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1	NAME	1	NAME
2	Coro - coroutine process abstraction	2	Coro - the only real threads in perl
3		3
4	SYNOPSIS	4	SYNOPSIS
5	use Coro;	5	use Coro;
6		6
7	async {	7	async {
8	# some asynchronous thread of execution	8	# some asynchronous thread of execution
9	print "2\n";	9	print "2\n";
10	cede; # yield back to main	10	cede; # yield back to main
11	print "4\n";	11	print "4\n";
12	};	12	};
13	print "1\n";	13	print "1\n";
14	cede; # yield to coroutine	14	cede; # yield to coro
15	print "3\n";	15	print "3\n";
16	cede; # and again	16	cede; # and again
17		17
18	# use locking	18	# use locking
		19	use Coro::Semaphore;
19	my $lock = new Coro::Semaphore;	20	my $lock = new Coro::Semaphore;
20	my $locked;	21	my $locked;
21		22
22	$lock->down;	23	$lock->down;
23	$locked = 1;	24	$locked = 1;
24	$lock->up;	25	$lock->up;
25		26
26	DESCRIPTION	27	DESCRIPTION
27	This module collection manages coroutines. Coroutines are similar to	28	For a tutorial-style introduction, please read the Coro::Intro manpage.
		29	This manpage mainly contains reference information.
		30
		31	This module collection manages continuations in general, most often in
		32	the form of cooperative threads (also called coros, or simply "coro" in
		33	the documentation). They are similar to kernel threads but don't (in
28	threads but don't run in parallel at the same time even on SMP machines.	34	general) run in parallel at the same time even on SMP machines. The
29	The specific flavor of coroutine used in this module also guarantees you	35	specific flavor of thread offered by this module also guarantees you
30	that it will not switch between coroutines unless necessary, at	36	that it will not switch between threads unless necessary, at
31	easily-identified points in your program, so locking and parallel access	37	easily-identified points in your program, so locking and parallel access
32	are rarely an issue, making coroutine programming much safer than	38	are rarely an issue, making thread programming much safer and easier
33	threads programming.	39	than using other thread models.
34		40
35	(Perl, however, does not natively support real threads but instead does	41	Unlike the so-called "Perl threads" (which are not actually real threads
36	a very slow and memory-intensive emulation of processes using threads.	42	but only the windows process emulation ported to unix, and as such act
37	This is a performance win on Windows machines, and a loss everywhere	43	as processes), Coro provides a full shared address space, which makes
38	else).	44	communication between threads very easy. And Coro's threads are fast,
		45	too: disabling the Windows process emulation code in your perl and using
		46	Coro can easily result in a two to four times speed increase for your
		47	programs. A parallel matrix multiplication benchmark runs over 300 times
		48	faster on a single core than perl's pseudo-threads on a quad core using
		49	all four cores.
39		50
		51	Coro achieves that by supporting multiple running interpreters that
		52	share data, which is especially useful to code pseudo-parallel processes
		53	and for event-based programming, such as multiple HTTP-GET requests
		54	running concurrently. See Coro::AnyEvent to learn more on how to
		55	integrate Coro into an event-based environment.
		56
40	In this module, coroutines are defined as "callchain + lexical variables	57	In this module, a thread is defined as "callchain + lexical variables +
41	+ @_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own	58	some package variables + C stack), that is, a thread has its own
42	callchain, its own set of lexicals and its own set of perls most	59	callchain, its own set of lexicals and its own set of perls most
43	important global variables (see Coro::State for more configuration).	60	important global variables (see Coro::State for more configuration and
		61	background info).
44		62
		63	See also the "SEE ALSO" section at the end of this document - the Coro
		64	module family is quite large.
		65
		66	GLOBAL VARIABLES
45	$main	67	$Coro::main
46	This coroutine represents the main program.	68	This variable stores the Coro object that represents the main
		69	program. While you cna "ready" it and do most other things you can
		70	do to coro, it is mainly useful to compare again $Coro::current, to
		71	see whether you are running in the main program or not.
47		72
48	$current (or as function: current)	73	$Coro::current
49	The current coroutine (the last coroutine switched to). The initial	74	The Coro object representing the current coro (the last coro that
50	value is $main (of course).	75	the Coro scheduler switched to). The initial value is $Coro::main
		76	(of course).
51		77
52	This variable is strictly read-only. It is provided for	78	This variable is strictly read-only. You can take copies of the
53	performance reasons. If performance is not essential you are	79	value stored in it and use it as any other Coro object, but you must
54	encouraged to use the "Coro::current" function instead.	80	not otherwise modify the variable itself.
