[ViewVC] Diff of: cvs/Coro/Coro.pm

Comparing Coro/Coro.pm (file contents):
Revision 1.6 by root, Tue Jul 10 21:19:47 2001 UTC vs.
Revision 1.179 by root, Sat Apr 19 19:06:02 2008 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		15	print "1\n";
16	$main = new Coro;	16	cede; # yield to coroutine
17		17	print "3\n";
18	print "in main, switching to coroutine\n";	18	cede; # and again
19	$main->transfer($new);	19
20	print "back in main, switch to coroutine again\n";	20	# use locking
21	$main->transfer($new);	21	my $lock = new Coro::Semaphore;
22	print "back in main\n";	22	my $locked;
		23
		24	$lock->down;
		25	$locked = 1;
		26	$lock->up;
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 $VERSION = '4.51';
		63
		64	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
		65	our %EXPORT_TAGS = (
		66	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		67	);
		68	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
34		69
35	=over 4	70	=over 4
36		71
37	=cut	72	=item $main
38		73
39	package Coro;	74	This coroutine represents the main program.
40		75
41	BEGIN {	76	=cut
42	$VERSION = 0.03;
43		77
		78	$main = new Coro;
		79
		80	=item $current (or as function: current)
		81
		82	The current coroutine (the last coroutine switched to). The initial value
		83	is C<$main> (of course).
		84
		85	This variable is B<strictly> I<read-only>. It is provided for performance
		86	reasons. If performance is not essential you are encouraged to use the
		87	C<Coro::current> function instead.
		88
		89	=cut
		90
		91	$main->{desc} = "[main::]";
		92
		93	# maybe some other module used Coro::Specific before...
		94	$main->{_specific} = $current->{_specific}
		95	if $current;
		96
		97	_set_current $main;
		98
		99	sub current() { $current }
		100
		101	=item $idle
		102
		103	A callback that is called whenever the scheduler finds no ready coroutines
		104	to run. The default implementation prints "FATAL: deadlock detected" and
		105	exits, because the program has no other way to continue.
		106
		107	This hook is overwritten by modules such as C<Coro::Timer> and
		108	C<Coro::Event> to wait on an external event that hopefully wake up a
		109	coroutine so the scheduler can run it.
		110
		111	Please note that if your callback recursively invokes perl (e.g. for event
		112	handlers), then it must be prepared to be called recursively itself.
		113
		114	=cut
		115
		116	$idle = sub {
44	require XSLoader;	117	require Carp;
45	XSLoader::load Coro, $VERSION;	118	Carp::croak ("FATAL: deadlock detected");
46	}	119	};
47		120
48	=item $coro = new [$coderef [, @args]]	121	sub _cancel {
		122	my ($self) = @_;
49		123
50	Create a new coroutine and return it. The first C<transfer> call to this	124	# free coroutine data and mark as destructed
51	coroutine will start execution at the given coderef. If, the subroutine	125	$self->_destroy
52	returns it will be executed again.	126	or return;
53		127
54	If the coderef is omitted this function will create a new "empty"	128	# call all destruction callbacks
55	coroutine, i.e. a coroutine that cannot be transfered to but can be used	129	$_->(@{$self->{_status}})
56	to save the current coroutine in.	130	for @{(delete $self->{_on_destroy}) \|\| []};
		131	}
57		132
		133	# this coroutine is necessary because a coroutine
		134	# cannot destroy itself.
		135	my @destroy;
		136	my $manager;
		137
		138	$manager = new Coro sub {
		139	while () {
		140	(shift @destroy)->_cancel
		141	while @destroy;
		142
		143	&schedule;
		144	}
		145	};
		146	$manager->desc ("[coro manager]");
		147	$manager->prio (PRIO_MAX);
		148
		149	=back
		150
		151	=head2 STATIC METHODS
		152
		153	Static methods are actually functions that operate on the current coroutine only.
		154
		155	=over 4
		156
		157	=item async { ... } [@args...]
