[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 1.135 by root, Sat Sep 22 22:39:15 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. In
		231	addition to that, when the stacks used by a handler grows larger than 16kb
		232	(adjustable with $Coro::POOL_RSS) it will also exit.
		233
		234	=cut
		235
		236	our $POOL_SIZE = 8;
		237	our $POOL_RSS = 16 * 1024;
		238	our @async_pool;
		239
		240	sub pool_handler {
		241	my $cb;
		242
		243	while () {
		244	eval {
		245	while () {
		246	# &{&_pool_1 or &terminate}; # crashes, would be ~5% faster
		247	$cb = &_pool_1
		248	or &terminate;
		249	&$cb;
		250	undef $cb;
		251	&terminate if &_pool_2;
		252	&schedule;
		253	}
		254	};
		255
		256	warn $@ if $@;
		257	}
		258	}
		259
		260	sub async_pool(&@) {
		261	# this is also inlined into the unlock_scheduler
		262	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		263
		264	$coro->{_invoke} = [@_];
		265	$coro->ready;
		266
		267	$coro
		268	}
		269
		270	=item schedule
		271
		272	Calls the scheduler. Please note that the current coroutine will not be put
		273	into the ready queue, so calling this function usually means you will
		274	never be called again unless something else (e.g. an event handler) calls
		275	ready.
		276
		277	The canonical way to wait on external events is this:
		278
		279	{
		280	# remember current coroutine
		281	my $current = $Coro::current;
		282
		283	# register a hypothetical event handler
		284	on_event_invoke sub {
		285	# wake up sleeping coroutine
		286	$current->ready;
		287	undef $current;
		288	};
		289
		290	# call schedule until event occurred.
		291	# in case we are woken up for other reasons
		292	# (current still defined), loop.
		293	Coro::schedule while $current;
		294	}
		295
		296	=item cede
		297
		298	"Cede" to other coroutines. This function puts the current coroutine into the
		299	ready queue and calls C<schedule>, which has the effect of giving up the
		300	current "timeslice" to other coroutines of the same or higher priority.
		301
		302	Returns true if at least one coroutine switch has happened.
		303
		304	=item Coro::cede_notself
		305
		306	Works like cede, but is not exported by default and will cede to any
		307	coroutine, regardless of priority, once.
		308
		309	Returns true if at least one coroutine switch has happened.
		310
		311	=item terminate [arg...]
		312
		313	Terminates the current coroutine with the given status values (see L<cancel>).
		314
		315	=cut
		316
		317	sub terminate {
		318	$current->cancel (@_);
		319	}
		320
		321	=back
		322
		323	# dynamic methods
		324
		325	=head2 COROUTINE METHODS
		326
		327	These are the methods you can call on coroutine objects.
		328
		329	=over 4
		330
		331	=item new Coro \&sub [, @args...]
		332
		333	Create a new coroutine and return it. When the sub returns the coroutine
		334	automatically terminates as if C<terminate> with the returned values were
		335	called. To make the coroutine run you must first put it into the ready queue
		336	by calling the ready method.
		337
		338	See C<async> for additional discussion.
		339
		340	=cut
		341
		342	sub _run_coro {
		343	terminate &{+shift};
		344	}
59		345
60	sub new {	346	sub new {
61	my $class = $_[0];	347	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		348
75	=item $prev->transfer($next)	349	$class->SUPER::new (\&_run_coro, @_)
		350	}
76		351
77	Save the state of the current subroutine in C<$prev> and switch to the	352	=item $success = $coroutine->ready
78	coroutine saved in C<$next>.
79		353
80	The "state" of a subroutine only ever includes scope, i.e. lexical	354	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	355	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	356	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		357
88	The easiest way to do this is to create your own scheduling primitive like this:	358	=item $is_ready = $coroutine->is_ready
89		359
90	sub schedule {	360	Return wether the coroutine is currently the ready queue or not,
91	local ($_, $@, ...);	361
92	$old->transfer($new);	362	=item $coroutine->cancel (arg...)