55		81
56	$idle	82	$Coro::idle
		83	This variable is mainly useful to integrate Coro into event loops.
		84	It is usually better to rely on Coro::AnyEvent or Coro::EV, as this
		85	is pretty low-level functionality.
		86
		87	This variable stores either a Coro object or a callback.
		88
57	A callback that is called whenever the scheduler finds no ready	89	If it is a callback, the it is called whenever the scheduler finds
58	coroutines to run. The default implementation prints "FATAL:	90	no ready coros to run. The default implementation prints "FATAL:
59	deadlock detected" and exits, because the program has no other way	91	deadlock detected" and exits, because the program has no other way
60	to continue.	92	to continue.
61		93
		94	If it is a coro object, then this object will be readied (without
		95	invoking any ready hooks, however) when the scheduler finds no other
		96	ready coros to run.
		97
62	This hook is overwritten by modules such as "Coro::Timer" and	98	This hook is overwritten by modules such as "Coro::EV" and
63	"Coro::Event" to wait on an external event that hopefully wake up a	99	"Coro::AnyEvent" to wait on an external event that hopefully wake up
64	coroutine so the scheduler can run it.	100	a coro so the scheduler can run it.
		101
		102	Note that the callback must not, under any circumstances, block
		103	the current coro. Normally, this is achieved by having an "idle
		104	coro" that calls the event loop and then blocks again, and then
		105	readying that coro in the idle handler, or by simply placing the
		106	idle coro in this variable.
		107
		108	See Coro::Event or Coro::AnyEvent for examples of using this
		109	technique.
65		110
66	Please note that if your callback recursively invokes perl (e.g. for	111	Please note that if your callback recursively invokes perl (e.g. for
67	event handlers), then it must be prepared to be called recursively	112	event handlers), then it must be prepared to be called recursively
68	itself.	113	itself.
69		114
70	STATIC METHODS	115	SIMPLE CORO CREATION
71	Static methods are actually functions that operate on the current
72	coroutine only.
73
74	async { ... } [@args...]	116	async { ... } [@args...]
75	Create a new asynchronous coroutine and return it's coroutine object	117	Create a new coro and return its Coro object (usually unused). The
76	(usually unused). When the sub returns the new coroutine is	118	coro will be put into the ready queue, so it will start running
77	automatically terminated.	119	automatically on the next scheduler run.
78		120
		121	The first argument is a codeblock/closure that should be executed in
		122	the coro. When it returns argument returns the coro is automatically
		123	terminated.
		124
		125	The remaining arguments are passed as arguments to the closure.
		126
79	See the "Coro::State::new" constructor for info about the coroutine	127	See the "Coro::State::new" constructor for info about the coro
80	environment in which coroutines run.	128	environment in which coro are executed.
81		129
82	Calling "exit" in a coroutine will do the same as calling exit	130	Calling "exit" in a coro will do the same as calling exit outside
83	outside the coroutine. Likewise, when the coroutine dies, the	131	the coro. Likewise, when the coro dies, the program will exit, just
84	program will exit, just as it would in the main program.	132	as it would in the main program.
85		133
		134	If you do not want that, you can provide a default "die" handler, or
		135	simply avoid dieing (by use of "eval").
		136
86	# create a new coroutine that just prints its arguments	137	Example: Create a new coro that just prints its arguments.
		138
87	async {	139	async {
88	print "@_\n";	140	print "@_\n";
89	} 1,2,3,4;	141	} 1,2,3,4;
90		142
91	async_pool { ... } [@args...]	143	async_pool { ... } [@args...]
92	Similar to "async", but uses a coroutine pool, so you should not	144	Similar to "async", but uses a coro pool, so you should not call
93	call terminate or join (although you are allowed to), and you get a	145	terminate or join on it (although you are allowed to), and you get a
94	coroutine that might have executed other code already (which can be	146	coro that might have executed other code already (which can be good
95	good or bad :).	147	or bad :).
96		148
		149	On the plus side, this function is about twice as fast as creating
		150	(and destroying) a completely new coro, so if you need a lot of
		151	generic coros in quick successsion, use "async_pool", not "async".
		152
97	Also, the block is executed in an "eval" context and a warning will	153	The code block is executed in an "eval" context and a warning will
98	be issued in case of an exception instead of terminating the	154	be issued in case of an exception instead of terminating the
99	program, as "async" does. As the coroutine is being reused, stuff	155	program, as "async" does. As the coro is being reused, stuff like
100	like "on_destroy" will not work in the expected way, unless you call	156	"on_destroy" will not work in the expected way, unless you call
101	terminate or cancel, which somehow defeats the purpose of pooling.	157	terminate or cancel, which somehow defeats the purpose of pooling
		158	(but is fine in the exceptional case).