		158
		159	Create a new asynchronous coroutine and return it's coroutine object
		160	(usually unused). When the sub returns the new coroutine is automatically
		161	terminated.
		162
		163	See the C<Coro::State::new> constructor for info about the coroutine
		164	environment in which coroutines run.
		165
		166	Calling C<exit> in a coroutine will do the same as calling exit outside
		167	the coroutine. Likewise, when the coroutine dies, the program will exit,
		168	just as it would in the main program.
		169
		170	# create a new coroutine that just prints its arguments
		171	async {
		172	print "@_\n";
		173	} 1,2,3,4;
		174
58	=cut	175	=cut
		176
		177	sub async(&@) {
		178	my $coro = new Coro @_;
		179	$coro->ready;
		180	$coro
		181	}
		182
		183	=item async_pool { ... } [@args...]
		184
		185	Similar to C<async>, but uses a coroutine pool, so you should not call
		186	terminate or join (although you are allowed to), and you get a coroutine
		187	that might have executed other code already (which can be good or bad :).
		188
		189	Also, the block is executed in an C<eval> context and a warning will be
		190	issued in case of an exception instead of terminating the program, as
		191	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		192	will not work in the expected way, unless you call terminate or cancel,
		193	which somehow defeats the purpose of pooling.
		194
		195	The priority will be reset to C<0> after each job, tracing will be
		196	disabled, the description will be reset and the default output filehandle
		197	gets restored, so you can change alkl these. Otherwise the coroutine will
		198	be re-used "as-is": most notably if you change other per-coroutine global
		199	stuff such as C<$/> you need to revert that change, which is most simply
		200	done by using local as in C< local $/ >.
		201
		202	The pool size is limited to 8 idle coroutines (this can be adjusted by
		203	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
		204	required.
		205
		206	If you are concerned about pooled coroutines growing a lot because a
		207	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		208	{ terminate }> once per second or so to slowly replenish the pool. In
		209	addition to that, when the stacks used by a handler grows larger than 16kb
		210	(adjustable with $Coro::POOL_RSS) it will also exit.
		211
		212	=cut
		213
		214	our $POOL_SIZE = 8;
		215	our $POOL_RSS = 16 * 1024;
		216	our @async_pool;
		217
		218	sub pool_handler {
		219	my $cb;
		220
		221	while () {
		222	eval {
		223	while () {
		224	_pool_1 $cb;
		225	&$cb;
		226	_pool_2 $cb;
		227	&schedule;
		228	}
		229	};
		230
		231	last if $@ eq "\3async_pool terminate\2\n";
		232	warn $@ if $@;
		233	}
		234	}
		235
		236	sub async_pool(&@) {
		237	# this is also inlined into the unlock_scheduler
		238	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		239
		240	$coro->{_invoke} = [@_];
		241	$coro->ready;
		242
		243	$coro
		244	}
		245
		246	=item schedule
		247
		248	Calls the scheduler. Please note that the current coroutine will not be put
		249	into the ready queue, so calling this function usually means you will
		250	never be called again unless something else (e.g. an event handler) calls
		251	ready.
		252
		253	The canonical way to wait on external events is this:
		254
		255	{
		256	# remember current coroutine
		257	my $current = $Coro::current;
		258
		259	# register a hypothetical event handler
		260	on_event_invoke sub {
		261	# wake up sleeping coroutine
		262	$current->ready;
		263	undef $current;
		264	};
		265
		266	# call schedule until event occurred.
		267	# in case we are woken up for other reasons
		268	# (current still defined), loop.
		269	Coro::schedule while $current;
		270	}
		271
		272	=item cede
		273
		274	"Cede" to other coroutines. This function puts the current coroutine into the
		275	ready queue and calls C<schedule>, which has the effect of giving up the
		276	current "timeslice" to other coroutines of the same or higher priority.
		277
		278	=item Coro::cede_notself
		279
		280	Works like cede, but is not exported by default and will cede to any
		281	coroutine, regardless of priority, once.
