[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 1.129 by root, Wed Sep 19 22:33:08 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 $VERSION = '3.7';
		56
		57	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
		58	our %EXPORT_TAGS = (
		59	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		60	);
		61	our @EXPORT_OK = (@{$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	# maybe some other module used Coro::Specific before...
		119	$main->{specific} = $current->{specific}
		120	if $current;
		121
		122	_set_current $main;
		123
		124	sub current() { $current }
		125
		126	=item $idle
		127
		128	A callback that is called whenever the scheduler finds no ready coroutines
		129	to run. The default implementation prints "FATAL: deadlock detected" and
		130	exits, because the program has no other way to continue.
		131
		132	This hook is overwritten by modules such as C<Coro::Timer> and
		133	C<Coro::Event> to wait on an external event that hopefully wake up a
		134	coroutine so the scheduler can run it.
		135
		136	Please note that if your callback recursively invokes perl (e.g. for event
		137	handlers), then it must be prepared to be called recursively.
		138
		139	=cut
		140
		141	$idle = sub {
44	require XSLoader;	142	require Carp;
45	XSLoader::load Coro, $VERSION;	143	Carp::croak ("FATAL: deadlock detected");
46	}	144	};
47		145
48	=item $coro = new [$coderef [, @args]]	146	sub _cancel {
		147	my ($self) = @_;
49		148
50	Create a new coroutine and return it. The first C<transfer> call to this	149	# free coroutine data and mark as destructed
51	coroutine will start execution at the given coderef. If, the subroutine	150	$self->_destroy
52	returns it will be executed again.	151	or return;
53		152
54	If the coderef is omitted this function will create a new "empty"	153	# call all destruction callbacks
55	coroutine, i.e. a coroutine that cannot be transfered to but can be used	154	$_->(@{$self->{status}})
56	to save the current coroutine in.	155	for @{(delete $self->{destroy_cb}) \|\| []};
		156	}
57		157
		158	# this coroutine is necessary because a coroutine
		159	# cannot destroy itself.
		160	my @destroy;
		161	my $manager;
		162
		163	$manager = new Coro sub {
		164	$current->desc ("[coro manager]");
		165
		166	while () {
		167	(shift @destroy)->_cancel
		168	while @destroy;
		169
		170	&schedule;
		171	}
		172	};
		173
		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	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
58	=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.
		231
		232	=cut
		233
		234	our $POOL_SIZE = 8;
		235	our @pool;
		236
		237	sub pool_handler {
		238	while () {
		239	$current->{desc} = "[async_pool]";
		240
		241	eval {
		242	my ($cb, @arg) = @{ delete $current->{_invoke} or return };
		243	$cb->(@arg);
		244	};
		245	warn $@ if $@;
		246
		247	last if @pool >= $POOL_SIZE;
		248
		249	push @pool, $current;
		250	$current->{desc} = "[async_pool idle]";
		251	$current->save (Coro::State::SAVE_DEF);
		252	$current->prio (0);
		253	schedule;
		254	}
		255	}
		256
		257	sub async_pool(&@) {
		258	# this is also inlined into the unlock_scheduler
		259	my $coro = (pop @pool) \|\| new Coro \&pool_handler;;
		260
		261	$coro->{_invoke} = [@_];
		262	$coro->ready;
		263
		264	$coro
		265	}
		266
		267	=item schedule
		268
		269	Calls the scheduler. Please note that the current coroutine will not be put
		270	into the ready queue, so calling this function usually means you will
		271	never be called again unless something else (e.g. an event handler) calls
		272	ready.
		273
		274	The canonical way to wait on external events is this:
		275
		276	{
		277	# remember current coroutine
		278	my $current = $Coro::current;
		279
		280	# register a hypothetical event handler
		281	on_event_invoke sub {
		282	# wake up sleeping coroutine
		283	$current->ready;
		284	undef $current;
		285	};
		286
		287	# call schedule until event occurred.
		288	# in case we are woken up for other reasons
		289	# (current still defined), loop.
		290	Coro::schedule while $current;
		291	}
		292
		293	=item cede
		294
		295	"Cede" to other coroutines. This function puts the current coroutine into the
		296	ready queue and calls C<schedule>, which has the effect of giving up the
		297	current "timeslice" to other coroutines of the same or higher priority.
		298
		299	Returns true if at least one coroutine switch has happened.
		300
		301	=item Coro::cede_notself
		302
		303	Works like cede, but is not exported by default and will cede to any
		304	coroutine, regardless of priority, once.
		305
		306	Returns true if at least one coroutine switch has happened.
		307
		308	=item terminate [arg...]
