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

Comparing Coro/Coro.pm (file contents):
Revision 1.260 by root, Mon Jul 6 03:42:29 2009 UTC vs.
Revision 1.321 by root, Sun Feb 2 03:26:06 2014 UTC

…		…
16	cede; # yield to coro	16	cede; # yield to coro
17	print "3\n";	17	print "3\n";
18	cede; # and again	18	cede; # and again
19		19
20	# use locking	20	# use locking
21	use Coro::Semaphore;
22	my $lock = new Coro::Semaphore;	21	my $lock = new Coro::Semaphore;
23	my $locked;	22	my $locked;
24		23
25	$lock->down;	24	$lock->down;
26	$locked = 1;	25	$locked = 1;
…		…
40	points in your program, so locking and parallel access are rarely an	39	points in your program, so locking and parallel access are rarely an
41	issue, making thread programming much safer and easier than using other	40	issue, making thread programming much safer and easier than using other
42	thread models.	41	thread models.
43		42
44	Unlike the so-called "Perl threads" (which are not actually real threads	43	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	44	but only the windows process emulation (see section of same name for
46	as processes), Coro provides a full shared address space, which makes	45	more details) ported to UNIX, and as such act as processes), Coro
47	communication between threads very easy. And Coro's threads are fast,	46	provides a full shared address space, which makes communication between
48	too: disabling the Windows process emulation code in your perl and using	47	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	48	process emulation code in your perl and using Coro can easily result in
50	programs. A parallel matrix multiplication benchmark runs over 300 times	49	a two to four times speed increase for your programs. A parallel matrix
		50	multiplication benchmark (very communication-intensive) runs over 300
51	faster on a single core than perl's pseudo-threads on a quad core using	51	times faster on a single core than perls pseudo-threads on a quad core
52	all four cores.	52	using all four cores.
53		53
54	Coro achieves that by supporting multiple running interpreters that share	54	Coro achieves that by supporting multiple running interpreters that share
55	data, which is especially useful to code pseudo-parallel processes and	55	data, which is especially useful to code pseudo-parallel processes and
56	for event-based programming, such as multiple HTTP-GET requests running	56	for event-based programming, such as multiple HTTP-GET requests running
57	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro	57	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).	63	variables (see L<Coro::State> for more configuration and background info).
64		64
65	See also the C<SEE ALSO> section at the end of this document - the Coro	65	See also the C<SEE ALSO> section at the end of this document - the Coro
66	module family is quite large.	66	module family is quite large.
67		67
		68	=head1 CORO THREAD LIFE CYCLE
		69
		70	During the long and exciting (or not) life of a coro thread, it goes
		71	through a number of states:
		72
		73	=over 4
		74
		75	=item 1. Creation
		76
		77	The first thing in the life of a coro thread is it's creation -
		78	obviously. The typical way to create a thread is to call the C<async
		79	BLOCK> function:
		80
		81	async {
		82	# thread code goes here
		83	};
		84
		85	You can also pass arguments, which are put in C<@_>:
		86
		87	async {
		88	print $_[1]; # prints 2
		89	} 1, 2, 3;
		90
		91	This creates a new coro thread and puts it into the ready queue, meaning
		92	it will run as soon as the CPU is free for it.
		93
		94	C<async> will return a Coro object - you can store this for future
		95	reference or ignore it - a thread that is running, ready to run or waiting
		96	for some event is alive on it's own.
		97
		98	Another way to create a thread is to call the C<new> constructor with a
		99	code-reference:
		100
		101	new Coro sub {
		102	# thread code goes here
		103	}, @optional_arguments;
		104
		105	This is quite similar to calling C<async>, but the important difference is
		106	that the new thread is not put into the ready queue, so the thread will
		107	not run until somebody puts it there. C<async> is, therefore, identical to
		108	this sequence:
		109
		110	my $coro = new Coro sub {
		111	# thread code goes here
		112	};
		113	$coro->ready;
		114	return $coro;
		115
		116	=item 2. Startup
		117
		118	When a new coro thread is created, only a copy of the code reference
		119	and the arguments are stored, no extra memory for stacks and so on is
		120	allocated, keeping the coro thread in a low-memory state.
		121
		122	Only when it actually starts executing will all the resources be finally
		123	allocated.
		124
		125	The optional arguments specified at coro creation are available in C<@_>,
		126	similar to function calls.
		127
		128	=item 3. Running / Blocking
		129
		130	A lot can happen after the coro thread has started running. Quite usually,
		131	it will not run to the end in one go (because you could use a function
		132	instead), but it will give up the CPU regularly because it waits for
		133	external events.
		134
		135	As long as a coro thread runs, its Coro object is available in the global
		136	variable C<$Coro::current>.
