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

Comparing cvsroot/Coro/Coro.pm (file contents):
Revision 1.248 by root, Mon Dec 15 15:03:31 2008 UTC vs.
Revision 1.295 by root, Tue May 10 19:55:48 2011 UTC

…		…
40	points in your program, so locking and parallel access are rarely an	40	points in your program, so locking and parallel access are rarely an
41	issue, making thread programming much safer and easier than using other	41	issue, making thread programming much safer and easier than using other
42	thread models.	42	thread models.
43		43
44	Unlike the so-called "Perl threads" (which are not actually real threads	44	Unlike the so-called "Perl threads" (which are not actually real threads
45	but only the windows process emulation ported to unix), Coro provides a	45	but only the windows process emulation (see section of same name for
		46	more details) ported to UNIX, and as such act as processes), Coro
46	full shared address space, which makes communication between threads	47	provides a full shared address space, which makes communication between
47	very easy. And threads are fast, too: disabling the Windows process	48	threads very easy. And coro threads are fast, too: disabling the Windows
48	emulation code in your perl and using Coro can easily result in a two to	49	process emulation code in your perl and using Coro can easily result in
49	four times speed increase for your programs.	50	a two to four times speed increase for your programs. A parallel matrix
		51	multiplication benchmark (very communication-intensive) runs over 300
		52	times faster on a single core than perls pseudo-threads on a quad core
		53	using all four cores.
50		54
51	Coro achieves that by supporting multiple running interpreters that share	55	Coro achieves that by supporting multiple running interpreters that share
52	data, which is especially useful to code pseudo-parallel processes and	56	data, which is especially useful to code pseudo-parallel processes and
53	for event-based programming, such as multiple HTTP-GET requests running	57	for event-based programming, such as multiple HTTP-GET requests running
54	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro	58	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
55	into an event-based environment.	59	into an event-based environment.
56		60
57	In this module, a thread is defined as "callchain + lexical variables +	61	In this module, a thread is defined as "callchain + lexical variables +
58	@_ + $_ + $@ + $/ + C stack), that is, a thread has its own callchain,	62	some package variables + C stack), that is, a thread has its own callchain,
59	its own set of lexicals and its own set of perls most important global	63	its own set of lexicals and its own set of perls most important global
60	variables (see L<Coro::State> for more configuration and background info).	64	variables (see L<Coro::State> for more configuration and background info).
61		65
62	See also the C<SEE ALSO> section at the end of this document - the Coro	66	See also the C<SEE ALSO> section at the end of this document - the Coro
63	module family is quite large.	67	module family is quite large.
64		68
		69	=head1 CORO THREAD LIFE CYCLE
		70
		71	During the long and exciting (or not) life of a coro thread, it goes
		72	through a number of states:
		73
		74	=over 4
		75
		76	=item 1. Creation
		77
		78	The first thing in the life of a coro thread is it's creation -
		79	obviously. The typical way to create a thread is to call the C<async
		80	BLOCK> function:
		81
		82	async {
		83	# thread code goes here
		84	};
		85
		86	You can also pass arguments, which are put in C<@_>:
		87
		88	async {
		89	print $_[1]; # prints 2
		90	} 1, 2, 3;
		91
		92	This creates a new coro thread and puts it into the ready queue, meaning
		93	it will run as soon as the CPU is free for it.
		94
		95	C<async> will return a coro object - you can store this for future
		96	reference or ignore it, the thread itself will keep a reference to it's
		97	thread object - threads are alive on their own.
		98
		99	Another way to create a thread is to call the C<new> constructor with a
		100	code-reference:
		101
		102	new Coro sub {
		103	# thread code goes here
		104	}, @optional_arguments;
		105
		106	This is quite similar to calling C<async>, but the important difference is
		107	that the new thread is not put into the ready queue, so the thread will
		108	not run until somebody puts it there. C<async> is, therefore, identical to
		109	this sequence:
		110
		111	my $coro = new Coro sub {
		112	# thread code goes here
		113	};
		114	$coro->ready;
		115	return $coro;
		116
		117	=item 2. Startup
		118
		119	When a new coro thread is created, only a copy of the code reference
		120	and the arguments are stored, no extra memory for stacks and so on is
		121	allocated, keeping the coro thread in a low-memory state.
		122
		123	Only when it actually starts executing will all the resources be finally
		124	allocated.
		125
		126	The optional arguments specified at coro creation are available in C<@_>,
		127	similar to function calls.
		128
		129	=item 3. Running / Blocking
		130
		131	A lot can happen after the coro thread has started running. Quite usually,
		132	it will not run to the end in one go (because you could use a function
		133	instead), but it will give up the CPU regularly because it waits for
		134	external events.
		135
		136	As long as a coro thread runs, it's coro object is available in the global
		137	variable C<$Coro::current>.
