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

Comparing Coro/Coro.pm (file contents):
Revision 1.11 by root, Sun Jul 15 03:24:18 2001 UTC vs.
Revision 1.250 by root, Wed Dec 17 04:57:07 2008 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	Coro - coroutine process abstraction	3	Coro - the only real threads in perl
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use Coro;	7	use Coro;
8		8
9	async {	9	async {
10	# some asynchronous thread of execution	10	# some asynchronous thread of execution
		11	print "2\n";
		12	cede; # yield back to main
		13	print "4\n";
11	};	14	};
12		15	print "1\n";
13	# alternatively create an async process like this:	16	cede; # yield to coro
14		17	print "3\n";
15	sub some_func : Coro {	18	cede; # and again
16	# some more async code	19
17	}	20	# use locking
18		21	use Coro::Semaphore;
19	yield;	22	my $lock = new Coro::Semaphore;
		23	my $locked;
		24
		25	$lock->down;
		26	$locked = 1;
		27	$lock->up;
20		28
21	=head1 DESCRIPTION	29	=head1 DESCRIPTION
22		30
		31	For a tutorial-style introduction, please read the L<Coro::Intro>
		32	manpage. This manpage mainly contains reference information.
		33
		34	This module collection manages continuations in general, most often in
		35	the form of cooperative threads (also called coros, or simply "coro"
		36	in the documentation). They are similar to kernel threads but don't (in
		37	general) run in parallel at the same time even on SMP machines. The
		38	specific flavor of thread offered by this module also guarantees you that
		39	it will not switch between threads unless necessary, at easily-identified
		40	points in your program, so locking and parallel access are rarely an
		41	issue, making thread programming much safer and easier than using other
		42	thread models.
		43
		44	Unlike the so-called "Perl threads" (which are not actually real threads
		45	but only the windows process emulation ported to unix, and as such act
		46	as processes), Coro provides a full shared address space, which makes
		47	communication between threads very easy. And Coro's threads are fast,
		48	too: disabling the Windows process emulation code in your perl and using
		49	Coro can easily result in a two to four times speed increase for your
		50	programs. A parallel matrix multiplication benchmark runs over 300 times
		51	faster on a single core than perl's pseudo-threads on a quad core using
		52	all four cores.
		53
		54	Coro achieves that by supporting multiple running interpreters that share
		55	data, which is especially useful to code pseudo-parallel processes and
		56	for event-based programming, such as multiple HTTP-GET requests running
		57	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
		58	into an event-based environment.
		59
		60	In this module, a thread is defined as "callchain + lexical variables +
		61	some package variables + C stack), that is, a thread has its own callchain,
		62	its own set of lexicals and its own set of perls most important global
		63	variables (see L<Coro::State> for more configuration and background info).
		64
		65	See also the C<SEE ALSO> section at the end of this document - the Coro
		66	module family is quite large.
		67
23	=cut	68	=cut
24		69
25	package Coro;	70	package Coro;
26		71
		72	use strict qw(vars subs);
		73	no warnings "uninitialized";
		74
		75	use Guard ();
		76
27	use Coro::State;	77	use Coro::State;
28		78
29	use base Exporter;	79	use base qw(Coro::State Exporter);
30		80
31	$VERSION = 0.04;	81	our $idle; # idle handler
		82	our $main; # main coro
		83	our $current; # current coro
32		84
33	@EXPORT = qw(async yield schedule);	85	our $VERSION = 5.13;
34	@EXPORT_OK = qw($current);
35		86
36	{	87	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
37	use subs 'async';	88	our %EXPORT_TAGS = (
		89	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		90	);
		91	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
38		92
39	my @async;	93	=head1 GLOBAL VARIABLES
40		94
41	# this way of handling attributes simply is NOT scalable ;()	95	=over 4
42	sub import {	96
43	Coro->export_to_level(1, @_);	97	=item $Coro::main
44	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};	98
45	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {	99	This variable stores the Coro object that represents the main
46	my ($package, $ref) = (shift, shift);	100	program. While you cna C<ready> it and do most other things you can do to
47	my @attrs;	101	coro, it is mainly useful to compare again C<$Coro::current>, to see
48	for (@_) {	102	whether you are running in the main program or not.
