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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 coro switching considerably for coros that use them
		244	(But coro switching is still reasonably fast if the handlers are
		245	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 changes 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
152	Coro::cede_notself
153	Works like cede, but is not exported by default and will cede to any
154	coroutine, regardless of priority, once.
155
156	terminate [arg...]
157	Terminates the current coroutine with the given status values (see
158	cancel).
159		278
160	killall	279	killall
161	Kills/terminates/cancels all coroutines except the currently running	280	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		281
165	# dynamic methods	282	Note that while this will try to free some of the main interpreter
		283	resources if the calling coro isn't the main coro, but one cannot
		284	free all of them, so if a coro that is not the main coro calls this
		285	function, there will be some one-time resource leak.
166		286
167	COROUTINE METHODS	287	CORO OBJECT METHODS
168	These are the methods you can call on coroutine objects.	288	These are the methods you can call on coro objects (or to create them).
169		289
170	new Coro \&sub [, @args...]	290	new Coro \&sub [, @args...]
171	Create a new coroutine and return it. When the sub returns the	291	Create a new coro and return it. When the sub returns, the coro
172	coroutine automatically terminates as if "terminate" with the	292	automatically terminates as if "terminate" with the returned values
173	returned values were called. To make the coroutine run you must	293	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.	294	ready queue by calling the ready method.
175		295
176	See "async" and "Coro::State::new" for additional info about the	296	See "async" and "Coro::State::new" for additional info about the
177	coroutine environment.	297	coro environment.
178		298
179	$success = $coroutine->ready	299	$success = $coro->ready
180	Put the given coroutine into the ready queue (according to it's	300	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	301	queue for each priority) and return true. If the coro is already in
182	queue, do nothing and return false.	302	the ready queue, do nothing and return false.
183		303
		304	This ensures that the scheduler will resume this coro automatically
		305	once all the coro of higher priority and all coro of the same
		306	priority that were put into the ready queue earlier have been
		307	resumed.
		308
184	$is_ready = $coroutine->is_ready	309	$is_ready = $coro->is_ready
185	Return wether the coroutine is currently the ready queue or not,	310	Returns true iff the Coro object is in the ready queue. Unless the
		311	Coro object gets destroyed, it will eventually be scheduled by the
		312	scheduler.
186		313
		314	$is_running = $coro->is_running
		315	Returns true iff the Coro object is currently running. Only one Coro
		316	object can ever be in the running state (but it currently is
		317	possible to have multiple running Coro::States).
		318
		319	$is_suspended = $coro->is_suspended
		320	Returns true iff this Coro object has been suspended. Suspended
		321	Coros will not ever be scheduled.
		322
187	$coroutine->cancel (arg...)	323	$coro->cancel (arg...)
188	Terminates the given coroutine and makes it return the given	324	Terminates the given Coro and makes it return the given arguments as
189	arguments as status (default: the empty list). Never returns if the	325	status (default: the empty list). Never returns if the Coro is the
190	coroutine is the current coroutine.	326	current Coro.
191		327
192	$coroutine->join	328	$coro->schedule_to
193	Wait until the coroutine terminates and return any values given to	329	Puts the current coro to sleep (like "Coro::schedule"), but instead
194	the "terminate" or "cancel" functions. "join" can be called	330	of continuing with the next coro from the ready queue, always switch
195	concurrently from multiple coroutines.	331	to the given coro object (regardless of priority etc.). The
		332	readyness state of that coro isn't changed.
196		333
197	$coroutine->on_destroy (\&cb)	334	This is an advanced method for special cases - I'd love to hear
198	Registers a callback that is called when this coroutine gets	335	about any uses for this one.
199	destroyed, but before it is joined. The callback gets passed the
200	terminate arguments, if any.
201		336
202	$oldprio = $coroutine->prio ($newprio)	337	$coro->cede_to
203	Sets (or gets, if the argument is missing) the priority of the	338	Like "schedule_to", but puts the current coro into the ready queue.
204	coroutine. Higher priority coroutines get run before lower priority	339	This has the effect of temporarily switching to the given coro, and
205	coroutines. Priorities are small signed integers (currently -4 ..	340	continuing some time later.
