[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 1.291 by root, Fri Apr 29 15:43:26 2011 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 (see section of same name for
		46	more details) ported to UNIX, and as such act as processes), Coro
		47	provides a full shared address space, which makes communication between
		48	threads very easy. And coro threads are fast, too: disabling the Windows
		49	process emulation code in your perl and using Coro can easily result in
		50	a two to four times speed increase for your programs. A parallel matrix
		51	multiplication benchmark (very communication-intensive) runs over 300
		52	times faster on a single core than perls pseudo-threads on a quad core
		53	using all four cores.
		54
		55	Coro achieves that by supporting multiple running interpreters that share
		56	data, which is especially useful to code pseudo-parallel processes and
		57	for event-based programming, such as multiple HTTP-GET requests running
		58	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
		59	into an event-based environment.
		60
		61	In this module, a thread is defined as "callchain + lexical variables +
		62	some package variables + C stack), that is, a thread has its own callchain,
		63	its own set of lexicals and its own set of perls most important global
		64	variables (see L<Coro::State> for more configuration and background info).
		65
		66	See also the C<SEE ALSO> section at the end of this document - the Coro
		67	module family is quite large.
		68
		69	=head1 CORO THREAD LIFE CYCLE
		70
		71	During the long and exciting (or not) life of a coro thread, it goes
		72	through a number of states:
		73
		74	=over 4
		75
		76	=item 1. Creation
		77
		78	The first thing in the life of a coro thread is it's creation -
		79	obviously. The typical way to create a thread is to call the C<async
		80	BLOCK> function:
		81
		82	async {
		83	# thread code goes here
		84	};
		85
		86	You can also pass arguments, which are put in C<@_>:
		87
		88	async {
		89	print $_[1]; # prints 2
		90	} 1, 2, 3;
		91
		92	This creates a new coro thread and puts it into the ready queue, meaning
		93	it will run as soon as the CPU is free for it.
		94
		95	C<async> will return a coro object - you can store this for future
		96	reference or ignore it, the thread itself will keep a reference to it's
		97	thread object - threads are alive on their own.
		98
		99	Another way to create a thread is to call the C<new> constructor with a
		100	code-reference:
		101
		102	new Coro sub {
		103	# thread code goes here
		104	}, @optional_arguments;
		105
		106	This is quite similar to calling C<async>, but the important difference is
		107	that the new thread is not put into the ready queue, so the thread will
		108	not run until somebody puts it there. C<async> is, therefore, identical to
		109	this sequence:
		110
		111	my $coro = new Coro sub {
		112	# thread code goes here
		113	};
		114	$coro->ready;
		115	return $coro;
		116
		117	=item 2. Startup
		118
		119	When a new coro thread is created, only a copy of the code reference
		120	and the arguments are stored, no extra memory for stacks and so on is
		121	allocated, keeping the coro thread in a low-memory state.
		122
		123	Only when it actually starts executing will all the resources be finally
		124	allocated.
		125
		126	The optional arguments specified at coro creation are available in C<@_>,
		127	similar to function calls.
		128
		129	=item 3. Running / Blocking
		130
		131	A lot can happen after the coro thread has started running. Quite usually,
		132	it will not run to the end in one go (because you could use a function
		133	instead), but it will give up the CPU regularly because it waits for
		134	external events.
		135
		136	As long as a coro thread runs, it's coro object is available in the global
		137	variable C<$Coro::current>.
		138
		139	The low-level way to give up the CPU is to call the scheduler, which
		140	selects a new coro thread to run:
		141
		142	Coro::schedule;
		143
		144	Since running threads are not in the ready queue, calling the scheduler
		145	without doing anything else will block the coro thread forever - you need
		146	to arrange either for the coro to put woken up (readied) by some other
		147	event or some other thread, or you can put it into the ready queue before
		148	scheduling:
		149
		150	# this is exactly what Coro::cede does
		151	$Coro::current->ready;
		152	Coro::schedule;
		153
		154	All the higher-level synchronisation methods (Coro::Semaphore,
		155	Coro::rouse_*...) are actually implemented via C<< ->ready >> and C<<
		156	Coro::schedule >>.
		157
		158	While the coro thread is running it also might get assigned a C-level
		159	thread, or the C-level thread might be unassigned from it, as the Coro
		160	runtime wishes. A C-level thread needs to be assigned when your perl
		161	thread calls into some C-level function and that function in turn calls
		162	perl and perl then wants to switch coroutines. This happens most often
		163	when you run an event loop and block in the callback, or when perl
		164	itself calls some function such as C<AUTOLOAD> or methods via the C<tie>
		165	mechanism.
		166
		167	=item 4. Termination
		168
		169	Many threads actually terminate after some time. There are a number of
		170	ways to terminate a coro thread, the simplest is returning from the
		171	top-level code reference:
		172
		173	async {
		174	# after returning from here, the coro thread is terminated
		175	};
		176
		177	async {
		178	return if 0.5 < rand; # terminate a little earlier, maybe
		179	print "got a chance to print this\n";
		180	# or here
		181	};
		182
		183	Any values returned from the coroutine can be recovered using C<< ->join
		184	>>:
		185
		186	my $coro = async {
		187	"hello, world\n" # return a string
		188	};
		189
		190	my $hello_world = $coro->join;
		191
		192	print $hello_world;
		193
		194	Another way to terminate is to call C<< Coro::terminate >>, which at any
		195	subroutine call nesting level:
		196
		197	async {
		198	Coro::terminate "return value 1", "return value 2";
		199	};
		200
		201	And yet another way is to C<< ->cancel >> the coro thread from another
		202	thread:
		203
		204	my $coro = async {
		205	exit 1;
		206	};
		207
		208	$coro->cancel; # an also accept values for ->join to retrieve
		209
		210	Cancellation I<can> be dangerous - it's a bit like calling C<exit> without
		211	actually exiting, and might leave C libraries and XS modules in a weird
		212	state. Unlike other thread implementations, however, Coro is exceptionally
		213	safe with regards to cancellation, as perl will always be in a consistent
		214	state.
