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

Comparing cvsroot/Coro/Coro.pm (file contents):
Revision 1.264 by root, Thu Aug 13 02:35:41 2009 UTC vs.
Revision 1.291 by root, Fri Apr 29 15:43:26 2011 UTC

…		…
40	points in your program, so locking and parallel access are rarely an	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	41	issue, making thread programming much safer and easier than using other
42	thread models.	42	thread models.
43		43
44	Unlike the so-called "Perl threads" (which are not actually real threads	44	Unlike the so-called "Perl threads" (which are not actually real threads
45	but only the windows process emulation ported to unix, and as such act	45	but only the windows process emulation (see section of same name for
46	as processes), Coro provides a full shared address space, which makes	46	more details) ported to UNIX, and as such act as processes), Coro
47	communication between threads very easy. And Coro's threads are fast,	47	provides a full shared address space, which makes communication between
48	too: disabling the Windows process emulation code in your perl and using	48	threads very easy. And coro threads are fast, too: disabling the Windows
49	Coro can easily result in a two to four times speed increase for your	49	process emulation code in your perl and using Coro can easily result in
50	programs. A parallel matrix multiplication benchmark runs over 300 times	50	a two to four times speed increase for your programs. A parallel matrix
		51	multiplication benchmark (very communication-intensive) runs over 300
51	faster on a single core than perl's pseudo-threads on a quad core using	52	times faster on a single core than perls pseudo-threads on a quad core
52	all four cores.	53	using all four cores.
53		54
54	Coro achieves that by supporting multiple running interpreters that share	55	Coro achieves that by supporting multiple running interpreters that share
55	data, which is especially useful to code pseudo-parallel processes and	56	data, which is especially useful to code pseudo-parallel processes and
56	for event-based programming, such as multiple HTTP-GET requests running	57	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	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
…		…
63	variables (see L<Coro::State> for more configuration and background info).	64	variables (see L<Coro::State> for more configuration and background info).
64		65
65	See also the C<SEE ALSO> section at the end of this document - the Coro	66	See also the C<SEE ALSO> section at the end of this document - the Coro
66	module family is quite large.	67	module family is quite large.
67		68
		69	=head1 CORO THREAD LIFE CYCLE
		70
		71	During the long and exciting (or not) life of a coro thread, it goes
		72	through a number of states:
		73
		74	=over 4
		75
		76	=item 1. Creation
		77
		78	The first thing in the life of a coro thread is it's creation -
		79	obviously. The typical way to create a thread is to call the C<async
		80	BLOCK> function:
		81
		82	async {
		83	# thread code goes here
		84	};
		85
		86	You can also pass arguments, which are put in C<@_>:
		87
		88	async {
		89	print $_[1]; # prints 2
		90	} 1, 2, 3;
		91
		92	This creates a new coro thread and puts it into the ready queue, meaning
		93	it will run as soon as the CPU is free for it.
		94
		95	C<async> will return a coro object - you can store this for future
		96	reference or ignore it, the thread itself will keep a reference to it's
		97	thread object - threads are alive on their own.
		98
		99	Another way to create a thread is to call the C<new> constructor with a
		100	code-reference:
		101
		102	new Coro sub {
		103	# thread code goes here
		104	}, @optional_arguments;
		105
		106	This is quite similar to calling C<async>, but the important difference is
		107	that the new thread is not put into the ready queue, so the thread will
		108	not run until somebody puts it there. C<async> is, therefore, identical to
		109	this sequence:
		110
		111	my $coro = new Coro sub {
		112	# thread code goes here
		113	};
		114	$coro->ready;
		115	return $coro;
		116
		117	=item 2. Startup
		118
		119	When a new coro thread is created, only a copy of the code reference
		120	and the arguments are stored, no extra memory for stacks and so on is
		121	allocated, keeping the coro thread in a low-memory state.
		122
		123	Only when it actually starts executing will all the resources be finally
		124	allocated.
		125
		126	The optional arguments specified at coro creation are available in C<@_>,
		127	similar to function calls.
		128
		129	=item 3. Running / Blocking
		130
		131	A lot can happen after the coro thread has started running. Quite usually,
		132	it will not run to the end in one go (because you could use a function
		133	instead), but it will give up the CPU regularly because it waits for
		134	external events.
