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

Comparing Coro/Coro.pm (file contents):
Revision 1.20 by root, Sat Jul 21 18:21:45 2001 UTC vs.
Revision 1.213 by root, Tue Nov 11 03:26:58 2008 UTC

…		…
2		2
3	Coro - coroutine process abstraction	3	Coro - coroutine process abstraction
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 coroutine
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
23	This module collection manages coroutines. Coroutines are similar to	31	This module collection manages coroutines. Coroutines are similar to
24	Threads but don't run in parallel.	32	threads but don't (in general) run in parallel at the same time even
		33	on SMP machines. The specific flavor of coroutine used in this module
		34	also guarantees you that it will not switch between coroutines unless
		35	necessary, at easily-identified points in your program, so locking and
		36	parallel access are rarely an issue, making coroutine programming much
		37	safer and easier than threads programming.
25		38
26	This module is still experimental, see the BUGS section below.	39	Unlike a normal perl program, however, coroutines allow you to have
		40	multiple running interpreters that share data, which is especially useful
		41	to code pseudo-parallel processes and for event-based programming, such as
		42	multiple HTTP-GET requests running concurrently. See L<Coro::AnyEvent> to
		43	learn more.
27		44
		45	Coroutines are also useful because Perl has no support for threads (the so
		46	called "threads" that perl offers are nothing more than the (bad) process
		47	emulation coming from the Windows platform: On standard operating systems
		48	they serve no purpose whatsoever, except by making your programs slow and
		49	making them use a lot of memory. Best disable them when building perl, or
		50	aks your software vendor/distributor to do it for you).
		51
28	In this module, coroutines are defined as "callchain + lexical variables	52	In this module, coroutines are defined as "callchain + lexical variables +
29	+ @_ + $_ + $@ + $^W), that is, a coroutine has it's own callchain, it's	53	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
30	own set of lexicals and it's own set of perl's most important global	54	its own set of lexicals and its own set of perls most important global
31	variables.	55	variables (see L<Coro::State> for more configuration).
32		56
33	=cut	57	=cut
34		58
35	package Coro;	59	package Coro;
36		60
		61	use strict qw(vars subs);
		62	no warnings "uninitialized";
		63
37	use Coro::State;	64	use Coro::State;
38		65
39	use base Exporter;	66	use base qw(Coro::State Exporter);
40		67
		68	our $idle; # idle handler
		69	our $main; # main coroutine
		70	our $current; # current coroutine
		71
41	$VERSION = 0.10;	72	our $VERSION = 4.901;
42		73
43	@EXPORT = qw(async yield schedule terminate current);	74	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
44	@EXPORT_OK = qw($current);	75	our %EXPORT_TAGS = (
		76	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		77	);
		78	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
45		79
46	{	80	=over 4
47	my @async;
48		81
49	# this way of handling attributes simply is NOT scalable ;()
50	sub import {
51	Coro->export_to_level(1, @_);
52	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
53	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
54	my ($package, $ref) = (shift, shift);
55	my @attrs;
56	for (@_) {
57	if ($_ eq "Coro") {
58	push @async, $ref;
59	} else {
60	push @attrs, $_;
61	}
62	}
63	return $old ? $old->($package, $ref, @attrs) : @attrs;
64	};
65	}
66
67	sub INIT {
68	&async(pop @async) while @async;
69	}
70	}
71
72	=item $main	82	=item $Coro::main
73		83
74	This coroutine represents the main program.	84	This variable stores the coroutine object that represents the main
		85	program. While you cna C<ready> it and do most other things you can do to
		86	coroutines, it is mainly useful to compare again C<$Coro::current>, to see
		87	whether you are running in the main program or not.