		137
		138	The low-level way to give up the CPU is to call the scheduler, which
		139	selects a new coro thread to run:
		140
		141	Coro::schedule;
		142
		143	Since running threads are not in the ready queue, calling the scheduler
		144	without doing anything else will block the coro thread forever - you need
		145	to arrange either for the coro to put woken up (readied) by some other
		146	event or some other thread, or you can put it into the ready queue before
		147	scheduling:
		148
		149	# this is exactly what Coro::cede does
		150	$Coro::current->ready;
		151	Coro::schedule;
		152
		153	All the higher-level synchronisation methods (Coro::Semaphore,
		154	Coro::rouse_*...) are actually implemented via C<< ->ready >> and C<<
		155	Coro::schedule >>.
		156
		157	While the coro thread is running it also might get assigned a C-level
		158	thread, or the C-level thread might be unassigned from it, as the Coro
		159	runtime wishes. A C-level thread needs to be assigned when your perl
		160	thread calls into some C-level function and that function in turn calls
		161	perl and perl then wants to switch coroutines. This happens most often
		162	when you run an event loop and block in the callback, or when perl
		163	itself calls some function such as C<AUTOLOAD> or methods via the C<tie>
		164	mechanism.
		165
		166	=item 4. Termination
		167
		168	Many threads actually terminate after some time. There are a number of
		169	ways to terminate a coro thread, the simplest is returning from the
		170	top-level code reference:
		171
		172	async {
		173	# after returning from here, the coro thread is terminated
		174	};
		175
		176	async {
		177	return if 0.5 < rand; # terminate a little earlier, maybe
		178	print "got a chance to print this\n";
		179	# or here
		180	};
		181
		182	Any values returned from the coroutine can be recovered using C<< ->join
		183	>>:
		184
		185	my $coro = async {
		186	"hello, world\n" # return a string
		187	};
		188
		189	my $hello_world = $coro->join;
		190
		191	print $hello_world;
		192
		193	Another way to terminate is to call C<< Coro::terminate >>, which at any
		194	subroutine call nesting level:
		195
		196	async {
		197	Coro::terminate "return value 1", "return value 2";
		198	};
		199
		200	Yet another way is to C<< ->cancel >> (or C<< ->safe_cancel >>) the coro
		201	thread from another thread:
		202
		203	my $coro = async {
		204	exit 1;
		205	};
		206
		207	$coro->cancel; # also accepts values for ->join to retrieve
		208
		209	Cancellation I<can> be dangerous - it's a bit like calling C<exit> without
		210	actually exiting, and might leave C libraries and XS modules in a weird
		211	state. Unlike other thread implementations, however, Coro is exceptionally
		212	safe with regards to cancellation, as perl will always be in a consistent
		213	state, and for those cases where you want to do truly marvellous things
		214	with your coro while it is being cancelled - that is, make sure all
		215	cleanup code is executed from the thread being cancelled - there is even a
		216	C<< ->safe_cancel >> method.
		217
		218	So, cancelling a thread that runs in an XS event loop might not be the
		219	best idea, but any other combination that deals with perl only (cancelling
		220	when a thread is in a C<tie> method or an C<AUTOLOAD> for example) is
		221	safe.
		222
		223	Last not least, a coro thread object that isn't referenced is C<<
		224	->cancel >>'ed automatically - just like other objects in Perl. This
		225	is not such a common case, however - a running thread is referencedy by
		226	C<$Coro::current>, a thread ready to run is referenced by the ready queue,
		227	a thread waiting on a lock or semaphore is referenced by being in some
		228	wait list and so on. But a thread that isn't in any of those queues gets
		229	cancelled:
		230
		231	async {
		232	schedule; # cede to other coros, don't go into the ready queue
		233	};
		234
		235	cede;
		236	# now the async above is destroyed, as it is not referenced by anything.
		237
		238	A slightly embellished example might make it clearer:
		239
		240	async {
		241	my $guard = Guard::guard { print "destroyed\n" };
		242	schedule while 1;
		243	};
		244
		245	cede;
		246
		247	Superficially one might not expect any output - since the C<async>
		248	implements an endless loop, the C<$guard> will not be cleaned up. However,
		249	since the thread object returned by C<async> is not stored anywhere, the
		250	thread is initially referenced because it is in the ready queue, when it
		251	runs it is referenced by C<$Coro::current>, but when it calls C<schedule>,
		252	it gets C<cancel>ed causing the guard object to be destroyed (see the next
		253	section), and printing it's message.
		254
		255	If this seems a bit drastic, remember that this only happens when nothing
		256	references the thread anymore, which means there is no way to further
		257	execute it, ever. The only options at this point are leaking the thread,
		258	or cleaning it up, which brings us to...
		259
		260	=item 5. Cleanup
		261
		262	Threads will allocate various resources. Most but not all will be returned
		263	when a thread terminates, during clean-up.
		264
		265	Cleanup is quite similar to throwing an uncaught exception: perl will
		266	work it's way up through all subroutine calls and blocks. On it's way, it
		267	will release all C<my> variables, undo all C<local>'s and free any other
		268	resources truly local to the thread.
		269
		270	So, a common way to free resources is to keep them referenced only by my
		271	variables:
		272
		273	async {
		274	my $big_cache = new Cache ...;
		275	};
		276
		277	If there are no other references, then the C<$big_cache> object will be
		278	freed when the thread terminates, regardless of how it does so.
		279
		280	What it does C<NOT> do is unlock any Coro::Semaphores or similar
		281	resources, but that's where the C<guard> methods come in handy:
		282
		283	my $sem = new Coro::Semaphore;
		284
		285	async {
		286	my $lock_guard = $sem->guard;
		287	# if we return, or die or get cancelled, here,
		288	# then the semaphore will be "up"ed.