		135
		136	As long as a coro thread runs, it's coro object is available in the global
		137	variable C<$Coro::current>.
		138
		139	The low-level way to give up the CPU is to call the scheduler, which
		140	selects a new coro thread to run:
		141
		142	Coro::schedule;
		143
		144	Since running threads are not in the ready queue, calling the scheduler
		145	without doing anything else will block the coro thread forever - you need
		146	to arrange either for the coro to put woken up (readied) by some other
		147	event or some other thread, or you can put it into the ready queue before
		148	scheduling:
		149
		150	# this is exactly what Coro::cede does
		151	$Coro::current->ready;
		152	Coro::schedule;
		153
		154	All the higher-level synchronisation methods (Coro::Semaphore,
		155	Coro::rouse_*...) are actually implemented via C<< ->ready >> and C<<
		156	Coro::schedule >>.
		157
		158	While the coro thread is running it also might get assigned a C-level
		159	thread, or the C-level thread might be unassigned from it, as the Coro
		160	runtime wishes. A C-level thread needs to be assigned when your perl
		161	thread calls into some C-level function and that function in turn calls
		162	perl and perl then wants to switch coroutines. This happens most often
		163	when you run an event loop and block in the callback, or when perl
		164	itself calls some function such as C<AUTOLOAD> or methods via the C<tie>
		165	mechanism.
		166
		167	=item 4. Termination
		168
		169	Many threads actually terminate after some time. There are a number of
		170	ways to terminate a coro thread, the simplest is returning from the
		171	top-level code reference:
		172
		173	async {
		174	# after returning from here, the coro thread is terminated
		175	};
		176
		177	async {
		178	return if 0.5 < rand; # terminate a little earlier, maybe
		179	print "got a chance to print this\n";
		180	# or here
		181	};
		182
		183	Any values returned from the coroutine can be recovered using C<< ->join
		184	>>:
		185
		186	my $coro = async {
		187	"hello, world\n" # return a string
		188	};
		189
		190	my $hello_world = $coro->join;
		191
		192	print $hello_world;
		193
		194	Another way to terminate is to call C<< Coro::terminate >>, which at any
		195	subroutine call nesting level:
		196
		197	async {
		198	Coro::terminate "return value 1", "return value 2";
		199	};
		200
		201	And yet another way is to C<< ->cancel >> the coro thread from another
		202	thread:
		203
		204	my $coro = async {
		205	exit 1;
		206	};
		207
		208	$coro->cancel; # an also accept values for ->join to retrieve
		209
		210	Cancellation I<can> be dangerous - it's a bit like calling C<exit> without
		211	actually exiting, and might leave C libraries and XS modules in a weird
		212	state. Unlike other thread implementations, however, Coro is exceptionally
		213	safe with regards to cancellation, as perl will always be in a consistent
		214	state.
		215
		216	So, cancelling a thread that runs in an XS event loop might not be the
		217	best idea, but any other combination that deals with perl only (cancelling
		218	when a thread is in a C<tie> method or an C<AUTOLOAD> for example) is
		219	safe.
		220
		221	=item 5. Cleanup
		222
		223	Threads will allocate various resources. Most but not all will be returned
		224	when a thread terminates, during clean-up.
		225
		226	Cleanup is quite similar to throwing an uncaught exception: perl will
		227	work it's way up through all subroutine calls and blocks. On it's way, it
		228	will release all C<my> variables, undo all C<local>'s and free any other
		229	resources truly local to the thread.
		230
		231	So, a common way to free resources is to keep them referenced only by my
		232	variables:
		233
		234	async {
		235	my $big_cache = new Cache ...;
		236	};
		237
		238	If there are no other references, then the C<$big_cache> object will be
		239	freed when the thread terminates, regardless of how it does so.
		240
		241	What it does C<NOT> do is unlock any Coro::Semaphores or similar
		242	resources, but that's where the C<guard> methods come in handy:
		243
		244	my $sem = new Coro::Semaphore;
		245
		246	async {
		247	my $lock_guard = $sem->guard;
		248	# if we reutrn, or die or get cancelled, here,
		249	# then the semaphore will be "up"ed.