		138
		139	The low-level way to give up the CPU is to call the scheduler, which
		140	selects a new coro thread to run:
		141
		142	Coro::schedule;
		143
		144	Since running threads are not in the ready queue, calling the scheduler
		145	without doing anything else will block the coro thread forever - you need
		146	to arrange either for the coro to put woken up (readied) by some other
		147	event or some other thread, or you can put it into the ready queue before
		148	scheduling:
		149
		150	# this is exactly what Coro::cede does
		151	$Coro::current->ready;
		152	Coro::schedule;
		153
		154	All the higher-level synchronisation methods (Coro::Semaphore,
		155	Coro::rouse_*...) are actually implemented via C<< ->ready >> and C<<
		156	Coro::schedule >>.
		157
		158	While the coro thread is running it also might get assigned a C-level
		159	thread, or the C-level thread might be unassigned from it, as the Coro
		160	runtime wishes. A C-level thread needs to be assigned when your perl
		161	thread calls into some C-level function and that function in turn calls
		162	perl and perl then wants to switch coroutines. This happens most often
		163	when you run an event loop and block in the callback, or when perl
		164	itself calls some function such as C<AUTOLOAD> or methods via the C<tie>
		165	mechanism.
		166
		167	=item 4. Termination
		168
		169	Many threads actually terminate after some time. There are a number of
		170	ways to terminate a coro thread, the simplest is returning from the
		171	top-level code reference:
		172
		173	async {
		174	# after returning from here, the coro thread is terminated
		175	};
		176
		177	async {
		178	return if 0.5 < rand; # terminate a little earlier, maybe
		179	print "got a chance to print this\n";
		180	# or here
		181	};
		182
		183	Any values returned from the coroutine can be recovered using C<< ->join
		184	>>:
		185
		186	my $coro = async {
		187	"hello, world\n" # return a string
		188	};
		189
		190	my $hello_world = $coro->join;
		191
		192	print $hello_world;
		193
		194	Another way to terminate is to call C<< Coro::terminate >>, which at any
		195	subroutine call nesting level:
		196
		197	async {
		198	Coro::terminate "return value 1", "return value 2";
		199	};
		200
		201	And yet another way is to C<< ->cancel >> (or C<< ->safe_cancel >>) the
		202	coro thread from another thread:
		203
		204	my $coro = async {
		205	exit 1;
		206	};
		207
		208	$coro->cancel; # also accepts values for ->join to retrieve
		209
		210	Cancellation I<can> be dangerous - it's a bit like calling C<exit> without
		211	actually exiting, and might leave C libraries and XS modules in a weird
		212	state. Unlike other thread implementations, however, Coro is exceptionally
		213	safe with regards to cancellation, as perl will always be in a consistent
		214	state, and for those cases where you want to do truly marvellous things
		215	with your coro while it is being cancelled - that is, make sure all
		216	cleanup code is executed from the thread being cancelled - there is even a
		217	C<< ->safe_cancel >> method.
		218
		219	So, cancelling a thread that runs in an XS event loop might not be the
		220	best idea, but any other combination that deals with perl only (cancelling
		221	when a thread is in a C<tie> method or an C<AUTOLOAD> for example) is
		222	safe.
		223
		224	=item 5. Cleanup
		225
		226	Threads will allocate various resources. Most but not all will be returned
		227	when a thread terminates, during clean-up.
		228
		229	Cleanup is quite similar to throwing an uncaught exception: perl will
		230	work it's way up through all subroutine calls and blocks. On it's way, it
		231	will release all C<my> variables, undo all C<local>'s and free any other
		232	resources truly local to the thread.
		233
		234	So, a common way to free resources is to keep them referenced only by my
		235	variables:
		236
		237	async {
		238	my $big_cache = new Cache ...;
		239	};
		240
		241	If there are no other references, then the C<$big_cache> object will be
		242	freed when the thread terminates, regardless of how it does so.
		243
		244	What it does C<NOT> do is unlock any Coro::Semaphores or similar
		245	resources, but that's where the C<guard> methods come in handy:
		246
		247	my $sem = new Coro::Semaphore;
		248
		249	async {
		250	my $lock_guard = $sem->guard;
		251	# if we reutrn, or die or get cancelled, here,
		252	# then the semaphore will be "up"ed.
		253	};
		254
		255	The C<Guard::guard> function comes in handy for any custom cleanup you
		256	might want to do:
		257
		258	async {
		259	my $window = new Gtk2::Window "toplevel";
		260	# The window will not be cleaned up automatically, even when $window
		261	# gets freed, so use a guard to ensure it's destruction
		262	# in case of an error:
		263	my $window_guard = Guard::guard { $window->destroy };
		264
		265	# we are safe here
		266	};
		267
		268	Last not least, C<local> can often be handy, too, e.g. when temporarily
		269	replacing the coro thread description:
		270
		271	sub myfunction {
		272	local $Coro::current->{desc} = "inside myfunction(@_)";
		273
		274	# if we return or die here, the description will be restored
		275	}
		276
		277	=item 6. Viva La Zombie Muerte
		278
		279	Even after a thread has terminated and cleaned up it's resources, the coro
		280	object still is there and stores the return values of the thread. Only in
		281	this state will the coro object be "reference counted" in the normal perl
		282	sense: the thread code keeps a reference to it when it is active, but not
		283	after it has terminated.