		215
		216	So, cancelling a thread that runs in an XS event loop might not be the
		217	best idea, but any other combination that deals with perl only (cancelling
		218	when a thread is in a C<tie> method or an C<AUTOLOAD> for example) is
		219	safe.
		220
		221	=item 5. Cleanup
		222
		223	Threads will allocate various resources. Most but not all will be returned
		224	when a thread terminates, during clean-up.
		225
		226	Cleanup is quite similar to throwing an uncaught exception: perl will
		227	work it's way up through all subroutine calls and blocks. On it's way, it
		228	will release all C<my> variables, undo all C<local>'s and free any other
		229	resources truly local to the thread.
		230
		231	So, a common way to free resources is to keep them referenced only by my
		232	variables:
		233
		234	async {
		235	my $big_cache = new Cache ...;
		236	};
		237
		238	If there are no other references, then the C<$big_cache> object will be
		239	freed when the thread terminates, regardless of how it does so.
		240
		241	What it does C<NOT> do is unlock any Coro::Semaphores or similar
		242	resources, but that's where the C<guard> methods come in handy:
		243
		244	my $sem = new Coro::Semaphore;
		245
		246	async {
		247	my $lock_guard = $sem->guard;
		248	# if we reutrn, or die or get cancelled, here,
		249	# then the semaphore will be "up"ed.
		250	};
		251
		252	The C<Guard::guard> function comes in handy for any custom cleanup you
		253	might want to do:
		254
		255	async {
		256	my $window = new Gtk2::Window "toplevel";
		257	# The window will not be cleaned up automatically, even when $window
		258	# gets freed, so use a guard to ensure it's destruction
		259	# in case of an error:
		260	my $window_guard = Guard::guard { $window->destroy };
		261
		262	# we are safe here
		263	};
		264
		265	Last not least, C<local> can often be handy, too, e.g. when temporarily
		266	replacing the coro thread description:
		267
		268	sub myfunction {
		269	local $Coro::current->{desc} = "inside myfunction(@_)";
		270
		271	# if we return or die here, the description will be restored
		272	}
		273
		274	=item 6. Viva La Zombie Muerte
		275
		276	Even after a thread has terminated and cleaned up it's resources, the coro
		277	object still is there and stores the return values of the thread. Only in
		278	this state will the coro object be "reference counted" in the normal perl
		279	sense: the thread code keeps a reference to it when it is active, but not
		280	after it has terminated.
		281
		282	The means the coro object gets freed automatically when the thread has
		283	terminated and cleaned up and there arenot other references.
		284
		285	If there are, the coro object will stay around, and you can call C<<
		286	->join >> as many times as you wish to retrieve the result values:
		287
		288	async {
		289	print "hi\n";
		290	1
		291	};
		292
		293	# run the async above, and free everything before returning
		294	# from Coro::cede:
		295	Coro::cede;
		296
		297	{
		298	my $coro = async {
		299	print "hi\n";
		300	1
		301	};
		302
		303	# run the async above, and clean up, but do not free the coro
		304	# object:
		305	Coro::cede;
		306
		307	# optionally retrieve the result values
		308	my @results = $coro->join;
		309
		310	# now $coro goes out of scope, and presumably gets freed
		311	};
		312
		313	=back
		314
23	=cut	315	=cut
24		316
25	package Coro;	317	package Coro;
26		318
		319	use common::sense;
		320
		321	use Carp ();
		322
		323	use Guard ();
		324
27	use Coro::State;	325	use Coro::State;
28		326
29	use base Exporter;	327	use base qw(Coro::State Exporter);
30		328
31	$VERSION = 0.04;	329	our $idle; # idle handler
		330	our $main; # main coro
		331	our $current; # current coro
32		332
33	@EXPORT = qw(async yield schedule);	333	our $VERSION = 5.372;
34	@EXPORT_OK = qw($current);
35		334
36	{	335	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
37	use subs 'async';	336	our %EXPORT_TAGS = (
		337	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		338	);
		339	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
38		340
39	my @async;	341	=head1 GLOBAL VARIABLES
40		342
41	# this way of handling attributes simply is NOT scalable ;()	343	=over 4
42	sub import {	344
43	Coro->export_to_level(1, @_);	345	=item $Coro::main
44	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};	346
45	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {	347	This variable stores the Coro object that represents the main
46	my ($package, $ref) = (shift, shift);	348	program. While you cna C<ready> it and do most other things you can do to
47	my @attrs;	349	coro, it is mainly useful to compare again C<$Coro::current>, to see
48	for (@_) {	350	whether you are running in the main program or not.