		363
		364	Terminates the given coroutine and makes it return the given arguments as
		365	status (default: the empty list). Never returns if the coroutine is the
		366	current coroutine.
		367
		368	=cut
		369
		370	sub cancel {
		371	my $self = shift;
		372	$self->{status} = [@_];
		373
		374	if ($current == $self) {
		375	push @destroy, $self;
		376	$manager->ready;
		377	&schedule while 1;
		378	} else {
		379	$self->_cancel;
93	}	380	}
94
95	=cut
96
97	# I call the _transfer function from a perl function
98	# because that way perl saves all important things on
99	# the stack. Actually, I'd do it from within XS, but
100	# I couldn't get it to work.
101	sub transfer {
102	_transfer($_[0], $_[1]);
103	}	381	}
104		382
105	=item $error, $error_msg, $error_coro	383	=item $coroutine->join
106		384
107	This coroutine will be called on fatal errors. C<$error_msg> and	385	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	386	C<terminate> or C<cancel> functions. C<join> can be called multiple times
109	(NOT an object) respectively. This API might change.	387	from multiple coroutine.
110		388
111	=cut	389	=cut
112		390
113	$error_msg =	391	sub join {
114	$error_coro = undef;	392	my $self = shift;
115		393
116	$error = _newprocess {	394	unless ($self->{status}) {
117	print STDERR "FATAL: $error_msg\nprogram aborted\n";	395	my $current = $current;
118	exit 50;	396
		397	push @{$self->{destroy_cb}}, sub {
		398	$current->ready;
		399	undef $current;
		400	};
		401
		402	&schedule while $current;
		403	}
		404
		405	wantarray ? @{$self->{status}} : $self->{status}[0];
		406	}
		407
		408	=item $coroutine->on_destroy (\&cb)
		409
		410	Registers a callback that is called when this coroutine gets destroyed,
		411	but before it is joined. The callback gets passed the terminate arguments,
		412	if any.
		413
		414	=cut
		415
		416	sub on_destroy {
		417	my ($self, $cb) = @_;
		418
		419	push @{ $self->{destroy_cb} }, $cb;
		420	}
		421
		422	=item $oldprio = $coroutine->prio ($newprio)
		423
		424	Sets (or gets, if the argument is missing) the priority of the
		425	coroutine. Higher priority coroutines get run before lower priority
		426	coroutines. Priorities are small signed integers (currently -4 .. +3),
		427	that you can refer to using PRIO_xxx constants (use the import tag :prio
		428	to get then):
		429
		430	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		431	3 > 1 > 0 > -1 > -3 > -4
		432
		433	# set priority to HIGH
		434	current->prio(PRIO_HIGH);
		435
		436	The idle coroutine ($Coro::idle) always has a lower priority than any
		437	existing coroutine.
		438
		439	Changing the priority of the current coroutine will take effect immediately,
		440	but changing the priority of coroutines in the ready queue (but not
		441	running) will only take effect after the next schedule (of that
		442	coroutine). This is a bug that will be fixed in some future version.
		443
		444	=item $newprio = $coroutine->nice ($change)
		445
		446	Similar to C<prio>, but subtract the given value from the priority (i.e.
		447	higher values mean lower priority, just as in unix).
		448
		449	=item $olddesc = $coroutine->desc ($newdesc)
		450
		451	Sets (or gets in case the argument is missing) the description for this
		452	coroutine. This is just a free-form string you can associate with a coroutine.
		453
		454	=cut
		455
		456	sub desc {
		457	my $old = $_[0]{desc};
		458	$_[0]{desc} = $_[1] if @_ > 1;
		459	$old;
		460	}
		461
		462	=back
		463
		464	=head2 GLOBAL FUNCTIONS
		465
		466	=over 4
		467
		468	=item Coro::nready
		469
		470	Returns the number of coroutines that are currently in the ready state,
		471	i.e. that can be switched to. The value C<0> means that the only runnable
		472	coroutine is the currently running one, so C<cede> would have no effect,
		473	and C<schedule> would cause a deadlock unless there is an idle handler
		474	that wakes up some coroutines.