		250	};
		251
		252	The C<Guard::guard> function comes in handy for any custom cleanup you
		253	might want to do:
		254
		255	async {
		256	my $window = new Gtk2::Window "toplevel";
		257	# The window will not be cleaned up automatically, even when $window
		258	# gets freed, so use a guard to ensure it's destruction
		259	# in case of an error:
		260	my $window_guard = Guard::guard { $window->destroy };
		261
		262	# we are safe here
		263	};
		264
		265	Last not least, C<local> can often be handy, too, e.g. when temporarily
		266	replacing the coro thread description:
		267
		268	sub myfunction {
		269	local $Coro::current->{desc} = "inside myfunction(@_)";
		270
		271	# if we return or die here, the description will be restored
		272	}
		273
		274	=item 6. Viva La Zombie Muerte
		275
		276	Even after a thread has terminated and cleaned up it's resources, the coro
		277	object still is there and stores the return values of the thread. Only in
		278	this state will the coro object be "reference counted" in the normal perl
		279	sense: the thread code keeps a reference to it when it is active, but not
		280	after it has terminated.
		281
		282	The means the coro object gets freed automatically when the thread has
		283	terminated and cleaned up and there arenot other references.
		284
		285	If there are, the coro object will stay around, and you can call C<<
		286	->join >> as many times as you wish to retrieve the result values:
		287
		288	async {
		289	print "hi\n";
		290	1
		291	};
		292
		293	# run the async above, and free everything before returning
		294	# from Coro::cede:
		295	Coro::cede;
		296
		297	{
		298	my $coro = async {
		299	print "hi\n";
		300	1
		301	};
		302
		303	# run the async above, and clean up, but do not free the coro
		304	# object:
		305	Coro::cede;
		306
		307	# optionally retrieve the result values
		308	my @results = $coro->join;
		309
		310	# now $coro goes out of scope, and presumably gets freed
		311	};
		312
		313	=back
		314
68	=cut	315	=cut
69		316
70	package Coro;	317	package Coro;
71		318
72	use strict qw(vars subs);	319	use common::sense;
73	no warnings "uninitialized";	320
		321	use Carp ();
74		322
75	use Guard ();	323	use Guard ();
76		324
77	use Coro::State;	325	use Coro::State;
78		326
…		…
80		328
81	our $idle; # idle handler	329	our $idle; # idle handler
82	our $main; # main coro	330	our $main; # main coro
83	our $current; # current coro	331	our $current; # current coro
84		332
85	our $VERSION = 5.162;	333	our $VERSION = 5.372;
86		334
87	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	335	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
88	our %EXPORT_TAGS = (	336	our %EXPORT_TAGS = (
89	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	337	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
90	);	338	);
91	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	339	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
92		340
…		…
123		371
124	This variable is mainly useful to integrate Coro into event loops. It is	372	This variable is mainly useful to integrate Coro into event loops. It is
125	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is	373	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
126	pretty low-level functionality.	374	pretty low-level functionality.
127		375
128	This variable stores either a Coro object or a callback.	376	This variable stores a Coro object that is put into the ready queue when
		377	there are no other ready threads (without invoking any ready hooks).
129		378
130	If it is a callback, the it is called whenever the scheduler finds no	379	The default implementation dies with "FATAL: deadlock detected.", followed
131	ready coros to run. The default implementation prints "FATAL:	380	by a thread listing, because the program has no other way to continue.
132	deadlock detected" and exits, because the program has no other way to
133	continue.
134
135	If it is a coro object, then this object will be readied (without
136	invoking any ready hooks, however) when the scheduler finds no other ready
137	coros to run.
138		381
139	This hook is overwritten by modules such as C<Coro::EV> and	382	This hook is overwritten by modules such as C<Coro::EV> and
140	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a	383	C<Coro::AnyEvent> to wait on an external event that hopefully wakes up a
141	coro so the scheduler can run it.	384	coro so the scheduler can run it.
142		385
143	Note that the callback I<must not>, under any circumstances, block
144	the current coro. Normally, this is achieved by having an "idle
145	coro" that calls the event loop and then blocks again, and then
146	readying that coro in the idle handler, or by simply placing the idle
147	coro in this variable.
