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

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Revision 1.101 by root, Fri Dec 29 08:36:34 2006 UTC vs.
Revision 1.285 by root, Thu Feb 17 01:32:18 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 coroutine 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	cede;	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
23	This module collection manages coroutines. Coroutines are similar	31	For a tutorial-style introduction, please read the L<Coro::Intro>
24	to threads but don't run in parallel at the same time even on SMP	32	manpage. This manpage mainly contains reference information.
25	machines. The specific flavor of coroutine use din this module also
26	guarentees you that it will not switch between coroutines unless
27	necessary, at easily-identified points in your program, so locking and
28	parallel access are rarely an issue, making coroutine programming much
29	safer than threads programming.
30		33
31	(Perl, however, does not natively support real threads but instead does a	34	This module collection manages continuations in general, most often in
32	very slow and memory-intensive emulation of processes using threads. This	35	the form of cooperative threads (also called coros, or simply "coro"
33	is a performance win on Windows machines, and a loss everywhere else).	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.
34		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 more
		46	details) ported to unix, and as such act as processes), Coro provides
		47	a full shared address space, which makes communication between threads
		48	very easy. And Coro's 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 runs over 300 times faster on a single core than
		52	perl's pseudo-threads on a quad core using 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
35	In this module, coroutines are defined as "callchain + lexical variables +	60	In this module, a thread is defined as "callchain + lexical variables +
36	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,	61	some package variables + C stack), that is, a thread has its own callchain,
37	its own set of lexicals and its own set of perls most important global	62	its own set of lexicals and its own set of perls most important global
38	variables.	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.
39		67
40	=cut	68	=cut
41		69
42	package Coro;	70	package Coro;
43		71
44	use strict;	72	use common::sense;
45	no warnings "uninitialized";	73
		74	use Carp ();
		75
		76	use Guard ();
46		77
47	use Coro::State;	78	use Coro::State;
48		79
49	use base qw(Coro::State Exporter);	80	use base qw(Coro::State Exporter);
50		81
51	our $idle; # idle handler	82	our $idle; # idle handler
52	our $main; # main coroutine	83	our $main; # main coro
53	our $current; # current coroutine	84	our $current; # current coro
54		85
55	our $VERSION = '3.3';	86	our $VERSION = 5.26;
56		87
57	our @EXPORT = qw(async cede schedule terminate current unblock_sub);	88	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
58	our %EXPORT_TAGS = (	89	our %EXPORT_TAGS = (
59	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	90	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
60	);	91	);
61	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	92	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
62		93
63	{	94	=head1 GLOBAL VARIABLES
64	my @async;
65	my $init;
66
67	# this way of handling attributes simply is NOT scalable ;()
68	sub import {
69	no strict 'refs';
70
71	Coro->export_to_level (1, @_);
72
73	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
74	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
75	my ($package, $ref) = (shift, shift);
76	my @attrs;
77	for (@_) {
78	if ($_ eq "Coro") {
79	push @async, $ref;
80	unless ($init++) {
81	eval q{
82	sub INIT {
83	&async(pop @async) while @async;
84	}
85	};
86	}
87	} else {
88	push @attrs, $_;
89	}
90	}
91	return $old ? $old->($package, $ref, @attrs) : @attrs;
92	};
93	}
94
95	}
96		95
97	=over 4	96	=over 4
98		97
99	=item $main	98	=item $Coro::main
100		99
101	This coroutine represents the main program.	100	This variable stores the Coro object that represents the main
		101	program. While you cna C<ready> it and do most other things you can do to
		102	coro, it is mainly useful to compare again C<$Coro::current>, to see
		103	whether you are running in the main program or not.
102		104
103	=cut	105	=cut
104		106
105	$main = new Coro;	107	# $main is now being initialised by Coro::State
106		108
107	=item $current (or as function: current)	109	=item $Coro::current
108		110
109	The current coroutine (the last coroutine switched to). The initial value	111	The Coro object representing the current coro (the last
		112	coro that the Coro scheduler switched to). The initial value is
110	is C<$main> (of course).	113	C<$Coro::main> (of course).
111		114
112	This variable is B<strictly> I<read-only>. It is provided for performance	115	This variable is B<strictly> I<read-only>. You can take copies of the
113	reasons. If performance is not essentiel you are encouraged to use the	116	value stored in it and use it as any other Coro object, but you must
114	C<Coro::current> function instead.	117	not otherwise modify the variable itself.
115		118
116	=cut	119	=cut
117		120
118	# maybe some other module used Coro::Specific before...
119	$main->{specific} = $current->{specific}
120	if $current;
121
122	_set_current $main;
123
124	sub current() { $current }	121	sub current() { $current } # [DEPRECATED]
125		122
126	=item $idle	123	=item $Coro::idle
127		124
128	A callback that is called whenever the scheduler finds no ready coroutines	125	This variable is mainly useful to integrate Coro into event loops. It is
		126	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
		127	pretty low-level functionality.
		128
		129	This variable stores a Coro object that is put into the ready queue when
		130	there are no other ready threads (without invoking any ready hooks).
		131
129	to run. The default implementation prints "FATAL: deadlock detected" and	132	The default implementation dies with "FATAL: deadlock detected.", followed
130	exits, because the program has no other way to continue.	133	by a thread listing, because the program has no other way to continue.