75		88
76	=cut	89	=cut
77		90
78	our $main = new Coro;	91	$main = new Coro;
79		92
80	=item $current (or as function: current)	93	=item $Coro::current
81		94
82	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).	95	The coroutine object representing the current coroutine (the last
		96	coroutine that the Coro scheduler switched to). The initial value is
		97	C<$main> (of course).
83		98
		99	This variable is B<strictly> I<read-only>. You can take copies of the
		100	value stored in it and use it as any other coroutine object, but you must
		101	not otherwise modify the variable itself.
		102
84	=cut	103	=cut
		104
		105	$main->{desc} = "[main::]";
85		106
86	# maybe some other module used Coro::Specific before...	107	# maybe some other module used Coro::Specific before...
87	if ($current) {
88	$main->{specific} = $current->{specific};	108	$main->{_specific} = $current->{_specific}
89	}	109	if $current;
90		110
91	our $current = $main;	111	_set_current $main;
92		112
93	sub current() { $current }	113	sub current() { $current } # [DEPRECATED]
94		114
95	=item $idle	115	=item $Coro::idle
96		116
97	The coroutine to switch to when no other coroutine is running. The default	117	This variable is mainly useful to integrate Coro into event loops. It is
98	implementation prints "FATAL: deadlock detected" and exits.	118	usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is
		119	pretty low-level functionality.
99		120
100	=cut	121	This variable stores a callback that is called whenever the scheduler
		122	finds no ready coroutines to run. The default implementation prints
		123	"FATAL: deadlock detected" and exits, because the program has no other way
		124	to continue.
101		125
102	# should be done using priorities :(	126	This hook is overwritten by modules such as C<Coro::Timer> and
103	our $idle = new Coro sub {	127	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
104	print STDERR "FATAL: deadlock detected\n";	128	coroutine so the scheduler can run it.
105	exit(51);	129
		130	Note that the callback I<must not>, under any circumstances, block
		131	the current coroutine. Normally, this is achieved by having an "idle
		132	coroutine" that calls the event loop and then blocks again, and then
		133	readying that coroutine in the idle handler.
		134
		135	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
		136	technique.
		137
		138	Please note that if your callback recursively invokes perl (e.g. for event
		139	handlers), then it must be prepared to be called recursively itself.
		140
		141	=cut
		142
		143	$idle = sub {
		144	require Carp;
		145	Carp::croak ("FATAL: deadlock detected");
106	};	146	};
107		147
108	# we really need priorities...	148	sub _cancel {
109	my @ready; # the ready queue. hehe, rather broken ;)	149	my ($self) = @_;
110		150
111	# static methods. not really.	151	# free coroutine data and mark as destructed
		152	$self->_destroy
		153	or return;
112		154
113	=head2 STATIC METHODS	155	# call all destruction callbacks
		156	$_->(@{$self->{_status}})
		157	for @{ delete $self->{_on_destroy} \|\| [] };
		158	}
114		159
115	Static methods are actually functions that operate on the current process only.	160	# this coroutine is necessary because a coroutine
		161	# cannot destroy itself.
		162	my @destroy;
		163	my $manager;
		164
		165	$manager = new Coro sub {
		166	while () {
		167	(shift @destroy)->_cancel
		168	while @destroy;
		169
		170	&schedule;
		171	}
		172	};
		173	$manager->{desc} = "[coro manager]";
		174	$manager->prio (PRIO_MAX);
		175
		176	=back
		177
		178	=head2 SIMPLE COROUTINE CREATION
116		179
117	=over 4	180	=over 4
118		181
119	=item async { ... } [@args...]	182	=item async { ... } [@args...]
120		183
121	Create a new asynchronous process and return it's process object	184	Create a new coroutine and return it's coroutine object (usually
122	(usually unused). When the sub returns the new process is automatically	185	unused). The coroutine will be put into the ready queue, so
		186	it will start running automatically on the next scheduler run.
		187
		188	The first argument is a codeblock/closure that should be executed in the
		189	coroutine. When it returns argument returns the coroutine is automatically
123	terminated.	190	terminated.