		289	};
		290
		291	The C<Guard::guard> function comes in handy for any custom cleanup you
		292	might want to do (but you cannot switch to other coroutines from those
		293	code blocks):
		294
		295	async {
		296	my $window = new Gtk2::Window "toplevel";
		297	# The window will not be cleaned up automatically, even when $window
		298	# gets freed, so use a guard to ensure it's destruction
		299	# in case of an error:
		300	my $window_guard = Guard::guard { $window->destroy };
		301
		302	# we are safe here
		303	};
		304
		305	Last not least, C<local> can often be handy, too, e.g. when temporarily
		306	replacing the coro thread description:
		307
		308	sub myfunction {
		309	local $Coro::current->{desc} = "inside myfunction(@_)";
		310
		311	# if we return or die here, the description will be restored
		312	}
		313
		314	=item 6. Viva La Zombie Muerte
		315
		316	Even after a thread has terminated and cleaned up its resources, the Coro
		317	object still is there and stores the return values of the thread.
		318
		319	When there are no other references, it will simply be cleaned up and
		320	freed.
		321
		322	If there areany references, the Coro object will stay around, and you
		323	can call C<< ->join >> as many times as you wish to retrieve the result
		324	values:
		325
		326	async {
		327	print "hi\n";
		328	1
		329	};
		330
		331	# run the async above, and free everything before returning
		332	# from Coro::cede:
		333	Coro::cede;
		334
		335	{
		336	my $coro = async {
		337	print "hi\n";
		338	1
		339	};
		340
		341	# run the async above, and clean up, but do not free the coro
		342	# object:
		343	Coro::cede;
		344
		345	# optionally retrieve the result values
		346	my @results = $coro->join;
		347
		348	# now $coro goes out of scope, and presumably gets freed
		349	};
		350
		351	=back
		352
68	=cut	353	=cut
69		354
70	package Coro;	355	package Coro;
71		356
72	use strict qw(vars subs);	357	use common::sense;
73	no warnings "uninitialized";	358
		359	use Carp ();
74		360
75	use Guard ();	361	use Guard ();
76		362
77	use Coro::State;	363	use Coro::State;
78		364
…		…
80		366
81	our $idle; # idle handler	367	our $idle; # idle handler
82	our $main; # main coro	368	our $main; # main coro
83	our $current; # current coro	369	our $current; # current coro
84		370
85	our $VERSION = 5.151;	371	our $VERSION = 6.33;
86		372
87	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	373	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
88	our %EXPORT_TAGS = (	374	our %EXPORT_TAGS = (
89	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	375	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
90	);	376	);
91	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	377	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
92		378
…		…
95	=over 4	381	=over 4
96		382
97	=item $Coro::main	383	=item $Coro::main
98		384
99	This variable stores the Coro object that represents the main	385	This variable stores the Coro object that represents the main
100	program. While you cna C<ready> it and do most other things you can do to	386	program. While you can C<ready> it and do most other things you can do to
101	coro, it is mainly useful to compare again C<$Coro::current>, to see	387	coro, it is mainly useful to compare again C<$Coro::current>, to see
102	whether you are running in the main program or not.	388	whether you are running in the main program or not.
103		389
104	=cut	390	=cut
105		391
…		…
123		409
124	This variable is mainly useful to integrate Coro into event loops. It is	410	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	411	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
126	pretty low-level functionality.	412	pretty low-level functionality.
127		413
128	This variable stores either a Coro object or a callback.	414	This variable stores a Coro object that is put into the ready queue when
		415	there are no other ready threads (without invoking any ready hooks).
129		416
130	If it is a callback, the it is called whenever the scheduler finds no	417	The default implementation dies with "FATAL: deadlock detected.", followed
131	ready coros to run. The default implementation prints "FATAL:	418	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		419
139	This hook is overwritten by modules such as C<Coro::EV> and	420	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	421	C<Coro::AnyEvent> to wait on an external event that hopefully wakes up a
141	coro so the scheduler can run it.	422	coro so the scheduler can run it.
142		423
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	424	See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
150	technique.
151
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		425
155	=cut	426	=cut
156		427
157	$idle = sub {	428	# \|\|= because other modules could have provided their own by now
158	require Carp;	429	$idle \|\|= new Coro sub {
159	Carp::croak ("FATAL: deadlock detected");	430	require Coro::Debug;
		431	die "FATAL: deadlock detected.\n"
		432	. Coro::Debug::ps_listing ();
160	};	433	};
161		434
162	# this coro is necessary because a coro	435	# this coro is necessary because a coro
163	# cannot destroy itself.	436	# cannot destroy itself.
164	our @destroy;	437	our @destroy;
165	our $manager;	438	our $manager;
166		439
167	$manager = new Coro sub {	440	$manager = new Coro sub {
168	while () {	441	while () {
169	Coro::State::cancel shift @destroy	442	_destroy shift @destroy
170	while @destroy;	443	while @destroy;
171		444
172	&schedule;	445	&schedule;
173	}	446	}
174	};	447	};
…		…
206	Example: Create a new coro that just prints its arguments.	479	Example: Create a new coro that just prints its arguments.