131		134
132	This hook is overwritten by modules such as C<Coro::Timer> and	135	This hook is overwritten by modules such as C<Coro::EV> and
133	C<Coro::Event> to wait on an external event that hopefully wake up a	136	C<Coro::AnyEvent> to wait on an external event that hopefully wakes up a
134	coroutine so the scheduler can run it.	137	coro so the scheduler can run it.
135		138
136	Please note that if your callback recursively invokes perl (e.g. for event	139	See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
137	handlers), then it must be prepared to be called recursively.
138		140
139	=cut	141	=cut
140		142
141	$idle = sub {	143	# \|\|= because other modules could have provided their own by now
142	require Carp;	144	$idle \|\|= new Coro sub {
143	Carp::croak ("FATAL: deadlock detected");	145	require Coro::Debug;
		146	die "FATAL: deadlock detected.\n"
		147	. Coro::Debug::ps_listing ();
144	};	148	};
145		149
146	# this coroutine is necessary because a coroutine	150	# this coro is necessary because a coro
147	# cannot destroy itself.	151	# cannot destroy itself.
148	my @destroy;	152	our @destroy;
		153	our $manager;
		154
149	my $manager; $manager = new Coro sub {	155	$manager = new Coro sub {
150	while () {	156	while () {
151	# by overwriting the state object with the manager we destroy it	157	Coro::State::cancel shift @destroy
152	# while still being able to schedule this coroutine (in case it has
153	# been readied multiple times. this is harmless since the manager
154	# can be called as many times as neccessary and will always
155	# remove itself from the runqueue
156	while (@destroy) {	158	while @destroy;
157	my $coro = pop @destroy;
158		159
159	$coro->{status} \|\|= [];
160
161	$_->ready for @{(delete $coro->{join} ) \|\| []};
162	$_->(@{$coro->{status}}) for @{(delete $coro->{destroy_cb}) \|\| []};
163
164	# the next line destroys the coro state, but keeps the
165	# coroutine itself intact (we basically make it a zombie
166	# coroutine that always runs the manager thread, so it's possible
167	# to transfer() to this coroutine).
168	$coro->_clone_state_from ($manager);
169	}
170	&schedule;	160	&schedule;
171	}	161	}
172	};	162	};
173		163	$manager->{desc} = "[coro manager]";
174	# static methods. not really.	164	$manager->prio (PRIO_MAX);
175		165
176	=back	166	=back
177		167
178	=head2 STATIC METHODS	168	=head1 SIMPLE CORO CREATION
179
180	Static methods are actually functions that operate on the current coroutine only.
181		169
182	=over 4	170	=over 4
183		171
184	=item async { ... } [@args...]	172	=item async { ... } [@args...]
185		173
186	Create a new asynchronous coroutine and return it's coroutine object	174	Create a new coro and return its Coro object (usually
187	(usually unused). When the sub returns the new coroutine is automatically	175	unused). The coro will be put into the ready queue, so
		176	it will start running automatically on the next scheduler run.
		177
		178	The first argument is a codeblock/closure that should be executed in the
		179	coro. When it returns argument returns the coro is automatically
188	terminated.	180	terminated.
189		181
190	Calling C<exit> in a coroutine will not work correctly, so do not do that.	182	The remaining arguments are passed as arguments to the closure.
191		183
192	When the coroutine dies, the program will exit, just as in the main	184	See the C<Coro::State::new> constructor for info about the coro
193	program.	185	environment in which coro are executed.
194		186
		187	Calling C<exit> in a coro will do the same as calling exit outside
		188	the coro. Likewise, when the coro dies, the program will exit,
		189	just as it would in the main program.
		190
		191	If you do not want that, you can provide a default C<die> handler, or
		192	simply avoid dieing (by use of C<eval>).
		193
195	# create a new coroutine that just prints its arguments	194	Example: Create a new coro that just prints its arguments.
		195
196	async {	196	async {
197	print "@_\n";	197	print "@_\n";
198	} 1,2,3,4;	198	} 1,2,3,4;
199		199
200	=cut	200	=item async_pool { ... } [@args...]
201		201
202	sub async(&@) {	202	Similar to C<async>, but uses a coro pool, so you should not call
203	my $pid = new Coro @_;	203	terminate or join on it (although you are allowed to), and you get a
204	$pid->ready;	204	coro that might have executed other code already (which can be good
205	$pid	205	or bad :).
		206
		207	On the plus side, this function is about twice as fast as creating (and
		208	destroying) a completely new coro, so if you need a lot of generic
		209	coros in quick successsion, use C<async_pool>, not C<async>.
		210
		211	The code block is executed in an C<eval> context and a warning will be
		212	issued in case of an exception instead of terminating the program, as
		213	C<async> does. As the coro is being reused, stuff like C<on_destroy>
		214	will not work in the expected way, unless you call terminate or cancel,
		215	which somehow defeats the purpose of pooling (but is fine in the
		216	exceptional case).
		217
		218	The priority will be reset to C<0> after each run, tracing will be
		219	disabled, the description will be reset and the default output filehandle
		220	gets restored, so you can change all these. Otherwise the coro will
		221	be re-used "as-is": most notably if you change other per-coro global
		222	stuff such as C<$/> you I<must needs> revert that change, which is most
		223	simply done by using local as in: C<< local $/ >>.
		224
		225	The idle pool size is limited to C<8> idle coros (this can be
		226	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
		227	coros as required.
