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

Comparing libev/ev.pod (file contents):
Revision 1.253 by root, Tue Jul 14 18:33:48 2009 UTC vs.
Revision 1.271 by root, Fri Sep 18 21:16:10 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
…		…
361	forget about forgetting to tell libev about forking) when you use this	362	forget about forgetting to tell libev about forking) when you use this
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.
		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_NOSIGFD>
		376
		377	When this flag is specified, then libev will not attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is
		379	probably only useful to work around any bugs in libev. Consequently, this
		380	flag might go away once the signalfd functionality is considered stable,
		381	so it's useful mostly in environment variables and not in program code.
366		382
367	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	383	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
368		384
369	This is your standard select(2) backend. Not I<completely> standard, as	385	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,	386	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
518		534
519	It is definitely not recommended to use this flag.	535	It is definitely not recommended to use this flag.
520		536
521	=back	537	=back
522		538
523	If one or more of these are or'ed into the flags value, then only these	539	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	540	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.	541	here). If none are specified, all backends in C<ev_recommended_backends
		542	()> will be tried.
526		543
527	Example: This is the most typical usage.	544	Example: This is the most typical usage.
528		545
529	if (!ev_default_loop (0))	546	if (!ev_default_loop (0))
530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	547	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
573	as signal and child watchers) would need to be stopped manually.	590	as signal and child watchers) would need to be stopped manually.
574		591
575	In general it is not advisable to call this function except in the	592	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	593	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	594	pipe fds. If you need dynamically allocated loops it is better to use
578	C<ev_loop_new> and C<ev_loop_destroy>).	595	C<ev_loop_new> and C<ev_loop_destroy>.
579		596
580	=item ev_loop_destroy (loop)	597	=item ev_loop_destroy (loop)
581		598
582	Like C<ev_default_destroy>, but destroys an event loop created by an	599	Like C<ev_default_destroy>, but destroys an event loop created by an
583	earlier call to C<ev_loop_new>.	600	earlier call to C<ev_loop_new>.
…		…
687	event loop time (see C<ev_now_update>).	704	event loop time (see C<ev_now_update>).
688		705
689	=item ev_loop (loop, int flags)	706	=item ev_loop (loop, int flags)
690		707
691	Finally, this is it, the event handler. This function usually is called	708	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	709	after you have initialised all your watchers and you want to start
693	events.	710	handling events.
694		711
695	If the flags argument is specified as C<0>, it will not return until	712	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.	713	either no event watchers are active anymore or C<ev_unloop> was called.
697		714
698	Please note that an explicit C<ev_unloop> is usually better than	715	Please note that an explicit C<ev_unloop> is usually better than
…		…
862		879
863	This call will simply invoke all pending watchers while resetting their	880	This call will simply invoke all pending watchers while resetting their
864	pending state. Normally, C<ev_loop> does this automatically when required,	881	pending state. Normally, C<ev_loop> does this automatically when required,
865	but when overriding the invoke callback this call comes handy.	882	but when overriding the invoke callback this call comes handy.
866		883
		884	=item int ev_pending_count (loop)
		885
		886	Returns the number of pending watchers - zero indicates that no watchers
		887	are pending.
		888
867	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	889	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
868		890
869	This overrides the invoke pending functionality of the loop: Instead of	891	This overrides the invoke pending functionality of the loop: Instead of
870	invoking all pending watchers when there are any, C<ev_loop> will call	892	invoking all pending watchers when there are any, C<ev_loop> will call
871	this callback instead. This is useful, for example, when you want to	893	this callback instead. This is useful, for example, when you want to
…		…
889	suspended waiting for new events, and C<acquire> is called just	911	suspended waiting for new events, and C<acquire> is called just
890	afterwards.	912	afterwards.
891		913
892	Ideally, C<release> will just call your mutex_unlock function, and	914	Ideally, C<release> will just call your mutex_unlock function, and
893	C<acquire> will just call the mutex_lock function again.	915	C<acquire> will just call the mutex_lock function again.
