[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 1.139 by root, Thu Sep 27 15:52:30 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 $VERSION = '3.8';
		56
		57	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
		58	our %EXPORT_TAGS = (
		59	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		60	);
		61	our @EXPORT_OK = (@{$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	}
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	$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 {
44	require XSLoader;	144	require Carp;
45	XSLoader::load Coro, $VERSION;	145	Carp::croak ("FATAL: deadlock detected");
46	}	146	};
47		147
48	=item $coro = new [$coderef [, @args]]	148	sub _cancel {
		149	my ($self) = @_;
49		150
50	Create a new coroutine and return it. The first C<transfer> call to this	151	# free coroutine data and mark as destructed
51	coroutine will start execution at the given coderef. If, the subroutine	152	$self->_destroy
52	returns it will be executed again.	153	or return;
53		154
54	If the coderef is omitted this function will create a new "empty"	155	# call all destruction callbacks
55	coroutine, i.e. a coroutine that cannot be transfered to but can be used	156	$_->(@{$self->{status}})
56	to save the current coroutine in.	157	for @{(delete $self->{destroy_cb}) \|\| []};
		158	}
57		159
		160	sub _do_trace_sub {
		161	&{$current->{_trace_sub_cb}}
		162	}
		163
		164	sub _do_trace_line {
		165	&{$current->{_trace_line_cb}}
		166	}
		167
		168	# this coroutine is necessary because a coroutine
		169	# cannot destroy itself.
		170	my @destroy;
		171	my $manager;
		172
		173	$manager = new Coro sub {
		174	while () {
		175	(shift @destroy)->_cancel
		176	while @destroy;
		177
		178	&schedule;
		179	}
		180	};
		181	$manager->desc ("[coro manager]");
		182	$manager->prio (PRIO_MAX);
		183
		184	# static methods. not really.
		185
		186	=back
		187
		188	=head2 STATIC METHODS
		189
		190	Static methods are actually functions that operate on the current coroutine only.
		191
		192	=over 4
		193
		194	=item async { ... } [@args...]
		195
		196	Create a new asynchronous coroutine and return it's coroutine object
		197	(usually unused). When the sub returns the new coroutine is automatically
		198	terminated.
		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
58	=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, otherwise the coroutine
		230	will be re-used "as-is".
		231
		232	The pool size is limited to 8 idle coroutines (this can be adjusted by
		233	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
		234	required.
		235
		236	If you are concerned about pooled coroutines growing a lot because a
		237	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		238	{ terminate }> once per second or so to slowly replenish the pool. In
		239	addition to that, when the stacks used by a handler grows larger than 16kb
		240	(adjustable with $Coro::POOL_RSS) it will also exit.
		241
		242	=cut
		243
		244	our $POOL_SIZE = 8;
		245	our $POOL_RSS = 16 * 1024;
		246	our @async_pool;
		247
		248	sub pool_handler {
		249	my $cb;
		250
		251	while () {
		252	eval {
		253	while () {
		254	_pool_1 $cb;
		255	&$cb;
		256	_pool_2 $cb;
		257	&schedule;
		258	}
		259	};
		260
		261	last if $@ eq "\3terminate\2\n";
		262	warn $@ if $@;
		263	}
		264	}
		265
		266	sub async_pool(&@) {
		267	# this is also inlined into the unlock_scheduler
		268	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		269
		270	$coro->{_invoke} = [@_];
		271	$coro->ready;
		272
		273	$coro
		274	}
		275
		276	=item schedule
		277
		278	Calls the scheduler. Please note that the current coroutine will not be put
		279	into the ready queue, so calling this function usually means you will
		280	never be called again unless something else (e.g. an event handler) calls
		281	ready.
		282
		283	The canonical way to wait on external events is this:
		284
		285	{
		286	# remember current coroutine
		287	my $current = $Coro::current;
		288
		289	# register a hypothetical event handler
		290	on_event_invoke sub {
		291	# wake up sleeping coroutine
		292	$current->ready;
		293	undef $current;
		294	};
		295
		296	# call schedule until event occurred.
		297	# in case we are woken up for other reasons
		298	# (current still defined), loop.
		299	Coro::schedule while $current;
		300	}
		301
		302	=item cede
		303
		304	"Cede" to other coroutines. This function puts the current coroutine into the
		305	ready queue and calls C<schedule>, which has the effect of giving up the
		306	current "timeslice" to other coroutines of the same or higher priority.
		307
		308	Returns true if at least one coroutine switch has happened.
		309
		310	=item Coro::cede_notself
		311
		312	Works like cede, but is not exported by default and will cede to any
		313	coroutine, regardless of priority, once.
		314
		315	Returns true if at least one coroutine switch has happened.
		316
		317	=item terminate [arg...]
