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

Comparing cvsroot/Coro/Coro.pm (file contents):
Revision 1.281 by root, Tue Dec 7 17:13:43 2010 UTC vs.
Revision 1.294 by root, Fri May 6 21:15:17 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 (see section of same name for more	45	but only the windows process emulation (see section of same name for
46	details) ported to unix, and as such act as processes), Coro provides	46	more details) ported to UNIX, and as such act as processes), Coro
47	a full shared address space, which makes communication between threads	47	provides a full shared address space, which makes communication between
48	very easy. And Coro's threads are fast, too: disabling the Windows	48	threads very easy. And coro threads are fast, too: disabling the Windows
49	process emulation code in your perl and using Coro can easily result in	49	process emulation code in your perl and using Coro can easily result in
50	a two to four times speed increase for your programs. A parallel matrix	50	a two to four times speed increase for your programs. A parallel matrix
51	multiplication benchmark runs over 300 times faster on a single core than	51	multiplication benchmark (very communication-intensive) runs over 300
52	perl's pseudo-threads on a quad core using all four cores.	52	times faster on a single core than perls pseudo-threads on a quad core
		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 >> (or C<< ->safe_cancel >>) the
		202	coro thread from another 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>
		211	without actually exiting, and might leave C libraries and XS modules in
		212	a weird state. Unlike other thread implementations, however, Coro is
		213	exceptionally safe with regards to cancellation, as perl will always be
		214	in a consistent state, and for those cases where you want to do truly
		215	marvellous things with your coro while it is being cancelled, there is
		216	even a C<< ->safe_cancel >> method.
		217
		218	So, cancelling a thread that runs in an XS event loop might not be the
		219	best idea, but any other combination that deals with perl only (cancelling
		220	when a thread is in a C<tie> method or an C<AUTOLOAD> for example) is
		221	safe.
		222
		223	=item 5. Cleanup
		224
		225	Threads will allocate various resources. Most but not all will be returned
		226	when a thread terminates, during clean-up.
		227
		228	Cleanup is quite similar to throwing an uncaught exception: perl will
		229	work it's way up through all subroutine calls and blocks. On it's way, it
		230	will release all C<my> variables, undo all C<local>'s and free any other
		231	resources truly local to the thread.
		232
		233	So, a common way to free resources is to keep them referenced only by my
		234	variables:
		235
		236	async {
		237	my $big_cache = new Cache ...;
		238	};
		239
		240	If there are no other references, then the C<$big_cache> object will be
		241	freed when the thread terminates, regardless of how it does so.
		242
		243	What it does C<NOT> do is unlock any Coro::Semaphores or similar
		244	resources, but that's where the C<guard> methods come in handy:
		245
		246	my $sem = new Coro::Semaphore;
		247
		248	async {
		249	my $lock_guard = $sem->guard;
		250	# if we reutrn, or die or get cancelled, here,
		251	# then the semaphore will be "up"ed.
		252	};
		253
		254	The C<Guard::guard> function comes in handy for any custom cleanup you
		255	might want to do:
		256
		257	async {
		258	my $window = new Gtk2::Window "toplevel";
		259	# The window will not be cleaned up automatically, even when $window
		260	# gets freed, so use a guard to ensure it's destruction
		261	# in case of an error:
		262	my $window_guard = Guard::guard { $window->destroy };
		263
		264	# we are safe here
		265	};
		266
		267	Last not least, C<local> can often be handy, too, e.g. when temporarily
		268	replacing the coro thread description:
		269
		270	sub myfunction {
		271	local $Coro::current->{desc} = "inside myfunction(@_)";
		272
		273	# if we return or die here, the description will be restored
		274	}
		275
		276	=item 6. Viva La Zombie Muerte
		277
		278	Even after a thread has terminated and cleaned up it's resources, the coro
		279	object still is there and stores the return values of the thread. Only in
		280	this state will the coro object be "reference counted" in the normal perl
		281	sense: the thread code keeps a reference to it when it is active, but not
		282	after it has terminated.
		283
		284	The means the coro object gets freed automatically when the thread has
		285	terminated and cleaned up and there arenot other references.
