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

Comparing Coro/Coro.pm (file contents):
Revision 1.3 by root, Tue Jul 3 04:02:31 2001 UTC vs.
Revision 1.222 by root, Tue Nov 18 08:59:46 2008 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	Coro - create and manage 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	$Coro::main->resume;	11	print "2\n";
12	print "in coroutine again, switching back\n";	12	cede; # yield back to main
13	$Coro::main->resume;	13	print "4\n";
14	};	14	};
15		15	print "1\n";
16	print "in main, switching to coroutine\n";	16	cede; # yield to coroutine
17	$new->resume;	17	print "3\n";
18	print "back in main, switch to coroutine again\n";	18	cede; # and again
19	$new->resume;	19
20	print "back in main\n";	20	# use locking
		21	use Coro::Semaphore;
		22	my $lock = new Coro::Semaphore;
		23	my $locked;
		24
		25	$lock->down;
		26	$locked = 1;
		27	$lock->up;
21		28
22	=head1 DESCRIPTION	29	=head1 DESCRIPTION
23		30
24	This module implements coroutines. Coroutines, similar to continuations,	31	This module collection manages coroutines. Coroutines are similar to
25	allow you to run more than one "thread of execution" in parallel. Unlike	32	threads but don't (in general) run in parallel at the same time even
26	threads this, only voluntary switching is used so locking problems are	33	on SMP machines. The specific flavor of coroutine used in this module
27	greatly reduced.	34	also guarantees you that it will not switch between coroutines unless
		35	necessary, at easily-identified points in your program, so locking and
		36	parallel access are rarely an issue, making coroutine programming much
		37	safer and easier than threads programming.
28		38
29	Although this is the "main" module of the Coro family it provides only	39	Unlike a normal perl program, however, coroutines allow you to have
30	low-level functionality. See L<Coro::Process> and related modules for a	40	multiple running interpreters that share data, which is especially useful
31	more useful process abstraction including scheduling.	41	to code pseudo-parallel processes and for event-based programming, such as
		42	multiple HTTP-GET requests running concurrently. See L<Coro::AnyEvent> to
		43	learn more.
		44
		45	Coroutines are also useful because Perl has no support for threads (the so
		46	called "threads" that perl offers are nothing more than the (bad) process
		47	emulation coming from the Windows platform: On standard operating systems
		48	they serve no purpose whatsoever, except by making your programs slow and
		49	making them use a lot of memory. Best disable them when building perl, or
		50	aks your software vendor/distributor to do it for you).
		51
		52	In this module, coroutines are defined as "callchain + lexical variables +
		53	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
		54	its own set of lexicals and its own set of perls most important global
		55	variables (see L<Coro::State> for more configuration).
		56
		57	=cut
		58
		59	package Coro;
		60
		61	use strict qw(vars subs);
		62	no warnings "uninitialized";
		63
		64	use Coro::State;
		65
		66	use base qw(Coro::State Exporter);
		67
		68	our $idle; # idle handler
		69	our $main; # main coroutine
		70	our $current; # current coroutine
		71
		72	our $VERSION = 5.0;
		73
		74	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
		75	our %EXPORT_TAGS = (
		76	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		77	);
		78	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
32		79
33	=over 4	80	=over 4
34		81
35	=cut
36
37	package Coro;
38
39	BEGIN {
40	$VERSION = 0.01;
41
42	require XSLoader;
43	XSLoader::load Coro, $VERSION;
44	}
45
46	=item $main	82	=item $Coro::main
47		83
48	This coroutine represents the main program.	84	This variable stores the coroutine object that represents the main
		85	program. While you cna C<ready> it and do most other things you can do to
		86	coroutines, it is mainly useful to compare again C<$Coro::current>, to see
		87	whether you are running in the main program or not.
49		88
		89	=cut
		90
		91	# $main is now being initialised by Coro::State
		92
50	=item $current	93	=item $Coro::current
51		94
52	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).	95	The coroutine object representing the current coroutine (the last
		96	coroutine that the Coro scheduler switched to). The initial value is
		97	C<$Coro::main> (of course).
53		98
54	=cut	99	This variable is B<strictly> I<read-only>. You can take copies of the
		100	value stored in it and use it as any other coroutine object, but you must
		101	not otherwise modify the variable itself.
