		607	=back
		608
		609	=cut
120		610
121	1;	611	1;
122		612
123	=back	613	=head1 BUGS/LIMITATIONS
124		614
125	=head1 BUGS	615	- you must make very sure that no coro is still active on global
		616	destruction. very bad things might happen otherwise (usually segfaults).
126		617
127	This module has not yet been extensively tested.	618	- this module is not thread-safe. You should only ever use this module
		619	from the same thread (this requirement might be loosened in the future
		620	to allow per-thread schedulers, but Coro::State does not yet allow
		621	this).
128		622
129	=head1 SEE ALSO	623	=head1 SEE ALSO
130		624
131	L<Coro::Process>, L<Coro::Signal>.	625	Lower level Configuration, Coroutine Environment: L<Coro::State>.
		626
		627	Debugging: L<Coro::Debug>.
		628
		629	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
		630
		631	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		632
		633	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>.
		634
		635	Compatibility: L<Coro::LWP>, L<Coro::Storable>, L<Coro::Select>.
		636
		637	Embedding: L<Coro:MakeMaker>.
132		638
133	=head1 AUTHOR	639	=head1 AUTHOR
134		640
135	Marc Lehmann <pcg@goof.com>	641	Marc Lehmann <schmorp@schmorp.de>
136	http://www.goof.com/pcg/marc/	642	http://home.schmorp.de/
137		643
138	=cut	644	=cut
139		645

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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 1.152 by root, Sun Oct 7 13:53:37 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 1.152 by root, Sun Oct 7 13:53:37 2007 UTC