[ViewVC] Diff of: cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.249 by root, Wed Jul 8 04:29:31 2009 UTC vs.
Revision 1.279 by root, Mon Feb 15 05:15:55 2010 UTC

…		…
98	=head2 FEATURES	98	=head2 FEATURES
99		99
100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
103	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
104	with customised rescheduling (C<ev_periodic>), synchronous signals	104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
105	(C<ev_signal>), process status change events (C<ev_child>), and event	105	timers (C<ev_timer>), absolute timers with customised rescheduling
106	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
107	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	107	change events (C<ev_child>), and event watchers dealing with the event
108	file watchers (C<ev_stat>) and even limited support for fork events	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
109	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
110		111
111	It also is quite fast (see this	112	It also is quite fast (see this
112	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent
113	for example).	114	for example).
114		115
…		…
117	Libev is very configurable. In this manual the default (and most common)	118	Libev is very configurable. In this manual the default (and most common)
118	configuration will be described, which supports multiple event loops. For	119	configuration will be described, which supports multiple event loops. For
119	more info about various configuration options please have a look at	120	more info about various configuration options please have a look at
120	B<EMBED> section in this manual. If libev was configured without support	121	B<EMBED> section in this manual. If libev was configured without support
121	for multiple event loops, then all functions taking an initial argument of	122	for multiple event loops, then all functions taking an initial argument of
122	name C<loop> (which is always of type C<ev_loop *>) will not have	123	name C<loop> (which is always of type C<struct ev_loop *>) will not have
123	this argument.	124	this argument.
124		125
125	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
126		127
127	Libev represents time as a single floating point number, representing	128	Libev represents time as a single floating point number, representing
…		…
362	flag.	363	flag.
363		364
364	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
365	environment variable.	366	environment variable.
366		367
		368	=item C<EVFLAG_NOINOTIFY>
		369
		370	When this flag is specified, then libev will not attempt to use the
		371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		372	testing, this flag can be useful to conserve inotify file descriptors, as
		373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		374
		375	=item C<EVFLAG_SIGNALFD>
		376
		377	When this flag is specified, then libev will attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		379	delivers signals synchronously, which makes it both faster and might make
		380	it possible to get the queued signal data. It can also simplify signal
		381	handling with threads, as long as you properly block signals in your
		382	threads that are not interested in handling them.
		383
		384	Signalfd will not be used by default as this changes your signal mask, and
		385	there are a lot of shoddy libraries and programs (glib's threadpool for
		386	example) that can't properly initialise their signal masks.
		387
367	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
368		389
369	This is your standard select(2) backend. Not I<completely> standard, as	390	This is your standard select(2) backend. Not I<completely> standard, as
370	libev tries to roll its own fd_set with no limits on the number of fds,	391	libev tries to roll its own fd_set with no limits on the number of fds,
371	but if that fails, expect a fairly low limit on the number of fds when	392	but if that fails, expect a fairly low limit on the number of fds when
…		…
394		415
395	This backend maps C<EV_READ> to C<POLLIN \| POLLERR \| POLLHUP>, and	416	This backend maps C<EV_READ> to C<POLLIN \| POLLERR \| POLLHUP>, and
396	C<EV_WRITE> to C<POLLOUT \| POLLERR \| POLLHUP>.	417	C<EV_WRITE> to C<POLLOUT \| POLLERR \| POLLHUP>.
397		418
398	=item C<EVBACKEND_EPOLL> (value 4, Linux)	419	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		420
		421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		422	kernels).
399		423
400	For few fds, this backend is a bit little slower than poll and select,	424	For few fds, this backend is a bit little slower than poll and select,
401	but it scales phenomenally better. While poll and select usually scale	425	but it scales phenomenally better. While poll and select usually scale
402	like O(total_fds) where n is the total number of fds (or the highest fd),	426	like O(total_fds) where n is the total number of fds (or the highest fd),
403	epoll scales either O(1) or O(active_fds).	427	epoll scales either O(1) or O(active_fds).
…		…
518		542
519	It is definitely not recommended to use this flag.	543	It is definitely not recommended to use this flag.
520		544
521	=back	545	=back
522		546
523	If one or more of these are or'ed into the flags value, then only these	547	If one or more of the backend flags are or'ed into the flags value,
524	backends will be tried (in the reverse order as listed here). If none are	548	then only these backends will be tried (in the reverse order as listed
525	specified, all backends in C<ev_recommended_backends ()> will be tried.	549	here). If none are specified, all backends in C<ev_recommended_backends
		550	()> will be tried.
526		551
527	Example: This is the most typical usage.	552	Example: This is the most typical usage.
528		553
529	if (!ev_default_loop (0))	554	if (!ev_default_loop (0))
530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
573	as signal and child watchers) would need to be stopped manually.	598	as signal and child watchers) would need to be stopped manually.