55		102
56	$main = $current = _newprocess {	103	=cut
57	# never being called	104
		105	sub current() { $current } # [DEPRECATED]
		106
		107	=item $Coro::idle
		108
		109	This variable is mainly useful to integrate Coro into event loops. It is
		110	usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is
		111	pretty low-level functionality.
		112
		113	This variable stores a callback that is called whenever the scheduler
		114	finds no ready coroutines to run. The default implementation prints
		115	"FATAL: deadlock detected" and exits, because the program has no other way
		116	to continue.
		117
		118	This hook is overwritten by modules such as C<Coro::Timer> and
		119	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
		120	coroutine so the scheduler can run it.
		121
		122	Note that the callback I<must not>, under any circumstances, block
		123	the current coroutine. Normally, this is achieved by having an "idle
		124	coroutine" that calls the event loop and then blocks again, and then
		125	readying that coroutine in the idle handler.
		126
		127	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
		128	technique.
		129
		130	Please note that if your callback recursively invokes perl (e.g. for event
		131	handlers), then it must be prepared to be called recursively itself.
		132
		133	=cut
		134
		135	$idle = sub {
		136	require Carp;
		137	Carp::croak ("FATAL: deadlock detected");
58	};	138	};
59		139
60	=item $error, $error_msg, $error_coro	140	sub _cancel {
		141	my ($self) = @_;
61		142
62	This coroutine will be called on fatal errors. C<$error_msg> and	143	# free coroutine data and mark as destructed
63	C<$error_coro> return the error message and the error-causing coroutine,	144	$self->_destroy
64	respectively.	145	or return;
65		146
66	=cut	147	# call all destruction callbacks
		148	$_->(@{$self->{_status}})
		149	for @{ delete $self->{_on_destroy} \|\| [] };
		150	}
67		151
68	$error_msg =	152	# this coroutine is necessary because a coroutine
69	$error_coro = undef;	153	# cannot destroy itself.
		154	my @destroy;
		155	my $manager;
70		156
71	$error = _newprocess {	157	$manager = new Coro sub {
72	print STDERR "FATAL: $error_msg\nprogram aborted\n";	158	while () {
73	exit 250;	159	(shift @destroy)->_cancel
		160	while @destroy;
		161
		162	&schedule;
		163	}
74	};	164	};
		165	$manager->{desc} = "[coro manager]";
		166	$manager->prio (PRIO_MAX);
75		167
76	=item $coro = new $coderef [, @args]	168	=back
77		169
78	Create a new coroutine and return it. The first C<resume> call to this	170	=head2 SIMPLE COROUTINE CREATION
79	coroutine will start execution at the given coderef. If it returns it
80	should return a coroutine to switch to. If, after returning, the coroutine
81	is C<resume>d again it starts execution again at the givne coderef.
82		171
		172	=over 4
		173
		174	=item async { ... } [@args...]
		175
		176	Create a new coroutine and return it's coroutine object (usually
		177	unused). The coroutine will be put into the ready queue, so
		178	it will start running automatically on the next scheduler run.
		179
		180	The first argument is a codeblock/closure that should be executed in the
		181	coroutine. When it returns argument returns the coroutine is automatically
		182	terminated.
		183
		184	The remaining arguments are passed as arguments to the closure.
		185
		186	See the C<Coro::State::new> constructor for info about the coroutine
		187	environment in which coroutines are executed.
		188
		189	Calling C<exit> in a coroutine will do the same as calling exit outside
		190	the coroutine. Likewise, when the coroutine dies, the program will exit,
		191	just as it would in the main program.
		192
		193	If you do not want that, you can provide a default C<die> handler, or
		194	simply avoid dieing (by use of C<eval>).
		195
		196	Example: Create a new coroutine that just prints its arguments.
		197
		198	async {
		199	print "@_\n";
		200	} 1,2,3,4;
		201
83	=cut	202	=cut
		203
		204	sub async(&@) {
		205	my $coro = new Coro @_;
		206	$coro->ready;
		207	$coro
		208	}
		209
		210	=item async_pool { ... } [@args...]
		211
		212	Similar to C<async>, but uses a coroutine pool, so you should not call
		213	terminate or join on it (although you are allowed to), and you get a
		214	coroutine that might have executed other code already (which can be good
		215	or bad :).
