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

Comparing cvsroot/Coro/Coro.pm (file contents):
Revision 1.30 by root, Sat Aug 11 19:59:19 2001 UTC vs.
Revision 1.181 by root, Fri May 9 22:04:37 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	my $lock = new Coro::Semaphore;
19	cede;	22	my $locked;
		23
		24	$lock->down;
		25	$locked = 1;
		26	$lock->up;
20		27
21	=head1 DESCRIPTION	28	=head1 DESCRIPTION
22		29
23	This module collection manages coroutines. Coroutines are similar to	30	This module collection manages coroutines. Coroutines are similar to
24	Threads but don't run in parallel.	31	threads but don't (in general) run in parallel at the same time even
		32	on SMP machines. The specific flavor of coroutine used in this module
		33	also guarantees you that it will not switch between coroutines unless
		34	necessary, at easily-identified points in your program, so locking and
		35	parallel access are rarely an issue, making coroutine programming much
		36	safer and easier than threads programming.
25		37
26	This module is still experimental, see the BUGS section below.	38	Unlike a normal perl program, however, coroutines allow you to have
		39	multiple running interpreters that share data, which is especially useful
		40	to code pseudo-parallel processes, such as multiple HTTP-GET requests
		41	running concurrently.
27		42
		43	Coroutines are also useful because Perl has no support for threads (the so
		44	called "threads" that perl offers are nothing more than the (bad) process
		45	emulation coming from the Windows platform: On standard operating systems
		46	they serve no purpose whatsoever, except by making your programs slow and
		47	making them use a lot of memory. Best disable them when building perl, or
		48	aks your software vendor/distributor to do it for you).
		49
28	In this module, coroutines are defined as "callchain + lexical variables	50	In this module, coroutines are defined as "callchain + lexical variables +
29	+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own	51	@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
30	callchain, it's own set of lexicals and it's own set of perl's most	52	its own set of lexicals and its own set of perls most important global
31	important global variables.	53	variables (see L<Coro::State> for more configuration).
32		54
33	=cut	55	=cut
34		56
35	package Coro;	57	package Coro;
36		58
		59	use strict;
		60	no warnings "uninitialized";
		61
37	use Coro::State;	62	use Coro::State;
38		63
39	use base Exporter;	64	use base qw(Coro::State Exporter);
40		65
41	$VERSION = 0.45;	66	our $idle; # idle handler
		67	our $main; # main coroutine
		68	our $current; # current coroutine
42		69
		70	our $VERSION = 4.6;
		71
43	@EXPORT = qw(async cede schedule terminate current);	72	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
44	@EXPORT_OK = qw($current);	73	our %EXPORT_TAGS = (
		74	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
		75	);
		76	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
45		77
46	{	78	=over 4
47	my @async;
48	my $init;
49		79
50	# this way of handling attributes simply is NOT scalable ;()
51	sub import {
52	Coro->export_to_level(1, @_);
53	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
54	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
55	my ($package, $ref) = (shift, shift);
56	my @attrs;
57	for (@_) {
58	if ($_ eq "Coro") {
59	push @async, $ref;
60	unless ($init++) {
61	eval q{
62	sub INIT {
63	&async(pop @async) while @async;
64	}
65	};
66	}
67	} else {
68	push @attrs, $_;
69	}
70	}
71	return $old ? $old->($package, $ref, @attrs) : @attrs;
72	};
73	}
74
75	}
76
77	=item $main	80	=item $Coro::main
78		81
79	This coroutine represents the main program.	82	This variable stores the coroutine object that represents the main
		83	program. While you cna C<ready> it and do most other things you can do to
		84	coroutines, it is mainly useful to compare again C<$Coro::current>, to see
		85	wether you are running in the main program or not.