49	if ($_ eq "Coro") {	103
50	push @async, $ref;	104	=cut
51	} else {	105
52	push @attrs, @_;	106	# $main is now being initialised by Coro::State
53	}	107
54	}	108	=item $Coro::current
55	return $old ? $old->($package, $name, @attrs) : @attrs;	109
		110	The Coro object representing the current coro (the last
		111	coro that the Coro scheduler switched to). The initial value is
		112	C<$Coro::main> (of course).
		113
		114	This variable is B<strictly> I<read-only>. You can take copies of the
		115	value stored in it and use it as any other Coro object, but you must
		116	not otherwise modify the variable itself.
		117
		118	=cut
		119
		120	sub current() { $current } # [DEPRECATED]
		121
		122	=item $Coro::idle
		123
		124	This variable is mainly useful to integrate Coro into event loops. It is
		125	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
		126	pretty low-level functionality.
		127
		128	This variable stores either a Coro object or a callback.
		129
		130	If it is a callback, the it is called whenever the scheduler finds no
		131	ready coros to run. The default implementation prints "FATAL:
		132	deadlock detected" and exits, because the program has no other way to
		133	continue.
		134
		135	If it is a coro object, then this object will be readied (without
		136	invoking any ready hooks, however) when the scheduler finds no other ready
		137	coros to run.
		138
		139	This hook is overwritten by modules such as C<Coro::EV> and
		140	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
		141	coro so the scheduler can run it.
		142
		143	Note that the callback I<must not>, under any circumstances, block
		144	the current coro. Normally, this is achieved by having an "idle
		145	coro" that calls the event loop and then blocks again, and then
		146	readying that coro in the idle handler, or by simply placing the idle
		147	coro in this variable.
		148
		149	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
		150	technique.
		151
		152	Please note that if your callback recursively invokes perl (e.g. for event
		153	handlers), then it must be prepared to be called recursively itself.
		154
		155	=cut
		156
		157	$idle = sub {
		158	require Carp;
		159	Carp::croak ("FATAL: deadlock detected");
		160	};
		161
		162	# this coro is necessary because a coro
		163	# cannot destroy itself.
		164	our @destroy;
		165	our $manager;
		166
		167	$manager = new Coro sub {
		168	while () {
		169	Coro::State::cancel shift @destroy
		170	while @destroy;
		171
		172	&schedule;
		173	}
		174	};
		175	$manager->{desc} = "[coro manager]";
		176	$manager->prio (PRIO_MAX);
		177
		178	=back
		179
		180	=head1 SIMPLE CORO CREATION
		181
		182	=over 4
		183
		184	=item async { ... } [@args...]
		185
		186	Create a new coro and return its Coro object (usually
		187	unused). The coro will be put into the ready queue, so
		188	it will start running automatically on the next scheduler run.
		189
		190	The first argument is a codeblock/closure that should be executed in the
		191	coro. When it returns argument returns the coro is automatically
		192	terminated.
		193
		194	The remaining arguments are passed as arguments to the closure.
		195
		196	See the C<Coro::State::new> constructor for info about the coro
		197	environment in which coro are executed.
		198
		199	Calling C<exit> in a coro will do the same as calling exit outside
		200	the coro. Likewise, when the coro dies, the program will exit,
		201	just as it would in the main program.
		202
		203	If you do not want that, you can provide a default C<die> handler, or
		204	simply avoid dieing (by use of C<eval>).
		205
		206	Example: Create a new coro that just prints its arguments.
		207
		208	async {
		209	print "@_\n";
		210	} 1,2,3,4;
		211
		212	=cut
		213
		214	sub async(&@) {
		215	my $coro = new Coro @_;
		216	$coro->ready;
		217	$coro
		218	}
		219
		220	=item async_pool { ... } [@args...]