		216
		217	On the plus side, this function is faster than creating (and destroying)
		218	a completly new coroutine, so if you need a lot of generic coroutines in
		219	quick successsion, use C<async_pool>, not C<async>.
		220
		221	The code block is executed in an C<eval> context and a warning will be
		222	issued in case of an exception instead of terminating the program, as
		223	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		224	will not work in the expected way, unless you call terminate or cancel,
		225	which somehow defeats the purpose of pooling (but is fine in the
		226	exceptional case).
		227
		228	The priority will be reset to C<0> after each run, tracing will be
		229	disabled, the description will be reset and the default output filehandle
		230	gets restored, so you can change all these. Otherwise the coroutine will
		231	be re-used "as-is": most notably if you change other per-coroutine global
		232	stuff such as C<$/> you I<must needs> revert that change, which is most
		233	simply done by using local as in: C<< local $/ >>.
		234
		235	The idle pool size is limited to C<8> idle coroutines (this can be
		236	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
		237	coros as required.
		238
		239	If you are concerned about pooled coroutines growing a lot because a
		240	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		241	{ terminate }> once per second or so to slowly replenish the pool. In
		242	addition to that, when the stacks used by a handler grows larger than 16kb
		243	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
		244
		245	=cut
		246
		247	our $POOL_SIZE = 8;
		248	our $POOL_RSS = 16 * 1024;
		249	our @async_pool;
		250
		251	sub pool_handler {
		252	my $cb;
		253
		254	while () {
		255	eval {
		256	while () {
		257	_pool_1 $cb;
		258	&$cb;
		259	_pool_2 $cb;
		260	&schedule;
		261	}
		262	};
		263
		264	if ($@) {
		265	last if $@ eq "\3async_pool terminate\2\n";
		266	warn $@;
		267	}
		268	}
		269	}
		270
		271	sub async_pool(&@) {
		272	# this is also inlined into the unblock_scheduler
		273	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		274
		275	$coro->{_invoke} = [@_];
		276	$coro->ready;
		277
		278	$coro
		279	}
		280
		281	=back
		282
		283	=head2 STATIC METHODS
		284
		285	Static methods are actually functions that operate on the current coroutine.
		286
		287	=over 4
		288
		289	=item schedule
		290
		291	Calls the scheduler. The scheduler will find the next coroutine that is
		292	to be run from the ready queue and switches to it. The next coroutine
		293	to be run is simply the one with the highest priority that is longest
		294	in its ready queue. If there is no coroutine ready, it will clal the
		295	C<$Coro::idle> hook.
		296
		297	Please note that the current coroutine will I<not> be put into the ready
		298	queue, so calling this function usually means you will never be called
		299	again unless something else (e.g. an event handler) calls C<< ->ready >>,
		300	thus waking you up.
		301
		302	This makes C<schedule> I<the> generic method to use to block the current
		303	coroutine and wait for events: first you remember the current coroutine in
		304	a variable, then arrange for some callback of yours to call C<< ->ready
		305	>> on that once some event happens, and last you call C<schedule> to put
		306	yourself to sleep. Note that a lot of things can wake your coroutine up,
		307	so you need to check whether the event indeed happened, e.g. by storing the
		308	status in a variable.
		309
		310	The canonical way to wait on external events is this:
		311
		312	{
		313	# remember current coroutine
		314	my $current = $Coro::current;
		315
		316	# register a hypothetical event handler
		317	on_event_invoke sub {
		318	# wake up sleeping coroutine
		319	$current->ready;
		320	undef $current;
		321	};
		322
		323	# call schedule until event occurred.
		324	# in case we are woken up for other reasons
		325	# (current still defined), loop.
		326	Coro::schedule while $current;
		327	}
		328
		329	=item cede
		330
		331	"Cede" to other coroutines. This function puts the current coroutine into
		332	the ready queue and calls C<schedule>, which has the effect of giving
		333	up the current "timeslice" to other coroutines of the same or higher
		334	priority. Once your coroutine gets its turn again it will automatically be
		335	resumed.
		336
		337	This function is often called C<yield> in other languages.
		338
		339	=item Coro::cede_notself
		340
		341	Works like cede, but is not exported by default and will cede to I<any>
		342	coroutine, regardless of priority. This is useful sometimes to ensure
		343	progress is made.
		344
		345	=item terminate [arg...]
