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

Comparing libev/ev.pod (file contents):
Revision 1.246 by root, Thu Jul 2 12:08:55 2009 UTC vs.
Revision 1.262 by root, Sat Jul 25 10:14:34 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_NOSIGNALFD>
		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?");
…		…
620	happily wraps around with enough iterations.	637	happily wraps around with enough iterations.
621		638
622	This value can sometimes be useful as a generation counter of sorts (it	639	This value can sometimes be useful as a generation counter of sorts (it
623	"ticks" the number of loop iterations), as it roughly corresponds with	640	"ticks" the number of loop iterations), as it roughly corresponds with
624	C<ev_prepare> and C<ev_check> calls.	641	C<ev_prepare> and C<ev_check> calls.
		642
		643	=item unsigned int ev_loop_depth (loop)
		644
		645	Returns the number of times C<ev_loop> was entered minus the number of
		646	times C<ev_loop> was exited, in other words, the recursion depth.
		647
		648	Outside C<ev_loop>, this number is zero. In a callback, this number is
		649	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		650	in which case it is higher.
		651
		652	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		653	etc.), doesn't count as exit.
625		654
626	=item unsigned int ev_backend (loop)	655	=item unsigned int ev_backend (loop)
627		656
628	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	657	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
629	use.	658	use.
…		…
844	more often than 100 times per second:	873	more often than 100 times per second:
845		874
846	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);	875	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
847	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	876	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
848		877
		878	=item ev_invoke_pending (loop)
		879
		880	This call will simply invoke all pending watchers while resetting their
		881	pending state. Normally, C<ev_loop> does this automatically when required,
		882	but when overriding the invoke callback this call comes handy.
		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
		889	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		890
		891	This overrides the invoke pending functionality of the loop: Instead of
		892	invoking all pending watchers when there are any, C<ev_loop> will call
		893	this callback instead. This is useful, for example, when you want to
		894	invoke the actual watchers inside another context (another thread etc.).
		895
		896	If you want to reset the callback, use C<ev_invoke_pending> as new
		897	callback.
		898
		899	=item ev_set_loop_release_cb (loop, void (release)(EV_P), void (acquire)(EV_P))
		900
		901	Sometimes you want to share the same loop between multiple threads. This
		902	can be done relatively simply by putting mutex_lock/unlock calls around
		903	each call to a libev function.
		904
		905	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		906	wait for it to return. One way around this is to wake up the loop via
		907	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		908	and I<acquire> callbacks on the loop.
		909
		910	When set, then C<release> will be called just before the thread is
		911	suspended waiting for new events, and C<acquire> is called just
		912	afterwards.
		913
		914	Ideally, C<release> will just call your mutex_unlock function, and
		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.
		929
		930	=item ev_set_userdata (loop, void *data)
		931
		932	=item ev_userdata (loop)
		933
		934	Set and retrieve a single C<void *> associated with a loop. When
		935	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		936	C<0.>
		937
		938	These two functions can be used to associate arbitrary data with a loop,
		939	and are intended solely for the C<invoke_pending_cb>, C<release> and
		940	C<acquire> callbacks described above, but of course can be (ab-)used for
		941	any other purpose as well.
		942
849	=item ev_loop_verify (loop)	943	=item ev_loop_verify (loop)
850		944
851	This function only does something when C<EV_VERIFY> support has been	945	This function only does something when C<EV_VERIFY> support has been
852	compiled in, which is the default for non-minimal builds. It tries to go	946	compiled in, which is the default for non-minimal builds. It tries to go
853	through all internal structures and checks them for validity. If anything	947	through all internal structures and checks them for validity. If anything
…		…
1480		1574
1481	The callback is guaranteed to be invoked only I<after> its timeout has	1575	The callback is guaranteed to be invoked only I<after> its timeout has
1482	passed (not I<at>, so on systems with very low-resolution clocks this	1576	passed (not I<at>, so on systems with very low-resolution clocks this
1483	might introduce a small delay). If multiple timers become ready during the	1577	might introduce a small delay). If multiple timers become ready during the
1484	same loop iteration then the ones with earlier time-out values are invoked	1578	same loop iteration then the ones with earlier time-out values are invoked
1485	before ones with later time-out values (but this is no longer true when a	1579	before ones of the same priority with later time-out values (but this is
1486	callback calls C<ev_loop> recursively).	1580	no longer true when a callback calls C<ev_loop> recursively).