		221
		222	Similar to C<async>, but uses a coro pool, so you should not call
		223	terminate or join on it (although you are allowed to), and you get a
		224	coro that might have executed other code already (which can be good
		225	or bad :).
		226
		227	On the plus side, this function is about twice as fast as creating (and
		228	destroying) a completely new coro, so if you need a lot of generic
		229	coros in quick successsion, use C<async_pool>, not C<async>.
		230
		231	The code block is executed in an C<eval> context and a warning will be
		232	issued in case of an exception instead of terminating the program, as
		233	C<async> does. As the coro is being reused, stuff like C<on_destroy>
		234	will not work in the expected way, unless you call terminate or cancel,
		235	which somehow defeats the purpose of pooling (but is fine in the
		236	exceptional case).
		237
		238	The priority will be reset to C<0> after each run, tracing will be
		239	disabled, the description will be reset and the default output filehandle
		240	gets restored, so you can change all these. Otherwise the coro will
		241	be re-used "as-is": most notably if you change other per-coro global
		242	stuff such as C<$/> you I<must needs> revert that change, which is most
		243	simply done by using local as in: C<< local $/ >>.
		244
		245	The idle pool size is limited to C<8> idle coros (this can be
		246	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
		247	coros as required.
		248
		249	If you are concerned about pooled coros growing a lot because a
		250	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		251	{ terminate }> once per second or so to slowly replenish the pool. In
		252	addition to that, when the stacks used by a handler grows larger than 32kb
		253	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
		254
		255	=cut
		256
		257	our $POOL_SIZE = 8;
		258	our $POOL_RSS = 32 * 1024;
		259	our @async_pool;
		260
		261	sub pool_handler {
		262	while () {
		263	eval {
		264	&{&_pool_handler} while 1;
56	};	265	};
		266
		267	warn $@ if $@;
57	}	268	}
		269	}
58		270
59	sub INIT {	271	=back
60	async pop @async while @async;	272
		273	=head1 STATIC METHODS
		274
		275	Static methods are actually functions that implicitly operate on the
		276	current coro.
		277
		278	=over 4
		279
		280	=item schedule
		281
		282	Calls the scheduler. The scheduler will find the next coro that is
		283	to be run from the ready queue and switches to it. The next coro
		284	to be run is simply the one with the highest priority that is longest
		285	in its ready queue. If there is no coro ready, it will clal the
		286	C<$Coro::idle> hook.
		287
		288	Please note that the current coro will I<not> be put into the ready
		289	queue, so calling this function usually means you will never be called
		290	again unless something else (e.g. an event handler) calls C<< ->ready >>,
		291	thus waking you up.
		292
		293	This makes C<schedule> I<the> generic method to use to block the current
		294	coro and wait for events: first you remember the current coro in
		295	a variable, then arrange for some callback of yours to call C<< ->ready
		296	>> on that once some event happens, and last you call C<schedule> to put
		297	yourself to sleep. Note that a lot of things can wake your coro up,
		298	so you need to check whether the event indeed happened, e.g. by storing the
		299	status in a variable.
		300
		301	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
		302
		303	=item cede
		304
		305	"Cede" to other coros. This function puts the current coro into
		306	the ready queue and calls C<schedule>, which has the effect of giving
		307	up the current "timeslice" to other coros of the same or higher
		308	priority. Once your coro gets its turn again it will automatically be
		309	resumed.
		310
		311	This function is often called C<yield> in other languages.
		312
		313	=item Coro::cede_notself
		314
		315	Works like cede, but is not exported by default and will cede to I<any>
		316	coro, regardless of priority. This is useful sometimes to ensure
		317	progress is made.
		318
		319	=item terminate [arg...]
		320
		321	Terminates the current coro with the given status values (see L<cancel>).
		322
		323	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
		324
		325	These function install enter and leave winders in the current scope. The
		326	enter block will be executed when on_enter is called and whenever the
		327	current coro is re-entered by the scheduler, while the leave block is
		328	executed whenever the current coro is blocked by the scheduler, and
		329	also when the containing scope is exited (by whatever means, be it exit,
		330	die, last etc.).
