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

Comparing Coro/Coro.pm (file contents):
Revision 1.271 by root, Fri Oct 2 19:55:59 2009 UTC vs.
Revision 1.349 by root, Tue Aug 14 16:51:37 2018 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 (see section of same name for more	44	but only the windows process emulation (see section of same name for
46	details) ported to unix, and as such act as processes), Coro provides	45	more details) ported to UNIX, and as such act as processes), Coro
47	a full shared address space, which makes communication between threads	46	provides a full shared address space, which makes communication between
48	very easy. And Coro's threads are fast, too: disabling the Windows	47	threads very easy. And coro threads are fast, too: disabling the Windows
49	process emulation code in your perl and using Coro can easily result in	48	process emulation code in your perl and using Coro can easily result in
50	a two to four times speed increase for your programs. A parallel matrix	49	a two to four times speed increase for your programs. A parallel matrix
51	multiplication benchmark runs over 300 times faster on a single core than	50	multiplication benchmark (very communication-intensive) runs over 300
52	perl's pseudo-threads on a quad core using all four cores.	51	times faster on a single core than perls pseudo-threads on a quad core
		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 common::sense;	357	use common::sense;
…		…
81		366
82	our $idle; # idle handler	367	our $idle; # idle handler
83	our $main; # main coro	368	our $main; # main coro
84	our $current; # current coro	369	our $current; # current coro
85		370
86	our $VERSION = 5.2;	371	our $VERSION = 6.52;
87		372
88	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);	373	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
89	our %EXPORT_TAGS = (	374	our %EXPORT_TAGS = (
90	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)],
91	);	376	);
…		…
96	=over 4	381	=over 4
97		382
98	=item $Coro::main	383	=item $Coro::main
99		384
100	This variable stores the Coro object that represents the main	385	This variable stores the Coro object that represents the main
101	program. While you cna C<ready> it and do most other things you can do to	386	program. While you can C<ready> it and do most other things you can do to
102	coro, it is mainly useful to compare again C<$Coro::current>, to see	387	coro, it is mainly useful to compare again C<$Coro::current>, to see
103	whether you are running in the main program or not.	388	whether you are running in the main program or not.
104		389
105	=cut	390	=cut
106		391
…		…
131		416
132	The default implementation dies with "FATAL: deadlock detected.", followed	417	The default implementation dies with "FATAL: deadlock detected.", followed
133	by a thread listing, because the program has no other way to continue.	418	by a thread listing, because the program has no other way to continue.
134		419
135	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
136	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
137	coro so the scheduler can run it.	422	coro so the scheduler can run it.
138		423
139	See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.	424	See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
140		425
141	=cut	426	=cut
142		427
		428	# \|\|= because other modules could have provided their own by now
143	$idle = new Coro sub {	429	$idle \|\|= new Coro sub {
144	require Coro::Debug;	430	require Coro::Debug;
145	die "FATAL: deadlock detected.\n"	431	die "FATAL: deadlock detected.\n"
146	. Coro::Debug::ps_listing ();	432	. Coro::Debug::ps_listing ();
147	};	433	};
148		434
…		…
151	our @destroy;	437	our @destroy;
152	our $manager;	438	our $manager;
153		439
154	$manager = new Coro sub {	440	$manager = new Coro sub {
155	while () {	441	while () {
156	Coro::State::cancel shift @destroy	442	_destroy shift @destroy
157	while @destroy;	443	while @destroy;
158		444
159	&schedule;	445	&schedule;
160	}	446	}
161	};	447	};
…		…
212	C<async> does. As the coro is being reused, stuff like C<on_destroy>	498	C<async> does. As the coro is being reused, stuff like C<on_destroy>
213	will not work in the expected way, unless you call terminate or cancel,	499	will not work in the expected way, unless you call terminate or cancel,
214	which somehow defeats the purpose of pooling (but is fine in the	500	which somehow defeats the purpose of pooling (but is fine in the
215	exceptional case).	501	exceptional case).