206	+3), that you can refer to using PRIO_xxx constants (use the import
207	tag :prio to get then):
208		341
209	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN	342	This is an advanced method for special cases - I'd love to hear
210	3 > 1 > 0 > -1 > -3 > -4	343	about any uses for this one.
211		344
212	# set priority to HIGH
213	current->prio(PRIO_HIGH);
214
215	The idle coroutine ($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])	345	$coro->throw ([$scalar])
237	If $throw is specified and defined, it will be thrown as an	346	If $throw is specified and defined, it will be thrown as an
238	exception inside the coroutine at the next convinient point in time	347	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.	348	Otherwise clears the exception object.
		349
		350	Coro will check for the exception each time a schedule-like-function
		351	returns, i.e. after each "schedule", "cede",
		352	"Coro::Semaphore->down", "Coro::Handle->readable" and so on. Most of
		353	these functions detect this case and return early in case an
		354	exception is pending.
241		355
242	The exception object will be thrown "as is" with the specified	356	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	357	scalar in $@, i.e. if it is a string, no line number or newline will
244	be appended (unlike with "die").	358	be appended (unlike with "die").
245		359
246	This can be used as a softer means than "cancel" to ask a coroutine	360	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	361	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	362	lead to termination, and if the exception isn't caught it might well
249	well end the whole program.	363	end the whole program.
250		364
		365	You might also think of "throw" as being the moral equivalent of
		366	"kill"ing a coro with a signal (in this case, a scalar).
		367
		368	$coro->join
		369	Wait until the coro terminates and return any values given to the
		370	"terminate" or "cancel" functions. "join" can be called concurrently
		371	from multiple coro, and all will be resumed and given the status
		372	return once the $coro terminates.
		373
		374	$coro->on_destroy (\&cb)
		375	Registers a callback that is called when this coro gets destroyed,
		376	but before it is joined. The callback gets passed the terminate
		377	arguments, if any, and must not die, under any circumstances.
		378
		379	$oldprio = $coro->prio ($newprio)
		380	Sets (or gets, if the argument is missing) the priority of the coro.
		381	Higher priority coro get run before lower priority coro. Priorities
		382	are small signed integers (currently -4 .. +3), that you can refer
		383	to using PRIO_xxx constants (use the import tag :prio to get then):
		384
		385	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
		386	3 > 1 > 0 > -1 > -3 > -4
		387
		388	# set priority to HIGH
		389	current->prio (PRIO_HIGH);
		390
		391	The idle coro ($Coro::idle) always has a lower priority than any
		392	existing coro.
		393
		394	Changing the priority of the current coro will take effect
		395	immediately, but changing the priority of coro in the ready queue
		396	(but not running) will only take effect after the next schedule (of
		397	that coro). This is a bug that will be fixed in some future version.
		398
		399	$newprio = $coro->nice ($change)
		400	Similar to "prio", but subtract the given value from the priority
		401	(i.e. higher values mean lower priority, just as in unix).
		402
		403	$olddesc = $coro->desc ($newdesc)
		404	Sets (or gets in case the argument is missing) the description for
		405	this coro. This is just a free-form string you can associate with a
		406	coro.
		407
		408	This method simply sets the "$coro->{desc}" member to the given
		409	string. You can modify this member directly if you wish.
		410
251	GLOBAL FUNCTIONS	411	GLOBAL FUNCTIONS
252	Coro::nready	412	Coro::nready
253	Returns the number of coroutines that are currently in the ready	413	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	414	i.e. that can be switched to by calling "schedule" directory or
255	runnable coroutine is the currently running one, so "cede" would	415	indirectly. The value 0 means that the only runnable coro is the
256	have no effect, and "schedule" would cause a deadlock unless there	416	currently running one, so "cede" would have no effect, and
257	is an idle handler that wakes up some coroutines.	417	"schedule" would cause a deadlock unless there is an idle handler
		418	that wakes up some coro.