		331
		332	I<Neither invoking the scheduler, nor exceptions, are allowed within those
		333	BLOCKs>. That means: do not even think about calling C<die> without an
		334	eval, and do not even think of entering the scheduler in any way.
		335
		336	Since both BLOCKs are tied to the current scope, they will automatically
		337	be removed when the current scope exits.
		338
		339	These functions implement the same concept as C<dynamic-wind> in scheme
		340	does, and are useful when you want to localise some resource to a specific
		341	coro.
		342
		343	They slow down coro switching considerably for coros that use
		344	them (But coro switching is still reasonably fast if the handlers are
		345	fast).
		346
		347	These functions are best understood by an example: The following function
		348	will change the current timezone to "Antarctica/South_Pole", which
		349	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
		350	which remember/change the current timezone and restore the previous
		351	value, respectively, the timezone is only changes for the coro that
		352	installed those handlers.
		353
		354	use POSIX qw(tzset);
		355
		356	async {
		357	my $old_tz; # store outside TZ value here
		358
		359	Coro::on_enter {
		360	$old_tz = $ENV{TZ}; # remember the old value
		361
		362	$ENV{TZ} = "Antarctica/South_Pole";
		363	tzset; # enable new value
		364	};
		365
		366	Coro::on_leave {
		367	$ENV{TZ} = $old_tz;
		368	tzset; # restore old value
		369	};
		370
		371	# at this place, the timezone is Antarctica/South_Pole,
		372	# without disturbing the TZ of any other coro.
		373	};
		374
		375	This can be used to localise about any resource (locale, uid, current
		376	working directory etc.) to a block, despite the existance of other
		377	coros.
		378
		379	=item killall
		380
		381	Kills/terminates/cancels all coros except the currently running one.
		382
		383	Note that while this will try to free some of the main interpreter
		384	resources if the calling coro isn't the main coro, but one
		385	cannot free all of them, so if a coro that is not the main coro
		386	calls this function, there will be some one-time resource leak.
		387
		388	=cut
		389
		390	sub killall {
		391	for (Coro::State::list) {
		392	$_->cancel
		393	if $_ != $current && UNIVERSAL::isa $_, "Coro";
61	}	394	}
62	}	395	}
63		396
64	=item $main	397	=back
65		398
66	This coroutine represents the main program.	399	=head1 CORO OBJECT METHODS
67		400
68	=cut	401	These are the methods you can call on coro objects (or to create
		402	them).
69		403
70	our $main = new Coro;	404	=over 4
71		405
72	=item $current	406	=item new Coro \&sub [, @args...]
73		407
74	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).	408	Create a new coro and return it. When the sub returns, the coro
		409	automatically terminates as if C<terminate> with the returned values were
		410	called. To make the coro run you must first put it into the ready
		411	queue by calling the ready method.
75		412
76	=cut	413	See C<async> and C<Coro::State::new> for additional info about the
		414	coro environment.
77		415
78	# maybe some other module used Coro::Specific before...
79	if ($current) {
80	$main->{specific} = $current->{specific};
81	}
82
83	our $current = $main;
84
85	=item $idle
86
87	The coroutine to switch to when no other coroutine is running. The default
88	implementation prints "FATAL: deadlock detected" and exits.
89
90	=cut	416	=cut
91		417
92	# should be done using priorities :(	418	sub _coro_run {
		419	terminate &{+shift};
		420	}
		421
		422	=item $success = $coro->ready
		423
		424	Put the given coro into the end of its ready queue (there is one
		425	queue for each priority) and return true. If the coro is already in
		426	the ready queue, do nothing and return false.
		427
		428	This ensures that the scheduler will resume this coro automatically
		429	once all the coro of higher priority and all coro of the same
		430	priority that were put into the ready queue earlier have been resumed.
		431
		432	=item $coro->suspend
		433
		434	Suspends the specified coro. A suspended coro works just like any other
		435	coro, except that the scheduler will not select a suspended coro for
		436	execution.