207		480
208	async {	481	async {
209	print "@_\n";	482	print "@_\n";
210	} 1,2,3,4;	483	} 1,2,3,4;
211
212	=cut
213
214	sub async(&@) {
215	my $coro = new Coro @_;
216	$coro->ready;
217	$coro
218	}
219		484
220	=item async_pool { ... } [@args...]	485	=item async_pool { ... } [@args...]
221		486
222	Similar to C<async>, but uses a coro pool, so you should not call	487	Similar to C<async>, but uses a coro pool, so you should not call
223	terminate or join on it (although you are allowed to), and you get a	488	terminate or join on it (although you are allowed to), and you get a
…		…
280	=item schedule	545	=item schedule
281		546
282	Calls the scheduler. The scheduler will find the next coro that is	547	Calls the scheduler. The scheduler will find the next coro that is
283	to be run from the ready queue and switches to it. The next coro	548	to be run from the ready queue and switches to it. The next coro
284	to be run is simply the one with the highest priority that is longest	549	to be run is simply the one with the highest priority that is longest
285	in its ready queue. If there is no coro ready, it will clal the	550	in its ready queue. If there is no coro ready, it will call the
286	C<$Coro::idle> hook.	551	C<$Coro::idle> hook.
287		552
288	Please note that the current coro will I<not> be put into the ready	553	Please note that the current coro will I<not> be put into the ready
289	queue, so calling this function usually means you will never be called	554	queue, so calling this function usually means you will never be called
290	again unless something else (e.g. an event handler) calls C<< ->ready >>,	555	again unless something else (e.g. an event handler) calls C<< ->ready >>,
…		…
316	coro, regardless of priority. This is useful sometimes to ensure	581	coro, regardless of priority. This is useful sometimes to ensure
317	progress is made.	582	progress is made.
318		583
319	=item terminate [arg...]	584	=item terminate [arg...]
320		585
321	Terminates the current coro with the given status values (see L<cancel>).	586	Terminates the current coro with the given status values (see
		587	L<cancel>). The values will not be copied, but referenced directly.
322		588
323	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK	589	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
324		590
325	These function install enter and leave winders in the current scope. The	591	These function install enter and leave winders in the current scope. The
326	enter block will be executed when on_enter is called and whenever the	592	enter block will be executed when on_enter is called and whenever the
…		…
482	To avoid this, it is best to put a suspended coro into the ready queue	748	To avoid this, it is best to put a suspended coro into the ready queue
483	unconditionally, as every synchronisation mechanism must protect itself	749	unconditionally, as every synchronisation mechanism must protect itself
484	against spurious wakeups, and the one in the Coro family certainly do	750	against spurious wakeups, and the one in the Coro family certainly do
485	that.	751	that.
486		752
		753	=item $state->is_new
		754
		755	Returns true iff this Coro object is "new", i.e. has never been run
		756	yet. Those states basically consist of only the code reference to call and
		757	the arguments, but consumes very little other resources. New states will
		758	automatically get assigned a perl interpreter when they are transfered to.
		759
		760	=item $state->is_zombie
		761
		762	Returns true iff the Coro object has been cancelled, i.e.
		763	it's resources freed because they were C<cancel>'ed, C<terminate>'d,
		764	C<safe_cancel>'ed or simply went out of scope.
		765
		766	The name "zombie" stems from UNIX culture, where a process that has
		767	exited and only stores and exit status and no other resources is called a
		768	"zombie".
		769
487	=item $is_ready = $coro->is_ready	770	=item $is_ready = $coro->is_ready
488		771
489	Returns true iff the Coro object is in the ready queue. Unless the Coro	772	Returns true iff the Coro object is in the ready queue. Unless the Coro
490	object gets destroyed, it will eventually be scheduled by the scheduler.	773	object gets destroyed, it will eventually be scheduled by the scheduler.
491		774
…		…
500	Returns true iff this Coro object has been suspended. Suspended Coros will	783	Returns true iff this Coro object has been suspended. Suspended Coros will
501	not ever be scheduled.	784	not ever be scheduled.
502		785
503	=item $coro->cancel (arg...)	786	=item $coro->cancel (arg...)
504		787
505	Terminates the given Coro and makes it return the given arguments as	788	Terminates the given Coro thread and makes it return the given arguments as
506	status (default: the empty list). Never returns if the Coro is the	789	status (default: an empty list). Never returns if the Coro is the
507	current Coro.	790	current Coro.
508		791
509	=cut	792	This is a rather brutal way to free a coro, with some limitations - if
		793	the thread is inside a C callback that doesn't expect to be canceled,
		794	bad things can happen, or if the cancelled thread insists on running
		795	complicated cleanup handlers that rely on its thread context, things will
		796	not work.
510		797
511	sub cancel {	798	Any cleanup code being run (e.g. from C<guard> blocks) will be run without
512	my $self = shift;	799	a thread context, and is not allowed to switch to other threads. On the
		800	plus side, C<< ->cancel >> will always clean up the thread, no matter
		801	what. If your cleanup code is complex or you want to avoid cancelling a
		802	C-thread that doesn't know how to clean up itself, it can be better to C<<
		803	->throw >> an exception, or use C<< ->safe_cancel >>.