		309
		310	Terminates the current coroutine with the given status values (see L<cancel>).
		311
		312	=cut
		313
		314	sub terminate {
		315	$current->cancel (@_);
		316	}
		317
		318	=back
		319
		320	# dynamic methods
		321
		322	=head2 COROUTINE METHODS
		323
		324	These are the methods you can call on coroutine objects.
		325
		326	=over 4
		327
		328	=item new Coro \&sub [, @args...]
		329
		330	Create a new coroutine and return it. When the sub returns the coroutine
		331	automatically terminates as if C<terminate> with the returned values were
		332	called. To make the coroutine run you must first put it into the ready queue
		333	by calling the ready method.
		334
		335	See C<async> for additional discussion.
		336
		337	=cut
		338
		339	sub _run_coro {
		340	terminate &{+shift};
		341	}
59		342
60	sub new {	343	sub new {
61	my $class = $_[0];	344	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		345
75	=item $prev->transfer($next)	346	$class->SUPER::new (\&_run_coro, @_)
		347	}
76		348
77	Save the state of the current subroutine in C<$prev> and switch to the	349	=item $success = $coroutine->ready
78	coroutine saved in C<$next>.
79		350
80	The "state" of a subroutine only ever includes scope, i.e. lexical	351	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	352	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	353	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		354
88	The easiest way to do this is to create your own scheduling primitive like this:	355	=item $is_ready = $coroutine->is_ready
89		356
90	sub schedule {	357	Return wether the coroutine is currently the ready queue or not,
91	local ($_, $@, ...);	358
92	$old->transfer($new);	359	=item $coroutine->cancel (arg...)
		360
		361	Terminates the given coroutine and makes it return the given arguments as
		362	status (default: the empty list). Never returns if the coroutine is the
		363	current coroutine.
		364
		365	=cut
		366
		367	sub cancel {
		368	my $self = shift;
		369	$self->{status} = [@_];
		370
		371	if ($current == $self) {
		372	push @destroy, $self;
		373	$manager->ready;
		374	&schedule while 1;
		375	} else {
		376	$self->_cancel;
93	}	377	}
94
95	=cut
96
97	# I call the _transfer function from a perl function
98	# because that way perl saves all important things on
99	# the stack. Actually, I'd do it from within XS, but
100	# I couldn't get it to work.
101	sub transfer {
102	_transfer($_[0], $_[1]);
103	}	378	}
104		379
105	=item $error, $error_msg, $error_coro	380	=item $coroutine->join
106		381
107	This coroutine will be called on fatal errors. C<$error_msg> and	382	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	383	C<terminate> or C<cancel> functions. C<join> can be called multiple times
109	(NOT an object) respectively. This API might change.	384	from multiple coroutine.
110		385
111	=cut	386	=cut
112		387
113	$error_msg =	388	sub join {
114	$error_coro = undef;	389	my $self = shift;
115		390
116	$error = _newprocess {	391	unless ($self->{status}) {
117	print STDERR "FATAL: $error_msg\nprogram aborted\n";	392	my $current = $current;
118	exit 50;	393
		394	push @{$self->{destroy_cb}}, sub {
		395	$current->ready;
		396	undef $current;
		397	};
		398
		399	&schedule while $current;
		400	}
		401
		402	wantarray ? @{$self->{status}} : $self->{status}[0];
		403	}
		404
		405	=item $coroutine->on_destroy (\&cb)
		406
		407	Registers a callback that is called when this coroutine gets destroyed,
		408	but before it is joined. The callback gets passed the terminate arguments,
		409	if any.
		410
		411	=cut
		412
		413	sub on_destroy {
		414	my ($self, $cb) = @_;
		415
		416	push @{ $self->{destroy_cb} }, $cb;
		417	}
		418
		419	=item $oldprio = $coroutine->prio ($newprio)
		420
		421	Sets (or gets, if the argument is missing) the priority of the
		422	coroutine. Higher priority coroutines get run before lower priority
		423	coroutines. Priorities are small signed integers (currently -4 .. +3),
		424	that you can refer to using PRIO_xxx constants (use the import tag :prio
		425	to get then):
		426
		427	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		428	3 > 1 > 0 > -1 > -3 > -4
		429
		430	# set priority to HIGH
		431	current->prio(PRIO_HIGH);
		432
		433	The idle coroutine ($Coro::idle) always has a lower priority than any
		434	existing coroutine.
		435
		436	Changing the priority of the current coroutine will take effect immediately,
		437	but changing the priority of coroutines in the ready queue (but not
		438	running) will only take effect after the next schedule (of that
		439	coroutine). This is a bug that will be fixed in some future version.
		440
		441	=item $newprio = $coroutine->nice ($change)
		442
		443	Similar to C<prio>, but subtract the given value from the priority (i.e.
		444	higher values mean lower priority, just as in unix).
		445
		446	=item $olddesc = $coroutine->desc ($newdesc)
		447
		448	Sets (or gets in case the argument is missing) the description for this
		449	coroutine. This is just a free-form string you can associate with a coroutine.
