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

Comparing Coro/Coro.pm (file contents):
Revision 1.251 by root, Mon Mar 16 22:22:12 2009 UTC vs.
Revision 1.337 by root, Sun Oct 4 13:10:22 2015 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 = 5.131;	371	our $VERSION = 6.48;
86		372
87	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	373	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
88	our %EXPORT_TAGS = (	374	our %EXPORT_TAGS = (
89	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	375	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
90	);	376	);
91	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	377	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
92		378
…		…
95	=over 4	381	=over 4
96		382
97	=item $Coro::main	383	=item $Coro::main
98		384
99	This variable stores the Coro object that represents the main	385	This variable stores the Coro object that represents the main
100	program. While you cna C<ready> it and do most other things you can do to	386	program. While you can C<ready> it and do most other things you can do to
101	coro, it is mainly useful to compare again C<$Coro::current>, to see	387	coro, it is mainly useful to compare again C<$Coro::current>, to see
102	whether you are running in the main program or not.	388	whether you are running in the main program or not.
103		389
104	=cut	390	=cut
105		391
…		…
123		409
124	This variable is mainly useful to integrate Coro into event loops. It is	410	This variable is mainly useful to integrate Coro into event loops. It is
125	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is	411	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
126	pretty low-level functionality.	412	pretty low-level functionality.
127		413
128	This variable stores either a Coro object or a callback.	414	This variable stores a Coro object that is put into the ready queue when
		415	there are no other ready threads (without invoking any ready hooks).
129		416
130	If it is a callback, the it is called whenever the scheduler finds no	417	The default implementation dies with "FATAL: deadlock detected.", followed
131	ready coros to run. The default implementation prints "FATAL:	418	by a thread listing, because the program has no other way to continue.
132	deadlock detected" and exits, because the program has no other way to
133	continue.
134
135	If it is a coro object, then this object will be readied (without
136	invoking any ready hooks, however) when the scheduler finds no other ready
137	coros to run.
138		419
139	This hook is overwritten by modules such as C<Coro::EV> and	420	This hook is overwritten by modules such as C<Coro::EV> and
140	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a	421	C<Coro::AnyEvent> to wait on an external event that hopefully wakes up a
141	coro so the scheduler can run it.	422	coro so the scheduler can run it.
142		423
143	Note that the callback I<must not>, under any circumstances, block
144	the current coro. Normally, this is achieved by having an "idle
145	coro" that calls the event loop and then blocks again, and then
146	readying that coro in the idle handler, or by simply placing the idle
147	coro in this variable.
148
149	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this	424	See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
150	technique.
151
152	Please note that if your callback recursively invokes perl (e.g. for event
153	handlers), then it must be prepared to be called recursively itself.
154		425
155	=cut	426	=cut
156		427
157	$idle = sub {	428	# \|\|= because other modules could have provided their own by now
158	require Carp;	429	$idle \|\|= new Coro sub {
159	Carp::croak ("FATAL: deadlock detected");	430	require Coro::Debug;
		431	die "FATAL: deadlock detected.\n"
		432	. Coro::Debug::ps_listing ();
160	};	433	};
161		434
162	# this coro is necessary because a coro	435	# this coro is necessary because a coro
163	# cannot destroy itself.	436	# cannot destroy itself.
164	our @destroy;	437	our @destroy;
165	our $manager;	438	our $manager;
166		439
167	$manager = new Coro sub {	440	$manager = new Coro sub {
168	while () {	441	while () {
169	Coro::State::cancel shift @destroy	442	_destroy shift @destroy
170	while @destroy;	443	while @destroy;
171		444
172	&schedule;	445	&schedule;
173	}	446	}
174	};	447	};
…		…
206	Example: Create a new coro that just prints its arguments.	479	Example: Create a new coro that just prints its arguments.
207		480
208	async {	481	async {
209	print "@_\n";	482	print "@_\n";
210	} 1,2,3,4;	483	} 1,2,3,4;
211
212	=cut
213
214	sub async(&@) {
215	my $coro = new Coro @_;
216	$coro->ready;
217	$coro
218	}
219		484
220	=item async_pool { ... } [@args...]	485	=item async_pool { ... } [@args...]
