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

Comparing Coro/Coro.pm (file contents):
Revision 1.248 by root, Mon Dec 15 15:03:31 2008 UTC vs.
Revision 1.301 by root, Sun Jul 3 10:51:40 2011 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), Coro provides a	44	but only the windows process emulation (see section of same name for
		45	more details) ported to UNIX, and as such act as processes), Coro
46	full shared address space, which makes communication between threads	46	provides a full shared address space, which makes communication between
47	very easy. And threads are fast, too: disabling the Windows process	47	threads very easy. And coro threads are fast, too: disabling the Windows
48	emulation code in your perl and using Coro can easily result in a two to	48	process emulation code in your perl and using Coro can easily result in
49	four times speed increase for your programs.	49	a two to four times speed increase for your programs. A parallel matrix
		50	multiplication benchmark (very communication-intensive) runs over 300
		51	times faster on a single core than perls pseudo-threads on a quad core
		52	using all four cores.
50		53
51	Coro achieves that by supporting multiple running interpreters that share	54	Coro achieves that by supporting multiple running interpreters that share
52	data, which is especially useful to code pseudo-parallel processes and	55	data, which is especially useful to code pseudo-parallel processes and
53	for event-based programming, such as multiple HTTP-GET requests running	56	for event-based programming, such as multiple HTTP-GET requests running
54	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
55	into an event-based environment.	58	into an event-based environment.
56		59
57	In this module, a thread is defined as "callchain + lexical variables +	60	In this module, a thread is defined as "callchain + lexical variables +
58	@_ + $_ + $@ + $/ + C stack), that is, a thread has its own callchain,	61	some package variables + C stack), that is, a thread has its own callchain,
59	its own set of lexicals and its own set of perls most important global	62	its own set of lexicals and its own set of perls most important global
60	variables (see L<Coro::State> for more configuration and background info).	63	variables (see L<Coro::State> for more configuration and background info).
61		64
62	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
63	module family is quite large.	66	module family is quite large.
64		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	And yet another way is to C<< ->cancel >> (or C<< ->safe_cancel >>) the
		201	coro thread from another thread:
		202
		203	my $coro = async {
		204	exit 1;
		205	};
		206
		207	$coro->cancel; # also accepts values for ->join to retrieve
		208
		209	Cancellation I<can> be dangerous - it's a bit like calling C<exit> without
		210	actually exiting, and might leave C libraries and XS modules in a weird
		211	state. Unlike other thread implementations, however, Coro is exceptionally
		212	safe with regards to cancellation, as perl will always be in a consistent
		213	state, and for those cases where you want to do truly marvellous things
		214	with your coro while it is being cancelled - that is, make sure all
		215	cleanup code is executed from the thread being cancelled - there is even a
		216	C<< ->safe_cancel >> method.
		217
		218	So, cancelling a thread that runs in an XS event loop might not be the
		219	best idea, but any other combination that deals with perl only (cancelling
		220	when a thread is in a C<tie> method or an C<AUTOLOAD> for example) is
		221	safe.
		222
		223	Lastly, a coro thread object that isn't referenced is C<< ->cancel >>'ed
		224	automatically - just like other objects in Perl. This is not such a common
		225	case, however - a running thread is referencedy b C<$Coro::current>, a
		226	thread ready to run is referenced by the ready queue, a thread waiting
		227	on a lock or semaphore is referenced by being in some wait list and so
		228	on. But a thread that isn't in any of those queues gets cancelled:
		229
		230	async {
		231	schedule; # cede to other coros, don't go into the ready queue
		232	};
		233
		234	cede;
		235	# now the async above is destroyed, as it is not referenced by anything.
		236
		237	=item 5. Cleanup
		238
		239	Threads will allocate various resources. Most but not all will be returned
		240	when a thread terminates, during clean-up.
		241
		242	Cleanup is quite similar to throwing an uncaught exception: perl will
		243	work it's way up through all subroutine calls and blocks. On it's way, it
		244	will release all C<my> variables, undo all C<local>'s and free any other
		245	resources truly local to the thread.
		246
		247	So, a common way to free resources is to keep them referenced only by my
		248	variables:
		249
		250	async {
		251	my $big_cache = new Cache ...;
		252	};
		253
		254	If there are no other references, then the C<$big_cache> object will be
		255	freed when the thread terminates, regardless of how it does so.
		256
		257	What it does C<NOT> do is unlock any Coro::Semaphores or similar
		258	resources, but that's where the C<guard> methods come in handy:
		259
		260	my $sem = new Coro::Semaphore;
		261
		262	async {
		263	my $lock_guard = $sem->guard;
		264	# if we reutrn, or die or get cancelled, here,
		265	# then the semaphore will be "up"ed.