258		419
259	my $guard = Coro::guard { ... }	420	my $guard = Coro::guard { ... }
260	This creates and returns a guard object. Nothing happens until the	421	This function still exists, but is deprecated. Please use the
261	object gets destroyed, in which case the codeblock given as argument	422	"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		423
278	unblock_sub { ... }	424	unblock_sub { ... }
279	This utility function takes a BLOCK or code reference and "unblocks"	425	This utility function takes a BLOCK or code reference and "unblocks"
280	it, returning the new coderef. This means that the new coderef will	426	it, returning a new coderef. Unblocking means that calling the new
281	return immediately without blocking, returning nothing, while the	427	coderef will return immediately without blocking, returning nothing,
282	original code ref will be called (with parameters) from within its	428	while the original code ref will be called (with parameters) from
283	own coroutine.	429	within another coro.
284		430
285	The reason this function exists is that many event libraries (such	431	The reason this function exists is that many event libraries (such
286	as the venerable Event module) are not coroutine-safe (a weaker form	432	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	433	reentrancy). This means you must not block within event callbacks,
288	callbacks, otherwise you might suffer from crashes or worse.	434	otherwise you might suffer from crashes or worse. The only event
		435	library currently known that is safe to use without "unblock_sub" is
		436	EV.
289		437
290	This function allows your callbacks to block by executing them in	438	This function allows your callbacks to block by executing them in
291	another coroutine where it is safe to block. One example where	439	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	440	is handy is when you use the Coro::AIO functions to save results to
293	results to disk.	441	disk, for example.
294		442
295	In short: simply use "unblock_sub { ... }" instead of "sub { ... }"	443	In short: simply use "unblock_sub { ... }" instead of "sub { ... }"
296	when creating event callbacks that want to block.	444	when creating event callbacks that want to block.
297		445
		446	If your handler does not plan to block (e.g. simply sends a message
		447	to another coro, or puts some other coro into the ready queue),
		448	there is no reason to use "unblock_sub".
		449
		450	Note that you also need to use "unblock_sub" for any other callbacks
		451	that are indirectly executed by any C-based event loop. For example,
		452	when you use a module that uses AnyEvent (and you use
		453	Coro::AnyEvent) and it provides callbacks that are the result of
		454	some event callback, then you must not block either, or use
		455	"unblock_sub".
		456
		457	$cb = Coro::rouse_cb
		458	Create and return a "rouse callback". That's a code reference that,
		459	when called, will remember a copy of its arguments and notify the
		460	owner coro of the callback.
		461
		462	See the next function.
		463
		464	@args = Coro::rouse_wait [$cb]
		465	Wait for the specified rouse callback (or the last one that was
		466	created in this coro).
		467
		468	As soon as the callback is invoked (or when the callback was invoked
		469	before "rouse_wait"), it will return the arguments originally passed
		470	to the rouse callback.
		471
		472	See the section HOW TO WAIT FOR A CALLBACK for an actual usage
		473	example.
		474
		475	HOW TO WAIT FOR A CALLBACK
		476	It is very common for a coro to wait for some callback to be called.
		477	This occurs naturally when you use coro in an otherwise event-based
		478	program, or when you use event-based libraries.
		479
		480	These typically register a callback for some event, and call that
		481	callback when the event occured. In a coro, however, you typically want
		482	to just wait for the event, simplyifying things.
		483
		484	For example "AnyEvent->child" registers a callback to be called when a
		485	specific child has exited:
		486
		487	my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... });
		488
		489	But from within a coro, you often just want to write this:
		490
		491	my $status = wait_for_child $pid;
		492
		493	Coro offers two functions specifically designed to make this easy,
		494	"Coro::rouse_cb" and "Coro::rouse_wait".
		495
		496	The first function, "rouse_cb", generates and returns a callback that,
		497	when invoked, will save its arguments and notify the coro that created
		498	the callback.
		499
		500	The second function, "rouse_wait", waits for the callback to be called
		501	(by calling "schedule" to go to sleep) and returns the arguments
		502	originally passed to the callback.