102		159
103	The priority will be reset to 0 after each job, tracing will be	160	The priority will be reset to 0 after each run, tracing will be
104	disabled, the description will be reset and the default output	161	disabled, the description will be reset and the default output
105	filehandle gets restored, so you can change alkl these. Otherwise	162	filehandle gets restored, so you can change all these. Otherwise the
106	the coroutine will be re-used "as-is": most notably if you change	163	coro will be re-used "as-is": most notably if you change other
107	other per-coroutine global stuff such as $/ you need to revert that	164	per-coro global stuff such as $/ you must needs revert that
108	change, which is most simply done by using local as in " local $/ ".	165	change, which is most simply done by using local as in: "local $/".
109		166
110	The pool size is limited to 8 idle coroutines (this can be adjusted	167	The idle pool size is limited to 8 idle coros (this can be adjusted
111	by changing $Coro::POOL_SIZE), and there can be as many non-idle	168	by changing $Coro::POOL_SIZE), but there can be as many non-idle
112	coros as required.	169	coros as required.
113		170
114	If you are concerned about pooled coroutines growing a lot because a	171	If you are concerned about pooled coros growing a lot because a
115	single "async_pool" used a lot of stackspace you can e.g.	172	single "async_pool" used a lot of stackspace you can e.g.
116	"async_pool { terminate }" once per second or so to slowly replenish	173	"async_pool { terminate }" once per second or so to slowly replenish
117	the pool. In addition to that, when the stacks used by a handler	174	the pool. In addition to that, when the stacks used by a handler
118	grows larger than 16kb (adjustable with $Coro::POOL_RSS) it will	175	grows larger than 32kb (adjustable via $Coro::POOL_RSS) it will also
119	also exit.	176	be destroyed.
		177
		178	STATIC METHODS
		179	Static methods are actually functions that implicitly operate on the
		180	current coro.
120		181
121	schedule	182	schedule
122	Calls the scheduler. Please note that the current coroutine will not	183	Calls the scheduler. The scheduler will find the next coro that is
123	be put into the ready queue, so calling this function usually means	184	to be run from the ready queue and switches to it. The next coro to
		185	be run is simply the one with the highest priority that is longest
		186	in its ready queue. If there is no coro ready, it will clal the
		187	$Coro::idle hook.
		188
		189	Please note that the current coro will not be put into the ready
		190	queue, so calling this function usually means you will never be
124	you will never be called again unless something else (e.g. an event	191	called again unless something else (e.g. an event handler) calls
125	handler) calls ready.	192	"->ready", thus waking you up.
126		193
127	The canonical way to wait on external events is this:	194	This makes "schedule" the generic method to use to block the
		195	current coro and wait for events: first you remember the current
		196	coro in a variable, then arrange for some callback of yours to call
		197	"->ready" on that once some event happens, and last you call
		198	"schedule" to put yourself to sleep. Note that a lot of things can
		199	wake your coro up, so you need to check whether the event indeed
		200	happened, e.g. by storing the status in a variable.
128		201
		202	See HOW TO WAIT FOR A CALLBACK, below, for some ways to wait for
		203	callbacks.
		204
		205	cede
		206	"Cede" to other coros. This function puts the current coro into the
		207	ready queue and calls "schedule", which has the effect of giving up
		208	the current "timeslice" to other coros of the same or higher
		209	priority. Once your coro gets its turn again it will automatically
		210	be resumed.
		211
		212	This function is often called "yield" in other languages.
		213
		214	Coro::cede_notself
		215	Works like cede, but is not exported by default and will cede to
		216	any coro, regardless of priority. This is useful sometimes to
		217	ensure progress is made.
		218
		219	terminate [arg...]
		220	Terminates the current coro with the given status values (see
		221	cancel).
		222
		223	Coro::on_enter BLOCK, Coro::on_leave BLOCK
		224	These function install enter and leave winders in the current scope.
		225	The enter block will be executed when on_enter is called and
		226	whenever the current coro is re-entered by the scheduler, while the
		227	leave block is executed whenever the current coro is blocked by the
		228	scheduler, and also when the containing scope is exited (by whatever
		229	means, be it exit, die, last etc.).
		230
		231	*Neither invoking the scheduler, nor exceptions, are allowed within
		232	those BLOCKs*. That means: do not even think about calling "die"
		233	without an eval, and do not even think of entering the scheduler in
		234	any way.