		266	};
		267
		268	The C<Guard::guard> function comes in handy for any custom cleanup you
		269	might want to do (but you cannot switch to other coroutines form those
		270	code blocks):
		271
		272	async {
		273	my $window = new Gtk2::Window "toplevel";
		274	# The window will not be cleaned up automatically, even when $window
		275	# gets freed, so use a guard to ensure it's destruction
		276	# in case of an error:
		277	my $window_guard = Guard::guard { $window->destroy };
		278
		279	# we are safe here
		280	};
		281
		282	Last not least, C<local> can often be handy, too, e.g. when temporarily
		283	replacing the coro thread description:
		284
		285	sub myfunction {
		286	local $Coro::current->{desc} = "inside myfunction(@_)";
		287
		288	# if we return or die here, the description will be restored
		289	}
		290
		291	=item 6. Viva La Zombie Muerte
		292
		293	Even after a thread has terminated and cleaned up its resources, the Coro
		294	object still is there and stores the return values of the thread.
		295
		296	The means the Coro object gets freed automatically when the thread has
		297	terminated and cleaned up and there arenot other references.
		298
		299	If there are, the Coro object will stay around, and you can call C<<
		300	->join >> as many times as you wish to retrieve the result values:
		301
		302	async {
		303	print "hi\n";
		304	1
		305	};
		306
		307	# run the async above, and free everything before returning
		308	# from Coro::cede:
		309	Coro::cede;
		310
		311	{
		312	my $coro = async {
		313	print "hi\n";
		314	1
		315	};
		316
		317	# run the async above, and clean up, but do not free the coro
		318	# object:
		319	Coro::cede;
		320
		321	# optionally retrieve the result values
		322	my @results = $coro->join;
		323
		324	# now $coro goes out of scope, and presumably gets freed
		325	};
		326
		327	=back
		328
65	=cut	329	=cut
66		330
67	package Coro;	331	package Coro;
68		332
69	use strict qw(vars subs);	333	use common::sense;
70	no warnings "uninitialized";	334
		335	use Carp ();
71		336
72	use Guard ();	337	use Guard ();
73		338
74	use Coro::State;	339	use Coro::State;
75		340
…		…
77		342
78	our $idle; # idle handler	343	our $idle; # idle handler
79	our $main; # main coro	344	our $main; # main coro
80	our $current; # current coro	345	our $current; # current coro
81		346
82	our $VERSION = 5.13;	347	our $VERSION = 6.01;
83		348
84	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	349	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
85	our %EXPORT_TAGS = (	350	our %EXPORT_TAGS = (
86	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	351	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
87	);	352	);
88	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	353	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
89		354
…		…
120		385
121	This variable is mainly useful to integrate Coro into event loops. It is	386	This variable is mainly useful to integrate Coro into event loops. It is
122	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is	387	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
123	pretty low-level functionality.	388	pretty low-level functionality.
124		389
125	This variable stores either a Coro object or a callback.	390	This variable stores a Coro object that is put into the ready queue when
		391	there are no other ready threads (without invoking any ready hooks).
126		392
127	If it is a callback, the it is called whenever the scheduler finds no	393	The default implementation dies with "FATAL: deadlock detected.", followed
128	ready coros to run. The default implementation prints "FATAL:	394	by a thread listing, because the program has no other way to continue.
129	deadlock detected" and exits, because the program has no other way to
130	continue.
131
132	If it is a coro object, then this object will be readied (without
133	invoking any ready hooks, however) when the scheduler finds no other ready
134	coros to run.
135		395
136	This hook is overwritten by modules such as C<Coro::EV> and	396	This hook is overwritten by modules such as C<Coro::EV> and
137	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a	397	C<Coro::AnyEvent> to wait on an external event that hopefully wakes up a
138	coro so the scheduler can run it.	398	coro so the scheduler can run it.
139		399
140	Note that the callback I<must not>, under any circumstances, block
141	the current coro. Normally, this is achieved by having an "idle
142	coro" that calls the event loop and then blocks again, and then
143	readying that coro in the idle handler, or by simply placing the idle
144	coro in this variable.
145
146	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this	400	See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
147	technique.
148
149	Please note that if your callback recursively invokes perl (e.g. for event
150	handlers), then it must be prepared to be called recursively itself.
151		401
152	=cut	402	=cut
153		403
154	$idle = sub {	404	# \|\|= because other modules could have provided their own by now
155	require Carp;	405	$idle \|\|= new Coro sub {
156	Carp::croak ("FATAL: deadlock detected");	406	require Coro::Debug;
		407	die "FATAL: deadlock detected.\n"
		408	. Coro::Debug::ps_listing ();
157	};	409	};
158		410
159	# this coro is necessary because a coro	411	# this coro is necessary because a coro
160	# cannot destroy itself.	412	# cannot destroy itself.
