[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 1.132 by root, Thu Sep 20 22:53:23 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	$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	# this coroutine is necessary because a coroutine
		161	# cannot destroy itself.
		162	my @destroy;
		163	my $manager;
		164
		165	$manager = new Coro sub {
		166	while () {
		167	(shift @destroy)->_cancel
		168	while @destroy;
		169
		170	&schedule;
		171	}
		172	};
		173	$manager->desc ("[coro manager]");
		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 $MAX_POOL_RSS = 64 * 1024;
		236	our @pool;
		237
		238	sub pool_handler {
		239	while () {
		240	$current->{desc} = "[async_pool]";
		241
		242	eval {
		243	my ($cb, @arg) = @{ delete $current->{_invoke} or return };
		244	$cb->(@arg);
		245	};
		246	warn $@ if $@;
		247
		248	last if @pool >= $POOL_SIZE \|\| $current->rss >= $MAX_POOL_RSS;
		249
		250	push @pool, $current;
		251	$current->{desc} = "[async_pool idle]";
		252	$current->save (Coro::State::SAVE_DEF);
		253	$current->prio (0);
		254	schedule;
		255	}
		256	}
		257
		258	sub async_pool(&@) {
		259	# this is also inlined into the unlock_scheduler
		260	my $coro = (pop @pool) \|\| new Coro \&pool_handler;;
		261
		262	$coro->{_invoke} = [@_];
		263	$coro->ready;
		264
		265	$coro
		266	}
		267
		268	=item schedule
		269
		270	Calls the scheduler. Please note that the current coroutine will not be put
		271	into the ready queue, so calling this function usually means you will
		272	never be called again unless something else (e.g. an event handler) calls
		273	ready.
		274
		275	The canonical way to wait on external events is this:
		276
		277	{
		278	# remember current coroutine
		279	my $current = $Coro::current;
		280
		281	# register a hypothetical event handler
		282	on_event_invoke sub {
		283	# wake up sleeping coroutine
		284	$current->ready;
		285	undef $current;
		286	};
		287
		288	# call schedule until event occurred.
		289	# in case we are woken up for other reasons
		290	# (current still defined), loop.
		291	Coro::schedule while $current;
		292	}
		293
		294	=item cede
		295
		296	"Cede" to other coroutines. This function puts the current coroutine into the
		297	ready queue and calls C<schedule>, which has the effect of giving up the
		298	current "timeslice" to other coroutines of the same or higher priority.
		299
		300	Returns true if at least one coroutine switch has happened.
		301
		302	=item Coro::cede_notself
		303
		304	Works like cede, but is not exported by default and will cede to any
		305	coroutine, regardless of priority, once.
		306
		307	Returns true if at least one coroutine switch has happened.
		308
		309	=item terminate [arg...]
		310
		311	Terminates the current coroutine with the given status values (see L<cancel>).
		312
		313	=cut
		314
		315	sub terminate {
		316	$current->cancel (@_);
		317	}
		318
		319	=back
		320
		321	# dynamic methods
		322
		323	=head2 COROUTINE METHODS
		324
		325	These are the methods you can call on coroutine objects.
		326
		327	=over 4
		328
		329	=item new Coro \&sub [, @args...]
		330
		331	Create a new coroutine and return it. When the sub returns the coroutine
		332	automatically terminates as if C<terminate> with the returned values were
		333	called. To make the coroutine run you must first put it into the ready queue
		334	by calling the ready method.
		335
		336	See C<async> for additional discussion.
		337
		338	=cut
		339
		340	sub _run_coro {
		341	terminate &{+shift};
		342	}
59		343
60	sub new {	344	sub new {
61	my $class = $_[0];	345	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		346
75	=item $prev->transfer($next)	347	$class->SUPER::new (\&_run_coro, @_)
		348	}
76		349
77	Save the state of the current subroutine in C<$prev> and switch to the	350	=item $success = $coroutine->ready
78	coroutine saved in C<$next>.