		450
		451	=cut
		452
		453	sub desc {
		454	my $old = $_[0]{desc};
		455	$_[0]{desc} = $_[1] if @_ > 1;
		456	$old;
		457	}
		458
		459	=back
		460
		461	=head2 GLOBAL FUNCTIONS
		462
		463	=over 4
		464
		465	=item Coro::nready
		466
		467	Returns the number of coroutines that are currently in the ready state,
		468	i.e. that can be switched to. The value C<0> means that the only runnable
		469	coroutine is the currently running one, so C<cede> would have no effect,
		470	and C<schedule> would cause a deadlock unless there is an idle handler
		471	that wakes up some coroutines.
		472
		473	=item my $guard = Coro::guard { ... }
		474
		475	This creates and returns a guard object. Nothing happens until the object
		476	gets destroyed, in which case the codeblock given as argument will be
		477	executed. This is useful to free locks or other resources in case of a
		478	runtime error or when the coroutine gets canceled, as in both cases the
		479	guard block will be executed. The guard object supports only one method,
		480	C<< ->cancel >>, which will keep the codeblock from being executed.
		481
		482	Example: set some flag and clear it again when the coroutine gets canceled
		483	or the function returns:
		484
		485	sub do_something {
		486	my $guard = Coro::guard { $busy = 0 };
		487	$busy = 1;
		488
		489	# do something that requires $busy to be true
		490	}
		491
		492	=cut
		493
		494	sub guard(&) {
		495	bless \(my $cb = $_[0]), "Coro::guard"
		496	}
		497
		498	sub Coro::guard::cancel {
		499	${$_[0]} = sub { };
		500	}
		501
		502	sub Coro::guard::DESTROY {
		503	${$_[0]}->();
		504	}
		505
		506
		507	=item unblock_sub { ... }
		508
		509	This utility function takes a BLOCK or code reference and "unblocks" it,
		510	returning the new coderef. This means that the new coderef will return
		511	immediately without blocking, returning nothing, while the original code
		512	ref will be called (with parameters) from within its own coroutine.
		513
		514	The reason this function exists is that many event libraries (such as the
		515	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		516	of thread-safety). This means you must not block within event callbacks,
		517	otherwise you might suffer from crashes or worse.
		518
		519	This function allows your callbacks to block by executing them in another
		520	coroutine where it is safe to block. One example where blocking is handy
		521	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		522	disk.
		523
		524	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		525	creating event callbacks that want to block.
		526
		527	=cut
		528
		529	our @unblock_queue;
		530
		531	# we create a special coro because we want to cede,
		532	# to reduce pressure on the coro pool (because most callbacks
		533	# return immediately and can be reused) and because we cannot cede
		534	# inside an event callback.
		535	our $unblock_scheduler = async {
		536	$current->desc ("[unblock_sub scheduler]");
		537	while () {
		538	while (my $cb = pop @unblock_queue) {
		539	# this is an inlined copy of async_pool
		540	my $coro = (pop @pool or new Coro \&pool_handler);
		541
		542	$coro->{_invoke} = $cb;
		543	$coro->ready;
		544	cede; # for short-lived callbacks, this reduces pressure on the coro pool
		545	}
		546	schedule; # sleep well
		547	}
119	};	548	};
120		549
		550	sub unblock_sub(&) {
		551	my $cb = shift;
		552
		553	sub {
		554	unshift @unblock_queue, [$cb, @_];
		555	$unblock_scheduler->ready;
		556	}
		557	}
		558
		559	=back
		560
		561	=cut
		562
121	1;	563	1;
122		564
123	=back	565	=head1 BUGS/LIMITATIONS
124		566
125	=head1 BUGS	567	- you must make very sure that no coro is still active on global
		568	destruction. very bad things might happen otherwise (usually segfaults).
126		569
127	This module has not yet been extensively tested.	570	- this module is not thread-safe. You should only ever use this module
		571	from the same thread (this requirement might be loosened in the future
		572	to allow per-thread schedulers, but Coro::State does not yet allow
		573	this).
128		574
129	=head1 SEE ALSO	575	=head1 SEE ALSO
130		576
131	L<Coro::Process>, L<Coro::Signal>.	577	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
		578
		579	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		580
		581	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
		582
		583	Embedding: L<Coro:MakeMaker>
132		584
133	=head1 AUTHOR	585	=head1 AUTHOR
134		586
135	Marc Lehmann <pcg@goof.com>	587	Marc Lehmann <schmorp@schmorp.de>
136	http://www.goof.com/pcg/marc/	588	http://home.schmorp.de/
137		589
138	=cut	590	=cut
139		591

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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 1.129 by root, Wed Sep 19 22:33:08 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 1.129 by root, Wed Sep 19 22:33:08 2007 UTC