161	our @destroy;	413	our @destroy;
162	our $manager;	414	our $manager;
163		415
164	$manager = new Coro sub {	416	$manager = new Coro sub {
165	while () {	417	while () {
166	Coro::State::cancel shift @destroy	418	_destroy shift @destroy
167	while @destroy;	419	while @destroy;
168		420
169	&schedule;	421	&schedule;
170	}	422	}
171	};	423	};
…		…
203	Example: Create a new coro that just prints its arguments.	455	Example: Create a new coro that just prints its arguments.
204		456
205	async {	457	async {
206	print "@_\n";	458	print "@_\n";
207	} 1,2,3,4;	459	} 1,2,3,4;
208
209	=cut
210
211	sub async(&@) {
212	my $coro = new Coro @_;
213	$coro->ready;
214	$coro
215	}
216		460
217	=item async_pool { ... } [@args...]	461	=item async_pool { ... } [@args...]
218		462
219	Similar to C<async>, but uses a coro pool, so you should not call	463	Similar to C<async>, but uses a coro pool, so you should not call
220	terminate or join on it (although you are allowed to), and you get a	464	terminate or join on it (although you are allowed to), and you get a
…		…
277	=item schedule	521	=item schedule
278		522
279	Calls the scheduler. The scheduler will find the next coro that is	523	Calls the scheduler. The scheduler will find the next coro that is
280	to be run from the ready queue and switches to it. The next coro	524	to be run from the ready queue and switches to it. The next coro
281	to be run is simply the one with the highest priority that is longest	525	to be run is simply the one with the highest priority that is longest
282	in its ready queue. If there is no coro ready, it will clal the	526	in its ready queue. If there is no coro ready, it will call the
283	C<$Coro::idle> hook.	527	C<$Coro::idle> hook.
284		528
285	Please note that the current coro will I<not> be put into the ready	529	Please note that the current coro will I<not> be put into the ready
286	queue, so calling this function usually means you will never be called	530	queue, so calling this function usually means you will never be called
287	again unless something else (e.g. an event handler) calls C<< ->ready >>,	531	again unless something else (e.g. an event handler) calls C<< ->ready >>,
…		…
313	coro, regardless of priority. This is useful sometimes to ensure	557	coro, regardless of priority. This is useful sometimes to ensure
314	progress is made.	558	progress is made.
315		559
316	=item terminate [arg...]	560	=item terminate [arg...]
317		561
318	Terminates the current coro with the given status values (see L<cancel>).	562	Terminates the current coro with the given status values (see
		563	L<cancel>). The values will not be copied, but referenced directly.
319		564
320	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK	565	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
321		566
322	These function install enter and leave winders in the current scope. The	567	These function install enter and leave winders in the current scope. The
323	enter block will be executed when on_enter is called and whenever the	568	enter block will be executed when on_enter is called and whenever the
…		…
335		580
336	These functions implement the same concept as C<dynamic-wind> in scheme	581	These functions implement the same concept as C<dynamic-wind> in scheme
337	does, and are useful when you want to localise some resource to a specific	582	does, and are useful when you want to localise some resource to a specific
338	coro.	583	coro.
339		584
340	They slow down coro switching considerably for coros that use	585	They slow down thread switching considerably for coros that use them
341	them (But coro switching is still reasonably fast if the handlers are	586	(about 40% for a BLOCK with a single assignment, so thread switching is
342	fast).	587	still reasonably fast if the handlers are fast).
343		588
344	These functions are best understood by an example: The following function	589	These functions are best understood by an example: The following function
345	will change the current timezone to "Antarctica/South_Pole", which	590	will change the current timezone to "Antarctica/South_Pole", which
346	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,	591	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
347	which remember/change the current timezone and restore the previous	592	which remember/change the current timezone and restore the previous
348	value, respectively, the timezone is only changes for the coro that	593	value, respectively, the timezone is only changed for the coro that
349	installed those handlers.	594	installed those handlers.
350		595
351	use POSIX qw(tzset);	596	use POSIX qw(tzset);
352		597
353	async {	598	async {
…		…
370	};	615	};
371		616
372	This can be used to localise about any resource (locale, uid, current	617	This can be used to localise about any resource (locale, uid, current
373	working directory etc.) to a block, despite the existance of other	618	working directory etc.) to a block, despite the existance of other
374	coros.	619	coros.