		346
		347	Terminates the current coroutine with the given status values (see L<cancel>).
		348
		349	=item killall
		350
		351	Kills/terminates/cancels all coroutines except the currently running
		352	one. This is useful after a fork, either in the child or the parent, as
		353	usually only one of them should inherit the running coroutines.
		354
		355	Note that while this will try to free some of the main programs resources,
		356	you cannot free all of them, so if a coroutine that is not the main
		357	program calls this function, there will be some one-time resource leak.
		358
		359	=cut
		360
		361	sub terminate {
		362	$current->cancel (@_);
		363	}
		364
		365	sub killall {
		366	for (Coro::State::list) {
		367	$_->cancel
		368	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		369	}
		370	}
		371
		372	=back
		373
		374	=head2 COROUTINE METHODS
		375
		376	These are the methods you can call on coroutine objects (or to create
		377	them).
		378
		379	=over 4
		380
		381	=item new Coro \&sub [, @args...]
		382
		383	Create a new coroutine and return it. When the sub returns, the coroutine
		384	automatically terminates as if C<terminate> with the returned values were
		385	called. To make the coroutine run you must first put it into the ready
		386	queue by calling the ready method.
		387
		388	See C<async> and C<Coro::State::new> for additional info about the
		389	coroutine environment.
		390
		391	=cut
		392
		393	sub _run_coro {
		394	terminate &{+shift};
		395	}
84		396
85	sub new {	397	sub new {
86	my $class = $_[0];	398	my $class = shift;
87	my $proc = $_[1];	399
88	bless _newprocess {	400	$class->SUPER::new (\&_run_coro, @_)
89	do {	401	}
90	eval { &$proc->resume };	402
91	if ($@) {	403	=item $success = $coroutine->ready
92	($error_msg, $error_coro) = ($@, $current);	404
93	$error->resume;	405	Put the given coroutine into the end of its ready queue (there is one
		406	queue for each priority) and return true. If the coroutine is already in
		407	the ready queue, do nothing and return false.
		408
		409	This ensures that the scheduler will resume this coroutine automatically
		410	once all the coroutines of higher priority and all coroutines of the same
		411	priority that were put into the ready queue earlier have been resumed.
		412
		413	=item $is_ready = $coroutine->is_ready
		414
		415	Return whether the coroutine is currently the ready queue or not,
		416
		417	=item $coroutine->cancel (arg...)
		418
		419	Terminates the given coroutine and makes it return the given arguments as
		420	status (default: the empty list). Never returns if the coroutine is the
		421	current coroutine.
		422
		423	=cut
		424
		425	sub cancel {
		426	my $self = shift;
		427	$self->{_status} = [@_];
		428
		429	if ($current == $self) {
		430	push @destroy, $self;
		431	$manager->ready;
		432	&schedule while 1;
		433	} else {
		434	$self->_cancel;
		435	}
		436	}
		437
		438	=item $coroutine->throw ([$scalar])
		439
		440	If C<$throw> is specified and defined, it will be thrown as an exception
		441	inside the coroutine at the next convenient point in time. Otherwise
		442	clears the exception object.
		443
		444	Coro will check for the exception each time a schedule-like-function
		445	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		446	>>, C<< Coro::Handle->readable >> and so on. Note that this means that
		447	when a coroutine is acquiring a lock, it might only throw after it has
		448	sucessfully acquired it.
		449
		450	The exception object will be thrown "as is" with the specified scalar in
		451	C<$@>, i.e. if it is a string, no line number or newline will be appended
		452	(unlike with C<die>).
		453
		454	This can be used as a softer means than C<cancel> to ask a coroutine to
		455	end itself, although there is no guarantee that the exception will lead to
		456	termination, and if the exception isn't caught it might well end the whole
		457	program.
		458
		459	You might also think of C<throw> as being the moral equivalent of
		460	C<kill>ing a coroutine with a signal (in this case, a scalar).
		461
		462	=item $coroutine->join
		463
		464	Wait until the coroutine terminates and return any values given to the
		465	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		466	from multiple coroutines, and all will be resumed and given the status
		467	return once the C<$coroutine> terminates.
