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

Comparing libev/ev.pod (file contents):
Revision 1.248 by root, Wed Jul 8 04:14:34 2009 UTC vs.
Revision 1.277 by root, Thu Dec 31 06:50:17 2009 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 is both faster and might make
		380	it possible to get the queued signal data.
		381
		382	Signalfd will not be used by default as this changes your signal mask, and
		383	there are a lot of shoddy libraries and programs (glib's threadpool for
		384	example) that can't properly initialise their signal masks.
		385
367	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	386	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
368		387
369	This is your standard select(2) backend. Not I<completely> standard, as	388	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,	389	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	390	but if that fails, expect a fairly low limit on the number of fds when
…		…
394		413
395	This backend maps C<EV_READ> to C<POLLIN \| POLLERR \| POLLHUP>, and	414	This backend maps C<EV_READ> to C<POLLIN \| POLLERR \| POLLHUP>, and
396	C<EV_WRITE> to C<POLLOUT \| POLLERR \| POLLHUP>.	415	C<EV_WRITE> to C<POLLOUT \| POLLERR \| POLLHUP>.
397		416
398	=item C<EVBACKEND_EPOLL> (value 4, Linux)	417	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		418
		419	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		420	kernels).
399		421
400	For few fds, this backend is a bit little slower than poll and select,	422	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	423	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),	424	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).	425	epoll scales either O(1) or O(active_fds).
…		…
518		540
519	It is definitely not recommended to use this flag.	541	It is definitely not recommended to use this flag.
520		542
521	=back	543	=back
522		544
523	If one or more of these are or'ed into the flags value, then only these	545	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	546	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.	547	here). If none are specified, all backends in C<ev_recommended_backends
		548	()> will be tried.
526		549
527	Example: This is the most typical usage.	550	Example: This is the most typical usage.
528		551
529	if (!ev_default_loop (0))	552	if (!ev_default_loop (0))
530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	553	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
573	as signal and child watchers) would need to be stopped manually.	596	as signal and child watchers) would need to be stopped manually.
574		597
575	In general it is not advisable to call this function except in the	598	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	599	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	600	pipe fds. If you need dynamically allocated loops it is better to use
578	C<ev_loop_new> and C<ev_loop_destroy>).	601	C<ev_loop_new> and C<ev_loop_destroy>.
579		602
580	=item ev_loop_destroy (loop)	603	=item ev_loop_destroy (loop)
581		604
582	Like C<ev_default_destroy>, but destroys an event loop created by an	605	Like C<ev_default_destroy>, but destroys an event loop created by an
583	earlier call to C<ev_loop_new>.	606	earlier call to C<ev_loop_new>.
…		…
687	event loop time (see C<ev_now_update>).	710	event loop time (see C<ev_now_update>).
688		711
689	=item ev_loop (loop, int flags)	712	=item ev_loop (loop, int flags)
690		713
691	Finally, this is it, the event handler. This function usually is called	714	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	715	after you have initialised all your watchers and you want to start
693	events.	716	handling events.
694		717
695	If the flags argument is specified as C<0>, it will not return until	718	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.	719	either no event watchers are active anymore or C<ev_unloop> was called.
697		720
698	Please note that an explicit C<ev_unloop> is usually better than	721	Please note that an explicit C<ev_unloop> is usually better than
…		…
772		795
773	Ref/unref can be used to add or remove a reference count on the event	796	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	797	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.	798	count is nonzero, C<ev_loop> will not return on its own.
776		799
777	If you have a watcher you never unregister that should not keep C<ev_loop>	800	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	801	unregister, but that nevertheless should not keep C<ev_loop> from
		802	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
779	stopping it.	803	before stopping it.
780		804
781	As an example, libev itself uses this for its internal signal pipe: It	805	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	806	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	807	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	808	excellent way to do this for generic recurring timers or from within
…		…
856	more often than 100 times per second:	880	more often than 100 times per second:
857		881
858	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);	882	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	883	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
860		884
		885	=item ev_invoke_pending (loop)
		886
		887	This call will simply invoke all pending watchers while resetting their
		888	pending state. Normally, C<ev_loop> does this automatically when required,
		889	but when overriding the invoke callback this call comes handy.
