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

Comparing Coro/Coro.pm (file contents):
Revision 1.262 by root, Wed Jul 22 03:02:07 2009 UTC vs.
Revision 1.346 by root, Fri Jul 14 23:20:07 2017 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 = 5.161;	371	our $VERSION = 6.513;
86		372
87	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	373	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
88	our %EXPORT_TAGS = (	374	our %EXPORT_TAGS = (
89	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	375	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
90	);	376	);
91	our @EXPORT_OK = (@{$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	$coro
218	}
219		484
220	=item async_pool { ... } [@args...]	485	=item async_pool { ... } [@args...]
221		486
222	Similar to C<async>, but uses a coro pool, so you should not call	487	Similar to C<async>, but uses a coro pool, so you should not call
223	terminate or join on it (although you are allowed to), and you get a	488	terminate or join on it (although you are allowed to), and you get a
…		…
233	C<async> does. As the coro is being reused, stuff like C<on_destroy>	498	C<async> does. As the coro is being reused, stuff like C<on_destroy>
234	will not work in the expected way, unless you call terminate or cancel,	499	will not work in the expected way, unless you call terminate or cancel,
235	which somehow defeats the purpose of pooling (but is fine in the	500	which somehow defeats the purpose of pooling (but is fine in the
236	exceptional case).	501	exceptional case).
237		502
238	The priority will be reset to C<0> after each run, tracing will be	503	The priority will be reset to C<0> after each run, all C<swap_sv> calls
239	disabled, the description will be reset and the default output filehandle	504	will be undone, tracing will be disabled, the description will be reset
240	gets restored, so you can change all these. Otherwise the coro will	505	and the default output filehandle gets restored, so you can change all
241	be re-used "as-is": most notably if you change other per-coro global	506	these. Otherwise the coro will be re-used "as-is": most notably if you
242	stuff such as C<$/> you I<must needs> revert that change, which is most	507	change other per-coro global stuff such as C<$/> you I<must needs> revert
243	simply done by using local as in: C<< local $/ >>.	508	that change, which is most simply done by using local as in: C<< local $/
		509	>>.
244		510
245	The idle pool size is limited to C<8> idle coros (this can be	511	The idle pool size is limited to C<8> idle coros (this can be
246	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle	512	adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
247	coros as required.	513	coros as required.
248		514
…		…
280	=item schedule	546	=item schedule
281		547
282	Calls the scheduler. The scheduler will find the next coro that is	548	Calls the scheduler. The scheduler will find the next coro that is
283	to be run from the ready queue and switches to it. The next coro	549	to be run from the ready queue and switches to it. The next coro
284	to be run is simply the one with the highest priority that is longest	550	to be run is simply the one with the highest priority that is longest
285	in its ready queue. If there is no coro ready, it will clal the	551	in its ready queue. If there is no coro ready, it will call the
286	C<$Coro::idle> hook.	552	C<$Coro::idle> hook.
287		553
288	Please note that the current coro will I<not> be put into the ready	554	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	555	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 >>,	556	again unless something else (e.g. an event handler) calls C<< ->ready >>,
…		…
316	coro, regardless of priority. This is useful sometimes to ensure	582	coro, regardless of priority. This is useful sometimes to ensure
317	progress is made.	583	progress is made.
318		584
319	=item terminate [arg...]	585	=item terminate [arg...]
320		586
321	Terminates the current coro with the given status values (see L<cancel>).	587	Terminates the current coro with the given status values (see
		588	L<cancel>). The values will not be copied, but referenced directly.
322		589
323	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK	590	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
324		591
325	These function install enter and leave winders in the current scope. The	592	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	593	enter block will be executed when on_enter is called and whenever the
…		…
371	# at this place, the timezone is Antarctica/South_Pole,	638	# at this place, the timezone is Antarctica/South_Pole,
372	# without disturbing the TZ of any other coro.	639	# without disturbing the TZ of any other coro.
373	};	640	};
374		641
375	This can be used to localise about any resource (locale, uid, current	642	This can be used to localise about any resource (locale, uid, current
376	working directory etc.) to a block, despite the existance of other	643	working directory etc.) to a block, despite the existence of other
377	coros.	644	coros.