		468
		469	=cut
		470
		471	sub join {
		472	my $self = shift;
		473
		474	unless ($self->{_status}) {
		475	my $current = $current;
		476
		477	push @{$self->{_on_destroy}}, sub {
		478	$current->ready;
		479	undef $current;
		480	};
		481
		482	&schedule while $current;
		483	}
		484
		485	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		486	}
		487
		488	=item $coroutine->on_destroy (\&cb)
		489
		490	Registers a callback that is called when this coroutine gets destroyed,
		491	but before it is joined. The callback gets passed the terminate arguments,
		492	if any, and I<must not> die, under any circumstances.
		493
		494	=cut
		495
		496	sub on_destroy {
		497	my ($self, $cb) = @_;
		498
		499	push @{ $self->{_on_destroy} }, $cb;
		500	}
		501
		502	=item $oldprio = $coroutine->prio ($newprio)
		503
		504	Sets (or gets, if the argument is missing) the priority of the
		505	coroutine. Higher priority coroutines get run before lower priority
		506	coroutines. Priorities are small signed integers (currently -4 .. +3),
		507	that you can refer to using PRIO_xxx constants (use the import tag :prio
		508	to get then):
		509
		510	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		511	3 > 1 > 0 > -1 > -3 > -4
		512
		513	# set priority to HIGH
		514	current->prio(PRIO_HIGH);
		515
		516	The idle coroutine ($Coro::idle) always has a lower priority than any
		517	existing coroutine.
		518
		519	Changing the priority of the current coroutine will take effect immediately,
		520	but changing the priority of coroutines in the ready queue (but not
		521	running) will only take effect after the next schedule (of that
		522	coroutine). This is a bug that will be fixed in some future version.
		523
		524	=item $newprio = $coroutine->nice ($change)
		525
		526	Similar to C<prio>, but subtract the given value from the priority (i.e.
		527	higher values mean lower priority, just as in unix).
		528
		529	=item $olddesc = $coroutine->desc ($newdesc)
		530
		531	Sets (or gets in case the argument is missing) the description for this
		532	coroutine. This is just a free-form string you can associate with a
		533	coroutine.
		534
		535	This method simply sets the C<< $coroutine->{desc} >> member to the given
		536	string. You can modify this member directly if you wish.
		537
		538	=cut
		539
		540	sub desc {
		541	my $old = $_[0]{desc};
		542	$_[0]{desc} = $_[1] if @_ > 1;
		543	$old;
		544	}
		545
		546	=back
		547
		548	=head2 GLOBAL FUNCTIONS
		549
		550	=over 4
		551
		552	=item Coro::nready
		553
		554	Returns the number of coroutines that are currently in the ready state,
		555	i.e. that can be switched to by calling C<schedule> directory or
		556	indirectly. The value C<0> means that the only runnable coroutine is the
		557	currently running one, so C<cede> would have no effect, and C<schedule>
		558	would cause a deadlock unless there is an idle handler that wakes up some
		559	coroutines.
		560
		561	=item my $guard = Coro::guard { ... }
		562
		563	This creates and returns a guard object. Nothing happens until the object
		564	gets destroyed, in which case the codeblock given as argument will be
		565	executed. This is useful to free locks or other resources in case of a
		566	runtime error or when the coroutine gets canceled, as in both cases the
		567	guard block will be executed. The guard object supports only one method,
		568	C<< ->cancel >>, which will keep the codeblock from being executed.
		569
		570	Example: set some flag and clear it again when the coroutine gets canceled
		571	or the function returns:
		572
		573	sub do_something {
		574	my $guard = Coro::guard { $busy = 0 };
		575	$busy = 1;
		576
		577	# do something that requires $busy to be true
		578	}
		579
		580	=cut
		581
		582	sub guard(&) {
		583	bless \(my $cb = $_[0]), "Coro::guard"
		584	}
		585
		586	sub Coro::guard::cancel {
		587	${$_[0]} = sub { };
		588	}
		589
		590	sub Coro::guard::DESTROY {
		591	${$_[0]}->();
		592	}
		593
		594
		595	=item unblock_sub { ... }
		596
		597	This utility function takes a BLOCK or code reference and "unblocks" it,
		598	returning a new coderef. Unblocking means that calling the new coderef
		599	will return immediately without blocking, returning nothing, while the
		600	original code ref will be called (with parameters) from within another
		601	coroutine.
		602
		603	The reason this function exists is that many event libraries (such as the
		604	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		605	of thread-safety). This means you must not block within event callbacks,
		606	otherwise you might suffer from crashes or worse. The only event library
		607	currently known that is safe to use without C<unblock_sub> is L<EV>.