		284
		285	The means the coro object gets freed automatically when the thread has
		286	terminated and cleaned up and there arenot other references.
		287
		288	If there are, the coro object will stay around, and you can call C<<
		289	->join >> as many times as you wish to retrieve the result values:
		290
		291	async {
		292	print "hi\n";
		293	1
		294	};
		295
		296	# run the async above, and free everything before returning
		297	# from Coro::cede:
		298	Coro::cede;
		299
		300	{
		301	my $coro = async {
		302	print "hi\n";
		303	1
		304	};
		305
		306	# run the async above, and clean up, but do not free the coro
		307	# object:
		308	Coro::cede;
		309
		310	# optionally retrieve the result values
		311	my @results = $coro->join;
		312
		313	# now $coro goes out of scope, and presumably gets freed
		314	};
		315
		316	=back
		317
65	=cut	318	=cut
66		319
67	package Coro;	320	package Coro;
68		321
69	use strict qw(vars subs);	322	use common::sense;
70	no warnings "uninitialized";	323
		324	use Carp ();
71		325
72	use Guard ();	326	use Guard ();
73		327
74	use Coro::State;	328	use Coro::State;
75		329
…		…
77		331
78	our $idle; # idle handler	332	our $idle; # idle handler
79	our $main; # main coro	333	our $main; # main coro
80	our $current; # current coro	334	our $current; # current coro
81		335
82	our $VERSION = 5.13;	336	our $VERSION = 5.372;
83		337
84	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	338	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
85	our %EXPORT_TAGS = (	339	our %EXPORT_TAGS = (
86	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	340	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
87	);	341	);
88	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	342	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
89		343
…		…
120		374
121	This variable is mainly useful to integrate Coro into event loops. It is	375	This variable is mainly useful to integrate Coro into event loops. It is
122	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is	376	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
123	pretty low-level functionality.	377	pretty low-level functionality.
124		378
125	This variable stores either a Coro object or a callback.	379	This variable stores a Coro object that is put into the ready queue when
		380	there are no other ready threads (without invoking any ready hooks).
126		381
127	If it is a callback, the it is called whenever the scheduler finds no	382	The default implementation dies with "FATAL: deadlock detected.", followed
128	ready coros to run. The default implementation prints "FATAL:	383	by a thread listing, because the program has no other way to continue.
129	deadlock detected" and exits, because the program has no other way to
130	continue.
131
132	If it is a coro object, then this object will be readied (without
133	invoking any ready hooks, however) when the scheduler finds no other ready
134	coros to run.
135		384
136	This hook is overwritten by modules such as C<Coro::EV> and	385	This hook is overwritten by modules such as C<Coro::EV> and
137	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a	386	C<Coro::AnyEvent> to wait on an external event that hopefully wakes up a
138	coro so the scheduler can run it.	387	coro so the scheduler can run it.
139		388
140	Note that the callback I<must not>, under any circumstances, block
141	the current coro. Normally, this is achieved by having an "idle
142	coro" that calls the event loop and then blocks again, and then
143	readying that coro in the idle handler, or by simply placing the idle
144	coro in this variable.
145
146	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this	389	See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
147	technique.
148		390
149	Please note that if your callback recursively invokes perl (e.g. for event
150	handlers), then it must be prepared to be called recursively itself.
151
152	=cut	391	=cut
153		392
154	$idle = sub {	393	# \|\|= because other modules could have provided their own by now
155	require Carp;	394	$idle \|\|= new Coro sub {
156	Carp::croak ("FATAL: deadlock detected");	395	require Coro::Debug;
		396	die "FATAL: deadlock detected.\n"
		397	. Coro::Debug::ps_listing ();
157	};	398	};
158		399
159	# this coro is necessary because a coro	400	# this coro is necessary because a coro
160	# cannot destroy itself.	401	# cannot destroy itself.
161	our @destroy;	402	our @destroy;
162	our $manager;	403	our $manager;
163		404
164	$manager = new Coro sub {	405	$manager = new Coro sub {
165	while () {	406	while () {
166	Coro::State::cancel shift @destroy	407	_destroy shift @destroy
167	while @destroy;	408	while @destroy;
168		409
169	&schedule;	410	&schedule;
170	}	411	}
171	};	412	};
…		…
203	Example: Create a new coro that just prints its arguments.	444	Example: Create a new coro that just prints its arguments.
204		445
205	async {	446	async {
206	print "@_\n";	447	print "@_\n";
207	} 1,2,3,4;	448	} 1,2,3,4;
208
209	=cut
210
211	sub async(&@) {
212	my $coro = new Coro @_;
213	$coro->ready;
214	$coro
215	}
216		449
217	=item async_pool { ... } [@args...]	450	=item async_pool { ... } [@args...]