		235
		236	Since both BLOCKs are tied to the current scope, they will
		237	automatically be removed when the current scope exits.
		238
		239	These functions implement the same concept as "dynamic-wind" in
		240	scheme does, and are useful when you want to localise some resource
		241	to a specific coro.
		242
		243	They slow down thread switching considerably for coros that use them
		244	(about 40% for a BLOCK with a single assignment, so thread switching
		245	is still reasonably fast if the handlers are fast).
		246
		247	These functions are best understood by an example: The following
		248	function will change the current timezone to
		249	"Antarctica/South_Pole", which requires a call to "tzset", but by
		250	using "on_enter" and "on_leave", which remember/change the current
		251	timezone and restore the previous value, respectively, the timezone
		252	is only changed for the coro that installed those handlers.
		253
		254	use POSIX qw(tzset);
		255
129	{	256	async {
130	# remember current coroutine	257	my $old_tz; # store outside TZ value here
131	my $current = $Coro::current;
132		258
133	# register a hypothetical event handler	259	Coro::on_enter {
134	on_event_invoke sub {	260	$old_tz = $ENV{TZ}; # remember the old value
135	# wake up sleeping coroutine	261
136	$current->ready;	262	$ENV{TZ} = "Antarctica/South_Pole";
137	undef $current;	263	tzset; # enable new value
138	};	264	};
139		265
140	# call schedule until event occurred.	266	Coro::on_leave {
141	# in case we are woken up for other reasons	267	$ENV{TZ} = $old_tz;
142	# (current still defined), loop.	268	tzset; # restore old value
143	Coro::schedule while $current;	269	};
		270
		271	# at this place, the timezone is Antarctica/South_Pole,
		272	# without disturbing the TZ of any other coro.
144	}	273	};
145		274
146	cede	275	This can be used to localise about any resource (locale, uid,
147	"Cede" to other coroutines. This function puts the current coroutine	276	current working directory etc.) to a block, despite the existance of
148	into the ready queue and calls "schedule", which has the effect of	277	other coros.
149	giving up the current "timeslice" to other coroutines of the same or
150	higher priority.
151		278
152	Coro::cede_notself	279	Another interesting example implements time-sliced multitasking
153	Works like cede, but is not exported by default and will cede to any	280	using interval timers (this could obviously be optimised, but does
154	coroutine, regardless of priority, once.	281	the job):
155		282
156	terminate [arg...]	283	# "timeslice" the given block
157	Terminates the current coroutine with the given status values (see	284	sub timeslice(&) {
158	cancel).	285	use Time::HiRes ();
		286
		287	Coro::on_enter {
		288	# on entering the thread, we set an VTALRM handler to cede
		289	$SIG{VTALRM} = sub { cede };
		290	# and then start the interval timer
		291	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
		292	};
		293	Coro::on_leave {
		294	# on leaving the thread, we stop the interval timer again
		295	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
		296	};
		297
		298	&{+shift};
		299	}
		300
		301	# use like this:
		302	timeslice {
		303	# The following is an endless loop that would normally
		304	# monopolise the process. Since it runs in a timesliced
		305	# environment, it will regularly cede to other threads.
		306	while () { }
		307	};
159		308
160	killall	309	killall
161	Kills/terminates/cancels all coroutines except the currently running	310	Kills/terminates/cancels all coros except the currently running one.
162	one. This is useful after a fork, either in the child or the parent,
163	as usually only one of them should inherit the running coroutines.
164		311
165	# dynamic methods	312	Note that while this will try to free some of the main interpreter
		313	resources if the calling coro isn't the main coro, but one cannot
		314	free all of them, so if a coro that is not the main coro calls this
		315	function, there will be some one-time resource leak.
166		316
167	COROUTINE METHODS	317	CORO OBJECT METHODS
168	These are the methods you can call on coroutine objects.	318	These are the methods you can call on coro objects (or to create them).
169		319
170	new Coro \&sub [, @args...]	320	new Coro \&sub [, @args...]
171	Create a new coroutine and return it. When the sub returns the	321	Create a new coro and return it. When the sub returns, the coro
172	coroutine automatically terminates as if "terminate" with the	322	automatically terminates as if "terminate" with the returned values
173	returned values were called. To make the coroutine run you must	323	were called. To make the coro run you must first put it into the
174	first put it into the ready queue by calling the ready method.	324	ready queue by calling the ready method.