574		599
575	In general it is not advisable to call this function except in the	600	In general it is not advisable to call this function except in the
576	rare occasion where you really need to free e.g. the signal handling	601	rare occasion where you really need to free e.g. the signal handling
577	pipe fds. If you need dynamically allocated loops it is better to use	602	pipe fds. If you need dynamically allocated loops it is better to use
578	C<ev_loop_new> and C<ev_loop_destroy>).	603	C<ev_loop_new> and C<ev_loop_destroy>.
579		604
580	=item ev_loop_destroy (loop)	605	=item ev_loop_destroy (loop)
581		606
582	Like C<ev_default_destroy>, but destroys an event loop created by an	607	Like C<ev_default_destroy>, but destroys an event loop created by an
583	earlier call to C<ev_loop_new>.	608	earlier call to C<ev_loop_new>.
…		…
687	event loop time (see C<ev_now_update>).	712	event loop time (see C<ev_now_update>).
688		713
689	=item ev_loop (loop, int flags)	714	=item ev_loop (loop, int flags)
690		715
691	Finally, this is it, the event handler. This function usually is called	716	Finally, this is it, the event handler. This function usually is called
692	after you initialised all your watchers and you want to start handling	717	after you have initialised all your watchers and you want to start
693	events.	718	handling events.
694		719
695	If the flags argument is specified as C<0>, it will not return until	720	If the flags argument is specified as C<0>, it will not return until
696	either no event watchers are active anymore or C<ev_unloop> was called.	721	either no event watchers are active anymore or C<ev_unloop> was called.
697		722
698	Please note that an explicit C<ev_unloop> is usually better than	723	Please note that an explicit C<ev_unloop> is usually better than
…		…
772		797
773	Ref/unref can be used to add or remove a reference count on the event	798	Ref/unref can be used to add or remove a reference count on the event
774	loop: Every watcher keeps one reference, and as long as the reference	799	loop: Every watcher keeps one reference, and as long as the reference
775	count is nonzero, C<ev_loop> will not return on its own.	800	count is nonzero, C<ev_loop> will not return on its own.
776		801
777	If you have a watcher you never unregister that should not keep C<ev_loop>	802	This is useful when you have a watcher that you never intend to
778	from returning, call ev_unref() after starting, and ev_ref() before	803	unregister, but that nevertheless should not keep C<ev_loop> from
		804	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
779	stopping it.	805	before stopping it.
780		806
781	As an example, libev itself uses this for its internal signal pipe: It	807	As an example, libev itself uses this for its internal signal pipe: It
782	is not visible to the libev user and should not keep C<ev_loop> from	808	is not visible to the libev user and should not keep C<ev_loop> from
783	exiting if no event watchers registered by it are active. It is also an	809	exiting if no event watchers registered by it are active. It is also an
784	excellent way to do this for generic recurring timers or from within	810	excellent way to do this for generic recurring timers or from within
…		…
856	more often than 100 times per second:	882	more often than 100 times per second:
857		883
858	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);	884	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	885	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
860		886
		887	=item ev_invoke_pending (loop)
		888
		889	This call will simply invoke all pending watchers while resetting their
		890	pending state. Normally, C<ev_loop> does this automatically when required,
		891	but when overriding the invoke callback this call comes handy.
		892
		893	=item int ev_pending_count (loop)
		894
		895	Returns the number of pending watchers - zero indicates that no watchers
		896	are pending.
		897
		898	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		899
		900	This overrides the invoke pending functionality of the loop: Instead of
		901	invoking all pending watchers when there are any, C<ev_loop> will call
		902	this callback instead. This is useful, for example, when you want to
		903	invoke the actual watchers inside another context (another thread etc.).
		904
		905	If you want to reset the callback, use C<ev_invoke_pending> as new
		906	callback.
		907
		908	=item ev_set_loop_release_cb (loop, void (release)(EV_P), void (acquire)(EV_P))
		909
		910	Sometimes you want to share the same loop between multiple threads. This
		911	can be done relatively simply by putting mutex_lock/unlock calls around
		912	each call to a libev function.
		913
		914	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		915	wait for it to return. One way around this is to wake up the loop via
		916	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		917	and I<acquire> callbacks on the loop.
		918
		919	When set, then C<release> will be called just before the thread is
		920	suspended waiting for new events, and C<acquire> is called just
		921	afterwards.
		922
		923	Ideally, C<release> will just call your mutex_unlock function, and
		924	C<acquire> will just call the mutex_lock function again.
		925
		926	While event loop modifications are allowed between invocations of
		927	C<release> and C<acquire> (that's their only purpose after all), no
		928	modifications done will affect the event loop, i.e. adding watchers will
		929	have no effect on the set of file descriptors being watched, or the time
		930	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		931	to take note of any changes you made.