124		191
		192	The remaining arguments are passed as arguments to the closure.
		193
		194	See the C<Coro::State::new> constructor for info about the coroutine
		195	environment in which coroutines are executed.
		196
		197	Calling C<exit> in a coroutine will do the same as calling exit outside
		198	the coroutine. Likewise, when the coroutine dies, the program will exit,
		199	just as it would in the main program.
		200
		201	If you do not want that, you can provide a default C<die> handler, or
		202	simply avoid dieing (by use of C<eval>).
		203
125	# create a new coroutine that just prints its arguments	204	Example: Create a new coroutine that just prints its arguments.
		205
126	async {	206	async {
127	print "@_\n";	207	print "@_\n";
128	} 1,2,3,4;	208	} 1,2,3,4;
129		209
130	The coderef you submit MUST NOT be a closure that refers to variables
131	in an outer scope. This does NOT work. Pass arguments into it instead.
132
133	=cut	210	=cut
134		211
135	sub async(&@) {	212	sub async(&@) {
136	my $pid = new Coro @_;	213	my $coro = new Coro @_;
137	$pid->ready;	214	$coro->ready;
138	$pid;	215	$coro
139	}	216	}
		217
		218	=item async_pool { ... } [@args...]
		219
		220	Similar to C<async>, but uses a coroutine pool, so you should not call
		221	terminate or join on it (although you are allowed to), and you get a
		222	coroutine that might have executed other code already (which can be good
		223	or bad :).
		224
		225	On the plus side, this function is faster than creating (and destroying)
		226	a completly new coroutine, so if you need a lot of generic coroutines in
		227	quick successsion, use C<async_pool>, not C<async>.
		228
		229	The code block is executed in an C<eval> context and a warning will be
		230	issued in case of an exception instead of terminating the program, as
		231	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		232	will not work in the expected way, unless you call terminate or cancel,
		233	which somehow defeats the purpose of pooling (but is fine in the
		234	exceptional case).
		235
		236	The priority will be reset to C<0> after each run, tracing will be
		237	disabled, the description will be reset and the default output filehandle
		238	gets restored, so you can change all these. Otherwise the coroutine will
		239	be re-used "as-is": most notably if you change other per-coroutine global
		240	stuff such as C<$/> you I<must needs> revert that change, which is most
		241	simply done by using local as in: C<< local $/ >>.
		242
		243	The idle pool size is limited to C<8> idle coroutines (this can be
		244	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
		245	coros as required.
		246
		247	If you are concerned about pooled coroutines growing a lot because a
		248	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		249	{ terminate }> once per second or so to slowly replenish the pool. In
		250	addition to that, when the stacks used by a handler grows larger than 16kb
		251	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
		252
		253	=cut
		254
		255	our $POOL_SIZE = 8;
		256	our $POOL_RSS = 16 * 1024;
		257	our @async_pool;
		258
		259	sub pool_handler {
		260	my $cb;
		261
		262	while () {
		263	eval {
		264	while () {
		265	_pool_1 $cb;
		266	&$cb;
		267	_pool_2 $cb;
		268	&schedule;
		269	}
		270	};
		271
		272	if ($@) {
		273	last if $@ eq "\3async_pool terminate\2\n";
		274	warn $@;
		275	}
		276	}
		277	}
		278
		279	sub async_pool(&@) {
		280	# this is also inlined into the unlock_scheduler
		281	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		282
		283	$coro->{_invoke} = [@_];
		284	$coro->ready;
		285
		286	$coro
		287	}
		288
		289	=back
		290
		291	=head2 STATIC METHODS
		292
		293	Static methods are actually functions that operate on the current coroutine.
		294
		295	=over 4
140		296
141	=item schedule	297	=item schedule
142		298
143	Calls the scheduler. Please note that the current process will not be put	299	Calls the scheduler. The scheduler will find the next coroutine that is
		300	to be run from the ready queue and switches to it. The next coroutine
		301	to be run is simply the one with the highest priority that is longest
		302	in its ready queue. If there is no coroutine ready, it will clal the
		303	C<$Coro::idle> hook.
		304
		305	Please note that the current coroutine will I<not> be put into the ready
144	into the ready queue, so calling this function usually means you will	306	queue, so calling this function usually means you will never be called
145	never be called again.	307	again unless something else (e.g. an event handler) calls C<< ->ready >>,
		308	thus waking you up.