		475
		476	=item my $guard = Coro::guard { ... }
		477
		478	This creates and returns a guard object. Nothing happens until the object
		479	gets destroyed, in which case the codeblock given as argument will be
		480	executed. This is useful to free locks or other resources in case of a
		481	runtime error or when the coroutine gets canceled, as in both cases the
		482	guard block will be executed. The guard object supports only one method,
		483	C<< ->cancel >>, which will keep the codeblock from being executed.
		484
		485	Example: set some flag and clear it again when the coroutine gets canceled
		486	or the function returns:
		487
		488	sub do_something {
		489	my $guard = Coro::guard { $busy = 0 };
		490	$busy = 1;
		491
		492	# do something that requires $busy to be true
		493	}
		494
		495	=cut
		496
		497	sub guard(&) {
		498	bless \(my $cb = $_[0]), "Coro::guard"
		499	}
		500
		501	sub Coro::guard::cancel {
		502	${$_[0]} = sub { };
		503	}
		504
		505	sub Coro::guard::DESTROY {
		506	${$_[0]}->();
		507	}
		508
		509
		510	=item unblock_sub { ... }
		511
		512	This utility function takes a BLOCK or code reference and "unblocks" it,
		513	returning the new coderef. This means that the new coderef will return
		514	immediately without blocking, returning nothing, while the original code
		515	ref will be called (with parameters) from within its own coroutine.
		516
		517	The reason this function exists is that many event libraries (such as the
		518	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		519	of thread-safety). This means you must not block within event callbacks,
		520	otherwise you might suffer from crashes or worse.
		521
		522	This function allows your callbacks to block by executing them in another
		523	coroutine where it is safe to block. One example where blocking is handy
		524	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		525	disk.
		526
		527	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		528	creating event callbacks that want to block.
		529
		530	=cut
		531
		532	our @unblock_queue;
		533
		534	# we create a special coro because we want to cede,
		535	# to reduce pressure on the coro pool (because most callbacks
		536	# return immediately and can be reused) and because we cannot cede
		537	# inside an event callback.
		538	our $unblock_scheduler = new Coro sub {
		539	while () {
		540	while (my $cb = pop @unblock_queue) {
		541	# this is an inlined copy of async_pool
		542	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		543
		544	$coro->{_invoke} = $cb;
		545	$coro->ready;
		546	cede; # for short-lived callbacks, this reduces pressure on the coro pool
		547	}
		548	schedule; # sleep well
		549	}
119	};	550	};
		551	$unblock_scheduler->desc ("[unblock_sub scheduler]");
		552
		553	sub unblock_sub(&) {
		554	my $cb = shift;
		555
		556	sub {
		557	unshift @unblock_queue, [$cb, @_];
		558	$unblock_scheduler->ready;
		559	}
		560	}
		561
		562	=back
		563
		564	=cut
120		565
121	1;	566	1;
122		567
123	=back	568	=head1 BUGS/LIMITATIONS
124		569
125	=head1 BUGS	570	- you must make very sure that no coro is still active on global
		571	destruction. very bad things might happen otherwise (usually segfaults).
126		572
127	This module has not yet been extensively tested.	573	- this module is not thread-safe. You should only ever use this module
		574	from the same thread (this requirement might be loosened in the future
		575	to allow per-thread schedulers, but Coro::State does not yet allow
		576	this).
128		577
129	=head1 SEE ALSO	578	=head1 SEE ALSO
130		579
131	L<Coro::Process>, L<Coro::Signal>.	580	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
		581
		582	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		583
		584	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
		585
		586	Embedding: L<Coro:MakeMaker>
132		587
133	=head1 AUTHOR	588	=head1 AUTHOR
134		589
135	Marc Lehmann <pcg@goof.com>	590	Marc Lehmann <schmorp@schmorp.de>
136	http://www.goof.com/pcg/marc/	591	http://home.schmorp.de/
137		592
138	=cut	593	=cut
139		594

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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 1.135 by root, Sat Sep 22 22:39:15 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 1.135 by root, Sat Sep 22 22:39:15 2007 UTC