		932
		933	In theory, threads executing C<ev_loop> will be async-cancel safe between
		934	invocations of C<release> and C<acquire>.
		935
		936	See also the locking example in the C<THREADS> section later in this
		937	document.
		938
		939	=item ev_set_userdata (loop, void *data)
		940
		941	=item ev_userdata (loop)
		942
		943	Set and retrieve a single C<void *> associated with a loop. When
		944	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		945	C<0.>
		946
		947	These two functions can be used to associate arbitrary data with a loop,
		948	and are intended solely for the C<invoke_pending_cb>, C<release> and
		949	C<acquire> callbacks described above, but of course can be (ab-)used for
		950	any other purpose as well.
		951
861	=item ev_loop_verify (loop)	952	=item ev_loop_verify (loop)
862		953
863	This function only does something when C<EV_VERIFY> support has been	954	This function only does something when C<EV_VERIFY> support has been
864	compiled in, which is the default for non-minimal builds. It tries to go	955	compiled in, which is the default for non-minimal builds. It tries to go
865	through all internal structures and checks them for validity. If anything	956	through all internal structures and checks them for validity. If anything
…		…
1041		1132
1042	ev_io w;	1133	ev_io w;
1043	ev_init (&w, my_cb);	1134	ev_init (&w, my_cb);
1044	ev_io_set (&w, STDIN_FILENO, EV_READ);	1135	ev_io_set (&w, STDIN_FILENO, EV_READ);
1045		1136
1046	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1137	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1047		1138
1048	This macro initialises the type-specific parts of a watcher. You need to	1139	This macro initialises the type-specific parts of a watcher. You need to
1049	call C<ev_init> at least once before you call this macro, but you can	1140	call C<ev_init> at least once before you call this macro, but you can
1050	call C<ev_TYPE_set> any number of times. You must not, however, call this	1141	call C<ev_TYPE_set> any number of times. You must not, however, call this
1051	macro on a watcher that is active (it can be pending, however, which is a	1142	macro on a watcher that is active (it can be pending, however, which is a
…		…
1064		1155
1065	Example: Initialise and set an C<ev_io> watcher in one step.	1156	Example: Initialise and set an C<ev_io> watcher in one step.
1066		1157
1067	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1158	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1068		1159
1069	=item C<ev_TYPE_start> (loop , ev_TYPE watcher)	1160	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1070		1161
1071	Starts (activates) the given watcher. Only active watchers will receive	1162	Starts (activates) the given watcher. Only active watchers will receive
1072	events. If the watcher is already active nothing will happen.	1163	events. If the watcher is already active nothing will happen.
1073		1164
1074	Example: Start the C<ev_io> watcher that is being abused as example in this	1165	Example: Start the C<ev_io> watcher that is being abused as example in this
1075	whole section.	1166	whole section.
1076		1167
1077	ev_io_start (EV_DEFAULT_UC, &w);	1168	ev_io_start (EV_DEFAULT_UC, &w);
1078		1169
1079	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)	1170	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1080		1171
1081	Stops the given watcher if active, and clears the pending status (whether	1172	Stops the given watcher if active, and clears the pending status (whether
1082	the watcher was active or not).	1173	the watcher was active or not).
1083		1174
1084	It is possible that stopped watchers are pending - for example,	1175	It is possible that stopped watchers are pending - for example,
…		…
1109	=item ev_cb_set (ev_TYPE *watcher, callback)	1200	=item ev_cb_set (ev_TYPE *watcher, callback)
1110		1201
1111	Change the callback. You can change the callback at virtually any time	1202	Change the callback. You can change the callback at virtually any time
1112	(modulo threads).	1203	(modulo threads).
1113		1204
1114	=item ev_set_priority (ev_TYPE *watcher, priority)	1205	=item ev_set_priority (ev_TYPE *watcher, int priority)
1115		1206
1116	=item int ev_priority (ev_TYPE *watcher)	1207	=item int ev_priority (ev_TYPE *watcher)
1117		1208
1118	Set and query the priority of the watcher. The priority is a small	1209	Set and query the priority of the watcher. The priority is a small
1119	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1210	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1150	returns its C<revents> bitset (as if its callback was invoked). If the	1241	returns its C<revents> bitset (as if its callback was invoked). If the
1151	watcher isn't pending it does nothing and returns C<0>.	1242	watcher isn't pending it does nothing and returns C<0>.
1152		1243
1153	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1244	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1154	callback to be invoked, which can be accomplished with this function.	1245	callback to be invoked, which can be accomplished with this function.