49	if ($_ eq "Coro") {	351
50	push @async, $ref;	352	=cut
51	} else {	353
52	push @attrs, @_;	354	# $main is now being initialised by Coro::State
53	}	355
54	}	356	=item $Coro::current
55	return $old ? $old->($package, $name, @attrs) : @attrs;	357
		358	The Coro object representing the current coro (the last
		359	coro that the Coro scheduler switched to). The initial value is
		360	C<$Coro::main> (of course).
		361
		362	This variable is B<strictly> I<read-only>. You can take copies of the
		363	value stored in it and use it as any other Coro object, but you must
		364	not otherwise modify the variable itself.
		365
		366	=cut
		367
		368	sub current() { $current } # [DEPRECATED]
		369
		370	=item $Coro::idle
		371
		372	This variable is mainly useful to integrate Coro into event loops. It is
		373	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
		374	pretty low-level functionality.
		375
		376	This variable stores a Coro object that is put into the ready queue when
		377	there are no other ready threads (without invoking any ready hooks).
		378
		379	The default implementation dies with "FATAL: deadlock detected.", followed
		380	by a thread listing, because the program has no other way to continue.
		381
		382	This hook is overwritten by modules such as C<Coro::EV> and
		383	C<Coro::AnyEvent> to wait on an external event that hopefully wakes up a
		384	coro so the scheduler can run it.
		385
		386	See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
		387
		388	=cut
		389
		390	# \|\|= because other modules could have provided their own by now
		391	$idle \|\|= new Coro sub {
		392	require Coro::Debug;
		393	die "FATAL: deadlock detected.\n"
		394	. Coro::Debug::ps_listing ();
		395	};
		396
		397	# this coro is necessary because a coro
		398	# cannot destroy itself.
		399	our @destroy;
		400	our $manager;
		401
		402	$manager = new Coro sub {
		403	while () {
		404	_destroy shift @destroy
		405	while @destroy;
		406
		407	&schedule;
		408	}
		409	};
		410	$manager->{desc} = "[coro manager]";
		411	$manager->prio (PRIO_MAX);
		412
		413	=back
		414
		415	=head1 SIMPLE CORO CREATION
		416
		417	=over 4
		418
		419	=item async { ... } [@args...]
		420
		421	Create a new coro and return its Coro object (usually
		422	unused). The coro will be put into the ready queue, so
		423	it will start running automatically on the next scheduler run.
		424
		425	The first argument is a codeblock/closure that should be executed in the
		426	coro. When it returns argument returns the coro is automatically
		427	terminated.
		428
		429	The remaining arguments are passed as arguments to the closure.
		430
		431	See the C<Coro::State::new> constructor for info about the coro
		432	environment in which coro are executed.
		433
		434	Calling C<exit> in a coro will do the same as calling exit outside
		435	the coro. Likewise, when the coro dies, the program will exit,
		436	just as it would in the main program.
		437
		438	If you do not want that, you can provide a default C<die> handler, or
		439	simply avoid dieing (by use of C<eval>).
		440
		441	Example: Create a new coro that just prints its arguments.
		442
		443	async {
		444	print "@_\n";
		445	} 1,2,3,4;
		446
		447	=item async_pool { ... } [@args...]
		448
		449	Similar to C<async>, but uses a coro pool, so you should not call
		450	terminate or join on it (although you are allowed to), and you get a
		451	coro that might have executed other code already (which can be good
		452	or bad :).
		453
		454	On the plus side, this function is about twice as fast as creating (and
		455	destroying) a completely new coro, so if you need a lot of generic
		456	coros in quick successsion, use C<async_pool>, not C<async>.
		457
		458	The code block is executed in an C<eval> context and a warning will be
		459	issued in case of an exception instead of terminating the program, as
		460	C<async> does. As the coro is being reused, stuff like C<on_destroy>
		461	will not work in the expected way, unless you call terminate or cancel,
		462	which somehow defeats the purpose of pooling (but is fine in the
		463	exceptional case).
		464
		465	The priority will be reset to C<0> after each run, tracing will be
		466	disabled, the description will be reset and the default output filehandle
		467	gets restored, so you can change all these. Otherwise the coro will
		468	be re-used "as-is": most notably if you change other per-coro global
		469	stuff such as C<$/> you I<must needs> revert that change, which is most
		470	simply done by using local as in: C<< local $/ >>.
		471
		472	The idle pool size is limited to C<8> idle coros (this can be
		473	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
		474	coros as required.
		475
		476	If you are concerned about pooled coros growing a lot because a
		477	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		478	{ terminate }> once per second or so to slowly replenish the pool. In
		479	addition to that, when the stacks used by a handler grows larger than 32kb
		480	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
		481
		482	=cut
		483
		484	our $POOL_SIZE = 8;
		485	our $POOL_RSS = 32 * 1024;
		486	our @async_pool;
		487
		488	sub pool_handler {
		489	while () {
		490	eval {
		491	&{&_pool_handler} while 1;
56	};	492	};
57	}
58		493
59	sub INIT {	494	warn $@ if $@;
60	async pop @async while @async;
61	}	495	}
62	}	496	}
63		497
64	=item $main	498	=back
65		499
66	This coroutine represents the main program.	500	=head1 STATIC METHODS
67		501
68	=cut	502	Static methods are actually functions that implicitly operate on the
		503	current coro.