		890
		891	=item int ev_pending_count (loop)
		892
		893	Returns the number of pending watchers - zero indicates that no watchers
		894	are pending.
		895
		896	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		897
		898	This overrides the invoke pending functionality of the loop: Instead of
		899	invoking all pending watchers when there are any, C<ev_loop> will call
		900	this callback instead. This is useful, for example, when you want to
		901	invoke the actual watchers inside another context (another thread etc.).
		902
		903	If you want to reset the callback, use C<ev_invoke_pending> as new
		904	callback.
		905
		906	=item ev_set_loop_release_cb (loop, void (release)(EV_P), void (acquire)(EV_P))
		907
		908	Sometimes you want to share the same loop between multiple threads. This
		909	can be done relatively simply by putting mutex_lock/unlock calls around
		910	each call to a libev function.
		911
		912	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		913	wait for it to return. One way around this is to wake up the loop via
		914	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		915	and I<acquire> callbacks on the loop.
		916
		917	When set, then C<release> will be called just before the thread is
		918	suspended waiting for new events, and C<acquire> is called just
		919	afterwards.
		920
		921	Ideally, C<release> will just call your mutex_unlock function, and
		922	C<acquire> will just call the mutex_lock function again.
		923
		924	While event loop modifications are allowed between invocations of
		925	C<release> and C<acquire> (that's their only purpose after all), no
		926	modifications done will affect the event loop, i.e. adding watchers will
		927	have no effect on the set of file descriptors being watched, or the time
		928	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		929	to take note of any changes you made.
		930
		931	In theory, threads executing C<ev_loop> will be async-cancel safe between
		932	invocations of C<release> and C<acquire>.
		933
		934	See also the locking example in the C<THREADS> section later in this
		935	document.
		936
		937	=item ev_set_userdata (loop, void *data)
		938
		939	=item ev_userdata (loop)
		940
		941	Set and retrieve a single C<void *> associated with a loop. When
		942	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		943	C<0.>
		944
		945	These two functions can be used to associate arbitrary data with a loop,
		946	and are intended solely for the C<invoke_pending_cb>, C<release> and
		947	C<acquire> callbacks described above, but of course can be (ab-)used for
		948	any other purpose as well.
		949
861	=item ev_loop_verify (loop)	950	=item ev_loop_verify (loop)
862		951
863	This function only does something when C<EV_VERIFY> support has been	952	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	953	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	954	through all internal structures and checks them for validity. If anything
…		…
1041		1130
1042	ev_io w;	1131	ev_io w;
1043	ev_init (&w, my_cb);	1132	ev_init (&w, my_cb);
1044	ev_io_set (&w, STDIN_FILENO, EV_READ);	1133	ev_io_set (&w, STDIN_FILENO, EV_READ);
1045		1134
1046	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1135	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1047		1136
1048	This macro initialises the type-specific parts of a watcher. You need to	1137	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	1138	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	1139	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	1140	macro on a watcher that is active (it can be pending, however, which is a
…		…
1064		1153
1065	Example: Initialise and set an C<ev_io> watcher in one step.	1154	Example: Initialise and set an C<ev_io> watcher in one step.
1066		1155
1067	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1156	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1068		1157
1069	=item C<ev_TYPE_start> (loop , ev_TYPE watcher)	1158	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1070		1159
1071	Starts (activates) the given watcher. Only active watchers will receive	1160	Starts (activates) the given watcher. Only active watchers will receive
1072	events. If the watcher is already active nothing will happen.	1161	events. If the watcher is already active nothing will happen.
1073		1162
1074	Example: Start the C<ev_io> watcher that is being abused as example in this	1163	Example: Start the C<ev_io> watcher that is being abused as example in this
1075	whole section.	1164	whole section.