513		804
514	if ($current == $self) {	805	The arguments to C<< ->cancel >> are not copied, but instead will
515	terminate @_;	806	be referenced directly (e.g. if you pass C<$var> and after the call
516	} else {	807	change that variable, then you might change the return values passed to
517	$self->{_status} = [@_];	808	e.g. C<join>, so don't do that).
518	Coro::State::cancel $self;	809
		810	The resources of the Coro are usually freed (or destructed) before this
		811	call returns, but this can be delayed for an indefinite amount of time, as
		812	in some cases the manager thread has to run first to actually destruct the
		813	Coro object.
		814
		815	=item $coro->safe_cancel ($arg...)
		816
		817	Works mostly like C<< ->cancel >>, but is inherently "safer", and
		818	consequently, can fail with an exception in cases the thread is not in a
		819	cancellable state.
		820
		821	This method works a bit like throwing an exception that cannot be caught
		822	- specifically, it will clean up the thread from within itself, so
		823	all cleanup handlers (e.g. C<guard> blocks) are run with full thread
		824	context and can block if they wish. The downside is that there is no
		825	guarantee that the thread can be cancelled when you call this method, and
		826	therefore, it might fail. It is also considerably slower than C<cancel> or
		827	C<terminate>.
		828
		829	A thread is in a safe-cancellable state if it either hasn't been run yet,
		830	or it has no C context attached and is inside an SLF function.
		831
		832	The latter two basically mean that the thread isn't currently inside a
		833	perl callback called from some C function (usually via some XS modules)
		834	and isn't currently executing inside some C function itself (via Coro's XS
		835	API).
		836
		837	This call returns true when it could cancel the thread, or croaks with an
		838	error otherwise (i.e. it either returns true or doesn't return at all).
		839
		840	Why the weird interface? Well, there are two common models on how and
		841	when to cancel things. In the first, you have the expectation that your
		842	coro thread can be cancelled when you want to cancel it - if the thread
		843	isn't cancellable, this would be a bug somewhere, so C<< ->safe_cancel >>
		844	croaks to notify of the bug.
		845
		846	In the second model you sometimes want to ask nicely to cancel a thread,
		847	but if it's not a good time, well, then don't cancel. This can be done
		848	relatively easy like this:
		849
		850	if (! eval { $coro->safe_cancel }) {
		851	warn "unable to cancel thread: $@";
519	}	852	}
520	}	853
		854	However, what you never should do is first try to cancel "safely" and
		855	if that fails, cancel the "hard" way with C<< ->cancel >>. That makes
		856	no sense: either you rely on being able to execute cleanup code in your
		857	thread context, or you don't. If you do, then C<< ->safe_cancel >> is the
		858	only way, and if you don't, then C<< ->cancel >> is always faster and more
		859	direct.
521		860
522	=item $coro->schedule_to	861	=item $coro->schedule_to
523		862
524	Puts the current coro to sleep (like C<Coro::schedule>), but instead	863	Puts the current coro to sleep (like C<Coro::schedule>), but instead
525	of continuing with the next coro from the ready queue, always switch to	864	of continuing with the next coro from the ready queue, always switch to
…		…
544	inside the coro at the next convenient point in time. Otherwise	883	inside the coro at the next convenient point in time. Otherwise
545	clears the exception object.	884	clears the exception object.
546		885
547	Coro will check for the exception each time a schedule-like-function	886	Coro will check for the exception each time a schedule-like-function
548	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down	887	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
549	>>, C<< Coro::Handle->readable >> and so on. Most of these functions	888	>>, C<< Coro::Handle->readable >> and so on. Most of those functions (all
550	detect this case and return early in case an exception is pending.	889	that are part of Coro itself) detect this case and return early in case an
		890	exception is pending.
551		891
552	The exception object will be thrown "as is" with the specified scalar in	892	The exception object will be thrown "as is" with the specified scalar in
553	C<$@>, i.e. if it is a string, no line number or newline will be appended	893	C<$@>, i.e. if it is a string, no line number or newline will be appended
554	(unlike with C<die>).	894	(unlike with C<die>).
555		895
556	This can be used as a softer means than C<cancel> to ask a coro to	896	This can be used as a softer means than either C<cancel> or C<safe_cancel
557	end itself, although there is no guarantee that the exception will lead to	897	>to ask a coro to end itself, although there is no guarantee that the
558	termination, and if the exception isn't caught it might well end the whole	898	exception will lead to termination, and if the exception isn't caught it
559	program.	899	might well end the whole program.
560		900
561	You might also think of C<throw> as being the moral equivalent of	901	You might also think of C<throw> as being the moral equivalent of
562	C<kill>ing a coro with a signal (in this case, a scalar).	902	C<kill>ing a coro with a signal (in this case, a scalar).
563		903
564	=item $coro->join	904	=item $coro->join
565		905
566	Wait until the coro terminates and return any values given to the	906	Wait until the coro terminates and return any values given to the
567	C<terminate> or C<cancel> functions. C<join> can be called concurrently	907	C<terminate> or C<cancel> functions. C<join> can be called concurrently
568	from multiple coro, and all will be resumed and given the status	908	from multiple threads, and all will be resumed and given the status
569	return once the C<$coro> terminates.	909	return once the C<$coro> terminates.