		620
		621	Another interesting example implements time-sliced multitasking using
		622	interval timers (this could obviously be optimised, but does the job):
		623
		624	# "timeslice" the given block
		625	sub timeslice(&) {
		626	use Time::HiRes ();
		627
		628	Coro::on_enter {
		629	# on entering the thread, we set an VTALRM handler to cede
		630	$SIG{VTALRM} = sub { cede };
		631	# and then start the interval timer
		632	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
		633	};
		634	Coro::on_leave {
		635	# on leaving the thread, we stop the interval timer again
		636	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
		637	};
		638
		639	&{+shift};
		640	}
		641
		642	# use like this:
		643	timeslice {
		644	# The following is an endless loop that would normally
		645	# monopolise the process. Since it runs in a timesliced
		646	# environment, it will regularly cede to other threads.
		647	while () { }
		648	};
		649
375		650
376	=item killall	651	=item killall
377		652
378	Kills/terminates/cancels all coros except the currently running one.	653	Kills/terminates/cancels all coros except the currently running one.
379		654
…		…
424		699
425	This ensures that the scheduler will resume this coro automatically	700	This ensures that the scheduler will resume this coro automatically
426	once all the coro of higher priority and all coro of the same	701	once all the coro of higher priority and all coro of the same
427	priority that were put into the ready queue earlier have been resumed.	702	priority that were put into the ready queue earlier have been resumed.
428		703
		704	=item $coro->suspend
		705
		706	Suspends the specified coro. A suspended coro works just like any other
		707	coro, except that the scheduler will not select a suspended coro for
		708	execution.
		709
		710	Suspending a coro can be useful when you want to keep the coro from
		711	running, but you don't want to destroy it, or when you want to temporarily
		712	freeze a coro (e.g. for debugging) to resume it later.
		713
		714	A scenario for the former would be to suspend all (other) coros after a
		715	fork and keep them alive, so their destructors aren't called, but new
		716	coros can be created.
		717
		718	=item $coro->resume
		719
		720	If the specified coro was suspended, it will be resumed. Note that when
		721	the coro was in the ready queue when it was suspended, it might have been
		722	unreadied by the scheduler, so an activation might have been lost.
		723
		724	To avoid this, it is best to put a suspended coro into the ready queue
		725	unconditionally, as every synchronisation mechanism must protect itself
		726	against spurious wakeups, and the one in the Coro family certainly do
		727	that.
		728
		729	=item $state->is_new
		730
		731	Returns true iff this Coro object is "new", i.e. has never been run
		732	yet. Those states basically consist of only the code reference to call and
		733	the arguments, but consumes very little other resources. New states will
		734	automatically get assigned a perl interpreter when they are transfered to.
		735
		736	=item $state->is_zombie
		737
		738	Returns true iff the Coro object has been cancelled, i.e.
		739	it's resources freed because they were C<cancel>'ed, C<terminate>'d,
		740	C<safe_cancel>'ed or simply went out of scope.
		741
		742	The name "zombie" stems from UNIX culture, where a process that has
		743	exited and only stores and exit status and no other resources is called a
		744	"zombie".
		745
429	=item $is_ready = $coro->is_ready	746	=item $is_ready = $coro->is_ready
430		747
431	Returns true iff the Coro object is in the ready queue. Unless the Coro	748	Returns true iff the Coro object is in the ready queue. Unless the Coro
432	object gets destroyed, it will eventually be scheduled by the scheduler.	749	object gets destroyed, it will eventually be scheduled by the scheduler.
433		750
…		…
442	Returns true iff this Coro object has been suspended. Suspended Coros will	759	Returns true iff this Coro object has been suspended. Suspended Coros will
443	not ever be scheduled.	760	not ever be scheduled.
444		761
445	=item $coro->cancel (arg...)	762	=item $coro->cancel (arg...)
446		763
447	Terminates the given Coro and makes it return the given arguments as	764	Terminates the given Coro thread and makes it return the given arguments as
448	status (default: the empty list). Never returns if the Coro is the	765	status (default: an empty list). Never returns if the Coro is the
449	current Coro.	766	current Coro.
450		767
451	=cut	768	This is a rather brutal way to free a coro, with some limitations - if
		769	the thread is inside a C callback that doesn't expect to be canceled,
		770	bad things can happen, or if the cancelled thread insists on running
		771	complicated cleanup handlers that rely on its thread context, things will
		772	not work.
452		773
453	sub cancel {	774	Any cleanup code being run (e.g. from C<guard> blocks) will be run without
454	my $self = shift;	775	a thread context, and is not allowed to switch to other threads. On the
		776	plus side, C<< ->cancel >> will always clean up the thread, no matter
		777	what. If your cleanup code is complex or you want to avoid cancelling a
		778	C-thread that doesn't know how to clean up itself, it can be better to C<<
		779	->throw >> an exception, or use C<< ->safe_cancel >>.