1076		1165
1077	ev_io_start (EV_DEFAULT_UC, &w);	1166	ev_io_start (EV_DEFAULT_UC, &w);
1078		1167
1079	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)	1168	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1080		1169
1081	Stops the given watcher if active, and clears the pending status (whether	1170	Stops the given watcher if active, and clears the pending status (whether
1082	the watcher was active or not).	1171	the watcher was active or not).
1083		1172
1084	It is possible that stopped watchers are pending - for example,	1173	It is possible that stopped watchers are pending - for example,
…		…
1109	=item ev_cb_set (ev_TYPE *watcher, callback)	1198	=item ev_cb_set (ev_TYPE *watcher, callback)
1110		1199
1111	Change the callback. You can change the callback at virtually any time	1200	Change the callback. You can change the callback at virtually any time
1112	(modulo threads).	1201	(modulo threads).
1113		1202
1114	=item ev_set_priority (ev_TYPE *watcher, priority)	1203	=item ev_set_priority (ev_TYPE *watcher, int priority)
1115		1204
1116	=item int ev_priority (ev_TYPE *watcher)	1205	=item int ev_priority (ev_TYPE *watcher)
1117		1206
1118	Set and query the priority of the watcher. The priority is a small	1207	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>	1208	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	1239	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>.	1240	watcher isn't pending it does nothing and returns C<0>.
1152		1241
1153	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1242	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.	1243	callback to be invoked, which can be accomplished with this function.
		1244
		1245	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1246
		1247	Feeds the given event set into the event loop, as if the specified event
		1248	had happened for the specified watcher (which must be a pointer to an
		1249	initialised but not necessarily started event watcher). Obviously you must
		1250	not free the watcher as long as it has pending events.
		1251
		1252	Stopping the watcher, letting libev invoke it, or calling
		1253	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1254	not started in the first place.
		1255
		1256	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1257	functions that do not need a watcher.
1155		1258
1156	=back	1259	=back
1157		1260
1158		1261
1159	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1262	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1690		1793
1691	If the event loop is suspended for a long time, you can also force an	1794	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	1795	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1693	()>.	1796	()>.
1694		1797
		1798	=head3 The special problems of suspended animation
		1799
		1800	When you leave the server world it is quite customary to hit machines that
		1801	can suspend/hibernate - what happens to the clocks during such a suspend?
		1802
		1803	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1804	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1805	to run until the system is suspended, but they will not advance while the
		1806	system is suspended. That means, on resume, it will be as if the program
		1807	was frozen for a few seconds, but the suspend time will not be counted
		1808	towards C<ev_timer> when a monotonic clock source is used. The real time
		1809	clock advanced as expected, but if it is used as sole clocksource, then a
		1810	long suspend would be detected as a time jump by libev, and timers would
		1811	be adjusted accordingly.
		1812
		1813	I would not be surprised to see different behaviour in different between
		1814	operating systems, OS versions or even different hardware.
		1815
		1816	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1817	time jump in the monotonic clocks and the realtime clock. If the program
		1818	is suspended for a very long time, and monotonic clock sources are in use,
		1819	then you can expect C<ev_timer>s to expire as the full suspension time
		1820	will be counted towards the timers. When no monotonic clock source is in
		1821	use, then libev will again assume a timejump and adjust accordingly.
		1822
		1823	It might be beneficial for this latter case to call C<ev_suspend>
		1824	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1825	deterministic behaviour in this case (you can do nothing against
		1826	C<SIGSTOP>).
		1827
1695	=head3 Watcher-Specific Functions and Data Members	1828	=head3 Watcher-Specific Functions and Data Members
1696		1829
1697	=over 4	1830	=over 4
1698		1831
1699	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1832	=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	1857	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.	1858	C<repeat> value), or reset the running timer to the C<repeat> value.
1726		1859
1727	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	1860	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1728	usage example.	1861	usage example.
		1862
		1863	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		1864
		1865	Returns the remaining time until a timer fires. If the timer is active,
		1866	then this time is relative to the current event loop time, otherwise it's
		1867	the timeout value currently configured.