		916
		917	While event loop modifications are allowed between invocations of
		918	C<release> and C<acquire> (that's their only purpose after all), no
		919	modifications done will affect the event loop, i.e. adding watchers will
		920	have no effect on the set of file descriptors being watched, or the time
		921	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		922	to take note of any changes you made.
		923
		924	In theory, threads executing C<ev_loop> will be async-cancel safe between
		925	invocations of C<release> and C<acquire>.
		926
		927	See also the locking example in the C<THREADS> section later in this
		928	document.
894		929
895	=item ev_set_userdata (loop, void *data)	930	=item ev_set_userdata (loop, void *data)
896		931
897	=item ev_userdata (loop)	932	=item ev_userdata (loop)
898		933
…		…
1737		1772
1738	If the event loop is suspended for a long time, you can also force an	1773	If the event loop is suspended for a long time, you can also force an
1739	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1774	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1740	()>.	1775	()>.
1741		1776
		1777	=head3 The special problems of suspended animation
		1778
		1779	When you leave the server world it is quite customary to hit machines that
		1780	can suspend/hibernate - what happens to the clocks during such a suspend?
		1781
		1782	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1783	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1784	to run until the system is suspended, but they will not advance while the
		1785	system is suspended. That means, on resume, it will be as if the program
		1786	was frozen for a few seconds, but the suspend time will not be counted
		1787	towards C<ev_timer> when a monotonic clock source is used. The real time
		1788	clock advanced as expected, but if it is used as sole clocksource, then a
		1789	long suspend would be detected as a time jump by libev, and timers would
		1790	be adjusted accordingly.
		1791
		1792	I would not be surprised to see different behaviour in different between
		1793	operating systems, OS versions or even different hardware.
		1794
		1795	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1796	time jump in the monotonic clocks and the realtime clock. If the program
		1797	is suspended for a very long time, and monotonic clock sources are in use,
		1798	then you can expect C<ev_timer>s to expire as the full suspension time
		1799	will be counted towards the timers. When no monotonic clock source is in
		1800	use, then libev will again assume a timejump and adjust accordingly.
		1801
		1802	It might be beneficial for this latter case to call C<ev_suspend>
		1803	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1804	deterministic behaviour in this case (you can do nothing against
		1805	C<SIGSTOP>).
		1806
1742	=head3 Watcher-Specific Functions and Data Members	1807	=head3 Watcher-Specific Functions and Data Members
1743		1808
1744	=over 4	1809	=over 4
1745		1810
1746	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1811	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1771	If the timer is repeating, either start it if necessary (with the	1836	If the timer is repeating, either start it if necessary (with the
1772	C<repeat> value), or reset the running timer to the C<repeat> value.	1837	C<repeat> value), or reset the running timer to the C<repeat> value.
1773		1838
1774	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	1839	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1775	usage example.	1840	usage example.
		1841
		1842	=item ev_timer_remaining (loop, ev_timer *)
		1843
		1844	Returns the remaining time until a timer fires. If the timer is active,
		1845	then this time is relative to the current event loop time, otherwise it's
		1846	the timeout value currently configured.
		1847
		1848	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		1849	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
		1850	will return C<4>. When the timer expires and is restarted, it will return
		1851	roughly C<7> (likely slightly less as callback invocation takes some time,
		1852	too), and so on.
1776		1853
1777	=item ev_tstamp repeat [read-write]	1854	=item ev_tstamp repeat [read-write]
1778		1855
1779	The current C<repeat> value. Will be used each time the watcher times out	1856	The current C<repeat> value. Will be used each time the watcher times out
1780	or C<ev_timer_again> is called, and determines the next timeout (if any),	1857	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
2016	Signal watchers will trigger an event when the process receives a specific	2093	Signal watchers will trigger an event when the process receives a specific
2017	signal one or more times. Even though signals are very asynchronous, libev	2094	signal one or more times. Even though signals are very asynchronous, libev
2018	will try it's best to deliver signals synchronously, i.e. as part of the	2095	will try it's best to deliver signals synchronously, i.e. as part of the
2019	normal event processing, like any other event.	2096	normal event processing, like any other event.