1487		1581
1488	=head3 Be smart about timeouts	1582	=head3 Be smart about timeouts
1489		1583
1490	Many real-world problems involve some kind of timeout, usually for error	1584	Many real-world problems involve some kind of timeout, usually for error
1491	recovery. A typical example is an HTTP request - if the other side hangs,	1585	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1678		1772
1679	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
1680	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
1681	()>.	1775	()>.
1682		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
1683	=head3 Watcher-Specific Functions and Data Members	1807	=head3 Watcher-Specific Functions and Data Members
1684		1808
1685	=over 4	1809	=over 4
1686		1810
1687	=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)
…		…
1712	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
1713	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.
1714		1838
1715	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
1716	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.
1717		1853
1718	=item ev_tstamp repeat [read-write]	1854	=item ev_tstamp repeat [read-write]
1719		1855
1720	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
1721	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),
…		…
1957	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
1958	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
1959	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
1960	normal event processing, like any other event.	2096	normal event processing, like any other event.
1961		2097
1962	If you want signals asynchronously, just use C<sigaction> as you would	2098	If you want signals to be delivered truly asynchronously, just use
1963	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
1964	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.
1965		2102
1966	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
1967	first watcher gets started will libev actually register a signal handler	2109	When the first watcher gets started will libev actually register something
1968	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
1969	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).
1970	the last signal watcher for a signal is stopped, libev will reset the	2112
1971	signal handler to SIG_DFL (regardless of what it was set to before).	2113	Both the signal mask state (C<sigprocmask>) and the signal handler state
		2114	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2115	sotpping it again), that is, libev might or might not block the signal,
		2116	and might or might not set or restore the installed signal handler.
1972		2117
1973	If possible and supported, libev will install its handlers with	2118	If possible and supported, libev will install its handlers with
1974	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2119	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1975	interrupted. If you have a problem with system calls getting interrupted by	2120	not be unduly interrupted. If you have a problem with system calls getting
1976	signals you can block all signals in an C<ev_check> watcher and unblock	2121	interrupted by signals you can block all signals in an C<ev_check> watcher
1977	them in an C<ev_prepare> watcher.	2122	and unblock them in an C<ev_prepare> watcher.
1978		2123
1979	=head3 Watcher-Specific Functions and Data Members	2124	=head3 Watcher-Specific Functions and Data Members
1980		2125
1981	=over 4	2126	=over 4
1982		2127
…		…
2020	in the next callback invocation is not.	2165	in the next callback invocation is not.
2021		2166
2022	Only the default event loop is capable of handling signals, and therefore	2167	Only the default event loop is capable of handling signals, and therefore
2023	you can only register child watchers in the default event loop.	2168	you can only register child watchers in the default event loop.
2024		2169
		2170	Due to some design glitches inside libev, child watchers will always be
		2171	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2172	libev)
		2173
2025	=head3 Process Interaction	2174	=head3 Process Interaction
2026		2175
2027	Libev grabs C<SIGCHLD> as soon as the default event loop is	2176	Libev grabs C<SIGCHLD> as soon as the default event loop is
2028	initialised. This is necessary to guarantee proper behaviour even if	2177	initialised. This is necessary to guarantee proper behaviour even if the
2029	the first child watcher is started after the child exits. The occurrence	2178	first child watcher is started after the child exits. The occurrence
2030	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2179	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2031	synchronously as part of the event loop processing. Libev always reaps all	2180	synchronously as part of the event loop processing. Libev always reaps all
2032	children, even ones not watched.	2181	children, even ones not watched.
2033		2182
2034	=head3 Overriding the Built-In Processing	2183	=head3 Overriding the Built-In Processing
…		…
2044	=head3 Stopping the Child Watcher	2193	=head3 Stopping the Child Watcher
2045		2194
2046	Currently, the child watcher never gets stopped, even when the	2195	Currently, the child watcher never gets stopped, even when the
2047	child terminates, so normally one needs to stop the watcher in the	2196	child terminates, so normally one needs to stop the watcher in the
2048	callback. Future versions of libev might stop the watcher automatically	2197	callback. Future versions of libev might stop the watcher automatically
2049	when a child exit is detected.	2198	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2199	problem).