80		86
81	=cut	87	=cut
82		88
83	our $main = new Coro;	89	$main = new Coro;
84		90
85	=item $current (or as function: current)	91	=item $Coro::current
86		92
87	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).	93	The coroutine object representing the current coroutine (the last
		94	coroutine that the Coro scheduler switched to). The initial value is
		95	C<$main> (of course).
88		96
		97	This variable is B<strictly> I<read-only>. You can take copies of the
		98	value stored in it and use it as any other coroutine object, but you must
		99	not otherwise modify the variable itself.
		100
89	=cut	101	=cut
		102
		103	$main->{desc} = "[main::]";
90		104
91	# maybe some other module used Coro::Specific before...	105	# maybe some other module used Coro::Specific before...
92	if ($current) {
93	$main->{specific} = $current->{specific};	106	$main->{_specific} = $current->{_specific}
94	}	107	if $current;
95		108
96	our $current = $main;	109	_set_current $main;
97		110
98	sub current() { $current }	111	sub current() { $current } # [DEPRECATED]
99		112
100	=item $idle	113	=item $Coro::idle
101		114
102	The coroutine to switch to when no other coroutine is running. The default	115	This variable is mainly useful to integrate Coro into event loops. It is
103	implementation prints "FATAL: deadlock detected" and exits.	116	usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is
		117	pretty low-level functionality.
104		118
105	=cut	119	This variable stores a callback that is called whenever the scheduler
		120	finds no ready coroutines to run. The default implementation prints
		121	"FATAL: deadlock detected" and exits, because the program has no other way
		122	to continue.
106		123
107	# should be done using priorities :(	124	This hook is overwritten by modules such as C<Coro::Timer> and
108	our $idle = new Coro sub {	125	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
109	print STDERR "FATAL: deadlock detected\n";	126	coroutine so the scheduler can run it.
110	exit(51);	127
		128	Note that the callback I<must not>, under any circumstances, block
		129	the current coroutine. Normally, this is achieved by having an "idle
		130	coroutine" that calls the event loop and then blocks again, and then
		131	readying that coroutine in the idle handler.
		132
		133	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
		134	technique.
		135
		136	Please note that if your callback recursively invokes perl (e.g. for event
		137	handlers), then it must be prepared to be called recursively itself.
		138
		139	=cut
		140
		141	$idle = sub {
		142	require Carp;
		143	Carp::croak ("FATAL: deadlock detected");
111	};	144	};
		145
		146	sub _cancel {
		147	my ($self) = @_;
		148
		149	# free coroutine data and mark as destructed
		150	$self->_destroy
		151	or return;
		152
		153	# call all destruction callbacks
		154	$_->(@{$self->{_status}})
		155	for @{(delete $self->{_on_destroy}) \|\| []};
		156	}
112		157
113	# this coroutine is necessary because a coroutine	158	# this coroutine is necessary because a coroutine
114	# cannot destroy itself.	159	# cannot destroy itself.
115	my @destroy;	160	my @destroy;
		161	my $manager;
		162
116	my $manager = new Coro sub {	163	$manager = new Coro sub {
117	while() {	164	while () {
118	delete ((pop @destroy)->{_coro_state}) while @destroy;	165	(shift @destroy)->_cancel
		166	while @destroy;
		167
119	&schedule;	168	&schedule;
120	}	169	}
121	};	170	};
		171	$manager->desc ("[coro manager]");
		172	$manager->prio (PRIO_MAX);
122		173
123	# static methods. not really.	174	=back
124		175
125	=head2 STATIC METHODS	176	=head2 SIMPLE COROUTINE CREATION
126
127	Static methods are actually functions that operate on the current process only.
128		177
129	=over 4	178	=over 4
130		179
131	=item async { ... } [@args...]	180	=item async { ... } [@args...]
132		181
133	Create a new asynchronous process and return it's process object	182	Create a new coroutine and return it's coroutine object (usually
134	(usually unused). When the sub returns the new process is automatically	183	unused). The coroutine will be put into the ready queue, so
		184	it will start running automatically on the next scheduler run.