148
149	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this	386	See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
150	technique.
151		387
152	Please note that if your callback recursively invokes perl (e.g. for event
153	handlers), then it must be prepared to be called recursively itself.
154
155	=cut	388	=cut
156		389
157	$idle = sub {	390	# \|\|= because other modules could have provided their own by now
158	require Carp;	391	$idle \|\|= new Coro sub {
159	Carp::croak ("FATAL: deadlock detected");	392	require Coro::Debug;
		393	die "FATAL: deadlock detected.\n"
		394	. Coro::Debug::ps_listing ();
160	};	395	};
161		396
162	# this coro is necessary because a coro	397	# this coro is necessary because a coro
163	# cannot destroy itself.	398	# cannot destroy itself.
164	our @destroy;	399	our @destroy;
165	our $manager;	400	our $manager;
166		401
167	$manager = new Coro sub {	402	$manager = new Coro sub {
168	while () {	403	while () {
169	Coro::State::cancel shift @destroy	404	_destroy shift @destroy
170	while @destroy;	405	while @destroy;
171		406
172	&schedule;	407	&schedule;
173	}	408	}
174	};	409	};
…		…
272	=item schedule	507	=item schedule
273		508
274	Calls the scheduler. The scheduler will find the next coro that is	509	Calls the scheduler. The scheduler will find the next coro that is
275	to be run from the ready queue and switches to it. The next coro	510	to be run from the ready queue and switches to it. The next coro
276	to be run is simply the one with the highest priority that is longest	511	to be run is simply the one with the highest priority that is longest
277	in its ready queue. If there is no coro ready, it will clal the	512	in its ready queue. If there is no coro ready, it will call the
278	C<$Coro::idle> hook.	513	C<$Coro::idle> hook.
279		514
280	Please note that the current coro will I<not> be put into the ready	515	Please note that the current coro will I<not> be put into the ready
281	queue, so calling this function usually means you will never be called	516	queue, so calling this function usually means you will never be called
282	again unless something else (e.g. an event handler) calls C<< ->ready >>,	517	again unless something else (e.g. an event handler) calls C<< ->ready >>,
…		…
308	coro, regardless of priority. This is useful sometimes to ensure	543	coro, regardless of priority. This is useful sometimes to ensure
309	progress is made.	544	progress is made.
310		545
311	=item terminate [arg...]	546	=item terminate [arg...]
312		547
313	Terminates the current coro with the given status values (see L<cancel>).	548	Terminates the current coro with the given status values (see
		549	L<cancel>). The values will not be copied, but referenced directly.
314		550
315	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK	551	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
316		552
317	These function install enter and leave winders in the current scope. The	553	These function install enter and leave winders in the current scope. The
318	enter block will be executed when on_enter is called and whenever the	554	enter block will be executed when on_enter is called and whenever the
…		…
492	Returns true iff this Coro object has been suspended. Suspended Coros will	728	Returns true iff this Coro object has been suspended. Suspended Coros will
493	not ever be scheduled.	729	not ever be scheduled.
494		730
495	=item $coro->cancel (arg...)	731	=item $coro->cancel (arg...)
496		732
497	Terminates the given Coro and makes it return the given arguments as	733	Terminates the given Coro object and makes it return the given arguments as
498	status (default: the empty list). Never returns if the Coro is the	734	status (default: an empty list). Never returns if the Coro is the
499	current Coro.	735	current Coro.
500		736
501	=cut	737	The arguments are not copied, but instead will be referenced directly
		738	(e.g. if you pass C<$var> and after the call change that variable, then
		739	you might change the return values passed to e.g. C<join>, so don't do
		740	that).
502		741
503	sub cancel {	742	The resources of the Coro are usually freed (or destructed) before this
504	my $self = shift;	743	call returns, but this can be delayed for an indefinite amount of time, as
505		744	in some cases the manager thread has to run first to actually destruct the
506	if ($current == $self) {	745	Coro object.