378		645
379	Another interesting example implements time-sliced multitasking using	646	Another interesting example implements time-sliced multitasking using
380	interval timers (this could obviously be optimised, but does the job):	647	interval timers (this could obviously be optimised, but does the job):
381		648
…		…
386	Coro::on_enter {	653	Coro::on_enter {
387	# on entering the thread, we set an VTALRM handler to cede	654	# on entering the thread, we set an VTALRM handler to cede
388	$SIG{VTALRM} = sub { cede };	655	$SIG{VTALRM} = sub { cede };
389	# and then start the interval timer	656	# and then start the interval timer
390	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;	657	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
391	};	658	};
392	Coro::on_leave {	659	Coro::on_leave {
393	# on leaving the thread, we stop the interval timer again	660	# on leaving the thread, we stop the interval timer again
394	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;	661	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
395	};	662	};
396		663
397	&{+shift};	664	&{+shift};
398	}	665	}
399		666
400	# use like this:	667	# use like this:
401	timeslice {	668	timeslice {
402	# The following is an endless loop that would normally	669	# The following is an endless loop that would normally
403	# monopolise the process. Since it runs in a timesliced	670	# monopolise the process. Since it runs in a timesliced
404	# environment, it will regularly cede to other threads.	671	# environment, it will regularly cede to other threads.
405	while () { }	672	while () { }
406	};	673	};
407		674
408		675
409	=item killall	676	=item killall
410		677
411	Kills/terminates/cancels all coros except the currently running one.	678	Kills/terminates/cancels all coros except the currently running one.
…		…
482	To avoid this, it is best to put a suspended coro into the ready queue	749	To avoid this, it is best to put a suspended coro into the ready queue
483	unconditionally, as every synchronisation mechanism must protect itself	750	unconditionally, as every synchronisation mechanism must protect itself
484	against spurious wakeups, and the one in the Coro family certainly do	751	against spurious wakeups, and the one in the Coro family certainly do
485	that.	752	that.
486		753
		754	=item $state->is_new
		755
		756	Returns true iff this Coro object is "new", i.e. has never been run
		757	yet. Those states basically consist of only the code reference to call and
		758	the arguments, but consumes very little other resources. New states will
		759	automatically get assigned a perl interpreter when they are transferred to.
		760
		761	=item $state->is_zombie
		762
		763	Returns true iff the Coro object has been cancelled, i.e.
		764	it's resources freed because they were C<cancel>'ed, C<terminate>'d,
		765	C<safe_cancel>'ed or simply went out of scope.
		766
		767	The name "zombie" stems from UNIX culture, where a process that has
		768	exited and only stores and exit status and no other resources is called a
		769	"zombie".
		770
487	=item $is_ready = $coro->is_ready	771	=item $is_ready = $coro->is_ready
488		772
489	Returns true iff the Coro object is in the ready queue. Unless the Coro	773	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.	774	object gets destroyed, it will eventually be scheduled by the scheduler.
491		775
…		…
500	Returns true iff this Coro object has been suspended. Suspended Coros will	784	Returns true iff this Coro object has been suspended. Suspended Coros will
501	not ever be scheduled.	785	not ever be scheduled.
502		786
503	=item $coro->cancel (arg...)	787	=item $coro->cancel (arg...)
504		788
505	Terminates the given Coro and makes it return the given arguments as	789	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	790	status (default: an empty list). Never returns if the Coro is the
507	current Coro.	791	current Coro.
508		792
509	=cut	793	This is a rather brutal way to free a coro, with some limitations - if
		794	the thread is inside a C callback that doesn't expect to be canceled,
		795	bad things can happen, or if the cancelled thread insists on running
		796	complicated cleanup handlers that rely on its thread context, things will
		797	not work.
510		798
511	sub cancel {	799	Any cleanup code being run (e.g. from C<guard> blocks, destructors and so
512	my $self = shift;	800	on) will be run without a thread context, and is not allowed to switch
		801	to other threads. A common mistake is to call C<< ->cancel >> from a
		802	destructor called by die'ing inside the thread to be cancelled for
		803	example.