		228
		229	If you are concerned about pooled coros growing a lot because a
		230	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		231	{ terminate }> once per second or so to slowly replenish the pool. In
		232	addition to that, when the stacks used by a handler grows larger than 32kb
		233	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
		234
		235	=cut
		236
		237	our $POOL_SIZE = 8;
		238	our $POOL_RSS = 32 * 1024;
		239	our @async_pool;
		240
		241	sub pool_handler {
		242	while () {
		243	eval {
		244	&{&_pool_handler} while 1;
		245	};
		246
		247	warn $@ if $@;
		248	}
206	}	249	}
207		250
		251	=back
		252
		253	=head1 STATIC METHODS
		254
		255	Static methods are actually functions that implicitly operate on the
		256	current coro.
		257
		258	=over 4
		259
208	=item schedule	260	=item schedule
209		261
210	Calls the scheduler. Please note that the current coroutine will not be put	262	Calls the scheduler. The scheduler will find the next coro that is
		263	to be run from the ready queue and switches to it. The next coro
		264	to be run is simply the one with the highest priority that is longest
		265	in its ready queue. If there is no coro ready, it will call the
		266	C<$Coro::idle> hook.
		267
		268	Please note that the current coro will I<not> be put into the ready
211	into the ready queue, so calling this function usually means you will	269	queue, so calling this function usually means you will never be called
212	never be called again unless something else (e.g. an event handler) calls	270	again unless something else (e.g. an event handler) calls C<< ->ready >>,
213	ready.	271	thus waking you up.
214		272
215	The canonical way to wait on external events is this:	273	This makes C<schedule> I<the> generic method to use to block the current
		274	coro and wait for events: first you remember the current coro in
		275	a variable, then arrange for some callback of yours to call C<< ->ready
		276	>> on that once some event happens, and last you call C<schedule> to put
		277	yourself to sleep. Note that a lot of things can wake your coro up,
		278	so you need to check whether the event indeed happened, e.g. by storing the
		279	status in a variable.
216		280
		281	See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
		282
		283	=item cede
		284
		285	"Cede" to other coros. This function puts the current coro into
		286	the ready queue and calls C<schedule>, which has the effect of giving
		287	up the current "timeslice" to other coros of the same or higher
		288	priority. Once your coro gets its turn again it will automatically be
		289	resumed.
		290
		291	This function is often called C<yield> in other languages.
		292
		293	=item Coro::cede_notself
		294
		295	Works like cede, but is not exported by default and will cede to I<any>
		296	coro, regardless of priority. This is useful sometimes to ensure
		297	progress is made.
		298
		299	=item terminate [arg...]
		300
		301	Terminates the current coro with the given status values (see L<cancel>).
		302
		303	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
		304
		305	These function install enter and leave winders in the current scope. The
		306	enter block will be executed when on_enter is called and whenever the
		307	current coro is re-entered by the scheduler, while the leave block is
		308	executed whenever the current coro is blocked by the scheduler, and
		309	also when the containing scope is exited (by whatever means, be it exit,
		310	die, last etc.).
		311
		312	I<Neither invoking the scheduler, nor exceptions, are allowed within those
		313	BLOCKs>. That means: do not even think about calling C<die> without an
		314	eval, and do not even think of entering the scheduler in any way.
		315
		316	Since both BLOCKs are tied to the current scope, they will automatically
		317	be removed when the current scope exits.
		318
		319	These functions implement the same concept as C<dynamic-wind> in scheme
		320	does, and are useful when you want to localise some resource to a specific
		321	coro.
		322
		323	They slow down thread switching considerably for coros that use them
		324	(about 40% for a BLOCK with a single assignment, so thread switching is
		325	still reasonably fast if the handlers are fast).
		326
		327	These functions are best understood by an example: The following function
		328	will change the current timezone to "Antarctica/South_Pole", which
		329	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
		330	which remember/change the current timezone and restore the previous
		331	value, respectively, the timezone is only changed for the coro that
		332	installed those handlers.
		333
		334	use POSIX qw(tzset);
		335
		336	async {
		337	my $old_tz; # store outside TZ value here
		338
		339	Coro::on_enter {
		340	$old_tz = $ENV{TZ}; # remember the old value
		341
		342	$ENV{TZ} = "Antarctica/South_Pole";
		343	tzset; # enable new value
		344	};
		345
		346	Coro::on_leave {
		347	$ENV{TZ} = $old_tz;
		348	tzset; # restore old value
		349	};
		350
		351	# at this place, the timezone is Antarctica/South_Pole,
		352	# without disturbing the TZ of any other coro.
		353	};
		354
		355	This can be used to localise about any resource (locale, uid, current
		356	working directory etc.) to a block, despite the existance of other
		357	coros.
		358
		359	Another interesting example implements time-sliced multitasking using
		360	interval timers (this could obviously be optimised, but does the job):
		361
		362	# "timeslice" the given block
		363	sub timeslice(&) {
		364	use Time::HiRes ();
		365
		366	Coro::on_enter {
		367	# on entering the thread, we set an VTALRM handler to cede
		368	$SIG{VTALRM} = sub { cede };
		369	# and then start the interval timer
		370	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
		371	};
		372	Coro::on_leave {
		373	# on leaving the thread, we stop the interval timer again
		374	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
		375	};
		376
		377	&{+shift};
		378	}
		379
		380	# use like this:
		381	timeslice {
		382	# The following is an endless loop that would normally
		383	# monopolise the process. Since it runs in a timesliced
		384	# environment, it will regularly cede to other threads.