		1246
		1247	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1248
		1249	Feeds the given event set into the event loop, as if the specified event
		1250	had happened for the specified watcher (which must be a pointer to an
		1251	initialised but not necessarily started event watcher). Obviously you must
		1252	not free the watcher as long as it has pending events.
		1253
		1254	Stopping the watcher, letting libev invoke it, or calling
		1255	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1256	not started in the first place.
		1257
		1258	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1259	functions that do not need a watcher.
1155		1260
1156	=back	1261	=back
1157		1262
1158		1263
1159	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1264	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1690		1795
1691	If the event loop is suspended for a long time, you can also force an	1796	If the event loop is suspended for a long time, you can also force an
1692	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1797	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1693	()>.	1798	()>.
1694		1799
		1800	=head3 The special problems of suspended animation
		1801
		1802	When you leave the server world it is quite customary to hit machines that
		1803	can suspend/hibernate - what happens to the clocks during such a suspend?
		1804
		1805	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1806	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1807	to run until the system is suspended, but they will not advance while the
		1808	system is suspended. That means, on resume, it will be as if the program
		1809	was frozen for a few seconds, but the suspend time will not be counted
		1810	towards C<ev_timer> when a monotonic clock source is used. The real time
		1811	clock advanced as expected, but if it is used as sole clocksource, then a
		1812	long suspend would be detected as a time jump by libev, and timers would
		1813	be adjusted accordingly.
		1814
		1815	I would not be surprised to see different behaviour in different between
		1816	operating systems, OS versions or even different hardware.
		1817
		1818	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1819	time jump in the monotonic clocks and the realtime clock. If the program
		1820	is suspended for a very long time, and monotonic clock sources are in use,
		1821	then you can expect C<ev_timer>s to expire as the full suspension time
		1822	will be counted towards the timers. When no monotonic clock source is in
		1823	use, then libev will again assume a timejump and adjust accordingly.
		1824
		1825	It might be beneficial for this latter case to call C<ev_suspend>
		1826	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1827	deterministic behaviour in this case (you can do nothing against
		1828	C<SIGSTOP>).
		1829
1695	=head3 Watcher-Specific Functions and Data Members	1830	=head3 Watcher-Specific Functions and Data Members
1696		1831
1697	=over 4	1832	=over 4
1698		1833
1699	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1834	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1724	If the timer is repeating, either start it if necessary (with the	1859	If the timer is repeating, either start it if necessary (with the
1725	C<repeat> value), or reset the running timer to the C<repeat> value.	1860	C<repeat> value), or reset the running timer to the C<repeat> value.
1726		1861
1727	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	1862	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1728	usage example.	1863	usage example.
		1864
		1865	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		1866
		1867	Returns the remaining time until a timer fires. If the timer is active,
		1868	then this time is relative to the current event loop time, otherwise it's
		1869	the timeout value currently configured.
		1870
		1871	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		1872	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
		1873	will return C<4>. When the timer expires and is restarted, it will return
		1874	roughly C<7> (likely slightly less as callback invocation takes some time,
		1875	too), and so on.
1729		1876
1730	=item ev_tstamp repeat [read-write]	1877	=item ev_tstamp repeat [read-write]
1731		1878
1732	The current C<repeat> value. Will be used each time the watcher times out	1879	The current C<repeat> value. Will be used each time the watcher times out
1733	or C<ev_timer_again> is called, and determines the next timeout (if any),	1880	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1969	Signal watchers will trigger an event when the process receives a specific	2116	Signal watchers will trigger an event when the process receives a specific
1970	signal one or more times. Even though signals are very asynchronous, libev	2117	signal one or more times. Even though signals are very asynchronous, libev
1971	will try it's best to deliver signals synchronously, i.e. as part of the	2118	will try it's best to deliver signals synchronously, i.e. as part of the
1972	normal event processing, like any other event.	2119	normal event processing, like any other event.
1973		2120
1974	If you want signals asynchronously, just use C<sigaction> as you would	2121	If you want signals to be delivered truly asynchronously, just use
1975	do without libev and forget about sharing the signal. You can even use	2122	C<sigaction> as you would do without libev and forget about sharing
1976	C<ev_async> from a signal handler to synchronously wake up an event loop.	2123	the signal. You can even use C<ev_async> from a signal handler to
		2124	synchronously wake up an event loop.
1977		2125
1978	You can configure as many watchers as you like per signal. Only when the	2126	You can configure as many watchers as you like for the same signal, but
		2127	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2128	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2129	C<SIGINT> in both the default loop and another loop at the same time. At
		2130	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2131
1979	first watcher gets started will libev actually register a signal handler	2132	When the first watcher gets started will libev actually register something
1980	with the kernel (thus it coexists with your own signal handlers as long as	2133	with the kernel (thus it coexists with your own signal handlers as long as
1981	you don't register any with libev for the same signal). Similarly, when	2134	you don't register any with libev for the same signal).