175		325
176	See "async" and "Coro::State::new" for additional info about the	326	See "async" and "Coro::State::new" for additional info about the
177	coroutine environment.	327	coro environment.
178		328
179	$success = $coroutine->ready	329	$success = $coro->ready
180	Put the given coroutine into the ready queue (according to it's	330	Put the given coro into the end of its ready queue (there is one
181	priority) and return true. If the coroutine is already in the ready	331	queue for each priority) and return true. If the coro is already in
182	queue, do nothing and return false.	332	the ready queue, do nothing and return false.
183		333
		334	This ensures that the scheduler will resume this coro automatically
		335	once all the coro of higher priority and all coro of the same
		336	priority that were put into the ready queue earlier have been
		337	resumed.
		338
		339	$coro->suspend
		340	Suspends the specified coro. A suspended coro works just like any
		341	other coro, except that the scheduler will not select a suspended
		342	coro for execution.
		343
		344	Suspending a coro can be useful when you want to keep the coro from
		345	running, but you don't want to destroy it, or when you want to
		346	temporarily freeze a coro (e.g. for debugging) to resume it later.
		347
		348	A scenario for the former would be to suspend all (other) coros
		349	after a fork and keep them alive, so their destructors aren't
		350	called, but new coros can be created.
		351
		352	$coro->resume
		353	If the specified coro was suspended, it will be resumed. Note that
		354	when the coro was in the ready queue when it was suspended, it might
		355	have been unreadied by the scheduler, so an activation might have
		356	been lost.
		357
		358	To avoid this, it is best to put a suspended coro into the ready
		359	queue unconditionally, as every synchronisation mechanism must
		360	protect itself against spurious wakeups, and the one in the Coro
		361	family certainly do that.
		362
184	$is_ready = $coroutine->is_ready	363	$is_ready = $coro->is_ready
185	Return wether the coroutine is currently the ready queue or not,	364	Returns true iff the Coro object is in the ready queue. Unless the
		365	Coro object gets destroyed, it will eventually be scheduled by the
		366	scheduler.
186		367
		368	$is_running = $coro->is_running
		369	Returns true iff the Coro object is currently running. Only one Coro
		370	object can ever be in the running state (but it currently is
		371	possible to have multiple running Coro::States).
		372
		373	$is_suspended = $coro->is_suspended
		374	Returns true iff this Coro object has been suspended. Suspended
		375	Coros will not ever be scheduled.
		376
187	$coroutine->cancel (arg...)	377	$coro->cancel (arg...)
188	Terminates the given coroutine and makes it return the given	378	Terminates the given Coro and makes it return the given arguments as
189	arguments as status (default: the empty list). Never returns if the	379	status (default: the empty list). Never returns if the Coro is the
190	coroutine is the current coroutine.	380	current Coro.
191		381
192	$coroutine->join	382	$coro->schedule_to
193	Wait until the coroutine terminates and return any values given to	383	Puts the current coro to sleep (like "Coro::schedule"), but instead
194	the "terminate" or "cancel" functions. "join" can be called	384	of continuing with the next coro from the ready queue, always switch
195	concurrently from multiple coroutines.	385	to the given coro object (regardless of priority etc.). The
		386	readyness state of that coro isn't changed.
196		387
197	$coroutine->on_destroy (\&cb)	388	This is an advanced method for special cases - I'd love to hear
198	Registers a callback that is called when this coroutine gets	389	about any uses for this one.
199	destroyed, but before it is joined. The callback gets passed the
200	terminate arguments, if any.
201		390
202	$oldprio = $coroutine->prio ($newprio)	391	$coro->cede_to
203	Sets (or gets, if the argument is missing) the priority of the	392	Like "schedule_to", but puts the current coro into the ready queue.
204	coroutine. Higher priority coroutines get run before lower priority	393	This has the effect of temporarily switching to the given coro, and
205	coroutines. Priorities are small signed integers (currently -4 ..	394	continuing some time later.
206	+3), that you can refer to using PRIO_xxx constants (use the import
207	tag :prio to get then):
208		395
209	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	396	This is an advanced method for special cases - I'd love to hear
210	3 > 1 > 0 > -1 > -3 > -4	397	about any uses for this one.
211		398
212	# set priority to HIGH
213	current->prio(PRIO_HIGH);
214
215	The idle coroutine ($Coro::idle) always has a lower priority than
216	any existing coroutine.
217
218	Changing the priority of the current coroutine will take effect
219	immediately, but changing the priority of coroutines in the ready
220	queue (but not running) will only take effect after the next
221	schedule (of that coroutine). This is a bug that will be fixed in
222	some future version.