		1868
		1869	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		1870	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
		1871	will return C<4>. When the timer expires and is restarted, it will return
		1872	roughly C<7> (likely slightly less as callback invocation takes some time,
		1873	too), and so on.
1729		1874
1730	=item ev_tstamp repeat [read-write]	1875	=item ev_tstamp repeat [read-write]
1731		1876
1732	The current C<repeat> value. Will be used each time the watcher times out	1877	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),	1878	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	2114	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	2115	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	2116	will try it's best to deliver signals synchronously, i.e. as part of the
1972	normal event processing, like any other event.	2117	normal event processing, like any other event.
1973		2118
1974	If you want signals asynchronously, just use C<sigaction> as you would	2119	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	2120	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.	2121	the signal. You can even use C<ev_async> from a signal handler to
		2122	synchronously wake up an event loop.
1977		2123
1978	You can configure as many watchers as you like per signal. Only when the	2124	You can configure as many watchers as you like for the same signal, but
		2125	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2126	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2127	C<SIGINT> in both the default loop and another loop at the same time. At
		2128	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2129
1979	first watcher gets started will libev actually register a signal handler	2130	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	2131	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	2132	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		2133
1985	If possible and supported, libev will install its handlers with	2134	If possible and supported, libev will install its handlers with
1986	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2135	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1987	interrupted. If you have a problem with system calls getting interrupted by	2136	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	2137	interrupted by signals you can block all signals in an C<ev_check> watcher
1989	them in an C<ev_prepare> watcher.	2138	and unblock them in an C<ev_prepare> watcher.
		2139
		2140	=head3 The special problem of inheritance over fork/execve/pthread_create
		2141
		2142	Both the signal mask (C<sigprocmask>) and the signal disposition
		2143	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2144	stopping it again), that is, libev might or might not block the signal,
		2145	and might or might not set or restore the installed signal handler.
		2146
		2147	While this does not matter for the signal disposition (libev never
		2148	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2149	C<execve>), this matters for the signal mask: many programs do not expect
		2150	certain signals to be blocked.
		2151
		2152	This means that before calling C<exec> (from the child) you should reset
		2153	the signal mask to whatever "default" you expect (all clear is a good
		2154	choice usually).
		2155
		2156	The simplest way to ensure that the signal mask is reset in the child is
		2157	to install a fork handler with C<pthread_atfork> that resets it. That will
		2158	catch fork calls done by libraries (such as the libc) as well.
		2159
		2160	In current versions of libev, the signal will not be blocked indefinitely
		2161	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2162	the window of opportunity for problems, it will not go away, as libev
		2163	I<has> to modify the signal mask, at least temporarily.
		2164
		2165	So I can't stress this enough I<if you do not reset your signal mask
		2166	when you expect it to be empty, you have a race condition in your
		2167	program>. This is not a libev-specific thing, this is true for most event
		2168	libraries.
1990		2169
1991	=head3 Watcher-Specific Functions and Data Members	2170	=head3 Watcher-Specific Functions and Data Members
1992		2171
1993	=over 4	2172	=over 4
1994		2173
…		…
2033		2212
2034	Only the default event loop is capable of handling signals, and therefore	2213	Only the default event loop is capable of handling signals, and therefore
2035	you can only register child watchers in the default event loop.	2214	you can only register child watchers in the default event loop.
2036		2215
2037	Due to some design glitches inside libev, child watchers will always be	2216	Due to some design glitches inside libev, child watchers will always be
2038	handled at maximum priority (their priority is set to EV_MAXPRI by libev)	2217	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2218	libev)
2039		2219
2040	=head3 Process Interaction	2220	=head3 Process Interaction
2041		2221
2042	Libev grabs C<SIGCHLD> as soon as the default event loop is	2222	Libev grabs C<SIGCHLD> as soon as the default event loop is
2043	initialised. This is necessary to guarantee proper behaviour even if	2223	initialised. This is necessary to guarantee proper behaviour even if the
2044	the first child watcher is started after the child exits. The occurrence	2224	first child watcher is started after the child exits. The occurrence
2045	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2225	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2046	synchronously as part of the event loop processing. Libev always reaps all	2226	synchronously as part of the event loop processing. Libev always reaps all
2047	children, even ones not watched.	2227	children, even ones not watched.