221		486
222	Similar to C<async>, but uses a coro pool, so you should not call	487	Similar to C<async>, but uses a coro pool, so you should not call
223	terminate or join on it (although you are allowed to), and you get a	488	terminate or join on it (although you are allowed to), and you get a
…		…
280	=item schedule	545	=item schedule
281		546
282	Calls the scheduler. The scheduler will find the next coro that is	547	Calls the scheduler. The scheduler will find the next coro that is
283	to be run from the ready queue and switches to it. The next coro	548	to be run from the ready queue and switches to it. The next coro
284	to be run is simply the one with the highest priority that is longest	549	to be run is simply the one with the highest priority that is longest
285	in its ready queue. If there is no coro ready, it will clal the	550	in its ready queue. If there is no coro ready, it will call the
286	C<$Coro::idle> hook.	551	C<$Coro::idle> hook.
287		552
288	Please note that the current coro will I<not> be put into the ready	553	Please note that the current coro will I<not> be put into the ready
289	queue, so calling this function usually means you will never be called	554	queue, so calling this function usually means you will never be called
290	again unless something else (e.g. an event handler) calls C<< ->ready >>,	555	again unless something else (e.g. an event handler) calls C<< ->ready >>,
…		…
316	coro, regardless of priority. This is useful sometimes to ensure	581	coro, regardless of priority. This is useful sometimes to ensure
317	progress is made.	582	progress is made.
318		583
319	=item terminate [arg...]	584	=item terminate [arg...]
320		585
321	Terminates the current coro with the given status values (see L<cancel>).	586	Terminates the current coro with the given status values (see
		587	L<cancel>). The values will not be copied, but referenced directly.
322		588
323	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK	589	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
324		590
325	These function install enter and leave winders in the current scope. The	591	These function install enter and leave winders in the current scope. The
326	enter block will be executed when on_enter is called and whenever the	592	enter block will be executed when on_enter is called and whenever the
…		…
338		604
339	These functions implement the same concept as C<dynamic-wind> in scheme	605	These functions implement the same concept as C<dynamic-wind> in scheme
340	does, and are useful when you want to localise some resource to a specific	606	does, and are useful when you want to localise some resource to a specific
341	coro.	607	coro.
342		608
343	They slow down coro switching considerably for coros that use	609	They slow down thread switching considerably for coros that use them
344	them (But coro switching is still reasonably fast if the handlers are	610	(about 40% for a BLOCK with a single assignment, so thread switching is
345	fast).	611	still reasonably fast if the handlers are fast).
346		612
347	These functions are best understood by an example: The following function	613	These functions are best understood by an example: The following function
348	will change the current timezone to "Antarctica/South_Pole", which	614	will change the current timezone to "Antarctica/South_Pole", which
349	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,	615	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
350	which remember/change the current timezone and restore the previous	616	which remember/change the current timezone and restore the previous
351	value, respectively, the timezone is only changes for the coro that	617	value, respectively, the timezone is only changed for the coro that
352	installed those handlers.	618	installed those handlers.
353		619
354	use POSIX qw(tzset);	620	use POSIX qw(tzset);
355		621
356	async {	622	async {
…		…
373	};	639	};
374		640
375	This can be used to localise about any resource (locale, uid, current	641	This can be used to localise about any resource (locale, uid, current
376	working directory etc.) to a block, despite the existance of other	642	working directory etc.) to a block, despite the existance of other
377	coros.	643	coros.
		644
		645	Another interesting example implements time-sliced multitasking using
		646	interval timers (this could obviously be optimised, but does the job):
		647
		648	# "timeslice" the given block
		649	sub timeslice(&) {
		650	use Time::HiRes ();
		651
		652	Coro::on_enter {
		653	# on entering the thread, we set an VTALRM handler to cede
		654	$SIG{VTALRM} = sub { cede };
		655	# and then start the interval timer
		656	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
		657	};
		658	Coro::on_leave {
		659	# on leaving the thread, we stop the interval timer again
		660	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
		661	};
		662
		663	&{+shift};
		664	}
		665
		666	# use like this:
		667	timeslice {
		668	# The following is an endless loop that would normally
		669	# monopolise the process. Since it runs in a timesliced
		670	# environment, it will regularly cede to other threads.