218		451
219	Similar to C<async>, but uses a coro pool, so you should not call	452	Similar to C<async>, but uses a coro pool, so you should not call
220	terminate or join on it (although you are allowed to), and you get a	453	terminate or join on it (although you are allowed to), and you get a
…		…
277	=item schedule	510	=item schedule
278		511
279	Calls the scheduler. The scheduler will find the next coro that is	512	Calls the scheduler. The scheduler will find the next coro that is
280	to be run from the ready queue and switches to it. The next coro	513	to be run from the ready queue and switches to it. The next coro
281	to be run is simply the one with the highest priority that is longest	514	to be run is simply the one with the highest priority that is longest
282	in its ready queue. If there is no coro ready, it will clal the	515	in its ready queue. If there is no coro ready, it will call the
283	C<$Coro::idle> hook.	516	C<$Coro::idle> hook.
284		517
285	Please note that the current coro will I<not> be put into the ready	518	Please note that the current coro will I<not> be put into the ready
286	queue, so calling this function usually means you will never be called	519	queue, so calling this function usually means you will never be called
287	again unless something else (e.g. an event handler) calls C<< ->ready >>,	520	again unless something else (e.g. an event handler) calls C<< ->ready >>,
…		…
313	coro, regardless of priority. This is useful sometimes to ensure	546	coro, regardless of priority. This is useful sometimes to ensure
314	progress is made.	547	progress is made.
315		548
316	=item terminate [arg...]	549	=item terminate [arg...]
317		550
318	Terminates the current coro with the given status values (see L<cancel>).	551	Terminates the current coro with the given status values (see
		552	L<cancel>). The values will not be copied, but referenced directly.
319		553
320	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK	554	=item Coro::on_enter BLOCK, Coro::on_leave BLOCK
321		555
322	These function install enter and leave winders in the current scope. The	556	These function install enter and leave winders in the current scope. The
323	enter block will be executed when on_enter is called and whenever the	557	enter block will be executed when on_enter is called and whenever the
…		…
335		569
336	These functions implement the same concept as C<dynamic-wind> in scheme	570	These functions implement the same concept as C<dynamic-wind> in scheme
337	does, and are useful when you want to localise some resource to a specific	571	does, and are useful when you want to localise some resource to a specific
338	coro.	572	coro.
339		573
340	They slow down coro switching considerably for coros that use	574	They slow down thread switching considerably for coros that use them
341	them (But coro switching is still reasonably fast if the handlers are	575	(about 40% for a BLOCK with a single assignment, so thread switching is
342	fast).	576	still reasonably fast if the handlers are fast).
343		577
344	These functions are best understood by an example: The following function	578	These functions are best understood by an example: The following function
345	will change the current timezone to "Antarctica/South_Pole", which	579	will change the current timezone to "Antarctica/South_Pole", which
346	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,	580	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
347	which remember/change the current timezone and restore the previous	581	which remember/change the current timezone and restore the previous
348	value, respectively, the timezone is only changes for the coro that	582	value, respectively, the timezone is only changed for the coro that
349	installed those handlers.	583	installed those handlers.
350		584
351	use POSIX qw(tzset);	585	use POSIX qw(tzset);
352		586
353	async {	587	async {
…		…
370	};	604	};
371		605
372	This can be used to localise about any resource (locale, uid, current	606	This can be used to localise about any resource (locale, uid, current
373	working directory etc.) to a block, despite the existance of other	607	working directory etc.) to a block, despite the existance of other
374	coros.	608	coros.
		609
		610	Another interesting example implements time-sliced multitasking using
		611	interval timers (this could obviously be optimised, but does the job):
		612
		613	# "timeslice" the given block
		614	sub timeslice(&) {
		615	use Time::HiRes ();
		616
		617	Coro::on_enter {
		618	# on entering the thread, we set an VTALRM handler to cede
		619	$SIG{VTALRM} = sub { cede };
		620	# and then start the interval timer
		621	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
		622	};
		623	Coro::on_leave {
		624	# on leaving the thread, we stop the interval timer again
		625	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
		626	};
		627
		628	&{+shift};
		629	}
		630
		631	# use like this:
		632	timeslice {
		633	# The following is an endless loop that would normally
		634	# monopolise the process. Since it runs in a timesliced
		635	# environment, it will regularly cede to other threads.
		636	while () { }
		637	};
		638
375		639
376	=item killall	640	=item killall
377		641
378	Kills/terminates/cancels all coros except the currently running one.	642	Kills/terminates/cancels all coros except the currently running one.
379		643
…		…
424		688
425	This ensures that the scheduler will resume this coro automatically	689	This ensures that the scheduler will resume this coro automatically
426	once all the coro of higher priority and all coro of the same	690	once all the coro of higher priority and all coro of the same
427	priority that were put into the ready queue earlier have been resumed.	691	priority that were put into the ready queue earlier have been resumed.
428		692
		693	=item $coro->suspend
		694
		695	Suspends the specified coro. A suspended coro works just like any other
		696	coro, except that the scheduler will not select a suspended coro for
		697	execution.
		698
		699	Suspending a coro can be useful when you want to keep the coro from
		700	running, but you don't want to destroy it, or when you want to temporarily
		701	freeze a coro (e.g. for debugging) to resume it later.
		702
		703	A scenario for the former would be to suspend all (other) coros after a
		704	fork and keep them alive, so their destructors aren't called, but new
		705	coros can be created.