		282
		283	=item terminate [arg...]
		284
		285	Terminates the current coroutine with the given status values (see L<cancel>).
		286
		287	=item killall
		288
		289	Kills/terminates/cancels all coroutines except the currently running
		290	one. This is useful after a fork, either in the child or the parent, as
		291	usually only one of them should inherit the running coroutines.
		292
		293	=cut
		294
		295	sub terminate {
		296	$current->cancel (@_);
		297	}
		298
		299	sub killall {
		300	for (Coro::State::list) {
		301	$_->cancel
		302	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		303	}
		304	}
		305
		306	=back
		307
		308	=head2 COROUTINE METHODS
		309
		310	These are the methods you can call on coroutine objects.
		311
		312	=over 4
		313
		314	=item new Coro \&sub [, @args...]
		315
		316	Create a new coroutine and return it. When the sub returns the coroutine
		317	automatically terminates as if C<terminate> with the returned values were
		318	called. To make the coroutine run you must first put it into the ready queue
		319	by calling the ready method.
		320
		321	See C<async> and C<Coro::State::new> for additional info about the
		322	coroutine environment.
		323
		324	=cut
		325
		326	sub _run_coro {
		327	terminate &{+shift};
		328	}
59		329
60	sub new {	330	sub new {
61	my $class = $_[0];	331	my $class = shift;
62	my $proc = $_[1] \|\| sub { die "tried to transfer to an empty coroutine" };	332
63	bless _newprocess {	333	$class->SUPER::new (\&_run_coro, @_)
64	do {	334	}
65	eval { &$proc };	335
66	if ($@) {	336	=item $success = $coroutine->ready
67	$error_msg = $@;	337
68	$error_coro = _newprocess { };	338	Put the given coroutine into the ready queue (according to it's priority)
69	&transfer($error_coro, $error);	339	and return true. If the coroutine is already in the ready queue, do nothing
		340	and return false.
		341
		342	=item $is_ready = $coroutine->is_ready
		343
		344	Return wether the coroutine is currently the ready queue or not,
		345
		346	=item $coroutine->cancel (arg...)
		347
		348	Terminates the given coroutine and makes it return the given arguments as
		349	status (default: the empty list). Never returns if the coroutine is the
		350	current coroutine.
		351
		352	=cut
		353
		354	sub cancel {
		355	my $self = shift;
		356	$self->{_status} = [@_];
		357
		358	if ($current == $self) {
		359	push @destroy, $self;
		360	$manager->ready;
		361	&schedule while 1;
		362	} else {
		363	$self->_cancel;
		364	}
		365	}
		366
		367	=item $coroutine->join
		368
		369	Wait until the coroutine terminates and return any values given to the
		370	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		371	from multiple coroutines.
		372
		373	=cut
		374
		375	sub join {
		376	my $self = shift;
		377
		378	unless ($self->{_status}) {
		379	my $current = $current;
		380
		381	push @{$self->{_on_destroy}}, sub {
		382	$current->ready;
		383	undef $current;
		384	};
		385
		386	&schedule while $current;
		387	}
		388
		389	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		390	}
		391
		392	=item $coroutine->on_destroy (\&cb)
		393
		394	Registers a callback that is called when this coroutine gets destroyed,
		395	but before it is joined. The callback gets passed the terminate arguments,
		396	if any.
		397
		398	=cut
		399
		400	sub on_destroy {
		401	my ($self, $cb) = @_;
		402
		403	push @{ $self->{_on_destroy} }, $cb;
		404	}
		405
		406	=item $oldprio = $coroutine->prio ($newprio)
		407
		408	Sets (or gets, if the argument is missing) the priority of the
		409	coroutine. Higher priority coroutines get run before lower priority
		410	coroutines. Priorities are small signed integers (currently -4 .. +3),
		411	that you can refer to using PRIO_xxx constants (use the import tag :prio
		412	to get then):
		413
		414	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		415	3 > 1 > 0 > -1 > -3 > -4
		416
		417	# set priority to HIGH
		418	current->prio(PRIO_HIGH);
		419
		420	The idle coroutine ($Coro::idle) always has a lower priority than any
		421	existing coroutine.