223
224	$newprio = $coroutine->nice ($change)
225	Similar to "prio", but subtract the given value from the priority
226	(i.e. higher values mean lower priority, just as in unix).
227
228	$olddesc = $coroutine->desc ($newdesc)
229	Sets (or gets in case the argument is missing) the description for
230	this coroutine. This is just a free-form string you can associate
231	with a coroutine.
232
233	This method simply sets the "$coroutine->{desc}" member to the given
234	string. You can modify this member directly if you wish.
235
236	$coroutine->throw ([$scalar])	399	$coro->throw ([$scalar])
237	If $throw is specified and defined, it will be thrown as an	400	If $throw is specified and defined, it will be thrown as an
238	exception inside the coroutine at the next convinient point in time	401	exception inside the coro at the next convenient point in time.
239	(usually after it gains control at the next schedule/transfer/cede).
240	Otherwise clears the exception object.	402	Otherwise clears the exception object.
		403
		404	Coro will check for the exception each time a schedule-like-function
		405	returns, i.e. after each "schedule", "cede",
		406	"Coro::Semaphore->down", "Coro::Handle->readable" and so on. Most of
		407	these functions detect this case and return early in case an
		408	exception is pending.
241		409
242	The exception object will be thrown "as is" with the specified	410	The exception object will be thrown "as is" with the specified
243	scalar in $@, i.e. if it is a string, no line number or newline will	411	scalar in $@, i.e. if it is a string, no line number or newline will
244	be appended (unlike with "die").	412	be appended (unlike with "die").
245		413
246	This can be used as a softer means than "cancel" to ask a coroutine	414	This can be used as a softer means than "cancel" to ask a coro to
247	to end itself, although there is no guarentee that the exception	415	end itself, although there is no guarantee that the exception will
248	will lead to termination, and if the exception isn't caught it might	416	lead to termination, and if the exception isn't caught it might well
249	well end the whole program.	417	end the whole program.
250		418
		419	You might also think of "throw" as being the moral equivalent of
		420	"kill"ing a coro with a signal (in this case, a scalar).
		421
		422	$coro->join
		423	Wait until the coro terminates and return any values given to the
		424	"terminate" or "cancel" functions. "join" can be called concurrently
		425	from multiple coro, and all will be resumed and given the status
		426	return once the $coro terminates.
		427
		428	$coro->on_destroy (\&cb)
		429	Registers a callback that is called when this coro gets destroyed,
		430	but before it is joined. The callback gets passed the terminate
		431	arguments, if any, and must not die, under any circumstances.
		432
		433	$oldprio = $coro->prio ($newprio)
		434	Sets (or gets, if the argument is missing) the priority of the coro.
		435	Higher priority coro get run before lower priority coro. Priorities
		436	are small signed integers (currently -4 .. +3), that you can refer
		437	to using PRIO_xxx constants (use the import tag :prio to get then):
		438
		439	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		440	3 > 1 > 0 > -1 > -3 > -4
		441
		442	# set priority to HIGH
		443	current->prio (PRIO_HIGH);
		444
		445	The idle coro ($Coro::idle) always has a lower priority than any
		446	existing coro.
		447
		448	Changing the priority of the current coro will take effect
		449	immediately, but changing the priority of coro in the ready queue
		450	(but not running) will only take effect after the next schedule (of
		451	that coro). This is a bug that will be fixed in some future version.
		452
		453	$newprio = $coro->nice ($change)
		454	Similar to "prio", but subtract the given value from the priority
		455	(i.e. higher values mean lower priority, just as in unix).
		456
		457	$olddesc = $coro->desc ($newdesc)
		458	Sets (or gets in case the argument is missing) the description for
		459	this coro. This is just a free-form string you can associate with a
		460	coro.
		461
		462	This method simply sets the "$coro->{desc}" member to the given
		463	string. You can modify this member directly if you wish.
		464
251	GLOBAL FUNCTIONS	465	GLOBAL FUNCTIONS
252	Coro::nready	466	Coro::nready
253	Returns the number of coroutines that are currently in the ready	467	Returns the number of coro that are currently in the ready state,
254	state, i.e. that can be switched to. The value 0 means that the only	468	i.e. that can be switched to by calling "schedule" directory or
255	runnable coroutine is the currently running one, so "cede" would	469	indirectly. The value 0 means that the only runnable coro is the
256	have no effect, and "schedule" would cause a deadlock unless there	470	currently running one, so "cede" would have no effect, and
257	is an idle handler that wakes up some coroutines.	471	"schedule" would cause a deadlock unless there is an idle handler
		472	that wakes up some coro.