513		804
514	if ($current == $self) {	805	On the plus side, C<< ->cancel >> will always clean up the thread, no
515	terminate @_;	806	matter what. If your cleanup code is complex or you want to avoid
516	} else {	807	cancelling a C-thread that doesn't know how to clean up itself, it can be
517	$self->{_status} = [@_];	808	better to C<< ->throw >> an exception, or use C<< ->safe_cancel >>.
518	Coro::State::cancel $self;	809
		810	The arguments to C<< ->cancel >> are not copied, but instead will
		811	be referenced directly (e.g. if you pass C<$var> and after the call
		812	change that variable, then you might change the return values passed to
		813	e.g. C<join>, so don't do that).
		814
		815	The resources of the Coro are usually freed (or destructed) before this
		816	call returns, but this can be delayed for an indefinite amount of time, as
		817	in some cases the manager thread has to run first to actually destruct the
		818	Coro object.
		819
		820	=item $coro->safe_cancel ($arg...)
		821
		822	Works mostly like C<< ->cancel >>, but is inherently "safer", and
		823	consequently, can fail with an exception in cases the thread is not in a
		824	cancellable state. Essentially, C<< ->safe_cancel >> is a C<< ->cancel >>
		825	with extra checks before canceling.
		826
		827	It works a bit like throwing an exception that cannot be caught -
		828	specifically, it will clean up the thread from within itself, so all
		829	cleanup handlers (e.g. C<guard> blocks) are run with full thread
		830	context and can block if they wish. The downside is that there is no
		831	guarantee that the thread can be cancelled when you call this method, and
		832	therefore, it might fail. It is also considerably slower than C<cancel> or
		833	C<terminate>.
		834
		835	A thread is in a safe-cancellable state if it either hasn't been run yet,
		836	or it has no C context attached and is inside an SLF function.
		837
		838	The latter two basically mean that the thread isn't currently inside a
		839	perl callback called from some C function (usually via some XS modules)
		840	and isn't currently executing inside some C function itself (via Coro's XS
		841	API).
		842
		843	This call returns true when it could cancel the thread, or croaks with an
		844	error otherwise (i.e. it either returns true or doesn't return at all).
		845
		846	Why the weird interface? Well, there are two common models on how and
		847	when to cancel things. In the first, you have the expectation that your
		848	coro thread can be cancelled when you want to cancel it - if the thread
		849	isn't cancellable, this would be a bug somewhere, so C<< ->safe_cancel >>
		850	croaks to notify of the bug.
		851
		852	In the second model you sometimes want to ask nicely to cancel a thread,
		853	but if it's not a good time, well, then don't cancel. This can be done
		854	relatively easy like this:
		855
		856	if (! eval { $coro->safe_cancel }) {
		857	warn "unable to cancel thread: $@";
519	}	858	}
520	}	859
		860	However, what you never should do is first try to cancel "safely" and
		861	if that fails, cancel the "hard" way with C<< ->cancel >>. That makes
		862	no sense: either you rely on being able to execute cleanup code in your
		863	thread context, or you don't. If you do, then C<< ->safe_cancel >> is the
		864	only way, and if you don't, then C<< ->cancel >> is always faster and more
		865	direct.
521		866
522	=item $coro->schedule_to	867	=item $coro->schedule_to
523		868
524	Puts the current coro to sleep (like C<Coro::schedule>), but instead	869	Puts the current coro to sleep (like C<Coro::schedule>), but instead
525	of continuing with the next coro from the ready queue, always switch to	870	of continuing with the next coro from the ready queue, always switch to
…		…
544	inside the coro at the next convenient point in time. Otherwise	889	inside the coro at the next convenient point in time. Otherwise
545	clears the exception object.	890	clears the exception object.
546		891
547	Coro will check for the exception each time a schedule-like-function	892	Coro will check for the exception each time a schedule-like-function
548	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down	893	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
549	>>, C<< Coro::Handle->readable >> and so on. Most of these functions	894	>>, C<< Coro::Handle->readable >> and so on. Most of those functions (all
550	detect this case and return early in case an exception is pending.	895	that are part of Coro itself) detect this case and return early in case an
		896	exception is pending.