		185
		186	The first argument is a codeblock/closure that should be executed in the
		187	coroutine. When it returns argument returns the coroutine is automatically
135	terminated.	188	terminated.
136		189
		190	The remaining arguments are passed as arguments to the closure.
		191
		192	See the C<Coro::State::new> constructor for info about the coroutine
		193	environment in which coroutines are executed.
		194
		195	Calling C<exit> in a coroutine will do the same as calling exit outside
		196	the coroutine. Likewise, when the coroutine dies, the program will exit,
		197	just as it would in the main program.
		198
		199	If you do not want that, you can provide a default C<die> handler, or
		200	simply avoid dieing (by use of C<eval>).
		201
137	# create a new coroutine that just prints its arguments	202	Example: Create a new coroutine that just prints its arguments.
		203
138	async {	204	async {
139	print "@_\n";	205	print "@_\n";
140	} 1,2,3,4;	206	} 1,2,3,4;
141		207
142	The coderef you submit MUST NOT be a closure that refers to variables
143	in an outer scope. This does NOT work. Pass arguments into it instead.
144
145	=cut	208	=cut
146		209
147	sub async(&@) {	210	sub async(&@) {
148	my $pid = new Coro @_;	211	my $coro = new Coro @_;
149	$manager->ready; # this ensures that the stack is cloned from the manager
150	$pid->ready;	212	$coro->ready;
151	$pid;	213	$coro
152	}	214	}
		215
		216	=item async_pool { ... } [@args...]
		217
		218	Similar to C<async>, but uses a coroutine pool, so you should not call
		219	terminate or join on it (although you are allowed to), and you get a
		220	coroutine that might have executed other code already (which can be good
		221	or bad :).
		222
		223	On the plus side, this function is faster than creating (and destroying)
		224	a completely new coroutine, so if you need a lot of generic coroutines in
		225	quick successsion, use C<async_pool>, not C<async>.
		226
		227	The code block is executed in an C<eval> context and a warning will be
		228	issued in case of an exception instead of terminating the program, as
		229	C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
		230	will not work in the expected way, unless you call terminate or cancel,
		231	which somehow defeats the purpose of pooling (but is fine in the
		232	exceptional case).
		233
		234	The priority will be reset to C<0> after each run, tracing will be
		235	disabled, the description will be reset and the default output filehandle
		236	gets restored, so you can change all these. Otherwise the coroutine will
		237	be re-used "as-is": most notably if you change other per-coroutine global
		238	stuff such as C<$/> you I<must needs> to revert that change, which is most
		239	simply done by using local as in: C< local $/ >.
		240
		241	The pool size is limited to C<8> idle coroutines (this can be adjusted by
		242	changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
		243	required.
		244
		245	If you are concerned about pooled coroutines growing a lot because a
		246	single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
		247	{ terminate }> once per second or so to slowly replenish the pool. In
		248	addition to that, when the stacks used by a handler grows larger than 16kb
		249	(adjustable via $Coro::POOL_RSS) it will also be destroyed.
		250
		251	=cut
		252
		253	our $POOL_SIZE = 8;
		254	our $POOL_RSS = 16 * 1024;
		255	our @async_pool;
		256
		257	sub pool_handler {
		258	my $cb;
		259
		260	while () {
		261	eval {
		262	while () {
		263	_pool_1 $cb;
		264	&$cb;
		265	_pool_2 $cb;
		266	&schedule;
		267	}
		268	};
		269
		270	last if $@ eq "\3async_pool terminate\2\n";
		271	warn $@ if $@;
		272	}
		273	}
		274
		275	sub async_pool(&@) {
		276	# this is also inlined into the unlock_scheduler
		277	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		278
		279	$coro->{_invoke} = [@_];
		280	$coro->ready;