79		351
80	The "state" of a subroutine only ever includes scope, i.e. lexical	352	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	353	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	354	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		355
88	The easiest way to do this is to create your own scheduling primitive like this:	356	=item $is_ready = $coroutine->is_ready
89		357
90	sub schedule {	358	Return wether the coroutine is currently the ready queue or not,
91	local ($_, $@, ...);	359
92	$old->transfer($new);	360	=item $coroutine->cancel (arg...)
		361
		362	Terminates the given coroutine and makes it return the given arguments as
		363	status (default: the empty list). Never returns if the coroutine is the
		364	current coroutine.
		365
		366	=cut
		367
		368	sub cancel {
		369	my $self = shift;
		370	$self->{status} = [@_];
		371
		372	if ($current == $self) {
		373	push @destroy, $self;
		374	$manager->ready;
		375	&schedule while 1;
		376	} else {
		377	$self->_cancel;
93	}	378	}
94
95	=cut
96
97	# I call the _transfer function from a perl function
98	# because that way perl saves all important things on
99	# the stack. Actually, I'd do it from within XS, but
100	# I couldn't get it to work.
101	sub transfer {
102	_transfer($_[0], $_[1]);
103	}	379	}
104		380
105	=item $error, $error_msg, $error_coro	381	=item $coroutine->join
106		382
107	This coroutine will be called on fatal errors. C<$error_msg> and	383	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	384	C<terminate> or C<cancel> functions. C<join> can be called multiple times
109	(NOT an object) respectively. This API might change.	385	from multiple coroutine.
110		386
111	=cut	387	=cut
112		388
113	$error_msg =	389	sub join {
114	$error_coro = undef;	390	my $self = shift;
115		391
116	$error = _newprocess {	392	unless ($self->{status}) {
117	print STDERR "FATAL: $error_msg\nprogram aborted\n";	393	my $current = $current;
118	exit 50;	394
		395	push @{$self->{destroy_cb}}, sub {
		396	$current->ready;
		397	undef $current;
		398	};
		399
		400	&schedule while $current;
		401	}
		402
		403	wantarray ? @{$self->{status}} : $self->{status}[0];
		404	}
		405
		406	=item $coroutine->on_destroy (\&cb)
		407
		408	Registers a callback that is called when this coroutine gets destroyed,
		409	but before it is joined. The callback gets passed the terminate arguments,
		410	if any.
		411
		412	=cut
		413
		414	sub on_destroy {
		415	my ($self, $cb) = @_;
		416
		417	push @{ $self->{destroy_cb} }, $cb;
		418	}
		419
		420	=item $oldprio = $coroutine->prio ($newprio)
		421
		422	Sets (or gets, if the argument is missing) the priority of the
		423	coroutine. Higher priority coroutines get run before lower priority
		424	coroutines. Priorities are small signed integers (currently -4 .. +3),
		425	that you can refer to using PRIO_xxx constants (use the import tag :prio
		426	to get then):
		427
		428	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		429	3 > 1 > 0 > -1 > -3 > -4
		430
		431	# set priority to HIGH
		432	current->prio(PRIO_HIGH);
		433
		434	The idle coroutine ($Coro::idle) always has a lower priority than any
		435	existing coroutine.
		436
		437	Changing the priority of the current coroutine will take effect immediately,
		438	but changing the priority of coroutines in the ready queue (but not
		439	running) will only take effect after the next schedule (of that
		440	coroutine). This is a bug that will be fixed in some future version.
		441
		442	=item $newprio = $coroutine->nice ($change)
		443
		444	Similar to C<prio>, but subtract the given value from the priority (i.e.
		445	higher values mean lower priority, just as in unix).
		446
		447	=item $olddesc = $coroutine->desc ($newdesc)
		448
		449	Sets (or gets in case the argument is missing) the description for this
		450	coroutine. This is just a free-form string you can associate with a coroutine.