258		473
259	my $guard = Coro::guard { ... }	474	my $guard = Coro::guard { ... }
260	This creates and returns a guard object. Nothing happens until the	475	This function still exists, but is deprecated. Please use the
261	object gets destroyed, in which case the codeblock given as argument	476	"Guard::guard" function instead.
262	will be executed. This is useful to free locks or other resources in
263	case of a runtime error or when the coroutine gets canceled, as in
264	both cases the guard block will be executed. The guard object
265	supports only one method, "->cancel", which will keep the codeblock
266	from being executed.
267
268	Example: set some flag and clear it again when the coroutine gets
269	canceled or the function returns:
270
271	sub do_something {
272	my $guard = Coro::guard { $busy = 0 };
273	$busy = 1;
274
275	# do something that requires $busy to be true
276	}
277		477
278	unblock_sub { ... }	478	unblock_sub { ... }
279	This utility function takes a BLOCK or code reference and "unblocks"	479	This utility function takes a BLOCK or code reference and "unblocks"
280	it, returning the new coderef. This means that the new coderef will	480	it, returning a new coderef. Unblocking means that calling the new
281	return immediately without blocking, returning nothing, while the	481	coderef will return immediately without blocking, returning nothing,
282	original code ref will be called (with parameters) from within its	482	while the original code ref will be called (with parameters) from
283	own coroutine.	483	within another coro.
284		484
285	The reason this function exists is that many event libraries (such	485	The reason this function exists is that many event libraries (such
286	as the venerable Event module) are not coroutine-safe (a weaker form	486	as the venerable Event module) are not thread-safe (a weaker form of
287	of thread-safety). This means you must not block within event	487	reentrancy). This means you must not block within event callbacks,
288	callbacks, otherwise you might suffer from crashes or worse.	488	otherwise you might suffer from crashes or worse. The only event
		489	library currently known that is safe to use without "unblock_sub" is
		490	EV.
289		491
290	This function allows your callbacks to block by executing them in	492	This function allows your callbacks to block by executing them in
291	another coroutine where it is safe to block. One example where	493	another coro where it is safe to block. One example where blocking
292	blocking is handy is when you use the Coro::AIO functions to save	494	is handy is when you use the Coro::AIO functions to save results to
293	results to disk.	495	disk, for example.
294		496
295	In short: simply use "unblock_sub { ... }" instead of "sub { ... }"	497	In short: simply use "unblock_sub { ... }" instead of "sub { ... }"
296	when creating event callbacks that want to block.	498	when creating event callbacks that want to block.
297		499
		500	If your handler does not plan to block (e.g. simply sends a message
		501	to another coro, or puts some other coro into the ready queue),
		502	there is no reason to use "unblock_sub".
		503
		504	Note that you also need to use "unblock_sub" for any other callbacks
		505	that are indirectly executed by any C-based event loop. For example,
		506	when you use a module that uses AnyEvent (and you use
		507	Coro::AnyEvent) and it provides callbacks that are the result of
		508	some event callback, then you must not block either, or use
		509	"unblock_sub".
		510
		511	$cb = Coro::rouse_cb
		512	Create and return a "rouse callback". That's a code reference that,
		513	when called, will remember a copy of its arguments and notify the
		514	owner coro of the callback.
		515
		516	See the next function.
		517
		518	@args = Coro::rouse_wait [$cb]
		519	Wait for the specified rouse callback (or the last one that was
		520	created in this coro).
		521
		522	As soon as the callback is invoked (or when the callback was invoked
		523	before "rouse_wait"), it will return the arguments originally passed
		524	to the rouse callback.
		525
		526	See the section HOW TO WAIT FOR A CALLBACK for an actual usage
		527	example.
		528
		529	HOW TO WAIT FOR A CALLBACK
		530	It is very common for a coro to wait for some callback to be called.
		531	This occurs naturally when you use coro in an otherwise event-based
		532	program, or when you use event-based libraries.
		533
		534	These typically register a callback for some event, and call that
		535	callback when the event occured. In a coro, however, you typically want
		536	to just wait for the event, simplyifying things.
		537
		538	For example "AnyEvent->child" registers a callback to be called when a
		539	specific child has exited:
		540
		541	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		542
		543	But from within a coro, you often just want to write this:
		544
		545	my $status = wait_for_child $pid;
		546
		547	Coro offers two functions specifically designed to make this easy,
		548	"Coro::rouse_cb" and "Coro::rouse_wait".