455		780
456	if ($current == $self) {	781	The arguments to C<< ->cancel >> are not copied, but instead will
457	terminate @_;	782	be referenced directly (e.g. if you pass C<$var> and after the call
458	} else {	783	change that variable, then you might change the return values passed to
459	$self->{_status} = [@_];	784	e.g. C<join>, so don't do that).
460	Coro::State::cancel $self;	785
		786	The resources of the Coro are usually freed (or destructed) before this
		787	call returns, but this can be delayed for an indefinite amount of time, as
		788	in some cases the manager thread has to run first to actually destruct the
		789	Coro object.
		790
		791	=item $coro->safe_cancel ($arg...)
		792
		793	Works mostly like C<< ->cancel >>, but is inherently "safer", and
		794	consequently, can fail with an exception in cases the thread is not in a
		795	cancellable state.
		796
		797	This method works a bit like throwing an exception that cannot be caught
		798	- specifically, it will clean up the thread from within itself, so
		799	all cleanup handlers (e.g. C<guard> blocks) are run with full thread
		800	context and can block if they wish. The downside is that there is no
		801	guarantee that the thread can be cancelled when you call this method, and
		802	therefore, it might fail. It is also considerably slower than C<cancel> or
		803	C<terminate>.
		804
		805	A thread is in a safe-cancellable state if it either hasn't been run yet,
		806	or it has no C context attached and is inside an SLF function.
		807
		808	The latter two basically mean that the thread isn't currently inside a
		809	perl callback called from some C function (usually via some XS modules)
		810	and isn't currently executing inside some C function itself (via Coro's XS
		811	API).
		812
		813	This call returns true when it could cancel the thread, or croaks with an
		814	error otherwise (i.e. it either returns true or doesn't return at all).
		815
		816	Why the weird interface? Well, there are two common models on how and
		817	when to cancel things. In the first, you have the expectation that your
		818	coro thread can be cancelled when you want to cancel it - if the thread
		819	isn't cancellable, this would be a bug somewhere, so C<< ->safe_cancel >>
		820	croaks to notify of the bug.
		821
		822	In the second model you sometimes want to ask nicely to cancel a thread,
		823	but if it's not a good time, well, then don't cancel. This can be done
		824	relatively easy like this:
		825
		826	if (! eval { $coro->safe_cancel }) {
		827	warn "unable to cancel thread: $@";
461	}	828	}
462	}	829
		830	However, what you never should do is first try to cancel "safely" and
		831	if that fails, cancel the "hard" way with C<< ->cancel >>. That makes
		832	no sense: either you rely on being able to execute cleanup code in your
		833	thread context, or you don't. If you do, then C<< ->safe_cancel >> is the
		834	only way, and if you don't, then C<< ->cancel >> is always faster and more
		835	direct.
463		836
464	=item $coro->schedule_to	837	=item $coro->schedule_to
465		838
466	Puts the current coro to sleep (like C<Coro::schedule>), but instead	839	Puts the current coro to sleep (like C<Coro::schedule>), but instead
467	of continuing with the next coro from the ready queue, always switch to	840	of continuing with the next coro from the ready queue, always switch to
…		…
486	inside the coro at the next convenient point in time. Otherwise	859	inside the coro at the next convenient point in time. Otherwise
487	clears the exception object.	860	clears the exception object.
488		861
489	Coro will check for the exception each time a schedule-like-function	862	Coro will check for the exception each time a schedule-like-function
490	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down	863	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
491	>>, C<< Coro::Handle->readable >> and so on. Most of these functions	864	>>, C<< Coro::Handle->readable >> and so on. Most of those functions (all
492	detect this case and return early in case an exception is pending.	865	that are part of Coro itself) detect this case and return early in case an
		866	exception is pending.
493		867
494	The exception object will be thrown "as is" with the specified scalar in	868	The exception object will be thrown "as is" with the specified scalar in
495	C<$@>, i.e. if it is a string, no line number or newline will be appended	869	C<$@>, i.e. if it is a string, no line number or newline will be appended
496	(unlike with C<die>).	870	(unlike with C<die>).
497		871
498	This can be used as a softer means than C<cancel> to ask a coro to	872	This can be used as a softer means than either C<cancel> or C<safe_cancel
499	end itself, although there is no guarantee that the exception will lead to	873	>to ask a coro to end itself, although there is no guarantee that the
500	termination, and if the exception isn't caught it might well end the whole	874	exception will lead to termination, and if the exception isn't caught it
501	program.	875	might well end the whole program.