1982	the last signal watcher for a signal is stopped, libev will reset the
1983	signal handler to SIG_DFL (regardless of what it was set to before).
1984		2135
1985	If possible and supported, libev will install its handlers with	2136	If possible and supported, libev will install its handlers with
1986	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2137	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1987	interrupted. If you have a problem with system calls getting interrupted by	2138	not be unduly interrupted. If you have a problem with system calls getting
1988	signals you can block all signals in an C<ev_check> watcher and unblock	2139	interrupted by signals you can block all signals in an C<ev_check> watcher
1989	them in an C<ev_prepare> watcher.	2140	and unblock them in an C<ev_prepare> watcher.
		2141
		2142	=head3 The special problem of inheritance over fork/execve/pthread_create
		2143
		2144	Both the signal mask (C<sigprocmask>) and the signal disposition
		2145	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2146	stopping it again), that is, libev might or might not block the signal,
		2147	and might or might not set or restore the installed signal handler.
		2148
		2149	While this does not matter for the signal disposition (libev never
		2150	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2151	C<execve>), this matters for the signal mask: many programs do not expect
		2152	certain signals to be blocked.
		2153
		2154	This means that before calling C<exec> (from the child) you should reset
		2155	the signal mask to whatever "default" you expect (all clear is a good
		2156	choice usually).
		2157
		2158	The simplest way to ensure that the signal mask is reset in the child is
		2159	to install a fork handler with C<pthread_atfork> that resets it. That will
		2160	catch fork calls done by libraries (such as the libc) as well.
		2161
		2162	In current versions of libev, the signal will not be blocked indefinitely
		2163	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2164	the window of opportunity for problems, it will not go away, as libev
		2165	I<has> to modify the signal mask, at least temporarily.
		2166
		2167	So I can't stress this enough: I<If you do not reset your signal mask when
		2168	you expect it to be empty, you have a race condition in your code>. This
		2169	is not a libev-specific thing, this is true for most event libraries.
1990		2170
1991	=head3 Watcher-Specific Functions and Data Members	2171	=head3 Watcher-Specific Functions and Data Members
1992		2172
1993	=over 4	2173	=over 4
1994		2174
…		…
2039	libev)	2219	libev)
2040		2220
2041	=head3 Process Interaction	2221	=head3 Process Interaction
2042		2222
2043	Libev grabs C<SIGCHLD> as soon as the default event loop is	2223	Libev grabs C<SIGCHLD> as soon as the default event loop is
2044	initialised. This is necessary to guarantee proper behaviour even if	2224	initialised. This is necessary to guarantee proper behaviour even if the
2045	the first child watcher is started after the child exits. The occurrence	2225	first child watcher is started after the child exits. The occurrence
2046	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2226	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2047	synchronously as part of the event loop processing. Libev always reaps all	2227	synchronously as part of the event loop processing. Libev always reaps all
2048	children, even ones not watched.	2228	children, even ones not watched.
2049		2229
2050	=head3 Overriding the Built-In Processing	2230	=head3 Overriding the Built-In Processing
…		…
2060	=head3 Stopping the Child Watcher	2240	=head3 Stopping the Child Watcher
2061		2241
2062	Currently, the child watcher never gets stopped, even when the	2242	Currently, the child watcher never gets stopped, even when the
2063	child terminates, so normally one needs to stop the watcher in the	2243	child terminates, so normally one needs to stop the watcher in the
2064	callback. Future versions of libev might stop the watcher automatically	2244	callback. Future versions of libev might stop the watcher automatically
2065	when a child exit is detected.	2245	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2246	problem).
2066		2247
2067	=head3 Watcher-Specific Functions and Data Members	2248	=head3 Watcher-Specific Functions and Data Members
2068		2249
2069	=over 4	2250	=over 4
2070		2251
…		…
2810	=head3 Queueing	2991	=head3 Queueing
2811		2992
2812	C<ev_async> does not support queueing of data in any way. The reason	2993	C<ev_async> does not support queueing of data in any way. The reason
2813	is that the author does not know of a simple (or any) algorithm for a	2994	is that the author does not know of a simple (or any) algorithm for a
2814	multiple-writer-single-reader queue that works in all cases and doesn't	2995	multiple-writer-single-reader queue that works in all cases and doesn't
2815	need elaborate support such as pthreads.	2996	need elaborate support such as pthreads or unportable memory access
		2997	semantics.
