… | |
… | |
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?"); |
… | |
… | |
856 | more often than 100 times per second: |
873 | more often than 100 times per second: |
857 | |
874 | |
858 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
875 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
859 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
876 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
860 | |
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 | |
861 | =item ev_loop_verify (loop) |
943 | =item ev_loop_verify (loop) |
862 | |
944 | |
863 | 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 |
864 | 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 |
865 | through all internal structures and checks them for validity. If anything |
947 | through all internal structures and checks them for validity. If anything |
… | |
… | |
1690 | |
1772 | |
1691 | 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 |
1692 | 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 |
1693 | ()>. |
1775 | ()>. |
1694 | |
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 | |
1695 | =head3 Watcher-Specific Functions and Data Members |
1807 | =head3 Watcher-Specific Functions and Data Members |
1696 | |
1808 | |
1697 | =over 4 |
1809 | =over 4 |
1698 | |
1810 | |
1699 | =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) |
… | |
… | |
1724 | 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 |
1725 | 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. |
1726 | |
1838 | |
1727 | 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 |
1728 | 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. |
1729 | |
1853 | |
1730 | =item ev_tstamp repeat [read-write] |
1854 | =item ev_tstamp repeat [read-write] |
1731 | |
1855 | |
1732 | 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 |
1733 | 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), |
… | |
… | |
1969 | 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 |
1970 | 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 |
1971 | 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 |
1972 | normal event processing, like any other event. |
2096 | normal event processing, like any other event. |
1973 | |
2097 | |
1974 | If you want signals asynchronously, just use C<sigaction> as you would |
2098 | 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 |
2099 | 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. |
2100 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2101 | synchronously wake up an event loop. |
1977 | |
2102 | |
1978 | 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 | |
1979 | first watcher gets started will libev actually register a signal handler |
2109 | 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 |
2110 | 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 |
2111 | 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 |
2112 | |
1983 | 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. |
1984 | |
2117 | |
1985 | If possible and supported, libev will install its handlers with |
2118 | If possible and supported, libev will install its handlers with |
1986 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2119 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1987 | 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 |
1988 | 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 |
1989 | them in an C<ev_prepare> watcher. |
2122 | and unblock them in an C<ev_prepare> watcher. |
1990 | |
2123 | |
1991 | =head3 Watcher-Specific Functions and Data Members |
2124 | =head3 Watcher-Specific Functions and Data Members |
1992 | |
2125 | |
1993 | =over 4 |
2126 | =over 4 |
1994 | |
2127 | |
… | |
… | |
2039 | libev) |
2172 | libev) |
2040 | |
2173 | |
2041 | =head3 Process Interaction |
2174 | =head3 Process Interaction |
2042 | |
2175 | |
2043 | 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 |
2044 | initialised. This is necessary to guarantee proper behaviour even if |
2177 | initialised. This is necessary to guarantee proper behaviour even if the |
2045 | the first child watcher is started after the child exits. The occurrence |
2178 | first child watcher is started after the child exits. The occurrence |
2046 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2179 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2047 | 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 |
2048 | children, even ones not watched. |
2181 | children, even ones not watched. |
2049 | |
2182 | |
2050 | =head3 Overriding the Built-In Processing |
2183 | =head3 Overriding the Built-In Processing |
… | |
… | |
2060 | =head3 Stopping the Child Watcher |
2193 | =head3 Stopping the Child Watcher |
2061 | |
2194 | |
2062 | Currently, the child watcher never gets stopped, even when the |
2195 | Currently, the child watcher never gets stopped, even when the |
2063 | 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 |
2064 | callback. Future versions of libev might stop the watcher automatically |
2197 | callback. Future versions of libev might stop the watcher automatically |
2065 | when a child exit is detected. |
2198 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2199 | problem). |
2066 | |
2200 | |
2067 | =head3 Watcher-Specific Functions and Data Members |
2201 | =head3 Watcher-Specific Functions and Data Members |
2068 | |
2202 | |
2069 | =over 4 |
2203 | =over 4 |
2070 | |
2204 | |
… | |
… | |
3448 | 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 |
3449 | implementations for some libevent functions (such as logging, which is not |
3583 | implementations for some libevent functions (such as logging, which is not |
3450 | supported). It will also not define any of the structs usually found in |
3584 | supported). It will also not define any of the structs usually found in |
3451 | F<event.h> that are not directly supported by the libev core alone. |
3585 | F<event.h> that are not directly supported by the libev core alone. |
3452 | |
3586 | |
3453 | In stanbdalone mode, libev will still try to automatically deduce the |
3587 | In standalone mode, libev will still try to automatically deduce the |
3454 | configuration, but has to be more conservative. |
3588 | configuration, but has to be more conservative. |
3455 | |
3589 | |
3456 | =item EV_USE_MONOTONIC |
3590 | =item EV_USE_MONOTONIC |
3457 | |
3591 | |
3458 | 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 |
… | |
… | |
3676 | speed (but with the full API), define this symbol to C<1>. Currently this |
3810 | speed (but with the full API), define this symbol to C<1>. Currently this |
3677 | is used to override some inlining decisions, saves roughly 30% code size |
3811 | is used to override some inlining decisions, saves roughly 30% code size |
3678 | on amd64. It also selects a much smaller 2-heap for timer management over |
3812 | on amd64. It also selects a much smaller 2-heap for timer management over |
3679 | the default 4-heap. |
3813 | the default 4-heap. |
3680 | |
3814 | |
3681 | You can save even more by disabling watcher types you do not need and |