		671	while () { }
		672	};
		673
378		674
379	=item killall	675	=item killall
380		676
381	Kills/terminates/cancels all coros except the currently running one.	677	Kills/terminates/cancels all coros except the currently running one.
382		678
…		…
452	To avoid this, it is best to put a suspended coro into the ready queue	748	To avoid this, it is best to put a suspended coro into the ready queue
453	unconditionally, as every synchronisation mechanism must protect itself	749	unconditionally, as every synchronisation mechanism must protect itself
454	against spurious wakeups, and the one in the Coro family certainly do	750	against spurious wakeups, and the one in the Coro family certainly do
455	that.	751	that.
456		752
		753	=item $state->is_new
		754
		755	Returns true iff this Coro object is "new", i.e. has never been run
		756	yet. Those states basically consist of only the code reference to call and
		757	the arguments, but consumes very little other resources. New states will
		758	automatically get assigned a perl interpreter when they are transfered to.
		759
		760	=item $state->is_zombie
		761
		762	Returns true iff the Coro object has been cancelled, i.e.
		763	it's resources freed because they were C<cancel>'ed, C<terminate>'d,
		764	C<safe_cancel>'ed or simply went out of scope.
		765
		766	The name "zombie" stems from UNIX culture, where a process that has
		767	exited and only stores and exit status and no other resources is called a
		768	"zombie".
		769
457	=item $is_ready = $coro->is_ready	770	=item $is_ready = $coro->is_ready
458		771
459	Returns true iff the Coro object is in the ready queue. Unless the Coro	772	Returns true iff the Coro object is in the ready queue. Unless the Coro
460	object gets destroyed, it will eventually be scheduled by the scheduler.	773	object gets destroyed, it will eventually be scheduled by the scheduler.
461		774
…		…
470	Returns true iff this Coro object has been suspended. Suspended Coros will	783	Returns true iff this Coro object has been suspended. Suspended Coros will
471	not ever be scheduled.	784	not ever be scheduled.
472		785
473	=item $coro->cancel (arg...)	786	=item $coro->cancel (arg...)
474		787
475	Terminates the given Coro and makes it return the given arguments as	788	Terminates the given Coro thread and makes it return the given arguments as
476	status (default: the empty list). Never returns if the Coro is the	789	status (default: an empty list). Never returns if the Coro is the
477	current Coro.	790	current Coro.
478		791
479	=cut	792	This is a rather brutal way to free a coro, with some limitations - if
		793	the thread is inside a C callback that doesn't expect to be canceled,
		794	bad things can happen, or if the cancelled thread insists on running
		795	complicated cleanup handlers that rely on its thread context, things will
		796	not work.
480		797
481	sub cancel {	798	Any cleanup code being run (e.g. from C<guard> blocks, destructors and so
482	my $self = shift;	799	on) will be run without a thread context, and is not allowed to switch
		800	to other threads. A common mistake is to call C<< ->cancel >> from a
		801	destructor called by die'ing inside the thread to be cancelled for
		802	example.
483		803
484	if ($current == $self) {	804	On the plus side, C<< ->cancel >> will always clean up the thread, no
485	terminate @_;	805	matter what. If your cleanup code is complex or you want to avoid
486	} else {	806	cancelling a C-thread that doesn't know how to clean up itself, it can be
487	$self->{_status} = [@_];	807	better to C<< ->throw >> an exception, or use C<< ->safe_cancel >>.
488	Coro::State::cancel $self;	808
		809	The arguments to C<< ->cancel >> are not copied, but instead will
		810	be referenced directly (e.g. if you pass C<$var> and after the call
		811	change that variable, then you might change the return values passed to
		812	e.g. C<join>, so don't do that).
		813
		814	The resources of the Coro are usually freed (or destructed) before this
		815	call returns, but this can be delayed for an indefinite amount of time, as
		816	in some cases the manager thread has to run first to actually destruct the
		817	Coro object.
		818
		819	=item $coro->safe_cancel ($arg...)
		820
		821	Works mostly like C<< ->cancel >>, but is inherently "safer", and
		822	consequently, can fail with an exception in cases the thread is not in a
		823	cancellable state. Essentially, C<< ->safe_cancel >> is a C<< ->cancel >>
		824	with extra checks before canceling.