2816		2998
2817	That means that if you want to queue data, you have to provide your own	2999	That means that if you want to queue data, you have to provide your own
2818	queue. But at least I can tell you how to implement locking around your	3000	queue. But at least I can tell you how to implement locking around your
2819	queue:	3001	queue:
2820		3002
…		…
2978	/* doh, nothing entered */;	3160	/* doh, nothing entered */;
2979	}	3161	}
2980		3162
2981	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3163	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2982		3164
2983	=item ev_feed_event (struct ev_loop , watcher , int revents)
2984
2985	Feeds the given event set into the event loop, as if the specified event
2986	had happened for the specified watcher (which must be a pointer to an
2987	initialised but not necessarily started event watcher).
2988
2989	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3165	=item ev_feed_fd_event (loop, int fd, int revents)
2990		3166
2991	Feed an event on the given fd, as if a file descriptor backend detected	3167	Feed an event on the given fd, as if a file descriptor backend detected
2992	the given events it.	3168	the given events it.
2993		3169
2994	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3170	=item ev_feed_signal_event (loop, int signum)
2995		3171
2996	Feed an event as if the given signal occurred (C<loop> must be the default	3172	Feed an event as if the given signal occurred (C<loop> must be the default
2997	loop!).	3173	loop!).
2998		3174
2999	=back	3175	=back
…		…
3079		3255
3080	=over 4	3256	=over 4
3081		3257
3082	=item ev::TYPE::TYPE ()	3258	=item ev::TYPE::TYPE ()
3083		3259
3084	=item ev::TYPE::TYPE (struct ev_loop *)	3260	=item ev::TYPE::TYPE (loop)
3085		3261
3086	=item ev::TYPE::~TYPE	3262	=item ev::TYPE::~TYPE
3087		3263
3088	The constructor (optionally) takes an event loop to associate the watcher	3264	The constructor (optionally) takes an event loop to associate the watcher
3089	with. If it is omitted, it will use C<EV_DEFAULT>.	3265	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3166	Example: Use a plain function as callback.	3342	Example: Use a plain function as callback.
3167		3343
3168	static void io_cb (ev::io &w, int revents) { }	3344	static void io_cb (ev::io &w, int revents) { }
3169	iow.set <io_cb> ();	3345	iow.set <io_cb> ();
3170		3346
3171	=item w->set (struct ev_loop *)	3347	=item w->set (loop)
3172		3348
3173	Associates a different C<struct ev_loop> with this watcher. You can only	3349	Associates a different C<struct ev_loop> with this watcher. You can only
3174	do this when the watcher is inactive (and not pending either).	3350	do this when the watcher is inactive (and not pending either).
3175		3351
3176	=item w->set ([arguments])	3352	=item w->set ([arguments])
…		…
3273	=item Ocaml	3449	=item Ocaml
3274		3450
3275	Erkki Seppala has written Ocaml bindings for libev, to be found at	3451	Erkki Seppala has written Ocaml bindings for libev, to be found at
3276	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3452	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3277		3453
		3454	=item Lua
		3455
		3456	Brian Maher has written a partial interface to libev for lua (at the
		3457	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3458	L<http://github.com/brimworks/lua-ev>.
		3459
3278	=back	3460	=back
3279		3461
3280		3462
3281	=head1 MACRO MAGIC	3463	=head1 MACRO MAGIC
3282		3464
…		…
3448	keeps libev from including F<config.h>, and it also defines dummy	3630	keeps libev from including F<config.h>, and it also defines dummy
3449	implementations for some libevent functions (such as logging, which is not	3631	implementations for some libevent functions (such as logging, which is not
3450	supported). It will also not define any of the structs usually found in	3632	supported). It will also not define any of the structs usually found in
3451	F<event.h> that are not directly supported by the libev core alone.	3633	F<event.h> that are not directly supported by the libev core alone.
3452		3634
3453	In stanbdalone mode, libev will still try to automatically deduce the	3635	In standalone mode, libev will still try to automatically deduce the
3454	configuration, but has to be more conservative.	3636	configuration, but has to be more conservative.
3455		3637
3456	=item EV_USE_MONOTONIC	3638	=item EV_USE_MONOTONIC
3457		3639
3458	If defined to be C<1>, libev will try to detect the availability of the	3640	If defined to be C<1>, libev will try to detect the availability of the
…		…
3523	be used is the winsock select). This means that it will call	3705	be used is the winsock select). This means that it will call
3524	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3706	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3525	it is assumed that all these functions actually work on fds, even	3707	it is assumed that all these functions actually work on fds, even
3526	on win32. Should not be defined on non-win32 platforms.	3708	on win32. Should not be defined on non-win32 platforms.