3815 | You can save even more by disabling watcher types you do not need |
3682 | setting C<EV_MAXPRI> == C<EV_MINPRI>. |
3816 | and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> |
|
|
3817 | (C<-DNDEBUG>) will usually reduce code size a lot. |
3683 | |
3818 | |
3684 | 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 |
3685 | 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 |
3686 | 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 |
3687 | over time. |
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. |
3688 | |
3832 | |
3689 | =item EV_PID_HASHSIZE |
3833 | =item EV_PID_HASHSIZE |
3690 | |
3834 | |
3691 | 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 |
3692 | 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 |
… | |
… | |
3878 | 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 |
3879 | watcher callback into the event loop interested in the signal. |
4023 | watcher callback into the event loop interested in the signal. |
3880 | |
4024 | |
3881 | =back |
4025 | =back |
3882 | |
4026 | |
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4027 | =head4 THREAD LOCKING EXAMPLE |
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4028 | |
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4029 | Here is a fictitious example of how to run an event loop in a different |
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4030 | thread than where callbacks are being invoked and watchers are |
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4031 | created/added/removed. |
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4032 | |
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4033 | For a real-world example, see the C<EV::Loop::Async> perl module, |
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4034 | which uses exactly this technique (which is suited for many high-level |
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4035 | languages). |
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4036 | |
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4037 | The example uses a pthread mutex to protect the loop data, a condition |
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4038 | variable to wait for callback invocations, an async watcher to notify the |
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4039 | event loop thread and an unspecified mechanism to wake up the main thread. |
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4040 | |
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4041 | First, you need to associate some data with the event loop: |
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4042 | |
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4043 | typedef struct { |
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4044 | mutex_t lock; /* global loop lock */ |
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4045 | ev_async async_w; |
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4046 | thread_t tid; |
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4047 | cond_t invoke_cv; |
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4048 | } userdata; |
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4049 | |
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4050 | void prepare_loop (EV_P) |
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4051 | { |
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4052 | // for simplicity, we use a static userdata struct. |
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4053 | static userdata u; |
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4054 | |
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4055 | ev_async_init (&u->async_w, async_cb); |
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4056 | ev_async_start (EV_A_ &u->async_w); |
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4057 | |
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4058 | pthread_mutex_init (&u->lock, 0); |
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4059 | pthread_cond_init (&u->invoke_cv, 0); |
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4060 | |
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4061 | // now associate this with the loop |
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4062 | ev_set_userdata (EV_A_ u); |
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4063 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
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4064 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
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4065 | |
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4066 | // then create the thread running ev_loop |
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4067 | pthread_create (&u->tid, 0, l_run, EV_A); |
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4068 | } |
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4069 | |
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4070 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
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4071 | solely to wake up the event loop so it takes notice of any new watchers |
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4072 | that might have been added: |
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4073 | |
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4074 | static void |
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4075 | async_cb (EV_P_ ev_async *w, int revents) |
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4076 | { |
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4077 | // just used for the side effects |
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4078 | } |
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4079 | |
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4080 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
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4081 | protecting the loop data, respectively. |
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4082 | |
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4083 | static void |
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4084 | l_release (EV_P) |
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4085 | { |
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4086 | userdata *u = ev_userdata (EV_A); |
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4087 | pthread_mutex_unlock (&u->lock); |
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4088 | } |
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4089 | |
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4090 | static void |
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4091 | l_acquire (EV_P) |
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4092 | { |
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4093 | userdata *u = ev_userdata (EV_A); |
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4094 | pthread_mutex_lock (&u->lock); |
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4095 | } |