551		897
552	The exception object will be thrown "as is" with the specified scalar in	898	The exception object will be thrown "as is" with the specified scalar in
553	C<$@>, i.e. if it is a string, no line number or newline will be appended	899	C<$@>, i.e. if it is a string, no line number or newline will be appended
554	(unlike with C<die>).	900	(unlike with C<die>).
555		901
556	This can be used as a softer means than C<cancel> to ask a coro to	902	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	903	>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	904	exception will lead to termination, and if the exception isn't caught it
559	program.	905	might well end the whole program.
560		906
561	You might also think of C<throw> as being the moral equivalent of	907	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).	908	C<kill>ing a coro with a signal (in this case, a scalar).
563		909
564	=item $coro->join	910	=item $coro->join
565		911
566	Wait until the coro terminates and return any values given to the	912	Wait until the coro terminates and return any values given to the
567	C<terminate> or C<cancel> functions. C<join> can be called concurrently	913	C<terminate> or C<cancel> functions. C<join> can be called concurrently
568	from multiple coro, and all will be resumed and given the status	914	from multiple threads, and all will be resumed and given the status
569	return once the C<$coro> terminates.	915	return once the C<$coro> terminates.
570		916
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)	917	=item $coro->on_destroy (\&cb)
591		918
592	Registers a callback that is called when this coro gets destroyed,	919	Registers a callback that is called when this coro thread gets destroyed,
593	but before it is joined. The callback gets passed the terminate arguments,	920	that is, after it's resources have been freed but before it is joined. The
		921	callback gets passed the terminate/cancel arguments, if any, and I<must
594	if any, and I<must not> die, under any circumstances.	922	not> die, under any circumstances.
595		923
596	=cut	924	There can be any number of C<on_destroy> callbacks per coro, and there is
597		925	currently no way to remove a callback once added.
598	sub on_destroy {
599	my ($self, $cb) = @_;
600
601	push @{ $self->{_on_destroy} }, $cb;
602	}
603		926
604	=item $oldprio = $coro->prio ($newprio)	927	=item $oldprio = $coro->prio ($newprio)
605		928
606	Sets (or gets, if the argument is missing) the priority of the	929	Sets (or gets, if the argument is missing) the priority of the
607	coro. Higher priority coro get run before lower priority	930	coro thread. Higher priority coro get run before lower priority
608	coro. Priorities are small signed integers (currently -4 .. +3),	931	coros. Priorities are small signed integers (currently -4 .. +3),
609	that you can refer to using PRIO_xxx constants (use the import tag :prio	932	that you can refer to using PRIO_xxx constants (use the import tag :prio
610	to get then):	933	to get then):
611		934
612	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	935	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
613	3 > 1 > 0 > -1 > -3 > -4	936	3 > 1 > 0 > -1 > -3 > -4
614		937
615	# set priority to HIGH	938	# set priority to HIGH
616	current->prio (PRIO_HIGH);	939	current->prio (PRIO_HIGH);
617		940
618	The idle coro ($Coro::idle) always has a lower priority than any	941	The idle coro thread ($Coro::idle) always has a lower priority than any
619	existing coro.	942	existing coro.
620		943
621	Changing the priority of the current coro will take effect immediately,	944	Changing the priority of the current coro will take effect immediately,
622	but changing the priority of coro in the ready queue (but not	945	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	946	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.	947	bug that will be fixed in some future version.
625		948
626	=item $newprio = $coro->nice ($change)	949	=item $newprio = $coro->nice ($change)
627		950
628	Similar to C<prio>, but subtract the given value from the priority (i.e.	951	Similar to C<prio>, but subtract the given value from the priority (i.e.
629	higher values mean lower priority, just as in unix).	952	higher values mean lower priority, just as in UNIX's nice command).
630		953
631	=item $olddesc = $coro->desc ($newdesc)	954	=item $olddesc = $coro->desc ($newdesc)
632		955
633	Sets (or gets in case the argument is missing) the description for this	956	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	957	coro thread. This is just a free-form string you can associate with a
635	coro.	958	coro.