69		504
70	our $main = new Coro;	505	=over 4
71		506
72	=item $current	507	=item schedule
73		508
74	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).	509	Calls the scheduler. The scheduler will find the next coro that is
		510	to be run from the ready queue and switches to it. The next coro
		511	to be run is simply the one with the highest priority that is longest
		512	in its ready queue. If there is no coro ready, it will call the
		513	C<$Coro::idle> hook.
75		514
76	=cut	515	Please note that the current coro will I<not> be put into the ready
		516	queue, so calling this function usually means you will never be called
		517	again unless something else (e.g. an event handler) calls C<< ->ready >>,
		518	thus waking you up.
77		519
78	# maybe some other module used Coro::Specific before...	520	This makes C<schedule> I<the> generic method to use to block the current
79	if ($current) {	521	coro and wait for events: first you remember the current coro in
80	$main->{specific} = $current->{specific};	522	a variable, then arrange for some callback of yours to call C<< ->ready
		523	>> on that once some event happens, and last you call C<schedule> to put
		524	yourself to sleep. Note that a lot of things can wake your coro up,
		525	so you need to check whether the event indeed happened, e.g. by storing the
		526	status in a variable.
		527
		528	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
		529
		530	=item cede
		531
		532	"Cede" to other coros. This function puts the current coro into
		533	the ready queue and calls C<schedule>, which has the effect of giving
		534	up the current "timeslice" to other coros of the same or higher
		535	priority. Once your coro gets its turn again it will automatically be
		536	resumed.
		537
		538	This function is often called C<yield> in other languages.
		539
		540	=item Coro::cede_notself
		541
		542	Works like cede, but is not exported by default and will cede to I<any>
		543	coro, regardless of priority. This is useful sometimes to ensure
		544	progress is made.
		545
		546	=item terminate [arg...]
		547
		548	Terminates the current coro with the given status values (see
		549	L<cancel>). The values will not be copied, but referenced directly.
		550
		551	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
		552
		553	These function install enter and leave winders in the current scope. The
		554	enter block will be executed when on_enter is called and whenever the
		555	current coro is re-entered by the scheduler, while the leave block is
		556	executed whenever the current coro is blocked by the scheduler, and
		557	also when the containing scope is exited (by whatever means, be it exit,
		558	die, last etc.).
		559
		560	I<Neither invoking the scheduler, nor exceptions, are allowed within those
		561	BLOCKs>. That means: do not even think about calling C<die> without an
		562	eval, and do not even think of entering the scheduler in any way.
		563
		564	Since both BLOCKs are tied to the current scope, they will automatically
		565	be removed when the current scope exits.
		566
		567	These functions implement the same concept as C<dynamic-wind> in scheme
		568	does, and are useful when you want to localise some resource to a specific
		569	coro.
		570
		571	They slow down thread switching considerably for coros that use them
		572	(about 40% for a BLOCK with a single assignment, so thread switching is
		573	still reasonably fast if the handlers are fast).
		574
		575	These functions are best understood by an example: The following function
		576	will change the current timezone to "Antarctica/South_Pole", which
		577	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
		578	which remember/change the current timezone and restore the previous
		579	value, respectively, the timezone is only changed for the coro that
		580	installed those handlers.
		581
		582	use POSIX qw(tzset);
		583
		584	async {
		585	my $old_tz; # store outside TZ value here
		586
		587	Coro::on_enter {
		588	$old_tz = $ENV{TZ}; # remember the old value
		589
		590	$ENV{TZ} = "Antarctica/South_Pole";
		591	tzset; # enable new value
		592	};
		593
		594	Coro::on_leave {
		595	$ENV{TZ} = $old_tz;
		596	tzset; # restore old value
		597	};
		598
		599	# at this place, the timezone is Antarctica/South_Pole,
		600	# without disturbing the TZ of any other coro.
		601	};
		602
		603	This can be used to localise about any resource (locale, uid, current
		604	working directory etc.) to a block, despite the existance of other
		605	coros.
		606
		607	Another interesting example implements time-sliced multitasking using
		608	interval timers (this could obviously be optimised, but does the job):
		609
		610	# "timeslice" the given block
		611	sub timeslice(&) {
		612	use Time::HiRes ();
		613
		614	Coro::on_enter {
		615	# on entering the thread, we set an VTALRM handler to cede
		616	$SIG{VTALRM} = sub { cede };
		617	# and then start the interval timer
		618	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
		619	};
		620	Coro::on_leave {
		621	# on leaving the thread, we stop the interval timer again
		622	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
		623	};
		624
		625	&{+shift};
		626	}
		627
		628	# use like this:
		629	timeslice {
		630	# The following is an endless loop that would normally
		631	# monopolise the process. Since it runs in a timesliced
		632	# environment, it will regularly cede to other threads.
		633	while () { }
		634	};
		635
		636
		637	=item killall
		638
		639	Kills/terminates/cancels all coros except the currently running one.
		640
		641	Note that while this will try to free some of the main interpreter
		642	resources if the calling coro isn't the main coro, but one
		643	cannot free all of them, so if a coro that is not the main coro
		644	calls this function, there will be some one-time resource leak.
		645
		646	=cut
		647
		648	sub killall {
		649	for (Coro::State::list) {
		650	$_->cancel
		651	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		652	}
81	}	653	}
82		654
83	our $current = $main;	655	=back
84		656
85	=item $idle	657	=head1 CORO OBJECT METHODS
86		658
87	The coroutine to switch to when no other coroutine is running. The default	659	These are the methods you can call on coro objects (or to create
88	implementation prints "FATAL: deadlock detected" and exits.	660	them).