		422
		423	Changing the priority of the current coroutine will take effect immediately,
		424	but changing the priority of coroutines in the ready queue (but not
		425	running) will only take effect after the next schedule (of that
		426	coroutine). This is a bug that will be fixed in some future version.
		427
		428	=item $newprio = $coroutine->nice ($change)
		429
		430	Similar to C<prio>, but subtract the given value from the priority (i.e.
		431	higher values mean lower priority, just as in unix).
		432
		433	=item $olddesc = $coroutine->desc ($newdesc)
		434
		435	Sets (or gets in case the argument is missing) the description for this
		436	coroutine. This is just a free-form string you can associate with a coroutine.
		437
		438	This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
		439	can modify this member directly if you wish.
		440
		441	=item $coroutine->throw ([$scalar])
		442
		443	If C<$throw> is specified and defined, it will be thrown as an exception
		444	inside the coroutine at the next convinient point in time (usually after
		445	it gains control at the next schedule/transfer/cede). Otherwise clears the
		446	exception object.
		447
		448	The exception object will be thrown "as is" with the specified scalar in
		449	C<$@>, i.e. if it is a string, no line number or newline will be appended
		450	(unlike with C<die>).
		451
		452	This can be used as a softer means than C<cancel> to ask a coroutine to
		453	end itself, although there is no guarentee that the exception will lead to
		454	termination, and if the exception isn't caught it might well end the whole
		455	program.
		456
		457	=cut
		458
		459	sub desc {
		460	my $old = $_[0]{desc};
		461	$_[0]{desc} = $_[1] if @_ > 1;
		462	$old;
		463	}
		464
		465	=back
		466
		467	=head2 GLOBAL FUNCTIONS
		468
		469	=over 4
		470
		471	=item Coro::nready
		472
		473	Returns the number of coroutines that are currently in the ready state,
		474	i.e. that can be switched to. The value C<0> means that the only runnable
		475	coroutine is the currently running one, so C<cede> would have no effect,
		476	and C<schedule> would cause a deadlock unless there is an idle handler
		477	that wakes up some coroutines.
		478
		479	=item my $guard = Coro::guard { ... }
		480
		481	This creates and returns a guard object. Nothing happens until the object
		482	gets destroyed, in which case the codeblock given as argument will be
		483	executed. This is useful to free locks or other resources in case of a
		484	runtime error or when the coroutine gets canceled, as in both cases the
		485	guard block will be executed. The guard object supports only one method,
		486	C<< ->cancel >>, which will keep the codeblock from being executed.
		487
		488	Example: set some flag and clear it again when the coroutine gets canceled
		489	or the function returns:
		490
		491	sub do_something {
		492	my $guard = Coro::guard { $busy = 0 };
		493	$busy = 1;
		494
		495	# do something that requires $busy to be true
		496	}
		497
		498	=cut
		499
		500	sub guard(&) {
		501	bless \(my $cb = $_[0]), "Coro::guard"
		502	}
		503
		504	sub Coro::guard::cancel {
		505	${$_[0]} = sub { };
		506	}
		507
		508	sub Coro::guard::DESTROY {
		509	${$_[0]}->();
		510	}
		511
		512
		513	=item unblock_sub { ... }
		514
		515	This utility function takes a BLOCK or code reference and "unblocks" it,
		516	returning the new coderef. This means that the new coderef will return
		517	immediately without blocking, returning nothing, while the original code
		518	ref will be called (with parameters) from within its own coroutine.
		519
		520	The reason this function exists is that many event libraries (such as the
		521	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		522	of thread-safety). This means you must not block within event callbacks,
		523	otherwise you might suffer from crashes or worse.