		385	while () { }
		386	};
		387
		388
		389	=item killall
		390
		391	Kills/terminates/cancels all coros except the currently running one.
		392
		393	Note that while this will try to free some of the main interpreter
		394	resources if the calling coro isn't the main coro, but one
		395	cannot free all of them, so if a coro that is not the main coro
		396	calls this function, there will be some one-time resource leak.
		397
		398	=cut
		399
		400	sub killall {
		401	for (Coro::State::list) {
		402	$_->cancel
		403	if $_ != $current && UNIVERSAL::isa $_, "Coro";
217	{	404	}
218	# remember current coroutine	405	}
		406
		407	=back
		408
		409	=head1 CORO OBJECT METHODS
		410
		411	These are the methods you can call on coro objects (or to create
		412	them).
		413
		414	=over 4
		415
		416	=item new Coro \&sub [, @args...]
		417
		418	Create a new coro and return it. When the sub returns, the coro
		419	automatically terminates as if C<terminate> with the returned values were
		420	called. To make the coro run you must first put it into the ready
		421	queue by calling the ready method.
		422
		423	See C<async> and C<Coro::State::new> for additional info about the
		424	coro environment.
		425
		426	=cut
		427
		428	sub _coro_run {
		429	terminate &{+shift};
		430	}
		431
		432	=item $success = $coro->ready
		433
		434	Put the given coro into the end of its ready queue (there is one
		435	queue for each priority) and return true. If the coro is already in
		436	the ready queue, do nothing and return false.
		437
		438	This ensures that the scheduler will resume this coro automatically
		439	once all the coro of higher priority and all coro of the same
		440	priority that were put into the ready queue earlier have been resumed.
		441
		442	=item $coro->suspend
		443
		444	Suspends the specified coro. A suspended coro works just like any other
		445	coro, except that the scheduler will not select a suspended coro for
		446	execution.
		447
		448	Suspending a coro can be useful when you want to keep the coro from
		449	running, but you don't want to destroy it, or when you want to temporarily
		450	freeze a coro (e.g. for debugging) to resume it later.
		451
		452	A scenario for the former would be to suspend all (other) coros after a
		453	fork and keep them alive, so their destructors aren't called, but new
		454	coros can be created.
		455
		456	=item $coro->resume
		457
		458	If the specified coro was suspended, it will be resumed. Note that when
		459	the coro was in the ready queue when it was suspended, it might have been
		460	unreadied by the scheduler, so an activation might have been lost.
		461
		462	To avoid this, it is best to put a suspended coro into the ready queue
		463	unconditionally, as every synchronisation mechanism must protect itself
		464	against spurious wakeups, and the one in the Coro family certainly do
		465	that.
		466
		467	=item $is_ready = $coro->is_ready
		468
		469	Returns true iff the Coro object is in the ready queue. Unless the Coro
		470	object gets destroyed, it will eventually be scheduled by the scheduler.
		471
		472	=item $is_running = $coro->is_running
		473
		474	Returns true iff the Coro object is currently running. Only one Coro object
		475	can ever be in the running state (but it currently is possible to have
		476	multiple running Coro::States).
		477
		478	=item $is_suspended = $coro->is_suspended
		479
		480	Returns true iff this Coro object has been suspended. Suspended Coros will
		481	not ever be scheduled.
		482
		483	=item $coro->cancel (arg...)
		484
		485	Terminates the given Coro and makes it return the given arguments as
		486	status (default: the empty list). Never returns if the Coro is the
		487	current Coro.
		488
		489	=cut
		490
		491	sub cancel {
		492	my $self = shift;
		493
		494	if ($current == $self) {
		495	terminate @_;
		496	} else {
		497	$self->{_status} = [@_];
		498	Coro::State::cancel $self;
		499	}
		500	}
		501
		502	=item $coro->schedule_to
		503
		504	Puts the current coro to sleep (like C<Coro::schedule>), but instead
		505	of continuing with the next coro from the ready queue, always switch to
		506	the given coro object (regardless of priority etc.). The readyness
		507	state of that coro isn't changed.
		508
		509	This is an advanced method for special cases - I'd love to hear about any
		510	uses for this one.
		511
		512	=item $coro->cede_to
		513
		514	Like C<schedule_to>, but puts the current coro into the ready
		515	queue. This has the effect of temporarily switching to the given
		516	coro, and continuing some time later.
		517
		518	This is an advanced method for special cases - I'd love to hear about any
		519	uses for this one.
		520
		521	=item $coro->throw ([$scalar])
		522
		523	If C<$throw> is specified and defined, it will be thrown as an exception
		524	inside the coro at the next convenient point in time. Otherwise
		525	clears the exception object.
		526
		527	Coro will check for the exception each time a schedule-like-function
		528	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
		529	>>, C<< Coro::Handle->readable >> and so on. Most of these functions
		530	detect this case and return early in case an exception is pending.
		531
		532	The exception object will be thrown "as is" with the specified scalar in
		533	C<$@>, i.e. if it is a string, no line number or newline will be appended
		534	(unlike with C<die>).
		535
		536	This can be used as a softer means than C<cancel> to ask a coro to
		537	end itself, although there is no guarantee that the exception will lead to
		538	termination, and if the exception isn't caught it might well end the whole
		539	program.