		281
		282	$coro
		283	}
		284
		285	=back
		286
		287	=head2 STATIC METHODS
		288
		289	Static methods are actually functions that operate on the current coroutine.
		290
		291	=over 4
153		292
154	=item schedule	293	=item schedule
155		294
156	Calls the scheduler. Please note that the current process will not be put	295	Calls the scheduler. The scheduler will find the next coroutine that is
		296	to be run from the ready queue and switches to it. The next coroutine
		297	to be run is simply the one with the highest priority that is longest
		298	in its ready queue. If there is no coroutine ready, it will clal the
		299	C<$Coro::idle> hook.
		300
		301	Please note that the current coroutine will I<not> be put into the ready
157	into the ready queue, so calling this function usually means you will	302	queue, so calling this function usually means you will never be called
158	never be called again.	303	again unless something else (e.g. an event handler) calls C<< ->ready >>,
		304	thus waking you up.
159		305
160	=cut	306	This makes C<schedule> I<the> generic method to use to block the current
		307	coroutine and wait for events: first you remember the current coroutine in
		308	a variable, then arrange for some callback of yours to call C<< ->ready
		309	>> on that once some event happens, and last you call C<schedule> to put
		310	yourself to sleep. Note that a lot of things can wake your coroutine up,
		311	so you need to check wether the event indeed happened, e.g. by storing the
		312	status in a variable.
		313
		314	The canonical way to wait on external events is this:
		315
		316	{
		317	# remember current coroutine
		318	my $current = $Coro::current;
		319
		320	# register a hypothetical event handler
		321	on_event_invoke sub {
		322	# wake up sleeping coroutine
		323	$current->ready;
		324	undef $current;
		325	};
		326
		327	# call schedule until event occurred.
		328	# in case we are woken up for other reasons
		329	# (current still defined), loop.
		330	Coro::schedule while $current;
		331	}
161		332
162	=item cede	333	=item cede
163		334
164	"Cede" to other processes. This function puts the current process into the	335	"Cede" to other coroutines. This function puts the current coroutine into
165	ready queue and calls C<schedule>, which has the effect of giving up the	336	the ready queue and calls C<schedule>, which has the effect of giving
166	current "timeslice" to other coroutines of the same or higher priority.	337	up the current "timeslice" to other coroutines of the same or higher
		338	priority. Once your coroutine gets its turn again it will automatically be
		339	resumed.
167		340
168	=cut	341	This function is often called C<yield> in other languages.
169		342
		343	=item Coro::cede_notself
		344
		345	Works like cede, but is not exported by default and will cede to I<any>
		346	coroutine, regardless of priority. This is useful sometimes to ensure
		347	progress is made.
		348
170	=item terminate	349	=item terminate [arg...]
171		350
172	Terminates the current process.	351	Terminates the current coroutine with the given status values (see L<cancel>).
173		352
174	Future versions of this function will allow result arguments.	353	=item killall
		354
		355	Kills/terminates/cancels all coroutines except the currently running
		356	one. This is useful after a fork, either in the child or the parent, as
		357	usually only one of them should inherit the running coroutines.
		358
		359	Note that while this will try to free some of the main programs resources,
		360	you cnanot free all of them, so if a coroutine that is not the main
		361	program calls this function, there will be some one-time resource leak.
175		362
176	=cut	363	=cut
177		364
178	sub terminate {	365	sub terminate {
179	$current->cancel;	366	$current->cancel (@_);
180	&schedule;	367	}
181	die; # NORETURN	368
		369	sub killall {
		370	for (Coro::State::list) {
		371	$_->cancel
		372	if $_ != $current && UNIVERSAL::isa $_, "Coro";
		373	}
182	}	374	}
183		375
184	=back	376	=back
185		377
186	# dynamic methods
187
188	=head2 PROCESS METHODS	378	=head2 COROUTINE METHODS
189		379
190	These are the methods you can call on process objects.	380	These are the methods you can call on coroutine objects (or to create
		381	them).