216		502
217	The priority will be reset to C<0> after each run, tracing will be	503	The priority will be reset to C<0> after each run, all C<swap_sv> calls
218	disabled, the description will be reset and the default output filehandle	504	will be undone, tracing will be disabled, the description will be reset
219	gets restored, so you can change all these. Otherwise the coro will	505	and the default output filehandle gets restored, so you can change all
220	be re-used "as-is": most notably if you change other per-coro global	506	these. Otherwise the coro will be re-used "as-is": most notably if you
221	stuff such as C<$/> 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
222	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	>>.
223		510
224	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
225	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
226	coros as required.	513	coros as required.
227		514
…		…
295	coro, regardless of priority. This is useful sometimes to ensure	582	coro, regardless of priority. This is useful sometimes to ensure
296	progress is made.	583	progress is made.
297		584
298	=item terminate [arg...]	585	=item terminate [arg...]
299		586
300	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.
301		589
302	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK	590	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
303		591
304	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
305	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
…		…
350	# at this place, the timezone is Antarctica/South_Pole,	638	# at this place, the timezone is Antarctica/South_Pole,
351	# without disturbing the TZ of any other coro.	639	# without disturbing the TZ of any other coro.
352	};	640	};
353		641
354	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
355	working directory etc.) to a block, despite the existance of other	643	working directory etc.) to a block, despite the existence of other
356	coros.	644	coros.
357		645
358	Another interesting example implements time-sliced multitasking using	646	Another interesting example implements time-sliced multitasking using
359	interval timers (this could obviously be optimised, but does the job):	647	interval timers (this could obviously be optimised, but does the job):
360		648
…		…
365	Coro::on_enter {	653	Coro::on_enter {
366	# on entering the thread, we set an VTALRM handler to cede	654	# on entering the thread, we set an VTALRM handler to cede
367	$SIG{VTALRM} = sub { cede };	655	$SIG{VTALRM} = sub { cede };
368	# and then start the interval timer	656	# and then start the interval timer
369	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;	657	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
370	};	658	};
371	Coro::on_leave {	659	Coro::on_leave {
372	# on leaving the thread, we stop the interval timer again	660	# on leaving the thread, we stop the interval timer again
373	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;	661	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
374	};	662	};
375		663
376	&{+shift};	664	&{+shift};
377	}	665	}
378		666
379	# use like this:	667	# use like this:
380	timeslice {	668	timeslice {
381	# The following is an endless loop that would normally	669	# The following is an endless loop that would normally
382	# monopolise the process. Since it runs in a timesliced	670	# monopolise the process. Since it runs in a timesliced
383	# environment, it will regularly cede to other threads.	671	# environment, it will regularly cede to other threads.
384	while () { }	672	while () { }
385	};	673	};
386		674
387		675
388	=item killall	676	=item killall
389		677
390	Kills/terminates/cancels all coros except the currently running one.	678	Kills/terminates/cancels all coros except the currently running one.
…		…
461	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
462	unconditionally, as every synchronisation mechanism must protect itself	750	unconditionally, as every synchronisation mechanism must protect itself
463	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
464	that.	752	that.
465		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
466	=item $is_ready = $coro->is_ready	771	=item $is_ready = $coro->is_ready
467		772
468	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
469	object gets destroyed, it will eventually be scheduled by the scheduler.	774	object gets destroyed, it will eventually be scheduled by the scheduler.
470		775
…		…
477	=item $is_suspended = $coro->is_suspended	782	=item $is_suspended = $coro->is_suspended
478		783
479	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
480	not ever be scheduled.	785	not ever be scheduled.
481		786
482	=item $coro->cancel (arg...)	787	=item $coro->cancel ($arg...)
483		788
484	Terminates the given Coro and makes it return the given arguments as	789	Terminate the given Coro thread and make it return the given arguments as
485	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
486	current Coro.	791	current Coro.
