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

Comparing libev/ev.pod (file contents):
Revision 1.255 by root, Tue Jul 14 19:11:31 2009 UTC vs.
Revision 1.261 by root, Mon Jul 20 04:18:20 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?");
…		…
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
…		…
1750		1772
1751	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
1752	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
1753	()>.	1775	()>.
1754		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
1755	=head3 Watcher-Specific Functions and Data Members	1807	=head3 Watcher-Specific Functions and Data Members
1756		1808
1757	=over 4	1809	=over 4
1758		1810
1759	=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)
…		…
1784	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
1785	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.
1786		1838
1787	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
1788	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.
1789		1853
1790	=item ev_tstamp repeat [read-write]	1854	=item ev_tstamp repeat [read-write]
1791		1855
1792	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
1793	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),
…		…
2029	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
2030	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
2031	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
2032	normal event processing, like any other event.	2096	normal event processing, like any other event.
2033		2097
2034	If you want signals asynchronously, just use C<sigaction> as you would	2098	If you want signals to be delivered truly asynchronously, just use
2035	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
2036	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.
2037		2102
2038	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
2039	first watcher gets started will libev actually register a signal handler	2109	When the first watcher gets started will libev actually register something
2040	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
2041	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).
2042	the last signal watcher for a signal is stopped, libev will reset the	2112
2043	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.
2044		2117
2045	If possible and supported, libev will install its handlers with	2118	If possible and supported, libev will install its handlers with
2046	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2119	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2047	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
2048	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
2049	them in an C<ev_prepare> watcher.	2122	and unblock them in an C<ev_prepare> watcher.
2050		2123
2051	=head3 Watcher-Specific Functions and Data Members	2124	=head3 Watcher-Specific Functions and Data Members
2052		2125
2053	=over 4	2126	=over 4
2054		2127
…		…
2099	libev)	2172	libev)
2100		2173
2101	=head3 Process Interaction	2174	=head3 Process Interaction
2102		2175
2103	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
2104	initialised. This is necessary to guarantee proper behaviour even if	2177	initialised. This is necessary to guarantee proper behaviour even if the
2105	the first child watcher is started after the child exits. The occurrence	2178	first child watcher is started after the child exits. The occurrence
2106	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2179	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2107	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
2108	children, even ones not watched.	2181	children, even ones not watched.
2109		2182
2110	=head3 Overriding the Built-In Processing	2183	=head3 Overriding the Built-In Processing
…		…
2120	=head3 Stopping the Child Watcher	2193	=head3 Stopping the Child Watcher
2121		2194
2122	Currently, the child watcher never gets stopped, even when the	2195	Currently, the child watcher never gets stopped, even when the
2123	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
2124	callback. Future versions of libev might stop the watcher automatically	2197	callback. Future versions of libev might stop the watcher automatically
2125	when a child exit is detected.	2198	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2199	problem).
2126		2200
2127	=head3 Watcher-Specific Functions and Data Members	2201	=head3 Watcher-Specific Functions and Data Members
2128		2202
2129	=over 4	2203	=over 4
2130		2204
…		…
3745	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	3819	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
3746	provide a bare-bones event library. See C<ev.h> for details on what parts	3820	provide a bare-bones event library. See C<ev.h> for details on what parts
3747	of the API are still available, and do not complain if this subset changes	3821	of the API are still available, and do not complain if this subset changes
3748	over time.	3822	over time.
3749		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.
		3832
3750	=item EV_PID_HASHSIZE	3833	=item EV_PID_HASHSIZE
3751		3834
3752	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
3753	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
3754	than enough. If you need to manage thousands of children you might want to	3837	than enough. If you need to manage thousands of children you might want to
…		…
4028	}	4111	}
4029		4112
4030	Instead of invoking all pending watchers, the C<l_invoke> callback will	4113	Instead of invoking all pending watchers, the C<l_invoke> callback will
4031	signal the main thread via some unspecified mechanism (signals? pipe	4114	signal the main thread via some unspecified mechanism (signals? pipe
4032	writes? C<Async::Interrupt>?) and then waits until all pending watchers	4115	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4033	have been called:	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):
4034		4119
4035	static void	4120	static void
4036	l_invoke (EV_P)	4121	l_invoke (EV_P)
4037	{	4122	{
4038	userdata *u = ev_userdata (EV_A);	4123	userdata *u = ev_userdata (EV_A);
4039		4124
		4125	while (ev_pending_count (EV_A))
		4126	{
4040	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();	4127	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4041
4042	pthread_cond_wait (&u->invoke_cv, &u->lock);	4128	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4129	}
4043	}	4130	}
4044		4131
4045	Now, whenever the main thread gets told to invoke pending watchers, it	4132	Now, whenever the main thread gets told to invoke pending watchers, it
4046	will grab the lock, call C<ev_invoke_pending> and then signal the loop	4133	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4047	thread to continue:	4134	thread to continue:

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Comparing libev/ev.pod (file contents): Revision 1.255 by root, Tue Jul 14 19:11:31 2009 UTC vs. Revision 1.261 by root, Mon Jul 20 04:18:20 2009 UTC

Diff Legend

Comparing libev/ev.pod (file contents):
Revision 1.255 by root, Tue Jul 14 19:11:31 2009 UTC vs.
Revision 1.261 by root, Mon Jul 20 04:18:20 2009 UTC