570		910
571	=cut
572
573	sub join {
574	my $self = shift;
575
576	unless ($self->{_status}) {
577	my $current = $current;
578
579	push @{$self->{_on_destroy}}, sub {
580	$current->ready;
581	undef $current;
582	};
583
584	&schedule while $current;
585	}
586
587	wantarray ? @{$self->{_status}} : $self->{_status}[0];
588	}
589
590	=item $coro->on_destroy (\&cb)	911	=item $coro->on_destroy (\&cb)
591		912
592	Registers a callback that is called when this coro gets destroyed,	913	Registers a callback that is called when this coro thread gets destroyed,
593	but before it is joined. The callback gets passed the terminate arguments,	914	that is, after it's resources have been freed but before it is joined. The
		915	callback gets passed the terminate/cancel arguments, if any, and I<must
594	if any, and I<must not> die, under any circumstances.	916	not> die, under any circumstances.
595		917
596	=cut	918	There can be any number of C<on_destroy> callbacks per coro, and there is
597		919	currently no way to remove a callback once added.
598	sub on_destroy {
599	my ($self, $cb) = @_;
600
601	push @{ $self->{_on_destroy} }, $cb;
602	}
603		920
604	=item $oldprio = $coro->prio ($newprio)	921	=item $oldprio = $coro->prio ($newprio)
605		922
606	Sets (or gets, if the argument is missing) the priority of the	923	Sets (or gets, if the argument is missing) the priority of the
607	coro. Higher priority coro get run before lower priority	924	coro thread. Higher priority coro get run before lower priority
608	coro. Priorities are small signed integers (currently -4 .. +3),	925	coros. Priorities are small signed integers (currently -4 .. +3),
609	that you can refer to using PRIO_xxx constants (use the import tag :prio	926	that you can refer to using PRIO_xxx constants (use the import tag :prio
610	to get then):	927	to get then):
611		928
612	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	929	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
613	3 > 1 > 0 > -1 > -3 > -4	930	3 > 1 > 0 > -1 > -3 > -4
614		931
615	# set priority to HIGH	932	# set priority to HIGH
616	current->prio (PRIO_HIGH);	933	current->prio (PRIO_HIGH);
617		934
618	The idle coro ($Coro::idle) always has a lower priority than any	935	The idle coro thread ($Coro::idle) always has a lower priority than any
619	existing coro.	936	existing coro.
620		937
621	Changing the priority of the current coro will take effect immediately,	938	Changing the priority of the current coro will take effect immediately,
622	but changing the priority of coro in the ready queue (but not	939	but changing the priority of a coro in the ready queue (but not running)
623	running) will only take effect after the next schedule (of that	940	will only take effect after the next schedule (of that coro). This is a
624	coro). This is a bug that will be fixed in some future version.	941	bug that will be fixed in some future version.
625		942
626	=item $newprio = $coro->nice ($change)	943	=item $newprio = $coro->nice ($change)
627		944
628	Similar to C<prio>, but subtract the given value from the priority (i.e.	945	Similar to C<prio>, but subtract the given value from the priority (i.e.
629	higher values mean lower priority, just as in unix).	946	higher values mean lower priority, just as in UNIX's nice command).
630		947
631	=item $olddesc = $coro->desc ($newdesc)	948	=item $olddesc = $coro->desc ($newdesc)
632		949
633	Sets (or gets in case the argument is missing) the description for this	950	Sets (or gets in case the argument is missing) the description for this
634	coro. This is just a free-form string you can associate with a	951	coro thread. This is just a free-form string you can associate with a
635	coro.	952	coro.
636		953
637	This method simply sets the C<< $coro->{desc} >> member to the given	954	This method simply sets the C<< $coro->{desc} >> member to the given
638	string. You can modify this member directly if you wish.	955	string. You can modify this member directly if you wish, and in fact, this
		956	is often preferred to indicate major processing states that can then be
		957	seen for example in a L<Coro::Debug> session:
		958
		959	sub my_long_function {
		960	local $Coro::current->{desc} = "now in my_long_function";
		961	...
		962	$Coro::current->{desc} = "my_long_function: phase 1";
		963	...
		964	$Coro::current->{desc} = "my_long_function: phase 2";
		965	...
		966	}
639		967
640	=cut	968	=cut
641		969
642	sub desc {	970	sub desc {
643	my $old = $_[0]{desc};	971	my $old = $_[0]{desc};
…		…
680	returning a new coderef. Unblocking means that calling the new coderef	1008	returning a new coderef. Unblocking means that calling the new coderef
681	will return immediately without blocking, returning nothing, while the	1009	will return immediately without blocking, returning nothing, while the
682	original code ref will be called (with parameters) from within another	1010	original code ref will be called (with parameters) from within another
683	coro.	1011	coro.