487		792
488	=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.
489		798
490	sub cancel {	799	Any cleanup code being run (e.g. from C<guard> blocks, destructors and so
491	my $self = shift;	800	on) will be run without a thread context, and is not allowed to switch
		801	to other threads. A common mistake is to call C<< ->cancel >> from a
		802	destructor called by die'ing inside the thread to be cancelled for
		803	example.
492		804
493	if ($current == $self) {	805	On the plus side, C<< ->cancel >> will always clean up the thread, no
494	terminate @_;	806	matter what. If your cleanup code is complex or you want to avoid
495	} else {	807	cancelling a C-thread that doesn't know how to clean up itself, it can be
496	$self->{_status} = [@_];	808	better to C<< ->throw >> an exception, or use C<< ->safe_cancel >>.
497	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 has never been run
		836	yet, has already been canceled/terminated or otherwise destroyed, or has
		837	no C context attached and is inside an SLF function.
		838
		839	The first two states are trivial - a thread that hasnot started or has
		840	already finished is safe to cancel.
		841
		842	The last state basically means that the thread isn't currently inside a
		843	perl callback called from some C function (usually via some XS modules)
		844	and isn't currently executing inside some C function itself (via Coro's XS
		845	API).
		846
		847	This call returns true when it could cancel the thread, or croaks with an
		848	error otherwise (i.e. it either returns true or doesn't return at all).
		849
		850	Why the weird interface? Well, there are two common models on how and
		851	when to cancel things. In the first, you have the expectation that your
		852	coro thread can be cancelled when you want to cancel it - if the thread
		853	isn't cancellable, this would be a bug somewhere, so C<< ->safe_cancel >>
		854	croaks to notify of the bug.
		855
		856	In the second model you sometimes want to ask nicely to cancel a thread,
		857	but if it's not a good time, well, then don't cancel. This can be done
		858	relatively easy like this:
		859
		860	if (! eval { $coro->safe_cancel }) {
		861	warn "unable to cancel thread: $@";
498	}	862	}
499	}	863
		864	However, what you never should do is first try to cancel "safely" and
		865	if that fails, cancel the "hard" way with C<< ->cancel >>. That makes
		866	no sense: either you rely on being able to execute cleanup code in your
		867	thread context, or you don't. If you do, then C<< ->safe_cancel >> is the
		868	only way, and if you don't, then C<< ->cancel >> is always faster and more
		869	direct.
500		870
501	=item $coro->schedule_to	871	=item $coro->schedule_to
502		872
503	Puts the current coro to sleep (like C<Coro::schedule>), but instead	873	Puts the current coro to sleep (like C<Coro::schedule>), but instead
504	of continuing with the next coro from the ready queue, always switch to	874	of continuing with the next coro from the ready queue, always switch to
…		…
523	inside the coro at the next convenient point in time. Otherwise	893	inside the coro at the next convenient point in time. Otherwise
524	clears the exception object.	894	clears the exception object.
525		895
526	Coro will check for the exception each time a schedule-like-function	896	Coro will check for the exception each time a schedule-like-function
527	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down	897	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
528	>>, C<< Coro::Handle->readable >> and so on. Most of these functions	898	>>, C<< Coro::Handle->readable >> and so on. Most of those functions (all
529	detect this case and return early in case an exception is pending.	899	that are part of Coro itself) detect this case and return early in case an
		900	exception is pending.
530		901
531	The exception object will be thrown "as is" with the specified scalar in	902	The exception object will be thrown "as is" with the specified scalar in
532	C<$@>, i.e. if it is a string, no line number or newline will be appended	903	C<$@>, i.e. if it is a string, no line number or newline will be appended
533	(unlike with C<die>).	904	(unlike with C<die>).