		286
		287	If there are, the coro object will stay around, and you can call C<<
		288	->join >> as many times as you wish to retrieve the result values:
		289
		290	async {
		291	print "hi\n";
		292	1
		293	};
		294
		295	# run the async above, and free everything before returning
		296	# from Coro::cede:
		297	Coro::cede;
		298
		299	{
		300	my $coro = async {
		301	print "hi\n";
		302	1
		303	};
		304
		305	# run the async above, and clean up, but do not free the coro
		306	# object:
		307	Coro::cede;
		308
		309	# optionally retrieve the result values
		310	my @results = $coro->join;
		311
		312	# now $coro goes out of scope, and presumably gets freed
		313	};
		314
		315	=back
		316
68	=cut	317	=cut
69		318
70	package Coro;	319	package Coro;
71		320
72	use common::sense;	321	use common::sense;
…		…
81		330
82	our $idle; # idle handler	331	our $idle; # idle handler
83	our $main; # main coro	332	our $main; # main coro
84	our $current; # current coro	333	our $current; # current coro
85		334
86	our $VERSION = 5.25;	335	our $VERSION = 5.372;
87		336
88	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);	337	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
89	our %EXPORT_TAGS = (	338	our %EXPORT_TAGS = (
90	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	339	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
91	);	340	);
…		…
131		380
132	The default implementation dies with "FATAL: deadlock detected.", followed	381	The default implementation dies with "FATAL: deadlock detected.", followed
133	by a thread listing, because the program has no other way to continue.	382	by a thread listing, because the program has no other way to continue.
134		383
135	This hook is overwritten by modules such as C<Coro::EV> and	384	This hook is overwritten by modules such as C<Coro::EV> and
136	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a	385	C<Coro::AnyEvent> to wait on an external event that hopefully wakes up a
137	coro so the scheduler can run it.	386	coro so the scheduler can run it.
138		387
139	See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.	388	See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
140		389
141	=cut	390	=cut
…		…
152	our @destroy;	401	our @destroy;
153	our $manager;	402	our $manager;
154		403
155	$manager = new Coro sub {	404	$manager = new Coro sub {
156	while () {	405	while () {
157	Coro::State::cancel shift @destroy	406	_destroy shift @destroy
158	while @destroy;	407	while @destroy;
159		408
160	&schedule;	409	&schedule;
161	}	410	}
162	};	411	};
…		…
296	coro, regardless of priority. This is useful sometimes to ensure	545	coro, regardless of priority. This is useful sometimes to ensure
297	progress is made.	546	progress is made.
298		547
299	=item terminate [arg...]	548	=item terminate [arg...]
300		549
301	Terminates the current coro with the given status values (see L<cancel>).	550	Terminates the current coro with the given status values (see
		551	L<cancel>). The values will not be copied, but referenced directly.
302		552
303	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK	553	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
304		554
305	These function install enter and leave winders in the current scope. The	555	These function install enter and leave winders in the current scope. The
306	enter block will be executed when on_enter is called and whenever the	556	enter block will be executed when on_enter is called and whenever the
…		…
480	Returns true iff this Coro object has been suspended. Suspended Coros will	730	Returns true iff this Coro object has been suspended. Suspended Coros will
481	not ever be scheduled.	731	not ever be scheduled.
482		732
483	=item $coro->cancel (arg...)	733	=item $coro->cancel (arg...)
484		734
485	Terminates the given Coro and makes it return the given arguments as	735	Terminates the given Coro thread and makes it return the given arguments as
486	status (default: the empty list). Never returns if the Coro is the	736	status (default: an empty list). Never returns if the Coro is the
487	current Coro.	737	current Coro.
488		738
489	=cut	739	This is a rather brutal way to free a coro, with some limitations - if
		740	the thread is inside a C callback that doesn't expect to be canceled,
		741	bad things can happen, or if the cancelled thread insists on running
		742	complicated cleanup handlers that rely on it'S thread context, things will
		743	not work.
490		744
491	sub cancel {	745	Sometimes it is safer to C<< ->throw >> an exception, or use C<<
492	my $self = shift;	746	->safe_cancel >>.
493		747
494	if ($current == $self) {	748	The arguments are not copied, but instead will be referenced directly
495	terminate @_;	749	(e.g. if you pass C<$var> and after the call change that variable, then
496	} else {	750	you might change the return values passed to e.g. C<join>, so don't do
497	$self->{_status} = [@_];	751	that).