89		661
90	=cut	662	=over 4
91		663
92	# should be done using priorities :(	664	=item new Coro \&sub [, @args...]
		665
		666	Create a new coro and return it. When the sub returns, the coro
		667	automatically terminates as if C<terminate> with the returned values were
		668	called. To make the coro run you must first put it into the ready
		669	queue by calling the ready method.
		670
		671	See C<async> and C<Coro::State::new> for additional info about the
		672	coro environment.
		673
		674	=cut
		675
		676	sub _coro_run {
		677	terminate &{+shift};
		678	}
		679
		680	=item $success = $coro->ready
		681
		682	Put the given coro into the end of its ready queue (there is one
		683	queue for each priority) and return true. If the coro is already in
		684	the ready queue, do nothing and return false.
		685
		686	This ensures that the scheduler will resume this coro automatically
		687	once all the coro of higher priority and all coro of the same
		688	priority that were put into the ready queue earlier have been resumed.
		689
		690	=item $coro->suspend
		691
		692	Suspends the specified coro. A suspended coro works just like any other
		693	coro, except that the scheduler will not select a suspended coro for
		694	execution.
		695
		696	Suspending a coro can be useful when you want to keep the coro from
		697	running, but you don't want to destroy it, or when you want to temporarily
		698	freeze a coro (e.g. for debugging) to resume it later.
		699
		700	A scenario for the former would be to suspend all (other) coros after a
		701	fork and keep them alive, so their destructors aren't called, but new
		702	coros can be created.
		703
		704	=item $coro->resume
		705
		706	If the specified coro was suspended, it will be resumed. Note that when
		707	the coro was in the ready queue when it was suspended, it might have been
		708	unreadied by the scheduler, so an activation might have been lost.
		709
		710	To avoid this, it is best to put a suspended coro into the ready queue
		711	unconditionally, as every synchronisation mechanism must protect itself
		712	against spurious wakeups, and the one in the Coro family certainly do
		713	that.
		714
		715	=item $is_ready = $coro->is_ready
		716
		717	Returns true iff the Coro object is in the ready queue. Unless the Coro
		718	object gets destroyed, it will eventually be scheduled by the scheduler.
		719
		720	=item $is_running = $coro->is_running
		721
		722	Returns true iff the Coro object is currently running. Only one Coro object
		723	can ever be in the running state (but it currently is possible to have
		724	multiple running Coro::States).
		725
		726	=item $is_suspended = $coro->is_suspended
		727
		728	Returns true iff this Coro object has been suspended. Suspended Coros will
		729	not ever be scheduled.
		730
		731	=item $coro->cancel (arg...)
		732
		733	Terminates the given Coro object and makes it return the given arguments as
		734	status (default: an empty list). Never returns if the Coro is the
		735	current Coro.
		736
		737	The arguments are not copied, but instead will be referenced directly
		738	(e.g. if you pass C<$var> and after the call change that variable, then
		739	you might change the return values passed to e.g. C<join>, so don't do
		740	that).
		741
		742	The resources of the Coro are usually freed (or destructed) before this
		743	call returns, but this can be delayed for an indefinite amount of time, as
		744	in some cases the manager thread has to run first to actually destruct the
		745	Coro object.
		746
		747	=item $coro->schedule_to
		748
		749	Puts the current coro to sleep (like C<Coro::schedule>), but instead
		750	of continuing with the next coro from the ready queue, always switch to
		751	the given coro object (regardless of priority etc.). The readyness
		752	state of that coro isn't changed.
		753
		754	This is an advanced method for special cases - I'd love to hear about any
		755	uses for this one.
		756
		757	=item $coro->cede_to
		758
		759	Like C<schedule_to>, but puts the current coro into the ready
		760	queue. This has the effect of temporarily switching to the given
		761	coro, and continuing some time later.
		762
		763	This is an advanced method for special cases - I'd love to hear about any
		764	uses for this one.
		765
		766	=item $coro->throw ([$scalar])
		767
		768	If C<$throw> is specified and defined, it will be thrown as an exception
		769	inside the coro at the next convenient point in time. Otherwise
		770	clears the exception object.
		771
		772	Coro will check for the exception each time a schedule-like-function
		773	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		774	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		775	detect this case and return early in case an exception is pending.
		776
		777	The exception object will be thrown "as is" with the specified scalar in
		778	C<$@>, i.e. if it is a string, no line number or newline will be appended
		779	(unlike with C<die>).
		780
		781	This can be used as a softer means than C<cancel> to ask a coro to
		782	end itself, although there is no guarantee that the exception will lead to
		783	termination, and if the exception isn't caught it might well end the whole
		784	program.
		785
		786	You might also think of C<throw> as being the moral equivalent of
		787	C<kill>ing a coro with a signal (in this case, a scalar).
		788
		789	=item $coro->join
		790
		791	Wait until the coro terminates and return any values given to the
		792	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		793	from multiple coro, and all will be resumed and given the status
		794	return once the C<$coro> terminates.
		795
		796	=cut
		797
		798	sub join {
		799	my $self = shift;
		800
		801	unless ($self->{_status}) {
		802	my $current = $current;
		803
		804	push @{$self->{_on_destroy}}, sub {
		805	$current->ready;
		806	undef $current;
		807	};
		808
		809	&schedule while $current;
		810	}
		811
		812	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		813	}
		814
		815	=item $coro->on_destroy (\&cb)
		816
		817	Registers a callback that is called when this coro thread gets destroyed,
		818	but before it is joined. The callback gets passed the terminate arguments,
		819	if any, and I<must not> die, under any circumstances.