		437
		438	Suspending a coro can be useful when you want to keep the coro from
		439	running, but you don't want to destroy it, or when you want to temporarily
		440	freeze a coro (e.g. for debugging) to resume it later.
		441
		442	A scenario for the former would be to suspend all (other) coros after a
		443	fork and keep them alive, so their destructors aren't called, but new
		444	coros can be created.
		445
		446	=item $coro->resume
		447
		448	If the specified coro was suspended, it will be resumed. Note that when
		449	the coro was in the ready queue when it was suspended, it might have been
		450	unreadied by the scheduler, so an activation might have been lost.
		451
		452	To avoid this, it is best to put a suspended coro into the ready queue
		453	unconditionally, as every synchronisation mechanism must protect itself
		454	against spurious wakeups, and the one in the Coro family certainly do
		455	that.
		456
		457	=item $is_ready = $coro->is_ready
		458
		459	Returns true iff the Coro object is in the ready queue. Unless the Coro
		460	object gets destroyed, it will eventually be scheduled by the scheduler.
		461
		462	=item $is_running = $coro->is_running
		463
		464	Returns true iff the Coro object is currently running. Only one Coro object
		465	can ever be in the running state (but it currently is possible to have
		466	multiple running Coro::States).
		467
		468	=item $is_suspended = $coro->is_suspended
		469
		470	Returns true iff this Coro object has been suspended. Suspended Coros will
		471	not ever be scheduled.
		472
		473	=item $coro->cancel (arg...)
		474
		475	Terminates the given Coro and makes it return the given arguments as
		476	status (default: the empty list). Never returns if the Coro is the
		477	current Coro.
		478
		479	=cut
		480
		481	sub cancel {
		482	my $self = shift;
		483
		484	if ($current == $self) {
		485	terminate @_;
		486	} else {
		487	$self->{_status} = [@_];
		488	Coro::State::cancel $self;
		489	}
		490	}
		491
		492	=item $coro->schedule_to
		493
		494	Puts the current coro to sleep (like C<Coro::schedule>), but instead
		495	of continuing with the next coro from the ready queue, always switch to
		496	the given coro object (regardless of priority etc.). The readyness
		497	state of that coro isn't changed.
		498
		499	This is an advanced method for special cases - I'd love to hear about any
		500	uses for this one.
		501
		502	=item $coro->cede_to
		503
		504	Like C<schedule_to>, but puts the current coro into the ready
		505	queue. This has the effect of temporarily switching to the given
		506	coro, and continuing some time later.
		507
		508	This is an advanced method for special cases - I'd love to hear about any
		509	uses for this one.
		510
		511	=item $coro->throw ([$scalar])
		512
		513	If C<$throw> is specified and defined, it will be thrown as an exception
		514	inside the coro at the next convenient point in time. Otherwise
		515	clears the exception object.
		516
		517	Coro will check for the exception each time a schedule-like-function
		518	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		519	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		520	detect this case and return early in case an exception is pending.
		521
		522	The exception object will be thrown "as is" with the specified scalar in
		523	C<$@>, i.e. if it is a string, no line number or newline will be appended
		524	(unlike with C<die>).
		525
		526	This can be used as a softer means than C<cancel> to ask a coro to
		527	end itself, although there is no guarantee that the exception will lead to
		528	termination, and if the exception isn't caught it might well end the whole
		529	program.
		530
		531	You might also think of C<throw> as being the moral equivalent of
		532	C<kill>ing a coro with a signal (in this case, a scalar).
		533
		534	=item $coro->join
		535
		536	Wait until the coro terminates and return any values given to the
		537	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		538	from multiple coro, and all will be resumed and given the status
		539	return once the C<$coro> terminates.
		540
		541	=cut
		542
		543	sub join {
		544	my $self = shift;
		545
		546	unless ($self->{_status}) {
		547	my $current = $current;
		548
		549	push @{$self->{_on_destroy}}, sub {
		550	$current->ready;
		551	undef $current;
		552	};
		553
		554	&schedule while $current;
		555	}
		556
		557	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		558	}
		559
		560	=item $coro->on_destroy (\&cb)
		561
		562	Registers a callback that is called when this coro gets destroyed,
		563	but before it is joined. The callback gets passed the terminate arguments,
		564	if any, and I<must not> die, under any circumstances.