2050		2200
2051	=head3 Watcher-Specific Functions and Data Members	2201	=head3 Watcher-Specific Functions and Data Members
2052		2202
2053	=over 4	2203	=over 4
2054		2204
…		…
3432	keeps libev from including F<config.h>, and it also defines dummy	3582	keeps libev from including F<config.h>, and it also defines dummy
3433	implementations for some libevent functions (such as logging, which is not	3583	implementations for some libevent functions (such as logging, which is not
3434	supported). It will also not define any of the structs usually found in	3584	supported). It will also not define any of the structs usually found in
3435	F<event.h> that are not directly supported by the libev core alone.	3585	F<event.h> that are not directly supported by the libev core alone.
3436		3586
3437	In stanbdalone mode, libev will still try to automatically deduce the	3587	In standalone mode, libev will still try to automatically deduce the
3438	configuration, but has to be more conservative.	3588	configuration, but has to be more conservative.
3439		3589
3440	=item EV_USE_MONOTONIC	3590	=item EV_USE_MONOTONIC
3441		3591
3442	If defined to be C<1>, libev will try to detect the availability of the	3592	If defined to be C<1>, libev will try to detect the availability of the
…		…
3655	defined to be C<0>, then they are not.	3805	defined to be C<0>, then they are not.
3656		3806
3657	=item EV_MINIMAL	3807	=item EV_MINIMAL
3658		3808
3659	If you need to shave off some kilobytes of code at the expense of some	3809	If you need to shave off some kilobytes of code at the expense of some
3660	speed, define this symbol to C<1>. Currently this is used to override some	3810	speed (but with the full API), define this symbol to C<1>. Currently this
3661	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3811	is used to override some inlining decisions, saves roughly 30% code size
3662	much smaller 2-heap for timer management over the default 4-heap.	3812	on amd64. It also selects a much smaller 2-heap for timer management over
		3813	the default 4-heap.
		3814
		3815	You can save even more by disabling watcher types you do not need
		3816	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3817	(C<-DNDEBUG>) will usually reduce code size a lot.
		3818
		3819	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3820	provide a bare-bones event library. See C<ev.h> for details on what parts
		3821	of the API are still available, and do not complain if this subset changes
		3822	over time.
		3823
		3824	=item EV_NSIG
		3825
		3826	The highest supported signal number, +1 (or, the number of
		3827	signals): Normally, libev tries to deduce the maximum number of signals
		3828	automatically, but sometimes this fails, in which case it can be
		3829	specified. Also, using a lower number than detected (C<32> should be
		3830	good for about any system in existance) can save some memory, as libev
		3831	statically allocates some 12-24 bytes per signal number.
3663		3832
3664	=item EV_PID_HASHSIZE	3833	=item EV_PID_HASHSIZE
3665		3834
3666	C<ev_child> watchers use a small hash table to distribute workload by	3835	C<ev_child> watchers use a small hash table to distribute workload by
3667	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3836	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3853	default loop and triggering an C<ev_async> watcher from the default loop	4022	default loop and triggering an C<ev_async> watcher from the default loop
3854	watcher callback into the event loop interested in the signal.	4023	watcher callback into the event loop interested in the signal.
3855		4024
3856	=back	4025	=back
3857		4026
		4027	=head4 THREAD LOCKING EXAMPLE
		4028
		4029	Here is a fictitious example of how to run an event loop in a different
		4030	thread than where callbacks are being invoked and watchers are
		4031	created/added/removed.
		4032
		4033	For a real-world example, see the C<EV::Loop::Async> perl module,
		4034	which uses exactly this technique (which is suited for many high-level
		4035	languages).
		4036
		4037	The example uses a pthread mutex to protect the loop data, a condition
		4038	variable to wait for callback invocations, an async watcher to notify the
		4039	event loop thread and an unspecified mechanism to wake up the main thread.
		4040
		4041	First, you need to associate some data with the event loop:
		4042
		4043	typedef struct {
		4044	mutex_t lock; /* global loop lock */
		4045	ev_async async_w;
		4046	thread_t tid;
		4047	cond_t invoke_cv;
		4048	} userdata;
		4049
		4050	void prepare_loop (EV_P)
		4051	{
		4052	// for simplicity, we use a static userdata struct.
		4053	static userdata u;
		4054
		4055	ev_async_init (&u->async_w, async_cb);
		4056	ev_async_start (EV_A_ &u->async_w);
		4057
		4058	pthread_mutex_init (&u->lock, 0);
		4059	pthread_cond_init (&u->invoke_cv, 0);
		4060
		4061	// now associate this with the loop
		4062	ev_set_userdata (EV_A_ u);
		4063	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4064	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4065
		4066	// then create the thread running ev_loop
		4067	pthread_create (&u->tid, 0, l_run, EV_A);
		4068	}
		4069
		4070	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4071	solely to wake up the event loop so it takes notice of any new watchers
		4072	that might have been added:
		4073
		4074	static void
		4075	async_cb (EV_P_ ev_async *w, int revents)
		4076	{
		4077	// just used for the side effects
		4078	}
		4079
		4080	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4081	protecting the loop data, respectively.