		706
		707	=item $coro->resume
		708
		709	If the specified coro was suspended, it will be resumed. Note that when
		710	the coro was in the ready queue when it was suspended, it might have been
		711	unreadied by the scheduler, so an activation might have been lost.
		712
		713	To avoid this, it is best to put a suspended coro into the ready queue
		714	unconditionally, as every synchronisation mechanism must protect itself
		715	against spurious wakeups, and the one in the Coro family certainly do
		716	that.
		717
429	=item $is_ready = $coro->is_ready	718	=item $is_ready = $coro->is_ready
430		719
431	Returns true iff the Coro object is in the ready queue. Unless the Coro	720	Returns true iff the Coro object is in the ready queue. Unless the Coro
432	object gets destroyed, it will eventually be scheduled by the scheduler.	721	object gets destroyed, it will eventually be scheduled by the scheduler.
433		722
…		…
442	Returns true iff this Coro object has been suspended. Suspended Coros will	731	Returns true iff this Coro object has been suspended. Suspended Coros will
443	not ever be scheduled.	732	not ever be scheduled.
444		733
445	=item $coro->cancel (arg...)	734	=item $coro->cancel (arg...)
446		735
447	Terminates the given Coro and makes it return the given arguments as	736	Terminates the given Coro thread and makes it return the given arguments as
448	status (default: the empty list). Never returns if the Coro is the	737	status (default: an empty list). Never returns if the Coro is the
449	current Coro.	738	current Coro.
450		739
451	=cut	740	This is a rather brutal way to free a coro, with some limitations - if
		741	the thread is inside a C callback that doesn't expect to be canceled,
		742	bad things can happen, or if the cancelled thread insists on running
		743	complicated cleanup handlers that rely on it'S thread context, things will
		744	not work.
452		745
453	sub cancel {	746	Any cleanup code being run (e.g. from C<guard> blocks) will be run without
454	my $self = shift;	747	a thread context, and is not allowed to switch to other threads. On the
		748	plus side, C<< ->cancel >> will always clean up the thread, no matter
		749	what. If your cleanup code is complex or you want to avoid cancelling a
		750	C-thread that doesn't know how to clean up itself, it can be better to C<<
		751	->throw >> an exception, or use C<< ->safe_cancel >>.
455		752
456	if ($current == $self) {	753	The arguments to C<< ->cancel >> are not copied, but instead will
457	terminate @_;	754	be referenced directly (e.g. if you pass C<$var> and after the call
458	} else {	755	change that variable, then you might change the return values passed to
459	$self->{_status} = [@_];	756	e.g. C<join>, so don't do that).
460	Coro::State::cancel $self;	757
		758	The resources of the Coro are usually freed (or destructed) before this
		759	call returns, but this can be delayed for an indefinite amount of time, as
		760	in some cases the manager thread has to run first to actually destruct the
		761	Coro object.
		762
		763	=item $coro->safe_cancel ($arg...)
		764
		765	Works mostly like C<< ->cancel >>, but is inherently "safer", and
		766	consequently, can fail with an exception in cases the thread is not in a
		767	cancellable state.
		768
		769	This method works a bit like throwing an exception that cannot be caught
		770	- specifically, it will clean up the thread from within itself, so
		771	all cleanup handlers (e.g. C<guard> blocks) are run with full thread
		772	context and can block if they wish. The downside is that there is no
		773	guarantee that the thread can be cancelled when you call this method, and
		774	therefore, it might fail. It is also considerably slower than C<cancel> or
		775	C<terminate>.
		776
		777	A thread is in a safe-cancellable state if it either hasn't been run yet,
		778	or it has no C context attached and is inside an SLF function.
		779
		780	The latter two basically mean that the thread isn't currently inside a
		781	perl callback called from some C function (usually via some XS modules)
		782	and isn't currently executing inside some C function itself (via Coro's XS
		783	API).
		784
		785	This call returns true when it could cancel the thread, or croaks with an
		786	error otherwise (i.e. it either returns true or doesn't return at all).
		787
		788	Why the weird interface? Well, there are two common models on how and
		789	when to cancel things. In the first, you have the expectation that your
		790	coro thread can be cancelled when you want to cancel it - if the thread
		791	isn't cancellable, this would be a bug somewhere, so C<< ->safe_cancel >>
		792	croaks to notify of the bug.
		793
		794	In the second model you sometimes want to ask nicely to cancel a thread,
		795	but if it's not a good time, well, then don't cancel. This can be done
		796	relatively easy like this:
		797
		798	if (! eval { $coro->safe_cancel }) {
		799	warn "unable to cancel thread: $@";
461	}	800	}
462	}	801
		802	However, what you never should do is first try to cancel "safely" and
		803	if that fails, cancel the "hard" way with C<< ->cancel >>. That makes
		804	no sense: either you rely on being able to execute cleanup code in your
		805	thread context, or you don't. If you do, then C<< ->safe_cancel >> is the
		806	only way, and if you don't, then C<< ->cancel >> is always faster and more
		807	direct.