534		905
535	This can be used as a softer means than C<cancel> to ask a coro to	906	This can be used as a softer means than either C<cancel> or C<safe_cancel
536	end itself, although there is no guarantee that the exception will lead to	907	>to ask a coro to end itself, although there is no guarantee that the
537	termination, and if the exception isn't caught it might well end the whole	908	exception will lead to termination, and if the exception isn't caught it
538	program.	909	might well end the whole program.
539		910
540	You might also think of C<throw> as being the moral equivalent of	911	You might also think of C<throw> as being the moral equivalent of
541	C<kill>ing a coro with a signal (in this case, a scalar).	912	C<kill>ing a coro with a signal (in this case, a scalar).
542		913
543	=item $coro->join	914	=item $coro->join
544		915
545	Wait until the coro terminates and return any values given to the	916	Wait until the coro terminates and return any values given to the
546	C<terminate> or C<cancel> functions. C<join> can be called concurrently	917	C<terminate> or C<cancel> functions. C<join> can be called concurrently
547	from multiple coro, and all will be resumed and given the status	918	from multiple threads, and all will be resumed and given the status
548	return once the C<$coro> terminates.	919	return once the C<$coro> terminates.
549		920
550	=cut
551
552	sub join {
553	my $self = shift;
554
555	unless ($self->{_status}) {
556	my $current = $current;
557
558	push @{$self->{_on_destroy}}, sub {
559	$current->ready;
560	undef $current;
561	};
562
563	&schedule while $current;
564	}
565
566	wantarray ? @{$self->{_status}} : $self->{_status}[0];
567	}
568
569	=item $coro->on_destroy (\&cb)	921	=item $coro->on_destroy (\&cb)
570		922
571	Registers a callback that is called when this coro gets destroyed,	923	Registers a callback that is called when this coro thread gets destroyed,
572	but before it is joined. The callback gets passed the terminate arguments,	924	that is, after it's resources have been freed but before it is joined. The
		925	callback gets passed the terminate/cancel arguments, if any, and I<must
573	if any, and I<must not> die, under any circumstances.	926	not> die, under any circumstances.
574		927
575	=cut	928	There can be any number of C<on_destroy> callbacks per coro, and there is
576		929	currently no way to remove a callback once added.
577	sub on_destroy {
578	my ($self, $cb) = @_;
579
580	push @{ $self->{_on_destroy} }, $cb;
581	}
582		930
583	=item $oldprio = $coro->prio ($newprio)	931	=item $oldprio = $coro->prio ($newprio)
584		932
585	Sets (or gets, if the argument is missing) the priority of the	933	Sets (or gets, if the argument is missing) the priority of the
586	coro. Higher priority coro get run before lower priority	934	coro thread. Higher priority coro get run before lower priority
587	coro. Priorities are small signed integers (currently -4 .. +3),	935	coros. Priorities are small signed integers (currently -4 .. +3),
588	that you can refer to using PRIO_xxx constants (use the import tag :prio	936	that you can refer to using PRIO_xxx constants (use the import tag :prio
589	to get then):	937	to get then):
590		938
591	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	939	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
592	3 > 1 > 0 > -1 > -3 > -4	940	3 > 1 > 0 > -1 > -3 > -4
593		941
594	# set priority to HIGH	942	# set priority to HIGH
595	current->prio (PRIO_HIGH);	943	current->prio (PRIO_HIGH);
596		944
597	The idle coro ($Coro::idle) always has a lower priority than any	945	The idle coro thread ($Coro::idle) always has a lower priority than any
598	existing coro.	946	existing coro.
599		947
600	Changing the priority of the current coro will take effect immediately,	948	Changing the priority of the current coro will take effect immediately,
601	but changing the priority of coro in the ready queue (but not	949	but changing the priority of a coro in the ready queue (but not running)
602	running) will only take effect after the next schedule (of that	950	will only take effect after the next schedule (of that coro). This is a
603	coro). This is a bug that will be fixed in some future version.	951	bug that will be fixed in some future version.
