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

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