		825
		826	It works a bit like throwing an exception that cannot be caught -
		827	specifically, it will clean up the thread from within itself, so all
		828	cleanup handlers (e.g. C<guard> blocks) are run with full thread
		829	context and can block if they wish. The downside is that there is no
		830	guarantee that the thread can be cancelled when you call this method, and
		831	therefore, it might fail. It is also considerably slower than C<cancel> or
		832	C<terminate>.
		833
		834	A thread is in a safe-cancellable state if it either hasn't been run yet,
		835	or it has no C context attached and is inside an SLF function.
		836
		837	The latter two basically mean that the thread isn't currently inside a
		838	perl callback called from some C function (usually via some XS modules)
		839	and isn't currently executing inside some C function itself (via Coro's XS
		840	API).
		841
		842	This call returns true when it could cancel the thread, or croaks with an
		843	error otherwise (i.e. it either returns true or doesn't return at all).
		844
		845	Why the weird interface? Well, there are two common models on how and
		846	when to cancel things. In the first, you have the expectation that your
		847	coro thread can be cancelled when you want to cancel it - if the thread
		848	isn't cancellable, this would be a bug somewhere, so C<< ->safe_cancel >>
		849	croaks to notify of the bug.
		850
		851	In the second model you sometimes want to ask nicely to cancel a thread,
		852	but if it's not a good time, well, then don't cancel. This can be done
		853	relatively easy like this:
		854
		855	if (! eval { $coro->safe_cancel }) {
		856	warn "unable to cancel thread: $@";
489	}	857	}
490	}	858
		859	However, what you never should do is first try to cancel "safely" and
		860	if that fails, cancel the "hard" way with C<< ->cancel >>. That makes
		861	no sense: either you rely on being able to execute cleanup code in your
		862	thread context, or you don't. If you do, then C<< ->safe_cancel >> is the
		863	only way, and if you don't, then C<< ->cancel >> is always faster and more
		864	direct.
491		865
492	=item $coro->schedule_to	866	=item $coro->schedule_to
493		867
494	Puts the current coro to sleep (like C<Coro::schedule>), but instead	868	Puts the current coro to sleep (like C<Coro::schedule>), but instead
495	of continuing with the next coro from the ready queue, always switch to	869	of continuing with the next coro from the ready queue, always switch to
…		…
514	inside the coro at the next convenient point in time. Otherwise	888	inside the coro at the next convenient point in time. Otherwise
515	clears the exception object.	889	clears the exception object.
516		890
517	Coro will check for the exception each time a schedule-like-function	891	Coro will check for the exception each time a schedule-like-function
518	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down	892	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
519	>>, C<< Coro::Handle->readable >> and so on. Most of these functions	893	>>, C<< Coro::Handle->readable >> and so on. Most of those functions (all
520	detect this case and return early in case an exception is pending.	894	that are part of Coro itself) detect this case and return early in case an
		895	exception is pending.
521		896
522	The exception object will be thrown "as is" with the specified scalar in	897	The exception object will be thrown "as is" with the specified scalar in
523	C<$@>, i.e. if it is a string, no line number or newline will be appended	898	C<$@>, i.e. if it is a string, no line number or newline will be appended
524	(unlike with C<die>).	899	(unlike with C<die>).
525		900
526	This can be used as a softer means than C<cancel> to ask a coro to	901	This can be used as a softer means than either C<cancel> or C<safe_cancel
527	end itself, although there is no guarantee that the exception will lead to	902	>to ask a coro to end itself, although there is no guarantee that the
528	termination, and if the exception isn't caught it might well end the whole	903	exception will lead to termination, and if the exception isn't caught it
529	program.	904	might well end the whole program.
530		905
531	You might also think of C<throw> as being the moral equivalent of	906	You might also think of C<throw> as being the moral equivalent of
532	C<kill>ing a coro with a signal (in this case, a scalar).	907	C<kill>ing a coro with a signal (in this case, a scalar).