507	terminate @_;
508	} else {
509	$self->{_status} = [@_];
510	Coro::State::cancel $self;
511	}
512	}
513		746
514	=item $coro->schedule_to	747	=item $coro->schedule_to
515		748
516	Puts the current coro to sleep (like C<Coro::schedule>), but instead	749	Puts the current coro to sleep (like C<Coro::schedule>), but instead
517	of continuing with the next coro from the ready queue, always switch to	750	of continuing with the next coro from the ready queue, always switch to
…		…
579	wantarray ? @{$self->{_status}} : $self->{_status}[0];	812	wantarray ? @{$self->{_status}} : $self->{_status}[0];
580	}	813	}
581		814
582	=item $coro->on_destroy (\&cb)	815	=item $coro->on_destroy (\&cb)
583		816
584	Registers a callback that is called when this coro gets destroyed,	817	Registers a callback that is called when this coro thread gets destroyed,
585	but before it is joined. The callback gets passed the terminate arguments,	818	but before it is joined. The callback gets passed the terminate arguments,
586	if any, and I<must not> die, under any circumstances.	819	if any, and I<must not> die, under any circumstances.
587		820
		821	There can be any number of C<on_destroy> callbacks per coro.
		822
588	=cut	823	=cut
589		824
590	sub on_destroy {	825	sub on_destroy {
591	my ($self, $cb) = @_;	826	my ($self, $cb) = @_;
592		827
…		…
594	}	829	}
595		830
596	=item $oldprio = $coro->prio ($newprio)	831	=item $oldprio = $coro->prio ($newprio)
597		832
598	Sets (or gets, if the argument is missing) the priority of the	833	Sets (or gets, if the argument is missing) the priority of the
599	coro. Higher priority coro get run before lower priority	834	coro thread. Higher priority coro get run before lower priority
600	coro. Priorities are small signed integers (currently -4 .. +3),	835	coros. Priorities are small signed integers (currently -4 .. +3),
601	that you can refer to using PRIO_xxx constants (use the import tag :prio	836	that you can refer to using PRIO_xxx constants (use the import tag :prio
602	to get then):	837	to get then):
603		838
604	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	839	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
605	3 > 1 > 0 > -1 > -3 > -4	840	3 > 1 > 0 > -1 > -3 > -4
606		841
607	# set priority to HIGH	842	# set priority to HIGH
608	current->prio (PRIO_HIGH);	843	current->prio (PRIO_HIGH);
609		844
610	The idle coro ($Coro::idle) always has a lower priority than any	845	The idle coro thread ($Coro::idle) always has a lower priority than any
611	existing coro.	846	existing coro.
612		847
613	Changing the priority of the current coro will take effect immediately,	848	Changing the priority of the current coro will take effect immediately,
614	but changing the priority of coro in the ready queue (but not	849	but changing the priority of a coro in the ready queue (but not running)
615	running) will only take effect after the next schedule (of that	850	will only take effect after the next schedule (of that coro). This is a
616	coro). This is a bug that will be fixed in some future version.	851	bug that will be fixed in some future version.
617		852
618	=item $newprio = $coro->nice ($change)	853	=item $newprio = $coro->nice ($change)
619		854
620	Similar to C<prio>, but subtract the given value from the priority (i.e.	855	Similar to C<prio>, but subtract the given value from the priority (i.e.
621	higher values mean lower priority, just as in unix).	856	higher values mean lower priority, just as in UNIX's nice command).
622		857
623	=item $olddesc = $coro->desc ($newdesc)	858	=item $olddesc = $coro->desc ($newdesc)
624		859
625	Sets (or gets in case the argument is missing) the description for this	860	Sets (or gets in case the argument is missing) the description for this
626	coro. This is just a free-form string you can associate with a	861	coro thread. This is just a free-form string you can associate with a
627	coro.	862	coro.
628		863
629	This method simply sets the C<< $coro->{desc} >> member to the given	864	This method simply sets the C<< $coro->{desc} >> member to the given
630	string. You can modify this member directly if you wish.	865	string. You can modify this member directly if you wish, and in fact, this
		866	is often preferred to indicate major processing states that cna then be
		867	seen for example in a L<Coro::Debug> session:
		868
		869	sub my_long_function {
		870	local $Coro::current->{desc} = "now in my_long_function";
		871	...
		872	$Coro::current->{desc} = "my_long_function: phase 1";
		873	...