		820
		821	There can be any number of C<on_destroy> callbacks per coro.
		822
		823	=cut
		824
		825	sub on_destroy {
		826	my ($self, $cb) = @_;
		827
		828	push @{ $self->{_on_destroy} }, $cb;
		829	}
		830
		831	=item $oldprio = $coro->prio ($newprio)
		832
		833	Sets (or gets, if the argument is missing) the priority of the
		834	coro thread. Higher priority coro get run before lower priority
		835	coros. Priorities are small signed integers (currently -4 .. +3),
		836	that you can refer to using PRIO_xxx constants (use the import tag :prio
		837	to get then):
		838
		839	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		840	3 > 1 > 0 > -1 > -3 > -4
		841
		842	# set priority to HIGH
		843	current->prio (PRIO_HIGH);
		844
		845	The idle coro thread ($Coro::idle) always has a lower priority than any
		846	existing coro.
		847
		848	Changing the priority of the current coro will take effect immediately,
		849	but changing the priority of a coro in the ready queue (but not running)
		850	will only take effect after the next schedule (of that coro). This is a
		851	bug that will be fixed in some future version.
		852
		853	=item $newprio = $coro->nice ($change)
		854
		855	Similar to C<prio>, but subtract the given value from the priority (i.e.
		856	higher values mean lower priority, just as in UNIX's nice command).
		857
		858	=item $olddesc = $coro->desc ($newdesc)
		859
		860	Sets (or gets in case the argument is missing) the description for this
		861	coro thread. This is just a free-form string you can associate with a
		862	coro.
		863
		864	This method simply sets the C<< $coro->{desc} >> member to the given
		865	string. You can modify this member directly if you wish, and in fact, this
		866	is often preferred to indicate major processing states that cna then be
		867	seen for example in a L<Coro::Debug> session:
		868
		869	sub my_long_function {
		870	local $Coro::current->{desc} = "now in my_long_function";
		871	...
		872	$Coro::current->{desc} = "my_long_function: phase 1";
		873	...
		874	$Coro::current->{desc} = "my_long_function: phase 2";
		875	...
		876	}
		877
		878	=cut
		879
		880	sub desc {
		881	my $old = $_[0]{desc};
		882	$_[0]{desc} = $_[1] if @_ > 1;
		883	$old;
		884	}
		885
		886	sub transfer {
		887	require Carp;
		888	Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
		889	}
		890
		891	=back
		892
		893	=head1 GLOBAL FUNCTIONS
		894
		895	=over 4
		896
		897	=item Coro::nready
		898
		899	Returns the number of coro that are currently in the ready state,
		900	i.e. that can be switched to by calling C<schedule> directory or
		901	indirectly. The value C<0> means that the only runnable coro is the
		902	currently running one, so C<cede> would have no effect, and C<schedule>
		903	would cause a deadlock unless there is an idle handler that wakes up some
		904	coro.
		905
		906	=item my $guard = Coro::guard { ... }
		907
		908	This function still exists, but is deprecated. Please use the
		909	C<Guard::guard> function instead.
		910
		911	=cut
		912
		913	BEGIN { *guard = \&Guard::guard }
		914
		915	=item unblock_sub { ... }
		916
		917	This utility function takes a BLOCK or code reference and "unblocks" it,
		918	returning a new coderef. Unblocking means that calling the new coderef
		919	will return immediately without blocking, returning nothing, while the
		920	original code ref will be called (with parameters) from within another
		921	coro.
		922
		923	The reason this function exists is that many event libraries (such as
		924	the venerable L<Event\|Event> module) are not thread-safe (a weaker form
		925	of reentrancy). This means you must not block within event callbacks,
		926	otherwise you might suffer from crashes or worse. The only event library
		927	currently known that is safe to use without C<unblock_sub> is L<EV> (but
		928	you might still run into deadlocks if all event loops are blocked).
		929
		930	Coro will try to catch you when you block in the event loop
		931	("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and
		932	only works when you do not run your own event loop.
		933
		934	This function allows your callbacks to block by executing them in another
		935	coro where it is safe to block. One example where blocking is handy
		936	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		937	disk, for example.
		938
		939	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		940	creating event callbacks that want to block.
		941
		942	If your handler does not plan to block (e.g. simply sends a message to
		943	another coro, or puts some other coro into the ready queue), there is
		944	no reason to use C<unblock_sub>.
		945
		946	Note that you also need to use C<unblock_sub> for any other callbacks that
		947	are indirectly executed by any C-based event loop. For example, when you
		948	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		949	provides callbacks that are the result of some event callback, then you
		950	must not block either, or use C<unblock_sub>.
		951
		952	=cut
		953
		954	our @unblock_queue;
		955
		956	# we create a special coro because we want to cede,
		957	# to reduce pressure on the coro pool (because most callbacks
		958	# return immediately and can be reused) and because we cannot cede
		959	# inside an event callback.