191		382
192	=over 4	383	=over 4
193		384
194	=item new Coro \&sub [, @args...]	385	=item new Coro \&sub [, @args...]
195		386
196	Create a new process and return it. When the sub returns the process	387	Create a new coroutine and return it. When the sub returns, the coroutine
197	automatically terminates. To start the process you must first put it into	388	automatically terminates as if C<terminate> with the returned values were
		389	called. To make the coroutine run you must first put it into the ready
198	the ready queue by calling the ready method.	390	queue by calling the ready method.
199		391
200	The coderef you submit MUST NOT be a closure that refers to variables	392	See C<async> and C<Coro::State::new> for additional info about the
201	in an outer scope. This does NOT work. Pass arguments into it instead.	393	coroutine environment.
202		394
203	=cut	395	=cut
204		396
205	sub _newcoro {	397	sub _run_coro {
206	terminate &{+shift};	398	terminate &{+shift};
207	}	399	}
208		400
209	sub new {	401	sub new {
210	my $class = shift;	402	my $class = shift;
211	bless {
212	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
213	}, $class;
214	}
215		403
216	=item $process->ready	404	$class->SUPER::new (\&_run_coro, @_)
		405	}
217		406
218	Put the current process into the ready queue.	407	=item $success = $coroutine->ready
219		408
220	=cut	409	Put the given coroutine into the end of its ready queue (there is one
		410	queue for each priority) and return true. If the coroutine is already in
		411	the ready queue, do nothing and return false.
221		412
222	=item $process->cancel	413	This ensures that the scheduler will resume this coroutine automatically
		414	once all the coroutines of higher priority and all coroutines of the same
		415	priority that were put into the ready queue earlier have been resumed.
223		416
224	Like C<terminate>, but terminates the specified process instead.	417	=item $is_ready = $coroutine->is_ready
		418
		419	Return wether the coroutine is currently the ready queue or not,
		420
		421	=item $coroutine->cancel (arg...)
		422
		423	Terminates the given coroutine and makes it return the given arguments as
		424	status (default: the empty list). Never returns if the coroutine is the
		425	current coroutine.
225		426
226	=cut	427	=cut
227		428
228	sub cancel {	429	sub cancel {
		430	my $self = shift;
		431	$self->{_status} = [@_];
		432
		433	if ($current == $self) {
229	push @destroy, $_[0];	434	push @destroy, $self;
230	$manager->ready;	435	$manager->ready;
		436	&schedule while 1;
		437	} else {
		438	$self->_cancel;
		439	}
		440	}
		441
		442	=item $coroutine->join
		443
		444	Wait until the coroutine terminates and return any values given to the
		445	C<terminate> or C<cancel> functions. C<join> can be called concurrently
		446	from multiple coroutines, and all will be resumed and given the status
		447	return once the C<$coroutine> terminates.
		448
		449	=cut
		450
		451	sub join {
		452	my $self = shift;
		453
		454	unless ($self->{_status}) {
		455	my $current = $current;
		456
		457	push @{$self->{_on_destroy}}, sub {
		458	$current->ready;
		459	undef $current;
		460	};
		461
		462	&schedule while $current;
		463	}
		464
		465	wantarray ? @{$self->{_status}} : $self->{_status}[0];
		466	}
		467
		468	=item $coroutine->on_destroy (\&cb)
		469
		470	Registers a callback that is called when this coroutine gets destroyed,
		471	but before it is joined. The callback gets passed the terminate arguments,
		472	if any, and I<must not> die, under any circumstances.