		874	$Coro::current->{desc} = "my_long_function: phase 2";
		875	...
		876	}
631		877
632	=cut	878	=cut
633		879
634	sub desc {	880	sub desc {
635	my $old = $_[0]{desc};	881	my $old = $_[0]{desc};
…		…
672	returning a new coderef. Unblocking means that calling the new coderef	918	returning a new coderef. Unblocking means that calling the new coderef
673	will return immediately without blocking, returning nothing, while the	919	will return immediately without blocking, returning nothing, while the
674	original code ref will be called (with parameters) from within another	920	original code ref will be called (with parameters) from within another
675	coro.	921	coro.
676		922
677	The reason this function exists is that many event libraries (such as the	923	The reason this function exists is that many event libraries (such as
678	venerable L<Event\|Event> module) are not thread-safe (a weaker form	924	the venerable L<Event\|Event> module) are not thread-safe (a weaker form
679	of reentrancy). This means you must not block within event callbacks,	925	of reentrancy). This means you must not block within event callbacks,
680	otherwise you might suffer from crashes or worse. The only event library	926	otherwise you might suffer from crashes or worse. The only event library
681	currently known that is safe to use without C<unblock_sub> is L<EV>.	927	currently known that is safe to use without C<unblock_sub> is L<EV> (but
		928	you might still run into deadlocks if all event loops are blocked).
		929
		930	Coro will try to catch you when you block in the event loop
		931	("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and
		932	only works when you do not run your own event loop.
682		933
683	This function allows your callbacks to block by executing them in another	934	This function allows your callbacks to block by executing them in another
684	coro where it is safe to block. One example where blocking is handy	935	coro where it is safe to block. One example where blocking is handy
685	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	936	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
686	disk, for example.	937	disk, for example.
…		…
728	unshift @unblock_queue, [$cb, @_];	979	unshift @unblock_queue, [$cb, @_];
729	$unblock_scheduler->ready;	980	$unblock_scheduler->ready;
730	}	981	}
731	}	982	}
732		983
733	=item $cb = Coro::rouse_cb	984	=item $cb = rouse_cb
734		985
735	Create and return a "rouse callback". That's a code reference that,	986	Create and return a "rouse callback". That's a code reference that,
736	when called, will remember a copy of its arguments and notify the owner	987	when called, will remember a copy of its arguments and notify the owner
737	coro of the callback.	988	coro of the callback.
738		989
739	See the next function.	990	See the next function.
740		991
741	=item @args = Coro::rouse_wait [$cb]	992	=item @args = rouse_wait [$cb]
742		993
743	Wait for the specified rouse callback (or the last one that was created in	994	Wait for the specified rouse callback (or the last one that was created in
744	this coro).	995	this coro).
745		996
746	As soon as the callback is invoked (or when the callback was invoked	997	As soon as the callback is invoked (or when the callback was invoked
…		…
752	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.	1003	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
753		1004
754	=back	1005	=back
755		1006
756	=cut	1007	=cut
		1008
		1009	for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) {
		1010	my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"};
		1011
		1012	*{"Coro::$module\::new"} = sub {
		1013	require "Coro/$module.pm";
		1014
		1015	# some modules have their new predefined in State.xs, some don't
		1016	*{"Coro::$module\::new"} = $old
		1017	if $old;
		1018
		1019	goto &{"Coro::$module\::new"};
		1020	};
		1021	}
757		1022
758	1;	1023	1;
759		1024
760	=head1 HOW TO WAIT FOR A CALLBACK	1025	=head1 HOW TO WAIT FOR A CALLBACK
761		1026
…		…
843	the windows process emulation enabled under unix roughly halves perl	1108	the windows process emulation enabled under unix roughly halves perl
844	performance, even when not used.	1109	performance, even when not used.
845		1110
846	=item coro switching is not signal safe	1111	=item coro switching is not signal safe
847		1112
848	You must not switch to another coro from within a signal handler	1113	You must not switch to another coro from within a signal handler (only
849	(only relevant with %SIG - most event libraries provide safe signals).	1114	relevant with %SIG - most event libraries provide safe signals), I<unless>
		1115	you are sure you are not interrupting a Coro function.