2048		2228
2049	=head3 Overriding the Built-In Processing	2229	=head3 Overriding the Built-In Processing
…		…
2059	=head3 Stopping the Child Watcher	2239	=head3 Stopping the Child Watcher
2060		2240
2061	Currently, the child watcher never gets stopped, even when the	2241	Currently, the child watcher never gets stopped, even when the
2062	child terminates, so normally one needs to stop the watcher in the	2242	child terminates, so normally one needs to stop the watcher in the
2063	callback. Future versions of libev might stop the watcher automatically	2243	callback. Future versions of libev might stop the watcher automatically
2064	when a child exit is detected.	2244	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2245	problem).
2065		2246
2066	=head3 Watcher-Specific Functions and Data Members	2247	=head3 Watcher-Specific Functions and Data Members
2067		2248
2068	=over 4	2249	=over 4
2069		2250
…		…
2809	=head3 Queueing	2990	=head3 Queueing
2810		2991
2811	C<ev_async> does not support queueing of data in any way. The reason	2992	C<ev_async> does not support queueing of data in any way. The reason
2812	is that the author does not know of a simple (or any) algorithm for a	2993	is that the author does not know of a simple (or any) algorithm for a
2813	multiple-writer-single-reader queue that works in all cases and doesn't	2994	multiple-writer-single-reader queue that works in all cases and doesn't
2814	need elaborate support such as pthreads.	2995	need elaborate support such as pthreads or unportable memory access
		2996	semantics.
2815		2997
2816	That means that if you want to queue data, you have to provide your own	2998	That means that if you want to queue data, you have to provide your own
2817	queue. But at least I can tell you how to implement locking around your	2999	queue. But at least I can tell you how to implement locking around your
2818	queue:	3000	queue:
2819		3001
…		…
2977	/* doh, nothing entered */;	3159	/* doh, nothing entered */;
2978	}	3160	}
2979		3161
2980	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3162	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2981		3163
2982	=item ev_feed_event (struct ev_loop , watcher , int revents)
2983
2984	Feeds the given event set into the event loop, as if the specified event
2985	had happened for the specified watcher (which must be a pointer to an
2986	initialised but not necessarily started event watcher).
2987
2988	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3164	=item ev_feed_fd_event (loop, int fd, int revents)
2989		3165
2990	Feed an event on the given fd, as if a file descriptor backend detected	3166	Feed an event on the given fd, as if a file descriptor backend detected
2991	the given events it.	3167	the given events it.
2992		3168
2993	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3169	=item ev_feed_signal_event (loop, int signum)
2994		3170
2995	Feed an event as if the given signal occurred (C<loop> must be the default	3171	Feed an event as if the given signal occurred (C<loop> must be the default
2996	loop!).	3172	loop!).
2997		3173
2998	=back	3174	=back
…		…
3078		3254
3079	=over 4	3255	=over 4
3080		3256
3081	=item ev::TYPE::TYPE ()	3257	=item ev::TYPE::TYPE ()
3082		3258
3083	=item ev::TYPE::TYPE (struct ev_loop *)	3259	=item ev::TYPE::TYPE (loop)
3084		3260
3085	=item ev::TYPE::~TYPE	3261	=item ev::TYPE::~TYPE
3086		3262
3087	The constructor (optionally) takes an event loop to associate the watcher	3263	The constructor (optionally) takes an event loop to associate the watcher
3088	with. If it is omitted, it will use C<EV_DEFAULT>.	3264	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3165	Example: Use a plain function as callback.	3341	Example: Use a plain function as callback.