146		309
147	=cut	310	This makes C<schedule> I<the> generic method to use to block the current
		311	coroutine and wait for events: first you remember the current coroutine in
		312	a variable, then arrange for some callback of yours to call C<< ->ready
		313	>> on that once some event happens, and last you call C<schedule> to put
		314	yourself to sleep. Note that a lot of things can wake your coroutine up,
		315	so you need to check whether the event indeed happened, e.g. by storing the
		316	status in a variable.
148		317
149	my $prev;	318	The canonical way to wait on external events is this:
150		319
151	sub schedule {	320	{
152	# should be done using priorities :(	321	# remember current coroutine
153	($prev, $current) = ($current, shift @ready \|\| $idle);	322	my $current = $Coro::current;
154	Coro::State::transfer($prev, $current);
155	}
156		323
157	=item yield	324	# register a hypothetical event handler
158		325	on_event_invoke sub {
159	Yield to other processes. This function puts the current process into the	326	# wake up sleeping coroutine
160	ready queue and calls C<schedule>.
161
162	=cut
163
164	sub yield {
165	$current->ready;	327	$current->ready;
166	&schedule;	328	undef $current;
167	}	329	};
168		330
		331	# call schedule until event occurred.
		332	# in case we are woken up for other reasons
		333	# (current still defined), loop.
		334	Coro::schedule while $current;
		335	}
		336
		337	=item cede
		338
		339	"Cede" to other coroutines. This function puts the current coroutine into
		340	the ready queue and calls C<schedule>, which has the effect of giving
		341	up the current "timeslice" to other coroutines of the same or higher
		342	priority. Once your coroutine gets its turn again it will automatically be
		343	resumed.
		344
		345	This function is often called C<yield> in other languages.
		346
		347	=item Coro::cede_notself
		348
		349	Works like cede, but is not exported by default and will cede to I<any>
		350	coroutine, regardless of priority. This is useful sometimes to ensure
		351	progress is made.
		352
169	=item terminate	353	=item terminate [arg...]
170		354
171	Terminates the current process.	355	Terminates the current coroutine with the given status values (see L<cancel>).
172		356
173	Future versions of this function will allow result arguments.	357	=item killall
		358
		359	Kills/terminates/cancels all coroutines except the currently running
		360	one. This is useful after a fork, either in the child or the parent, as
		361	usually only one of them should inherit the running coroutines.
		362
		363	Note that while this will try to free some of the main programs resources,
		364	you cannot free all of them, so if a coroutine that is not the main
		365	program calls this function, there will be some one-time resource leak.
174		366
175	=cut	367	=cut
176		368
177	sub terminate {	369	sub terminate {
178	$current->{_results} = [@_];	370	$current->cancel (@_);
179	&schedule;	371	}
		372
		373	sub killall {
		374	for (Coro::State::list) {
		375	$_->cancel
		376	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		377	}
180	}	378	}
181		379
182	=back	380	=back
183		381
184	# dynamic methods
185
186	=head2 PROCESS METHODS	382	=head2 COROUTINE METHODS
187		383
188	These are the methods you can call on process objects.	384	These are the methods you can call on coroutine objects (or to create
		385	them).
189		386
190	=over 4	387	=over 4
191		388
192	=item new Coro \&sub [, @args...]	389	=item new Coro \&sub [, @args...]