502		876
503	You might also think of C<throw> as being the moral equivalent of	877	You might also think of C<throw> as being the moral equivalent of
504	C<kill>ing a coro with a signal (in this case, a scalar).	878	C<kill>ing a coro with a signal (in this case, a scalar).
505		879
506	=item $coro->join	880	=item $coro->join
507		881
508	Wait until the coro terminates and return any values given to the	882	Wait until the coro terminates and return any values given to the
509	C<terminate> or C<cancel> functions. C<join> can be called concurrently	883	C<terminate> or C<cancel> functions. C<join> can be called concurrently
510	from multiple coro, and all will be resumed and given the status	884	from multiple threads, and all will be resumed and given the status
511	return once the C<$coro> terminates.	885	return once the C<$coro> terminates.
512		886
513	=cut
514
515	sub join {
516	my $self = shift;
517
518	unless ($self->{_status}) {
519	my $current = $current;
520
521	push @{$self->{_on_destroy}}, sub {
522	$current->ready;
523	undef $current;
524	};
525
526	&schedule while $current;
527	}
528
529	wantarray ? @{$self->{_status}} : $self->{_status}[0];
530	}
531
532	=item $coro->on_destroy (\&cb)	887	=item $coro->on_destroy (\&cb)
533		888
534	Registers a callback that is called when this coro gets destroyed,	889	Registers a callback that is called when this coro thread gets destroyed,
535	but before it is joined. The callback gets passed the terminate arguments,	890	that is, after it's resources have been freed but before it is joined. The
		891	callback gets passed the terminate/cancel arguments, if any, and I<must
536	if any, and I<must not> die, under any circumstances.	892	not> die, under any circumstances.
537		893
538	=cut	894	There can be any number of C<on_destroy> callbacks per coro, and there is
539		895	no way currently to remove a callback once added.
540	sub on_destroy {
541	my ($self, $cb) = @_;
542
543	push @{ $self->{_on_destroy} }, $cb;
544	}
545		896
546	=item $oldprio = $coro->prio ($newprio)	897	=item $oldprio = $coro->prio ($newprio)
547		898
548	Sets (or gets, if the argument is missing) the priority of the	899	Sets (or gets, if the argument is missing) the priority of the
549	coro. Higher priority coro get run before lower priority	900	coro thread. Higher priority coro get run before lower priority
550	coro. Priorities are small signed integers (currently -4 .. +3),	901	coros. Priorities are small signed integers (currently -4 .. +3),
551	that you can refer to using PRIO_xxx constants (use the import tag :prio	902	that you can refer to using PRIO_xxx constants (use the import tag :prio
552	to get then):	903	to get then):
553		904
554	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	905	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
555	3 > 1 > 0 > -1 > -3 > -4	906	3 > 1 > 0 > -1 > -3 > -4
556		907
557	# set priority to HIGH	908	# set priority to HIGH
558	current->prio (PRIO_HIGH);	909	current->prio (PRIO_HIGH);
559		910
560	The idle coro ($Coro::idle) always has a lower priority than any	911	The idle coro thread ($Coro::idle) always has a lower priority than any
561	existing coro.	912	existing coro.
562		913
563	Changing the priority of the current coro will take effect immediately,	914	Changing the priority of the current coro will take effect immediately,
564	but changing the priority of coro in the ready queue (but not	915	but changing the priority of a coro in the ready queue (but not running)
565	running) will only take effect after the next schedule (of that	916	will only take effect after the next schedule (of that coro). This is a
566	coro). This is a bug that will be fixed in some future version.	917	bug that will be fixed in some future version.
567		918
568	=item $newprio = $coro->nice ($change)	919	=item $newprio = $coro->nice ($change)
569		920
570	Similar to C<prio>, but subtract the given value from the priority (i.e.	921	Similar to C<prio>, but subtract the given value from the priority (i.e.
571	higher values mean lower priority, just as in unix).	922	higher values mean lower priority, just as in UNIX's nice command).
572		923
573	=item $olddesc = $coro->desc ($newdesc)	924	=item $olddesc = $coro->desc ($newdesc)
574		925
575	Sets (or gets in case the argument is missing) the description for this	926	Sets (or gets in case the argument is missing) the description for this
576	coro. This is just a free-form string you can associate with a	927	coro thread. This is just a free-form string you can associate with a
577	coro.	928	coro.
578		929
579	This method simply sets the C<< $coro->{desc} >> member to the given	930	This method simply sets the C<< $coro->{desc} >> member to the given
580	string. You can modify this member directly if you wish.	931	string. You can modify this member directly if you wish, and in fact, this
		932	is often preferred to indicate major processing states that cna then be
		933	seen for example in a L<Coro::Debug> session:
		934
		935	sub my_long_function {
		936	local $Coro::current->{desc} = "now in my_long_function";
		937	...