636		959
637	This method simply sets the C<< $coro->{desc} >> member to the given	960	This method simply sets the C<< $coro->{desc} >> member to the given
638	string. You can modify this member directly if you wish.	961	string. You can modify this member directly if you wish, and in fact, this
		962	is often preferred to indicate major processing states that can then be
		963	seen for example in a L<Coro::Debug> session:
		964
		965	sub my_long_function {
		966	local $Coro::current->{desc} = "now in my_long_function";
		967	...
		968	$Coro::current->{desc} = "my_long_function: phase 1";
		969	...
		970	$Coro::current->{desc} = "my_long_function: phase 2";
		971	...
		972	}
639		973
640	=cut	974	=cut
641		975
642	sub desc {	976	sub desc {
643	my $old = $_[0]{desc};	977	my $old = $_[0]{desc};
…		…
680	returning a new coderef. Unblocking means that calling the new coderef	1014	returning a new coderef. Unblocking means that calling the new coderef
681	will return immediately without blocking, returning nothing, while the	1015	will return immediately without blocking, returning nothing, while the
682	original code ref will be called (with parameters) from within another	1016	original code ref will be called (with parameters) from within another
683	coro.	1017	coro.
684		1018
685	The reason this function exists is that many event libraries (such as the	1019	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	1020	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,	1021	of reentrancy). This means you must not block within event callbacks,
688	otherwise you might suffer from crashes or worse. The only event library	1022	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>.	1023	currently known that is safe to use without C<unblock_sub> is L<EV> (but
		1024	you might still run into deadlocks if all event loops are blocked).
		1025
		1026	Coro will try to catch you when you block in the event loop
		1027	("FATAL: $Coro::idle blocked itself"), but this is just best effort and
		1028	only works when you do not run your own event loop.
690		1029
691	This function allows your callbacks to block by executing them in another	1030	This function allows your callbacks to block by executing them in another
692	coro where it is safe to block. One example where blocking is handy	1031	coro where it is safe to block. One example where blocking is handy
693	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	1032	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
694	disk, for example.	1033	disk, for example.
…		…
736	unshift @unblock_queue, [$cb, @_];	1075	unshift @unblock_queue, [$cb, @_];
737	$unblock_scheduler->ready;	1076	$unblock_scheduler->ready;
738	}	1077	}
739	}	1078	}
740		1079
741	=item $cb = Coro::rouse_cb	1080	=item $cb = rouse_cb
742		1081
743	Create and return a "rouse callback". That's a code reference that,	1082	Create and return a "rouse callback". That's a code reference that,
744	when called, will remember a copy of its arguments and notify the owner	1083	when called, will remember a copy of its arguments and notify the owner
745	coro of the callback.	1084	coro of the callback.
746		1085
747	See the next function.	1086	See the next function.
748		1087
749	=item @args = Coro::rouse_wait [$cb]	1088	=item @args = rouse_wait [$cb]
750		1089
751	Wait for the specified rouse callback (or the last one that was created in	1090	Wait for the specified rouse callback (or the last one that was created in
752	this coro).	1091	this coro).
753		1092
754	As soon as the callback is invoked (or when the callback was invoked	1093	As soon as the callback is invoked (or when the callback was invoked
…		…
761		1100
762	=back	1101	=back
763		1102
764	=cut	1103	=cut
765		1104
		1105	for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) {
		1106	my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"};
		1107
		1108	*{"Coro::$module\::new"} = sub {
		1109	require "Coro/$module.pm";
		1110
		1111	# some modules have their new predefined in State.xs, some don't
		1112	*{"Coro::$module\::new"} = $old
		1113	if $old;
		1114
		1115	goto &{"Coro::$module\::new"};
		1116	};
		1117	}
		1118
766	1;	1119	1;
767		1120
768	=head1 HOW TO WAIT FOR A CALLBACK	1121	=head1 HOW TO WAIT FOR A CALLBACK
769		1122
770	It is very common for a coro to wait for some callback to be	1123	It is very common for a coro to wait for some callback to be
771	called. This occurs naturally when you use coro in an otherwise	1124	called. This occurs naturally when you use coro in an otherwise
772	event-based program, or when you use event-based libraries.	1125	event-based program, or when you use event-based libraries.