850		1116
851	That means you I<MUST NOT> call any function that might "block" the	1117	That means you I<MUST NOT> call any function that might "block" the
852	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or	1118	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
853	anything that calls those. Everything else, including calling C<ready>,	1119	anything that calls those. Everything else, including calling C<ready>,
854	works.	1120	works.
855		1121
856	=back	1122	=back
857		1123
858		1124
		1125	=head1 WINDOWS PROCESS EMULATION
		1126
		1127	A great many people seem to be confused about ithreads (for example, Chip
		1128	Salzenberg called me unintelligent, incapable, stupid and gullible,
		1129	while in the same mail making rather confused statements about perl
		1130	ithreads (for example, that memory or files would be shared), showing his
		1131	lack of understanding of this area - if it is hard to understand for Chip,
		1132	it is probably not obvious to everybody).
		1133
		1134	What follows is an ultra-condensed version of my talk about threads in
		1135	scripting languages given on the perl workshop 2009:
		1136
		1137	The so-called "ithreads" were originally implemented for two reasons:
		1138	first, to (badly) emulate unix processes on native win32 perls, and
		1139	secondly, to replace the older, real thread model ("5.005-threads").
		1140
		1141	It does that by using threads instead of OS processes. The difference
		1142	between processes and threads is that threads share memory (and other
		1143	state, such as files) between threads within a single process, while
		1144	processes do not share anything (at least not semantically). That
		1145	means that modifications done by one thread are seen by others, while
		1146	modifications by one process are not seen by other processes.
		1147
		1148	The "ithreads" work exactly like that: when creating a new ithreads
		1149	process, all state is copied (memory is copied physically, files and code
		1150	is copied logically). Afterwards, it isolates all modifications. On UNIX,
		1151	the same behaviour can be achieved by using operating system processes,
		1152	except that UNIX typically uses hardware built into the system to do this
		1153	efficiently, while the windows process emulation emulates this hardware in
		1154	software (rather efficiently, but of course it is still much slower than
		1155	dedicated hardware).
		1156
		1157	As mentioned before, loading code, modifying code, modifying data
		1158	structures and so on is only visible in the ithreads process doing the
		1159	modification, not in other ithread processes within the same OS process.
		1160
		1161	This is why "ithreads" do not implement threads for perl at all, only
		1162	processes. What makes it so bad is that on non-windows platforms, you can
		1163	actually take advantage of custom hardware for this purpose (as evidenced
		1164	by the forks module, which gives you the (i-) threads API, just much
		1165	faster).
		1166
		1167	Sharing data is in the i-threads model is done by transfering data
		1168	structures between threads using copying semantics, which is very slow -
		1169	shared data simply does not exist. Benchmarks using i-threads which are
		1170	communication-intensive show extremely bad behaviour with i-threads (in
		1171	fact, so bad that Coro, which cannot take direct advantage of multiple
		1172	CPUs, is often orders of magnitude faster because it shares data using
		1173	real threads, refer to my talk for details).
		1174
		1175	As summary, i-threads use threads to implement processes, while
		1176	the compatible forks module uses processes to emulate, uhm,
		1177	processes. I-threads slow down every perl program when enabled, and
		1178	outside of windows, serve no (or little) practical purpose, but
		1179	disadvantages every single-threaded Perl program.
		1180
		1181	This is the reason that I try to avoid the name "ithreads", as it is
		1182	misleading as it implies that it implements some kind of thread model for
		1183	perl, and prefer the name "windows process emulation", which describes the
		1184	actual use and behaviour of it much better.
		1185
859	=head1 SEE ALSO	1186	=head1 SEE ALSO
860		1187
861	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.	1188	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
862		1189
863	Debugging: L<Coro::Debug>.	1190	Debugging: L<Coro::Debug>.

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Comparing cvsroot/Coro/Coro.pm (file contents): Revision 1.264 by root, Thu Aug 13 02:35:41 2009 UTC vs. Revision 1.291 by root, Fri Apr 29 15:43:26 2011 UTC

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Comparing cvsroot/Coro/Coro.pm (file contents):
Revision 1.264 by root, Thu Aug 13 02:35:41 2009 UTC vs.
Revision 1.291 by root, Fri Apr 29 15:43:26 2011 UTC