3166		3342
3167	static void io_cb (ev::io &w, int revents) { }	3343	static void io_cb (ev::io &w, int revents) { }
3168	iow.set <io_cb> ();	3344	iow.set <io_cb> ();
3169		3345
3170	=item w->set (struct ev_loop *)	3346	=item w->set (loop)
3171		3347
3172	Associates a different C<struct ev_loop> with this watcher. You can only	3348	Associates a different C<struct ev_loop> with this watcher. You can only
3173	do this when the watcher is inactive (and not pending either).	3349	do this when the watcher is inactive (and not pending either).
3174		3350
3175	=item w->set ([arguments])	3351	=item w->set ([arguments])
…		…
3272	=item Ocaml	3448	=item Ocaml
3273		3449
3274	Erkki Seppala has written Ocaml bindings for libev, to be found at	3450	Erkki Seppala has written Ocaml bindings for libev, to be found at
3275	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3451	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3276		3452
		3453	=item Lua
		3454
		3455	Brian Maher has written a partial interface to libev
		3456	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3457	L<http://github.com/brimworks/lua-ev>.
		3458
3277	=back	3459	=back
3278		3460
3279		3461
3280	=head1 MACRO MAGIC	3462	=head1 MACRO MAGIC
3281		3463
…		…
3447	keeps libev from including F<config.h>, and it also defines dummy	3629	keeps libev from including F<config.h>, and it also defines dummy
3448	implementations for some libevent functions (such as logging, which is not	3630	implementations for some libevent functions (such as logging, which is not
3449	supported). It will also not define any of the structs usually found in	3631	supported). It will also not define any of the structs usually found in
3450	F<event.h> that are not directly supported by the libev core alone.	3632	F<event.h> that are not directly supported by the libev core alone.
3451		3633
3452	In stanbdalone mode, libev will still try to automatically deduce the	3634	In standalone mode, libev will still try to automatically deduce the
3453	configuration, but has to be more conservative.	3635	configuration, but has to be more conservative.
3454		3636
3455	=item EV_USE_MONOTONIC	3637	=item EV_USE_MONOTONIC
3456		3638
3457	If defined to be C<1>, libev will try to detect the availability of the	3639	If defined to be C<1>, libev will try to detect the availability of the
…		…
3522	be used is the winsock select). This means that it will call	3704	be used is the winsock select). This means that it will call
3523	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3705	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3524	it is assumed that all these functions actually work on fds, even	3706	it is assumed that all these functions actually work on fds, even
3525	on win32. Should not be defined on non-win32 platforms.	3707	on win32. Should not be defined on non-win32 platforms.
3526		3708
3527	=item EV_FD_TO_WIN32_HANDLE	3709	=item EV_FD_TO_WIN32_HANDLE(fd)
3528		3710
3529	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3711	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3530	file descriptors to socket handles. When not defining this symbol (the	3712	file descriptors to socket handles. When not defining this symbol (the
3531	default), then libev will call C<_get_osfhandle>, which is usually	3713	default), then libev will call C<_get_osfhandle>, which is usually
3532	correct. In some cases, programs use their own file descriptor management,	3714	correct. In some cases, programs use their own file descriptor management,
3533	in which case they can provide this function to map fds to socket handles.	3715	in which case they can provide this function to map fds to socket handles.
		3716
		3717	=item EV_WIN32_HANDLE_TO_FD(handle)
		3718
		3719	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3720	using the standard C<_open_osfhandle> function. For programs implementing
		3721	their own fd to handle mapping, overwriting this function makes it easier
		3722	to do so. This can be done by defining this macro to an appropriate value.
		3723
		3724	=item EV_WIN32_CLOSE_FD(fd)
		3725
		3726	If programs implement their own fd to handle mapping on win32, then this
		3727	macro can be used to override the C<close> function, useful to unregister
		3728	file descriptors again. Note that the replacement function has to close
		3729	the underlying OS handle.
3534		3730
3535	=item EV_USE_POLL	3731	=item EV_USE_POLL
3536		3732
3537	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3733	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3538	backend. Otherwise it will be enabled on non-win32 platforms. It	3734	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3670	defined to be C<0>, then they are not.	3866	defined to be C<0>, then they are not.