773		1126
774	These typically register a callback for some event, and call that callback	1127	These typically register a callback for some event, and call that callback
775	when the event occured. In a coro, however, you typically want to	1128	when the event occurred. In a coro, however, you typically want to
776	just wait for the event, simplyifying things.	1129	just wait for the event, simplyifying things.
777		1130
778	For example C<< AnyEvent->child >> registers a callback to be called when	1131	For example C<< AnyEvent->child >> registers a callback to be called when
779	a specific child has exited:	1132	a specific child has exited:
780		1133
…		…
783	But from within a coro, you often just want to write this:	1136	But from within a coro, you often just want to write this:
784		1137
785	my $status = wait_for_child $pid;	1138	my $status = wait_for_child $pid;
786		1139
787	Coro offers two functions specifically designed to make this easy,	1140	Coro offers two functions specifically designed to make this easy,
788	C<Coro::rouse_cb> and C<Coro::rouse_wait>.	1141	C<rouse_cb> and C<rouse_wait>.
789		1142
790	The first function, C<rouse_cb>, generates and returns a callback that,	1143	The first function, C<rouse_cb>, generates and returns a callback that,
791	when invoked, will save its arguments and notify the coro that	1144	when invoked, will save its arguments and notify the coro that
792	created the callback.	1145	created the callback.
793		1146
…		…
799	function mentioned above:	1152	function mentioned above:
800		1153
801	sub wait_for_child($) {	1154	sub wait_for_child($) {
802	my ($pid) = @_;	1155	my ($pid) = @_;
803		1156
804	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);	1157	my $watcher = AnyEvent->child (pid => $pid, cb => rouse_cb);
805		1158
806	my ($rpid, $rstatus) = Coro::rouse_wait;	1159	my ($rpid, $rstatus) = rouse_wait;
807	$rstatus	1160	$rstatus
808	}	1161	}
809		1162
810	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,	1163	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
811	you can roll your own, using C<schedule>:	1164	you can roll your own, using C<schedule> and C<ready>:
812		1165
813	sub wait_for_child($) {	1166	sub wait_for_child($) {
814	my ($pid) = @_;	1167	my ($pid) = @_;
815		1168
816	# store the current coro in $current,	1169	# store the current coro in $current,
…		…
819	my ($done, $rstatus);	1172	my ($done, $rstatus);
820		1173
821	# pass a closure to ->child	1174	# pass a closure to ->child
822	my $watcher = AnyEvent->child (pid => $pid, cb => sub {	1175	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
823	$rstatus = $_[1]; # remember rstatus	1176	$rstatus = $_[1]; # remember rstatus
824	$done = 1; # mark $rstatus as valud	1177	$done = 1; # mark $rstatus as valid
		1178	$current->ready; # wake up the waiting thread
825	});	1179	});
826		1180
827	# wait until the closure has been called	1181	# wait until the closure has been called
828	schedule while !$done;	1182	schedule while !$done;
829		1183
…		…
849	future to allow per-thread schedulers, but Coro::State does not yet allow	1203	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	1204	this). I recommend disabling thread support and using processes, as having
851	the windows process emulation enabled under unix roughly halves perl	1205	the windows process emulation enabled under unix roughly halves perl
852	performance, even when not used.	1206	performance, even when not used.
853		1207
		1208	Attempts to use threads created in another emulated process will crash
		1209	("cleanly", with a null pointer exception).
		1210
854	=item coro switching is not signal safe	1211	=item coro switching is not signal safe
855		1212
856	You must not switch to another coro from within a signal handler	1213	You must not switch to another coro from within a signal handler (only
857	(only relevant with %SIG - most event libraries provide safe signals).	1214	relevant with %SIG - most event libraries provide safe signals), I<unless>
		1215	you are sure you are not interrupting a Coro function.
858		1216
859	That means you I<MUST NOT> call any function that might "block" the	1217	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	1218	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
861	anything that calls those. Everything else, including calling C<ready>,	1219	anything that calls those. Everything else, including calling C<ready>,
862	works.	1220	works.