		540
		541	You might also think of C<throw> as being the moral equivalent of
		542	C<kill>ing a coro with a signal (in this case, a scalar).
		543
		544	=item $coro->join
		545
		546	Wait until the coro terminates and return any values given to the
		547	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		548	from multiple coro, and all will be resumed and given the status
		549	return once the C<$coro> terminates.
		550
		551	=cut
		552
		553	sub join {
		554	my $self = shift;
		555
		556	unless ($self->{_status}) {
219	my $current = $Coro::current;	557	my $current = $current;
220		558
221	# register a hypothetical event handler	559	push @{$self->{_on_destroy}}, sub {
222	on_event_invoke sub {
223	# wake up sleeping coroutine
224	$current->ready;	560	$current->ready;
225	undef $current;	561	undef $current;
226	};	562	};
227		563
228	# call schedule until event occured.
229	# in case we are woken up for other reasons
230	# (current still defined), loop.
231	Coro::schedule while $current;	564	&schedule while $current;
232	}	565	}
233		566
234	=item cede	567	wantarray ? @{$self->{_status}} : $self->{_status}[0];
235
236	"Cede" to other coroutines. This function puts the current coroutine into the
237	ready queue and calls C<schedule>, which has the effect of giving up the
238	current "timeslice" to other coroutines of the same or higher priority.
239
240	=item terminate [arg...]
241
242	Terminates the current coroutine with the given status values (see L<cancel>).
243
244	=cut
245
246	sub terminate {
247	$current->cancel (@_);
248	}	568	}
249		569
250	=back
251
252	# dynamic methods
253
254	=head2 COROUTINE METHODS
255
256	These are the methods you can call on coroutine objects.
257
258	=over 4
259
260	=item new Coro \&sub [, @args...]
261
262	Create a new coroutine and return it. When the sub returns the coroutine
263	automatically terminates as if C<terminate> with the returned values were
264	called. To make the coroutine run you must first put it into the ready queue
265	by calling the ready method.
266
267	Calling C<exit> in a coroutine will not work correctly, so do not do that.
268
269	=cut
270
271	sub _run_coro {
272	terminate &{+shift};
273	}
274
275	sub new {
276	my $class = shift;
277
278	$class->SUPER::new (\&_run_coro, @_)
279	}
280
281	=item $success = $coroutine->ready
282
283	Put the given coroutine into the ready queue (according to it's priority)
284	and return true. If the coroutine is already in the ready queue, do nothing
285	and return false.
286
287	=item $is_ready = $coroutine->is_ready
288
289	Return wether the coroutine is currently the ready queue or not,
290
291	=item $coroutine->cancel (arg...)
292
293	Terminates the given coroutine and makes it return the given arguments as
294	status (default: the empty list).
295
296	=cut
297
298	sub cancel {
299	my $self = shift;
300	$self->{status} = [@_];
301	push @destroy, $self;
302	$manager->ready;
303	&schedule if $current == $self;
304	}
305
306	=item $coroutine->join
307
308	Wait until the coroutine terminates and return any values given to the
309	C<terminate> or C<cancel> functions. C<join> can be called multiple times
310	from multiple coroutine.
311
312	=cut
313
314	sub join {
315	my $self = shift;
316	unless ($self->{status}) {
317	push @{$self->{join}}, $current;
318	&schedule;
319	}
320	wantarray ? @{$self->{status}} : $self->{status}[0];
321	}
322
323	=item $coroutine->on_destroy (\&cb)	570	=item $coro->on_destroy (\&cb)
324		571
325	Registers a callback that is called when this coroutine gets destroyed,	572	Registers a callback that is called when this coro thread gets destroyed,
326	but before it is joined. The callback gets passed the terminate arguments,	573	but before it is joined. The callback gets passed the terminate arguments,
327	if any.	574	if any, and I<must not> die, under any circumstances.
		575
		576	There can be any number of C<on_destroy> callbacks per coro.
328		577
329	=cut	578	=cut
330		579
331	sub on_destroy {	580	sub on_destroy {
332	my ($self, $cb) = @_;	581	my ($self, $cb) = @_;
333		582
334	push @{ $self->{destroy_cb} }, $cb;	583	push @{ $self->{_on_destroy} }, $cb;
335	}	584	}
336		585
337	=item $oldprio = $coroutine->prio ($newprio)	586	=item $oldprio = $coro->prio ($newprio)
338		587
339	Sets (or gets, if the argument is missing) the priority of the	588	Sets (or gets, if the argument is missing) the priority of the
340	coroutine. Higher priority coroutines get run before lower priority	589	coro thread. Higher priority coro get run before lower priority
341	coroutines. Priorities are small signed integers (currently -4 .. +3),	590	coros. Priorities are small signed integers (currently -4 .. +3),
342	that you can refer to using PRIO_xxx constants (use the import tag :prio	591	that you can refer to using PRIO_xxx constants (use the import tag :prio
343	to get then):	592	to get then):
344		593
345	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	594	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
346	3 > 1 > 0 > -1 > -3 > -4	595	3 > 1 > 0 > -1 > -3 > -4
347		596
348	# set priority to HIGH	597	# set priority to HIGH
349	current->prio(PRIO_HIGH);	598	current->prio (PRIO_HIGH);
350		599
351	The idle coroutine ($Coro::idle) always has a lower priority than any	600	The idle coro thread ($Coro::idle) always has a lower priority than any
352	existing coroutine.	601	existing coro.