604		952
605	=item $newprio = $coro->nice ($change)	953	=item $newprio = $coro->nice ($change)
606		954
607	Similar to C<prio>, but subtract the given value from the priority (i.e.	955	Similar to C<prio>, but subtract the given value from the priority (i.e.
608	higher values mean lower priority, just as in unix).	956	higher values mean lower priority, just as in UNIX's nice command).
609		957
610	=item $olddesc = $coro->desc ($newdesc)	958	=item $olddesc = $coro->desc ($newdesc)
611		959
612	Sets (or gets in case the argument is missing) the description for this	960	Sets (or gets in case the argument is missing) the description for this
613	coro. This is just a free-form string you can associate with a	961	coro thread. This is just a free-form string you can associate with a
614	coro.	962	coro.
615		963
616	This method simply sets the C<< $coro->{desc} >> member to the given	964	This method simply sets the C<< $coro->{desc} >> member to the given
617	string. You can modify this member directly if you wish.	965	string. You can modify this member directly if you wish, and in fact, this
		966	is often preferred to indicate major processing states that can then be
		967	seen for example in a L<Coro::Debug> session:
		968
		969	sub my_long_function {
		970	local $Coro::current->{desc} = "now in my_long_function";
		971	...
		972	$Coro::current->{desc} = "my_long_function: phase 1";
		973	...
		974	$Coro::current->{desc} = "my_long_function: phase 2";
		975	...
		976	}
618		977
619	=cut	978	=cut
620		979
621	sub desc {	980	sub desc {
622	my $old = $_[0]{desc};	981	my $old = $_[0]{desc};
…		…
659	returning a new coderef. Unblocking means that calling the new coderef	1018	returning a new coderef. Unblocking means that calling the new coderef
660	will return immediately without blocking, returning nothing, while the	1019	will return immediately without blocking, returning nothing, while the
661	original code ref will be called (with parameters) from within another	1020	original code ref will be called (with parameters) from within another
662	coro.	1021	coro.
663		1022
664	The reason this function exists is that many event libraries (such as the	1023	The reason this function exists is that many event libraries (such as
665	venerable L<Event\|Event> module) are not thread-safe (a weaker form	1024	the venerable L<Event\|Event> module) are not thread-safe (a weaker form
666	of reentrancy). This means you must not block within event callbacks,	1025	of reentrancy). This means you must not block within event callbacks,
667	otherwise you might suffer from crashes or worse. The only event library	1026	otherwise you might suffer from crashes or worse. The only event library
668	currently known that is safe to use without C<unblock_sub> is L<EV>.	1027	currently known that is safe to use without C<unblock_sub> is L<EV> (but
		1028	you might still run into deadlocks if all event loops are blocked).
		1029
		1030	Coro will try to catch you when you block in the event loop
		1031	("FATAL: $Coro::idle blocked itself"), but this is just best effort and
		1032	only works when you do not run your own event loop.
669		1033
670	This function allows your callbacks to block by executing them in another	1034	This function allows your callbacks to block by executing them in another
671	coro where it is safe to block. One example where blocking is handy	1035	coro where it is safe to block. One example where blocking is handy
672	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	1036	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
673	disk, for example.	1037	disk, for example.
…		…
740		1104
741	=back	1105	=back
742		1106
743	=cut	1107	=cut
744		1108
		1109	for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) {
		1110	my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"};
		1111
		1112	*{"Coro::$module\::new"} = sub {
		1113	require "Coro/$module.pm";
		1114
		1115	# some modules have their new predefined in State.xs, some don't
		1116	*{"Coro::$module\::new"} = $old
		1117	if $old;
		1118
		1119	goto &{"Coro::$module\::new"};
		1120	};
		1121	}
		1122
745	1;	1123	1;
746		1124
747	=head1 HOW TO WAIT FOR A CALLBACK	1125	=head1 HOW TO WAIT FOR A CALLBACK
748		1126
749	It is very common for a coro to wait for some callback to be	1127	It is very common for a coro to wait for some callback to be
750	called. This occurs naturally when you use coro in an otherwise	1128	called. This occurs naturally when you use coro in an otherwise
751	event-based program, or when you use event-based libraries.	1129	event-based program, or when you use event-based libraries.