498	Coro::State::cancel $self;	752
		753	The resources of the Coro are usually freed (or destructed) before this
		754	call returns, but this can be delayed for an indefinite amount of time, as
		755	in some cases the manager thread has to run first to actually destruct the
		756	Coro object.
		757
		758	=item $coro->safe_cancel ($arg...)
		759
		760	Works mostly like C<< ->cancel >>, but is inherently "safer", and
		761	consequently, can fail with an exception in cases the thread is not in a
		762	cancellable state.
		763
		764	This method works a bit like throwing an exception that cannot be caught
		765	- specifically, it will clean up the thread from within itself, so all
		766	cleanup handlers (e.g. C<guard> blocks) are run with full thread context
		767	and can block if they wish.
		768
		769	A thread is safe-cancellable if it either hasn't been run yet, or
		770	it has no C context attached and is inside an SLF function.
		771
		772	The latter two basically mean that the thread isn't currently inside a
		773	perl callback called from some C function (usually XS modules) and isn't
		774	currently inside some C function itself.
		775
		776	This call always returns true when it could cancel the thread, or croaks
		777	with an error otherwise, so you can write things like this:
		778
		779	if (! eval { $coro->safe_cancel }) {
		780	warn "unable to cancel thread: $@";
499	}	781	}
500	}
501		782
502	=item $coro->schedule_to	783	=item $coro->schedule_to
503		784
504	Puts the current coro to sleep (like C<Coro::schedule>), but instead	785	Puts the current coro to sleep (like C<Coro::schedule>), but instead
505	of continuing with the next coro from the ready queue, always switch to	786	of continuing with the next coro from the ready queue, always switch to
…		…
543		824
544	=item $coro->join	825	=item $coro->join
545		826
546	Wait until the coro terminates and return any values given to the	827	Wait until the coro terminates and return any values given to the
547	C<terminate> or C<cancel> functions. C<join> can be called concurrently	828	C<terminate> or C<cancel> functions. C<join> can be called concurrently
548	from multiple coro, and all will be resumed and given the status	829	from multiple threads, and all will be resumed and given the status
549	return once the C<$coro> terminates.	830	return once the C<$coro> terminates.
550		831
551	=cut	832	=cut
552		833
553	sub join {	834	sub join {
…		…
567	wantarray ? @{$self->{_status}} : $self->{_status}[0];	848	wantarray ? @{$self->{_status}} : $self->{_status}[0];
568	}	849	}
569		850
570	=item $coro->on_destroy (\&cb)	851	=item $coro->on_destroy (\&cb)
571		852
572	Registers a callback that is called when this coro gets destroyed,	853	Registers a callback that is called when this coro thread gets destroyed,
573	but before it is joined. The callback gets passed the terminate arguments,	854	that is, after it's resources have been freed but before it is joined. The
		855	callback gets passed the terminate/cancel arguments, if any, and I<must
574	if any, and I<must not> die, under any circumstances.	856	not> die, under any circumstances.
		857
		858	There can be any number of C<on_destroy> callbacks per coro, and there is
		859	no way currently to remove a callback once added.
575		860
576	=cut	861	=cut
577		862
578	sub on_destroy {	863	sub on_destroy {
579	my ($self, $cb) = @_;	864	my ($self, $cb) = @_;
…		…
582	}	867	}
583		868
584	=item $oldprio = $coro->prio ($newprio)	869	=item $oldprio = $coro->prio ($newprio)
585		870
586	Sets (or gets, if the argument is missing) the priority of the	871	Sets (or gets, if the argument is missing) the priority of the
587	coro. Higher priority coro get run before lower priority	872	coro thread. Higher priority coro get run before lower priority
588	coro. Priorities are small signed integers (currently -4 .. +3),	873	coros. Priorities are small signed integers (currently -4 .. +3),
589	that you can refer to using PRIO_xxx constants (use the import tag :prio	874	that you can refer to using PRIO_xxx constants (use the import tag :prio
590	to get then):	875	to get then):
591		876
592	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	877	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
593	3 > 1 > 0 > -1 > -3 > -4	878	3 > 1 > 0 > -1 > -3 > -4
594		879
595	# set priority to HIGH	880	# set priority to HIGH
596	current->prio (PRIO_HIGH);	881	current->prio (PRIO_HIGH);
597		882
598	The idle coro ($Coro::idle) always has a lower priority than any	883	The idle coro thread ($Coro::idle) always has a lower priority than any
599	existing coro.	884	existing coro.