353		602
354	Changing the priority of the current coroutine will take effect immediately,	603	Changing the priority of the current coro will take effect immediately,
355	but changing the priority of coroutines in the ready queue (but not	604	but changing the priority of a coro in the ready queue (but not running)
356	running) will only take effect after the next schedule (of that	605	will only take effect after the next schedule (of that coro). This is a
357	coroutine). This is a bug that will be fixed in some future version.	606	bug that will be fixed in some future version.
358		607
359	=item $newprio = $coroutine->nice ($change)	608	=item $newprio = $coro->nice ($change)
360		609
361	Similar to C<prio>, but subtract the given value from the priority (i.e.	610	Similar to C<prio>, but subtract the given value from the priority (i.e.
362	higher values mean lower priority, just as in unix).	611	higher values mean lower priority, just as in UNIX's nice command).
363		612
364	=item $olddesc = $coroutine->desc ($newdesc)	613	=item $olddesc = $coro->desc ($newdesc)
365		614
366	Sets (or gets in case the argument is missing) the description for this	615	Sets (or gets in case the argument is missing) the description for this
367	coroutine. This is just a free-form string you can associate with a coroutine.	616	coro thread. This is just a free-form string you can associate with a
		617	coro.
		618
		619	This method simply sets the C<< $coro->{desc} >> member to the given
		620	string. You can modify this member directly if you wish, and in fact, this
		621	is often preferred to indicate major processing states that cna then be
		622	seen for example in a L<Coro::Debug> session:
		623
		624	sub my_long_function {
		625	local $Coro::current->{desc} = "now in my_long_function";
		626	...
		627	$Coro::current->{desc} = "my_long_function: phase 1";
		628	...
		629	$Coro::current->{desc} = "my_long_function: phase 2";
		630	...
		631	}
368		632
369	=cut	633	=cut
370		634
371	sub desc {	635	sub desc {
372	my $old = $_[0]{desc};	636	my $old = $_[0]{desc};
373	$_[0]{desc} = $_[1] if @_ > 1;	637	$_[0]{desc} = $_[1] if @_ > 1;
374	$old;	638	$old;
375	}	639	}
376		640
		641	sub transfer {
		642	require Carp;
		643	Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught");
		644	}
		645
377	=back	646	=back
378		647
379	=head2 GLOBAL FUNCTIONS	648	=head1 GLOBAL FUNCTIONS
380		649
381	=over 4	650	=over 4
382		651
383	=item Coro::nready	652	=item Coro::nready
384		653
385	Returns the number of coroutines that are currently in the ready state,	654	Returns the number of coro that are currently in the ready state,
386	i.e. that can be swicthed to. The value C<0> means that the only runnable	655	i.e. that can be switched to by calling C<schedule> directory or
		656	indirectly. The value C<0> means that the only runnable coro is the
387	coroutine is the currently running one, so C<cede> would have no effect,	657	currently running one, so C<cede> would have no effect, and C<schedule>
388	and C<schedule> would cause a deadlock unless there is an idle handler	658	would cause a deadlock unless there is an idle handler that wakes up some
389	that wakes up some coroutines.	659	coro.
		660
		661	=item my $guard = Coro::guard { ... }
		662
		663	This function still exists, but is deprecated. Please use the
		664	C<Guard::guard> function instead.
		665
		666	=cut
		667
		668	BEGIN { *guard = \&Guard::guard }
390		669
391	=item unblock_sub { ... }	670	=item unblock_sub { ... }
392		671
393	This utility function takes a BLOCK or code reference and "unblocks" it,	672	This utility function takes a BLOCK or code reference and "unblocks" it,
394	returning the new coderef. This means that the new coderef will return	673	returning a new coderef. Unblocking means that calling the new coderef
395	immediately without blocking, returning nothing, while the original code	674	will return immediately without blocking, returning nothing, while the
396	ref will be called (with parameters) from within its own coroutine.	675	original code ref will be called (with parameters) from within another
		676	coro.
397		677
398	The reason this fucntion exists is that many event libraries (such as the	678	The reason this function exists is that many event libraries (such as
399	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form	679	the venerable L<Event\|Event> module) are not thread-safe (a weaker form
400	of thread-safety). This means you must not block within event callbacks,	680	of reentrancy). This means you must not block within event callbacks,
401	otherwise you might suffer from crashes or worse.	681	otherwise you might suffer from crashes or worse. The only event library
		682	currently known that is safe to use without C<unblock_sub> is L<EV> (but
		683	you might still run into deadlocks if all event loops are blocked).
		684
		685	Coro will try to catch you when you block in the event loop
		686	("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and
		687	only works when you do not run your own event loop.
402		688
403	This function allows your callbacks to block by executing them in another	689	This function allows your callbacks to block by executing them in another
404	coroutine where it is safe to block. One example where blocking is handy	690	coro where it is safe to block. One example where blocking is handy
405	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	691	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
406	disk.	692	disk, for example.
407		693
408	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when	694	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
409	creating event callbacks that want to block.	695	creating event callbacks that want to block.
410		696
411	=cut	697	If your handler does not plan to block (e.g. simply sends a message to
		698	another coro, or puts some other coro into the ready queue), there is
		699	no reason to use C<unblock_sub>.
412		700
413	our @unblock_pool;	701	Note that you also need to use C<unblock_sub> for any other callbacks that
		702	are indirectly executed by any C-based event loop. For example, when you
		703	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		704	provides callbacks that are the result of some event callback, then you
		705	must not block either, or use C<unblock_sub>.