3527		3709
3528	=item EV_FD_TO_WIN32_HANDLE	3710	=item EV_FD_TO_WIN32_HANDLE(fd)
3529		3711
3530	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3712	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3531	file descriptors to socket handles. When not defining this symbol (the	3713	file descriptors to socket handles. When not defining this symbol (the
3532	default), then libev will call C<_get_osfhandle>, which is usually	3714	default), then libev will call C<_get_osfhandle>, which is usually
3533	correct. In some cases, programs use their own file descriptor management,	3715	correct. In some cases, programs use their own file descriptor management,
3534	in which case they can provide this function to map fds to socket handles.	3716	in which case they can provide this function to map fds to socket handles.
		3717
		3718	=item EV_WIN32_HANDLE_TO_FD(handle)
		3719
		3720	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3721	using the standard C<_open_osfhandle> function. For programs implementing
		3722	their own fd to handle mapping, overwriting this function makes it easier
		3723	to do so. This can be done by defining this macro to an appropriate value.
		3724
		3725	=item EV_WIN32_CLOSE_FD(fd)
		3726
		3727	If programs implement their own fd to handle mapping on win32, then this
		3728	macro can be used to override the C<close> function, useful to unregister
		3729	file descriptors again. Note that the replacement function has to close
		3730	the underlying OS handle.
3535		3731
3536	=item EV_USE_POLL	3732	=item EV_USE_POLL
3537		3733
3538	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3734	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3539	backend. Otherwise it will be enabled on non-win32 platforms. It	3735	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3671	defined to be C<0>, then they are not.	3867	defined to be C<0>, then they are not.
3672		3868
3673	=item EV_MINIMAL	3869	=item EV_MINIMAL
3674		3870
3675	If you need to shave off some kilobytes of code at the expense of some	3871	If you need to shave off some kilobytes of code at the expense of some
3676	speed, define this symbol to C<1>. Currently this is used to override some	3872	speed (but with the full API), define this symbol to C<1>. Currently this
3677	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3873	is used to override some inlining decisions, saves roughly 30% code size
3678	much smaller 2-heap for timer management over the default 4-heap.	3874	on amd64. It also selects a much smaller 2-heap for timer management over
		3875	the default 4-heap.
		3876
		3877	You can save even more by disabling watcher types you do not need
		3878	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3879	(C<-DNDEBUG>) will usually reduce code size a lot.
		3880
		3881	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3882	provide a bare-bones event library. See C<ev.h> for details on what parts
		3883	of the API are still available, and do not complain if this subset changes
		3884	over time.
		3885
		3886	=item EV_NSIG
		3887
		3888	The highest supported signal number, +1 (or, the number of
		3889	signals): Normally, libev tries to deduce the maximum number of signals
		3890	automatically, but sometimes this fails, in which case it can be
		3891	specified. Also, using a lower number than detected (C<32> should be
		3892	good for about any system in existance) can save some memory, as libev
		3893	statically allocates some 12-24 bytes per signal number.
3679		3894
3680	=item EV_PID_HASHSIZE	3895	=item EV_PID_HASHSIZE
3681		3896
3682	C<ev_child> watchers use a small hash table to distribute workload by	3897	C<ev_child> watchers use a small hash table to distribute workload by
3683	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3898	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3869	default loop and triggering an C<ev_async> watcher from the default loop	4084	default loop and triggering an C<ev_async> watcher from the default loop
3870	watcher callback into the event loop interested in the signal.	4085	watcher callback into the event loop interested in the signal.
3871		4086
3872	=back	4087	=back
3873		4088
		4089	=head4 THREAD LOCKING EXAMPLE
		4090
		4091	Here is a fictitious example of how to run an event loop in a different
		4092	thread than where callbacks are being invoked and watchers are
		4093	created/added/removed.
		4094
		4095	For a real-world example, see the C<EV::Loop::Async> perl module,
		4096	which uses exactly this technique (which is suited for many high-level
		4097	languages).
		4098
		4099	The example uses a pthread mutex to protect the loop data, a condition
		4100	variable to wait for callback invocations, an async watcher to notify the
		4101	event loop thread and an unspecified mechanism to wake up the main thread.
		4102
		4103	First, you need to associate some data with the event loop:
		4104
		4105	typedef struct {
		4106	mutex_t lock; /* global loop lock */
		4107	ev_async async_w;
		4108	thread_t tid;
		4109	cond_t invoke_cv;
		4110	} userdata;
		4111
		4112	void prepare_loop (EV_P)
		4113	{
		4114	// for simplicity, we use a static userdata struct.