2020		2097
2021	If you want signals asynchronously, just use C<sigaction> as you would	2098	If you want signals to be delivered truly asynchronously, just use
2022	do without libev and forget about sharing the signal. You can even use	2099	C<sigaction> as you would do without libev and forget about sharing
2023	C<ev_async> from a signal handler to synchronously wake up an event loop.	2100	the signal. You can even use C<ev_async> from a signal handler to
		2101	synchronously wake up an event loop.
2024		2102
2025	You can configure as many watchers as you like per signal. Only when the	2103	You can configure as many watchers as you like for the same signal, but
		2104	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2105	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2106	C<SIGINT> in both the default loop and another loop at the same time. At
		2107	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2108
2026	first watcher gets started will libev actually register a signal handler	2109	When the first watcher gets started will libev actually register something
2027	with the kernel (thus it coexists with your own signal handlers as long as	2110	with the kernel (thus it coexists with your own signal handlers as long as
2028	you don't register any with libev for the same signal). Similarly, when	2111	you don't register any with libev for the same signal).
2029	the last signal watcher for a signal is stopped, libev will reset the
2030	signal handler to SIG_DFL (regardless of what it was set to before).
2031		2112
2032	If possible and supported, libev will install its handlers with	2113	If possible and supported, libev will install its handlers with
2033	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2114	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2034	interrupted. If you have a problem with system calls getting interrupted by	2115	not be unduly interrupted. If you have a problem with system calls getting
2035	signals you can block all signals in an C<ev_check> watcher and unblock	2116	interrupted by signals you can block all signals in an C<ev_check> watcher
2036	them in an C<ev_prepare> watcher.	2117	and unblock them in an C<ev_prepare> watcher.
		2118
		2119	=head3 The special problem of inheritance over execve
		2120
		2121	Both the signal mask (C<sigprocmask>) and the signal disposition
		2122	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2123	stopping it again), that is, libev might or might not block the signal,
		2124	and might or might not set or restore the installed signal handler.
		2125
		2126	While this does not matter for the signal disposition (libev never
		2127	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2128	C<execve>), this matters for the signal mask: many programs do not expect
		2129	certain signals to be blocked.
		2130
		2131	This means that before calling C<exec> (from the child) you should reset
		2132	the signal mask to whatever "default" you expect (all clear is a good
		2133	choice usually).
		2134
		2135	The simplest way to ensure that the signal mask is reset in the child is
		2136	to install a fork handler with C<pthread_atfork> that resets it. That will
		2137	catch fork calls done by libraries (such as the libc) as well.
		2138
		2139	In current versions of libev, you can also ensure that the signal mask is
		2140	not blocking any signals (except temporarily, so thread users watch out)
		2141	by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This
		2142	is not guaranteed for future versions, however.
2037		2143
2038	=head3 Watcher-Specific Functions and Data Members	2144	=head3 Watcher-Specific Functions and Data Members
2039		2145
2040	=over 4	2146	=over 4
2041		2147
…		…
2086	libev)	2192	libev)
2087		2193
2088	=head3 Process Interaction	2194	=head3 Process Interaction
2089		2195
2090	Libev grabs C<SIGCHLD> as soon as the default event loop is	2196	Libev grabs C<SIGCHLD> as soon as the default event loop is
2091	initialised. This is necessary to guarantee proper behaviour even if	2197	initialised. This is necessary to guarantee proper behaviour even if the
2092	the first child watcher is started after the child exits. The occurrence	2198	first child watcher is started after the child exits. The occurrence
2093	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2199	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2094	synchronously as part of the event loop processing. Libev always reaps all	2200	synchronously as part of the event loop processing. Libev always reaps all
2095	children, even ones not watched.	2201	children, even ones not watched.