		938	$Coro::current->{desc} = "my_long_function: phase 1";
		939	...
		940	$Coro::current->{desc} = "my_long_function: phase 2";
		941	...
		942	}
581		943
582	=cut	944	=cut
583		945
584	sub desc {	946	sub desc {
585	my $old = $_[0]{desc};	947	my $old = $_[0]{desc};
…		…
622	returning a new coderef. Unblocking means that calling the new coderef	984	returning a new coderef. Unblocking means that calling the new coderef
623	will return immediately without blocking, returning nothing, while the	985	will return immediately without blocking, returning nothing, while the
624	original code ref will be called (with parameters) from within another	986	original code ref will be called (with parameters) from within another
625	coro.	987	coro.
626		988
627	The reason this function exists is that many event libraries (such as the	989	The reason this function exists is that many event libraries (such as
628	venerable L<Event\|Event> module) are not thread-safe (a weaker form	990	the venerable L<Event\|Event> module) are not thread-safe (a weaker form
629	of reentrancy). This means you must not block within event callbacks,	991	of reentrancy). This means you must not block within event callbacks,
630	otherwise you might suffer from crashes or worse. The only event library	992	otherwise you might suffer from crashes or worse. The only event library
631	currently known that is safe to use without C<unblock_sub> is L<EV>.	993	currently known that is safe to use without C<unblock_sub> is L<EV> (but
		994	you might still run into deadlocks if all event loops are blocked).
		995
		996	Coro will try to catch you when you block in the event loop
		997	("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and
		998	only works when you do not run your own event loop.
632		999
633	This function allows your callbacks to block by executing them in another	1000	This function allows your callbacks to block by executing them in another
634	coro where it is safe to block. One example where blocking is handy	1001	coro where it is safe to block. One example where blocking is handy
635	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	1002	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
636	disk, for example.	1003	disk, for example.
…		…
678	unshift @unblock_queue, [$cb, @_];	1045	unshift @unblock_queue, [$cb, @_];
679	$unblock_scheduler->ready;	1046	$unblock_scheduler->ready;
680	}	1047	}
681	}	1048	}
682		1049
683	=item $cb = Coro::rouse_cb	1050	=item $cb = rouse_cb
684		1051
685	Create and return a "rouse callback". That's a code reference that,	1052	Create and return a "rouse callback". That's a code reference that,
686	when called, will remember a copy of its arguments and notify the owner	1053	when called, will remember a copy of its arguments and notify the owner
687	coro of the callback.	1054	coro of the callback.
688		1055
689	See the next function.	1056	See the next function.
690		1057
691	=item @args = Coro::rouse_wait [$cb]	1058	=item @args = rouse_wait [$cb]
692		1059
693	Wait for the specified rouse callback (or the last one that was created in	1060	Wait for the specified rouse callback (or the last one that was created in
694	this coro).	1061	this coro).
695		1062
696	As soon as the callback is invoked (or when the callback was invoked	1063	As soon as the callback is invoked (or when the callback was invoked
697	before C<rouse_wait>), it will return the arguments originally passed to	1064	before C<rouse_wait>), it will return the arguments originally passed to
698	the rouse callback.	1065	the rouse callback. In scalar context, that means you get the I<last>
		1066	argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
		1067	statement at the end.
699		1068
700	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.	1069	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
701		1070
702	=back	1071	=back
703		1072
704	=cut	1073	=cut
		1074
		1075	for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) {
		1076	my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"};
		1077
		1078	*{"Coro::$module\::new"} = sub {
		1079	require "Coro/$module.pm";
		1080
		1081	# some modules have their new predefined in State.xs, some don't
		1082	*{"Coro::$module\::new"} = $old
		1083	if $old;
		1084
		1085	goto &{"Coro::$module\::new"};
		1086	};
		1087	}
705		1088
706	1;	1089	1;
707		1090
708	=head1 HOW TO WAIT FOR A CALLBACK	1091	=head1 HOW TO WAIT FOR A CALLBACK
709		1092
…		…
789	future to allow per-thread schedulers, but Coro::State does not yet allow	1172	future to allow per-thread schedulers, but Coro::State does not yet allow
790	this). I recommend disabling thread support and using processes, as having	1173	this). I recommend disabling thread support and using processes, as having
791	the windows process emulation enabled under unix roughly halves perl	1174	the windows process emulation enabled under unix roughly halves perl
792	performance, even when not used.	1175	performance, even when not used.
793		1176
		1177	Attempts to use threads created in another emulated process will crash
		1178	("cleanly", with a null pointer exception).