		565
		566	=cut
		567
		568	sub on_destroy {
		569	my ($self, $cb) = @_;
		570
		571	push @{ $self->{_on_destroy} }, $cb;
		572	}
		573
		574	=item $oldprio = $coro->prio ($newprio)
		575
		576	Sets (or gets, if the argument is missing) the priority of the
		577	coro. Higher priority coro get run before lower priority
		578	coro. Priorities are small signed integers (currently -4 .. +3),
		579	that you can refer to using PRIO_xxx constants (use the import tag :prio
		580	to get then):
		581
		582	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		583	3 > 1 > 0 > -1 > -3 > -4
		584
		585	# set priority to HIGH
		586	current->prio (PRIO_HIGH);
		587
		588	The idle coro ($Coro::idle) always has a lower priority than any
		589	existing coro.
		590
		591	Changing the priority of the current coro will take effect immediately,
		592	but changing the priority of coro in the ready queue (but not
		593	running) will only take effect after the next schedule (of that
		594	coro). This is a bug that will be fixed in some future version.
		595
		596	=item $newprio = $coro->nice ($change)
		597
		598	Similar to C<prio>, but subtract the given value from the priority (i.e.
		599	higher values mean lower priority, just as in unix).
		600
		601	=item $olddesc = $coro->desc ($newdesc)
		602
		603	Sets (or gets in case the argument is missing) the description for this
		604	coro. This is just a free-form string you can associate with a
		605	coro.
		606
		607	This method simply sets the C<< $coro->{desc} >> member to the given
		608	string. You can modify this member directly if you wish.
		609
		610	=cut
		611
		612	sub desc {
		613	my $old = $_[0]{desc};
		614	$_[0]{desc} = $_[1] if @_ > 1;
		615	$old;
		616	}
		617
		618	sub transfer {
		619	require Carp;
		620	Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
		621	}
		622
		623	=back
		624
		625	=head1 GLOBAL FUNCTIONS
		626
		627	=over 4
		628
		629	=item Coro::nready
		630
		631	Returns the number of coro that are currently in the ready state,
		632	i.e. that can be switched to by calling C<schedule> directory or
		633	indirectly. The value C<0> means that the only runnable coro is the
		634	currently running one, so C<cede> would have no effect, and C<schedule>
		635	would cause a deadlock unless there is an idle handler that wakes up some
		636	coro.
		637
		638	=item my $guard = Coro::guard { ... }
		639
		640	This function still exists, but is deprecated. Please use the
		641	C<Guard::guard> function instead.
		642
		643	=cut
		644
		645	BEGIN { *guard = \&Guard::guard }
		646
		647	=item unblock_sub { ... }
		648
		649	This utility function takes a BLOCK or code reference and "unblocks" it,
		650	returning a new coderef. Unblocking means that calling the new coderef
		651	will return immediately without blocking, returning nothing, while the
		652	original code ref will be called (with parameters) from within another
		653	coro.
		654
		655	The reason this function exists is that many event libraries (such as the
		656	venerable L<Event\|Event> module) are not thread-safe (a weaker form
		657	of reentrancy). This means you must not block within event callbacks,
		658	otherwise you might suffer from crashes or worse. The only event library
		659	currently known that is safe to use without C<unblock_sub> is L<EV>.
		660
		661	This function allows your callbacks to block by executing them in another
		662	coro where it is safe to block. One example where blocking is handy
		663	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		664	disk, for example.
		665
		666	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		667	creating event callbacks that want to block.
		668
		669	If your handler does not plan to block (e.g. simply sends a message to
		670	another coro, or puts some other coro into the ready queue), there is
		671	no reason to use C<unblock_sub>.