		4082
		4083	static void
		4084	l_release (EV_P)
		4085	{
		4086	userdata *u = ev_userdata (EV_A);
		4087	pthread_mutex_unlock (&u->lock);
		4088	}
		4089
		4090	static void
		4091	l_acquire (EV_P)
		4092	{
		4093	userdata *u = ev_userdata (EV_A);
		4094	pthread_mutex_lock (&u->lock);
		4095	}
		4096
		4097	The event loop thread first acquires the mutex, and then jumps straight
		4098	into C<ev_loop>:
		4099
		4100	void *
		4101	l_run (void *thr_arg)
		4102	{
		4103	struct ev_loop loop = (struct ev_loop )thr_arg;
		4104
		4105	l_acquire (EV_A);
		4106	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4107	ev_loop (EV_A_ 0);
		4108	l_release (EV_A);
		4109
		4110	return 0;
		4111	}
		4112
		4113	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4114	signal the main thread via some unspecified mechanism (signals? pipe
		4115	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4116	have been called (in a while loop because a) spurious wakeups are possible
		4117	and b) skipping inter-thread-communication when there are no pending
		4118	watchers is very beneficial):
		4119
		4120	static void
		4121	l_invoke (EV_P)
		4122	{
		4123	userdata *u = ev_userdata (EV_A);
		4124
		4125	while (ev_pending_count (EV_A))
		4126	{
		4127	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4128	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4129	}
		4130	}
		4131
		4132	Now, whenever the main thread gets told to invoke pending watchers, it
		4133	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4134	thread to continue:
		4135
		4136	static void
		4137	real_invoke_pending (EV_P)
		4138	{
		4139	userdata *u = ev_userdata (EV_A);
		4140
		4141	pthread_mutex_lock (&u->lock);
		4142	ev_invoke_pending (EV_A);
		4143	pthread_cond_signal (&u->invoke_cv);
		4144	pthread_mutex_unlock (&u->lock);
		4145	}
		4146
		4147	Whenever you want to start/stop a watcher or do other modifications to an
		4148	event loop, you will now have to lock:
		4149
		4150	ev_timer timeout_watcher;
		4151	userdata *u = ev_userdata (EV_A);
		4152
		4153	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4154
		4155	pthread_mutex_lock (&u->lock);
		4156	ev_timer_start (EV_A_ &timeout_watcher);
		4157	ev_async_send (EV_A_ &u->async_w);
		4158	pthread_mutex_unlock (&u->lock);
		4159
		4160	Note that sending the C<ev_async> watcher is required because otherwise
		4161	an event loop currently blocking in the kernel will have no knowledge
		4162	about the newly added timer. By waking up the loop it will pick up any new
		4163	watchers in the next event loop iteration.
		4164
3858	=head3 COROUTINES	4165	=head3 COROUTINES
3859		4166
3860	Libev is very accommodating to coroutines ("cooperative threads"):	4167	Libev is very accommodating to coroutines ("cooperative threads"):
3861	libev fully supports nesting calls to its functions from different	4168	libev fully supports nesting calls to its functions from different
3862	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4169	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3863	different coroutines, and switch freely between both coroutines running the	4170	different coroutines, and switch freely between both coroutines running
3864	loop, as long as you don't confuse yourself). The only exception is that	4171	the loop, as long as you don't confuse yourself). The only exception is
3865	you must not do this from C<ev_periodic> reschedule callbacks.	4172	that you must not do this from C<ev_periodic> reschedule callbacks.
3866		4173
3867	Care has been taken to ensure that libev does not keep local state inside	4174	Care has been taken to ensure that libev does not keep local state inside
3868	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4175	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3869	they do not call any callbacks.	4176	they do not call any callbacks.
3870		4177

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Comparing libev/ev.pod (file contents): Revision 1.246 by root, Thu Jul 2 12:08:55 2009 UTC vs. Revision 1.262 by root, Sat Jul 25 10:14:34 2009 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.246 by root, Thu Jul 2 12:08:55 2009 UTC vs.
Revision 1.262 by root, Sat Jul 25 10:14:34 2009 UTC