463		808
464	=item $coro->schedule_to	809	=item $coro->schedule_to
465		810
466	Puts the current coro to sleep (like C<Coro::schedule>), but instead	811	Puts the current coro to sleep (like C<Coro::schedule>), but instead
467	of continuing with the next coro from the ready queue, always switch to	812	of continuing with the next coro from the ready queue, always switch to
…		…
486	inside the coro at the next convenient point in time. Otherwise	831	inside the coro at the next convenient point in time. Otherwise
487	clears the exception object.	832	clears the exception object.
488		833
489	Coro will check for the exception each time a schedule-like-function	834	Coro will check for the exception each time a schedule-like-function
490	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down	835	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
491	>>, C<< Coro::Handle->readable >> and so on. Most of these functions	836	>>, C<< Coro::Handle->readable >> and so on. Most of those functions (all
492	detect this case and return early in case an exception is pending.	837	that are part of Coro itself) detect this case and return early in case an
		838	exception is pending.
493		839
494	The exception object will be thrown "as is" with the specified scalar in	840	The exception object will be thrown "as is" with the specified scalar in
495	C<$@>, i.e. if it is a string, no line number or newline will be appended	841	C<$@>, i.e. if it is a string, no line number or newline will be appended
496	(unlike with C<die>).	842	(unlike with C<die>).
497		843
498	This can be used as a softer means than C<cancel> to ask a coro to	844	This can be used as a softer means than either C<cancel> or C<safe_cancel
499	end itself, although there is no guarantee that the exception will lead to	845	>to ask a coro to end itself, although there is no guarantee that the
500	termination, and if the exception isn't caught it might well end the whole	846	exception will lead to termination, and if the exception isn't caught it
501	program.	847	might well end the whole program.
502		848
503	You might also think of C<throw> as being the moral equivalent of	849	You might also think of C<throw> as being the moral equivalent of
504	C<kill>ing a coro with a signal (in this case, a scalar).	850	C<kill>ing a coro with a signal (in this case, a scalar).
505		851
506	=item $coro->join	852	=item $coro->join
507		853
508	Wait until the coro terminates and return any values given to the	854	Wait until the coro terminates and return any values given to the
509	C<terminate> or C<cancel> functions. C<join> can be called concurrently	855	C<terminate> or C<cancel> functions. C<join> can be called concurrently
510	from multiple coro, and all will be resumed and given the status	856	from multiple threads, and all will be resumed and given the status
511	return once the C<$coro> terminates.	857	return once the C<$coro> terminates.
512		858
513	=cut	859	=cut
514		860
515	sub join {	861	sub join {
…		…
524	};	870	};
525		871
526	&schedule while $current;	872	&schedule while $current;
527	}	873	}
528		874
529	wantarray ? @{$self->{_status}} : $self->{_status}[0];	875	wantarray ? @{$self->{_status}} : $self->{_status}[0]
530	}	876	}
531		877
532	=item $coro->on_destroy (\&cb)	878	=item $coro->on_destroy (\&cb)
533		879
534	Registers a callback that is called when this coro gets destroyed,	880	Registers a callback that is called when this coro thread gets destroyed,
535	but before it is joined. The callback gets passed the terminate arguments,	881	that is, after it's resources have been freed but before it is joined. The
		882	callback gets passed the terminate/cancel arguments, if any, and I<must
536	if any, and I<must not> die, under any circumstances.	883	not> die, under any circumstances.
		884
		885	There can be any number of C<on_destroy> callbacks per coro, and there is
		886	no way currently to remove a callback once added.
537		887
538	=cut	888	=cut
539		889
540	sub on_destroy {	890	sub on_destroy {
541	my ($self, $cb) = @_;	891	my ($self, $cb) = @_;
…		…
544	}	894	}
545		895
546	=item $oldprio = $coro->prio ($newprio)	896	=item $oldprio = $coro->prio ($newprio)
547		897
548	Sets (or gets, if the argument is missing) the priority of the	898	Sets (or gets, if the argument is missing) the priority of the
549	coro. Higher priority coro get run before lower priority	899	coro thread. Higher priority coro get run before lower priority
550	coro. Priorities are small signed integers (currently -4 .. +3),	900	coros. Priorities are small signed integers (currently -4 .. +3),
551	that you can refer to using PRIO_xxx constants (use the import tag :prio	901	that you can refer to using PRIO_xxx constants (use the import tag :prio
552	to get then):	902	to get then):
553		903
554	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	904	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
555	3 > 1 > 0 > -1 > -3 > -4	905	3 > 1 > 0 > -1 > -3 > -4
556		906
557	# set priority to HIGH	907	# set priority to HIGH
558	current->prio (PRIO_HIGH);	908	current->prio (PRIO_HIGH);
559		909
560	The idle coro ($Coro::idle) always has a lower priority than any	910	The idle coro thread ($Coro::idle) always has a lower priority than any
561	existing coro.	911	existing coro.
562		912
563	Changing the priority of the current coro will take effect immediately,	913	Changing the priority of the current coro will take effect immediately,
564	but changing the priority of coro in the ready queue (but not	914	but changing the priority of a coro in the ready queue (but not running)
565	running) will only take effect after the next schedule (of that	915	will only take effect after the next schedule (of that coro). This is a
566	coro). This is a bug that will be fixed in some future version.	916	bug that will be fixed in some future version.