684		1012
685	The reason this function exists is that many event libraries (such as the	1013	The reason this function exists is that many event libraries (such as
686	venerable L<Event\|Event> module) are not thread-safe (a weaker form	1014	the venerable L<Event\|Event> module) are not thread-safe (a weaker form
687	of reentrancy). This means you must not block within event callbacks,	1015	of reentrancy). This means you must not block within event callbacks,
688	otherwise you might suffer from crashes or worse. The only event library	1016	otherwise you might suffer from crashes or worse. The only event library
689	currently known that is safe to use without C<unblock_sub> is L<EV>.	1017	currently known that is safe to use without C<unblock_sub> is L<EV> (but
		1018	you might still run into deadlocks if all event loops are blocked).
		1019
		1020	Coro will try to catch you when you block in the event loop
		1021	("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and
		1022	only works when you do not run your own event loop.
690		1023
691	This function allows your callbacks to block by executing them in another	1024	This function allows your callbacks to block by executing them in another
692	coro where it is safe to block. One example where blocking is handy	1025	coro where it is safe to block. One example where blocking is handy
693	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	1026	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
694	disk, for example.	1027	disk, for example.
…		…
736	unshift @unblock_queue, [$cb, @_];	1069	unshift @unblock_queue, [$cb, @_];
737	$unblock_scheduler->ready;	1070	$unblock_scheduler->ready;
738	}	1071	}
739	}	1072	}
740		1073
741	=item $cb = Coro::rouse_cb	1074	=item $cb = rouse_cb
742		1075
743	Create and return a "rouse callback". That's a code reference that,	1076	Create and return a "rouse callback". That's a code reference that,
744	when called, will remember a copy of its arguments and notify the owner	1077	when called, will remember a copy of its arguments and notify the owner
745	coro of the callback.	1078	coro of the callback.
746		1079
747	See the next function.	1080	See the next function.
748		1081
749	=item @args = Coro::rouse_wait [$cb]	1082	=item @args = rouse_wait [$cb]
750		1083
751	Wait for the specified rouse callback (or the last one that was created in	1084	Wait for the specified rouse callback (or the last one that was created in
752	this coro).	1085	this coro).
753		1086
754	As soon as the callback is invoked (or when the callback was invoked	1087	As soon as the callback is invoked (or when the callback was invoked
…		…
761		1094
762	=back	1095	=back
763		1096
764	=cut	1097	=cut
765		1098
		1099	for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) {
		1100	my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"};
		1101
		1102	*{"Coro::$module\::new"} = sub {
		1103	require "Coro/$module.pm";
		1104
		1105	# some modules have their new predefined in State.xs, some don't
		1106	*{"Coro::$module\::new"} = $old
		1107	if $old;
		1108
		1109	goto &{"Coro::$module\::new"};
		1110	};
		1111	}
		1112
766	1;	1113	1;
767		1114
768	=head1 HOW TO WAIT FOR A CALLBACK	1115	=head1 HOW TO WAIT FOR A CALLBACK
769		1116
770	It is very common for a coro to wait for some callback to be	1117	It is very common for a coro to wait for some callback to be
…		…
783	But from within a coro, you often just want to write this:	1130	But from within a coro, you often just want to write this:
784		1131
785	my $status = wait_for_child $pid;	1132	my $status = wait_for_child $pid;
786		1133
787	Coro offers two functions specifically designed to make this easy,	1134	Coro offers two functions specifically designed to make this easy,
788	C<Coro::rouse_cb> and C<Coro::rouse_wait>.	1135	C<rouse_cb> and C<rouse_wait>.
789		1136
790	The first function, C<rouse_cb>, generates and returns a callback that,	1137	The first function, C<rouse_cb>, generates and returns a callback that,
791	when invoked, will save its arguments and notify the coro that	1138	when invoked, will save its arguments and notify the coro that
792	created the callback.	1139	created the callback.
793		1140
…		…
799	function mentioned above:	1146	function mentioned above:
800		1147
801	sub wait_for_child($) {	1148	sub wait_for_child($) {
802	my ($pid) = @_;	1149	my ($pid) = @_;
803		1150
804	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);	1151	my $watcher = AnyEvent->child (pid => $pid, cb => rouse_cb);
805		1152
806	my ($rpid, $rstatus) = Coro::rouse_wait;	1153	my ($rpid, $rstatus) = rouse_wait;
807	$rstatus	1154	$rstatus
808	}	1155	}
809		1156
810	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,	1157	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
811	you can roll your own, using C<schedule>:	1158	you can roll your own, using C<schedule> and C<ready>:
812		1159
813	sub wait_for_child($) {	1160	sub wait_for_child($) {
814	my ($pid) = @_;	1161	my ($pid) = @_;
815		1162
816	# store the current coro in $current,	1163	# store the current coro in $current,
…		…
819	my ($done, $rstatus);	1166	my ($done, $rstatus);
820		1167
821	# pass a closure to ->child	1168	# pass a closure to ->child
822	my $watcher = AnyEvent->child (pid => $pid, cb => sub {	1169	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
823	$rstatus = $_[1]; # remember rstatus	1170	$rstatus = $_[1]; # remember rstatus
824	$done = 1; # mark $rstatus as valud	1171	$done = 1; # mark $rstatus as valid
		1172	$current->ready; # wake up the waiting thread
825	});	1173	});
826		1174
827	# wait until the closure has been called	1175	# wait until the closure has been called
828	schedule while !$done;	1176	schedule while !$done;
829		1177
…		…
849	future to allow per-thread schedulers, but Coro::State does not yet allow	1197	future to allow per-thread schedulers, but Coro::State does not yet allow
850	this). I recommend disabling thread support and using processes, as having	1198	this). I recommend disabling thread support and using processes, as having
851	the windows process emulation enabled under unix roughly halves perl	1199	the windows process emulation enabled under unix roughly halves perl
852	performance, even when not used.	1200	performance, even when not used.