93	our $idle = new Coro sub {	960	our $unblock_scheduler = new Coro sub {
94	print STDERR "FATAL: deadlock detected\n";	961	while () {
95	exit(51);	962	while (my $cb = pop @unblock_queue) {
		963	&async_pool (@$cb);
		964
		965	# for short-lived callbacks, this reduces pressure on the coro pool
		966	# as the chance is very high that the async_poll coro will be back
		967	# in the idle state when cede returns
		968	cede;
		969	}
		970	schedule; # sleep well
		971	}
96	};	972	};
		973	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
97		974
98	# we really need priorities...	975	sub unblock_sub(&) {
99	my @ready = (); # the ready queue. hehe, rather broken ;)	976	my $cb = shift;
100		977
101	# static methods. not really.	978	sub {
		979	unshift @unblock_queue, [$cb, @_];
		980	$unblock_scheduler->ready;
		981	}
		982	}
102		983
103	=head2 STATIC METHODS	984	=item $cb = rouse_cb
104		985
105	Static methods are actually functions that operate on the current process only.	986	Create and return a "rouse callback". That's a code reference that,
		987	when called, will remember a copy of its arguments and notify the owner
		988	coro of the callback.
		989
		990	See the next function.
		991
		992	=item @args = rouse_wait [$cb]
		993
		994	Wait for the specified rouse callback (or the last one that was created in
		995	this coro).
		996
		997	As soon as the callback is invoked (or when the callback was invoked
		998	before C<rouse_wait>), it will return the arguments originally passed to
		999	the rouse callback. In scalar context, that means you get the I<last>
		1000	argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
		1001	statement at the end.
		1002
		1003	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		1004
		1005	=back
		1006
		1007	=cut
		1008
		1009	for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) {
		1010	my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"};
		1011
		1012	*{"Coro::$module\::new"} = sub {
		1013	require "Coro/$module.pm";
		1014
		1015	# some modules have their new predefined in State.xs, some don't
		1016	*{"Coro::$module\::new"} = $old
		1017	if $old;
		1018
		1019	goto &{"Coro::$module\::new"};
		1020	};
		1021	}
		1022
		1023	1;
		1024
		1025	=head1 HOW TO WAIT FOR A CALLBACK
		1026
		1027	It is very common for a coro to wait for some callback to be
		1028	called. This occurs naturally when you use coro in an otherwise
		1029	event-based program, or when you use event-based libraries.
		1030
		1031	These typically register a callback for some event, and call that callback
		1032	when the event occured. In a coro, however, you typically want to
		1033	just wait for the event, simplyifying things.
		1034
		1035	For example C<< AnyEvent->child >> registers a callback to be called when
		1036	a specific child has exited:
		1037
		1038	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		1039
		1040	But from within a coro, you often just want to write this:
		1041
		1042	my $status = wait_for_child $pid;
		1043
		1044	Coro offers two functions specifically designed to make this easy,
		1045	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		1046
		1047	The first function, C<rouse_cb>, generates and returns a callback that,
		1048	when invoked, will save its arguments and notify the coro that
		1049	created the callback.
		1050
		1051	The second function, C<rouse_wait>, waits for the callback to be called
		1052	(by calling C<schedule> to go to sleep) and returns the arguments
		1053	originally passed to the callback.
		1054
		1055	Using these functions, it becomes easy to write the C<wait_for_child>
		1056	function mentioned above:
		1057
		1058	sub wait_for_child($) {
		1059	my ($pid) = @_;
		1060
		1061	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		1062
		1063	my ($rpid, $rstatus) = Coro::rouse_wait;
		1064	$rstatus
		1065	}
		1066
		1067	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		1068	you can roll your own, using C<schedule>:
		1069
		1070	sub wait_for_child($) {
		1071	my ($pid) = @_;
		1072
		1073	# store the current coro in $current,
		1074	# and provide result variables for the closure passed to ->child
		1075	my $current = $Coro::current;
		1076	my ($done, $rstatus);
		1077
		1078	# pass a closure to ->child
		1079	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		1080	$rstatus = $_[1]; # remember rstatus
		1081	$done = 1; # mark $rstatus as valud
		1082	});
		1083
		1084	# wait until the closure has been called
		1085	schedule while !$done;
		1086
		1087	$rstatus
		1088	}
		1089
		1090
		1091	=head1 BUGS/LIMITATIONS
106		1092
107	=over 4	1093	=over 4
108		1094
109	=item async { ... };	1095	=item fork with pthread backend
110		1096
111	Create a new asynchronous process and return it's process object	1097	When Coro is compiled using the pthread backend (which isn't recommended
112	(usually unused). When the sub returns the new process is automatically	1098	but required on many BSDs as their libcs are completely broken), then
113	terminated.	1099	coro will not survive a fork. There is no known workaround except to
		1100	fix your libc and use a saner backend.
114		1101
115	=cut	1102	=item perl process emulation ("threads")
116		1103
117	sub async(&) {	1104	This module is not perl-pseudo-thread-safe. You should only ever use this
118	my $pid = new Coro $_[0];	1105	module from the first thread (this requirement might be removed in the
119	$pid->ready;	1106	future to allow per-thread schedulers, but Coro::State does not yet allow
120	$pid;	1107	this). I recommend disabling thread support and using processes, as having
121	}	1108	the windows process emulation enabled under unix roughly halves perl
		1109	performance, even when not used.