533		908
534	=item $coro->join	909	=item $coro->join
535		910
536	Wait until the coro terminates and return any values given to the	911	Wait until the coro terminates and return any values given to the
537	C<terminate> or C<cancel> functions. C<join> can be called concurrently	912	C<terminate> or C<cancel> functions. C<join> can be called concurrently
538	from multiple coro, and all will be resumed and given the status	913	from multiple threads, and all will be resumed and given the status
539	return once the C<$coro> terminates.	914	return once the C<$coro> terminates.
540		915
541	=cut
542
543	sub join {
544	my $self = shift;
545
546	unless ($self->{_status}) {
547	my $current = $current;
548
549	push @{$self->{_on_destroy}}, sub {
550	$current->ready;
551	undef $current;
552	};
553
554	&schedule while $current;
555	}
556
557	wantarray ? @{$self->{_status}} : $self->{_status}[0];
558	}
559
560	=item $coro->on_destroy (\&cb)	916	=item $coro->on_destroy (\&cb)
561		917
562	Registers a callback that is called when this coro gets destroyed,	918	Registers a callback that is called when this coro thread gets destroyed,
563	but before it is joined. The callback gets passed the terminate arguments,	919	that is, after it's resources have been freed but before it is joined. The
		920	callback gets passed the terminate/cancel arguments, if any, and I<must
564	if any, and I<must not> die, under any circumstances.	921	not> die, under any circumstances.
565		922
566	=cut	923	There can be any number of C<on_destroy> callbacks per coro, and there is
567		924	currently no way to remove a callback once added.
568	sub on_destroy {
569	my ($self, $cb) = @_;
570
571	push @{ $self->{_on_destroy} }, $cb;
572	}
573		925
574	=item $oldprio = $coro->prio ($newprio)	926	=item $oldprio = $coro->prio ($newprio)
575		927
576	Sets (or gets, if the argument is missing) the priority of the	928	Sets (or gets, if the argument is missing) the priority of the
577	coro. Higher priority coro get run before lower priority	929	coro thread. Higher priority coro get run before lower priority
578	coro. Priorities are small signed integers (currently -4 .. +3),	930	coros. Priorities are small signed integers (currently -4 .. +3),
579	that you can refer to using PRIO_xxx constants (use the import tag :prio	931	that you can refer to using PRIO_xxx constants (use the import tag :prio
580	to get then):	932	to get then):
581		933
582	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	934	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
583	3 > 1 > 0 > -1 > -3 > -4	935	3 > 1 > 0 > -1 > -3 > -4
584		936
585	# set priority to HIGH	937	# set priority to HIGH
586	current->prio (PRIO_HIGH);	938	current->prio (PRIO_HIGH);
587		939
588	The idle coro ($Coro::idle) always has a lower priority than any	940	The idle coro thread ($Coro::idle) always has a lower priority than any
589	existing coro.	941	existing coro.
590		942
591	Changing the priority of the current coro will take effect immediately,	943	Changing the priority of the current coro will take effect immediately,
592	but changing the priority of coro in the ready queue (but not	944	but changing the priority of a coro in the ready queue (but not running)
593	running) will only take effect after the next schedule (of that	945	will only take effect after the next schedule (of that coro). This is a
594	coro). This is a bug that will be fixed in some future version.	946	bug that will be fixed in some future version.
595		947
596	=item $newprio = $coro->nice ($change)	948	=item $newprio = $coro->nice ($change)
597		949
598	Similar to C<prio>, but subtract the given value from the priority (i.e.	950	Similar to C<prio>, but subtract the given value from the priority (i.e.
599	higher values mean lower priority, just as in unix).	951	higher values mean lower priority, just as in UNIX's nice command).
600		952
601	=item $olddesc = $coro->desc ($newdesc)	953	=item $olddesc = $coro->desc ($newdesc)
602		954
603	Sets (or gets in case the argument is missing) the description for this	955	Sets (or gets in case the argument is missing) the description for this
604	coro. This is just a free-form string you can associate with a	956	coro thread. This is just a free-form string you can associate with a
605	coro.	957	coro.