		451
		452	=cut
		453
		454	sub desc {
		455	my $old = $_[0]{desc};
		456	$_[0]{desc} = $_[1] if @_ > 1;
		457	$old;
		458	}
		459
		460	=back
		461
		462	=head2 GLOBAL FUNCTIONS
		463
		464	=over 4
		465
		466	=item Coro::nready
		467
		468	Returns the number of coroutines that are currently in the ready state,
		469	i.e. that can be switched to. The value C<0> means that the only runnable
		470	coroutine is the currently running one, so C<cede> would have no effect,
		471	and C<schedule> would cause a deadlock unless there is an idle handler
		472	that wakes up some coroutines.
		473
		474	=item my $guard = Coro::guard { ... }
		475
		476	This creates and returns a guard object. Nothing happens until the object
		477	gets destroyed, in which case the codeblock given as argument will be
		478	executed. This is useful to free locks or other resources in case of a
		479	runtime error or when the coroutine gets canceled, as in both cases the
		480	guard block will be executed. The guard object supports only one method,
		481	C<< ->cancel >>, which will keep the codeblock from being executed.
		482
		483	Example: set some flag and clear it again when the coroutine gets canceled
		484	or the function returns:
		485
		486	sub do_something {
		487	my $guard = Coro::guard { $busy = 0 };
		488	$busy = 1;
		489
		490	# do something that requires $busy to be true
		491	}
		492
		493	=cut
		494
		495	sub guard(&) {
		496	bless \(my $cb = $_[0]), "Coro::guard"
		497	}
		498
		499	sub Coro::guard::cancel {
		500	${$_[0]} = sub { };
		501	}
		502
		503	sub Coro::guard::DESTROY {
		504	${$_[0]}->();
		505	}
		506
		507
		508	=item unblock_sub { ... }
		509
		510	This utility function takes a BLOCK or code reference and "unblocks" it,
		511	returning the new coderef. This means that the new coderef will return
		512	immediately without blocking, returning nothing, while the original code
		513	ref will be called (with parameters) from within its own coroutine.
		514
		515	The reason this function exists is that many event libraries (such as the
		516	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		517	of thread-safety). This means you must not block within event callbacks,
		518	otherwise you might suffer from crashes or worse.
		519
		520	This function allows your callbacks to block by executing them in another
		521	coroutine where it is safe to block. One example where blocking is handy
		522	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		523	disk.
		524
		525	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		526	creating event callbacks that want to block.
		527
		528	=cut
		529
		530	our @unblock_queue;
		531
		532	# we create a special coro because we want to cede,
		533	# to reduce pressure on the coro pool (because most callbacks
		534	# return immediately and can be reused) and because we cannot cede
		535	# inside an event callback.
		536	our $unblock_scheduler = new Coro sub {
		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	};
		549	$unblock_scheduler->desc ("[unblock_sub scheduler]");
		550
		551	sub unblock_sub(&) {
		552	my $cb = shift;
		553
		554	sub {
		555	unshift @unblock_queue, [$cb, @_];
		556	$unblock_scheduler->ready;
		557	}
		558	}
		559
		560	=back
		561
		562	=cut
120		563
121	1;	564	1;
122		565
123	=back	566	=head1 BUGS/LIMITATIONS
124		567
125	=head1 BUGS	568	- you must make very sure that no coro is still active on global
		569	destruction. very bad things might happen otherwise (usually segfaults).
126		570
127	This module has not yet been extensively tested.	571	- this module is not thread-safe. You should only ever use this module
		572	from the same thread (this requirement might be loosened in the future
		573	to allow per-thread schedulers, but Coro::State does not yet allow
		574	this).
128		575
129	=head1 SEE ALSO	576	=head1 SEE ALSO
130		577
131	L<Coro::Process>, L<Coro::Signal>.	578	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
		579
		580	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		581
		582	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
		583
		584	Embedding: L<Coro:MakeMaker>
132		585
133	=head1 AUTHOR	586	=head1 AUTHOR
134		587
135	Marc Lehmann <pcg@goof.com>	588	Marc Lehmann <schmorp@schmorp.de>
136	http://www.goof.com/pcg/marc/	589	http://home.schmorp.de/
137		590
138	=cut	591	=cut
139		592

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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 1.132 by root, Thu Sep 20 22:53:23 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 1.132 by root, Thu Sep 20 22:53:23 2007 UTC