		706
		707	=cut
		708
414	our @unblock_queue;	709	our @unblock_queue;
415	our $UNBLOCK_POOL_SIZE = 2;
416		710
417	sub unblock_handler_ {	711	# we create a special coro because we want to cede,
418	while () {	712	# to reduce pressure on the coro pool (because most callbacks
419	my ($cb, @arg) = @{ delete $Coro::current->{arg} };	713	# return immediately and can be reused) and because we cannot cede
420	$cb->(@arg);	714	# inside an event callback.
421
422	last if @unblock_pool >= $UNBLOCK_POOL_SIZE;
423	push @unblock_pool, $Coro::current;
424	schedule;
425	}
426	}
427
428	our $unblock_scheduler = async {	715	our $unblock_scheduler = new Coro sub {
429	while () {	716	while () {
430	while (my $cb = pop @unblock_queue) {	717	while (my $cb = pop @unblock_queue) {
431	my $handler = (pop @unblock_pool or new Coro \&unblock_handler_);	718	&async_pool (@$cb);
432	$handler->{arg} = $cb;	719
433	$handler->ready;	720	# for short-lived callbacks, this reduces pressure on the coro pool
		721	# as the chance is very high that the async_poll coro will be back
		722	# in the idle state when cede returns
434	cede;	723	cede;
435	}	724	}
436		725	schedule; # sleep well
437	schedule;
438	}	726	}
439	};	727	};
		728	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
440		729
441	sub unblock_sub(&) {	730	sub unblock_sub(&) {
442	my $cb = shift;	731	my $cb = shift;
443		732
444	sub {	733	sub {
445	push @unblock_queue, [$cb, @_];	734	unshift @unblock_queue, [$cb, @_];
446	$unblock_scheduler->ready;	735	$unblock_scheduler->ready;
447	}	736	}
448	}	737	}
449		738
		739	=item $cb = rouse_cb
		740
		741	Create and return a "rouse callback". That's a code reference that,
		742	when called, will remember a copy of its arguments and notify the owner
		743	coro of the callback.
		744
		745	See the next function.
		746
		747	=item @args = rouse_wait [$cb]
		748
		749	Wait for the specified rouse callback (or the last one that was created in
		750	this coro).
		751
		752	As soon as the callback is invoked (or when the callback was invoked
		753	before C<rouse_wait>), it will return the arguments originally passed to
		754	the rouse callback. In scalar context, that means you get the I<last>
		755	argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
		756	statement at the end.
		757
		758	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
		759
450	=back	760	=back
451		761
452	=cut	762	=cut
453		763
		764	for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) {
		765	my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"};
		766
		767	*{"Coro::$module\::new"} = sub {
		768	require "Coro/$module.pm";
		769
		770	# some modules have their new predefined in State.xs, some don't
		771	*{"Coro::$module\::new"} = $old
		772	if $old;
		773
		774	goto &{"Coro::$module\::new"};
		775	};
		776	}
		777
454	1;	778	1;
455		779
		780	=head1 HOW TO WAIT FOR A CALLBACK
		781
		782	It is very common for a coro to wait for some callback to be
		783	called. This occurs naturally when you use coro in an otherwise
		784	event-based program, or when you use event-based libraries.
		785
		786	These typically register a callback for some event, and call that callback
		787	when the event occured. In a coro, however, you typically want to
		788	just wait for the event, simplyifying things.
		789
		790	For example C<< AnyEvent->child >> registers a callback to be called when
		791	a specific child has exited:
		792
		793	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		794
		795	But from within a coro, you often just want to write this:
		796
		797	my $status = wait_for_child $pid;
		798
		799	Coro offers two functions specifically designed to make this easy,
		800	C<Coro::rouse_cb> and C<Coro::rouse_wait>.
		801
		802	The first function, C<rouse_cb>, generates and returns a callback that,
		803	when invoked, will save its arguments and notify the coro that
		804	created the callback.
		805
		806	The second function, C<rouse_wait>, waits for the callback to be called
		807	(by calling C<schedule> to go to sleep) and returns the arguments
		808	originally passed to the callback.
		809
		810	Using these functions, it becomes easy to write the C<wait_for_child>
		811	function mentioned above:
		812
		813	sub wait_for_child($) {
		814	my ($pid) = @_;
		815
		816	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		817
		818	my ($rpid, $rstatus) = Coro::rouse_wait;
		819	$rstatus
		820	}
		821
		822	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
		823	you can roll your own, using C<schedule>:
		824
		825	sub wait_for_child($) {
		826	my ($pid) = @_;
		827
		828	# store the current coro in $current,
		829	# and provide result variables for the closure passed to ->child
		830	my $current = $Coro::current;
		831	my ($done, $rstatus);
		832
		833	# pass a closure to ->child
		834	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		835	$rstatus = $_[1]; # remember rstatus
		836	$done = 1; # mark $rstatus as valud
		837	});
		838
		839	# wait until the closure has been called
		840	schedule while !$done;
		841
		842	$rstatus
		843	}
		844
		845
456	=head1 BUGS/LIMITATIONS	846	=head1 BUGS/LIMITATIONS
457		847
458	- you must make very sure that no coro is still active on global	848	=over 4
459	destruction. very bad things might happen otherwise (usually segfaults).