606		958
607	This method simply sets the C<< $coro->{desc} >> member to the given	959	This method simply sets the C<< $coro->{desc} >> member to the given
608	string. You can modify this member directly if you wish.	960	string. You can modify this member directly if you wish, and in fact, this
		961	is often preferred to indicate major processing states that can then be
		962	seen for example in a L<Coro::Debug> session:
		963
		964	sub my_long_function {
		965	local $Coro::current->{desc} = "now in my_long_function";
		966	...
		967	$Coro::current->{desc} = "my_long_function: phase 1";
		968	...
		969	$Coro::current->{desc} = "my_long_function: phase 2";
		970	...
		971	}
609		972
610	=cut	973	=cut
611		974
612	sub desc {	975	sub desc {
613	my $old = $_[0]{desc};	976	my $old = $_[0]{desc};
…		…
650	returning a new coderef. Unblocking means that calling the new coderef	1013	returning a new coderef. Unblocking means that calling the new coderef
651	will return immediately without blocking, returning nothing, while the	1014	will return immediately without blocking, returning nothing, while the
652	original code ref will be called (with parameters) from within another	1015	original code ref will be called (with parameters) from within another
653	coro.	1016	coro.
654		1017
655	The reason this function exists is that many event libraries (such as the	1018	The reason this function exists is that many event libraries (such as
656	venerable L<Event\|Event> module) are not thread-safe (a weaker form	1019	the venerable L<Event\|Event> module) are not thread-safe (a weaker form
657	of reentrancy). This means you must not block within event callbacks,	1020	of reentrancy). This means you must not block within event callbacks,
658	otherwise you might suffer from crashes or worse. The only event library	1021	otherwise you might suffer from crashes or worse. The only event library
659	currently known that is safe to use without C<unblock_sub> is L<EV>.	1022	currently known that is safe to use without C<unblock_sub> is L<EV> (but
		1023	you might still run into deadlocks if all event loops are blocked).
		1024
		1025	Coro will try to catch you when you block in the event loop
		1026	("FATAL: $Coro::idle blocked itself"), but this is just best effort and
		1027	only works when you do not run your own event loop.
660		1028
661	This function allows your callbacks to block by executing them in another	1029	This function allows your callbacks to block by executing them in another
662	coro where it is safe to block. One example where blocking is handy	1030	coro where it is safe to block. One example where blocking is handy
663	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	1031	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
664	disk, for example.	1032	disk, for example.
…		…
706	unshift @unblock_queue, [$cb, @_];	1074	unshift @unblock_queue, [$cb, @_];
707	$unblock_scheduler->ready;	1075	$unblock_scheduler->ready;
708	}	1076	}
709	}	1077	}
710		1078
711	=item $cb = Coro::rouse_cb	1079	=item $cb = rouse_cb
712		1080
713	Create and return a "rouse callback". That's a code reference that,	1081	Create and return a "rouse callback". That's a code reference that,
714	when called, will remember a copy of its arguments and notify the owner	1082	when called, will remember a copy of its arguments and notify the owner
715	coro of the callback.	1083	coro of the callback.
716		1084
717	See the next function.	1085	See the next function.
718		1086
719	=item @args = Coro::rouse_wait [$cb]	1087	=item @args = rouse_wait [$cb]
720		1088
721	Wait for the specified rouse callback (or the last one that was created in	1089	Wait for the specified rouse callback (or the last one that was created in
722	this coro).	1090	this coro).
723		1091
724	As soon as the callback is invoked (or when the callback was invoked	1092	As soon as the callback is invoked (or when the callback was invoked
725	before C<rouse_wait>), it will return the arguments originally passed to	1093	before C<rouse_wait>), it will return the arguments originally passed to
726	the rouse callback.	1094	the rouse callback. In scalar context, that means you get the I<last>
		1095	argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
		1096	statement at the end.