853		1201
		1202	Attempts to use threads created in another emulated process will crash
		1203	("cleanly", with a null pointer exception).
		1204
854	=item coro switching is not signal safe	1205	=item coro switching is not signal safe
855		1206
856	You must not switch to another coro from within a signal handler	1207	You must not switch to another coro from within a signal handler (only
857	(only relevant with %SIG - most event libraries provide safe signals).	1208	relevant with %SIG - most event libraries provide safe signals), I<unless>
		1209	you are sure you are not interrupting a Coro function.
858		1210
859	That means you I<MUST NOT> call any function that might "block" the	1211	That means you I<MUST NOT> call any function that might "block" the
860	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or	1212	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
861	anything that calls those. Everything else, including calling C<ready>,	1213	anything that calls those. Everything else, including calling C<ready>,
862	works.	1214	works.
863		1215
864	=back	1216	=back
865		1217
866		1218
		1219	=head1 WINDOWS PROCESS EMULATION
		1220
		1221	A great many people seem to be confused about ithreads (for example, Chip
		1222	Salzenberg called me unintelligent, incapable, stupid and gullible,
		1223	while in the same mail making rather confused statements about perl
		1224	ithreads (for example, that memory or files would be shared), showing his
		1225	lack of understanding of this area - if it is hard to understand for Chip,
		1226	it is probably not obvious to everybody).
		1227
		1228	What follows is an ultra-condensed version of my talk about threads in
		1229	scripting languages given on the perl workshop 2009:
		1230
		1231	The so-called "ithreads" were originally implemented for two reasons:
		1232	first, to (badly) emulate unix processes on native win32 perls, and
		1233	secondly, to replace the older, real thread model ("5.005-threads").
		1234
		1235	It does that by using threads instead of OS processes. The difference
		1236	between processes and threads is that threads share memory (and other
		1237	state, such as files) between threads within a single process, while
		1238	processes do not share anything (at least not semantically). That
		1239	means that modifications done by one thread are seen by others, while
		1240	modifications by one process are not seen by other processes.
		1241
		1242	The "ithreads" work exactly like that: when creating a new ithreads
		1243	process, all state is copied (memory is copied physically, files and code
		1244	is copied logically). Afterwards, it isolates all modifications. On UNIX,
		1245	the same behaviour can be achieved by using operating system processes,
		1246	except that UNIX typically uses hardware built into the system to do this
		1247	efficiently, while the windows process emulation emulates this hardware in
		1248	software (rather efficiently, but of course it is still much slower than
		1249	dedicated hardware).
		1250
		1251	As mentioned before, loading code, modifying code, modifying data
		1252	structures and so on is only visible in the ithreads process doing the
		1253	modification, not in other ithread processes within the same OS process.
		1254
		1255	This is why "ithreads" do not implement threads for perl at all, only
		1256	processes. What makes it so bad is that on non-windows platforms, you can
		1257	actually take advantage of custom hardware for this purpose (as evidenced
		1258	by the forks module, which gives you the (i-) threads API, just much
		1259	faster).
		1260
		1261	Sharing data is in the i-threads model is done by transfering data
		1262	structures between threads using copying semantics, which is very slow -
		1263	shared data simply does not exist. Benchmarks using i-threads which are
		1264	communication-intensive show extremely bad behaviour with i-threads (in
		1265	fact, so bad that Coro, which cannot take direct advantage of multiple
		1266	CPUs, is often orders of magnitude faster because it shares data using
		1267	real threads, refer to my talk for details).
		1268
		1269	As summary, i-threads use threads to implement processes, while
		1270	the compatible forks module uses processes to emulate, uhm,
		1271	processes. I-threads slow down every perl program when enabled, and
		1272	outside of windows, serve no (or little) practical purpose, but
		1273	disadvantages every single-threaded Perl program.
		1274
		1275	This is the reason that I try to avoid the name "ithreads", as it is
		1276	misleading as it implies that it implements some kind of thread model for
		1277	perl, and prefer the name "windows process emulation", which describes the
		1278	actual use and behaviour of it much better.
		1279
867	=head1 SEE ALSO	1280	=head1 SEE ALSO
868		1281
869	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.	1282	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
870		1283
871	Debugging: L<Coro::Debug>.	1284	Debugging: L<Coro::Debug>.

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Comparing Coro/Coro.pm (file contents): Revision 1.260 by root, Mon Jul 6 03:42:29 2009 UTC vs. Revision 1.321 by root, Sun Feb 2 03:26:06 2014 UTC

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Comparing Coro/Coro.pm (file contents):
Revision 1.260 by root, Mon Jul 6 03:42:29 2009 UTC vs.
Revision 1.321 by root, Sun Feb 2 03:26:06 2014 UTC