193		390
194	Create a new process and return it. When the sub returns the process	391	Create a new coroutine and return it. When the sub returns, the coroutine
195	automatically terminates. To start the process you must first put it into	392	automatically terminates as if C<terminate> with the returned values were
		393	called. To make the coroutine run you must first put it into the ready
196	the ready queue by calling the ready method.	394	queue by calling the ready method.
197		395
198	The coderef you submit MUST NOT be a closure that refers to variables	396	See C<async> and C<Coro::State::new> for additional info about the
199	in an outer scope. This does NOT work. Pass arguments into it instead.	397	coroutine environment.
200		398
201	=cut	399	=cut
202		400
203	sub _newcoro {	401	sub _run_coro {
204	terminate &{+shift};	402	terminate &{+shift};
205	}	403	}
206		404
207	sub new {	405	sub new {
208	my $class = shift;	406	my $class = shift;
209	bless {
210	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
211	}, $class;
212	}
213		407
214	=item $process->ready	408	$class->SUPER::new (\&_run_coro, @_)
		409	}
215		410
216	Put the current process into the ready queue.	411	=item $success = $coroutine->ready
217		412
218	=cut	413	Put the given coroutine into the end of its ready queue (there is one
		414	queue for each priority) and return true. If the coroutine is already in
		415	the ready queue, do nothing and return false.
219		416
220	sub ready {	417	This ensures that the scheduler will resume this coroutine automatically
221	push @ready, $_[0];	418	once all the coroutines of higher priority and all coroutines of the same
		419	priority that were put into the ready queue earlier have been resumed.
		420
		421	=item $is_ready = $coroutine->is_ready
		422
		423	Return whether the coroutine is currently the ready queue or not,
		424
		425	=item $coroutine->cancel (arg...)
		426
		427	Terminates the given coroutine and makes it return the given arguments as
		428	status (default: the empty list). Never returns if the coroutine is the
		429	current coroutine.
		430
		431	=cut
		432
		433	sub cancel {
		434	my $self = shift;
		435	$self->{_status} = [@_];
		436
		437	if ($current == $self) {
		438	push @destroy, $self;
		439	$manager->ready;
		440	&schedule while 1;
		441	} else {
		442	$self->_cancel;
		443	}
		444	}
		445
		446	=item $coroutine->throw ([$scalar])
		447
		448	If C<$throw> is specified and defined, it will be thrown as an exception
		449	inside the coroutine at the next convenient point in time (usually after
		450	it gains control at the next schedule/transfer/cede). Otherwise clears the
		451	exception object.
		452
		453	The exception object will be thrown "as is" with the specified scalar in
		454	C<$@>, i.e. if it is a string, no line number or newline will be appended
		455	(unlike with C<die>).
		456
		457	This can be used as a softer means than C<cancel> to ask a coroutine to
		458	end itself, although there is no guarantee that the exception will lead to
		459	termination, and if the exception isn't caught it might well end the whole
		460	program.
		461
		462	You might also think of C<throw> as being the moral equivalent of
		463	C<kill>ing a coroutine with a signal (in this case, a scalar).
		464
		465	=item $coroutine->join
		466
		467	Wait until the coroutine terminates and return any values given to the
		468	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		469	from multiple coroutines, and all will be resumed and given the status
		470	return once the C<$coroutine> terminates.
		471
		472	=cut
		473
		474	sub join {
		475	my $self = shift;
		476
		477	unless ($self->{_status}) {
		478	my $current = $current;
		479
		480	push @{$self->{_on_destroy}}, sub {
		481	$current->ready;
		482	undef $current;
		483	};
		484
		485	&schedule while $current;
		486	}
		487
		488	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		489	}
		490
		491	=item $coroutine->on_destroy (\&cb)
		492
		493	Registers a callback that is called when this coroutine gets destroyed,
		494	but before it is joined. The callback gets passed the terminate arguments,
		495	if any, and I<must not> die, under any circumstances.