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4096 | |
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4097 | The event loop thread first acquires the mutex, and then jumps straight |
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4098 | into C<ev_loop>: |
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4099 | |
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4100 | void * |
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4101 | l_run (void *thr_arg) |
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4102 | { |
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4103 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
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4104 | |
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4105 | l_acquire (EV_A); |
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4106 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
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4107 | ev_loop (EV_A_ 0); |
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4108 | l_release (EV_A); |
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4109 | |
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4110 | return 0; |
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4111 | } |
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4112 | |
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4113 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
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4114 | signal the main thread via some unspecified mechanism (signals? pipe |
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4115 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
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4116 | have been called (in a while loop because a) spurious wakeups are possible |
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4117 | and b) skipping inter-thread-communication when there are no pending |
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4118 | watchers is very beneficial): |
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4119 | |
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4120 | static void |
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4121 | l_invoke (EV_P) |
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4122 | { |
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4123 | userdata *u = ev_userdata (EV_A); |
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4124 | |
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4125 | while (ev_pending_count (EV_A)) |
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4126 | { |
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4127 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
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4128 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
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4129 | } |
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4130 | } |
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4131 | |
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4132 | Now, whenever the main thread gets told to invoke pending watchers, it |
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4133 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
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4134 | thread to continue: |
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4135 | |
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4136 | static void |
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4137 | real_invoke_pending (EV_P) |
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4138 | { |
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4139 | userdata *u = ev_userdata (EV_A); |
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4140 | |
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4141 | pthread_mutex_lock (&u->lock); |
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4142 | ev_invoke_pending (EV_A); |
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4143 | pthread_cond_signal (&u->invoke_cv); |
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4144 | pthread_mutex_unlock (&u->lock); |
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4145 | } |
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4146 | |
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4147 | Whenever you want to start/stop a watcher or do other modifications to an |
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4148 | event loop, you will now have to lock: |
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4149 | |
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4150 | ev_timer timeout_watcher; |
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4151 | userdata *u = ev_userdata (EV_A); |
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4152 | |
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4153 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
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4154 | |
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4155 | pthread_mutex_lock (&u->lock); |
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4156 | ev_timer_start (EV_A_ &timeout_watcher); |
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4157 | ev_async_send (EV_A_ &u->async_w); |
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4158 | pthread_mutex_unlock (&u->lock); |
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4159 | |
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4160 | Note that sending the C<ev_async> watcher is required because otherwise |
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4161 | an event loop currently blocking in the kernel will have no knowledge |
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4162 | about the newly added timer. By waking up the loop it will pick up any new |
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4163 | watchers in the next event loop iteration. |
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4164 | |
3883 | =head3 COROUTINES |
4165 | =head3 COROUTINES |
3884 | |
4166 | |
3885 | Libev is very accommodating to coroutines ("cooperative threads"): |
4167 | Libev is very accommodating to coroutines ("cooperative threads"): |
3886 | libev fully supports nesting calls to its functions from different |
4168 | libev fully supports nesting calls to its functions from different |
3887 | 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 |
3888 | different coroutines, and switch freely between both coroutines running the |
4170 | different coroutines, and switch freely between both coroutines running |
3889 | 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 |
3890 | you must not do this from C<ev_periodic> reschedule callbacks. |
4172 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3891 | |
4173 | |
3892 | 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 |
3893 | 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 |
3894 | they do not call any callbacks. |
4176 | they do not call any callbacks. |
3895 | |
4177 | |