		549
		550	The first function, "rouse_cb", generates and returns a callback that,
		551	when invoked, will save its arguments and notify the coro that created
		552	the callback.
		553
		554	The second function, "rouse_wait", waits for the callback to be called
		555	(by calling "schedule" to go to sleep) and returns the arguments
		556	originally passed to the callback.
		557
		558	Using these functions, it becomes easy to write the "wait_for_child"
		559	function mentioned above:
		560
		561	sub wait_for_child($) {
		562	my ($pid) = @_;
		563
		564	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		565
		566	my ($rpid, $rstatus) = Coro::rouse_wait;
		567	$rstatus
		568	}
		569
		570	In the case where "rouse_cb" and "rouse_wait" are not flexible enough,
		571	you can roll your own, using "schedule":
		572
		573	sub wait_for_child($) {
		574	my ($pid) = @_;
		575
		576	# store the current coro in $current,
		577	# and provide result variables for the closure passed to ->child
		578	my $current = $Coro::current;
		579	my ($done, $rstatus);
		580
		581	# pass a closure to ->child
		582	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		583	$rstatus = $_[1]; # remember rstatus
		584	$done = 1; # mark $rstatus as valud
		585	});
		586
		587	# wait until the closure has been called
		588	schedule while !$done;
		589
		590	$rstatus
		591	}
		592
298	BUGS/LIMITATIONS	593	BUGS/LIMITATIONS
299	- you must make very sure that no coro is still active on global	594	fork with pthread backend
300	destruction. very bad things might happen otherwise (usually segfaults).	595	When Coro is compiled using the pthread backend (which isn't
		596	recommended but required on many BSDs as their libcs are completely
		597	broken), then coro will not survive a fork. There is no known
		598	workaround except to fix your libc and use a saner backend.
301		599
		600	perl process emulation ("threads")
302	- this module is not thread-safe. You should only ever use this module	601	This module is not perl-pseudo-thread-safe. You should only ever use
303	from the same thread (this requirement might be loosened in the future	602	this module from the first thread (this requirement might be removed
304	to allow per-thread schedulers, but Coro::State does not yet allow	603	in the future to allow per-thread schedulers, but Coro::State does
305	this).	604	not yet allow this). I recommend disabling thread support and using
		605	processes, as having the windows process emulation enabled under
		606	unix roughly halves perl performance, even when not used.
		607
		608	coro switching is not signal safe
		609	You must not switch to another coro from within a signal handler
		610	(only relevant with %SIG - most event libraries provide safe
		611	signals).
		612
		613	That means you MUST NOT call any function that might "block" the
		614	current coro - "cede", "schedule" "Coro::Semaphore->down" or
		615	anything that calls those. Everything else, including calling
		616	"ready", works.
306		617
307	SEE ALSO	618	SEE ALSO
308	Lower level Configuration, Coroutine Environment: Coro::State.	619	Event-Loop integration: Coro::AnyEvent, Coro::EV, Coro::Event.
309		620
310	Debugging: Coro::Debug.	621	Debugging: Coro::Debug.
311		622
312	Support/Utility: Coro::Specific, Coro::Util.	623	Support/Utility: Coro::Specific, Coro::Util.
313		624
314	Locking/IPC: Coro::Signal, Coro::Channel, Coro::Semaphore,	625	Locking and IPC: Coro::Signal, Coro::Channel, Coro::Semaphore,
315	Coro::SemaphoreSet, Coro::RWLock.	626	Coro::SemaphoreSet, Coro::RWLock.
316		627
317	Event/IO: Coro::Timer, Coro::Event, Coro::Handle, Coro::Socket.	628	I/O and Timers: Coro::Timer, Coro::Handle, Coro::Socket, Coro::AIO.
318		629
319	Compatibility: Coro::LWP, Coro::Storable, Coro::Select.	630	Compatibility with other modules: Coro::LWP (but see also AnyEvent::HTTP
		631	for a better-working alternative), Coro::BDB, Coro::Storable,
		632	Coro::Select.
320		633
321	Embedding: <Coro:MakeMaker>.	634	XS API: Coro::MakeMaker.
		635
		636	Low level Configuration, Thread Environment, Continuations: Coro::State.
322		637
323	AUTHOR	638	AUTHOR
324	Marc Lehmann <schmorp@schmorp.de>	639	Marc Lehmann <schmorp@schmorp.de>
325	http://home.schmorp.de/	640	http://home.schmorp.de/
326		641

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Revision 1.24 by root, Tue Jun 23 23:40:06 2009 UTC