		4115	static userdata u;
		4116
		4117	ev_async_init (&u->async_w, async_cb);
		4118	ev_async_start (EV_A_ &u->async_w);
		4119
		4120	pthread_mutex_init (&u->lock, 0);
		4121	pthread_cond_init (&u->invoke_cv, 0);
		4122
		4123	// now associate this with the loop
		4124	ev_set_userdata (EV_A_ u);
		4125	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4126	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4127
		4128	// then create the thread running ev_loop
		4129	pthread_create (&u->tid, 0, l_run, EV_A);
		4130	}
		4131
		4132	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4133	solely to wake up the event loop so it takes notice of any new watchers
		4134	that might have been added:
		4135
		4136	static void
		4137	async_cb (EV_P_ ev_async *w, int revents)
		4138	{
		4139	// just used for the side effects
		4140	}
		4141
		4142	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4143	protecting the loop data, respectively.
		4144
		4145	static void
		4146	l_release (EV_P)
		4147	{
		4148	userdata *u = ev_userdata (EV_A);
		4149	pthread_mutex_unlock (&u->lock);
		4150	}
		4151
		4152	static void
		4153	l_acquire (EV_P)
		4154	{
		4155	userdata *u = ev_userdata (EV_A);
		4156	pthread_mutex_lock (&u->lock);
		4157	}
		4158
		4159	The event loop thread first acquires the mutex, and then jumps straight
		4160	into C<ev_loop>:
		4161
		4162	void *
		4163	l_run (void *thr_arg)
		4164	{
		4165	struct ev_loop loop = (struct ev_loop )thr_arg;
		4166
		4167	l_acquire (EV_A);
		4168	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4169	ev_loop (EV_A_ 0);
		4170	l_release (EV_A);
		4171
		4172	return 0;
		4173	}
		4174
		4175	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4176	signal the main thread via some unspecified mechanism (signals? pipe
		4177	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4178	have been called (in a while loop because a) spurious wakeups are possible
		4179	and b) skipping inter-thread-communication when there are no pending
		4180	watchers is very beneficial):
		4181
		4182	static void
		4183	l_invoke (EV_P)
		4184	{
		4185	userdata *u = ev_userdata (EV_A);
		4186
		4187	while (ev_pending_count (EV_A))
		4188	{
		4189	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4190	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4191	}
		4192	}
		4193
		4194	Now, whenever the main thread gets told to invoke pending watchers, it
		4195	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4196	thread to continue:
		4197
		4198	static void
		4199	real_invoke_pending (EV_P)
		4200	{
		4201	userdata *u = ev_userdata (EV_A);
		4202
		4203	pthread_mutex_lock (&u->lock);
		4204	ev_invoke_pending (EV_A);
		4205	pthread_cond_signal (&u->invoke_cv);
		4206	pthread_mutex_unlock (&u->lock);
		4207	}
		4208
		4209	Whenever you want to start/stop a watcher or do other modifications to an
		4210	event loop, you will now have to lock:
		4211
		4212	ev_timer timeout_watcher;
		4213	userdata *u = ev_userdata (EV_A);
		4214
		4215	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4216
		4217	pthread_mutex_lock (&u->lock);
		4218	ev_timer_start (EV_A_ &timeout_watcher);
		4219	ev_async_send (EV_A_ &u->async_w);
		4220	pthread_mutex_unlock (&u->lock);
		4221
		4222	Note that sending the C<ev_async> watcher is required because otherwise
		4223	an event loop currently blocking in the kernel will have no knowledge
		4224	about the newly added timer. By waking up the loop it will pick up any new
		4225	watchers in the next event loop iteration.
		4226
3874	=head3 COROUTINES	4227	=head3 COROUTINES
3875		4228
3876	Libev is very accommodating to coroutines ("cooperative threads"):	4229	Libev is very accommodating to coroutines ("cooperative threads"):
3877	libev fully supports nesting calls to its functions from different	4230	libev fully supports nesting calls to its functions from different
3878	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4231	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3879	different coroutines, and switch freely between both coroutines running the	4232	different coroutines, and switch freely between both coroutines running
3880	loop, as long as you don't confuse yourself). The only exception is that	4233	the loop, as long as you don't confuse yourself). The only exception is
3881	you must not do this from C<ev_periodic> reschedule callbacks.	4234	that you must not do this from C<ev_periodic> reschedule callbacks.
3882		4235
3883	Care has been taken to ensure that libev does not keep local state inside	4236	Care has been taken to ensure that libev does not keep local state inside
3884	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4237	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3885	they do not call any callbacks.	4238	they do not call any callbacks.
3886		4239

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Comparing libev/ev.pod (file contents): Revision 1.249 by root, Wed Jul 8 04:29:31 2009 UTC vs. Revision 1.279 by root, Mon Feb 15 05:15:55 2010 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.249 by root, Wed Jul 8 04:29:31 2009 UTC vs.
Revision 1.279 by root, Mon Feb 15 05:15:55 2010 UTC