		318
		319	Terminates the current coroutine with the given status values (see L<cancel>).
		320
		321	=cut
		322
		323	sub terminate {
		324	$current->cancel (@_);
		325	}
		326
		327	=back
		328
		329	# dynamic methods
		330
		331	=head2 COROUTINE METHODS
		332
		333	These are the methods you can call on coroutine objects.
		334
		335	=over 4
		336
		337	=item new Coro \&sub [, @args...]
		338
		339	Create a new coroutine and return it. When the sub returns the coroutine
		340	automatically terminates as if C<terminate> with the returned values were
		341	called. To make the coroutine run you must first put it into the ready queue
		342	by calling the ready method.
		343
		344	See C<async> for additional discussion.
		345
		346	=cut
		347
		348	sub _run_coro {
		349	terminate &{+shift};
		350	}
59		351
60	sub new {	352	sub new {
61	my $class = $_[0];	353	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		354
75	=item $prev->transfer($next)	355	$class->SUPER::new (\&_run_coro, @_)
		356	}
76		357
77	Save the state of the current subroutine in C<$prev> and switch to the	358	=item $success = $coroutine->ready
78	coroutine saved in C<$next>.
79		359
80	The "state" of a subroutine only ever includes scope, i.e. lexical	360	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	361	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	362	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		363
88	The easiest way to do this is to create your own scheduling primitive like this:	364	=item $is_ready = $coroutine->is_ready
89		365
90	sub schedule {	366	Return wether the coroutine is currently the ready queue or not,
91	local ($_, $@, ...);	367
92	$old->transfer($new);	368	=item $coroutine->cancel (arg...)
		369
		370	Terminates the given coroutine and makes it return the given arguments as
		371	status (default: the empty list). Never returns if the coroutine is the
		372	current coroutine.
		373
		374	=cut
		375
		376	sub cancel {
		377	my $self = shift;
		378	$self->{status} = [@_];
		379
		380	if ($current == $self) {
		381	push @destroy, $self;
		382	$manager->ready;
		383	&schedule while 1;
		384	} else {
		385	$self->_cancel;
93	}	386	}
94
95	=cut
96
97	# I call the _transfer function from a perl function
98	# because that way perl saves all important things on
99	# the stack. Actually, I'd do it from within XS, but
100	# I couldn't get it to work.
101	sub transfer {
102	_transfer($_[0], $_[1]);
103	}	387	}
104		388
105	=item $error, $error_msg, $error_coro	389	=item $coroutine->join
106		390
107	This coroutine will be called on fatal errors. C<$error_msg> and	391	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	392	C<terminate> or C<cancel> functions. C<join> can be called multiple times
109	(NOT an object) respectively. This API might change.	393	from multiple coroutine.
110		394
111	=cut	395	=cut
112		396
113	$error_msg =	397	sub join {
114	$error_coro = undef;	398	my $self = shift;
115		399
116	$error = _newprocess {	400	unless ($self->{status}) {
117	print STDERR "FATAL: $error_msg\nprogram aborted\n";	401	my $current = $current;
118	exit 50;	402
		403	push @{$self->{destroy_cb}}, sub {
		404	$current->ready;
		405	undef $current;
		406	};
		407
		408	&schedule while $current;
		409	}
		410
		411	wantarray ? @{$self->{status}} : $self->{status}[0];
		412	}
		413
		414	=item $coroutine->on_destroy (\&cb)
		415
		416	Registers a callback that is called when this coroutine gets destroyed,
		417	but before it is joined. The callback gets passed the terminate arguments,
		418	if any.
		419
		420	=cut
		421
		422	sub on_destroy {
		423	my ($self, $cb) = @_;
		424
		425	push @{ $self->{destroy_cb} }, $cb;
		426	}
		427
		428	=item $oldprio = $coroutine->prio ($newprio)
		429
		430	Sets (or gets, if the argument is missing) the priority of the
		431	coroutine. Higher priority coroutines get run before lower priority
		432	coroutines. Priorities are small signed integers (currently -4 .. +3),
		433	that you can refer to using PRIO_xxx constants (use the import tag :prio
		434	to get then):
		435
		436	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		437	3 > 1 > 0 > -1 > -3 > -4
		438
		439	# set priority to HIGH
		440	current->prio(PRIO_HIGH);
		441
		442	The idle coroutine ($Coro::idle) always has a lower priority than any
		443	existing coroutine.
		444
		445	Changing the priority of the current coroutine will take effect immediately,
		446	but changing the priority of coroutines in the ready queue (but not
		447	running) will only take effect after the next schedule (of that
		448	coroutine). This is a bug that will be fixed in some future version.
		449
		450	=item $newprio = $coroutine->nice ($change)
		451
		452	Similar to C<prio>, but subtract the given value from the priority (i.e.
		453	higher values mean lower priority, just as in unix).