		672
		673	Note that you also need to use C<unblock_sub> for any other callbacks that
		674	are indirectly executed by any C-based event loop. For example, when you
		675	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		676	provides callbacks that are the result of some event callback, then you
		677	must not block either, or use C<unblock_sub>.
		678
		679	=cut
		680
		681	our @unblock_queue;
		682
		683	# we create a special coro because we want to cede,
		684	# to reduce pressure on the coro pool (because most callbacks
		685	# return immediately and can be reused) and because we cannot cede
		686	# inside an event callback.
93	our $idle = new Coro sub {	687	our $unblock_scheduler = new Coro sub {
94	print STDERR "FATAL: deadlock detected\n";	688	while () {
95	exit(51);	689	while (my $cb = pop @unblock_queue) {
		690	&async_pool (@$cb);
		691
		692	# for short-lived callbacks, this reduces pressure on the coro pool
		693	# as the chance is very high that the async_poll coro will be back
		694	# in the idle state when cede returns
		695	cede;
		696	}
		697	schedule; # sleep well
		698	}
96	};	699	};
		700	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
97		701
98	# we really need priorities...	702	sub unblock_sub(&) {
99	my @ready = (); # the ready queue. hehe, rather broken ;)	703	my $cb = shift;
100		704
101	# static methods. not really.	705	sub {
		706	unshift @unblock_queue, [$cb, @_];
		707	$unblock_scheduler->ready;
		708	}
		709	}
102		710
103	=head2 STATIC METHODS	711	=item $cb = Coro::rouse_cb
104		712
105	Static methods are actually functions that operate on the current process only.	713	Create and return a "rouse callback". That's a code reference that,
		714	when called, will remember a copy of its arguments and notify the owner
		715	coro of the callback.
		716
		717	See the next function.
		718
		719	=item @args = Coro::rouse_wait [$cb]
		720
		721	Wait for the specified rouse callback (or the last one that was created in
		722	this coro).
		723
		724	As soon as the callback is invoked (or when the callback was invoked
		725	before C<rouse_wait>), it will return the arguments originally passed to
		726	the rouse callback.
		727
		728	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		729
		730	=back
		731
		732	=cut
		733
		734	1;
		735
		736	=head1 HOW TO WAIT FOR A CALLBACK
		737
		738	It is very common for a coro to wait for some callback to be
		739	called. This occurs naturally when you use coro in an otherwise
		740	event-based program, or when you use event-based libraries.
		741
		742	These typically register a callback for some event, and call that callback
		743	when the event occured. In a coro, however, you typically want to
		744	just wait for the event, simplyifying things.
		745
		746	For example C<< AnyEvent->child >> registers a callback to be called when
		747	a specific child has exited:
		748
		749	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		750
		751	But from within a coro, you often just want to write this:
		752
		753	my $status = wait_for_child $pid;
		754
		755	Coro offers two functions specifically designed to make this easy,
		756	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		757
		758	The first function, C<rouse_cb>, generates and returns a callback that,
		759	when invoked, will save its arguments and notify the coro that
		760	created the callback.
		761
		762	The second function, C<rouse_wait>, waits for the callback to be called
		763	(by calling C<schedule> to go to sleep) and returns the arguments
		764	originally passed to the callback.
		765
		766	Using these functions, it becomes easy to write the C<wait_for_child>
		767	function mentioned above:
		768
		769	sub wait_for_child($) {
		770	my ($pid) = @_;
		771
		772	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		773
		774	my ($rpid, $rstatus) = Coro::rouse_wait;
		775	$rstatus
		776	}
		777
		778	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		779	you can roll your own, using C<schedule>:
		780
		781	sub wait_for_child($) {
		782	my ($pid) = @_;
		783
		784	# store the current coro in $current,
		785	# and provide result variables for the closure passed to ->child
		786	my $current = $Coro::current;
		787	my ($done, $rstatus);
		788
		789	# pass a closure to ->child
		790	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		791	$rstatus = $_[1]; # remember rstatus
		792	$done = 1; # mark $rstatus as valud
		793	});
		794
		795	# wait until the closure has been called
		796	schedule while !$done;
		797
		798	$rstatus
		799	}
		800
		801
		802	=head1 BUGS/LIMITATIONS
106		803
107	=over 4	804	=over 4
108		805
109	=item async { ... };	806	=item fork with pthread backend
110		807
111	Create a new asynchronous process and return it's process object	808	When Coro is compiled using the pthread backend (which isn't recommended
112	(usually unused). When the sub returns the new process is automatically	809	but required on many BSDs as their libcs are completely broken), then
113	terminated.	810	coro will not survive a fork. There is no known workaround except to
		811	fix your libc and use a saner backend.