460		849
		850	=item fork with pthread backend
		851
		852	When Coro is compiled using the pthread backend (which isn't recommended
		853	but required on many BSDs as their libcs are completely broken), then
		854	coro will not survive a fork. There is no known workaround except to
		855	fix your libc and use a saner backend.
		856
		857	=item perl process emulation ("threads")
		858
461	- this module is not thread-safe. You should only ever use this module	859	This module is not perl-pseudo-thread-safe. You should only ever use this
462	from the same thread (this requirement might be losened in the future	860	module from the first thread (this requirement might be removed in the
463	to allow per-thread schedulers, but Coro::State does not yet allow	861	future to allow per-thread schedulers, but Coro::State does not yet allow
464	this).	862	this). I recommend disabling thread support and using processes, as having
		863	the windows process emulation enabled under unix roughly halves perl
		864	performance, even when not used.
		865
		866	=item coro switching is not signal safe
		867
		868	You must not switch to another coro from within a signal handler (only
		869	relevant with %SIG - most event libraries provide safe signals), I<unless>
		870	you are sure you are not interrupting a Coro function.
		871
		872	That means you I<MUST NOT> call any function that might "block" the
		873	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
		874	anything that calls those. Everything else, including calling C<ready>,
		875	works.
		876
		877	=back
		878
		879
		880	=head1 WINDOWS PROCESS EMULATION
		881
		882	A great many people seem to be confused about ithreads (for example, Chip
		883	Salzenberg called me unintelligent, incapable, stupid and gullible,
		884	while in the same mail making rather confused statements about perl
		885	ithreads (for example, that memory or files would be shared), showing his
		886	lack of understanding of this area - if it is hard to understand for Chip,
		887	it is probably not obvious to everybody).
		888
		889	What follows is an ultra-condensed version of my talk about threads in
		890	scripting languages given on the perl workshop 2009:
		891
		892	The so-called "ithreads" were originally implemented for two reasons:
		893	first, to (badly) emulate unix processes on native win32 perls, and
		894	secondly, to replace the older, real thread model ("5.005-threads").
		895
		896	It does that by using threads instead of OS processes. The difference
		897	between processes and threads is that threads share memory (and other
		898	state, such as files) between threads within a single process, while
		899	processes do not share anything (at least not semantically). That
		900	means that modifications done by one thread are seen by others, while
		901	modifications by one process are not seen by other processes.
		902
		903	The "ithreads" work exactly like that: when creating a new ithreads
		904	process, all state is copied (memory is copied physically, files and code
		905	is copied logically). Afterwards, it isolates all modifications. On UNIX,
		906	the same behaviour can be achieved by using operating system processes,
		907	except that UNIX typically uses hardware built into the system to do this
		908	efficiently, while the windows process emulation emulates this hardware in
		909	software (rather efficiently, but of course it is still much slower than
		910	dedicated hardware).
		911
		912	As mentioned before, loading code, modifying code, modifying data
		913	structures and so on is only visible in the ithreads process doing the
		914	modification, not in other ithread processes within the same OS process.
		915
		916	This is why "ithreads" do not implement threads for perl at all, only
		917	processes. What makes it so bad is that on non-windows platforms, you can
		918	actually take advantage of custom hardware for this purpose (as evidenced
		919	by the forks module, which gives you the (i-) threads API, just much
		920	faster).
		921
		922	Sharing data is in the i-threads model is done by transfering data
		923	structures between threads using copying semantics, which is very slow -
		924	shared data simply does not exist. Benchmarks using i-threads which are
		925	communication-intensive show extremely bad behaviour with i-threads (in
		926	fact, so bad that Coro, which cannot take direct advantage of multiple
		927	CPUs, is often orders of magnitude faster because it shares data using
		928	real threads, refer to my talk for details).
		929
		930	As summary, i-threads use threads to implement processes, while
		931	the compatible forks module uses processes to emulate, uhm,
		932	processes. I-threads slow down every perl program when enabled, and
		933	outside of windows, serve no (or little) practical purpose, but
		934	disadvantages every single-threaded Perl program.
		935
		936	This is the reason that I try to avoid the name "ithreads", as it is
		937	misleading as it implies that it implements some kind of thread model for
		938	perl, and prefer the name "windows process emulation", which describes the
		939	actual use and behaviour of it much better.
465		940
466	=head1 SEE ALSO	941	=head1 SEE ALSO
467		942
		943	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		944
		945	Debugging: L<Coro::Debug>.
		946
468	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.	947	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
469		948
470	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.	949	Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
		950	L<Coro::SemaphoreSet>, L<Coro::RWLock>.
471		951
472	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.	952	I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
473		953
474	Embedding: L<Coro:MakeMaker>	954	Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
		955	a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
		956	L<Coro::Select>.
		957
		958	XS API: L<Coro::MakeMaker>.
		959
		960	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
475		961
476	=head1 AUTHOR	962	=head1 AUTHOR
477		963
478	Marc Lehmann <schmorp@schmorp.de>	964	Marc Lehmann <schmorp@schmorp.de>
479	http://home.schmorp.de/	965	http://home.schmorp.de/

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Comparing cvsroot/Coro/Coro.pm (file contents): Revision 1.101 by root, Fri Dec 29 08:36:34 2006 UTC vs. Revision 1.285 by root, Thu Feb 17 01:32:18 2011 UTC

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Revision 1.285 by root, Thu Feb 17 01:32:18 2011 UTC