567		917
568	=item $newprio = $coro->nice ($change)	918	=item $newprio = $coro->nice ($change)
569		919
570	Similar to C<prio>, but subtract the given value from the priority (i.e.	920	Similar to C<prio>, but subtract the given value from the priority (i.e.
571	higher values mean lower priority, just as in unix).	921	higher values mean lower priority, just as in UNIX's nice command).
572		922
573	=item $olddesc = $coro->desc ($newdesc)	923	=item $olddesc = $coro->desc ($newdesc)
574		924
575	Sets (or gets in case the argument is missing) the description for this	925	Sets (or gets in case the argument is missing) the description for this
576	coro. This is just a free-form string you can associate with a	926	coro thread. This is just a free-form string you can associate with a
577	coro.	927	coro.
578		928
579	This method simply sets the C<< $coro->{desc} >> member to the given	929	This method simply sets the C<< $coro->{desc} >> member to the given
580	string. You can modify this member directly if you wish.	930	string. You can modify this member directly if you wish, and in fact, this
		931	is often preferred to indicate major processing states that cna then be
		932	seen for example in a L<Coro::Debug> session:
		933
		934	sub my_long_function {
		935	local $Coro::current->{desc} = "now in my_long_function";
		936	...
		937	$Coro::current->{desc} = "my_long_function: phase 1";
		938	...
		939	$Coro::current->{desc} = "my_long_function: phase 2";
		940	...
		941	}
581		942
582	=cut	943	=cut
583		944
584	sub desc {	945	sub desc {
585	my $old = $_[0]{desc};	946	my $old = $_[0]{desc};
…		…
622	returning a new coderef. Unblocking means that calling the new coderef	983	returning a new coderef. Unblocking means that calling the new coderef
623	will return immediately without blocking, returning nothing, while the	984	will return immediately without blocking, returning nothing, while the
624	original code ref will be called (with parameters) from within another	985	original code ref will be called (with parameters) from within another
625	coro.	986	coro.
626		987
627	The reason this function exists is that many event libraries (such as the	988	The reason this function exists is that many event libraries (such as
628	venerable L<Event\|Event> module) are not thread-safe (a weaker form	989	the venerable L<Event\|Event> module) are not thread-safe (a weaker form
629	of reentrancy). This means you must not block within event callbacks,	990	of reentrancy). This means you must not block within event callbacks,
630	otherwise you might suffer from crashes or worse. The only event library	991	otherwise you might suffer from crashes or worse. The only event library
631	currently known that is safe to use without C<unblock_sub> is L<EV>.	992	currently known that is safe to use without C<unblock_sub> is L<EV> (but
		993	you might still run into deadlocks if all event loops are blocked).
		994
		995	Coro will try to catch you when you block in the event loop
		996	("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and
		997	only works when you do not run your own event loop.
632		998
633	This function allows your callbacks to block by executing them in another	999	This function allows your callbacks to block by executing them in another
634	coro where it is safe to block. One example where blocking is handy	1000	coro where it is safe to block. One example where blocking is handy
635	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	1001	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
636	disk, for example.	1002	disk, for example.
…		…
678	unshift @unblock_queue, [$cb, @_];	1044	unshift @unblock_queue, [$cb, @_];
679	$unblock_scheduler->ready;	1045	$unblock_scheduler->ready;
680	}	1046	}
681	}	1047	}
682		1048
683	=item $cb = Coro::rouse_cb	1049	=item $cb = rouse_cb
684		1050
685	Create and return a "rouse callback". That's a code reference that,	1051	Create and return a "rouse callback". That's a code reference that,
686	when called, will remember a copy of its arguments and notify the owner	1052	when called, will remember a copy of its arguments and notify the owner
687	coro of the callback.	1053	coro of the callback.
688		1054
689	See the next function.	1055	See the next function.
690		1056
691	=item @args = Coro::rouse_wait [$cb]	1057	=item @args = rouse_wait [$cb]
692		1058
693	Wait for the specified rouse callback (or the last one that was created in	1059	Wait for the specified rouse callback (or the last one that was created in
694	this coro).	1060	this coro).
695		1061
696	As soon as the callback is invoked (or when the callback was invoked	1062	As soon as the callback is invoked (or when the callback was invoked
697	before C<rouse_wait>), it will return the arguments originally passed to	1063	before C<rouse_wait>), it will return the arguments originally passed to
698	the rouse callback.	1064	the rouse callback. In scalar context, that means you get the I<last>
		1065	argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
		1066	statement at the end.
699		1067
700	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.	1068	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
701		1069
702	=back	1070	=back
703		1071
704	=cut	1072	=cut
		1073
		1074	for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) {
		1075	my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"};
		1076
		1077	*{"Coro::$module\::new"} = sub {
		1078	require "Coro/$module.pm";
		1079
		1080	# some modules have their new predefined in State.xs, some don't
		1081	*{"Coro::$module\::new"} = $old
		1082	if $old;
		1083
		1084	goto &{"Coro::$module\::new"};
		1085	};
		1086	}
705		1087
706	1;	1088	1;
707		1089
708	=head1 HOW TO WAIT FOR A CALLBACK	1090	=head1 HOW TO WAIT FOR A CALLBACK
709		1091
…		…
791	the windows process emulation enabled under unix roughly halves perl	1173	the windows process emulation enabled under unix roughly halves perl
792	performance, even when not used.	1174	performance, even when not used.