752		1130
753	These typically register a callback for some event, and call that callback	1131	These typically register a callback for some event, and call that callback
754	when the event occured. In a coro, however, you typically want to	1132	when the event occurred. In a coro, however, you typically want to
755	just wait for the event, simplyifying things.	1133	just wait for the event, simplyifying things.
756		1134
757	For example C<< AnyEvent->child >> registers a callback to be called when	1135	For example C<< AnyEvent->child >> registers a callback to be called when
758	a specific child has exited:	1136	a specific child has exited:
759		1137
…		…
762	But from within a coro, you often just want to write this:	1140	But from within a coro, you often just want to write this:
763		1141
764	my $status = wait_for_child $pid;	1142	my $status = wait_for_child $pid;
765		1143
766	Coro offers two functions specifically designed to make this easy,	1144	Coro offers two functions specifically designed to make this easy,
767	C<Coro::rouse_cb> and C<Coro::rouse_wait>.	1145	C<rouse_cb> and C<rouse_wait>.
768		1146
769	The first function, C<rouse_cb>, generates and returns a callback that,	1147	The first function, C<rouse_cb>, generates and returns a callback that,
770	when invoked, will save its arguments and notify the coro that	1148	when invoked, will save its arguments and notify the coro that
771	created the callback.	1149	created the callback.
772		1150
…		…
778	function mentioned above:	1156	function mentioned above:
779		1157
780	sub wait_for_child($) {	1158	sub wait_for_child($) {
781	my ($pid) = @_;	1159	my ($pid) = @_;
782		1160
783	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);	1161	my $watcher = AnyEvent->child (pid => $pid, cb => rouse_cb);
784		1162
785	my ($rpid, $rstatus) = Coro::rouse_wait;	1163	my ($rpid, $rstatus) = rouse_wait;
786	$rstatus	1164	$rstatus
787	}	1165	}
788		1166
789	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,	1167	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
790	you can roll your own, using C<schedule>:	1168	you can roll your own, using C<schedule> and C<ready>:
791		1169
792	sub wait_for_child($) {	1170	sub wait_for_child($) {
793	my ($pid) = @_;	1171	my ($pid) = @_;
794		1172
795	# store the current coro in $current,	1173	# store the current coro in $current,
…		…
798	my ($done, $rstatus);	1176	my ($done, $rstatus);
799		1177
800	# pass a closure to ->child	1178	# pass a closure to ->child
801	my $watcher = AnyEvent->child (pid => $pid, cb => sub {	1179	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
802	$rstatus = $_[1]; # remember rstatus	1180	$rstatus = $_[1]; # remember rstatus
803	$done = 1; # mark $rstatus as valud	1181	$done = 1; # mark $rstatus as valid
		1182	$current->ready; # wake up the waiting thread
804	});	1183	});
805		1184
806	# wait until the closure has been called	1185	# wait until the closure has been called
807	schedule while !$done;	1186	schedule while !$done;
808		1187
…		…
828	future to allow per-thread schedulers, but Coro::State does not yet allow	1207	future to allow per-thread schedulers, but Coro::State does not yet allow
829	this). I recommend disabling thread support and using processes, as having	1208	this). I recommend disabling thread support and using processes, as having
830	the windows process emulation enabled under unix roughly halves perl	1209	the windows process emulation enabled under unix roughly halves perl
831	performance, even when not used.	1210	performance, even when not used.
832		1211
		1212	Attempts to use threads created in another emulated process will crash
		1213	("cleanly", with a null pointer exception).