114		812
115	=cut	813	=item perl process emulation ("threads")
116		814
117	sub async(&) {	815	This module is not perl-pseudo-thread-safe. You should only ever use this
118	my $pid = new Coro $_[0];	816	module from the first thread (this requirement might be removed in the
119	$pid->ready;	817	future to allow per-thread schedulers, but Coro::State does not yet allow
120	$pid;	818	this). I recommend disabling thread support and using processes, as having
121	}	819	the windows process emulation enabled under unix roughly halves perl
		820	performance, even when not used.
122		821
123	=item schedule	822	=item coro switching is not signal safe
124		823
125	Calls the scheduler. Please note that the current process will not be put	824	You must not switch to another coro from within a signal handler
126	into the ready queue, so calling this function usually means you will	825	(only relevant with %SIG - most event libraries provide safe signals).
127	never be called again.
128		826
129	=cut	827	That means you I<MUST NOT> call any function that might "block" the
130		828	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
131	my $prev;	829	anything that calls those. Everything else, including calling C<ready>,
132		830	works.
133	sub schedule {
134	# should be done using priorities :(
135	($prev, $current) = ($current, shift @ready \|\| $idle);
136	Coro::State::transfer($prev, $current);
137	}
138
139	=item yield
140
141	Yield to other processes. This function puts the current process into the
142	ready queue and calls C<schedule>.
143
144	=cut
145
146	sub yield {
147	$current->ready;
148	&schedule;
149	}
150
151	=item terminate
152
153	Terminates the current process.
154
155	=cut
156
157	sub terminate {
158	&schedule;
159	}
160		831
161	=back	832	=back
162		833
163	# dynamic methods
164
165	=head2 PROCESS METHODS
166
167	These are the methods you can call on process objects.
168
169	=over 4
170
171	=item new Coro \⊂
172
173	Create a new process and return it. When the sub returns the process
174	automatically terminates. To start the process you must first put it into
175	the ready queue by calling the ready method.
176
177	=cut
178
179	sub new {
180	my $class = shift;
181	my $proc = $_[0];
182	bless {
183	_coro_state => new Coro::State ($proc ? sub { &$proc; &terminate } : $proc),
184	}, $class;
185	}
186
187	=item $process->ready
188
189	Put the current process into the ready queue.
190
191	=cut
192
193	sub ready {
194	push @ready, $_[0];
195	}
196
197	=back
198
199	=cut
200
201	1;
202		834
203	=head1 SEE ALSO	835	=head1 SEE ALSO
204		836
205	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,	837	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
206	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>.	838
		839	Debugging: L<Coro::Debug>.
		840
		841	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
		842
		843	Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
		844	L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		845
		846	I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
		847
		848	Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
		849	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
		850	L<Coro::Select>.
		851
		852	XS API: L<Coro::MakeMaker>.
		853
		854	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
207		855
208	=head1 AUTHOR	856	=head1 AUTHOR
209		857
210	Marc Lehmann <pcg@goof.com>	858	Marc Lehmann <schmorp@schmorp.de>
211	http://www.goof.com/pcg/marc/	859	http://home.schmorp.de/
212		860
213	=cut	861	=cut
214		862

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Comparing Coro/Coro.pm (file contents): Revision 1.11 by root, Sun Jul 15 03:24:18 2001 UTC vs. Revision 1.250 by root, Wed Dec 17 04:57:07 2008 UTC

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Revision 1.250 by root, Wed Dec 17 04:57:07 2008 UTC