727		1097
728	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.	1098	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
729		1099
730	=back	1100	=back
731		1101
732	=cut	1102	=cut
		1103
		1104	for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) {
		1105	my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"};
		1106
		1107	*{"Coro::$module\::new"} = sub {
		1108	require "Coro/$module.pm";
		1109
		1110	# some modules have their new predefined in State.xs, some don't
		1111	*{"Coro::$module\::new"} = $old
		1112	if $old;
		1113
		1114	goto &{"Coro::$module\::new"};
		1115	};
		1116	}
733		1117
734	1;	1118	1;
735		1119
736	=head1 HOW TO WAIT FOR A CALLBACK	1120	=head1 HOW TO WAIT FOR A CALLBACK
737		1121
…		…
751	But from within a coro, you often just want to write this:	1135	But from within a coro, you often just want to write this:
752		1136
753	my $status = wait_for_child $pid;	1137	my $status = wait_for_child $pid;
754		1138
755	Coro offers two functions specifically designed to make this easy,	1139	Coro offers two functions specifically designed to make this easy,
756	C<Coro::rouse_cb> and C<Coro::rouse_wait>.	1140	C<rouse_cb> and C<rouse_wait>.
757		1141
758	The first function, C<rouse_cb>, generates and returns a callback that,	1142	The first function, C<rouse_cb>, generates and returns a callback that,
759	when invoked, will save its arguments and notify the coro that	1143	when invoked, will save its arguments and notify the coro that
760	created the callback.	1144	created the callback.
761		1145
…		…
767	function mentioned above:	1151	function mentioned above:
768		1152
769	sub wait_for_child($) {	1153	sub wait_for_child($) {
770	my ($pid) = @_;	1154	my ($pid) = @_;
771		1155
772	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);	1156	my $watcher = AnyEvent->child (pid => $pid, cb => rouse_cb);
773		1157
774	my ($rpid, $rstatus) = Coro::rouse_wait;	1158	my ($rpid, $rstatus) = rouse_wait;
775	$rstatus	1159	$rstatus
776	}	1160	}
777		1161
778	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,	1162	In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
779	you can roll your own, using C<schedule>:	1163	you can roll your own, using C<schedule> and C<ready>:
780		1164
781	sub wait_for_child($) {	1165	sub wait_for_child($) {
782	my ($pid) = @_;	1166	my ($pid) = @_;
783		1167
784	# store the current coro in $current,	1168	# store the current coro in $current,
…		…
787	my ($done, $rstatus);	1171	my ($done, $rstatus);
788		1172
789	# pass a closure to ->child	1173	# pass a closure to ->child
790	my $watcher = AnyEvent->child (pid => $pid, cb => sub {	1174	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
791	$rstatus = $_[1]; # remember rstatus	1175	$rstatus = $_[1]; # remember rstatus
792	$done = 1; # mark $rstatus as valud	1176	$done = 1; # mark $rstatus as valid
		1177	$current->ready; # wake up the waiting thread
793	});	1178	});
794		1179
795	# wait until the closure has been called	1180	# wait until the closure has been called
796	schedule while !$done;	1181	schedule while !$done;
797		1182
…		…
817	future to allow per-thread schedulers, but Coro::State does not yet allow	1202	future to allow per-thread schedulers, but Coro::State does not yet allow
818	this). I recommend disabling thread support and using processes, as having	1203	this). I recommend disabling thread support and using processes, as having
819	the windows process emulation enabled under unix roughly halves perl	1204	the windows process emulation enabled under unix roughly halves perl
820	performance, even when not used.	1205	performance, even when not used.
821		1206
		1207	Attempts to use threads created in another emulated process will crash
		1208	("cleanly", with a null pointer exception).
		1209
822	=item coro switching is not signal safe	1210	=item coro switching is not signal safe
823		1211
824	You must not switch to another coro from within a signal handler	1212	You must not switch to another coro from within a signal handler (only
825	(only relevant with %SIG - most event libraries provide safe signals).	1213	relevant with %SIG - most event libraries provide safe signals), I<unless>
		1214	you are sure you are not interrupting a Coro function.
826		1215
827	That means you I<MUST NOT> call any function that might "block" the	1216	That means you I<MUST NOT> call any function that might "block" the
828	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or	1217	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
829	anything that calls those. Everything else, including calling C<ready>,	1218	anything that calls those. Everything else, including calling C<ready>,
830	works.	1219	works.
831		1220
832	=back	1221	=back
833		1222
834		1223
		1224	=head1 WINDOWS PROCESS EMULATION
		1225
		1226	A great many people seem to be confused about ithreads (for example, Chip
		1227	Salzenberg called me unintelligent, incapable, stupid and gullible,
		1228	while in the same mail making rather confused statements about perl
		1229	ithreads (for example, that memory or files would be shared), showing his
		1230	lack of understanding of this area - if it is hard to understand for Chip,
		1231	it is probably not obvious to everybody).