793		1175
794	=item coro switching is not signal safe	1176	=item coro switching is not signal safe
795		1177
796	You must not switch to another coro from within a signal handler	1178	You must not switch to another coro from within a signal handler (only
797	(only relevant with %SIG - most event libraries provide safe signals).	1179	relevant with %SIG - most event libraries provide safe signals), I<unless>
		1180	you are sure you are not interrupting a Coro function.
798		1181
799	That means you I<MUST NOT> call any function that might "block" the	1182	That means you I<MUST NOT> call any function that might "block" the
800	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or	1183	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
801	anything that calls those. Everything else, including calling C<ready>,	1184	anything that calls those. Everything else, including calling C<ready>,
802	works.	1185	works.
803		1186
804	=back	1187	=back
805		1188
806		1189
		1190	=head1 WINDOWS PROCESS EMULATION
		1191
		1192	A great many people seem to be confused about ithreads (for example, Chip
		1193	Salzenberg called me unintelligent, incapable, stupid and gullible,
		1194	while in the same mail making rather confused statements about perl
		1195	ithreads (for example, that memory or files would be shared), showing his
		1196	lack of understanding of this area - if it is hard to understand for Chip,
		1197	it is probably not obvious to everybody).
		1198
		1199	What follows is an ultra-condensed version of my talk about threads in
		1200	scripting languages given on the perl workshop 2009:
		1201
		1202	The so-called "ithreads" were originally implemented for two reasons:
		1203	first, to (badly) emulate unix processes on native win32 perls, and
		1204	secondly, to replace the older, real thread model ("5.005-threads").
		1205
		1206	It does that by using threads instead of OS processes. The difference
		1207	between processes and threads is that threads share memory (and other
		1208	state, such as files) between threads within a single process, while
		1209	processes do not share anything (at least not semantically). That
		1210	means that modifications done by one thread are seen by others, while
		1211	modifications by one process are not seen by other processes.
		1212
		1213	The "ithreads" work exactly like that: when creating a new ithreads
		1214	process, all state is copied (memory is copied physically, files and code
		1215	is copied logically). Afterwards, it isolates all modifications. On UNIX,
		1216	the same behaviour can be achieved by using operating system processes,
		1217	except that UNIX typically uses hardware built into the system to do this
		1218	efficiently, while the windows process emulation emulates this hardware in
		1219	software (rather efficiently, but of course it is still much slower than
		1220	dedicated hardware).
		1221
		1222	As mentioned before, loading code, modifying code, modifying data
		1223	structures and so on is only visible in the ithreads process doing the
		1224	modification, not in other ithread processes within the same OS process.
		1225
		1226	This is why "ithreads" do not implement threads for perl at all, only
		1227	processes. What makes it so bad is that on non-windows platforms, you can
		1228	actually take advantage of custom hardware for this purpose (as evidenced
		1229	by the forks module, which gives you the (i-) threads API, just much
		1230	faster).
		1231
		1232	Sharing data is in the i-threads model is done by transfering data
		1233	structures between threads using copying semantics, which is very slow -
		1234	shared data simply does not exist. Benchmarks using i-threads which are
		1235	communication-intensive show extremely bad behaviour with i-threads (in
		1236	fact, so bad that Coro, which cannot take direct advantage of multiple
		1237	CPUs, is often orders of magnitude faster because it shares data using
		1238	real threads, refer to my talk for details).
		1239
		1240	As summary, i-threads use threads to implement processes, while
		1241	the compatible forks module uses processes to emulate, uhm,
		1242	processes. I-threads slow down every perl program when enabled, and
		1243	outside of windows, serve no (or little) practical purpose, but
		1244	disadvantages every single-threaded Perl program.
		1245
		1246	This is the reason that I try to avoid the name "ithreads", as it is
		1247	misleading as it implies that it implements some kind of thread model for
		1248	perl, and prefer the name "windows process emulation", which describes the
		1249	actual use and behaviour of it much better.
		1250
807	=head1 SEE ALSO	1251	=head1 SEE ALSO
808		1252
809	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.	1253	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
810		1254
811	Debugging: L<Coro::Debug>.	1255	Debugging: L<Coro::Debug>.

Diff Legend

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

Comparing cvsroot/Coro/Coro.pm (file contents): Revision 1.248 by root, Mon Dec 15 15:03:31 2008 UTC vs. Revision 1.295 by root, Tue May 10 19:55:48 2011 UTC

Diff Legend

Comparing cvsroot/Coro/Coro.pm (file contents):
Revision 1.248 by root, Mon Dec 15 15:03:31 2008 UTC vs.
Revision 1.295 by root, Tue May 10 19:55:48 2011 UTC