		503
		504	Using these functions, it becomes easy to write the "wait_for_child"
		505	function mentioned above:
		506
		507	sub wait_for_child($) {
		508	my ($pid) = @_;
		509
		510	my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
		511
		512	my ($rpid, $rstatus) = Coro::rouse_wait;
		513	$rstatus
		514	}
		515
		516	In the case where "rouse_cb" and "rouse_wait" are not flexible enough,
		517	you can roll your own, using "schedule":
		518
		519	sub wait_for_child($) {
		520	my ($pid) = @_;
		521
		522	# store the current coro in $current,
		523	# and provide result variables for the closure passed to ->child
		524	my $current = $Coro::current;
		525	my ($done, $rstatus);
		526
		527	# pass a closure to ->child
		528	my $watcher = AnyEvent->child (pid => $pid, cb => sub {
		529	$rstatus = $_[1]; # remember rstatus
		530	$done = 1; # mark $rstatus as valud
		531	});
		532
		533	# wait until the closure has been called
		534	schedule while !$done;
		535
		536	$rstatus
		537	}
		538
298	BUGS/LIMITATIONS	539	BUGS/LIMITATIONS
299	- you must make very sure that no coro is still active on global	540	fork with pthread backend
300	destruction. very bad things might happen otherwise (usually segfaults).	541	When Coro is compiled using the pthread backend (which isn't
		542	recommended but required on many BSDs as their libcs are completely
		543	broken), then coro will not survive a fork. There is no known
		544	workaround except to fix your libc and use a saner backend.
301		545
		546	perl process emulation ("threads")
302	- this module is not thread-safe. You should only ever use this module	547	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	548	this module from the first thread (this requirement might be removed
304	to allow per-thread schedulers, but Coro::State does not yet allow	549	in the future to allow per-thread schedulers, but Coro::State does
305	this).	550	not yet allow this). I recommend disabling thread support and using
		551	processes, as having the windows process emulation enabled under
		552	unix roughly halves perl performance, even when not used.
		553
		554	coro switching is not signal safe
		555	You must not switch to another coro from within a signal handler
		556	(only relevant with %SIG - most event libraries provide safe
		557	signals).
		558
		559	That means you MUST NOT call any function that might "block" the
		560	current coro - "cede", "schedule" "Coro::Semaphore->down" or
		561	anything that calls those. Everything else, including calling
		562	"ready", works.
306		563
307	SEE ALSO	564	SEE ALSO
308	Lower level Configuration, Coroutine Environment: Coro::State.	565	Event-Loop integration: Coro::AnyEvent, Coro::EV, Coro::Event.
309		566
310	Debugging: Coro::Debug.	567	Debugging: Coro::Debug.
311		568
312	Support/Utility: Coro::Specific, Coro::Util.	569	Support/Utility: Coro::Specific, Coro::Util.
313		570
314	Locking/IPC: Coro::Signal, Coro::Channel, Coro::Semaphore,	571	Locking and IPC: Coro::Signal, Coro::Channel, Coro::Semaphore,
315	Coro::SemaphoreSet, Coro::RWLock.	572	Coro::SemaphoreSet, Coro::RWLock.
316		573
317	Event/IO: Coro::Timer, Coro::Event, Coro::Handle, Coro::Socket.	574	I/O and Timers: Coro::Timer, Coro::Handle, Coro::Socket, Coro::AIO.
318		575
319	Compatibility: Coro::LWP, Coro::Storable, Coro::Select.	576	Compatibility with other modules: Coro::LWP (but see also AnyEvent::HTTP
		577	for a better-working alternative), Coro::BDB, Coro::Storable,
		578	Coro::Select.
320		579
321	Embedding: <Coro:MakeMaker>.	580	XS API: Coro::MakeMaker.
		581
		582	Low level Configuration, Thread Environment, Continuations: Coro::State.
322		583
323	AUTHOR	584	AUTHOR
324	Marc Lehmann <schmorp@schmorp.de>	585	Marc Lehmann <schmorp@schmorp.de>
325	http://home.schmorp.de/	586	http://home.schmorp.de/
326		587

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Revision 1.21 by root, Mon Dec 15 20:52:04 2008 UTC