		1232
		1233	What follows is an ultra-condensed version of my talk about threads in
		1234	scripting languages given on the perl workshop 2009:
		1235
		1236	The so-called "ithreads" were originally implemented for two reasons:
		1237	first, to (badly) emulate unix processes on native win32 perls, and
		1238	secondly, to replace the older, real thread model ("5.005-threads").
		1239
		1240	It does that by using threads instead of OS processes. The difference
		1241	between processes and threads is that threads share memory (and other
		1242	state, such as files) between threads within a single process, while
		1243	processes do not share anything (at least not semantically). That
		1244	means that modifications done by one thread are seen by others, while
		1245	modifications by one process are not seen by other processes.
		1246
		1247	The "ithreads" work exactly like that: when creating a new ithreads
		1248	process, all state is copied (memory is copied physically, files and code
		1249	is copied logically). Afterwards, it isolates all modifications. On UNIX,
		1250	the same behaviour can be achieved by using operating system processes,
		1251	except that UNIX typically uses hardware built into the system to do this
		1252	efficiently, while the windows process emulation emulates this hardware in
		1253	software (rather efficiently, but of course it is still much slower than
		1254	dedicated hardware).
		1255
		1256	As mentioned before, loading code, modifying code, modifying data
		1257	structures and so on is only visible in the ithreads process doing the
		1258	modification, not in other ithread processes within the same OS process.
		1259
		1260	This is why "ithreads" do not implement threads for perl at all, only
		1261	processes. What makes it so bad is that on non-windows platforms, you can
		1262	actually take advantage of custom hardware for this purpose (as evidenced
		1263	by the forks module, which gives you the (i-) threads API, just much
		1264	faster).
		1265
		1266	Sharing data is in the i-threads model is done by transfering data
		1267	structures between threads using copying semantics, which is very slow -
		1268	shared data simply does not exist. Benchmarks using i-threads which are
		1269	communication-intensive show extremely bad behaviour with i-threads (in
		1270	fact, so bad that Coro, which cannot take direct advantage of multiple
		1271	CPUs, is often orders of magnitude faster because it shares data using
		1272	real threads, refer to my talk for details).
		1273
		1274	As summary, i-threads use threads to implement processes, while
		1275	the compatible forks module uses processes to emulate, uhm,
		1276	processes. I-threads slow down every perl program when enabled, and
		1277	outside of windows, serve no (or little) practical purpose, but
		1278	disadvantages every single-threaded Perl program.
		1279
		1280	This is the reason that I try to avoid the name "ithreads", as it is
		1281	misleading as it implies that it implements some kind of thread model for
		1282	perl, and prefer the name "windows process emulation", which describes the
		1283	actual use and behaviour of it much better.
		1284
835	=head1 SEE ALSO	1285	=head1 SEE ALSO
836		1286
837	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.	1287	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
838		1288
839	Debugging: L<Coro::Debug>.	1289	Debugging: L<Coro::Debug>.
…		…
851		1301
852	XS API: L<Coro::MakeMaker>.	1302	XS API: L<Coro::MakeMaker>.
853		1303
854	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.	1304	Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
855		1305
856	=head1 AUTHOR	1306	=head1 AUTHOR/SUPPORT/CONTACT
857		1307
858	Marc Lehmann <schmorp@schmorp.de>	1308	Marc A. Lehmann <schmorp@schmorp.de>
859	http://home.schmorp.de/	1309	http://software.schmorp.de/pkg/Coro.html
860		1310
861	=cut	1311	=cut
862		1312

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Comparing Coro/Coro.pm (file contents): Revision 1.251 by root, Mon Mar 16 22:22:12 2009 UTC vs. Revision 1.337 by root, Sun Oct 4 13:10:22 2015 UTC

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Comparing Coro/Coro.pm (file contents):
Revision 1.251 by root, Mon Mar 16 22:22:12 2009 UTC vs.
Revision 1.337 by root, Sun Oct 4 13:10:22 2015 UTC