		524
		525	This function allows your callbacks to block by executing them in another
		526	coroutine where it is safe to block. One example where blocking is handy
		527	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		528	disk.
		529
		530	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		531	creating event callbacks that want to block.
		532
		533	=cut
		534
		535	our @unblock_queue;
		536
		537	# we create a special coro because we want to cede,
		538	# to reduce pressure on the coro pool (because most callbacks
		539	# return immediately and can be reused) and because we cannot cede
		540	# inside an event callback.
		541	our $unblock_scheduler = new Coro sub {
		542	while () {
		543	while (my $cb = pop @unblock_queue) {
		544	# this is an inlined copy of async_pool
		545	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		546
		547	$coro->{_invoke} = $cb;
		548	$coro->ready;
		549	cede; # for short-lived callbacks, this reduces pressure on the coro pool
70	}	550	}
71	} while (1);	551	schedule; # sleep well
72	}, $class;	552	}
73	}
74
75	=item $prev->transfer($next)
76
77	Save the state of the current subroutine in $prev and switch to the
78	coroutine saved in $next.
79
80	=cut
81
82	# I call the _transfer function from a perl function
83	# because that way perl saves all important things on
84	# the stack.
85	sub transfer {
86	_transfer($_[0], $_[1]);
87	}
88
89	=item $error, $error_msg, $error_coro
90
91	This coroutine will be called on fatal errors. C<$error_msg> and
92	C<$error_coro> return the error message and the error-causing coroutine
93	(NOT an object) respectively. This API might change.
94
95	=cut
96
97	$error_msg =
98	$error_coro = undef;
99
100	$error = _newprocess {
101	print STDERR "FATAL: $error_msg\nprogram aborted\n";
102	exit 50;
103	};	553	};
		554	$unblock_scheduler->desc ("[unblock_sub scheduler]");
		555
		556	sub unblock_sub(&) {
		557	my $cb = shift;
		558
		559	sub {
		560	unshift @unblock_queue, [$cb, @_];
		561	$unblock_scheduler->ready;
		562	}
		563	}
		564
		565	=back
		566
		567	=cut
104		568
105	1;	569	1;
106		570
107	=back	571	=head1 BUGS/LIMITATIONS
108		572
109	=head1 BUGS	573	- you must make very sure that no coro is still active on global
		574	destruction. very bad things might happen otherwise (usually segfaults).
110		575
111	This module has not yet been extensively tested.	576	- this module is not thread-safe. You should only ever use this module
		577	from the same thread (this requirement might be loosened in the future
		578	to allow per-thread schedulers, but Coro::State does not yet allow
		579	this).
112		580
113	=head1 SEE ALSO	581	=head1 SEE ALSO
114		582
115	L<Coro::Process>, L<Coro::Signal>.	583	Lower level Configuration, Coroutine Environment: L<Coro::State>.
		584
		585	Debugging: L<Coro::Debug>.
		586
		587	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
		588
		589	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		590
		591	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>.
		592
		593	Compatibility: L<Coro::LWP>, L<Coro::Storable>, L<Coro::Select>.
		594
		595	Embedding: L<Coro::MakeMaker>.
116		596
117	=head1 AUTHOR	597	=head1 AUTHOR
118		598
119	Marc Lehmann <pcg@goof.com>	599	Marc Lehmann <schmorp@schmorp.de>
120	http://www.goof.com/pcg/marc/	600	http://home.schmorp.de/
121		601
122	=cut	602	=cut
123		603

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Comparing Coro/Coro.pm (file contents): Revision 1.6 by root, Tue Jul 10 21:19:47 2001 UTC vs. Revision 1.179 by root, Sat Apr 19 19:06:02 2008 UTC

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Comparing Coro/Coro.pm (file contents):
Revision 1.6 by root, Tue Jul 10 21:19:47 2001 UTC vs.
Revision 1.179 by root, Sat Apr 19 19:06:02 2008 UTC