863		1221
864	=back	1222	=back
865		1223
866		1224
		1225	=head1 WINDOWS PROCESS EMULATION
		1226
		1227	A great many people seem to be confused about ithreads (for example, Chip
		1228	Salzenberg called me unintelligent, incapable, stupid and gullible,
		1229	while in the same mail making rather confused statements about perl
		1230	ithreads (for example, that memory or files would be shared), showing his
		1231	lack of understanding of this area - if it is hard to understand for Chip,
		1232	it is probably not obvious to everybody).
		1233
		1234	What follows is an ultra-condensed version of my talk about threads in
		1235	scripting languages given on the perl workshop 2009:
		1236
		1237	The so-called "ithreads" were originally implemented for two reasons:
		1238	first, to (badly) emulate unix processes on native win32 perls, and
		1239	secondly, to replace the older, real thread model ("5.005-threads").
		1240
		1241	It does that by using threads instead of OS processes. The difference
		1242	between processes and threads is that threads share memory (and other
		1243	state, such as files) between threads within a single process, while
		1244	processes do not share anything (at least not semantically). That
		1245	means that modifications done by one thread are seen by others, while
		1246	modifications by one process are not seen by other processes.
		1247
		1248	The "ithreads" work exactly like that: when creating a new ithreads
		1249	process, all state is copied (memory is copied physically, files and code
		1250	is copied logically). Afterwards, it isolates all modifications. On UNIX,
		1251	the same behaviour can be achieved by using operating system processes,
		1252	except that UNIX typically uses hardware built into the system to do this
		1253	efficiently, while the windows process emulation emulates this hardware in
		1254	software (rather efficiently, but of course it is still much slower than
		1255	dedicated hardware).
		1256
		1257	As mentioned before, loading code, modifying code, modifying data
		1258	structures and so on is only visible in the ithreads process doing the
		1259	modification, not in other ithread processes within the same OS process.
		1260
		1261	This is why "ithreads" do not implement threads for perl at all, only
		1262	processes. What makes it so bad is that on non-windows platforms, you can
		1263	actually take advantage of custom hardware for this purpose (as evidenced
		1264	by the forks module, which gives you the (i-) threads API, just much
		1265	faster).
		1266
		1267	Sharing data is in the i-threads model is done by transferring data
		1268	structures between threads using copying semantics, which is very slow -
		1269	shared data simply does not exist. Benchmarks using i-threads which are
		1270	communication-intensive show extremely bad behaviour with i-threads (in
		1271	fact, so bad that Coro, which cannot take direct advantage of multiple
		1272	CPUs, is often orders of magnitude faster because it shares data using
		1273	real threads, refer to my talk for details).
		1274
		1275	As summary, i-threads use threads to implement processes, while
		1276	the compatible forks module uses processes to emulate, uhm,
		1277	processes. I-threads slow down every perl program when enabled, and
		1278	outside of windows, serve no (or little) practical purpose, but
		1279	disadvantages every single-threaded Perl program.
		1280
		1281	This is the reason that I try to avoid the name "ithreads", as it is
		1282	misleading as it implies that it implements some kind of thread model for
		1283	perl, and prefer the name "windows process emulation", which describes the
		1284	actual use and behaviour of it much better.
		1285
867	=head1 SEE ALSO	1286	=head1 SEE ALSO
868		1287
869	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.	1288	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
870		1289
871	Debugging: L<Coro::Debug>.	1290	Debugging: L<Coro::Debug>.
…		…
883		1302
884	XS API: L<Coro::MakeMaker>.	1303	XS API: L<Coro::MakeMaker>.
885		1304
886	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.	1305	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
887		1306
888	=head1 AUTHOR	1307	=head1 AUTHOR/SUPPORT/CONTACT
889		1308
890	Marc Lehmann <schmorp@schmorp.de>	1309	Marc A. Lehmann <schmorp@schmorp.de>
891	http://home.schmorp.de/	1310	http://software.schmorp.de/pkg/Coro.html
892		1311
893	=cut	1312	=cut
894		1313

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Revision 1.262 by root, Wed Jul 22 03:02:07 2009 UTC vs.
Revision 1.346 by root, Fri Jul 14 23:20:07 2017 UTC