		473
		474	=cut
		475
		476	sub on_destroy {
		477	my ($self, $cb) = @_;
		478
		479	push @{ $self->{_on_destroy} }, $cb;
		480	}
		481
		482	=item $oldprio = $coroutine->prio ($newprio)
		483
		484	Sets (or gets, if the argument is missing) the priority of the
		485	coroutine. Higher priority coroutines get run before lower priority
		486	coroutines. Priorities are small signed integers (currently -4 .. +3),
		487	that you can refer to using PRIO_xxx constants (use the import tag :prio
		488	to get then):
		489
		490	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		491	3 > 1 > 0 > -1 > -3 > -4
		492
		493	# set priority to HIGH
		494	current->prio(PRIO_HIGH);
		495
		496	The idle coroutine ($Coro::idle) always has a lower priority than any
		497	existing coroutine.
		498
		499	Changing the priority of the current coroutine will take effect immediately,
		500	but changing the priority of coroutines in the ready queue (but not
		501	running) will only take effect after the next schedule (of that
		502	coroutine). This is a bug that will be fixed in some future version.
		503
		504	=item $newprio = $coroutine->nice ($change)
		505
		506	Similar to C<prio>, but subtract the given value from the priority (i.e.
		507	higher values mean lower priority, just as in unix).
		508
		509	=item $olddesc = $coroutine->desc ($newdesc)
		510
		511	Sets (or gets in case the argument is missing) the description for this
		512	coroutine. This is just a free-form string you can associate with a coroutine.
		513
		514	This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
		515	can modify this member directly if you wish.
		516
		517	=item $coroutine->throw ([$scalar])
		518
		519	If C<$throw> is specified and defined, it will be thrown as an exception
		520	inside the coroutine at the next convinient point in time (usually after
		521	it gains control at the next schedule/transfer/cede). Otherwise clears the
		522	exception object.
		523
		524	The exception object will be thrown "as is" with the specified scalar in
		525	C<$@>, i.e. if it is a string, no line number or newline will be appended
		526	(unlike with C<die>).
		527
		528	This can be used as a softer means than C<cancel> to ask a coroutine to
		529	end itself, although there is no guarentee that the exception will lead to
		530	termination, and if the exception isn't caught it might well end the whole
		531	program.
		532
		533	=cut
		534
		535	sub desc {
		536	my $old = $_[0]{desc};
		537	$_[0]{desc} = $_[1] if @_ > 1;
		538	$old;
231	}	539	}
232		540
233	=back	541	=back
234		542
		543	=head2 GLOBAL FUNCTIONS
		544
		545	=over 4
		546
		547	=item Coro::nready
		548
		549	Returns the number of coroutines that are currently in the ready state,
		550	i.e. that can be switched to by calling C<schedule> directory or
		551	indirectly. The value C<0> means that the only runnable coroutine is the
		552	currently running one, so C<cede> would have no effect, and C<schedule>
		553	would cause a deadlock unless there is an idle handler that wakes up some
		554	coroutines.
		555
		556	=item my $guard = Coro::guard { ... }
		557
		558	This creates and returns a guard object. Nothing happens until the object
		559	gets destroyed, in which case the codeblock given as argument will be
		560	executed. This is useful to free locks or other resources in case of a
		561	runtime error or when the coroutine gets canceled, as in both cases the
		562	guard block will be executed. The guard object supports only one method,
		563	C<< ->cancel >>, which will keep the codeblock from being executed.
		564
		565	Example: set some flag and clear it again when the coroutine gets canceled
		566	or the function returns:
		567
		568	sub do_something {
		569	my $guard = Coro::guard { $busy = 0 };
		570	$busy = 1;
		571
		572	# do something that requires $busy to be true
		573	}
		574
		575	=cut
		576
		577	sub guard(&) {
		578	bless \(my $cb = $_[0]), "Coro::guard"
		579	}
		580
		581	sub Coro::guard::cancel {
		582	${$_[0]} = sub { };
		583	}
		584
		585	sub Coro::guard::DESTROY {
		586	${$_[0]}->();
		587	}
		588
		589
		590	=item unblock_sub { ... }
		591
		592	This utility function takes a BLOCK or code reference and "unblocks" it,
		593	returning a new coderef. Unblocking means that calling the new coderef
		594	will return immediately without blocking, returning nothing, while the
		595	original code ref will be called (with parameters) from within another
		596	coroutine.