		608
		609	This function allows your callbacks to block by executing them in another
		610	coroutine where it is safe to block. One example where blocking is handy
		611	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		612	disk, for example.
		613
		614	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		615	creating event callbacks that want to block.
		616
		617	If your handler does not plan to block (e.g. simply sends a message to
		618	another coroutine, or puts some other coroutine into the ready queue),
		619	there is no reason to use C<unblock_sub>.
		620
		621	Note that you also need to use C<unblock_sub> for any other callbacks that
		622	are indirectly executed by any C-based event loop. For example, when you
		623	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		624	provides callbacks that are the result of some event callback, then you
		625	must not block either, or use C<unblock_sub>.
		626
		627	=cut
		628
		629	our @unblock_queue;
		630
		631	# we create a special coro because we want to cede,
		632	# to reduce pressure on the coro pool (because most callbacks
		633	# return immediately and can be reused) and because we cannot cede
		634	# inside an event callback.
		635	our $unblock_scheduler = new Coro sub {
		636	while () {
		637	while (my $cb = pop @unblock_queue) {
		638	# this is an inlined copy of async_pool
		639	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		640
		641	$coro->{_invoke} = $cb;
		642	$coro->ready;
		643	cede; # for short-lived callbacks, this reduces pressure on the coro pool
94	}	644	}
95	} while ();	645	schedule; # sleep well
96	}, $class;	646	}
97	}	647	};
		648	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
98		649
99	=item $coro->resume	650	sub unblock_sub(&) {
		651	my $cb = shift;
100		652
101	Resume execution at the given coroutine.	653	sub {
102		654	unshift @unblock_queue, [$cb, @_];
103	=cut	655	$unblock_scheduler->ready;
104		656	}
105	my $prev;
106
107	sub resume {
108	$prev = $current; $current = $_[0];
109	_transfer($prev, $current);
110	}	657	}
		658
		659	=back
		660
		661	=cut
111		662
112	1;	663	1;
113		664
		665	=head1 BUGS/LIMITATIONS
		666
		667	=over 4
		668
		669	=item fork with pthread backend
		670
		671	When Coro is compiled using the pthread backend (which isn't recommended
		672	but required on many BSDs as their libcs are completely broken), then
		673	coroutines will not survive a fork. There is no known workaround except to
		674	fix your libc and use a saner backend.
		675
		676	=item perl process emulation ("threads")
		677
		678	This module is not perl-pseudo-thread-safe. You should only ever use this
		679	module from the same thread (this requirement might be removed in the
		680	future to allow per-thread schedulers, but Coro::State does not yet allow
		681	this). I recommend disabling thread support and using processes, as having
		682	the windows process emulation enabled under unix roughly halves perl
		683	performance, even when not used.
		684
		685	=item coroutine switching not signal safe
		686
		687	You must not switch to another coroutine from within a signal handler
		688	(only relevant with %SIG - most event libraries provide safe signals).
		689
		690	That means you I<MUST NOT> call any function that might "block" the
		691	current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		692	anything that calls those. Everything else, including calling C<ready>,
		693	works.
		694
114	=back	695	=back
115		696
116	=head1 BUGS
117
118	This module has not yet been extensively tested.
119		697
120	=head1 SEE ALSO	698	=head1 SEE ALSO
121		699
122	L<Coro::Process>, L<Coro::Signal>.	700	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		701
		702	Debugging: L<Coro::Debug>.
		703
		704	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
		705
		706	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		707
		708	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
		709
		710	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.
		711
		712	XS API: L<Coro::MakeMaker>.
		713
		714	Low level Configuration, Coroutine Environment: L<Coro::State>.
123		715
124	=head1 AUTHOR	716	=head1 AUTHOR
125		717
126	Marc Lehmann <pcg@goof.com>	718	Marc Lehmann <schmorp@schmorp.de>
127	http://www.goof.com/pcg/marc/	719	http://home.schmorp.de/
128		720
129	=cut	721	=cut
130		722

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Comparing Coro/Coro.pm (file contents):
Revision 1.3 by root, Tue Jul 3 04:02:31 2001 UTC vs.
Revision 1.222 by root, Tue Nov 18 08:59:46 2008 UTC