2096		2202
2097	=head3 Overriding the Built-In Processing	2203	=head3 Overriding the Built-In Processing
…		…
2107	=head3 Stopping the Child Watcher	2213	=head3 Stopping the Child Watcher
2108		2214
2109	Currently, the child watcher never gets stopped, even when the	2215	Currently, the child watcher never gets stopped, even when the
2110	child terminates, so normally one needs to stop the watcher in the	2216	child terminates, so normally one needs to stop the watcher in the
2111	callback. Future versions of libev might stop the watcher automatically	2217	callback. Future versions of libev might stop the watcher automatically
2112	when a child exit is detected.	2218	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2219	problem).
2113		2220
2114	=head3 Watcher-Specific Functions and Data Members	2221	=head3 Watcher-Specific Functions and Data Members
2115		2222
2116	=over 4	2223	=over 4
2117		2224
…		…
3320	=item Ocaml	3427	=item Ocaml
3321		3428
3322	Erkki Seppala has written Ocaml bindings for libev, to be found at	3429	Erkki Seppala has written Ocaml bindings for libev, to be found at
3323	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3430	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3324		3431
		3432	=item Lua
		3433
		3434	Brian Maher has written a partial interface to libev
		3435	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3436	L<http://github.com/brimworks/lua-ev>.
		3437
3325	=back	3438	=back
3326		3439
3327		3440
3328	=head1 MACRO MAGIC	3441	=head1 MACRO MAGIC
3329		3442
…		…
3495	keeps libev from including F<config.h>, and it also defines dummy	3608	keeps libev from including F<config.h>, and it also defines dummy
3496	implementations for some libevent functions (such as logging, which is not	3609	implementations for some libevent functions (such as logging, which is not
3497	supported). It will also not define any of the structs usually found in	3610	supported). It will also not define any of the structs usually found in
3498	F<event.h> that are not directly supported by the libev core alone.	3611	F<event.h> that are not directly supported by the libev core alone.
3499		3612
3500	In stanbdalone mode, libev will still try to automatically deduce the	3613	In standalone mode, libev will still try to automatically deduce the
3501	configuration, but has to be more conservative.	3614	configuration, but has to be more conservative.
3502		3615
3503	=item EV_USE_MONOTONIC	3616	=item EV_USE_MONOTONIC
3504		3617
3505	If defined to be C<1>, libev will try to detect the availability of the	3618	If defined to be C<1>, libev will try to detect the availability of the
…		…
3570	be used is the winsock select). This means that it will call	3683	be used is the winsock select). This means that it will call
3571	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3684	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3572	it is assumed that all these functions actually work on fds, even	3685	it is assumed that all these functions actually work on fds, even
3573	on win32. Should not be defined on non-win32 platforms.	3686	on win32. Should not be defined on non-win32 platforms.
3574		3687
3575	=item EV_FD_TO_WIN32_HANDLE	3688	=item EV_FD_TO_WIN32_HANDLE(fd)
3576		3689
3577	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3690	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3578	file descriptors to socket handles. When not defining this symbol (the	3691	file descriptors to socket handles. When not defining this symbol (the
3579	default), then libev will call C<_get_osfhandle>, which is usually	3692	default), then libev will call C<_get_osfhandle>, which is usually
3580	correct. In some cases, programs use their own file descriptor management,	3693	correct. In some cases, programs use their own file descriptor management,
3581	in which case they can provide this function to map fds to socket handles.	3694	in which case they can provide this function to map fds to socket handles.
		3695
		3696	=item EV_WIN32_HANDLE_TO_FD(handle)
		3697
		3698	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3699	using the standard C<_open_osfhandle> function. For programs implementing
		3700	their own fd to handle mapping, overwriting this function makes it easier
		3701	to do so. This can be done by defining this macro to an appropriate value.