600		885
601	Changing the priority of the current coro will take effect immediately,	886	Changing the priority of the current coro will take effect immediately,
602	but changing the priority of coro in the ready queue (but not	887	but changing the priority of a coro in the ready queue (but not running)
603	running) will only take effect after the next schedule (of that	888	will only take effect after the next schedule (of that coro). This is a
604	coro). This is a bug that will be fixed in some future version.	889	bug that will be fixed in some future version.
605		890
606	=item $newprio = $coro->nice ($change)	891	=item $newprio = $coro->nice ($change)
607		892
608	Similar to C<prio>, but subtract the given value from the priority (i.e.	893	Similar to C<prio>, but subtract the given value from the priority (i.e.
609	higher values mean lower priority, just as in unix).	894	higher values mean lower priority, just as in UNIX's nice command).
610		895
611	=item $olddesc = $coro->desc ($newdesc)	896	=item $olddesc = $coro->desc ($newdesc)
612		897
613	Sets (or gets in case the argument is missing) the description for this	898	Sets (or gets in case the argument is missing) the description for this
614	coro. This is just a free-form string you can associate with a	899	coro thread. This is just a free-form string you can associate with a
615	coro.	900	coro.
616		901
617	This method simply sets the C<< $coro->{desc} >> member to the given	902	This method simply sets the C<< $coro->{desc} >> member to the given
618	string. You can modify this member directly if you wish, and in fact, this	903	string. You can modify this member directly if you wish, and in fact, this
619	is often preferred to indicate major processing states that cna then be	904	is often preferred to indicate major processing states that cna then be
…		…
671	returning a new coderef. Unblocking means that calling the new coderef	956	returning a new coderef. Unblocking means that calling the new coderef
672	will return immediately without blocking, returning nothing, while the	957	will return immediately without blocking, returning nothing, while the
673	original code ref will be called (with parameters) from within another	958	original code ref will be called (with parameters) from within another
674	coro.	959	coro.
675		960
676	The reason this function exists is that many event libraries (such as the	961	The reason this function exists is that many event libraries (such as
677	venerable L<Event\|Event> module) are not thread-safe (a weaker form	962	the venerable L<Event\|Event> module) are not thread-safe (a weaker form
678	of reentrancy). This means you must not block within event callbacks,	963	of reentrancy). This means you must not block within event callbacks,
679	otherwise you might suffer from crashes or worse. The only event library	964	otherwise you might suffer from crashes or worse. The only event library
680	currently known that is safe to use without C<unblock_sub> is L<EV>.	965	currently known that is safe to use without C<unblock_sub> is L<EV> (but
		966	you might still run into deadlocks if all event loops are blocked).
681		967
682	Coro will try to catch you when you block in the event loop	968	Coro will try to catch you when you block in the event loop
683	("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and	969	("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and
684	only works when you do not run your own event loop.	970	only works when you do not run your own event loop.
685		971
…		…
756		1042
757	=back	1043	=back
758		1044
759	=cut	1045	=cut
760		1046
		1047	for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) {
		1048	my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"};
		1049
		1050	*{"Coro::$module\::new"} = sub {
		1051	require "Coro/$module.pm";
		1052
		1053	# some modules have their new predefined in State.xs, some don't
		1054	*{"Coro::$module\::new"} = $old
		1055	if $old;
		1056
		1057	goto &{"Coro::$module\::new"};
		1058	};
		1059	}
		1060
761	1;	1061	1;
762		1062
763	=head1 HOW TO WAIT FOR A CALLBACK	1063	=head1 HOW TO WAIT FOR A CALLBACK
764		1064
765	It is very common for a coro to wait for some callback to be	1065	It is very common for a coro to wait for some callback to be

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Comparing cvsroot/Coro/Coro.pm (file contents): Revision 1.281 by root, Tue Dec 7 17:13:43 2010 UTC vs. Revision 1.294 by root, Fri May 6 21:15:17 2011 UTC

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Comparing cvsroot/Coro/Coro.pm (file contents):
Revision 1.281 by root, Tue Dec 7 17:13:43 2010 UTC vs.
Revision 1.294 by root, Fri May 6 21:15:17 2011 UTC