3671		3867
3672	=item EV_MINIMAL	3868	=item EV_MINIMAL
3673		3869
3674	If you need to shave off some kilobytes of code at the expense of some	3870	If you need to shave off some kilobytes of code at the expense of some
3675	speed, define this symbol to C<1>. Currently this is used to override some	3871	speed (but with the full API), define this symbol to C<1>. Currently this
3676	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3872	is used to override some inlining decisions, saves roughly 30% code size
3677	much smaller 2-heap for timer management over the default 4-heap.	3873	on amd64. It also selects a much smaller 2-heap for timer management over
		3874	the default 4-heap.
		3875
		3876	You can save even more by disabling watcher types you do not need
		3877	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3878	(C<-DNDEBUG>) will usually reduce code size a lot.
		3879
		3880	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3881	provide a bare-bones event library. See C<ev.h> for details on what parts
		3882	of the API are still available, and do not complain if this subset changes
		3883	over time.
		3884
		3885	=item EV_NSIG
		3886
		3887	The highest supported signal number, +1 (or, the number of
		3888	signals): Normally, libev tries to deduce the maximum number of signals
		3889	automatically, but sometimes this fails, in which case it can be
		3890	specified. Also, using a lower number than detected (C<32> should be
		3891	good for about any system in existance) can save some memory, as libev
		3892	statically allocates some 12-24 bytes per signal number.
3678		3893
3679	=item EV_PID_HASHSIZE	3894	=item EV_PID_HASHSIZE
3680		3895
3681	C<ev_child> watchers use a small hash table to distribute workload by	3896	C<ev_child> watchers use a small hash table to distribute workload by
3682	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3897	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3868	default loop and triggering an C<ev_async> watcher from the default loop	4083	default loop and triggering an C<ev_async> watcher from the default loop
3869	watcher callback into the event loop interested in the signal.	4084	watcher callback into the event loop interested in the signal.
3870		4085
3871	=back	4086	=back
3872		4087
		4088	=head4 THREAD LOCKING EXAMPLE
		4089
		4090	Here is a fictitious example of how to run an event loop in a different
		4091	thread than where callbacks are being invoked and watchers are
		4092	created/added/removed.
		4093
		4094	For a real-world example, see the C<EV::Loop::Async> perl module,
		4095	which uses exactly this technique (which is suited for many high-level
		4096	languages).
		4097
		4098	The example uses a pthread mutex to protect the loop data, a condition
		4099	variable to wait for callback invocations, an async watcher to notify the
		4100	event loop thread and an unspecified mechanism to wake up the main thread.
		4101
		4102	First, you need to associate some data with the event loop:
		4103
		4104	typedef struct {
		4105	mutex_t lock; /* global loop lock */
		4106	ev_async async_w;
		4107	thread_t tid;
		4108	cond_t invoke_cv;
		4109	} userdata;
		4110
		4111	void prepare_loop (EV_P)
		4112	{
		4113	// for simplicity, we use a static userdata struct.
		4114	static userdata u;
		4115
		4116	ev_async_init (&u->async_w, async_cb);
		4117	ev_async_start (EV_A_ &u->async_w);
		4118
		4119	pthread_mutex_init (&u->lock, 0);
		4120	pthread_cond_init (&u->invoke_cv, 0);
		4121
		4122	// now associate this with the loop
		4123	ev_set_userdata (EV_A_ u);
		4124	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4125	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4126
		4127	// then create the thread running ev_loop
		4128	pthread_create (&u->tid, 0, l_run, EV_A);
		4129	}
		4130
		4131	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4132	solely to wake up the event loop so it takes notice of any new watchers
		4133	that might have been added:
		4134
		4135	static void
		4136	async_cb (EV_P_ ev_async *w, int revents)
		4137	{
		4138	// just used for the side effects
		4139	}
		4140
		4141	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4142	protecting the loop data, respectively.