		496
		497	=cut
		498
		499	sub on_destroy {
		500	my ($self, $cb) = @_;
		501
		502	push @{ $self->{_on_destroy} }, $cb;
		503	}
		504
		505	=item $oldprio = $coroutine->prio ($newprio)
		506
		507	Sets (or gets, if the argument is missing) the priority of the
		508	coroutine. Higher priority coroutines get run before lower priority
		509	coroutines. Priorities are small signed integers (currently -4 .. +3),
		510	that you can refer to using PRIO_xxx constants (use the import tag :prio
		511	to get then):
		512
		513	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		514	3 > 1 > 0 > -1 > -3 > -4
		515
		516	# set priority to HIGH
		517	current->prio(PRIO_HIGH);
		518
		519	The idle coroutine ($Coro::idle) always has a lower priority than any
		520	existing coroutine.
		521
		522	Changing the priority of the current coroutine will take effect immediately,
		523	but changing the priority of coroutines in the ready queue (but not
		524	running) will only take effect after the next schedule (of that
		525	coroutine). This is a bug that will be fixed in some future version.
		526
		527	=item $newprio = $coroutine->nice ($change)
		528
		529	Similar to C<prio>, but subtract the given value from the priority (i.e.
		530	higher values mean lower priority, just as in unix).
		531
		532	=item $olddesc = $coroutine->desc ($newdesc)
		533
		534	Sets (or gets in case the argument is missing) the description for this
		535	coroutine. This is just a free-form string you can associate with a
		536	coroutine.
		537
		538	This method simply sets the C<< $coroutine->{desc} >> member to the given
		539	string. You can modify this member directly if you wish.
		540
		541	=cut
		542
		543	sub desc {
		544	my $old = $_[0]{desc};
		545	$_[0]{desc} = $_[1] if @_ > 1;
		546	$old;
222	}	547	}
223		548
224	=back	549	=back
225		550
		551	=head2 GLOBAL FUNCTIONS
		552
		553	=over 4
		554
		555	=item Coro::nready
		556
		557	Returns the number of coroutines that are currently in the ready state,
		558	i.e. that can be switched to by calling C<schedule> directory or
		559	indirectly. The value C<0> means that the only runnable coroutine is the
		560	currently running one, so C<cede> would have no effect, and C<schedule>
		561	would cause a deadlock unless there is an idle handler that wakes up some
		562	coroutines.
		563
		564	=item my $guard = Coro::guard { ... }
		565
		566	This creates and returns a guard object. Nothing happens until the object
		567	gets destroyed, in which case the codeblock given as argument will be
		568	executed. This is useful to free locks or other resources in case of a
		569	runtime error or when the coroutine gets canceled, as in both cases the
		570	guard block will be executed. The guard object supports only one method,
		571	C<< ->cancel >>, which will keep the codeblock from being executed.
		572
		573	Example: set some flag and clear it again when the coroutine gets canceled
		574	or the function returns:
		575
		576	sub do_something {
		577	my $guard = Coro::guard { $busy = 0 };
		578	$busy = 1;
		579
		580	# do something that requires $busy to be true
		581	}
		582
		583	=cut
		584
		585	sub guard(&) {
		586	bless \(my $cb = $_[0]), "Coro::guard"
		587	}
		588
		589	sub Coro::guard::cancel {
		590	${$_[0]} = sub { };
		591	}
		592
		593	sub Coro::guard::DESTROY {
		594	${$_[0]}->();
		595	}
		596
		597
		598	=item unblock_sub { ... }
		599
		600	This utility function takes a BLOCK or code reference and "unblocks" it,
		601	returning a new coderef. Unblocking means that calling the new coderef
		602	will return immediately without blocking, returning nothing, while the
		603	original code ref will be called (with parameters) from within another
		604	coroutine.
		605
		606	The reason this function exists is that many event libraries (such as the
		607	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		608	of thread-safety). This means you must not block within event callbacks,
		609	otherwise you might suffer from crashes or worse. The only event library
		610	currently known that is safe to use without C<unblock_sub> is L<EV>.