		454
		455	=item $olddesc = $coroutine->desc ($newdesc)
		456
		457	Sets (or gets in case the argument is missing) the description for this
		458	coroutine. This is just a free-form string you can associate with a coroutine.
		459
		460	=cut
		461
		462	sub desc {
		463	my $old = $_[0]{desc};
		464	$_[0]{desc} = $_[1] if @_ > 1;
		465	$old;
		466	}
		467
		468	=back
		469
		470	=head2 GLOBAL FUNCTIONS
		471
		472	=over 4
		473
		474	=item Coro::nready
		475
		476	Returns the number of coroutines that are currently in the ready state,
		477	i.e. that can be switched to. The value C<0> means that the only runnable
		478	coroutine is the currently running one, so C<cede> would have no effect,
		479	and C<schedule> would cause a deadlock unless there is an idle handler
		480	that wakes up some coroutines.
		481
		482	=item my $guard = Coro::guard { ... }
		483
		484	This creates and returns a guard object. Nothing happens until the object
		485	gets destroyed, in which case the codeblock given as argument will be
		486	executed. This is useful to free locks or other resources in case of a
		487	runtime error or when the coroutine gets canceled, as in both cases the
		488	guard block will be executed. The guard object supports only one method,
		489	C<< ->cancel >>, which will keep the codeblock from being executed.
		490
		491	Example: set some flag and clear it again when the coroutine gets canceled
		492	or the function returns:
		493
		494	sub do_something {
		495	my $guard = Coro::guard { $busy = 0 };
		496	$busy = 1;
		497
		498	# do something that requires $busy to be true
		499	}
		500
		501	=cut
		502
		503	sub guard(&) {
		504	bless \(my $cb = $_[0]), "Coro::guard"
		505	}
		506
		507	sub Coro::guard::cancel {
		508	${$_[0]} = sub { };
		509	}
		510
		511	sub Coro::guard::DESTROY {
		512	${$_[0]}->();
		513	}
		514
		515
		516	=item unblock_sub { ... }
		517
		518	This utility function takes a BLOCK or code reference and "unblocks" it,
		519	returning the new coderef. This means that the new coderef will return
		520	immediately without blocking, returning nothing, while the original code
		521	ref will be called (with parameters) from within its own coroutine.
		522
		523	The reason this function exists is that many event libraries (such as the
		524	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		525	of thread-safety). This means you must not block within event callbacks,
		526	otherwise you might suffer from crashes or worse.
		527
		528	This function allows your callbacks to block by executing them in another
		529	coroutine where it is safe to block. One example where blocking is handy
		530	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		531	disk.
		532
		533	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		534	creating event callbacks that want to block.
		535
		536	=cut
		537
		538	our @unblock_queue;
		539
		540	# we create a special coro because we want to cede,
		541	# to reduce pressure on the coro pool (because most callbacks
		542	# return immediately and can be reused) and because we cannot cede
		543	# inside an event callback.
		544	our $unblock_scheduler = new Coro sub {
		545	while () {
		546	while (my $cb = pop @unblock_queue) {
		547	# this is an inlined copy of async_pool
		548	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		549
		550	$coro->{_invoke} = $cb;
		551	$coro->ready;
		552	cede; # for short-lived callbacks, this reduces pressure on the coro pool
		553	}
		554	schedule; # sleep well
		555	}
119	};	556	};
		557	$unblock_scheduler->desc ("[unblock_sub scheduler]");
		558
		559	sub unblock_sub(&) {
		560	my $cb = shift;
		561
		562	sub {
		563	unshift @unblock_queue, [$cb, @_];
		564	$unblock_scheduler->ready;
		565	}
		566	}
		567
		568	=back
		569
		570	=cut
120		571
121	1;	572	1;
122		573
123	=back	574	=head1 BUGS/LIMITATIONS
124		575
125	=head1 BUGS	576	- you must make very sure that no coro is still active on global
		577	destruction. very bad things might happen otherwise (usually segfaults).
126		578
127	This module has not yet been extensively tested.	579	- this module is not thread-safe. You should only ever use this module
		580	from the same thread (this requirement might be loosened in the future
		581	to allow per-thread schedulers, but Coro::State does not yet allow
		582	this).
128		583
129	=head1 SEE ALSO	584	=head1 SEE ALSO
130		585
131	L<Coro::Process>, L<Coro::Signal>.	586	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
		587
		588	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		589
		590	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
		591
		592	Embedding: L<Coro:MakeMaker>
132		593
133	=head1 AUTHOR	594	=head1 AUTHOR
134		595
135	Marc Lehmann <pcg@goof.com>	596	Marc Lehmann <schmorp@schmorp.de>
136	http://www.goof.com/pcg/marc/	597	http://home.schmorp.de/
137		598
138	=cut	599	=cut
139		600

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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 1.139 by root, Thu Sep 27 15:52:30 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 1.139 by root, Thu Sep 27 15:52:30 2007 UTC