		4143
		4144	static void
		4145	l_release (EV_P)
		4146	{
		4147	userdata *u = ev_userdata (EV_A);
		4148	pthread_mutex_unlock (&u->lock);
		4149	}
		4150
		4151	static void
		4152	l_acquire (EV_P)
		4153	{
		4154	userdata *u = ev_userdata (EV_A);
		4155	pthread_mutex_lock (&u->lock);
		4156	}
		4157
		4158	The event loop thread first acquires the mutex, and then jumps straight
		4159	into C<ev_loop>:
		4160
		4161	void *
		4162	l_run (void *thr_arg)
		4163	{
		4164	struct ev_loop loop = (struct ev_loop )thr_arg;
		4165
		4166	l_acquire (EV_A);
		4167	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4168	ev_loop (EV_A_ 0);
		4169	l_release (EV_A);
		4170
		4171	return 0;
		4172	}
		4173
		4174	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4175	signal the main thread via some unspecified mechanism (signals? pipe
		4176	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4177	have been called (in a while loop because a) spurious wakeups are possible
		4178	and b) skipping inter-thread-communication when there are no pending
		4179	watchers is very beneficial):
		4180
		4181	static void
		4182	l_invoke (EV_P)
		4183	{
		4184	userdata *u = ev_userdata (EV_A);
		4185
		4186	while (ev_pending_count (EV_A))
		4187	{
		4188	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4189	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4190	}
		4191	}
		4192
		4193	Now, whenever the main thread gets told to invoke pending watchers, it
		4194	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4195	thread to continue:
		4196
		4197	static void
		4198	real_invoke_pending (EV_P)
		4199	{
		4200	userdata *u = ev_userdata (EV_A);
		4201
		4202	pthread_mutex_lock (&u->lock);
		4203	ev_invoke_pending (EV_A);
		4204	pthread_cond_signal (&u->invoke_cv);
		4205	pthread_mutex_unlock (&u->lock);
		4206	}
		4207
		4208	Whenever you want to start/stop a watcher or do other modifications to an
		4209	event loop, you will now have to lock:
		4210
		4211	ev_timer timeout_watcher;
		4212	userdata *u = ev_userdata (EV_A);
		4213
		4214	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4215
		4216	pthread_mutex_lock (&u->lock);
		4217	ev_timer_start (EV_A_ &timeout_watcher);
		4218	ev_async_send (EV_A_ &u->async_w);
		4219	pthread_mutex_unlock (&u->lock);
		4220
		4221	Note that sending the C<ev_async> watcher is required because otherwise
		4222	an event loop currently blocking in the kernel will have no knowledge
		4223	about the newly added timer. By waking up the loop it will pick up any new
		4224	watchers in the next event loop iteration.
		4225
3873	=head3 COROUTINES	4226	=head3 COROUTINES
3874		4227
3875	Libev is very accommodating to coroutines ("cooperative threads"):	4228	Libev is very accommodating to coroutines ("cooperative threads"):
3876	libev fully supports nesting calls to its functions from different	4229	libev fully supports nesting calls to its functions from different
3877	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4230	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3878	different coroutines, and switch freely between both coroutines running the	4231	different coroutines, and switch freely between both coroutines running
3879	loop, as long as you don't confuse yourself). The only exception is that	4232	the loop, as long as you don't confuse yourself). The only exception is
3880	you must not do this from C<ev_periodic> reschedule callbacks.	4233	that you must not do this from C<ev_periodic> reschedule callbacks.
3881		4234
3882	Care has been taken to ensure that libev does not keep local state inside	4235	Care has been taken to ensure that libev does not keep local state inside
3883	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4236	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3884	they do not call any callbacks.	4237	they do not call any callbacks.
3885		4238

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Comparing libev/ev.pod (file contents): Revision 1.248 by root, Wed Jul 8 04:14:34 2009 UTC vs. Revision 1.277 by root, Thu Dec 31 06:50:17 2009 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.248 by root, Wed Jul 8 04:14:34 2009 UTC vs.
Revision 1.277 by root, Thu Dec 31 06:50:17 2009 UTC