		1214
833	=item coro switching is not signal safe	1215	=item coro switching is not signal safe
834		1216
835	You must not switch to another coro from within a signal handler	1217	You must not switch to another coro from within a signal handler (only
836	(only relevant with %SIG - most event libraries provide safe signals).	1218	relevant with %SIG - most event libraries provide safe signals), I<unless>
		1219	you are sure you are not interrupting a Coro function.
837		1220
838	That means you I<MUST NOT> call any function that might "block" the	1221	That means you I<MUST NOT> call any function that might "block" the
839	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or	1222	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
840	anything that calls those. Everything else, including calling C<ready>,	1223	anything that calls those. Everything else, including calling C<ready>,
841	works.	1224	works.
…		…
851	ithreads (for example, that memory or files would be shared), showing his	1234	ithreads (for example, that memory or files would be shared), showing his
852	lack of understanding of this area - if it is hard to understand for Chip,	1235	lack of understanding of this area - if it is hard to understand for Chip,
853	it is probably not obvious to everybody).	1236	it is probably not obvious to everybody).
854		1237
855	What follows is an ultra-condensed version of my talk about threads in	1238	What follows is an ultra-condensed version of my talk about threads in
856	scripting languages given onthe perl workshop 2009:	1239	scripting languages given on the perl workshop 2009:
857		1240
858	The so-called "ithreads" were originally implemented for two reasons:	1241	The so-called "ithreads" were originally implemented for two reasons:
859	first, to (badly) emulate unix processes on native win32 perls, and	1242	first, to (badly) emulate unix processes on native win32 perls, and
860	secondly, to replace the older, real thread model ("5.005-threads").	1243	secondly, to replace the older, real thread model ("5.005-threads").
861		1244
…		…
883	processes. What makes it so bad is that on non-windows platforms, you can	1266	processes. What makes it so bad is that on non-windows platforms, you can
884	actually take advantage of custom hardware for this purpose (as evidenced	1267	actually take advantage of custom hardware for this purpose (as evidenced
885	by the forks module, which gives you the (i-) threads API, just much	1268	by the forks module, which gives you the (i-) threads API, just much
886	faster).	1269	faster).
887		1270
888	Sharing data is in the i-threads model is done by transfering data	1271	Sharing data is in the i-threads model is done by transferring data
889	structures between threads using copying semantics, which is very slow -	1272	structures between threads using copying semantics, which is very slow -
890	shared data simply does not exist. Benchmarks using i-threads which are	1273	shared data simply does not exist. Benchmarks using i-threads which are
891	communication-intensive show extremely bad behaviour with i-threads (in	1274	communication-intensive show extremely bad behaviour with i-threads (in
892	fact, so bad that Coro, which cannot take direct advantage of multiple	1275	fact, so bad that Coro, which cannot take direct advantage of multiple
893	CPUs, is often orders of magnitude faster because it shares data using	1276	CPUs, is often orders of magnitude faster because it shares data using
…		…
923		1306
924	XS API: L<Coro::MakeMaker>.	1307	XS API: L<Coro::MakeMaker>.
925		1308
926	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.	1309	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
927		1310
928	=head1 AUTHOR	1311	=head1 AUTHOR/SUPPORT/CONTACT
929		1312
930	Marc Lehmann <schmorp@schmorp.de>	1313	Marc A. Lehmann <schmorp@schmorp.de>
931	http://home.schmorp.de/	1314	http://software.schmorp.de/pkg/Coro.html
932		1315
933	=cut	1316	=cut
934		1317

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing Coro/Coro.pm (file contents): Revision 1.271 by root, Fri Oct 2 19:55:59 2009 UTC vs. Revision 1.349 by root, Tue Aug 14 16:51:37 2018 UTC

Diff Legend

Comparing Coro/Coro.pm (file contents):
Revision 1.271 by root, Fri Oct 2 19:55:59 2009 UTC vs.
Revision 1.349 by root, Tue Aug 14 16:51:37 2018 UTC