		611
		612	This function allows your callbacks to block by executing them in another
		613	coroutine where it is safe to block. One example where blocking is handy
		614	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		615	disk, for example.
		616
		617	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		618	creating event callbacks that want to block.
		619
		620	If your handler does not plan to block (e.g. simply sends a message to
		621	another coroutine, or puts some other coroutine into the ready queue),
		622	there is no reason to use C<unblock_sub>.
		623
		624	Note that you also need to use C<unblock_sub> for any other callbacks that
		625	are indirectly executed by any C-based event loop. For example, when you
		626	use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
		627	provides callbacks that are the result of some event callback, then you
		628	must not block either, or use C<unblock_sub>.
		629
		630	=cut
		631
		632	our @unblock_queue;
		633
		634	# we create a special coro because we want to cede,
		635	# to reduce pressure on the coro pool (because most callbacks
		636	# return immediately and can be reused) and because we cannot cede
		637	# inside an event callback.
		638	our $unblock_scheduler = new Coro sub {
		639	while () {
		640	while (my $cb = pop @unblock_queue) {
		641	# this is an inlined copy of async_pool
		642	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		643
		644	$coro->{_invoke} = $cb;
		645	$coro->ready;
		646	cede; # for short-lived callbacks, this reduces pressure on the coro pool
		647	}
		648	schedule; # sleep well
		649	}
		650	};
		651	$unblock_scheduler->{desc} = "[unblock_sub scheduler]";
		652
		653	sub unblock_sub(&) {
		654	my $cb = shift;
		655
		656	sub {
		657	unshift @unblock_queue, [$cb, @_];
		658	$unblock_scheduler->ready;
		659	}
		660	}
		661
		662	=back
		663
226	=cut	664	=cut
227		665
228	1;	666	1;
229		667
230	=head1 BUGS/LIMITATIONS	668	=head1 BUGS/LIMITATIONS
231		669
232	- could be faster, especially when the core would introduce special	670	This module is not perl-pseudo-thread-safe. You should only ever use this
233	support for coroutines (like it does for threads).
234	- there is still a memleak on coroutine termination that I could not
235	identify. Could be as small as a single SV.
236	- this module is not well-tested.
237	- if variables or arguments "disappear" (become undef) or become
238	corrupted please contact the author so he cen iron out the
239	remaining bugs.
240	- this module is not thread-safe. You must only ever use this module from
241	the same thread (this requirement might be loosened in the future to	671	module from the same thread (this requirement might be removed in the
242	allow per-thread schedulers, but Coro::State does not yet allow this).	672	future to allow per-thread schedulers, but Coro::State does not yet allow
		673	this). I recommend disabling thread support and using processes, as this
		674	is much faster and uses less memory.
243		675
244	=head1 SEE ALSO	676	=head1 SEE ALSO
245		677
246	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,	678	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
247	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>.	679
		680	Debugging: L<Coro::Debug>.
		681
		682	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
		683
		684	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		685
		686	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
		687
		688	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.
		689
		690	XS API: L<Coro::MakeMaker>.
		691
		692	Low level Configuration, Coroutine Environment: L<Coro::State>.
248		693
249	=head1 AUTHOR	694	=head1 AUTHOR
250		695
251	Marc Lehmann <pcg@goof.com>	696	Marc Lehmann <schmorp@schmorp.de>
252	http://www.goof.com/pcg/marc/	697	http://home.schmorp.de/
253		698
254	=cut	699	=cut
255		700

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Comparing Coro/Coro.pm (file contents): Revision 1.20 by root, Sat Jul 21 18:21:45 2001 UTC vs. Revision 1.213 by root, Tue Nov 11 03:26:58 2008 UTC

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Revision 1.213 by root, Tue Nov 11 03:26:58 2008 UTC