		1179
794	=item coro switching is not signal safe	1180	=item coro switching is not signal safe
795		1181
796	You must not switch to another coro from within a signal handler	1182	You must not switch to another coro from within a signal handler (only
797	(only relevant with %SIG - most event libraries provide safe signals).	1183	relevant with %SIG - most event libraries provide safe signals), I<unless>
		1184	you are sure you are not interrupting a Coro function.
798		1185
799	That means you I<MUST NOT> call any function that might "block" the	1186	That means you I<MUST NOT> call any function that might "block" the
800	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or	1187	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
801	anything that calls those. Everything else, including calling C<ready>,	1188	anything that calls those. Everything else, including calling C<ready>,
802	works.	1189	works.
803		1190
804	=back	1191	=back
805		1192
806		1193
		1194	=head1 WINDOWS PROCESS EMULATION
		1195
		1196	A great many people seem to be confused about ithreads (for example, Chip
		1197	Salzenberg called me unintelligent, incapable, stupid and gullible,
		1198	while in the same mail making rather confused statements about perl
		1199	ithreads (for example, that memory or files would be shared), showing his
		1200	lack of understanding of this area - if it is hard to understand for Chip,
		1201	it is probably not obvious to everybody).
		1202
		1203	What follows is an ultra-condensed version of my talk about threads in
		1204	scripting languages given on the perl workshop 2009:
		1205
		1206	The so-called "ithreads" were originally implemented for two reasons:
		1207	first, to (badly) emulate unix processes on native win32 perls, and
		1208	secondly, to replace the older, real thread model ("5.005-threads").
		1209
		1210	It does that by using threads instead of OS processes. The difference
		1211	between processes and threads is that threads share memory (and other
		1212	state, such as files) between threads within a single process, while
		1213	processes do not share anything (at least not semantically). That
		1214	means that modifications done by one thread are seen by others, while
		1215	modifications by one process are not seen by other processes.
		1216
		1217	The "ithreads" work exactly like that: when creating a new ithreads
		1218	process, all state is copied (memory is copied physically, files and code
		1219	is copied logically). Afterwards, it isolates all modifications. On UNIX,
		1220	the same behaviour can be achieved by using operating system processes,
		1221	except that UNIX typically uses hardware built into the system to do this
		1222	efficiently, while the windows process emulation emulates this hardware in
		1223	software (rather efficiently, but of course it is still much slower than
		1224	dedicated hardware).
		1225
		1226	As mentioned before, loading code, modifying code, modifying data
		1227	structures and so on is only visible in the ithreads process doing the
		1228	modification, not in other ithread processes within the same OS process.
		1229
		1230	This is why "ithreads" do not implement threads for perl at all, only
		1231	processes. What makes it so bad is that on non-windows platforms, you can
		1232	actually take advantage of custom hardware for this purpose (as evidenced
		1233	by the forks module, which gives you the (i-) threads API, just much
		1234	faster).
		1235
		1236	Sharing data is in the i-threads model is done by transfering data
		1237	structures between threads using copying semantics, which is very slow -
		1238	shared data simply does not exist. Benchmarks using i-threads which are
		1239	communication-intensive show extremely bad behaviour with i-threads (in
		1240	fact, so bad that Coro, which cannot take direct advantage of multiple
		1241	CPUs, is often orders of magnitude faster because it shares data using
		1242	real threads, refer to my talk for details).
		1243
		1244	As summary, i-threads use threads to implement processes, while
		1245	the compatible forks module uses processes to emulate, uhm,
		1246	processes. I-threads slow down every perl program when enabled, and
		1247	outside of windows, serve no (or little) practical purpose, but
		1248	disadvantages every single-threaded Perl program.
		1249
		1250	This is the reason that I try to avoid the name "ithreads", as it is
		1251	misleading as it implies that it implements some kind of thread model for
		1252	perl, and prefer the name "windows process emulation", which describes the
		1253	actual use and behaviour of it much better.
		1254
807	=head1 SEE ALSO	1255	=head1 SEE ALSO
808		1256
809	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.	1257	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
810		1258
811	Debugging: L<Coro::Debug>.	1259	Debugging: L<Coro::Debug>.

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Comparing Coro/Coro.pm (file contents): Revision 1.248 by root, Mon Dec 15 15:03:31 2008 UTC vs. Revision 1.301 by root, Sun Jul 3 10:51:40 2011 UTC

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Comparing Coro/Coro.pm (file contents):
Revision 1.248 by root, Mon Dec 15 15:03:31 2008 UTC vs.
Revision 1.301 by root, Sun Jul 3 10:51:40 2011 UTC