		3702
		3703	=item EV_WIN32_CLOSE_FD(fd)
		3704
		3705	If programs implement their own fd to handle mapping on win32, then this
		3706	macro can be used to override the C<close> function, useful to unregister
		3707	file descriptors again. Note that the replacement function has to close
		3708	the underlying OS handle.
3582		3709
3583	=item EV_USE_POLL	3710	=item EV_USE_POLL
3584		3711
3585	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3712	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3586	backend. Otherwise it will be enabled on non-win32 platforms. It	3713	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3732	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	3859	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
3733	provide a bare-bones event library. See C<ev.h> for details on what parts	3860	provide a bare-bones event library. See C<ev.h> for details on what parts
3734	of the API are still available, and do not complain if this subset changes	3861	of the API are still available, and do not complain if this subset changes
3735	over time.	3862	over time.
3736		3863
		3864	=item EV_NSIG
		3865
		3866	The highest supported signal number, +1 (or, the number of
		3867	signals): Normally, libev tries to deduce the maximum number of signals
		3868	automatically, but sometimes this fails, in which case it can be
		3869	specified. Also, using a lower number than detected (C<32> should be
		3870	good for about any system in existance) can save some memory, as libev
		3871	statically allocates some 12-24 bytes per signal number.
		3872
3737	=item EV_PID_HASHSIZE	3873	=item EV_PID_HASHSIZE
3738		3874
3739	C<ev_child> watchers use a small hash table to distribute workload by	3875	C<ev_child> watchers use a small hash table to distribute workload by
3740	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3876	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
3741	than enough. If you need to manage thousands of children you might want to	3877	than enough. If you need to manage thousands of children you might want to
…		…
3928		4064
3929	=back	4065	=back
3930		4066
3931	=head4 THREAD LOCKING EXAMPLE	4067	=head4 THREAD LOCKING EXAMPLE
3932		4068
		4069	Here is a fictitious example of how to run an event loop in a different
		4070	thread than where callbacks are being invoked and watchers are
		4071	created/added/removed.
		4072
		4073	For a real-world example, see the C<EV::Loop::Async> perl module,
		4074	which uses exactly this technique (which is suited for many high-level
		4075	languages).
		4076
		4077	The example uses a pthread mutex to protect the loop data, a condition
		4078	variable to wait for callback invocations, an async watcher to notify the
		4079	event loop thread and an unspecified mechanism to wake up the main thread.
		4080
		4081	First, you need to associate some data with the event loop:
		4082
		4083	typedef struct {
		4084	mutex_t lock; /* global loop lock */
		4085	ev_async async_w;
		4086	thread_t tid;
		4087	cond_t invoke_cv;
		4088	} userdata;
		4089
		4090	void prepare_loop (EV_P)
		4091	{
		4092	// for simplicity, we use a static userdata struct.
		4093	static userdata u;
		4094
		4095	ev_async_init (&u->async_w, async_cb);
		4096	ev_async_start (EV_A_ &u->async_w);
		4097
		4098	pthread_mutex_init (&u->lock, 0);
		4099	pthread_cond_init (&u->invoke_cv, 0);
		4100
		4101	// now associate this with the loop
		4102	ev_set_userdata (EV_A_ u);
		4103	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4104	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4105
		4106	// then create the thread running ev_loop
		4107	pthread_create (&u->tid, 0, l_run, EV_A);
		4108	}
		4109
		4110	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4111	solely to wake up the event loop so it takes notice of any new watchers
		4112	that might have been added:
		4113
		4114	static void
		4115	async_cb (EV_P_ ev_async *w, int revents)
		4116	{
		4117	// just used for the side effects
		4118	}
		4119
		4120	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4121	protecting the loop data, respectively.