		597
		598	The reason this function exists is that many event libraries (such as the
		599	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
		600	of thread-safety). This means you must not block within event callbacks,
		601	otherwise you might suffer from crashes or worse. The only event library
		602	currently known that is safe to use without C<unblock_sub> is L<EV>.
		603
		604	This function allows your callbacks to block by executing them in another
		605	coroutine where it is safe to block. One example where blocking is handy
		606	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
		607	disk, for example.
		608
		609	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
		610	creating event callbacks that want to block.
		611
		612	If your handler does not plan to block (e.g. simply sends a message to
		613	another coroutine, or puts some other coroutine into the ready queue),
		614	there is no reason to use C<unblock_sub>.
		615
		616	=cut
		617
		618	our @unblock_queue;
		619
		620	# we create a special coro because we want to cede,
		621	# to reduce pressure on the coro pool (because most callbacks
		622	# return immediately and can be reused) and because we cannot cede
		623	# inside an event callback.
		624	our $unblock_scheduler = new Coro sub {
		625	while () {
		626	while (my $cb = pop @unblock_queue) {
		627	# this is an inlined copy of async_pool
		628	my $coro = (pop @async_pool) \|\| new Coro \&pool_handler;
		629
		630	$coro->{_invoke} = $cb;
		631	$coro->ready;
		632	cede; # for short-lived callbacks, this reduces pressure on the coro pool
		633	}
		634	schedule; # sleep well
		635	}
		636	};
		637	$unblock_scheduler->desc ("[unblock_sub scheduler]");
		638
		639	sub unblock_sub(&) {
		640	my $cb = shift;
		641
		642	sub {
		643	unshift @unblock_queue, [$cb, @_];
		644	$unblock_scheduler->ready;
		645	}
		646	}
		647
		648	=back
		649
235	=cut	650	=cut
236		651
237	1;	652	1;
238		653
239	=head1 BUGS/LIMITATIONS	654	=head1 BUGS/LIMITATIONS
240		655
241	- could be faster, especially when the core would introduce special	656	This module is not perl-pseudo-thread-safe. You should only ever use this
242	support for coroutines (like it does for threads).
243	- there is still a memleak on coroutine termination that I could not
244	identify. Could be as small as a single SV.
245	- this module is not well-tested.
246	- if variables or arguments "disappear" (become undef) or become
247	corrupted please contact the author so he cen iron out the
248	remaining bugs.
249	- this module is not thread-safe. You must only ever use this module from
250	the same thread (this requirement might be loosened in the future to	657	module from the same thread (this requirement might be removed in the
251	allow per-thread schedulers, but Coro::State does not yet allow this).	658	future to allow per-thread schedulers, but Coro::State does not yet allow
		659	this). I recommend disabling thread support and using processes, as this
		660	is much faster and uses less memory.
252		661
253	=head1 SEE ALSO	662	=head1 SEE ALSO
254		663
255	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,	664	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
256	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,	665
257	L<Coro::Handle>, L<Coro::Socket>.	666	Debugging: L<Coro::Debug>.
		667
		668	Support/Utility: L<Coro::Specific>, L<Coro::Util>.
		669
		670	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
		671
		672	IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
		673
		674	Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.
		675
		676	XS API: L<Coro::MakeMaker>.
		677
		678	Low level Configuration, Coroutine Environment: L<Coro::State>.
258		679
259	=head1 AUTHOR	680	=head1 AUTHOR
260		681
261	Marc Lehmann <pcg@goof.com>	682	Marc Lehmann <schmorp@schmorp.de>
262	http://www.goof.com/pcg/marc/	683	http://home.schmorp.de/
263		684
264	=cut	685	=cut
265		686

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Revision 1.181 by root, Fri May 9 22:04:37 2008 UTC