122		1110
123	=item schedule	1111	=item coro switching is not signal safe
124		1112
125	Calls the scheduler. Please note that the current process will not be put	1113	You must not switch to another coro from within a signal handler (only
126	into the ready queue, so calling this function usually means you will	1114	relevant with %SIG - most event libraries provide safe signals), I<unless>
127	never be called again.	1115	you are sure you are not interrupting a Coro function.
128		1116
129	=cut	1117	That means you I<MUST NOT> call any function that might "block" the
130		1118	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
131	my $prev;	1119	anything that calls those. Everything else, including calling C<ready>,
132		1120	works.
133	sub schedule {
134	# should be done using priorities :(
135	($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		1121
161	=back	1122	=back
162		1123
163	# dynamic methods
164		1124
165	=head2 PROCESS METHODS	1125	=head1 WINDOWS PROCESS EMULATION
166		1126
167	These are the methods you can call on process objects.	1127	A great many people seem to be confused about ithreads (for example, Chip
		1128	Salzenberg called me unintelligent, incapable, stupid and gullible,
		1129	while in the same mail making rather confused statements about perl
		1130	ithreads (for example, that memory or files would be shared), showing his
		1131	lack of understanding of this area - if it is hard to understand for Chip,
		1132	it is probably not obvious to everybody).
168		1133
169	=over 4	1134	What follows is an ultra-condensed version of my talk about threads in
		1135	scripting languages given on the perl workshop 2009:
170		1136
171	=item new Coro \⊂	1137	The so-called "ithreads" were originally implemented for two reasons:
		1138	first, to (badly) emulate unix processes on native win32 perls, and
		1139	secondly, to replace the older, real thread model ("5.005-threads").
172		1140
173	Create a new process and return it. When the sub returns the process	1141	It does that by using threads instead of OS processes. The difference
174	automatically terminates. To start the process you must first put it into	1142	between processes and threads is that threads share memory (and other
175	the ready queue by calling the ready method.	1143	state, such as files) between threads within a single process, while
		1144	processes do not share anything (at least not semantically). That
		1145	means that modifications done by one thread are seen by others, while
		1146	modifications by one process are not seen by other processes.
176		1147
177	=cut	1148	The "ithreads" work exactly like that: when creating a new ithreads
		1149	process, all state is copied (memory is copied physically, files and code
		1150	is copied logically). Afterwards, it isolates all modifications. On UNIX,
		1151	the same behaviour can be achieved by using operating system processes,
		1152	except that UNIX typically uses hardware built into the system to do this
		1153	efficiently, while the windows process emulation emulates this hardware in
		1154	software (rather efficiently, but of course it is still much slower than
		1155	dedicated hardware).
178		1156
179	sub new {	1157	As mentioned before, loading code, modifying code, modifying data
180	my $class = shift;	1158	structures and so on is only visible in the ithreads process doing the
181	my $proc = $_[0];	1159	modification, not in other ithread processes within the same OS process.
182	bless {
183	_coro_state => new Coro::State ($proc ? sub { &$proc; &terminate } : $proc),
184	}, $class;
185	}
186		1160
187	=item $process->ready	1161	This is why "ithreads" do not implement threads for perl at all, only
		1162	processes. What makes it so bad is that on non-windows platforms, you can
		1163	actually take advantage of custom hardware for this purpose (as evidenced
		1164	by the forks module, which gives you the (i-) threads API, just much
		1165	faster).
188		1166
189	Put the current process into the ready queue.	1167	Sharing data is in the i-threads model is done by transfering data
		1168	structures between threads using copying semantics, which is very slow -
		1169	shared data simply does not exist. Benchmarks using i-threads which are
		1170	communication-intensive show extremely bad behaviour with i-threads (in
		1171	fact, so bad that Coro, which cannot take direct advantage of multiple
		1172	CPUs, is often orders of magnitude faster because it shares data using
		1173	real threads, refer to my talk for details).
190		1174
191	=cut	1175	As summary, i-threads use threads to implement processes, while
		1176	the compatible forks module uses processes to emulate, uhm,
		1177	processes. I-threads slow down every perl program when enabled, and
		1178	outside of windows, serve no (or little) practical purpose, but
		1179	disadvantages every single-threaded Perl program.
192		1180
193	sub ready {	1181	This is the reason that I try to avoid the name "ithreads", as it is
194	push @ready, $_[0];	1182	misleading as it implies that it implements some kind of thread model for
195	}	1183	perl, and prefer the name "windows process emulation", which describes the
196		1184	actual use and behaviour of it much better.
197	=back
198
199	=cut
200
201	1;
202		1185
203	=head1 SEE ALSO	1186	=head1 SEE ALSO
204		1187
205	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,	1188	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
206	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>.	1189
		1190	Debugging: L<Coro::Debug>.
		1191
		1192	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
		1193
		1194	Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
		1195	L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		1196
		1197	I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
		1198
		1199	Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
		1200	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
		1201	L<Coro::Select>.
		1202
		1203	XS API: L<Coro::MakeMaker>.
		1204
		1205	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
207		1206
208	=head1 AUTHOR	1207	=head1 AUTHOR
209		1208
210	Marc Lehmann <pcg@goof.com>	1209	Marc Lehmann <schmorp@schmorp.de>
211	http://www.goof.com/pcg/marc/	1210	http://home.schmorp.de/
212		1211
213	=cut	1212	=cut
214		1213

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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 1.291 by root, Fri Apr 29 15:43:26 2011 UTC

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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 1.291 by root, Fri Apr 29 15:43:26 2011 UTC