		4122
		4123	static void
		4124	l_release (EV_P)
		4125	{
		4126	userdata *u = ev_userdata (EV_A);
		4127	pthread_mutex_unlock (&u->lock);
		4128	}
		4129
		4130	static void
		4131	l_acquire (EV_P)
		4132	{
		4133	userdata *u = ev_userdata (EV_A);
		4134	pthread_mutex_lock (&u->lock);
		4135	}
		4136
		4137	The event loop thread first acquires the mutex, and then jumps straight
		4138	into C<ev_loop>:
		4139
		4140	void *
		4141	l_run (void *thr_arg)
		4142	{
		4143	struct ev_loop loop = (struct ev_loop )thr_arg;
		4144
		4145	l_acquire (EV_A);
		4146	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4147	ev_loop (EV_A_ 0);
		4148	l_release (EV_A);
		4149
		4150	return 0;
		4151	}
		4152
		4153	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4154	signal the main thread via some unspecified mechanism (signals? pipe
		4155	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4156	have been called (in a while loop because a) spurious wakeups are possible
		4157	and b) skipping inter-thread-communication when there are no pending
		4158	watchers is very beneficial):
		4159
		4160	static void
		4161	l_invoke (EV_P)
		4162	{
		4163	userdata *u = ev_userdata (EV_A);
		4164
		4165	while (ev_pending_count (EV_A))
		4166	{
		4167	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4168	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4169	}
		4170	}
		4171
		4172	Now, whenever the main thread gets told to invoke pending watchers, it
		4173	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4174	thread to continue:
		4175
		4176	static void
		4177	real_invoke_pending (EV_P)
		4178	{
		4179	userdata *u = ev_userdata (EV_A);
		4180
		4181	pthread_mutex_lock (&u->lock);
		4182	ev_invoke_pending (EV_A);
		4183	pthread_cond_signal (&u->invoke_cv);
		4184	pthread_mutex_unlock (&u->lock);
		4185	}
		4186
		4187	Whenever you want to start/stop a watcher or do other modifications to an
		4188	event loop, you will now have to lock:
		4189
		4190	ev_timer timeout_watcher;
		4191	userdata *u = ev_userdata (EV_A);
		4192
		4193	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4194
		4195	pthread_mutex_lock (&u->lock);
		4196	ev_timer_start (EV_A_ &timeout_watcher);
		4197	ev_async_send (EV_A_ &u->async_w);
		4198	pthread_mutex_unlock (&u->lock);
		4199
		4200	Note that sending the C<ev_async> watcher is required because otherwise
		4201	an event loop currently blocking in the kernel will have no knowledge
		4202	about the newly added timer. By waking up the loop it will pick up any new
		4203	watchers in the next event loop iteration.
		4204
3933	=head3 COROUTINES	4205	=head3 COROUTINES
3934		4206
3935	Libev is very accommodating to coroutines ("cooperative threads"):	4207	Libev is very accommodating to coroutines ("cooperative threads"):
3936	libev fully supports nesting calls to its functions from different	4208	libev fully supports nesting calls to its functions from different
3937	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4209	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3938	different coroutines, and switch freely between both coroutines running the	4210	different coroutines, and switch freely between both coroutines running
3939	loop, as long as you don't confuse yourself). The only exception is that	4211	the loop, as long as you don't confuse yourself). The only exception is
3940	you must not do this from C<ev_periodic> reschedule callbacks.	4212	that you must not do this from C<ev_periodic> reschedule callbacks.
3941		4213
3942	Care has been taken to ensure that libev does not keep local state inside	4214	Care has been taken to ensure that libev does not keep local state inside
3943	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4215	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3944	they do not call any callbacks.	4216	they do not call any callbacks.
3945		4217

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Comparing libev/ev.pod (file contents): Revision 1.253 by root, Tue Jul 14 18:33:48 2009 UTC vs. Revision 1.271 by root, Fri Sep 18 21:16:10 2009 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.253 by root, Tue Jul 14 18:33:48 2009 UTC vs.
Revision 1.271 by root, Fri Sep 18 21:16:10 2009 UTC